SEMICONDUCTOR CHIP ASSEMBLY WITH POST/DIELECTRIC/POST HEAT SPREADER
A semiconductor chip assembly includes a semiconductor device, a heat spreader, a conductive trace and first and second adhesives. The heat spreader includes a first post, a second post and a dielectric base. The conductive trace includes a pad and a terminal. The semiconductor device is electrically connected to the conductive trace and thermally connected to the heat spreader. The first post extends from the dielectric base in a first vertical direction into a first opening in the first adhesive, the second post extends from the dielectric base in a second vertical direction into a second opening in the second adhesive and the dielectric base contacts and is sandwiched between and extends laterally from the posts. The conductive trace provides signal routing between the pad and the terminal.
This application is a continuation-in-part of U.S. application Ser. No. 12/616,773 filed Nov. 11, 2009 and a continuation-in-part of U.S. application Ser. No. 12/616,775 filed Nov. 11, 2009, each of which is incorporated by reference. This application also claims the benefit of U.S. Provisional Application Ser. No. 61/481,733 filed May 3, 2011, which is incorporated by reference.
U.S. application Ser. No. 12/616,773 filed Nov. 11, 2009 and U.S. application Ser. No. 12/616,775 filed Nov. 11, 2009 are each a continuation-in-part of U.S. application Ser. No. 12/557,540 filed Sep. 11, 2009 and a continuation-in-part of U.S. application Ser. No. 12/557,541 filed Sep. 11, 2009.
U.S. application Ser. No. 12/557,540 filed Sep. 11, 2009 and U.S. application Ser. No. 12/557,541 filed Sep. 11, 2009 are each a continuation-in-part of U.S. application Ser. No. 12/406,510 filed Mar. 18, 2009, which claims the benefit of U.S. Provisional Application Ser. No. 61/071,589 filed May 7, 2008, U.S. Provisional Application Ser. No. 61/071,588 filed May 7, 2008, U.S. Provisional Application Ser. No. 61/071,072 filed Apr. 11, 2008, and U.S. Provisional Application Ser. No. 61/064,748 filed Mar. 25, 2008, each of which is incorporated by reference. U.S. application Ser. No. 12/557,540 filed Sep. 11, 2009 and U.S. application Ser. No. 12/557,541 filed Sep. 11, 2009 also claim the benefit of U.S. Provisional Application Ser. No. 61/150,980 filed Feb. 9, 2009, which is incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to semiconductor chip assembly, and more particularly to a semiconductor chip assembly with a semiconductor device, a conductive trace, an adhesive and a heat spreader and its method of manufacture.
2. Description of the Related Art
Semiconductor devices such as packaged and unpackaged semiconductor chips have high voltage, high frequency and high performance applications that require substantial power to perform the specified functions. As the power increases, the semiconductor device generates more heat. Furthermore, the heat build-up is aggravated by higher packing density and smaller profile sizes which reduce the surface area to dissipate the heat.
Semiconductor devices are susceptible to performance degradation as well as short life span and immediate failure at high operating temperatures. The heat not only degrades the chip, but also imposes thermal stress on the chip and surrounding elements due to thermal expansion mismatch. As a result, the heat must be dissipated rapidly and efficiently from the chip to ensure effective and reliable operation. A high thermal conductivity path typically requires heat conduction and heat spreading to a much larger surface area than the chip or a die pad it is mounted on.
Light emitting diodes (LEDs) have recently become popular alternatives to incandescent, fluorescent and halogen light sources. LEDs provide energy efficient, cost effective, long term lighting for medical, military, signage, signal, aircraft, maritime, automotive, portable, commercial and residential applications. For instance, LEDs provide light sources for lamps, flashlights, headlights, flood lights, traffic lights and displays.
LEDs include high power chips that generate high light output and considerable heat. Unfortunately, LEDs exhibit color shifts and low light output as well as short lifetimes and immediate failure at high operating temperatures. Furthermore, LED light output and reliability are constrained by heat dissipation limits. LEDs underscore the critical need for providing high power chips with adequate heat dissipation.
LED packages usually include an LED chip, a submount, electrical contacts and a thermal contact. The submount is thermally connected to and mechanically supports the LED chip. The electrical contacts are electrically connected to the anode and cathode of the LED chip. The thermal contact is thermally connected to the LED chip by the submount but requires adequate heat dissipation by the underlying carrier to prevent the LED chip from overheating.
Packages and thermal boards for high power chips have been developed extensively in the industry with a wide variety of designs and manufacturing techniques in attempts to meet performance demands in an extremely cost-competitive environment.
Plastic ball grid array (PBGA) packages have a chip and a laminated substrate enclosed in a plastic housing and are attached to a printed circuit board (PCB) by solder balls. The laminated substrate includes a dielectric layer that often includes fiberglass. The heat from the chip flows through the plastic and the dielectric layer to the solder balls and then the PCB. However, since the plastic and the dielectric layer typically have low thermal conductivity, the PBGA provides poor heat dissipation.
Quad-Flat-No Lead (QFN) packages have the chip mounted on a copper die pad which is soldered to the PCB. The heat from the chip flows through the die pad to the PCB. However, since the lead frame type interposer has limited routing capability, the QFN package cannot accommodate high input/output (I/O) chips or passive elements.
Thermal boards provide electrical routing, thermal management and mechanical support for semiconductor devices. Thermal boards usually include a substrate for signal routing, a heat spreader or heat sink for heat removal, pads for electrical connection to the semiconductor device and terminals for electrical connection to the next level assembly. The substrate can be a laminated structure with single layer or multi-layer routing circuitry and one or more dielectric layers. The heat spreader can be a metal base, a metal slug or an embedded metal layer.
Thermal boards interface with the next level assembly. For instance, the next level assembly can be a light fixture with a printed circuit board and a heat sink. In this instance, an LED package is mounted on the thermal board, the thermal board is mounted on the heat sink, the thermal board/heat sink subassembly and the printed circuit board are mounted in the light fixture and the thermal board is electrically connected to the printed circuit board by wires. The substrate routes electrical signals to the LED package from the printed circuit board and the heat spreader spreads and transfers heat from the LED package to the heat sink. The thermal board thus provides a critical thermal path for the LED chip.
U.S. Pat. No. 6,507,102 to Juskey et al. discloses an assembly in which a composite substrate with fiberglass and cured thermosetting resin includes a central opening, a heat slug with a square or rectangular shape resembling the central opening is attached to the substrate at sidewalls of the central opening, top and bottom conductive layers are attached to the top and bottom of the substrate and electrically connected to one another by plated through-holes through the substrate, a chip is mounted on the heat slug and wire bonded to the top conductive layer, an encapsulant is molded on the chip and solder balls are placed on the bottom conductive layer.
During manufacture, the substrate is initially a prepreg with B-stage resin placed on the bottom conductive layer, the heat slug is inserted into the central opening and on the bottom conductive layer and spaced from the substrate by a gap, the top conductive layer is mounted on the substrate, the conductive layers are heated and pressed towards one another so that the resin melts, flows into the gap and solidifies, the conductive layers are patterned to form circuit traces on the substrate and expose the excess resin flash on the heat slug, and the excess resin flash is removed to expose the heat slug. The chip is then mounted on the heat slug, wire bonded and encapsulated.
The heat flows from the chip through the heat slug to the PCB. However, manually dropping the heat slug into the central opening is prohibitively cumbersome and expensive for high volume manufacture. Furthermore, since the heat slug is difficult to accurately position in the central opening due to tight lateral placement tolerance, voids and inconsistent bond lines arise between the substrate and the heat slug. The substrate is therefore partially attached to the heat slug, fragile due to inadequate support by the heat slug and prone to delamination. In addition, the wet chemical etch that removes portions of the conductive layers to expose the excess resin flash also removes portions of the heat slug exposed by the excess resin flash. The heat slug is therefore non-planar and difficult to bond to. As a result, the assembly suffers from high yield loss, poor reliability and excessive cost.
U.S. Pat. No. 6,528,882 to Ding et al. discloses a thermal enhanced ball grid array package in which the substrate includes a metal core layer. The chip is mounted on a die pad region at the top surface of the metal core layer, an insulating layer is formed on the bottom surface of the metal core layer, blind vias extend through the insulating layer to the metal core layer, thermal balls fill the blind vias and solder balls are placed on the substrate and aligned with the thermal balls. The heat from the chip flows through the metal core layer to the thermal balls to the PCB. However, the insulating layer sandwiched between the metal core layer and the PCB limits the heat flow to the PCB.
U.S. Pat. No. 6,670,219 to Lee et al. discloses a cavity down ball grid array (CDBGA) package in which a ground plate with a central opening is mounted on a heat spreader to form a thermal dissipating substrate. A substrate with a central opening is mounted on the ground plate using an adhesive with a central opening. A chip is mounted on the heat spreader in a cavity defined by the central opening in the ground plate and solder balls are placed on the substrate. However, since the solder balls extend above the substrate, the heat spreader does not contact the PCB. As a result, the heat spreader releases the heat by thermal convection rather than thermal conduction which severely limits the heat dissipation.
U.S. Pat. No. 7,038,311 to Woodall et al. discloses a thermal enhanced BGA package in which a heat sink with an inverted T-like shape includes a pedestal and an expanded base, a substrate with a window opening is mounted on the expanded base, an adhesive attaches the pedestal and the expanded base to the substrate, a chip is mounted on the pedestal and wire bonded to the substrate, an encapsulant is molded on the chip and solder balls are placed on the substrate. The pedestal extends through the window opening, the substrate is supported by the expanded base and the solder balls are located between the expanded base and the perimeter of the substrate. The heat from the chip flows through the pedestal to the expanded base to the PCB. However, since the expanded base must leave room for the solder balls, the expanded base protrudes below the substrate only between the central window and the innermost solder ball. Consequently, the substrate is unbalanced and wobbles and warps during manufacture. This creates enormous difficulties with chip mounting, wire bonding and encapsulant molding. Furthermore, the expanded base may be bent by the encapsulant molding and may impede soldering the package to the next level assembly as the solder balls collapse. As a result, the package suffers from high yield loss, poor reliability and excessive cost.
U.S. Patent Application Publication No. 2007/0267642 to Erchak et al. discloses a light emitting device assembly in which a base with an inverted T-like shape includes a substrate, a protrusion and an insulative layer with an aperture, electrical contacts are mounted on the insulative layer, a package with an aperture and a transparent lid is mounted on the electrical contacts and an LED chip is mounted on the protrusion and wire bonded to the substrate. The protrusion is adjacent to the substrate and extends through the apertures in the insulative layer and the package into the package, the insulative layer is mounted on the substrate, the electrical contacts are mounted on the insulative layer and the package is mounted on the electrical contacts and spaced from the insulative layer. The heat from the chip flows through the protrusion to the substrate to a heat sink. However, the electrical contacts are difficult to mount on the insulating layer, difficult to electrically connect to the next level assembly and fail to provide multi-layer routing.
Conventional packages and thermal boards thus have major deficiencies. For instance, dielectrics with low thermal conductivity such as epoxy limit heat dissipation, whereas dielectrics with higher thermal conductivity such as epoxy filled with ceramic or silicon carbide have low adhesion and are prohibitively expensive for high volume manufacture. The dielectric may delaminate during manufacture or prematurely during operation due to the heat. The substrate may have single layer circuitry with limited routing capability or multi-layer circuitry with thick dielectric layers which reduce heat dissipation. The heat spreader may be inefficient, cumbersome or difficult to thermally connect to the next level assembly. The manufacturing process may be unsuitable for low cost, high volume manufacture.
In view of the various development stages and limitations in currently available packages and thermal boards for high power semiconductor devices, there is a need for a semiconductor chip assembly that is cost effective, reliable, manufacturable, versatile, provides flexible signal routing and has excellent heat spreading and dissipation.
SUMMARY OF THE INVENTIONThe present invention provides a semiconductor chip assembly that includes a semiconductor device, a heat spreader, a conductive trace and first and second adhesives. The heat spreader includes a first post, a second post and a dielectric base. The conductive trace includes a pad and a terminal. The semiconductor device is electrically connected to the conductive trace and thermally connected to the heat spreader. The first post extends from the dielectric base in a first vertical direction into a first opening in the first adhesive, the second post extends from the dielectric base in a second vertical direction into a second opening in the second adhesive and the dielectric base contacts and is sandwiched between and extends laterally from the posts. The conductive trace provides signal routing between the pad and the terminal.
In accordance with an aspect of the present invention, a semiconductor chip assembly includes a semiconductor device, a heat spreader, a conductive trace and first and second adhesives. The first adhesive includes a first opening. The second adhesive includes a second opening. The heat spreader includes a first post, a second post and a dielectric base, wherein (i) the first post extends vertically from the dielectric base in a first vertical direction, (ii) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction and (iii) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts in lateral directions orthogonal to the vertical directions. The conductive trace includes a pad, a terminal and an electrical interconnect in an electrically conductive path between the pad and the terminal.
The semiconductor device is mounted on the first post, extends vertically beyond the dielectric base in the first vertical direction, extends laterally within peripheries of the posts, is electrically connected to the pad and thereby electrically connected to the terminal, is thermally connected to the first post and thereby thermally connected to the second post and is electrically isolated from the second post. The first adhesive extends vertically beyond the dielectric base in the first vertical direction, extends laterally from the first post to or beyond the terminal and is sandwiched between the dielectric base and the pad. The second adhesive extends vertically beyond the dielectric base in the second vertical direction, extends laterally from the second post to or beyond the terminal and is sandwiched between the dielectric base and the terminal. The pad extends vertically beyond the dielectric base in the first vertical direction, the terminal extends vertically beyond the dielectric base in the second vertical direction and the electrical interconnect extends through the dielectric base and the adhesives. The first post extends into the first opening, the second post extends into the second opening and the dielectric base contacts and is sandwiched between the adhesives and covers the semiconductor device in the second vertical direction.
In accordance with another aspect of the present invention, a semiconductor chip assembly includes a semiconductor device, a heat spreader, a conductive trace and first and second adhesives. The first adhesive includes a first opening. The second adhesive includes a second opening. The heat spreader includes a first post, a second post, a first cap, a second cap and a dielectric base, wherein (i) the first post extends vertically from the dielectric base in a first vertical direction, (ii) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, (iii) the first cap is adjacent to the first post, covers the first post in the first vertical direction and extends laterally from the first post, (iv) the second cap is adjacent to the second post, covers the second post in the second vertical direction and extends laterally from the second post and (v) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts and laterally beyond the caps in lateral directions orthogonal to the vertical directions. The conductive trace includes a pad, a terminal and an electrical interconnect, wherein the electrical interconnect includes a plated through-hole in an electrically conductive path between the pad and the terminal.
The semiconductor device is mounted on the first cap, extends vertically beyond the first cap and the first adhesive in the first vertical direction, extends laterally within peripheries of the posts, is located within peripheries of the caps, is electrically connected to the pad and thereby electrically connected to the terminal, is thermally connected to the first cap and thereby thermally connected to the second cap and is electrically isolated from the second cap. The first adhesive contacts the first post, the first cap and the dielectric base, is spaced from the second post and the second cap, extends vertically beyond the dielectric base in the first vertical direction, extends laterally from the first post to or beyond the terminal and is sandwiched between the dielectric base and the pad. The second adhesive contacts the second post, the second cap and the dielectric base, is spaced from the first post and the first cap, extends vertically beyond the dielectric base in the second vertical direction, extends laterally from the second post to or beyond the terminal and is sandwiched between the dielectric base and the terminal. The pad extends vertically beyond the first adhesive in the first vertical direction, the terminal extends vertically beyond the second adhesive in the second vertical direction and the plated through-hole extends through the dielectric base and the adhesives. The first post extends into the first opening, the second post extends into the second opening, the first cap extends vertically beyond the first adhesive in the first vertical direction, the second cap extends vertically beyond the second adhesive in the second vertical direction and the dielectric base is sandwiched between the adhesives and covers the semiconductor device in the second vertical direction. Furthermore, the posts and the caps are metallic the dielectric base and the adhesives are non-metallic and extend to peripheral edges of the assembly, the caps are electrically isolated from one another and the second cap has no electrical function.
In accordance with another aspect of the present invention, a semiconductor chip assembly includes a semiconductor device, a heat spreader, first and second adhesives and first and second conductive traces. The first adhesive includes a first opening. The second adhesive includes a second opening. The heat spreader includes a first post, a second post, a first cap, a second cap and a dielectric base, wherein (i) the first post extends vertically from the dielectric base in a first vertical direction, (ii) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, (iii) the first cap is adjacent to the first post, covers the first post in the first vertical direction and extends laterally from the first post, (iv) the second cap is adjacent to the second post, covers the second post in the second vertical direction and extends laterally from the second post and (v) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts and laterally beyond the caps in lateral directions orthogonal to the vertical directions. The first conductive trace includes a pad, a first terminal and a first electrical interconnect, wherein the first electrical interconnect includes a first plated through-hole in an electrically conductive path between the pad and the first terminal. The second conductive trace includes the first cap, a second terminal and a second electrical interconnect, wherein the second electrical interconnect includes a second plated through-hole in an electrically conductive path between the first cap and the second terminal.
The semiconductor device is mounted on the first cap, extends vertically beyond the first cap and the first adhesive in the first vertical direction, extends laterally within peripheries of the posts, is located within peripheries of the caps, is electrically connected to the pad and thereby electrically connected to the first terminal, is electrically connected to the first cap and thereby electrically connected to the second terminal, is thermally connected to the first cap and thereby thermally connected to the second cap and is electrically isolated from the second post and the second cap. The first adhesive contacts the first post, the first cap and the dielectric base, is spaced from the second post and the second cap, extends vertically beyond the dielectric base in the first vertical direction, extends laterally from the first post to or beyond the terminals and is sandwiched between the dielectric base and the pad. The second adhesive contacts the second post, the second cap and the dielectric base, is spaced from the first post and the first cap, extends vertically beyond the dielectric base in the second vertical direction, extends laterally from the second post to or beyond the terminals and is sandwiched between the dielectric base and the terminals. The pad extends vertically beyond the first adhesive in the first vertical direction, the terminals extend vertically beyond the second adhesive in the second vertical direction and the plated through-holes extend through the dielectric base and the adhesives. The first post extends into the first opening, the second post extends into the second opening, the first cap extends vertically beyond the first adhesive in the first vertical direction, the second cap extends vertically beyond the second adhesive in the second vertical direction and the dielectric base is sandwiched between the adhesives and covers the semiconductor device in the second vertical direction. Furthermore, the posts and the caps are metallic and spaced from peripheral edges of the assembly, the dielectric base and the adhesives are non-metallic and extend to peripheral edges of the assembly, the posts are electrically isolated from one another, the caps are electrically isolated from one another, the terminals are electrically isolated from one another and the second cap has no electrical function and electrically floats during operation of the semiconductor device.
The first cap can have a rectangular or square shape and the first post can have a circular shape. In this instance, the first cap can be sized and shaped to accommodate a thermal contact surface of the semiconductor device whereas the first post need not be sized and shaped to accommodate the thermal contact surface of the semiconductor device Likewise, the second cap can have a rectangular or square shape and the second post can have a circular shape. In this instance, the second cap can be sized and shaped to accommodate a thermal contact surface of a heat sink whereas the second post need not be sized and shaped to accommodate the thermal contact surface of the heat sink. In any case, the caps are thermally connected to one another by the posts and the dielectric base.
The heat spreader can consist of the posts, the caps and the dielectric base or include the posts, the caps, the dielectric base, the second plated through-hole and the second terminal. The heat spreader can also consist essentially of (i) copper, aluminum or copper/nickel/aluminum and (ii) the dielectric base. The heat spreader can also include a first buried copper, aluminum or copper/nickel/aluminum core shared by the first post, the first cap, the second plated through-hole and the second terminal, a second buried copper core shared by the second post and the second cap and plated surface contacts that consist of gold, silver and/or nickel at the caps and the second terminal. In any case, the heat spreader provides heat dissipation and spreading from the semiconductor device to the next level assembly.
The semiconductor device can be a packaged or unpackaged semiconductor chip. For instance, the semiconductor device can be a non-vertical LED chip that is mounted on the first cap but not the pad, extends beyond the pad and the first cap in the first vertical direction, is electrically connected to the pad using a wire bond and is thermally connected to the first cap using a die attach. In this instance, the LED chip can be electrically connected to a second pad using a second wire bond, thereby electrically connecting the LED chip to a second terminal, and the heat spreader can have a thermal function but not an electrical function. Alternatively, the semiconductor device can be a vertical LED chip that is mounted on the first cap but not the pad, extends beyond the pad and the first cap in the first vertical direction, is electrically connected to the pad using a wire bond and is electrically and thermally connected to the first cap using a die attach. In this instance, the LED chip can be electrically connected to second terminal using the first cap and the heat spreader can have a thermal/electrical function. In any case, the semiconductor device is thermally connected to and electrically isolated from the second cap.
The first adhesive can contact the first post, the first cap, the dielectric base and the electrical interconnect and be spaced from the second post, the second adhesive and the terminal. The first adhesive can also be sandwiched between the first post and the pad, between the dielectric base and the pad and between the dielectric base and the first cap. The first adhesive can also contact or be spaced from the pad. The first adhesive can also cover and surround the first post in the lateral directions, cover the dielectric base outside the first post in the first vertical direction and cover the first cap outside the first post in the second vertical direction. The first adhesive can also conformally coat the sidewalls of the first post.
The first adhesive can extend laterally from the first post to or beyond the terminal. For instance, the first adhesive and the terminal can extend to peripheral edges of the assembly. In this instance, the first adhesive extends laterally from the first post to the terminal. Alternatively, the first adhesive can extend to peripheral edges of the assembly and the terminal can be spaced from the peripheral edges of the assembly. In this instance, the first adhesive extends laterally from the first post beyond the terminal.
The first adhesive alone can intersect an imaginary horizontal line between the first post and the electrical interconnect, an imaginary horizontal line between the first post and a peripheral edge of the assembly and an imaginary vertical line between the first cap and the dielectric base.
The second adhesive can contact the second post, the second cap, the dielectric base and the electrical interconnect and be spaced from the first post, the first adhesive, and the pad. The second adhesive can also be sandwiched between the second post and the terminal, between the dielectric base and the terminal and between the dielectric base and the second cap. The second adhesive can also contact or be spaced from the terminal. The second adhesive can also cover and surround the second post in the lateral directions, cover the dielectric base outside the second post in the second vertical direction and cover the second cap outside the second post in the first vertical direction. The second adhesive can also conformally coat the sidewalls of the second post.
The second adhesive can extend laterally from the second post to or beyond the terminal. For instance, the second adhesive and the terminal can extend to peripheral edges of the assembly. In this instance, the second adhesive extends laterally from the second post to the terminal. Alternatively, the second adhesive can extend to peripheral edges of the assembly and the terminal can be spaced from the peripheral edges of the assembly. In this instance, the second adhesive extends laterally from the second post beyond the terminal.
The second adhesive alone can intersect an imaginary horizontal line between the second post and the electrical interconnect, an imaginary horizontal line between the second post and a peripheral edge of the assembly and an imaginary vertical line between the second cap and the dielectric base.
The adhesives can be the same material and can be spaced from one another.
The first post can be coplanar with the first adhesive at the first cap and at the dielectric base and second post can also be coplanar with the second adhesive at the second cap and at the dielectric base. The first adhesive can also be coplanar with the first post between opposing lateral surfaces of the pad and the second adhesive can also be coplanar with the second post between opposing lateral surfaces of the terminal. The first post can also have a cut-off conical or pyramidal shape in which its diameter decreases as it extends in the first vertical direction from the dielectric base to the first cap and the second post can also have a cut-off conical or pyramidal shape in which its diameter decreases as it extends in the second vertical direction from the dielectric base to the second cap. The first post can also have tapered sidewalls characteristic of wet chemical etching and the second post can also have tapered sidewalls characteristic of wet chemical etching.
The dielectric base can cover the first post and the first adhesive in the second vertical direction, cover the second post and the second adhesive in the first vertical direction, support the posts and the adhesives and extend to peripheral edges of the assembly. The dielectric base can also be various thermally conductive, electrically insulative organic or inorganic materials such as epoxy, polyimide and diamond-like carbon (DLC). The dielectric base can also be primarily plastic such as epoxy or polyimide and include a reinforcement such as E-glass to increase strength and a filler such as aluminum oxide or aluminum nitride to increase thermal conductivity. In any case, the dielectric base thermally connects and electrically isolates the posts.
The posts can be mirror images of one another. In this instance, the posts can be axially aligned with one another. Alternatively, the first post can have a surface area that is less than one-half of a surface area of the second post. In this instance, the first post, the first cap and the pad can be located within the periphery of the second post, the terminal can be located outside the periphery of the second post, the first adhesive can extend within and outside the periphery of the second post and the posts can be axially aligned with one another. In another instance, the pad can be located within the periphery of the second post, the terminal can be located outside the periphery of the second post, first post, the first cap and the first adhesive can extend within and outside the periphery of the second post and the posts can be laterally offset from one another.
The pad can contact or be spaced from the first adhesive and the terminal can contact or be spaced from the second adhesive. For instance, the pad can contact the first adhesive and the terminal can contact the second adhesive. In this instance, the first adhesive contacts and is sandwiched between the pad the dielectric base and the second adhesive contacts and is sandwiched between the terminal and the dielectric base. Alternatively, the assembly can include first and second dielectric layers, wherein the pad is spaced from the first adhesive and the terminal is spaced from the second adhesive. In this instance, the first dielectric layer contacts and is sandwiched between the pad and the first adhesive, contacts the first cap and is spaced from the first post and the dielectric base, the second dielectric layer contacts and is sandwiched between the terminal and the second adhesive, contacts the second cap and is spaced from the second post and the dielectric base, the first post extends through a first aperture in the first dielectric layer, the second post extends through a second aperture in the second dielectric layer and the plated through-hole extends through the dielectric layers. Furthermore, a first substrate can include the pad and the first dielectric layer and be a laminated structure that is spaced from the first post and the dielectric base and a second substrate can include the terminal and the second dielectric layer and be a laminated structure that is spaced from the second post and the dielectric base.
The pad and the first cap can have the same thickness where closest to one another, have different thickness where the first cap is adjacent to the first post and be coplanar with one another at a first surface that faces in the first vertical direction.
The terminal and the second cap can have the same thickness where closest to one another, have different thickness where the second cap is adjacent to the second post and be coplanar with one another at a second surface that faces in the second vertical direction.
The conductive trace can include a routing line that extends beyond the first adhesive in the first vertical direction and extends laterally in an electrically conductive path between the pad and the electrical interconnect Likewise, the conductive trace can include a routing line that extends beyond the second adhesive in the second vertical direction and extends laterally in an electrically conductive path between the terminal and the electrical interconnect. Furthermore, the electrical interconnect can be a plated through-hole that extends through the dielectric base and the adhesives.
The conductive trace can consist of the pad, the routing line, the terminal and the plated through-hole. The conductive trace can also consist essentially of copper. The conductive trace can also include a buried copper core and plated surface contacts that consist of gold, silver and/or nickel at the pad and the terminal. In any case, the conductive trace provides signal routing between the pad and the terminal.
The pad can be an electrical contact for the semiconductor device, the terminal can be an electrical contact for the next level assembly, and the pad and the terminal can provide signal routing between the semiconductor device and the next level assembly.
The first cap can be a thermal contact for the semiconductor device, the second cap be a thermal contact for the next level assembly, and the caps can provide thermal routing between the semiconductor device and the next level assembly.
The pad, the terminal and the caps can be the same metals and the posts can be the same metal. For instance, the pad, the terminal and the caps can include a gold, silver or nickel surface layer and a buried copper core and be primarily copper, the posts can be copper and the electrical interconnect can include copper. In this instance, a plated contact can include a gold or silver surface layer and a buried nickel layer that contacts and is sandwiched between the surface layer and the buried copper core or a nickel surface layer that contacts the buried copper core.
The heat spreader can include a first copper core shared by the first post and the first cap and a second copper core shared by the second post and the second cap and the conductive trace can include a copper core shared by the pad, the terminal and the electrical interconnect. For instance, the heat spreader can include a gold, silver or nickel surface layer at the caps, a first buried copper core at the first post and the first cap and a second buried copper core at the second post and the second cap and be primarily copper outside the dielectric base. In this instance, the first cap can include a plated contact as its surface layer and the second cap can include a plated contact as its surface layer Likewise, the conductive trace can include a gold, silver or nickel surface layer at the pad and the terminal, a buried copper core at the pad, the terminal and the electrical interconnect and be primarily copper. In this instance, the pad can include a plated contact as its surface layer and the terminal can include a plated contact as its surface layer.
The assembly can be a first-level or second-level single-chip or multi-chip device. For instance, the assembly can be a first-level package that contains a single chip or multiple chips. Alternatively, the assembly can be a second-level module that contains a single LED package or multiple LED packages, and each LED package can contain a single LED chip or multiple LED chips.
The present invention provides a method of making a semiconductor chip assembly that includes providing first and second posts, first and second adhesives, first and second conductive layers and a dielectric base, wherein the first post extends from the dielectric base in a first vertical direction into a first opening in the first adhesive and is aligned with a first aperture in the first conductive layer, the second post extends from the dielectric base in a second vertical direction into a second opening in the second adhesive and is aligned with a second aperture in the second conductive layer and the dielectric base is sandwiched between and extends laterally from the posts, then flowing the first adhesive in the first vertical direction and the second adhesive in the second vertical direction, solidifying the adhesives, then providing a conductive trace that includes a pad, a terminal and selected portions of the conductive layers, wherein the pad extends beyond the dielectric base in the first vertical direction and the terminal extends beyond the dielectric base in the second vertical direction, providing a heat spreader that includes the posts and the dielectric base, then mounting a semiconductor device on the first post, electrically connecting the semiconductor device to the conductive trace and thermally connecting the semiconductor device to the heat spreader.
In accordance with an aspect of the present invention, a method of making a semiconductor chip assembly includes (1) providing a first post, a second post, a first adhesive, a second adhesive, a first conductive layer, a second conductive layer and a dielectric base, wherein (a) the first post extends vertically from the dielectric base in a first vertical direction, extends into a first opening in the first adhesive and is aligned with a first aperture in the first conductive layer, (b) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, extends into a second opening in the second adhesive and is aligned with a second aperture in the second conductive layer, (c) the first adhesive contacts the dielectric base, is sandwiched between the dielectric base and the first conductive layer, extends vertically beyond the dielectric base in the first vertical direction and is non-solidified, (d) the second adhesive contacts the dielectric base, is sandwiched between the dielectric base and the second conductive layer, extends vertically beyond the dielectric base in the second vertical direction and is non-solidified, (e) the first conductive layer extends vertically beyond the first adhesive in the first vertical direction, (f) the second conductive layer extends vertically beyond the second adhesive in the second vertical direction, and (g) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates and mechanically attaches the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts in lateral directions orthogonal to the vertical directions, then (2) flowing the first adhesive in the first vertical direction into a first gap located in the first aperture between the first post and the first conductive layer, (3) flowing the second adhesive in the second vertical direction into a second gap located in the second aperture between the second post and the second conductive layer, (4) solidifying the adhesives, thereby mechanically attaching the first conductive layer to the first post and the dielectric base using the first adhesive and mechanically attaching the second conductive layer to the second post and the dielectric base using the second adhesive, then (5) providing a conductive trace that includes a pad, a terminal and an electrical interconnect, wherein the pad extends vertically beyond the dielectric base in the first vertical direction and includes a selected portion of the first conductive layer, the terminal extends vertically beyond the dielectric base in the second vertical direction and includes a selected portion of the second conductive layer and the electrical interconnect extends through the dielectric base and the adhesives in an electrically conductive path between the pad and the terminal, (6) providing a heat spreader that includes the posts and the dielectric base, then (7) mounting a semiconductor device on the first post, wherein the semiconductor device extends vertically beyond the first post in the first vertical direction and extends laterally within peripheries of the posts and the posts are electrically isolated from one another, (8) electrically connecting the semiconductor device to the pad, thereby electrically connecting the semiconductor device to the terminal, and (9) thermally connecting the semiconductor device to the first post, thereby thermally connecting the semiconductor device to the second post.
In accordance with another aspect of the present invention, a method of making a semiconductor chip assembly includes (1) providing a first post, a second post, a first adhesive, a second adhesive, a first conductive layer, a second conductive layer and a dielectric base, wherein (a) the first post extends vertically from the dielectric base in a first vertical direction, extends into a first opening in the first adhesive and is aligned with a first aperture in the first conductive layer, (b) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, extends into a second opening in the second adhesive and is aligned with a second aperture in the second conductive layer, (c) the first adhesive contacts the dielectric base, is sandwiched between the dielectric base and the first conductive layer, extends vertically beyond the dielectric base in the first vertical direction and is non-solidified, (d) the second adhesive contacts the dielectric base, is sandwiched between the dielectric base and the second conductive layer, extends vertically beyond the dielectric base in the second vertical direction and is non-solidified, (e) the first conductive layer extends vertically beyond the first adhesive in the first vertical direction, (f) the second conductive layer extends vertically beyond the second adhesive in the second vertical direction, and (g) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates and mechanically attaches the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts in lateral directions orthogonal to the vertical directions, then (2) applying heat to melt the adhesives, (3) moving the conductive layers towards one another, thereby moving the first post in the first vertical direction in the first aperture, moving the second post in the second vertical direction in the second aperture, applying pressure to the molten first adhesive between the dielectric base and the first conductive layer and applying pressure to the molten second adhesive between the dielectric base and the second conductive layer, wherein the pressure between the dielectric base and the first conductive layer forces the molten first adhesive to flow in the first vertical direction into a first gap located in the first aperture between the first post and the first conductive layer and the pressure between the dielectric base and the second conductive layer forces the molten second adhesive to flow in the second vertical direction into a second gap located in the second aperture between the second post and the second conductive layer, (4) applying heat to solidify the molten adhesives, thereby mechanically attaching the first conductive layer to the first post and the dielectric base using the first adhesive and mechanically attaching the second conductive layer to the second post and the dielectric base using the second adhesive, then (5) providing a conductive trace that includes a pad, a terminal and an electrical interconnect, wherein the pad extends vertically beyond the first adhesive in the first vertical direction and includes a selected portion of the first conductive layer, the terminal extends vertically beyond the second adhesive in the second vertical direction and includes a selected portion of the second conductive layer and the electrical interconnect extends through the dielectric base and the adhesives in an electrically conductive path between the pad and the terminal, (6) providing a heat spreader that includes the posts, the dielectric base, a first cap and a second cap, wherein the first cap is adjacent to the first post and the first adhesive, covers the first post in the first vertical direction, extends laterally from the first post, extends vertically beyond the first adhesive in the first vertical direction and includes a selected portion of the first conductive layer and the second cap is adjacent to the second post and the second adhesive, covers the second post in the second vertical direction, extends laterally from the second post, extends vertically beyond the second adhesive in the second vertical direction and includes a selected portion of the second conductive layer, then (7) mounting a semiconductor device on the first cap, wherein the semiconductor device extends vertically beyond the first cap in the first vertical direction and extends laterally within peripheries of the posts and the caps, the first post is sandwiched between the first cap and the dielectric base, the second post is sandwiched between the second cap and the dielectric base, the posts are electrically isolated from one another and the caps are electrically isolated from one another, (8) electrically connecting the semiconductor device to the pad, thereby electrically connecting the semiconductor device to the terminal, and (9) thermally connecting the semiconductor device to the first cap, thereby thermally connecting the semiconductor device to the second cap.
In accordance with another aspect of the present invention, a method of making a semiconductor chip assembly includes (1) providing a first post, a second post, a first adhesive, a second adhesive, a first conductive layer, a second conductive layer and a dielectric base, wherein (a) the first post extends vertically from the dielectric base in a first vertical direction, extends into a first opening in the first adhesive and is aligned with a first aperture in the first conductive layer, (b) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, extends into a second opening in the second adhesive and is aligned with a second aperture in the second conductive layer, (c) the first adhesive contacts the dielectric base, is sandwiched between the dielectric base and the first conductive layer, extends vertically beyond the dielectric base in the first vertical direction and is non-solidified, (d) the second adhesive contacts the dielectric base, is sandwiched between the dielectric base and the second conductive layer, extends vertically beyond the dielectric base in the second vertical direction and is non-solidified, (e) the first conductive layer extends vertically beyond the first adhesive in the first vertical direction, (f) the second conductive layer extends vertically beyond the second adhesive in the second vertical direction, and (g) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates and mechanically attaches the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts in lateral directions orthogonal to the vertical directions, then (2) applying heat to melt the adhesives, (3) moving the conductive layers towards one another, thereby moving the first post in the first vertical direction in the first aperture, moving the second post in the second vertical direction in the second aperture, applying pressure to the molten first adhesive between the dielectric base and the first conductive layer and applying pressure to the molten second adhesive between the dielectric base and the second conductive layer, wherein the pressure between the dielectric base and the first conductive layer forces the molten first adhesive to flow in the first vertical direction into a first gap located in the first aperture between the first post and the first conductive layer and the pressure between the dielectric base and the second conductive layer forces the molten second adhesive to flow in the second vertical direction into a second gap located in the second aperture between the second post and the second conductive layer, (4) applying heat to solidify the molten adhesives, thereby mechanically attaching the first conductive layer to the first post and the dielectric base using the first adhesive and mechanically attaching the second conductive layer to the second post and the dielectric base using the second adhesive, then (5) providing first and second plated through-holes that extend through the dielectric base, the adhesives and the conductive layers, then (6) providing a conductive trace that includes a pad, a first terminal and the first plated through-hole, wherein the pad extends vertically beyond the first adhesive in the first vertical direction and includes a selected portion of the first conductive layer, the first terminal extends vertically beyond the second adhesive in the second vertical direction and includes a selected portion of the second conductive layer and the first plated through-hole is in an electrically conductive path between the pad and the first terminal, (7) providing a heat spreader that includes the posts, the dielectric base, a first cap and a second cap, wherein the first cap is adjacent to the first post and the first adhesive, covers the first post in the first vertical direction, extends laterally from the first post, extends vertically beyond the first adhesive in the first vertical direction and includes a selected portion of the first conductive layer, the second cap is adjacent to the second post and the second adhesive, covers the second post in the second vertical direction, extends laterally from the second post, extends vertically beyond the second adhesive in the second vertical direction and includes a selected portion of the second conductive layer and the second plated through-hole is in an electrically conductive path between the first cap and a second terminal, (8) providing the pad and the first cap including removing selected portions of the first conductive layer, (9) providing the terminals and the second cap including removing selected portions of the second conductive layer, then (10) mounting a semiconductor device on the first cap, wherein the semiconductor device extends vertically beyond the first cap in the first vertical direction and extends laterally within peripheries of the posts and the caps, the first post is sandwiched between the first cap and the dielectric base, the second post is sandwiched between the second cap and the dielectric base, the posts are electrically isolated from one another, the caps are electrically isolated from one another and the terminals are electrically isolated from one another, (11) electrically connecting the semiconductor device to the pad, thereby electrically connecting the semiconductor device to the first terminal, (12) electrically connecting the semiconductor device to the first cap, thereby electrically connecting the semiconductor device to the second terminal, and (13) thermally connecting the semiconductor device to the first cap, thereby thermally connecting the semiconductor device to the second cap.
Providing the posts can include attaching first and second metal plates to one another and then etching the metal plates.
Attaching the metal plates can include laminating the first metal plate to the second metal plate using the dielectric base or depositing the dielectric base on the first metal plate and then depositing the second metal plate on the dielectric base. For instance, uncured epoxy or polyimide filled with aluminum oxide or aluminum nitride can be sandwiched between the metal plates and then cured, thereby laminating the metal plates to one another. Alternatively, DLC can be deposited on the first metal plate by vacuum coating or spray coating and then the second metal plate can be deposited on the DLC by sputtering or electroless plating and then electroplating.
Providing the post and the dielectric base can include providing the metal plates, wherein the dielectric base contacts and is sandwiched between the metal plates, then forming a first etch mask on the first metal plate that selectively exposes the first metal plate in the first vertical direction and defines the first post, forming a second etch mask on the second metal plate that selectively exposes the second metal plate in the second vertical direction and defines the second post, then etching the first metal plate in a first pattern defined by the first etch mask, thereby etching through the first metal plate to the dielectric base, wherein the first post includes an unetched portion of the first metal plate that protrudes beyond the dielectric base in the first vertical direction, etching the second metal plate a second pattern defined by the second etch mask, thereby etching through the second metal plate to the dielectric base, wherein the second post includes an unetched portion of the second metal plate that protrudes beyond the dielectric base in the second vertical direction, and then removing the etch masks
Providing the first adhesive can include providing a first prepreg with a first uncured epoxy and then inserting the first post into the first opening, flowing the first adhesive can include melting the first uncured epoxy and compressing the first uncured epoxy between the first conductive layer and the dielectric base and solidifying the first adhesive can include curing the molten first uncured epoxy. Likewise, providing the second adhesive can include providing a second prepreg with a second uncured epoxy and then inserting the second post into the second opening, flowing the second adhesive can include melting the second uncured epoxy and compressing the second uncured epoxy between the second conductive layer and the dielectric base and solidifying the second adhesive can include curing the molten second uncured epoxy.
Flowing the first adhesive can include filling the first gap with the first adhesive and squeezing the first adhesive through the first gap, beyond the first post and the first conductive layer in the first vertical direction and on surface portions of the first post and the first conductive layer adjacent to the first gap that face in the first vertical direction. Likewise, flowing the second adhesive can include filling the second gap with the second adhesive and squeezing the second adhesive through the second gap, beyond the second post and the second conductive layer in the second vertical direction and on surface portions of the second post and the second conductive layer adjacent to the second gap that face in the second vertical direction.
Solidifying the first adhesive can include mechanically bonding the first post and the dielectric base to the first conductive layer Likewise, solidifying the second adhesive can include mechanically bonding the second post and the dielectric base to the second conductive layer.
Providing the first conductive layer can include contacting the first conductive layer and the first adhesive, wherein the first aperture extends through the first conductive layer alone, and then flowing the first adhesive into the first gap. Likewise, providing the second conductive layer can include contacting the second conductive layer and the second adhesive, wherein the second aperture extends through the second conductive layer alone, and then flowing the second adhesive into the second gap. In this manner, the first adhesive laminates the first conductive layer alone to the first post and the dielectric base and the second adhesive laminates the second conductive layer alone to the second post and the dielectric base.
Providing the first conductive layer can include providing a first substrate that includes the first conductive layer and a first dielectric layer and then contacting the first dielectric layer and the first adhesive, wherein the first dielectric layer contacts and is sandwiched between the first conductive layer and the first adhesive and is solidified and the first aperture extends through the first conductive layer and the first dielectric layer, and then flowing the first adhesive into the first gap Likewise, providing the second conductive layer can include providing a second substrate that includes the second conductive layer and a second dielectric layer and then contacting the second dielectric layer and the second adhesive, wherein the second dielectric layer contacts and is sandwiched between the second conductive layer and the second adhesive and is solidified and the second aperture extends through the second conductive layer and the second dielectric layer, and then flowing the second adhesive into the second gap. In this manner, the first adhesive laminates the first conductive layer and the first dielectric layer to the first post and the dielectric base and the second adhesive laminates the second conductive layer and the second dielectric layer to the second post and the dielectric base.
Providing the pad can include removing selected portions of the first conductive layer after solidifying the first adhesive. The removing can include applying a wet chemical etch to the first conductive layer using an etch mask that defines the pad such that the pad includes a selected portion of the first conductive layer.
Providing the terminal can include removing selected portions of the second conductive layer after solidifying the second adhesive. The removing can include applying a wet chemical etch to the second conductive layer using an etch mask that defines the terminal such that the terminal includes a selected portion of the second conductive layer.
Providing the first cap can include removing selected portions of the first conductive layer after solidifying the first adhesive. The removing can include applying a wet chemical etch to the first conductive layer using an etch mask that defines the first cap such that the first cap includes a selected portion of the first conductive layer.
Providing the second cap can include removing selected portions of the second conductive layer after solidifying the second adhesive. The removing can include applying a wet chemical etch to the second conductive layer using an etch mask that defines the second cap such that the second cap includes a selected portion of the second conductive layer.
Providing the pad and the first cap can include removing selected portions of the first conductive layer using an etch mask that defines the pad and the first cap. Thus, the pad and the first cap can be formed simultaneously using the same etch mask and wet chemical etch.
Providing the terminal and the second cap can include removing selected portions of the second conductive layer using an etch mask that defines the terminal and the second cap. Thus, the terminal and the second cap can be formed simultaneously using the same etch mask and wet chemical etch.
Providing the pad and the first cap can include grinding the first post, the first adhesive and the first conductive layer after solidifying the first adhesive such that the first post, the first adhesive and the first conductive layer are laterally aligned with one another at a lateral surface that faces in the first vertical direction, and then removing selected portions of the first conductive layer such that the pad and the first cap include selected portions of the first conductive layer. The grinding can include grinding the first adhesive without grinding the first post and then grinding the first post, the first adhesive and the first conductive layer. The removing can include applying a wet chemical etch to the first conductive layer using an etch mask that defines the pad and the first cap.
Providing the terminal and the second cap can include grinding the second post, the second adhesive and the second conductive layer after solidifying the second adhesive such that the second post, the second adhesive and the second conductive layer are laterally aligned with one another at a lateral surface that faces in the second vertical direction, and then removing selected portions of the second conductive layer such that the terminal and the second cap include selected portions of the second conductive layer. The grinding can include grinding the second adhesive without grinding the second post and then grinding the second post, the second adhesive and the second conductive layer. The removing can include applying a wet chemical etch to the second conductive layer using an etch mask that defines the terminal and the second cap.
Providing the pad and the first cap can include depositing a first plated layer on the first post, the first adhesive and the first conductive layer after the grinding and then removing selected portions of the first conductive layer and the first plated layer such that the pad and the first cap include selected portions of the first conductive layer and the first plated layer. Depositing the first plated layer can include electrolessly plating an electrolessly plated layer on the first post, the first adhesive and the first conductive layer and then electroplating an electroplated layer on the electrolessly plated layer. The removing can include applying the wet chemical etch to the first conductive layer and the first plated layer using the etch mask to define the pad and the first cap.
Providing the terminal and the second cap can include depositing a second plated layer on the second post, the second adhesive and the second conductive layer after the grinding and then removing selected portions of the second conductive layer and the second plated layer such that the terminal and the second cap include selected portions of the second conductive layer and the second plated layer. Depositing the second plated layer can include electrolessly plating an electrolessly plated layer on the second post, the second adhesive and the second conductive layer and then electroplating an electroplated layer on the electrolessly plated layer. The removing can include applying the wet chemical etch to the second conductive layer and the second plated layer using the etch mask to define the terminal and the second cap.
Providing the conductive trace and the heat spreader can include providing a hole that extends through the dielectric base, the adhesives, the conductive layers and the dielectric layers after solidifying the adhesives, then depositing a plated metal on the posts, the adhesives, the conductive layers and the dielectric layers, wherein the plated metal forms a first plated layer that covers the first post in the first vertical direction, a second plated layer that covers the second post in the second vertical direction and the electrical interconnect as a plated through-hole in the hole, then forming a first etch mask on the first plated layer that defines the pad and the first cap, forming a second etch mask on the second plated layer that defines the terminal and the second cap, then etching the first conductive layer and the first plated layer in a first pattern defined by the first etch mask and etching the second conductive layer and the second plated layer in a second pattern defined by the second etch mask and then removing the etch masks.
The hole can be formed in a single step by mechanical drilling or laser drilling or multiple steps in which the conductive layers are opened by wet chemical etching and then the dielectric base, the adhesives and the dielectric layers are opened by laser drilling or plasma etching.
Etching the first conductive layer and the first plated layer can include exposing the first adhesive or the first dielectric layer in the first vertical direction without exposing the dielectric base in the first vertical direction, and etching the second conductive layer and the second plated layer can include exposing the second adhesive or the second dielectric layer in the second vertical direction without exposing the dielectric base in the second vertical direction.
The pad can be formed before, during or after the terminal is formed. Thus, the pad and the terminal can be formed simultaneously using the same wet chemical etch and different etch masks or sequentially using different etch masks. Likewise, the first cap can be formed before, during or after the second cap is formed. Thus, the caps can be formed simultaneously using the same wet chemical etch and different etch masks or sequentially using different etch masks. Similarly, the pad, the terminal and the caps can be formed simultaneously or sequentially.
The electrical interconnects can be formed in the same manner and the terminals can be formed in the same manner. Thus, the plated through-holes can be formed using the same plated layer and different holes and the terminals and the second cap can be formed simultaneously using the same etch mask and wet chemical etch.
Providing the conductive trace and the heat spreader can include providing first and second holes that extend through the dielectric base, the adhesives, the conductive layers and the dielectric layers, then depositing a plated metal on the posts, the adhesives, the conductive layers and the dielectric layers, wherein the plated metal forms a first plated layer that covers the first post in the first vertical direction, a second plated layer that covers the second post in the second vertical direction, the first plated through-hole in the first hole and the second plated through-hole in the second hole, then forming a first etch mask on the first plated layer that defines the pad and the first cap, forming a second etch mask on the second plated layer that defines the terminals and the second cap, then etching the first conductive layer and the first plated layer in a first pattern defined by the first etch mask, etching the second conductive layer and the second plated layer in a second pattern defined by the second etch mask and then removing the etch masks
Mounting the semiconductor device on the first post can include mounting the semiconductor device on the first cap and thus the first post. Mounting the semiconductor device can also include positioning the semiconductor device within the peripheries of the posts and caps and outside the periphery of the conductive trace. In any case, the semiconductor device extends laterally within the peripheries of the posts and the caps.
Mounting the semiconductor device can include providing a die attach between a semiconductor chip such as an LED chip and the first cap, electrically connecting the semiconductor device can include providing a wire bond between the chip and the pad, and thermally connecting the semiconductor device can include providing the die attach between the chip and the first cap.
Mounting the semiconductor device on the first cap can include providing a die attach between a non-vertical LED chip and the first cap, electrically connecting the semiconductor device to a first conductive trace can include providing a first wire bond between the LED chip and a first pad, thereby electrically connecting the LED chip to a first terminal, electrically connecting the semiconductor device to a second conductive trace can include providing a second wire bond between the LED chip and a second pad, thereby electrically connecting the LED chip to a second terminal, and thermally connecting the semiconductor device to the first cap can include providing the die attach between the LED chip and the first cap, thereby thermally connecting the LED chip to the posts and the second cap without electrically connecting the LED chip to the second post and the second cap.
Mounting the semiconductor device on the first cap can include providing a die attach between a vertical LED chip and the first cap, electrically connecting the semiconductor device to the pad can include providing a wire bond between the LED chip and the pad, thereby electrically connecting the LED chip to the first terminal, and electrically and thermally connecting the semiconductor device to the first cap can include providing the die attach between the LED chip and the first cap, thereby electrically connecting the LED chip to the second terminal and thermally connecting the LED chip to the posts and the second cap without electrically connecting the LED chip to the second post and the second cap.
The semiconductor device can be encapsulated by providing an encapsulant on the thermal board that covers the semiconductor device in the first vertical direction. Alternatively, the semiconductor device can be housed in a sealed enclosure by mounting a rim on the thermal board, then mounting the semiconductor device on the first cap and then mounting a lid on the rim.
The first adhesive can contact the first post, the first cap and the dielectric base, be spaced from the terminal, the second post and the second adhesive, cover and surround the first post in the lateral directions and extend to peripheral edges of the assembly after the assembly is manufactured and detached from other assemblies in a batch.
The second adhesive can contact the second post, the second cap and the dielectric base, be spaced from the pad, the first post and the first adhesive, cover and surround the second post in the lateral directions and extend to peripheral edges of the assembly after the assembly is manufactured and detached from other assemblies in a batch.
The dielectric base can cover the semiconductor device, the first post, the first cap and the pad in the second vertical direction, cover the second post, the second cap and the terminal in the first vertical direction, support the adhesives and extend to peripheral edges of the assembly after the assembly is manufactured and detached from other assemblies in a batch.
The present invention has numerous advantages. The heat spreader can provide excellent heat spreading and heat dissipation without heat flow through the adhesives. As a result, the adhesives can be a low cost dielectric with low thermal conductivity and not prone to delamination. The first post can provide thermal expansion matching with a semiconductor device mounted thereon, thereby increasing reliability. The first cap can be customized for the semiconductor device, thereby enhancing the thermal connection. The first adhesive can be sandwiched between the dielectric base and the pad and the second adhesive can be sandwiched between the dielectric base and the terminal, thereby providing a robust mechanical bond between the heat spreader and the conductive trace. The dielectric base can provide electrical isolation that protects the semiconductor device from electrostatic discharge in the second cap and enables the second cap to electrically float during operation of the semiconductor device. The conductive trace can provide signal routing with simple circuitry patterns or flexible multi-layer signal routing with complex circuitry patterns. The electrical interconnect can be a plated through-hole formed after the adhesives are solidified and remain a hollow tube or be split at a peripheral edge of the assembly. As a result, a solder joint subsequently reflowed on the terminal can wet and flow into the plated through-hole without creating a buried void in the solder joint beneath the plated through-hole that might otherwise occur if the plated through-hole is filled with the adhesives or another non-wettable insulator, thereby increasing reliability. The dielectric base can provide mechanical support for the conductive layers, the dielectric layers and the adhesives, thereby preventing warping. The assembly can be manufactured using low temperature processes which reduces stress and improves reliability. The assembly can also be manufactured using well-controlled processes which can be easily implemented by circuit board, lead frame and tape manufacturers.
These and other features and advantages of the present invention will be further described and more readily apparent from a review of the detailed description of the preferred embodiments which follows.
The following detailed description of the preferred embodiments of the present invention can best be understood when read in conjunction with the following drawings, in which:
Dielectric base 24 is an electrical insulator with high thermal conductivity that contacts and is sandwiched between and thermally connects and electrically isolates and mechanically attaches metal plates 12 and 14. Dielectric base 24 is illustrated as epoxy filled with aluminum nitride. Thus, aluminum nitride particles are dispersed in the epoxy. Dielectric base 24 is an unpatterned dielectric sheet with a thickness of 100 microns.
Dielectric base 24 is initially an epoxy paste that is deposited on metal plate 14, then metal plate 12 is mounted on the epoxy paste and then the epoxy paste is heated and hardened at a relatively low temperature such as 190° C. As a result, metal plates 12 and 14 and dielectric base 24 are a double-sided copper clad laminate.
The wet chemical etch is highly selective of copper and etches through metal plate 12 from the frontside and metal plate 14 from the backside. As a result, the etch etches through metal plate 12 to expose dielectric base 24 in the upward direction, and etches through metal plate 14 to expose dielectric base 24 in the downward direction. The wet chemical etch also laterally undercuts metal plate 12 beneath etch mask 16 and metal plate 14 above etch mask 18. A suitable wet chemical etch can be provided by a solution containing alkaline ammonia or a dilute mixture of nitric and hydrochloric acid Likewise, the wet chemical etch can be acidic or alkaline. The optimal etch time for forming posts 20 and 22 without excessively exposing metal plates 12 and 14 to the wet chemical etch can be established through trial and error.
Post 20 is an unetched portion of metal plate 12 defined by etch mask 16. Post 20 protrudes above dielectric base 24, has a height of 200 microns, a length and width at its top surface (square portion of metal plate 12 opposite dielectric base 24) of 1000 microns and a length and width at its bottom surface (square portion of metal plate 12 adjacent to dielectric base 24) of 1200 microns. Thus, post 20 has a cut-off pyramidal shape with tapered sidewalls characteristic of wet chemical etching in which its diameter decreases as it extends upwardly from dielectric base 24 to its flat square top surface. The tapered sidewalls arise from the lateral undercutting by the wet chemical etch beneath etch mask 16. The top surface is concentrically disposed within a periphery of the bottom surface (as shown in
Post 22 is an unetched portion of metal plate 14 defined by etch mask 18. Post 22 protrudes below dielectric base 24, has a height of 200 microns, a length and width at its bottom surface (rectangular portion of metal plate 14 opposite dielectric base 24) of 3000×5000 microns and a length and width at its top surface (rectangular portion of metal plate 14 adjacent to dielectric base 24) of 3200×5200 microns. Thus, post 22 has a cut-off pyramidal shape with tapered sidewalls characteristic of wet chemical etching in which its diameter decreases as it extends downwardly from dielectric base 24 to its flat rectangular bottom surface. The tapered sidewalls arise from the lateral undercutting by the wet chemical etch above etch mask 18. The bottom surface is concentrically disposed within a periphery of the top surface (as shown in
Posts 20 and 22 have the same thickness and are axially aligned with one another and are vertically offset from one another by dielectric base 24. However, post 20 has a far smaller length, width and surface area than post 22. As a result, post 20 is centrally located within the periphery of post 22.
Dielectric base 24 contacts and is sandwiched between and thermally connects and electrically isolates and mechanically attaches posts 20 and 22, covers post 20 in the downward direction, covers post 22 in the upward direction and extends laterally from posts 20 and 22 in a lateral plane (with lateral directions such as left and right). Dielectric base 24 provides the foundation for a unified structure that includes posts 20 and 22 as described below.
Posts 20 and 22 can be treated to improve bondability to epoxy and solder. For instance, posts 20 and 22 can be chemically oxidized or microetched to provide rougher surfaces.
Adhesive 26 can be various dielectric films or prepregs formed from numerous organic or inorganic electrical insulators. For instance, adhesive 26 can initially be a prepreg in which thermosetting epoxy in resin form impregnates a reinforcement and is partially cured to an intermediate stage. The epoxy can be FR-4 although other epoxies such as polyfunctional and bismaleimide triazine (BT) are suitable. For specific applications, cyanate esters, polyimide and PTFE are also suitable. The reinforcement can be E-glass although other reinforcements such as S-glass, D-glass, quartz, kevlar aramid and paper are suitable. The reinforcement can also be woven, non-woven or random microfiber. A filler such as silica (powdered fused quartz) can be added to the prepreg to improve thermal conductivity, thermal shock resistance and thermal expansion matching. Commercially available prepregs such as SPEEDBOARD C prepreg by W.L. Gore & Associates of Eau Claire, Wis. are suitable.
Substrate 30 is illustrated as a laminated structure. Substrate 30 can be other electrical interconnects such as a ceramic board or a printed circuit board. Likewise, substrate 30 can include additional layers of embedded circuitry.
Substrate 40 is illustrated as a laminated structure. Substrate 40 can be other electrical interconnects such as a ceramic board or a printed circuit board. Likewise, substrate 40 can include additional layers of embedded circuitry.
Adhesives 26 and 28 are identical prepregs except that opening 26A is far smaller than opening 28A. Likewise, conductive layers 32 and 42 are identical copper sheets and dielectric layers 34 and 44 are identical epoxy sheets except that aperture 30A is far smaller than aperture 40A. Furthermore, opening 26A and aperture 30A have the same shape and size and can be formed in the same manner with the same punch at the same punching station or the same drill bit at the same drilling station, and opening 28A and aperture 40A have the same shape and size and can be formed in the same manner with the same punch at the same punching station or the same drill bit at the same drilling station.
In
At this stage, substrate 30 is mounted on and contacts and extends above adhesive 26, adhesive 26 is mounted on and contacts and extends above dielectric base 24, dielectric base 24 is mounted on and contacts and extends above adhesive 28 and adhesive 28 is mounted on and contacts and extends above substrate 40. Thus, dielectric base 24 contacts and is sandwiched between adhesives 26 and 28 and is spaced from substrates 30 and 40, adhesive 26 contacts and is sandwiched between dielectric base 24 and dielectric layer 34 and is spaced from conductive layer 32, adhesive 28 contacts and is sandwiched between dielectric base 24 and dielectric layer 44 and is spaced from conductive layer 42, dielectric layer 34 contacts and is sandwiched between adhesive 26 and conductive layer 32 and dielectric layer 44 contacts and is sandwiched between adhesive 28 and conductive layer 42.
Post 20 extends through opening 26A into aperture 30A, is aligned with opening 26A and aperture 30A, is 30 microns below the top surface of conductive layer 32 and is exposed through aperture 30A in the upward direction. Post 20 remains adjacent to dielectric base 24 and spaced from adhesive 26, conductive layer 32 and dielectric layer 34.
Post 22 extends through opening 28A into aperture 40A, is aligned with opening 28A and aperture 40A, is 30 microns above the bottom surface of conductive layer 42 and is exposed through aperture 40A in the downward direction. Post 22 remains adjacent to dielectric base 24 and spaced from adhesive 28, conductive layer 42 and dielectric layer 44.
Adhesive 26 remains a non-solidified prepreg with B-stage uncured epoxy, adhesive 28 remains a non-solidified prepreg with B-stage uncured epoxy and adhesives 26 and 28 remain spaced from one another.
Dielectric layer 34 remains a solidified epoxy sheet, dielectric layer 44 remains a solidified epoxy sheet and dielectric layers 34 and 44 remain spaced from one another.
Post 20, opening 26A and aperture 30A are axially aligned with and located within the periphery of post 22. As a result, post 22 covers post 20, opening 26A and aperture 30A in the downward direction.
Gap 46 is located in aperture 30A between post 20 and substrate 30 and gap 48 is located in aperture 40A between post 22 and substrate 40. Gap 46 laterally surrounds post 20 and is laterally surrounded by conductive layer 32 and dielectric layer 34 and gap 48 laterally surrounds post 22 and is laterally surrounded by conductive layer 42 and dielectric layer 44.
Adhesive 26 is flowed into gap 46 and adhesive 28 is flowed into gap 48 by applying heat and pressure. In this illustration, adhesive 26 is forced into gap 46 and adhesive 28 is forced into gap 48 by applying downward pressure to conductive layer 32 and/or upward pressure to conductive layer 42, thereby moving dielectric base 24 and substrate 30 towards one another, moving dielectric base 24 and substrate 40 towards one another and applying pressure to adhesives 26 and 28 while simultaneously applying heat to adhesives 26 and 28. Adhesives 26 and 28 become compliant enough under the heat and pressure to conform to virtually any shape.
As a result, adhesive 26 sandwiched between dielectric base 24 and substrate 30 is compressed, forced out of its original shape and flows into and upward in gap 46. Likewise, adhesive 28 sandwiched between dielectric base 24 and substrate 40 is compressed, forced out of its original shape and flows into and downward in gap 48. Dielectric base 24 and substrate 30 continue to move towards one another and adhesive 26 eventually fills gap 46. Likewise, dielectric base 24 and substrate 40 continue to move towards one another and adhesive 28 eventually fills gap 48. Moreover, adhesive 26 remains sandwiched between and continues to fill the reduced space between dielectric base 24 and substrate 30 and adhesive 28 remains sandwiched between and continues to fill the reduced space between dielectric base 24 and substrate 40.
For instance, conductive layers 32 and 42 can be disposed between top and bottom platens (not shown) of a press. In addition, a top cull plate and top buffer paper (not shown) can be sandwiched between conductive layer 32 and the top platen, and a bottom cull plate and bottom buffer paper (not shown) can be sandwiched between conductive layer 42 and the bottom platen. The stack includes the top platen, top cull plate, top buffer paper, conductive layer 32, dielectric layer 34, adhesive 26, dielectric base 24, adhesive 28, dielectric layer 44, conductive layer 42, bottom buffer paper, bottom cull plate and bottom platen in descending order. Furthermore, the stack may be positioned on the bottom platen by tooling pins (not shown) that extend upward from the bottom platen through registration holes (not shown) in dielectric base 24.
The platens are heated and move towards one another, thereby applying heat and pressure to adhesives 26 and 28. The cull plates disperse the heat from the platens so that it is more uniformly applied to substrates 30 and 40 and thus adhesives 26 and 28, and the buffer papers disperse the pressure from the platens so that it is more uniformly applied to substrates 30 and 40 and thus adhesives 26 and 28. Initially, dielectric layer 34 contacts and presses down on adhesive 26 and dielectric layer 44 contacts and presses up on adhesive 28.
As the platen motion and heat continue, adhesive 26 between dielectric base 24 and dielectric layer 34 is compressed, melted and flows into and upward in gap 46 across conductive layer 32 and dielectric layer 34 and adhesive 28 between dielectric base 24 and dielectric layer 44 is compressed, melted and flows into and downward in gap 48 across conductive layer 42 and dielectric layer 44. For instance, in adhesive 26 the uncured epoxy is melted by the heat and the molten uncured epoxy is squeezed by the pressure into gap 46, however the reinforcement and the filler remain between dielectric base 24 and dielectric layer 34. Likewise, in adhesive 28 the uncured epoxy is melted by the heat and the molten uncured epoxy is squeezed by the pressure into gap 48, however the reinforcement and the filler remain between dielectric base 24 and dielectric layer 44.
Adhesive 26 ascends more rapidly than post 20 in aperture 30A, fills and extends slightly above gap 46 and overflows onto the top surfaces of post 20 and conductive layer 32 adjacent to gap 46 before the platen motion stops. This may occur due to the prepreg being slightly thicker than necessary. As a result, adhesive 26 creates a thin coating on the top surfaces of post 20 and conductive layer 32.
Adhesive 28 descends more rapidly than post 22 in aperture 40A, fills and extends slightly below gap 48 and overflows onto the bottom surfaces of post 22 and conductive layer 42 adjacent to gap 48 before the platen motion stops. This may occur due to the prepreg being slightly thicker than necessary. As a result, adhesive 28 creates a thin coating on the bottom surfaces of post 22 and conductive layer 42.
The platen motion is eventually blocked by posts 20 and 22 and the platens become stationary but continue to apply heat to adhesives 26 and 28.
The upward flow of adhesive 26 in gap 46 is shown by the thick upward arrows, the downward flow of adhesive 28 in gap 48 is shown by the thick downward arrows, the upward motion of substrate 40 relative to post 22 and dielectric base 24 is shown by the thin upward arrows, and the downward motion of substrate 30 relative to post 20 and dielectric base 24 is shown by the thin downward arrows.
For instance, the platens continue to clamp posts 20 and 22 and apply heat after the platen motion stops, thereby converting the B-stage molten uncured epoxy into C-stage cured or hardened epoxy. Thus, the epoxy is cured in a manner similar to conventional multi-layer lamination. After the epoxy is cured, the platens move away from one another and the structure is released from the press.
Adhesive 26 as solidified provides a secure robust mechanical bond between post 20 and substrate 30 and between dielectric base 24 and substrate 30. Adhesive 26 can withstand normal operating pressure without distortion or damage and is only temporarily distorted under unusually high pressure. Furthermore, adhesive 26 can absorb thermal expansion mismatch between post 20 and substrate 30 and between dielectric base 24 and substrate 30.
Adhesive 28 as solidified provides a secure robust mechanical bond between post 22 and substrate 40 and between dielectric base 24 and substrate 40. Adhesive 28 can withstand normal operating pressure without distortion or damage and is only temporarily distorted under unusually high pressure. Furthermore, adhesive 28 can absorb thermal expansion mismatch between post 22 and substrate 40 and between dielectric base 24 and substrate 40.
Post 20 and conductive layer 32 are essentially coplanar with one another and adhesive 26 and conductive layer 32 extend to a top surface that faces in the upward direction. For instance, adhesive 26 between dielectric base 24 and dielectric layer 34 has a thickness of 70 microns which is 30 microns less than its initial thickness of 100 microns, post 20 ascends 30 microns in aperture 30A and conductive layer 32 and dielectric layer 34 descend 30 microns relative to post 20. The 200 micron height of post 20 is essentially the same as the combined height of conductive layer 32 (30 microns), dielectric layer 34 (100 microns) and the underlying adhesive 26 (70 microns). Furthermore, post 20 continues to be centrally located in opening 26A and aperture 30A and spaced from conductive layer 32 and dielectric layer 34 and adhesive 26 fills the space between post 20 and conductive layer 32, between post 20 and dielectric layer 34 and between dielectric base 24 and dielectric layer 34 and fills gap 46. For instance, gap 46 (as well as adhesive 26 between post 20 and conductive layer 32) has a width of 125 microns ((1250−1000)/2) at the top surface of post 20.
Post 22 and conductive layer 42 are essentially coplanar with one another and adhesive 28 and conductive layer 42 extend to a bottom surface that faces in the downward direction. For instance, adhesive 28 between dielectric base 24 and dielectric layer 44 has a thickness of 70 microns which is 30 microns less than its initial thickness of 100 microns, post 22 descends 30 microns in aperture 40A and conductive layer 42 and dielectric layer 44 ascend 30 microns relative to post 22. The 200 micron height of post 22 is essentially the same as the combined height of conductive layer 42 (30 microns), dielectric layer 44 (100 microns) and the overlying adhesive 28 (70 microns). Furthermore, post 22 continues to be centrally located in opening 28A and aperture 40A and spaced from conductive layer 42 and dielectric layer 44 and adhesive 28 fills the space between post 22 and conductive layer 42, between post 22 and dielectric layer 44 and between dielectric base 24 and dielectric layer 44 and fills gap 48. For instance, gap 48 (as well as adhesive 28 between post 22 and conductive layer 42) has a width of 125 microns (((3250−3000)/2) and ((5250−5000)/2)) at the bottom surface of post 22.
Adhesive 26 extends across dielectric layer 34 in gap 46. That is, adhesive 26 in gap 46 extends in the upward and downward directions across the thickness of dielectric layer 34 at the outer sidewall of gap 46. Adhesive 26 also includes a thin top portion above gap 46 that contacts the top surfaces of post 20 and conductive layer 32 and extends above post 20 by 10 microns.
Adhesive 28 extends across dielectric layer 44 in gap 48. That is, adhesive 28 in gap 48 extends in the upward and downward directions across the thickness of dielectric layer 44 at the outer sidewall of gap 48. Adhesive 28 also includes a thin bottom portion below gap 48 that contacts the bottom surfaces of post 22 and conductive layer 42 and extends below post 22 by 10 microns.
Post 20, adhesive 26 and conductive layer 32 have their upper portions removed by grinding. For instance, a rotating diamond sand wheel and distilled water are applied to the top of the structure. Initially, the diamond sand wheel grinds only adhesive 26. As the grinding continues, adhesive 26 becomes thinner as its grinded surface migrates downwardly. Eventually the diamond sand wheel contacts post 20 and conductive layer 32 (not necessarily at the same time), and as a result, begins to grind post 20 and conductive layer 32 as well. As the grinding continues, post 20, adhesive 26 and conductive layer 32 become thinner as their grinded surfaces migrate downwardly. The grinding continues until the desired thickness has been removed. Thereafter, the structure is rinsed in distilled water to remove contaminants.
The grinding removes a 25 micron thick upper portion of adhesive 26, a 15 micron thick upper portion of post 20 and a 15 micron thick upper portion of conductive layer 32. The decreased thickness does not appreciably affect post 20 or adhesive 26. However, it substantially reduces the thickness of conductive layer 32 from 30 microns to 15 microns.
Post 22, adhesive 28 and conductive layer 42 have their lower portions removed by grinding. For instance, a rotating diamond sand wheel and distilled water are applied to the bottom of the structure. Initially, the diamond sand wheel grinds only adhesive 28. As the grinding continues, adhesive 28 becomes thinner as its grinded surface migrates upwardly. Eventually the diamond sand wheel contacts post 22 and conductive layer 42 (not necessarily at the same time), and as a result, begins to grind post 22 and conductive layer 42 as well. As the grinding continues, post 22, adhesive 28 and conductive layer 42 become thinner as their grinded surfaces migrate upwardly. The grinding continues until the desired thickness has been removed. Thereafter, the structure is rinsed in distilled water to remove contaminants.
The grinding removes a 25 micron thick lower portion of adhesive 28, a 15 micron thick lower portion of post 22 and a 15 micron thick lower portion of conductive layer 42. The decreased thickness does not appreciably affect post 22 or adhesive 28. However, it substantially reduces the thickness of conductive layer 42 from 30 microns to 15 microns.
At this stage, post 20, adhesive 26 and conductive layer 32 are coplanar with one another at a smoothed lapped lateral top surface that is above dielectric layer 34 and faces in the upward direction Likewise, post 22, adhesive 28 and conductive layer 42 are coplanar with one another at a smoothed lapped lateral bottom surface that is below dielectric layer 44 and faces in the downward direction.
Plated layer 54 is deposited on and contacts post 20, adhesive 26 and conductive layer 32 at the lateral top surface and covers them in the upward direction. Plated layer 54 is an unpatterned copper layer with a thickness of 20 microns.
Plated layer 56 is deposited on and contacts post 22, adhesive 28 and conductive layer 42 at the lateral bottom surface and covers them in the downward direction. Plated layer 56 is an unpatterned copper layer with a thickness of 20 microns.
Plated through-hole 58 is deposited on and extends through dielectric base 24, adhesives 26 and 28, conductive layers 32 and 42 and dielectric layers 34 and 44 in hole 50 and covers the sidewall in the lateral directions. Plated through-hole 58 is a copper tube with a thickness of 20 microns that is metallurgically bonded to and electrically connects conductive layers 32 and 42.
For instance, the structure is dipped in an activator solution to render dielectric base 24, adhesives 26 and 28 and dielectric layers 34 and 44 catalytic to electroless copper, then a first copper layer is electrolessly plated on posts 20 and 22, dielectric base 24, adhesives 26 and 28, conductive layers 32 and 42 and dielectric layers 34 and 44, and then a second copper layer is electroplated on the first copper layer. The first copper layer has a thickness of 2 microns, the second copper layer has a thickness of 18 microns, and plated metal 52 (and plated layers 54 and 56 and plated through-hole 58) has a thickness of 20 microns. As a result, conductive layer 32 essentially grows and has a thickness of 35 microns (15+20) and conductive layer 42 essentially grows and has a thickness of 35 microns (15+20).
Plated layer 54 serves as a cover layer for post 20 and adhesive 26 and a build-up layer for conductive layer 32, plated layer 56 serves as a cover layer for post 22 and adhesive 28 and a build-up layer for conductive layer 42 and plated through-hole 58 serves as an electrical interconnect between conductive layers 32 and 42 and between plated layers 54 and 56.
Post 20, conductive layer 32, plated layer 54 and plated through-hole 58 are shown as a single layer for convenience of illustration. Likewise, post 22, conductive layer 42, plated layer 56 and plated through-hole 58 are shown as a single layer for convenience of illustration. The boundary (shown in phantom) between post 20 and plated layer 54, between conductive layer 32 and plated layer 54, between post 22 and plated layer 56 and between conductive layer 42 and plated layer 56 may be difficult or impossible to detect since copper is plated on copper. However, the boundary between dielectric base 24 and plated through-hole 58 in hole 50, between adhesive 26 and plated through-hole 58 in hole 50, between adhesive 28 and plated through-hole 58 in hole 50, between dielectric layer 34 and plated through-hole 58 in hole 50, between dielectric layer 44 and plated through-hole 58 in hole 50, between adhesive 26 and plated layer 54 outside hole 50 and between adhesive 28 and plated layer 56 outside hole 50 is clear.
Conductive layer 32 and plated layer 54 as etched include pad 64, routing line 66 and cap 68. Pad 64, routing line 66 and cap 68 are unetched portions of conductive layer 32 and plated layer 54 defined by etch mask 60. Thus, conductive layer 32 and plated layer 54 are a patterned layer that includes pad 64, routing line 66 and cap 68.
Pad 64 is an unetched portion of conductive layer 32 and plated layer 54 defined by etch mask 60 that is spaced from plated through-hole 58. Routing line 66 is an unetched portion of conductive layer 32 and plated layer 54 defined by etch mask 60 that is adjacent to and extends laterally from and electrically connects plated through-hole 58 and pad 64. Cap 68 is an unetched portion of conductive layer 32 and plated layer 54 defined by etch mask 60 that is adjacent to and extends laterally from and is thermally connected to post 20.
Pad 64 and routing line 66 contact dielectric layer 34, are spaced from adhesive 26 and extend above adhesive 26 and dielectric layer 34. Cap 68 contacts and extends above adhesive 26 and dielectric layer 34.
Pad 64 has a thickness of 35 microns (15+20). Cap 68 has a thickness of 20 microns where it is adjacent to post 20 and excludes conductive layer 32 and a thickness of 35 microns (15+20) where it is closest to pad 64 and includes a selected portion of conductive layer 32. Cap 68 also has a thickness of 20 microns where it contacts adhesive 26, is spaced from dielectric layer 34 and covers opening 26A and aperture 30A in the upward direction and a thickness of 35 microns where it contacts dielectric layer 34. Thus, pad 64 and cap 68 have the same thickness where they are closest to one another, have different thickness where cap 68 is adjacent to post 20 and are spaced from and coplanar with one another.
Conductive layer 42 and plated layer 56 as etched include terminal 70 and cap 72. Terminal 70 and cap 72 are unetched portions of conductive layer 42 and plated layer 56 defined by etch mask 62. Thus, conductive layer 42 and plated layer 56 are a patterned layer that includes terminal 70 and cap 72.
Terminal 70 is an unetched portion of conductive layer 42 and plated layer 56 defined by etch mask 62 that is adjacent to and extends laterally from and is electrically connected to plated through-hole 58. Cap 72 is an unetched portion of conductive layer 42 and plated layer 56 defined by etch mask 62 that is adjacent to and extends laterally from and is thermally connected to post 22.
Terminal 70 contacts dielectric layer 44, is spaced from adhesive 28 and extends below adhesive 28 and dielectric layer 44. Cap 72 contacts and extends below adhesive 28 and dielectric layer 44.
Terminal 70 has a thickness of 35 microns (15+20). Cap 72 has a thickness of 20 microns where it is adjacent to post 22 and excludes conductive layer 42 and a thickness of 35 microns (15+20) where it is closest to terminal 70 and includes a selected portion of conductive layer 42. Cap 72 also has a thickness of 20 microns where it contacts adhesive 28, is spaced from dielectric layer 44 and covers opening 28A and aperture 40A in the downward direction and a thickness of 35 microns where it contacts dielectric layer 44. Thus, terminal 70 and cap 72 have the same thickness where they are closest to one another, have different thickness where cap 72 is adjacent to post 22 and are spaced from and coplanar with one another.
Conductive trace 74 is provided by plated through-hole 58, pad 64, routing line 66 and terminal 70. Similarly, an electrically conductive path between pad 64 and terminal 70 is plated through-hole 58 and routing line 66.
Furthermore, pad 64 is located within the peripheries of post 22 and cap 72, routing line 66 extends within and outside the peripheries of post 22 and cap 72 and plated through-hole 58 and terminal 70 are located outside the peripheries of post 22 and cap 72.
Heat spreader 76 is provided by posts 20 and 22, dielectric base 24 and caps 68 and 72. Post 20 extends above dielectric base 24, extends above and below dielectric layer 34 and is sandwiched between dielectric base 24 and cap 68. Post 22 extends below dielectric base 24, extends above and below dielectric layer 44 and is sandwiched between dielectric base 24 and cap 72. Dielectric base 24 contacts and is sandwiched between and thermally connects and electrically isolates posts 20 and 22, covers post 20 in the downward direction, covers post 22 in the upward direction and extends laterally in the lateral directions from posts 20 and 22. Cap 68 is above and adjacent to and covers in the upward direction and extends laterally in the lateral directions from the top of post 20 and is positioned so that post 20 is centrally located within its periphery Likewise, cap 72 is below and adjacent to and covers in the downward direction and extends laterally in the lateral directions from the bottom of post 22 and is positioned so that post 22 is centrally located within its periphery.
Posts 20 and 22 and caps 68 and 72 are axially aligned with one another, post 20 and cap 68 are located within the peripheries of post 22 and cap 72 and post 22 is located within the periphery of cap 72. As a result, post 22 and cap 72 cover post 20 and cap 68 in the downward direction. Furthermore, the surface area of post 20 is less than one-half the surface area of post 22.
Heat spreader 76 is essentially a heat slug with a small upper pedestal (post 20), a large lower pedestal (post 22), upper wings that extend laterally from the upper pedestal (cap 68), lower wings that extend laterally from the lower pedestal (cap 72) and a middle segment sandwiched between the upper and lower pedestals (dielectric base 24).
Plated contacts 78 are thin spot plated metal coatings that contact the exposed copper surfaces. Thus, plated contacts 78 contact plated through-hole 58, pad 64, routing line 66 and cap 68 and cover them in the upward direction and contact plated through-hole 58, terminal 70 and cap 72 and cover them in the downward direction. For instance, a nickel layer is electrolessly plated on the exposed copper surfaces, and then a silver layer is electrolessly plated on the nickel layer. The buried nickel layer has a thickness of 3 microns, the silver surface layer has a thickness of 0.5 microns, and plated contacts 78 have a thickness of 3.5 microns.
Pad 64, cap 68, terminal 70 and cap 72 treated with plated contacts 78 as a surface finish have several advantages. The buried nickel layer provides the primary mechanical and electrical and/or thermal connection, and the silver surface layer provides a wettable surface to facilitate solder reflow and accommodates a solder joint and a wire bond. Plated contacts 78 also protect conductive trace 74 and heat spreader 76 from corrosion. Plated contacts 78 can include a wide variety of metals to accommodate the external connection media. For instance, a gold surface layer can be plated on a buried nickel layer or a nickel surface layer alone can be employed.
Pad 64, cap 68, terminal 70 and cap 72 treated with plated contacts 78 are shown as single layers for convenience of illustration. The boundary (not shown) in conductive trace 74 and heat spreader 76 with plated contacts 78 occurs at the copper/nickel interface.
At this stage, the manufacture of thermal board 90 can be considered complete.
Thermal board 90 includes adhesives 26 and 28, substrates 30 and 40, conductive trace 74 and heat spreader 76. Substrate 30 includes dielectric layer 34. Substrate 40 includes dielectric layer 44. Conductive trace 74 includes plated through-hole 58, pad 64, routing line 66 and terminal 70. Heat spreader 76 includes posts 20 and 22, dielectric base 24 and caps 68 and 72.
Post 20 extends into and remains centrally located within opening 26A and aperture 30A and remains centrally located within the peripheries of post 22, dielectric base 24, adhesives 26 and 28, dielectric layers 34 and 44 and caps 68 and 72. Post 20 retains its cut-off pyramidal shape with tapered sidewalls characteristic of wet chemical etching in which its diameter decreases (length and width) as it extends upwardly from dielectric base 24 to its flat square top adjacent to cap 68. Post 20 is also coplanar with adhesive 26 at their tops at cap 68 between top and bottom (opposing lateral) surfaces of pad 64 and at their bottoms at dielectric base 24.
Post 22 extends into and remains centrally located within opening 28A and aperture 40A and remains centrally located within the peripheries of dielectric base 24, adhesives 26 and 28, dielectric layers 34 and 44 and cap 72. Post 22 retains its cut-off pyramidal shape with tapered sidewalls characteristic of wet chemical etching in which its diameter (length and width) decreases as it extends downwardly from dielectric base 24 to its flat rectangular bottom adjacent to cap 72. Post 22 is also coplanar with adhesive 28 at their tops at dielectric base 24 and at their bottoms at cap 72 between top and bottom (opposing lateral) surfaces of terminal 70.
Dielectric base 24 is located below post 20 and covers post 20 in the downward direction, is located above post 22 and covers post 22 in the upward direction and extends laterally from posts 20 and 22 to the peripheral edges of thermal board 90. Dielectric base 24 remains sandwiched between posts 20 and 22, adhesives 26 and 28, dielectric layers 34 and 44 and caps 68 and 72 and provides thermal coupling and electrical isolation for posts 20 and 22 and mechanical support for posts 20 and 22, adhesives 26 and 28, dielectric layers 34 and 44 and conductive trace 74.
Adhesive 26 contacts and is sandwiched between post 20 and dielectric layer 34, between post 20 and plated through-hole 58, between dielectric base 24 and dielectric layer 34 and between dielectric base 24 and cap 68 and is spaced from post 22, adhesive 28, dielectric layer 44, terminal 70 and cap 72. Adhesive 26 also extends laterally from post 20 beyond and overlaps terminal 70, covers cap 68 outside the periphery of post 20 in the downward direction, covers and surrounds post 20 in the lateral directions and is solidified.
Adhesive 28 contacts and is sandwiched between post 22 and dielectric layer 44, between post 22 and plated through-hole 58, between dielectric base 24 and dielectric layer 44 and between dielectric base 24 and cap 72 and is spaced from post 20, adhesive 26, dielectric layer 34, pad 64, routing line 66 and cap 68. Adhesive 28 also extends laterally from post 22 beyond and overlaps terminal 70, covers cap 72 outside the periphery of post 22 in the upward direction, covers and surrounds post 22 in the lateral directions and is solidified.
Adhesive 26 alone can intersect an imaginary horizontal line between post 20 and dielectric layer 34, an imaginary horizontal line between post 20 and plated through-hole 58, an imaginary vertical line between dielectric base 24 and dielectric layer 34 and an imaginary vertical line between dielectric base 24 and cap 68. Thus, an imaginary horizontal line exists that intersects only adhesive 26 as the line extends from post 20 to dielectric layer 34, an imaginary vertical line exists that intersects only adhesive 26 as the line extends from dielectric base 24 to cap 68 and so on.
Adhesive 28 alone can intersect an imaginary horizontal line between post 22 and dielectric layer 44, an imaginary horizontal line between post 22 and plated through-hole 58, an imaginary vertical line between dielectric base 24 and dielectric layer 44 and an imaginary vertical line between dielectric base 24 and cap 72. Thus, an imaginary horizontal line exists that intersects only adhesive 28 as the line extends from post 22 to dielectric layer 44, an imaginary vertical line exists that intersects only adhesive 28 as the line extends from dielectric base 24 to cap 72 and so on.
Substrate 30 contacts adhesive 26, is located above dielectric base 24 and is spaced from post 20 and dielectric base 24. Substrate 30 includes pad 64 and routing line 66 but does not include terminal 70. Furthermore, dielectric layer 34 contacts and is sandwiched between adhesive 26 and pad 64, between adhesive 26 and routing line 66 and between adhesive 26 and cap 68.
Substrate 40 contacts adhesive 28, is located below dielectric base 24 and is spaced from post 22 and dielectric base 24. Substrate 40 includes terminal 70 but does not include pad 64 and routing line 66. Furthermore, dielectric layer 44 contacts and is sandwiched between adhesive 28 and terminal 70 and between adhesive 28 and cap 72.
Plated through-hole 58 contacts and extends through dielectric base 24, adhesives 26 and 28 and dielectric layers 34 and 44 in hole 50. Plated through-hole 58 also retains its tubular shape with straight vertical inner and outer sidewalls in which its diameter is constant as it extends vertically from routing line 66 to terminal 70.
Pad 64 and cap 68 have the same thickness where they are closest to one another, have different thickness where cap 68 is adjacent to post 20 and are coplanar with one another above adhesive 26 and dielectric layer 34 at a top surface that faces in the upward direction.
Terminal 70 and cap 72 have the same thickness where they are closest to one another, have different thickness where cap 72 is adjacent to post 22 and are coplanar with one another below adhesive 28 and dielectric layer 44 at a bottom surface that faces in the downward direction.
Posts 20 and 22 are electrically isolated from one another and caps 68 and 72 are electrically isolated from one another.
Dielectric base 24, adhesives 26 and 28 and dielectric layers 34 and 44 extend to straight vertical peripheral edges of thermal board 90 after it is detached or singulated from a batch of identical simultaneously manufactured thermal boards.
Pad 64 is customized as an electrical interface for a semiconductor device such as an LED chip that is subsequently mounted on cap 68, terminal 70 is customized as an electrical interface for the next level assembly such as a solderable electrical contact from a printed circuit board, cap 68 is customized as a thermal interface for the semiconductor device, and cap 72 is customized as a thermal interface for the next level assembly such as the printed circuit board or a heat sink for an electronic device.
Pad 64 and terminal 70 are horizontally and vertically offset from one another and exposed at the top and bottom surfaces, respectively, of thermal board 90, thereby providing horizontal and vertical signal routing between the semiconductor device and the next level assembly.
Conductive trace 74 provides horizontal (fan-out) routing from pad 64 to plated through-hole 58 by routing line 66 and vertical (top to bottom) routing from pad 64 to terminal 70 by plated through-hole 58. Conductive trace 74 is not limited to this configuration. For instance, pad 64 can be electrically connected to plated through-hole 58 without a routing line as defined by etch mask 60, and terminal 70 can be electrically connected to plated through-hole 58 by a routing line as defined by etch mask 62. Pad 64 or routing line 66 can be electrically connected to terminal 70 by separate plated through-holes 58 in separate electrically conductive paths. Furthermore, the electrically conductive path can include vias that extend through adhesive 26, adhesive 28, dielectric layer 34 and/or dielectric layer 44 and routing lines (above and/or below adhesive 26, adhesive 28, dielectric layer 34 and/or dielectric layer 44) as well as passive components such as resistors and capacitors mounted on additional pads.
Conductive trace 74 is shown in cross-section as a continuous circuit trace for convenience of illustration. However, conductive trace 74 can provide horizontal signal routing in both the X and Y directions. That is, pad 64 and terminal 70 can be laterally offset from one another in the X and Y directions. Furthermore, plated through-hole 58 can be located between pad 64 and cap 68, between terminal 70 and cap 72 or at a corner or peripheral edge of thermal board 90.
Conductive trace 74 and heat spreader 76 remain spaced from one another. As a result, conductive trace 74 and heat spreader 76 are mechanically attached and electrically isolated from one another.
Heat spreader 76 provides heat spreading and heat dissipation from a semiconductor device that is subsequently mounted on cap 68 to the next level assembly that thermal board 90 is subsequently mounted on. The semiconductor device generates heat that flows into cap 68, from cap 68 into post 20, through post 20 into dielectric base 24, through dielectric base 24 into post 22 and through post 22 into cap 72, where it is spread out relative to post 20 and dissipated in the downward direction, for instance to an underlying heat sink.
Posts 20 and 22 are copper. Plated through-hole 58, pad 64, routing line 66, cap 68, terminal 70 and cap 72 are copper/nickel/silver. Plated through-hole 58, pad 64, routing line 66, cap 68, terminal 70 and cap 72 consist of a silver surface layer, a buried copper core and a buried nickel layer that contacts and is sandwiched between the silver surface layer and the buried copper core. Plated through-hole 58, pad 64, routing line 66, cap 68, terminal 70 and cap 72 are also primarily copper at the buried copper core. Plated contacts 78 provide the silver surface layer and the buried nickel layer and various combinations of metal plates 12 and 14, conductive layers 32 and 42 and plated metal 52 provide the buried copper core.
Conductive trace 74 includes a buried copper core shared by plated through-hole 58, pad 64, routing line 66 and terminal 70 and heat spreader 76 includes a first buried copper core shared by post 20 and cap 68 and a second buried copper core shared by post 22 and cap 72. Furthermore, conductive trace 74 includes a plated contact 78 at plated through-hole 58, pad 64, routing line 66 and terminal 70 and heat spreader 76 includes a plated contact 78 at cap 68 and spaced from posts 20 and 22 and another plated contact 78 at cap 72 and spaced from posts 20 and 22. Moreover, conductive trace 74 consists of copper/nickel/silver and is primarily copper at the buried copper core and heat spreader 76 consists of copper/nickel/silver and is primarily copper at the buried copper cores outside dielectric base 24.
Thermal board 90 does not expose post 20, post 22, dielectric base 24, adhesive 26 or adhesive 28 in the upward or downward direction. Post 20 is shown in phantom in
Thermal board 90 can include multiple conductive traces 74 with a plated through-hole 58, pad 64, routing line 66 and terminal 70. A single conductive trace 74 is described and labeled for convenience of illustration. In conductive traces 74, plated through-holes 58, pads 64 and terminals 70 generally have similar shapes and sizes whereas routing lines 66 may (but need not) have different routing configurations. For instance, some conductive traces 74 may be spaced and separated and electrically isolated from one another whereas other conductive traces 74 can intersect or route to the same pad 64, routing line 66 or terminal 70 and be electrically connected to one another. Likewise, some pads 64 may receive independent signals whereas other pads 64 share a common signal, power or ground.
Thermal board 90 can be adapted for an LED package with blue, green and red LED chips, with each LED chip including an anode and a cathode and each LED package including a corresponding anode terminal and cathode terminal. In this instance, thermal board 90 can include six pads 64 and four terminals 70 so that each anode is routed from a separate pad 64 to a separate terminal 70 whereas each cathode is routed from a separate pad 64 to a common ground terminal 70.
A brief cleaning step can be applied to the structure at various manufacturing stages to remove oxides and debris that may be present on the exposed metal. For instance, a brief oxygen plasma cleaning step can be applied to the structure. Alternatively, a brief wet chemical cleaning step using a solution containing potassium permanganate can be applied to the structure. Likewise, the structure can be rinsed in distilled water to remove contaminants. The cleaning step cleans the desired surfaces without appreciably affecting or damaging the structure.
Advantageously, there is no plating bus or related circuitry that need be disconnected or severed from conductive traces 74 after they are formed. A plating bus can be disconnected during the wet chemical etch that forms pad 64, routing line 66, cap 68, terminal 70 and cap 72.
Thermal board 90 can include registration holes (not shown) that are drilled or sliced through dielectric base 24, adhesives 26 and 28 and dielectric layers 34 and 44 so that thermal board 90 can be positioned by inserting tooling pins through the registration holes when it is subsequently mounted on an underlying carrier.
Thermal board 90 can accommodate multiple semiconductor devices rather than one with a single post 20 or multiple posts 20. Thus, multiple semiconductor devices can be mounted on a single post 20 or separate semiconductor devices can be mounted on separate posts 20. Likewise, multiple semiconductor devices can be mounted on a single cap 68 or separate semiconductor devices can be mounted on multiple caps 68.
Thermal board 90 with a single post 20 for multiple semiconductor devices can be accomplished by drilling additional holes to define additional plated through-holes 58, adjusting etch mask 60 to define additional pads 64 and routing lines 66 and adjusting etch mask 62 to define additional terminals 70. The plated through-holes 58, pads 64, routing lines 66 and terminals 70 can be laterally repositioned to provide a 2×2 array for four semiconductor devices. In addition, the topography (lateral shape) can be adjusted for pads 64 and terminals 70.
Thermal board 90 with multiple posts 20 for multiple semiconductor devices can be accomplished by adjusting etch mask 16 to define additional posts 20, adjusting adhesive 26 to include additional openings 26A, adjusting substrate 30 to include additional apertures 30A, drilling additional holes 50 to define additional plated through-holes 58, adjusting etch mask 60 to define additional pads 64, routing lines 66 and caps 68 and adjusting etch mask 62 to define additional terminals 70. These elements can be laterally repositioned to provide a 2×2 array for four semiconductor devices. In addition, the topography (lateral shape) can be adjusted for posts 20, pads 64, routing lines 66, caps 68 and terminals 70. Moreover, posts 20 can have separate posts 22 or share a single post 22 as defined by etch mask 62.
In this embodiment, the pad and the first cap are above the first adhesive and have the same thickness and the terminal and the second cap are below the second adhesive and have the same thickness. For purposes of brevity, any description of thermal board 90 is incorporated herein insofar as the same is applicable, and the same description need not be repeated Likewise, elements of the thermal board similar to those in thermal board 90 have corresponding reference numerals.
Thermal board 92 includes adhesives 26 and 28, conductive trace 74 and heat spreader 76. Conductive trace 74 includes plated through-hole 58, pad 64, routing line 66 and terminal 70. Heat spreader 76 includes posts 20 and 22, dielectric base 24 and caps 68 and 72.
Pad 64 and cap 68 contact and are located above adhesive 26. Pad 64 and cap 68 also have the same thickness. Thus, pad 64 and cap 68 have the same thickness not only where they are closest to one another but also where cap 68 is adjacent to post 20.
Terminal 70 and cap 72 contact and are located below adhesive 28. Terminal 70 and cap 72 also have the same thickness. Thus, terminal 70 and cap 72 have the same thickness not only where they are closest to one another but also where cap 72 is adjacent to post 22.
Thermal board 92 can be manufactured in a manner similar to thermal board 90 with suitable adjustments for pad 64, routing line 66, cap 68, terminal 70 and cap 72. For instance, metal plates 12 and 14 are 100 microns (rather than 200 microns) and posts 20 and 22 have a height of 100 microns (rather than 200 microns). Furthermore, adhesives 26 and 28 as prepregs have a thickness of 120 microns (rather than 100 microns).
Adhesive 28 is mounted on dielectric base 24, the structure is inverted and adhesive 26 is mounted on dielectric base 24. However, conductive layers 32 and 42 and dielectric layers 34 and 44 are omitted. Furthermore, posts 20 and 22 extend into but not through openings 26A and 28A.
Thereafter, heat and pressure are applied to flow and solidify adhesives 26 and 28. For instance, adhesives 26 and 28 can be disposed between top and bottom platens of a press. In addition, a top cull plate and top buffer paper can be sandwiched between adhesive 26 and the top platen, and a bottom cull plate and bottom buffer paper can be sandwiched between adhesive 28 and the bottom platen. The stack includes the top platen, top cull plate, top buffer paper, adhesive 26, dielectric base 24, adhesive 28, bottom buffer paper, bottom cull plate and bottom platen in descending order. Thus, adhesive 26 contacts and is sandwiched between dielectric base 24 and the top buffer paper and adhesive 28 contacts and is sandwiched between dielectric base 24 and the bottom buffer paper.
The platens are heated and move towards one another, thereby applying heat and pressure to adhesives 26 and 28. As the platen motion and heat continue, adhesive 26 between dielectric base 24 and the top platen is compressed, melted and flows into contact with post 20 and adhesive 28 between dielectric base 24 and the bottom platen is compressed, melted and flows into contact with post 22. Furthermore, adhesive 26 creates a thin coating on the top surface of post 20 and adhesive 28 creates a thin coating on the bottom surface of post 22. The platen motion is eventually blocked by posts 20 and 22 and the platens become stationary but continue to apply heat to solidify adhesives 26 and 28. Thereafter, the platens move away from one another and the structure is released from the press.
The top buffer paper provides a release sheet for adhesive 26 and the bottom buffer paper provides a release sheet for adhesive 28. As a result, the top buffer paper is easily peeled off from adhesive 26 without delaminating adhesive 26 and the bottom buffer paper is easily peeled off adhesive 28 without delaminating adhesive 28 after adhesives 26 and 28 are solidified. Moreover, adhesive 26 laminates only itself to post 20 and dielectric base 24 and adhesive 28 laminates only itself to post 22 and dielectric base 24.
Thereafter, grinding is applied to planarize the top and bottom surfaces, hole 50 is drilled through dielectric base 24 and adhesives 26 and 28 and then plated layers 54 and 56 and plated through-hole 58 are deposited on the structure. Thereafter, plated layer 54 alone is etched to form pad 64, routing line 66 and cap 68, plated layer 56 alone is etched to form terminal 70 and cap 72 and then plated contacts 78 provide a surface finish for pad 64, cap 68, terminal 70 and cap 72. Thereafter, dielectric base 24 and adhesives 26 and 28 are cut or cracked at the peripheral edges of thermal board 92 to detach it from the batch.
In this embodiment, the substrates are provided by the conductive layers alone and the dielectric layers is omitted. For purposes of brevity, any description of thermal board 90 is incorporated herein insofar as the same is applicable, and the same description need not be repeated Likewise, elements of the thermal board similar to those in thermal board 90 have corresponding reference numerals.
Thermal board 94 includes adhesives 26 and 28, conductive trace 74 and heat spreader 76. Conductive trace 74 includes plated through-hole 58, pad 64, routing line 66 and terminal 70. Heat spreader 76 includes posts 20 and 22, dielectric base 24 and caps 68 and 72.
Conductive layers 32 and 42 are thicker in this embodiment than the previous embodiment so that they can be handled without warping or wobbling. Pad 64, routing line 66, cap 68, terminal 70 and cap 72 are therefore thicker. In addition, dielectric layers 34 and 44 are omitted. As a result, adhesive 26 contacts and is sandwiched between dielectric base 24 and pad 64 and between dielectric base 24 and routing line 66 and adhesive 28 contacts and is sandwiched between dielectric base 24 and terminal 70. Furthermore, adhesive 26 is thicker to accommodate the absence of dielectric layer 34 and adhesive 28 is thicker to accommodate the absence of dielectric layer 44.
Thermal board 94 can be manufactured in a manner similar to thermal board 90 with suitable adjustments for adhesives 26 and 28 and conductive layers 32 and 42. For instance, adhesive 28 with a thickness of 150 microns (rather than 100 microns) is mounted on dielectric base 24, conductive layer 42 alone with a thickness of 80 microns (rather than 30 microns) is mounted on adhesive 28, the structure is inverted, adhesive 26 with a thickness of 150 microns (rather than 100 microns) is mounted on dielectric base 24 and conductive layer 32 alone with a thickness of 80 microns (rather than 30 microns) is mounted on adhesive 26. As a result, adhesive 26 contacts and is sandwiched between dielectric base 24 and conductive layer 32 and adhesive 28 contacts and is sandwiched between dielectric base 24 and conductive layer 42.
Thereafter, heat and pressure are applied to flow and solidify adhesives 26 and 28, grinding is applied to planarize the top and bottom surfaces, hole 50 is drilled through dielectric base 24, adhesives 26 and 28 and conductive layers 32 and 42 and then plated layers 54 and 56 and plated through-hole 58 are deposited on the structure. Thereafter, conductive layer 32 and plated layer 54 are etched to form pad 64, routing line 66 and cap 68, conductive layer 42 and plated layer 56 are etched to form terminal 70 and cap 72 and then plated contacts 78 provide a surface finish for pad 64, cap 68, terminal 70 and cap 72. Thereafter, dielectric base 24 and adhesives 26 and 28 are cut or cracked at the peripheral edges of thermal board 94 to detach it from the batch.
In this embodiment, first and second solder masks selectively expose the conductive trace and the heat spreader. For purposes of brevity, any description of thermal board 90 is incorporated herein insofar as the same is applicable, and the same description need not be repeated Likewise, elements of the thermal board similar to those in thermal board 90 have corresponding reference numerals.
Thermal board 96 includes adhesives 26 and 28, substrates 30 and 40, conductive trace 74, heat spreader 76 and solder masks 80 and 82. Substrate 30 includes dielectric layer 34. Substrate 40 includes dielectric layer 44. Conductive trace 74 includes plated through-hole 58, pad 64, routing line 66 and terminal 70. Heat spreader 76 includes posts 20 and 22, dielectric base 24 and caps 68 and 72.
Solder mask 80 is an electrically insulative layer that selectively exposes pad 64 and cap 68 in the upward direction and covers dielectric layer 34 where it is otherwise exposed in the upward direction, and solder mask 82 is an electrically insulative layer that selectively exposes terminal 70 and cap 72 in the downward direction and covers dielectric layer 44 where it is otherwise exposed in the downward direction.
Thermal board 96 can be manufactured in a manner similar to thermal board 90 with suitable adjustments for solder masks 80 and 82. For instance, adhesive 28 is mounted on dielectric base 24, substrate 40 is mounted on adhesive 28, the structure is inverted, adhesive 26 is mounted on dielectric base 24 and substrate 30 is mounted on adhesive 26. Thereafter, heat and pressure are applied to flow and solidify adhesives 26 and 28, grinding is applied to planarize the top and bottom surfaces, hole 50 is drilled through dielectric base 24, adhesives 26 and 28, conductive layers 32 and 42 and dielectric layers 34 and 44 and then plated layers 54 and 56 and plated through-hole 58 are deposited on the structure. Thereafter, conductive layer 32 and plated layer 54 are etched to form pad 64, routing line 66 and cap 68 and conductive layer 42 and plated layer 56 are etched to form terminal 70 and cap 72.
Thereafter, solder mask 80 is formed on the top surface and solder mask 82 is formed on the bottom surface. Solder masks 80 and 82 are initially a photoimageable liquid resin that is dispensed on the top and bottom surfaces, respectively. Thereafter, solder masks 80 and 82 are patterned by selectively applying light through reticles (not shown) so that the solder mask portions exposed to the light are rendered insoluble, applying a developer solution to remove the solder mask portions that are unexposed to the light and remain soluble and then hard baking, as is conventional.
Thereafter, plated contacts 78 provide a surface finish for pad 64, cap 68, terminal 70 and cap 72 and then dielectric base 24, adhesives 26 and 28, dielectric layers 34 and 44 and solder masks 80 and 82 are cut or cracked at the peripheral edges of thermal board 96 to detach it from the batch.
In this embodiment, the first cap is electrically connected to a second terminal. For purposes of brevity, any description of thermal board 90 is incorporated herein insofar as the same is applicable, and the same description need not be repeated Likewise, elements of the thermal board similar to those in thermal board 90 have corresponding reference numerals.
Thermal board 98 includes adhesives 26 and 28, substrates 30 and 40, conductive traces 74 and 75 and heat spreader 76. Substrate 30 includes dielectric layer 34. Substrate 40 includes dielectric layer 44. Conductive trace 74 includes plated through-hole 58, pad 64, routing line 66 and terminal 70. Conductive trace 75 includes plated through-hole 59, routing line 67, cap 68 and terminal 71. Heat spreader 76 includes posts 20 and 22, dielectric base 24 and caps 68 and 72.
Cap 68 provides an electrical contact (similar to pad 64) for conductive trace 75 as well as a thermal contact for heat spreader 76. Cap 68 is electrically connected to plated through-hole 59 by routing line 67 and thereby electrically connected to terminal 71. Thus, conductive trace 75 and heat spreader 76 share cap 68 and are integral with one another and heat spreader 76 has both a thermal and electrical function.
Plated through-holes 58 and 59 are identical. As a result, plated through-hole 59 contacts and extends through dielectric base 24, adhesives 26 and 28 and dielectric layers 34 and 44 in hole 51.
Terminals 70 and 71 are identical. As a result, terminals 70 and 71 have the same thickness and are coplanar with one another below adhesive 28 and dielectric layer 44 at a bottom surface that faces in the downward direction. Likewise, terminal 71 and cap 72 have the same thickness where they are closest to one another, have different thickness where cap 72 is adjacent to post 22 and are coplanar with one another below adhesive 28 and dielectric layer 44 at a bottom surface that faces in the downward direction.
Posts 20 and 22 are electrically isolated from one another, caps 68 and 72 are electrically isolated from one another and terminals 70 and 71 and cap 72 are electrically isolated from one another.
Thermal board 98 can be manufactured in a manner similar to thermal board 90 with suitable adjustments for routing line 67. For instance, adhesive 28 is mounted on dielectric base 24, substrate 40 is mounted on adhesive 28, the structure is inverted, adhesive 26 is mounted on dielectric base 24 and substrate 30 is mounted on adhesive 26. Thereafter, heat and pressure are applied to flow and solidify adhesives 26 and 28, grinding is applied to planarize the top and bottom surfaces, holes 50 and 51 are drilled through dielectric base 24, adhesives 26 and 28, conductive layers 32 and 42 and dielectric layers 34 and 44 and then plated layers 54 and 56 and plated through-holes 58 and 59 are deposited on the structure. Thereafter, conductive layer 32 and plated layer 54 are etched to form pad 64, routing lines 66 and 67 and cap 68 as defined by etch mask 60, conductive layer 42 and plated layer 56 are etched to form terminals 70 and 71 and cap 72 as defined by etch mask 62 and then plated contacts 78 provide a surface finish for pad 64, cap 68, terminals 70 and 71 and cap 72. Thereafter, dielectric base 24, adhesives 26 and 28 and dielectric layers 34 and 44 are cut or cracked at the peripheral edges of thermal board 98 to detach it from the batch.
In this embodiment, the semiconductor device is an LED chip that emits blue light, is mounted on the first cap, is electrically connected to the pad using a wire bond and is thermally connected to the first cap using a die attach. The semiconductor device is covered by a color-shifting encapsulant that converts the blue light to white light.
Semiconductor chip assembly 100 includes thermal board 90, LED chip 102, wire bond 104, die attach 106 and encapsulant 108. LED chip 102 includes top surface 110, bottom surface 112 and bond pad 114. Top surface 110 is the active surface and includes bond pad 114 and bottom surface 112 is a thermal contact surface.
LED chip 102 is mounted on heat spreader 76, electrically connected to conductive trace 74 and thermally connected to heat spreader 76. In particular, LED chip 102 is mounted on cap 68 (and thus post 20), extends above adhesive 26 and cap 68, overlaps (and thus extends laterally within the peripheries of) posts 20 and 22, dielectric base 24 and caps 68 and 72 but does not overlap (and thus is outside the periphery of) conductive trace 74, is located within the peripheries of and covered in the downward direction by post 22, dielectric base 24 and caps 68 and 72 and is located outside the periphery of conductive trace 74. LED chip 102 is electrically connected to pad 64 by wire bond 104 and is thermally connected to and mechanically attached to cap 68 by die attach 106.
Wire bond 104 is bonded to and electrically connects pads 64 and 114, thereby electrically connecting LED chip 102 to routing line 66, thereby electrically connecting LED chip 102 to plated through-hole 58 and thereby electrically connecting LED chip 102 to terminal 70. Die attach 106 contacts and is sandwiched between and thermally connects and mechanically attaches cap 68 and thermal contact surface 112, thereby thermally connecting LED chip 102 to post 20, thereby thermally connecting LED chip 102 to dielectric base 24, thereby thermally connecting LED chip 102 to post 22 and thereby thermally connecting LED chip 102 to cap 72. However, LED chip 102 is electrically isolated from post 22 and cap 72 regardless of whether LED chip 102 is electrically connected to or electrically isolated from post 20 and cap 68. Moreover, post 22 and cap 72 have no electrical function and electrically float during the operation of LED chip 102.
Encapsulant 108 is a solid adherent electrically insulative color-shifting protective enclosure that provides environmental protection such as moisture resistance and particle protection for LED chip 102 and wire bond 104. Encapsulant 108 contacts dielectric layer 34, pad 64, routing line 66, cap 68, LED chip 102, wire bond 104 and die attach 106, is spaced from posts 20 and 22, dielectric base 24, adhesives 26 and 28, dielectric layer 44, plated through-hole 58, terminal 70 and cap 72 and cover post 20, pad 64, cap 68, LED chip 102, wire bond 104 and die attach 106 in the upward direction. Encapsulant 108 is transparent for convenience of illustration.
Pad 64 is spot plated with nickel/silver to bond well with wire bond 104, thereby improving signal transfer from conductive trace 74 to LED chip 102, and cap 68 is spot plated with nickel/silver to bond well with die attach 106, thereby improving heat transfer from LED chip 102 to heat spreader 76. Cap 68 also provides a highly reflective surface which reflects the light emitted towards the silver surface layer by LED chip 102, thereby increasing light output in the upward direction. Furthermore, since cap 68 is shaped and sized to accommodate thermal contact surface 112, post 20 is not and need not be shaped and sized to accommodate thermal contact 112.
LED chip 102 includes a compound semiconductor that emits blue light, has high luminous efficiency and forms a p-n junction. Suitable compound semiconductors include gallium-nitride, gallium-arsenide, gallium-phosphide, gallium-arsenic-phosphide, gallium-aluminum-phosphide, gallium-aluminum-arsenide, indium-phosphide and indium-gallium-phosphide. LED chip 102 also has high light output and generates considerable heat.
Encapsulant 108 includes transparent silicone and yellow phosphor. For instance, the silicone can be polysiloxane resin and the yellow phosphor can be cerium-doped yttrium-aluminum-garnet (Ce:YAG) fluorescent powder. The yellow phosphor emits yellow light in response to blue light, and the blue and yellow light mix to produce white light. As a result, encapsulant 108 converts the blue light emitted by LED chip 102 into white light and assembly 100 is a white light source. In addition, encapsulant 108 has a hemisphere dome shape which provides a convex refractive surface that focuses the white light in the upward direction.
Semiconductor chip assembly 100 can be manufactured by mounting LED chip 102 on cap 68 using die attach 106, then wire bonding pads 64 and 114 and then forming encapsulant 108.
For instance, die attach 106 is initially a silver-filled epoxy paste with high thermal conductivity that is selectively screen printed on cap 68 and then LED chip 102 placed on the epoxy paste using a pick-up head and an automated pattern recognition system in step-and-repeat fashion. Thereafter, the epoxy paste is heated and hardened at a relatively low temperature such as 190° C. to form die attach 106. Next, wire bond 104 is a gold wire that is thermosonically ball bonded to pads 64 and 114 and then encapsulant 108 is molded on the structure.
LED chip 102 can be electrically connected to pad 64 by a wide variety of connection media, thermally connected to and mechanically attached to heat spreader 76 by a wide variety of thermal adhesives and encapsulated by a wide variety of encapsulants.
Semiconductor chip assembly 100 is a first-level single-chip package.
In this embodiment, the semiconductor device has a thermal/electrical contact surface that is electrically and thermally connected to the first cap and the first cap is electrically connected to a second terminal. For purposes of brevity, any description of assembly 100 is incorporated herein insofar as the same is applicable, and the same description need not be repeated Likewise, elements of the assembly similar to those in assembly 100 have corresponding reference numerals indexed at two-hundred rather than one-hundred. For instance, LED chip 202 corresponds to LED chip 102, wire bond 204 corresponds to wire bond 104, etc.
Semiconductor chip assembly 200 includes thermal board 98, LED chip 202, wire bond 204, die attach 206 and encapsulant 208. LED chip 202 includes top surface 210 and bottom surface 212. Top surface 210 includes bond pad 214 and bottom surface 212 is a thermal/electrical contact surface. Thus, LED chip 202 is a vertical chip with bond pad 214 as a frontside electrical contact and thermal/electrical contact surface 212 as a backside electrical contact.
LED chip 202 is mounted on heat spreader 76, electrically connected to conductive trace 74 and thermally connected to heat spreader 76. In particular, LED chip 202 is mounted on cap 68, overlaps posts 20 and 22, dielectric base 24 and caps 68 and 72, is electrically connected to pad 64 by wire bond 204 and is electrically and thermally connected to and mechanically attached to cap 68 by die attach 206.
Wire bond 204 is bonded to and electrically connects pads 64 and 214, thereby electrically connecting LED chip 202 to terminal 70. Die attach 206 contacts and is sandwiched between and electrically and thermally connects and mechanically attaches cap 68 and thermal/electrical contact surface 212, thereby electrically connecting LED chip 202 to terminal 71 and thermally connecting LED chip 202 to cap 72. However, LED chip 202 is electrically isolated from cap 72 which has no electrical function and electrically floats during the operation of LED chip 202.
Semiconductor chip assembly 200 can be manufactured by mounting LED chip 202 on cap 68 using die attach 206, then wire bonding pads 64 and 214 and then forming encapsulant 208.
For instance, die attach 206 is a gold-tin eutectic with high thermal and electrical conductivity that contacts and is sandwiched between and electrically and thermally connects and mechanically attaches cap 68 and thermal/electrical contact surface 212. Next, wire bond 204 is bonded to pads 64 and 214 and then encapsulant 208 is molded on the structure.
Semiconductor chip assembly 200 is a first-level single-chip package.
The semiconductor chip assemblies and thermal boards described above are merely exemplary. Numerous other embodiments are contemplated. In addition, the embodiments described above can be mixed-and-matched with one another and with other embodiments depending on design and reliability considerations. For instance, the thermal board can include single-level conductive traces and multi-level conductive traces. The thermal board can also include multiple first posts arranged in an array for multiple semiconductor devices and additional conductive traces to accommodate the additional semiconductor devices. The thermal board can also include the solder masks and exclude the dielectric layers. The thermal board can also include the thermal/electrical heat spreader and exclude the dielectric layers. The thermal board can also include the solder masks and the thermal/electrical heat spreader. The semiconductor device can be covered in the first vertical direction by a transparent, translucent or opaque encapsulant and/or a transparent, translucent or opaque lid. For instance, the semiconductor device can be an LED chip that emits blue light and is covered by a transparent encapsulant or lid so that the assembly is a blue light source or a color-shifting encapsulant or lid so that the assembly is a green, red or white light source. Likewise, the semiconductor device can be an LED package with multiple LED chips and the thermal board can include additional conductive traces to accommodate the additional LED chips.
The semiconductor device can share or not share the heat spreader with other semiconductor devices. For instance, a single semiconductor device can be mounted on the heat spreader. Alternatively, numerous semiconductor devices can mounted on the heat spreader. For instance, four small chips in a 2×2 array can be attached to the first post and the thermal board can include additional conductive traces to receive and route additional wire bonds to the chips. This may be more cost effective than providing a miniature first post for each chip.
The semiconductor chip can be optical or non-optical. For instance, the chip can be an LED, an IR detector, a solar cell, a microprocessor, a controller, a DRAM or an RF power amplifier. Likewise, the semiconductor package can be an LED package or an RF module. Thus, the semiconductor device can be a packaged or unpackaged optical or non-optical chip. Furthermore, the semiconductor device can be mechanically, electrically and thermally connected to the thermal board using a wide variety of connection media including solder and electrically and/or thermally conductive adhesive.
The heat spreader can provide rapid, efficient and essentially uniform heat spreading and dissipation for the semiconductor device to the next level assembly without heat flow through the adhesives or the dielectric layers. As a result, the adhesives can have low thermal conductivity which drastically reduces cost. The heat spreader can include a first cap that is metallurgically bonded and thermally connected to the first post and a second cap that is metallurgically bonded and thermally connected to the second post, thereby enhancing reliability and reducing cost. Furthermore, the first cap can be customized for the semiconductor device and the second cap can be customized for the next level assembly, thereby enhancing the thermal connection from the semiconductor device to the next level assembly. For instance, the first cap can have a square or rectangular shape in a lateral plane with the same or similar topography as the thermal contact of the semiconductor device, the second cap can have a square or rectangular shape in a lateral plane with the same or similar topography as a heat sink and the posts can have a circular shapes. In any case, the heat spreader can be a wide variety of thermally conductive structures.
The first post can include a flat top surface that is coplanar with the first adhesive. For instance, the first post can be coplanar with the first adhesive or the first post can be etched after the first adhesive is solidified to provide a cavity in the first adhesive over the first post. The first post can also be selectively etched to provide a cavity in the first post. In any case, the semiconductor device can be mounted on the first post and located in the cavity, and the wire bond can extend from the semiconductor device in the cavity to the pad outside the cavity. In this instance, the semiconductor device can be an LED chip and the cavity can focus the LED light in the first vertical direction.
The dielectric base can provide mechanical support for the conductive trace, the adhesives and the substrates. For instance, the dielectric base can prevent the substrates from warping during metal grinding, chip mounting, wire bonding and encapsulant molding.
The caps can be formed by numerous deposition techniques including electroplating, electroless plating, evaporating and sputtering as a single layer or multiple layers after the adhesives are solidified. The caps can be the same metal as the posts or the surfaces of the posts. Furthermore, the caps can include or be spaced from the conductive layers. For instance, the first cap can extend across the first aperture to the first substrate or reside within the periphery of the first aperture. Thus, the first cap may contact or be spaced from the first substrate. Likewise, the second cap can extend across the second aperture to the second substrate or reside within the periphery of the second aperture. Thus, the second cap may contact or be spaced from the second substrate. In any case, the first cap extends from the first post in the first vertical and lateral directions, the second cap extends from the second post in the second vertical and lateral directions and the caps are thermally connected to one another.
The adhesives can provide a robust mechanical bond between the heat spreader and the conductive trace and between the heat spreader and the substrates. For instance, the adhesives can extend laterally from the respective posts beyond the conductive trace to the peripheral edges of the assembly. The adhesives can also fill the respective gaps between the posts and the dielectric layers. The adhesives can also be void-free with consistent bond lines. The adhesives can also absorb thermal expansion mismatch between the heat spreader and the conductive trace. The adhesives can also be the same material as or a different material than the dielectric layers. Furthermore, the adhesives can be a low cost dielectric that need not have high thermal conductivity. Moreover, the adhesives are not prone to delamination.
The adhesives thickness can be adjusted so that the adhesives essentially fill the respective gaps and the adhesives are within structure once they are solidified and/or grinded. For instance, the optimal prepreg thickness can be established through trial and error Likewise, the dielectric layer thickness can be adjusted to achieve this result.
The first conductive layer alone can be mounted on the first adhesive. For instance, the first aperture can be formed in the first conductive layer and then the first conductive layer can be mounted on the first adhesive so that the first conductive layer contacts the first adhesive and is exposed in the first vertical direction and the first post extends into and is exposed in the first vertical direction by the first aperture. In this instance, the first conductive layer can have a thickness of 80 to 150 microns which is thick enough to handle without warping and wobbling yet thin enough to pattern without excessive etching.
The second conductive layer alone can be mounted on the second adhesive. For instance, the second aperture can be formed in the second conductive layer and then the second conductive layer can be mounted on the second adhesive so that the second conductive layer contacts the second adhesive and is exposed in the second vertical direction and the second post extends into and is exposed in the second vertical direction by the second aperture. In this instance, the second conductive layer can have a thickness of 80 to 150 microns which is thick enough to handle without warping and wobbling yet thin enough to pattern without excessive etching.
The first conductive layer and the first dielectric layer can be mounted on the first adhesive. For instance, the first conductive layer can be provided on the first dielectric layer, then the first aperture can be formed in the first conductive layer and the first dielectric layer, and then the first conductive layer and the first dielectric layer can be mounted on the first adhesive so that the first conductive layer is exposed in the first vertical direction, the first dielectric layer contacts and is sandwiched between and separates the first conductive layer and the first adhesive and the first post extends into and is exposed in the first vertical direction by the first aperture. In this instance, the first conductive layer can have a thickness of 10 to 50 microns such as 30 microns which is thick enough for reliable signal transfer yet thin enough to reduce weight and cost. Furthermore, the first dielectric layer is a permanent part of the thermal board.
The second conductive layer and the second dielectric layer can be mounted on the second adhesive. For instance, the second conductive layer can be provided on the second dielectric layer, then the second aperture can be formed in the second conductive layer and the second dielectric layer, and then the second conductive layer and the second dielectric layer can be mounted on the second adhesive so that the second conductive layer is exposed in the second vertical direction, the second dielectric layer contacts and is sandwiched between and separates the second conductive layer and the second adhesive and the second post extends into and is exposed in the second vertical direction by the second aperture. In this instance, the second conductive layer can have a thickness of 10 to 50 microns such as 30 microns which is thick enough for reliable signal transfer yet thin enough to reduce weight and cost. Furthermore, the second dielectric layer is a permanent part of the thermal board.
The first conductive layer and a first carrier can be mounted on the first adhesive. For instance, the first conductive layer can be attached to a first carrier such biaxially-oriented polyethylene terephthalate polyester (Mylar) by a thin film, then the first aperture can be formed in the first conductive layer but not the first carrier, then the first conductive layer and the first carrier can be mounted on the first adhesive so that the first carrier covers the first conductive layer and is exposed in the first vertical direction, the thin film contacts and is sandwiched between the first carrier and the first conductive layer, the first conductive layer contacts and is sandwiched between the thin film and the first adhesive, and the first post is aligned with the first aperture and covered in the first vertical direction by the first carrier. After the first adhesive is solidified, the thin film can be decomposed by UV light so that the first carrier can be peeled off the first conductive layer, thereby exposing the first conductive layer in the first vertical direction, and then the first conductive layer can be grinded and patterned for the pad and the first cap. In this instance, the first conductive layer can have a thickness of 10 to 50 microns such as 30 microns which is thick enough for reliable signal transfer yet thin enough to reduce weight and cost, and the first carrier can have a thickness of 300 to 500 microns which is thick enough to handle without warping and wobbling yet thin enough to reduce weight and cost. Furthermore, the first carrier is a temporary fixture and not a permanent part of the thermal board.
The second conductive layer and a second carrier can be mounted on the second adhesive in a similar manner.
The first substrate with the first conductive layer and the first dielectric layer can be a low cost laminated structure that need not have high thermal conductivity. The first substrate can include a single conductive layer or multiple conductive layers. Furthermore, the first substrate can be other electrical interconnects such as a ceramic board or a printed circuit board and can include additional layers of embedded circuitry.
The second substrate with the second conductive layer and the second dielectric layer can be a low cost laminated structure that need not have high thermal conductivity. The second substrate can include a single conductive layer or multiple conductive layers. Furthermore, the second substrate can be other electrical interconnects such as a ceramic board or a printed circuit board and can include additional layers of embedded circuitry.
The pad and the first cap can be coplanar at a first surface that faces in the first vertical direction, thereby facilitating the electrical, thermal and mechanical connections between the thermal board and the semiconductor device Likewise, the terminal and the second cap can be coplanar at a second surface that faces in the second vertical direction, thereby facilitating the electrical, thermal and mechanical connections between the thermal board and the next level assembly.
The pad and the terminal can have a wide variety of packaging formats as required by the semiconductor device and the next level assembly.
The pad and the terminal can be formed by numerous deposition techniques including electroplating, electroless plating, evaporating and sputtering as a single layer or multiple layers, either before or after the conductive layers are mounted on the adhesives. For instance, the first conductive layer can be patterned on a first substrate to provide the pad before it is mounted on the first adhesive or after it is attached to the first post and the dielectric base by the first adhesive. Likewise, the second conductive layer can be patterned on a second substrate to provide the terminal before it is mounted on the second adhesive or after it is attached to the second post and the dielectric base by the second adhesive.
The plated contact surface finish can be formed before or after the pad and the terminal are formed. For instance, the plated contacts can be deposited on the conductive layers before or after they are etched to form the pad, the terminal and the caps. Furthermore, the plated contacts can occupy 85 to 95 percent of a first surface that faces in the first vertical direction and thus provide a highly reflective surface which is particularly useful if an LED device is subsequently mounted on the first cap and the solder masks are omitted.
The encapsulant can be numerous transparent, translucent or opaque materials and have various shapes and sizes. For instance, the encapsulant can be transparent silicone, epoxy or combinations thereof. Silicone has higher thermal and color-shifting stability than epoxy but also higher cost and lower rigidity and adhesion than epoxy.
A lid can cover or replace the encapsulant. The lid can provide environmental protection such as moisture resistance and particle protection for the chip and the wire bond in a sealed enclosure. The lid can be numerous transparent, translucent or opaque materials and have various shapes and sizes. For instance, the lid can be transparent glass or silica.
A lens can cover or replace the encapsulant. The lens can provide environmental protection such as moisture resistance and particle protection for the chip and the wire bond in a sealed enclosure. The lens can also provide a convex refractive surface that focuses the light in the first vertical direction. The lens can be numerous transparent, translucent or opaque materials and have various shapes and sizes. For instance, a glass lens with a hollow hemisphere dome can be mounted on the thermal board and spaced from the encapsulant, or a plastic lens with a solid hemisphere dome can be mounted on the encapsulant and spaced from the thermal board.
A rim can laterally surround the semiconductor device and the first cap and extend beyond the semiconductor device and the first cap in the first vertical direction. The rim can be reflective or non-reflective and transparent or non-transparent. For instance, the rim can include a highly reflective metal such as silver or aluminum with a slanted inner surface which reflects the light directed at it in the first vertical direction, thereby increasing light output in the first vertical direction Likewise, the rim can include a transparent material such as glass or a non-reflective, non-transparent low cost material such as epoxy. Furthermore, a reflective rim can be used regardless of whether it contacts or confines the encapsulant, and a lid or a lens can be mounted on the rim.
The conductive trace can include additional pads, terminals, plated through-holes, routing lines and vias as well as passive components and have different configurations. The conductive trace can function as a signal, power or ground layer depending on the purpose of the corresponding semiconductor device pad. The conductive trace can also include various conductive metals such as copper, gold, nickel, silver, palladium, tin, combinations thereof, and alloys thereof. The preferred composition will depend on the nature of the external connection media as well as design and reliability considerations. Furthermore, those skilled in the art will understand that in the context of a semiconductor chip assembly, the copper material can be pure elemental copper but is typically a copper alloy that is mostly copper such as copper-zirconium (99.9% copper), copper-silver-phosphorus-magnesium (99.7% copper) and copper-tin-iron-phosphorus (99.7% copper) to improve mechanical properties such as tensile strength and elongation.
The caps, conductive layers, plated layers, routing lines, plated through-holes, plated contacts, dielectric layers, solder masks and encapsulant are generally desirable but may be omitted in some embodiments. For instance, if the openings and the apertures are punched rather than drilled so that the first post is shaped and sized to accommodate a thermal contact surface of the semiconductor device and the second post is shaped and sized to accommodate a heat sink then the caps can be omitted. Likewise, if thick conductive layers are used then the dielectric layers can be omitted.
The thermal board can include a thermal via that is spaced from the posts, extends through the dielectric base, the adhesives and the dielectric layers outside the openings and the apertures and is adjacent to and thermally connects the caps to improve heat dissipation from the first cap to the second cap and heat spreading in the second cap.
The assembly can provide horizontal or vertical single-level or multi-level signal routing.
Horizontal single-level signal routing with the pad, the terminal and the routing line above the dielectric layer is disclosed in U.S. application Ser. No. 12/616,773 filed Nov. 11, 2009 by Charles W. C. Lin et al. entitled “Semiconductor Chip Assembly with Post/Base Heat Spreader and Substrate” which is incorporated by reference.
Horizontal single-level signal routing with the pad, the terminal and the routing line above the adhesive and no dielectric layer is disclosed in U.S. application Ser. No. 12/616,775 filed Nov. 11, 2009 by Charles W. C. Lin et al. entitled “Semiconductor Chip Assembly with Post/Base Heat Spreader and Conductive Trace” which is incorporated by reference.
Horizontal multi-level signal routing with the pad and the terminal above the dielectric layer electrically connected by first and second vias through the dielectric layer and a routing line beneath the dielectric layer is disclosed in U.S. application Ser. No. 12/557,540 filed Sep. 11, 2009 by Chia-Chung Wang et al. entitled “Semiconductor Chip Assembly with Post/Base Heat Spreader and Horizontal Signal Routing” which is incorporated by reference.
Vertical multi-level signal routing with the pad above the dielectric layer and the terminal beneath the adhesive electrically connected by a first via through the dielectric layer, a routing line beneath the dielectric layer and a second via through the adhesive is disclosed in U.S. application Ser. No. 12/557,541 filed Sep. 11, 2009 by Chia-Chung Wang et al. entitled “Semiconductor Chip Assembly with Post/Base Heat Spreader and Vertical Signal Routing” which is incorporated by reference.
The working format for the thermal board can be a single thermal board or multiple thermal boards based on the manufacturing design. For instance, a single thermal board can be manufactured individually. Alternatively, numerous thermal boards can be simultaneously batch manufactured using a single first metal plate, a single second metal plate, a single dielectric base, a single first adhesive, a single second adhesive, a single first conductive layer, a single second conductive layer, a single first dielectric layer, a single second dielectric layer and a single plated metal and then separated from one another Likewise, numerous sets of heat spreaders and conductive traces that are each dedicated to a single semiconductor device can be simultaneously batch manufactured for each thermal board in the batch using a single first metal plate, a single second metal plate, a single dielectric base, a single first adhesive, a single second adhesive, a single first conductive layer, a single second conductive layer, a single first dielectric layer, a single second dielectric layer and a single plated metal.
For example, the metal plates can be attached to one another by the dielectric base, then the metal plates can be etched to form multiple first posts and multiple second posts, then the non-solidified second adhesive with second openings corresponding to the second posts can be mounted on the dielectric base such that each second post extends through a second opening, then the second substrate with the second conductive layer, the second dielectric layer and second apertures corresponding to the second posts can be mounted on the second adhesive such that each second post extends through a second opening into a second aperture, then the structure can be inverted, then the non-solidified first adhesive with first openings corresponding to the first posts can be mounted on the dielectric base such that each first post extends through a first opening, then the first substrate with the first conductive layer, the first dielectric layer and first apertures corresponding to the first posts can be mounted on the first adhesive such that each first post extends through a first opening into a first aperture, then the substrates can be moved towards the dielectric base by platens to force the first adhesive into the first gaps and the second adhesive into the second gaps, then the adhesives can be cured and solidified, then the posts, the adhesives and the conductive layers can be grinded to provide the first and second opposing planar lateral surfaces, then the holes can be drilled through the dielectric base, the adhesives, the conductive layers and the dielectric layers, then the plated metal can be plated on the structure to form the plated layers on the posts, the adhesives and the conductive layers and the plated through-holes in the holes, then the first conductive layer and the first plated layer can be etched to form the first caps corresponding to the first posts and the pads and the routing lines corresponding to the plated through-holes, the second conductive layer and the second plated layer can be etched to form the second caps corresponding to the second posts and the terminals corresponding to the plated through-holes, then the plated contact surface finish can be formed on the pads, the terminals and the caps and then the dielectric base, the adhesives and the dielectric layers can be cut or cracked at the desired locations of the peripheral edges of the thermal boards, thereby separating the individual thermal boards from one another.
The working format for the semiconductor chip assembly can be a single assembly or multiple assemblies based on the manufacturing design. For instance, a single assembly can be manufactured individually. Alternatively, numerous assemblies can be simultaneously batch manufactured before the thermal boards are separated from one another. Likewise, multiple semiconductor devices can be electrically, thermally and mechanically connected to each thermal board in the batch.
For example, solder paste portions can be deposited on the pads and the first caps, then LED packages can be placed on the solder paste portions, then the solder paste portions can be simultaneously heated, reflowed and hardened to provide the solder joints and then the thermal boards can be separated from one another.
As another example, die attach paste portions can be deposited on the first caps, then chips can be placed on the die attach paste portions, then the die attach paste portions can be simultaneously heated and hardened to provide the die attaches, then the chips can be wired bonded to the corresponding pads, then the encapsulants can be formed over the chips and the wire bonds and then the thermal boards can be separated from one another.
The thermal boards can be detached from one another in a single step or multiple steps. For instance, the thermal boards can be batch manufactured as a panel, then the semiconductor devices can be mounted on the panel and then the semiconductor chip assemblies of the panel can be detached from one another. Alternatively, the thermal boards can be batch manufactured as a panel, then the thermal boards of the panel can be singulated into strips of multiple thermal boards, then the semiconductor devices can be mounted on the thermal boards of a strip and then the semiconductor chip assemblies of the strip can be detached from one another. Furthermore, the thermal boards can be detached by mechanical sawing, laser sawing, cleaving or other suitable techniques.
The term “adjacent” refers to elements that are integral (single-piece) or in contact (not spaced or separated from) with one another. For instance, the posts are adjacent to the dielectric base regardless of whether the posts are formed additively or subtractively.
The term “overlap” refers to above and extending within a periphery of an underlying element. Overlap includes extending inside and outside the periphery or residing within the periphery. For instance, when the first post protrudes upward from the dielectric base and the second post protrudes downward from the dielectric base, the semiconductor device overlaps the posts since an imaginary vertical line intersects the semiconductor device and the posts, regardless of whether another element such as the first cap or the die attach is between the semiconductor device and the posts and is intersected by the line, and regardless of whether another imaginary vertical line intersects the posts but not the semiconductor device (outside the periphery of the semiconductor device). Likewise, the first adhesive overlaps the dielectric base and is overlapped by the pad, the first post overlaps and is within a periphery of the dielectric base and the dielectric base is overlapped by the first post. Moreover, overlap is synonymous with over and overlapped by is synonymous with under or beneath.
The term “contact” refers to direct contact. For instance, the dielectric base contacts the posts but does not contact the pad.
The term “cover” refers to complete coverage in the vertical and/or lateral directions. For instance, the dielectric base covers the first post in the second vertical direction but the first post does not cover the dielectric base in the first vertical direction and the dielectric base covers the second post in the first vertical direction but the second post does not cover the dielectric base in the second vertical direction.
The term “layer” refers to patterned and unpatterned layers. For instance, the conductive layers can be unpatterned blanket sheets when the adhesives are flowed and solidified, and the conductive layers can be patterned circuits with spaced traces when the semiconductor device is mounted on the heat spreader. Furthermore, a layer can include stacked layers.
The term “surface area” refers to a lateral region in a lateral plane that is parallel to the lateral directions and orthogonal to the vertical directions. Furthermore, the surface area of an element is defined by the periphery of the element. For instance, the surface area of the first post is a lateral region defined by the periphery of the first post and is orthogonal to the vertical directions and the surface area of the second post is a lateral region defined by the periphery of the second post and is orthogonal to the vertical directions.
The term “pad” in conjunction with the conductive trace refers to a connection region that is adapted to contact and/or bond to external connection media (such as solder or a wire bond) that electrically connects the conductive trace to the semiconductor device.
The term “terminal” in conjunction with the conductive trace refers to a connection region that is adapted to contact and/or bond to external connection media (such as solder or a wire bond) that electrically connects the conductive trace to an external device (such as a PCB or a wire thereto) associated with the next level assembly.
The term “plated through-hole” in conjunction with the conductive trace refers to an electrical interconnect that is formed in a hole using plating. For instance, the plated through-hole exists regardless of whether it remains intact in the hole and spaced from peripheral edges of the assembly or is subsequently split or trimmed such that the hole is converted into a groove and the remaining portion is in the groove at a peripheral edge of the assembly.
The term “first cap” in conjunction with the heat spreader refers to a contact region that is adapted to contact and/or bond to external connection media (such as solder or thermally conductive adhesive) that thermally connects the heat spreader to the semiconductor device.
The term “second cap” in conjunction with the heat spreader refers to a contact region that is adapted to contact and/or bond to external connection media (such as solder or thermally conductive adhesive) that thermally connects the heat spreader to an external device (such as a PCB or a heat sink) associated with the next level assembly.
The terms “opening” and “aperture” and “hole” refer to a through-hole and are synonymous. For instance, the first post is exposed by the first adhesive in the first vertical direction when it is inserted into the first opening in the first adhesive and the second post is exposed by the second adhesive in the second vertical direction when it is inserted into the second opening in the second adhesive.
The term “inserted” refers to relative motion between elements. For instance, the first post is inserted into the first aperture regardless of whether the dielectric base is stationary and the first conductive layer moves towards the dielectric base, the first conductive layer is stationary and the dielectric base moves towards the first conductive layer or the dielectric base and the first conductive layer both approach the other. Furthermore, the first post is inserted (or extends) into the first aperture regardless of whether it goes through (enters and exits) or does not go through (enters without exiting) the first aperture.
The phrase “move towards one another” also refers to relative motion between elements. For instance, the dielectric base and the first conductive layer move towards one another regardless of whether the dielectric base is stationary and the first conductive layer moves towards the dielectric base, the first conductive layer is stationary and the dielectric base moves towards the first conductive layer or the dielectric base and the first conductive layer both approach the other.
The phrase “aligned with” refers to relative position between elements. For instance, the first post is aligned with the first aperture when the first adhesive is mounted on the dielectric base, the first conductive layer is mounted on the first adhesive, the first post is inserted into and aligned with the first opening and the first aperture is aligned with the first opening regardless of whether the first post is inserted into or spaced from the first aperture.
The phrase “mounted on” includes contact and non-contact with a single or multiple support element(s). For instance, the semiconductor device is mounted on the heat spreader regardless of whether it contacts the heat spreader or is separated from the heat spreader by a die attach.
The term “above” refers to upward extension and includes adjacent and non-adjacent elements as well as overlapping and non-overlapping elements. For instance, when the first post protrudes upward from the dielectric base and the second post protrudes downward from the dielectric base, the first post extends above, is adjacent to, overlaps and protrudes from the dielectric base Likewise, the plated through-hole extends above the second post even though it is not adjacent to or overlap the second post.
The term “below” refers to downward extension and includes adjacent and non-adjacent elements as well as overlapping and non-overlapping elements. For instance, when the first post protrudes upward from the dielectric base and the second post protrudes downward from the dielectric base, the dielectric base extends below, is adjacent to and is overlapped by the first post. Likewise, the plated through-hole extends below the first post even though it is not adjacent to or overlapped by the first post.
The “first vertical direction” and “second vertical direction” do not depend on the orientation of the semiconductor chip assembly (or the thermal board), as will be readily apparent to those skilled in the art. For instance, the first post extends vertically beyond the dielectric base in the first vertical direction and vertically beyond the first cap in the second vertical direction regardless of whether the assembly is inverted and/or mounted on a heat sink. Likewise, the dielectric base extends “laterally” from the posts in a lateral plane regardless of whether the assembly is inverted, rotated or slanted. Thus, the first and second vertical directions are opposite one another and orthogonal to the lateral directions, and laterally aligned elements are coplanar with one another at a lateral plane orthogonal to the first and second vertical directions. Furthermore, the first vertical direction is the upward direction and the second vertical direction is the downward direction when the first post protrudes upward from the dielectric base and the second post protrudes downward from the dielectric base, and the first vertical direction is the downward direction and the second vertical direction is the upward direction when the first post protrudes downward from the dielectric base and the second post protrudes upward from the dielectric base.
The semiconductor chip assembly of the present invention has numerous advantages. The assembly is reliable, inexpensive and well-suited for high volume manufacture. The assembly is especially well-suited for high power semiconductor devices such as LED chips and large semiconductor chips as well as multiple semiconductor devices such as small semiconductor chips in arrays which generate considerable heat and require excellent heat dissipation in order to operate effectively and reliably.
The manufacturing process is highly versatile and permits a wide variety of mature electrical, thermal and mechanical connection technologies to be used in a unique and improved manner. The manufacturing process can also be performed without expensive tooling. As a result, the manufacturing process significantly enhances throughput, yield, performance and cost effectiveness compared to conventional packaging techniques. Moreover, the assembly is well-suited for copper chip and lead-free environmental requirements.
The embodiments described herein are exemplary and may simplify or omit elements or steps well-known to those skilled in the art to prevent obscuring the present invention Likewise, the drawings may omit duplicative or unnecessary elements and reference labels to improve clarity.
Various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. For instance, the materials, dimensions, shapes, sizes, steps and arrangement of steps described above are merely exemplary. Such changes, modifications and equivalents may be made without departing from the spirit and scope of the present invention as defined in the appended claims.
Claims
1. A semiconductor chip assembly, comprising:
- a semiconductor device;
- a first adhesive that includes a first opening;
- a second adhesive that includes a second opening;
- a conductive trace that includes a pad, a terminal and an electrical interconnect in an electrically conductive path between the pad and the terminal; and
- a heat spreader that includes a first post, a second post and a dielectric base, wherein (i) the first post extends vertically from the dielectric base in a first vertical direction, (ii) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction and (iii) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts in lateral directions orthogonal to the vertical directions;
- wherein the semiconductor device is mounted on the first post, extends vertically beyond the dielectric base in the first vertical direction, extends laterally within peripheries of the posts, is electrically connected to the pad and thereby electrically connected to the terminal, is thermally connected to the first post and thereby thermally connected to the second post and is electrically isolated from the second post;
- wherein the first adhesive extends vertically beyond the dielectric base in the first vertical direction, extends laterally from the first post to or beyond the terminal and is sandwiched between the dielectric base and the pad;
- wherein the second adhesive extends vertically beyond the dielectric base in the second vertical direction, extends laterally from the second post to or beyond the terminal and is sandwiched between the dielectric base and the terminal;
- wherein the pad extends vertically beyond the dielectric base in the first vertical direction, the terminal extends vertically beyond the dielectric base in the second vertical direction and the electrical interconnect extends through the dielectric base and the adhesives; and
- wherein the first post extends into the first opening, the second post extends into the second opening and the dielectric base contacts and is sandwiched between the adhesives and covers the semiconductor device in the second vertical direction.
2. The assembly of claim 1, wherein the semiconductor device is an LED chip.
3. The assembly of claim 1, wherein the semiconductor device is electrically connected to the pad using a wire bond and is thermally connected to the first post using a die attach.
4. The assembly of claim 1, wherein the first adhesive contacts the first post and is spaced from the second post and the second adhesive contacts the second post and is spaced from the first post.
5. The assembly of claim 1, wherein the first adhesive covers and surrounds the first post in the lateral directions and the second adhesive covers and surrounds the second post in the lateral directions.
6. The assembly of claim 1, wherein the first adhesive extends to peripheral edges of the assembly and the second adhesive extends to peripheral edges of the assembly.
7. The assembly of claim 1, wherein the first adhesive is coplanar with the first post between opposing lateral surfaces of the pad and the second adhesive is coplanar with the second post between opposing lateral surfaces of the terminal.
8. The assembly of claim 1, wherein the first post has a diameter that decreases as it extends vertically from the dielectric base in the first vertical direction and the second post has a diameter that decreases as it extends vertically from the dielectric base in the second vertical direction.
9. The assembly of claim 1, wherein the first post has tapered sidewalls characteristic of wet chemical etching and the second post has tapered sidewalls characteristic of wet chemical etching.
10. The assembly of claim 1, wherein the dielectric base is (i) epoxy filled with aluminum oxide or aluminum nitride, (ii) polyimide filled with aluminum oxide or aluminum nitride, or (iii) diamond-like carbon.
11. The assembly of claim 1, wherein the dielectric base extends to peripheral edges of the assembly.
12. The assembly of claim 1, wherein the pad extends beyond the first adhesive in the first vertical direction and the terminal extends beyond the second adhesive in the second vertical direction.
13. The assembly of claim 1, wherein the pad contacts the first adhesive and the terminal contacts the second adhesive.
14. The assembly of claim 1, wherein the pad and the terminal are spaced from the adhesives, a first dielectric layer contacts and is sandwiched between the pad and the first adhesive and is spaced from the first post and the dielectric base, a second dielectric layer contacts and is sandwiched between the terminal and the second adhesive and is spaced from the second post and the dielectric base, the first post extends into a first aperture in the first dielectric layer, the second post extends through a second aperture in the second dielectric layer and the electrical interconnect extends through the dielectric layers.
15. The assembly of claim 1, wherein the electrical interconnect is a plated through-hole.
16. The assembly of claim 1, wherein the posts are the same metal and the pad and the terminal are the same metals.
17. The assembly of claim 1, wherein the pad and the terminal include a gold, silver or nickel surface layer and a buried copper core and are primarily copper, the posts include copper and the dielectric base includes plastic.
18. The assembly of claim 1, wherein the conductive trace includes a copper core shared by the pad, the terminal and the electrical interconnect.
19. The assembly of claim 1, wherein the heat spreader includes:
- a first cap that is adjacent to the first post, covers the first post in the upward direction and extends laterally from the first post and that contacts the first adhesive and extends beyond the first adhesive in the first vertical direction; and
- a second cap that is adjacent to the second post, covers the second post in the downward direction and extends laterally from the second post and that contacts the second adhesive and extends beyond the second adhesive in the second vertical direction.
20. The assembly of claim 19, wherein:
- the pad and the first cap have the same thickness where closest to one another and are coplanar with one another at a first surface that faces in the first vertical direction; and
- the terminal and the second cap have the same thickness where closest to one another and are coplanar with one another at a second surface that faces in the second vertical direction.
21. A semiconductor chip assembly, comprising:
- a semiconductor device;
- a first adhesive that includes a first opening;
- a second adhesive that includes a second opening;
- a conductive trace that includes a pad, a terminal and an electrical interconnect, wherein the electrical interconnect includes a plated through-hole in an electrically conductive path between the pad and the terminal; and
- a heat spreader that includes a first post, a second post, a first cap, a second cap and a dielectric base, wherein (i) the first post extends vertically from the dielectric base in a first vertical direction, (ii) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, (iii) the first cap is adjacent to the first post, covers the first post in the first vertical direction and extends laterally from the first post, (iv) the second cap is adjacent to the second post, covers the second post in the second vertical direction and extends laterally from the second post and (v) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts and laterally beyond the caps in lateral directions orthogonal to the vertical directions;
- wherein the semiconductor device is mounted on the first cap, extends vertically beyond the first cap and the first adhesive in the first vertical direction, extends laterally within peripheries of the posts, is located within peripheries of the caps, is electrically connected to the pad and thereby electrically connected to the terminal, is thermally connected to the first cap and thereby thermally connected to the second cap and is electrically isolated from the second cap;
- wherein the first adhesive contacts the first post, the first cap and the dielectric base, is spaced from the second post and the second cap, extends vertically beyond the dielectric base in the first vertical direction, extends laterally from the first post to or beyond the terminal and is sandwiched between the dielectric base and the pad;
- wherein the second adhesive contacts the second post, the second cap and the dielectric base, is spaced from the first post and the first cap, extends vertically beyond the dielectric base in the second vertical direction, extends laterally from the second post to or beyond the terminal and is sandwiched between the dielectric base and the terminal;
- wherein the pad extends vertically beyond the first adhesive in the first vertical direction, the terminal extends vertically beyond the second adhesive in the second vertical direction and the plated through-hole extends through the dielectric base and the adhesives;
- wherein the first post extends into the first opening, the second post extends into the second opening, the first cap extends vertically beyond the first adhesive in the first vertical direction, the second cap extends vertically beyond the second adhesive in the second vertical direction and the dielectric base is sandwiched between the adhesives and covers the semiconductor device in the second vertical direction; and
- wherein the posts and the caps are metallic, the dielectric base and the adhesives are non-metallic and extend to peripheral edges of the assembly, the caps are electrically isolated from one another and the second cap has no electrical function.
22. The assembly of claim 21, wherein the semiconductor device is an LED chip, is mounted on the first cap using a die attach, is electrically connected to the pad using a wire bond and is thermally connected to the first cap using the die attach.
23. The assembly of claim 21, wherein the first adhesive covers and surrounds the first post in the lateral directions and the second adhesive covers and surrounds the second post in the lateral directions.
24. The assembly of claim 21, wherein the first adhesive is coplanar with the first post at the first cap between opposing lateral surfaces of the pad and at the dielectric base and the second adhesive is coplanar with the second post at the second cap between opposing lateral surfaces of the terminal and at the dielectric base.
25. The assembly of claim 21, wherein the adhesives are spaced from one another.
26. The assembly of claim 21, wherein the first post has a diameter that decreases as it extends vertically from the dielectric base in the first vertical direction and the second post has a diameter that decreases as it extends vertically from the dielectric base in the second vertical direction.
27. The assembly of claim 21, wherein the first post has tapered sidewalls characteristic of wet chemical etching and the second post has tapered sidewalls characteristic of wet chemical etching.
28. The assembly of claim 21, wherein the dielectric base is (i) epoxy filled with aluminum oxide or aluminum nitride, (ii) polyimide filled with aluminum oxide or aluminum nitride, or (iii) diamond-like carbon.
29. The assembly of claim 21, wherein the pad contacts the first adhesive and the terminal contacts the second adhesive.
30. The assembly of claim 21, wherein the pad and the terminal are spaced from the adhesives, a first dielectric layer contacts and is sandwiched between the pad and the first adhesive, contacts the first cap and is spaced from the first post and the dielectric base, a second dielectric layer contacts and is sandwiched between the terminal and the second adhesive, contacts the second cap and is spaced from the second post and the dielectric base, the first post extends through a first aperture in the first dielectric layer, the second post extends through a second aperture in the second dielectric layer and the plated through-hole extends through the dielectric layers.
31. The assembly of claim 21, wherein the pad is located within the periphery of the second post.
32. The assembly of claim 21, wherein the first post has a surface area that is less than one-half of a surface area of the second post.
33. The assembly of claim 21, wherein the pad and the first cap have the same thickness where closest to one another and are coplanar with one another at a first surface that faces in the first vertical direction.
34. The assembly of claim 21, wherein the pad and the first cap have the same thickness where closest to one another, have different thickness where the first cap is adjacent to the first post and are coplanar with one another at a first surface that faces in the first vertical direction.
35. The assembly of claim 21, wherein the terminal and the second cap have the same thickness where closest to one another and are coplanar with one another at a second surface that faces in the second vertical direction.
36. The assembly of claim 21, wherein the terminal and the second cap have the same thickness where closest to one another, have different thickness where the second cap is adjacent to the second post and are coplanar with one another at a second surface that faces in the second vertical direction.
37. The assembly of claim 21, wherein:
- the pad and the first cap have the same thickness where closest to one another, have different thickness where the first cap is adjacent to the first post and are coplanar with one another at a first surface that faces in the first vertical direction; and
- the terminal and the second cap have the same thickness where closest to one another, have different thickness where the second cap is adjacent to the second post and are coplanar with one another at a second surface that faces in the second vertical direction.
38. The assembly of claim 21, wherein the posts are the same metal and the pad, the terminal and the caps are the same metals.
39. The assembly of claim 21, wherein the pad, the terminal and the caps include a gold, silver or nickel surface layer and a buried copper core and are primarily copper, the posts are copper, the plated through-hole includes copper and the dielectric base includes plastic.
40. The assembly of claim 21, wherein the conductive trace includes a copper core shared by the pad, the terminal and the plated through-hole.
41. A semiconductor chip assembly, comprising:
- a semiconductor device;
- a first adhesive that includes a first opening;
- a second adhesive that includes a second opening;
- a heat spreader that includes a first post, a second post, a first cap, a second cap and a dielectric base, wherein (i) the first post extends vertically from the dielectric base in a first vertical direction, (ii) the second post extends vertically from the dielectric base in a second vertical direction opposite the first vertical direction, (iii) the first cap is adjacent to the first post, covers the first post in the first vertical direction and extends laterally from the first post, (iv) the second cap is adjacent to the second post, covers the second post in the second vertical direction and extends laterally from the second post and (v) the dielectric base is a thermally conductive, electrically insulative material that contacts and is sandwiched between and thermally connects and electrically isolates the posts, covers the first post in the second vertical direction, covers the second post in the first vertical direction and extends laterally from the posts and laterally beyond the caps in lateral directions orthogonal to the vertical directions;
- a first conductive trace that includes a pad, a first terminal and a first electrical interconnect, wherein the first electrical interconnect includes a first plated through-hole in an electrically conductive path between the pad and the first terminal; and
- a second conductive trace that includes the first cap, a second terminal and a second electrical interconnect, wherein the second electrical interconnect includes a second plated through-hole in an electrically conductive path between the first cap and the second terminal;
- wherein the semiconductor device is mounted on the first cap, extends vertically beyond the first cap and the first adhesive in the first vertical direction, extends laterally within peripheries of the posts, is located within peripheries of the caps, is electrically connected to the pad and thereby electrically connected to the first terminal, is electrically connected to the first cap and thereby electrically connected to the second terminal, is thermally connected to the first cap and thereby thermally connected to the second cap and is electrically isolated from the second post and the second cap;
- wherein the first adhesive contacts the first post, the first cap and the dielectric base, is spaced from the second post and the second cap, extends vertically beyond the dielectric base in the first vertical direction, extends laterally from the first post to or beyond the terminals and is sandwiched between the dielectric base and the pad;
- wherein the second adhesive contacts the second post, the second cap and the dielectric base, is spaced from the first post and the first cap, extends vertically beyond the dielectric base in the second vertical direction, extends laterally from the second post to or beyond the terminals and is sandwiched between the dielectric base and the terminals;
- wherein the pad extends vertically beyond the first adhesive in the first vertical direction, the terminals extend vertically beyond the second adhesive in the second vertical direction and the plated through-holes extend through the dielectric base and the adhesives;
- wherein the first post extends into the first opening, the second post extends into the second opening, the first cap extends vertically beyond the first adhesive in the first vertical direction, the second cap extends vertically beyond the second adhesive in the second vertical direction and the dielectric base is sandwiched between the adhesives and covers the semiconductor device in the second vertical direction; and
- wherein the posts and the caps are metallic and spaced from peripheral edges of the assembly, the dielectric base and the adhesives are non-metallic and extend to peripheral edges of the assembly, the posts are electrically isolated from one another, the caps are electrically isolated from one another, the terminals are electrically isolated from one another and the second cap has no electrical function and electrically floats during operation of the semiconductor device.
42. The assembly of claim 41, wherein the semiconductor device is a vertical LED chip, is mounted on the first cap using a die attach, is electrically connected to the pad using a wire bond and is electrically and thermally connected to the first cap using the die attach.
43. The assembly of claim 41, wherein the first adhesive covers and surrounds the first post in the lateral directions and is coplanar with the first post at the first cap between opposing lateral surfaces of the pad and at the dielectric base, the second adhesive covers and surrounds the second post in the lateral directions and is coplanar with the second post at the second cap between opposing lateral surfaces of the first terminal and between opposing lateral surfaces of the second terminal and at the dielectric base and the adhesives are spaced from one another.
44. The assembly of claim 41, wherein the first post has a diameter that decreases as it extends vertically from the dielectric base in the first vertical direction and has tapered sidewalls characteristic of wet chemical etching and the second post has a diameter that decreases as it extends vertically from the dielectric base in the second vertical direction and has tapered sidewalls characteristic of wet chemical etching.
45. The assembly of claim 41, wherein the pad contacts the first adhesive and the terminals contact the second adhesive.
46. The assembly of claim 41, wherein the pad and the terminals are spaced from the adhesives, a first dielectric layer contacts and is sandwiched between the pad and the first adhesive, contacts the first cap and is spaced from the first post and the dielectric base, a second dielectric layer contacts and is sandwiched between the terminals and the second adhesive, contacts the second cap and is spaced from the second post and the dielectric base, the first post extends through a first aperture in the first dielectric layer, the second post extends through a second aperture in the second dielectric layer and the plated through-holes extend through the dielectric layers.
47. The assembly of claim 41, wherein:
- the pad and the first cap have the same thickness where closest to one another, have different thickness where the first cap is adjacent to the first post and are coplanar with one another at a first surface that faces in the first vertical direction;
- the first terminal and the second cap have the same thickness where closest to one another, have different thickness where the second cap is adjacent to the second post and are coplanar with one another at a second surface that faces in the second vertical direction; and
- the second terminal and the second cap have the same thickness where closest to one another, have different thickness where the second cap is adjacent to the second post and are coplanar with one another at the second surface.
48. The assembly of claim 41, wherein the posts are the same metal and the pad, the terminals and the caps are the same metals.
49. The assembly of claim 41, wherein the pad, the terminals and the caps include a gold, silver or nickel surface layer and a buried copper core and are primarily copper, the posts are copper, the plated through-holes include copper and the dielectric base includes plastic.
50. The assembly of claim 41, wherein the conductive trace includes a copper core shared by the pad, the first terminal and the first plated through-hole and the heat spreader includes a copper core shared by the first post, the first cap, the second plated through-hole and the second terminal.
Type: Application
Filed: Jul 28, 2011
Publication Date: Nov 17, 2011
Inventors: Charles W.C. Lin (Singapore), Chia-Chung Wang (Hsinchu)
Application Number: 13/192,463
International Classification: H01L 33/62 (20100101);
