Abstract: A semiconductor module in which a plurality of kinds of semiconductor devices having different heat generating amounts in being operated are mixedly present, heat conducting sheets are interposed between a module main body mounted to a board and outer faces of the semiconductor devices, and heat radiating plates are mounted thereto by covering outer faces of the semiconductor devices over two pieces or more of the semiconductor devices, wherein the heat conducting sheet having a heat conductivity higher than a heat conductivity of the heat conducting sheet used for the semiconductor device having a heat generating amount smaller than a heat generating amount of the semiconductor device is used for the semiconductor device having a large heat generating amount in the semiconductor devices.

Abstract: A heat dissipating module comprises a base having a hollowed frame, a clamping member, and a heat dissipating plate. The frame has a side wall and a post extending downwardly from each pair of faced edges thereof, the side wall has a hook at a bottom edge thereof, wherein the frame has a pivot passage at one edge thereof, and two symmetrical passages at an opposing edge and positioned at two sides of the opposed position to the pivot passage. The clamping member is a U-shaped rod having a pair of long sides and a lug folded outwardly at each of both free ends thereof. When assembling, a chip is clamped on the heat dissipating plate by the hook of the base, while middle straight segments of the long sides is pressed on a surface of the heat dissipating plate, to allow it to contact with the chip closely.

Abstract: Described is an apparatus for use supporting a heatsink thermally coupled to an integrated circuit component disposed on a first side of a circuit board. The heatsink has an opening that is aligned with an opening of the circuit board. The apparatus includes a support stud disposed beneath the heatsink on a second side of the circuit board. The support stud has a bore and is press fit into the opening of the circuit board from the second side and secured within the opening of the circuit board by a fastener passing through the aligned openings of the heatsink and the circuit board and into the bore. A capture mechanism, disposed on a surface adjacent and parallel to the second side of the circuit board, receives the support stud, thereby coupling the circuit board to the adjacent surface.

Abstract: This invention relates to a chip package structure comprising of a chip, multiple leads with inner and outer ends, an exposed chip upper surface, an encapsulated body encloses the peripherals of the chip, and multiple conducting wires used to connect electrically the chip and leads, wherein said leads extends internally to the surfaces on the two sides of the chip, in the mean time, pasting method is used to connect the two side surfaces of the chip to the leads in order to carry the chip, therefore, traditional die pad is replaced, furthermore, the outer ends or lower surfaces of the leads are exposed out of encapsulated body, this is to prevent solder overflow and enhance solder aggregation effect, in the mean time, packaging cost can be saved and easier visual positioning and rework can be obtained from this package structure, leads are used as terminals to be electrically connected to the external; therefore, through the internally extended leads structure, die pad is replaced, and the effects of package

Abstract: A heat dissipating device of the present invention includes a heat sink (20) and two locking devices (10) for securing the heat sink. The heat sink includes a base (22) for contacting an electronic component. Each locking device includes a spring member, a post (12) and a sleeve (18). The spring member elastically rests on the base. The post extends through the sleeve. The post has one end engaging with the spring member, and an opposite end thereof extending beyond the sleeve for locking the combination. The sleeve has one end tightly grasping the post, and an opposite end thereof preventing the locking device from departing from the heat sink.

Abstract: A cooling structure for an electronic device comprises a compliant cap preloaded over the electronic device. The compliant cap comprises a horizontal top surface and at least one vertical support for the surface, the vertical support comprising a compliant portion and wherein the compliant cap comprises a thermally conducting material.

Abstract: A locking device for securing a heat sink to a heat generating component includes a locking plate, a plurality of locking feet each pivotably attached to the locking plate and a plurality of locking members attached to the locking feet. Adjacent two of the plurality of locking feet are capable of rotating towards each other from a first position at which the locking feet are located apart from each other with the locking members defining a first mounting position to a second position at which the locking feet are stacked together with the locking members defining a second mounting position.

Abstract: A fan holder (1) includes a base (12) for supporting a fan (3) thereon and a pair of locking members (14) pivotally connected to the base. Each of the locking members includes a pivot shaft (142) and a handle (144) extending perpendicularly from the pivot shaft. The pivot shaft includes a pivot section (1422) and a pressing section (1426) offsetting from the pivot section and spaced from the base, wherein the handle is capable of rotating about an axis of the pivot shaft to lock with the base and to cause the pressing section to exert a force against the fan toward the base to securely attach the fan to the base.

Abstract: A heat sink mounting assembly includes a retention module having a bottom and a pair of posts extending from the bottom. A heat sink is located on the bottom of the retention module. A clip spans across the heat sink and includes a clamping member having first and second legs releasably engaging with the posts of the retention module, and a pressing member having a first end thereof pivotably engaging with a first end of the clamping member. The pressing member has a pressing portion pressing the heat sink toward the retention module when a second end of the pressing member is depressed to engage with a pair of ears formed at a second end of the clamping member.

Abstract: A chip component (1) includes a semiconductor body (2), in which at least one switchable element (6, 62) is arranged in a partial region (24) of the semiconductor body (2). The partial region (24) can be reached by light of at least one wavelength. Furthermore, a circuit (9) integrated into the semiconductor body (2) is provided, which integrated circuit can assume one configuration from at least two possible configurations, one of these configurations being prescribed by a state of the at least one switchable element (6, 62). Furthermore, a housing (3) is provided, which encloses the semiconductor body (2) and is arranged with a partial region (35, 32) at least partly above the partial region (24) of the semiconductor body (2). The partial region (35, 32) of the housing (3) is formed in such a way that light can be fed to the partial region (24) of the semiconductor body (2).

Abstract: A power semiconductor module has a substrate (1) on which several pressure elements (16, 17, 18, 19) perform a mechanical pressure (F) at different areas (10, 11, 12, 13) thereof in a direction of a cooling element in order to press the underside (1b) of the substrate and reject heat towards said cooling element. In order to apply an essentially even and non-influenced by the component tolerances force to each area of the substrate, the pressure elements perform an elastic action on the substrate areas. The pressure elements (16, 17, 18, 19) are formed on the first part (21) of a housing which is movable with respect to the second part (22) thereof provided with spacing elements (30, 31, 32, 33) defining a supporting surface (34) in such a way that the first part (21) of the housing is fixed at a certain distance from the substrate (1).

Abstract: A wire fixture (27) is for fastening power wires (246) of a heat-dissipating fan (24) to a supporting surface of a heat dissipation device (20). The heat dissipation device is for dissipating heat from a heat-generating electronic component. The wire fixture includes a catching portion (278) for being attached to an end of the supporting surface, a fixing portion (272) disposed with adhesive thereon, for being fixed to an opposite end of the supporting surface, and a covering portion (276) formed between the catching portion and the fixing portion and being without adhesive spread thereon, for urging the power wires of the heat dissipating fan to the supporting surface. The catching portion is without adhesive thereon.

Abstract: A heat sink assembly (100) includes a heat sink (10) having a plurality of fins (14), a fan handle (24) buckled with the fins and a fan (30) mounted on the heat sink (10) via the fan handle. The fan handle includes a retaining body (26) clasping two adjacent fins having a space therebetween. A screw (22) is extended through the fan and into the space of the two adjacent fins. The retaining body includes a pair of opposite lateral walls (260) clamping opposite sides of the two adjacent fins, for preventing the two adjacent fins from being over expanded outwardly during the insertion of the screw into the space.

Abstract: A semiconductor device capsule comprising a semiconductor assembly mounted between opposed poles. At least one of the poles includes slots around the locality of the or each chip or group of chips within the semiconductor assembly to define a contact body portion on which the or each chip or group of chips is mounted and reduce the thickness of a laterally continuous body portion of the pole.

Abstract: In one embodiment, a liquid immersion cooled multichip module is provided which includes a substrate having chips mounted thereon and which is adapted to mount with a printed circuit board. A lid is adapted to secure to the printed circuit board so as to mount with the substrate to form a fluid chamber between the lid and the substrate, and to cause the substrate to mate with the printed circuit board. In one embodiment, a cambered bolster plate is located on a side of the printed circuit board opposite the lid and the lid is fastened to the bolster plate to secure the lid to the printed circuit board. A baffle, which may be removable in some embodiments, is located within the lid and directs coolant flow through the fluid chamber.

Abstract: An interface is formed by pressing a patterned first surface and a second surface together, with a particle-loaded interface material in between. The first surface is fabricated with a pattern of channels designed to redistribute the velocity gradients that occur in the interface material during interface formation in order to control the arrangement, orientation and concentration of particles at the end of the interface formation. The concept finds application in thermal interfaces and controlled placement of nano and micro particles and biological molecules.

Abstract: A ball grid array (BGA) socket is adapted to receive and electrically connect to an integrated circuit disposed between a circuit substrate and a heat sink. An attachment element is adapted to hold the Socket BGA to the circuit substrate with a compressive load isolated from the heat sink.

Abstract: A secure device for a heat dissipating component provides a base body with a plurality of engaging members attached to two lateral sides thereof. Each of the engaging members further has a secure part and a follower part for clamping the heat dissipating component.

Abstract: A bracing apparatus is disclosed that has a component located within an opening in a cantilevered end of a heatsink. The component has a form factor that is expandable for stabilizing the heatsink at a given elevation relative to a printed circuit board. The bracing apparatus includes a tensioning device located within an opening in the component. When deployed, the tensioning device causes the component to expand. Also included in the bracing apparatus is a coupling medium for coupling the component to the printed circuit board.

Abstract: In a multi-device holding structure for integrally holding two heat generative elements which are transistors having through-holes so as to be mounted on a base plate, and a heat sensitive element which is a temperature fuse sandwiched between the heat sensitive elements and is mounted on the base plate, the heat generative elements and the heat sensitive element are covered with a metallic holding member provided with first flat spring segments for urging the heat generative elements on both ends as well as inserting segments extending upward and inserted into the through-holes, and second flat spring segments for supporting the sides of the heat sensitive element.

Abstract: A supporting plate includes a metal plate and is utilized to support a heat sink module in an electronic device. The heat sink module has a thermal pad, and the electronic device has a first heat generating element and a second heat generating element. In addition, the heat sink module is contacted to the first heat generating element for conducting heat generated by the first heat generating element to the thermal pad. Moreover, the metal plate has a first concave portion and a second concave portion. The first concave portion is contacted to the thermal pad, and the second concave portion is contacted to the second heat generating element for conducting heat generated by the second heat generating element to the heat sink.

Abstract: A semiconductor device carrier comprising; a carrier housing having a housing portion for accommodating a semiconductor device; an electrode sheet disposed in the carrier housing, having a front surface wiring conductively arranged on a front surface of an insulation substrate, a rear surface wiring conductively arranged on a rear surface of the insulation substrate, a rear surface bump contact placement wiring, and a bump contact disposed in a contact placement portion and an elastic sheet disposed in the carrier housing to be in contact with the bottom of the electrode sheet; wherein a width of the rear surface bump contact placement wiring in correspondence to a bump contact to be in contact with an extreme electrode section of the semiconductor device is smaller than a width of the front surface bump contact placement wiring on which a bump contact to be in contact with the extreme electrode section is arranged.

Abstract: A semiconductor power circuit in which multiple field effect transistor dies are solder connected between opposed contact surfaces of overlying flat conductors and are clamped by means of spring clips which are arranged in symmetrically opposed relationship. A circuit board also disposed between the clamped surfaces is protected from the clamping forces by means of a soft paper layer with holes registering with similar holes in the circuit board to permit solder pads to pass there through.

Abstract: A holding fixture that holds a component and mounts the component on an electronic circuit board includes a holding member that holds the component at a side of a first surface of the electronic circuit board, a first fixing member that includes a first base that is engageable with the holding member, and an elastic member that is pivotally attached to the base, sandwiches the electronic circuit board at a side of a second surface of the electronic circuit board, and elastically supports the holding member at the side of the first surface, the second surface opposing to the first surface, and a second fixing member that includes a second base that is engageable with the holding member, and a projection member that projects from the second surface of the electronic circuit board and is engageable with the elastic member.

Abstract: A frame of a heat sink for a CPU in a computer includes a quadrilateral frame member and four stop plates. One of two opposite sides of the quadrilateral frame member has an opening block step with a length being equal to the width of the heat sink and the bottom of the block step is the same elevation as the top of the second side. The distance between two of the stop plates, which are disposed at both ends of the first side, is equal to the length of the first side. A reinforcing rib is disposed between another two of the stop plates, which are disposed at both ends of the second side, and is parallel to the second side with an elevation higher than the top of the second side and a distance between the inner surface of the reinforcing rib and the block step is equal to the depth of the heat sink for increasing strength and rigidity of the frame against deformation and preventing the heat sink from swaying.

Abstract: A semiconductor package with a heat dissipating device and a fabrication method of the semiconductor package are provided. A chip is mounted on a substrate. The heat dissipating device is mounted on the chip, and includes an accommodating room, and a first opening and a second opening that communicate with the accommodating room. An encapsulant is formed between the heat dissipating device and the substrate to encapsulate the chip. A cutting process is performed to remove a non-electrical part of structure and expose the first and second openings from the encapsulant. A cooling fluid is received in the accommodating room to absorb and dissipate heat produced by the chip. The heat dissipating device covers the encapsulant and the chip to provide a maximum heat transfer area for the semiconductor package.

Abstract: A heat sink clip assembly is for attaching a heat sink (10) to a motherboard (60). The motherboard and the heat sink each respectively define through apertures (52) and through holes (16) therein. The heat sink clip assembly includes four sleeves (46), four posts (38), four fasteners (41), and four spring members (44). Each sleeve comprises a top section and a bottom section. The top sections of the sleeves engage in the through holes respectively to attach the sleeves to the heat sink. The posts extend through the through apertures and received in the bottom sections of the sleeves. Each fastener includes a top head and a bottom end, the bottom ends extend into the sleeves and coupled to the top portions of the posts. The spring members are compressed between the top heads of the fasteners and the heat sink urging the heat sink toward the motherboard.

Abstract: A heat dissipation apparatus includes a metal enclosure for an electronic device, at least one heat pipe secured to the enclosure, a fin assembly secured to the enclosure, a centrifugal blower secured to the enclosure for promoting heat dissipation for the fin assembly. The heat pipe has an evaporating section thermally connecting with a heat generating electronic component within the enclosure, and first and second condensing sections respectively connecting with the enclosure and the fin assembly. The enclosure absorbs and dissipates heat generated by the heat generating electronic component. The heat dissipation surface area is increased and as a result the heat dissipation efficiency of the heat dissipation apparatus is improved.

Abstract: A thermal transfer material is described herein that includes: a heat spreader component, wherein the heat spreader component comprises a top surface, a bottom surface and at least one heat spreader material, and at least one solder material, wherein the solder material is directly deposited onto the bottom surface of the heat spreader component. Methods of forming layered thermal interface materials and thermal transfer materials include: a) providing a heat spreader component, wherein the heat spreader component comprises a top surface, a bottom surface and at least one heat spreader material; b) providing at least one solder material, wherein the solder material is directly deposited onto the bottom surface of the heat spreader component; and c) depositing the at least one solder material onto the bottom surface of the heat spreader component.

Abstract: An electronic assembly includes a PCB (20), a socket (22) mounted on the PCB, a CPU (24) connected with the socket, a heat sink (10) in thermal contact with the CPU, a foldable back plate (30) attached to an underside of the PCB and a base plane (40) forming four bridges (42). The back plate includes a first piece section (32) and a second piece section (34) pivotally joined together by a pivot (36). The first and the second piece sections each comprise two legs inserted into two corresponding bridges. Screws are used to extend through the heat sink, the PCB, the bridges to threadedly engage with the legs of the back plate, respectively. The pivot is located under a part of the PCB at which the CPU is mounted.

Abstract: A multi stack package with a package lid may be provided. In the multi stack package, the package lid, which may be positioned on an upper part of a semiconductor package module of the stacked semiconductor package modules, may include a device to improve the electrical performance such as the signal transferring quality of semiconductor chips. The device may be inside or on a surface of the printed circuit board core forming the package lid. The devices, which may be formed on the semiconductor package module substrate in a conventional multi stack package, may be included in the package lid, thereby securing a region for circuit design on the semiconductor package module substrate.

Abstract: A coolant cooled type semiconductor device capable of achieving a superior heat radiation capability is provided, while having a simple structure. While a plurality of semiconductor modules are arranged in such a manner that main surface directions of these semiconductor modules are positioned in parallel to each other in a interval along a thickness direction thereof. These semiconductor modules are sandwiched by coolant tube having folded portions with fixing members. As a consequence, both surfaces of the semiconductor module can be cooled by a single coolant tube with a uniform pinching force.

Abstract: A semiconductor device includes a heat generation element; a bonding member; first and second heat radiation plates disposed on first and second sides of the heat generation element through the bonding member; a heat radiation block disposed between the first heat radiation plate and the heat generation element through the bonding member; and a resin mold. The heat radiation block has a thickness in a range between 0.5 mm and 1.5 mm. The semiconductor device has high reliability of the bonding member.

Abstract: A locking device includes a flat plate for contacting with a heat-generating electronic component, a plurality of fins mounted on the flat plate, four locking feet and four fasteners. The flat plate includes two locking portions at opposite sides thereof. Each locking foot includes two spaced pivot plates at an end thereof, wherein the locking portions of the flat plate are sandwiched between the pivot plates. The locking feet are pivotably connected to the locking portions. The fasteners are secured to ends of the locking feet respectively, opposite to the ends where the spaced pivot plates are formed. The locking feet are pivotably movable between first and second positions. The locking device can be mounted to a first-typed PCB at the first position and a second-typed PCB at the second position.

Abstract: A thermal assembly for cooling an electronics module is described. The assembly includes a compressible thermal pad, a thermal plate, and a clip. The thermal plate attaches to a heat sink. The clip urges the thermal pad against a surface of the thermal plate. Heat generated by electronics components in the pluggable electronics module is conducted to the heat sink through a thermal path defined by the thermal plate, the compressible thermal pad, and the clip.

Abstract: A semiconductor device includes: first and second metallic plates, each of which includes a heat radiation surface and an inner surface; a semiconductor element between the metallic plates; a block between the second metallic plate and the semiconductor element; a solder member between the second metallic plate and the block; and a resin mold. The heat radiation surface is exposed from the resin mold. The second metallic plate includes a groove for preventing the solder member from expanding outside of the block. The groove is disposed on the inner surface and disposed on an outer periphery of the block. The second metallic plate further includes an inner surface member on an inner surface of the groove. The inner surface member has a solder wettability, which is larger than a solder wettability of the block.

Abstract: In a state wherein front ends of latch members 18A and 18B are apart from each other so that the upper surface of an alignment plate/positioning member 24 is outside, a pressing section 12PU of a heat sink member 12 is brought into contact with the periphery of a semiconductor device 22.

Abstract: A thermal enhance semiconductor package with a universal heat spreader mainly comprises a carrier, a semiconductor chip and a universal heat spreader. The semiconductor chip is electrically connected to the carrier in a flip-chip fashion and the universal heat spreader is mounted on the back surface of the semiconductor chip. Therein the universal heat spreader has a plurality of through holes for upgrading the efficiency of heat transmission. Moreover, a heat transmission pin is provided in one of the through holes to increase the areas for heat dissipation so as to enhance the thermal performance of the package.

Abstract: A chip sandwich includes a heat sink, a retention module, a computer chip mounted in a socket on a mother board, a wave washer spring and a mounting plate. The heat sink is mounted on the retention module using cams, hooks and heat sink tabs to provide an initial orientation of the heat sink over the computer chip. To provide final contact pressure between the heat sink and the computer chip, a wave washer spring oriented beneath the computer chip and under the mother board provides an upward pressure against the bottom of the mother board, and particularly against the center of the computer chip. Thus, by the wave washer spring pushing against the center of the computer chip, secure contact pressure is provided between the heat sink and the computer chip, while minimizing the amount of pressure between the computer chip's pins and the chip socket.

Abstract: An electronic assembly comprises a support board, an integrated circuit chip interconnected and coupled to the support board, and a thermal-gap-filler pad placed over the integrated circuit chip and in contact with an external device to dissipate heat generated by the integrated circuit chip. The electronic assembly further comprises a standoff structure disposed adjacent the thermal-gap-filler pad and coupled to the support board, the standoff structure configured to prevent excessive force from being applied onto the thermal-gap-filler.

Abstract: A retainer includes a retention module surrounding a heat sink and two clip members for cooperating with the retention module to retain the heat sink. Each clip member includes a strap resting on the heat sink and a pair of legs located at opposite ends of the strap and engagable with the retention module. The legs are pivotably attached to opposite ends of the strap. Friction between the legs and the strap is capable of holding the legs at any positions between released positions at which the legs are free from the retention module and engaged positions at which the legs are engaged with the retention module.

Abstract: There is provided a small-size electronic heat pump device which is low in power consumption and which secures a vacuum gap without use of an additional circuit. The electronic heat pump device includes an emitter 1 and a collector 2. An electrically and thermally insulative spacer section 5 for keeping a space, i.e. vacuum gap G between an emitter electrode 11 and a collector electrode 21 constant is integrally formed in a semiconductor substrate 20 of the collector 2, which makes it possible to maintain the vacuum gap to be a specified space while a back flow of heat is prevented in a simple structure with a reduced number of component parts.

Abstract: A heat dissipation device for dissipating heat form a heat source includes a control unit, a sensor, a first heat dissipation module, a second heat dissipation module, and a driving mechanism. The sensor electrical connects with the control unit and detects a temperature of the heat source, and reports the temperature to the control unit. The second heat dissipation module is retractably connected to the first heat dissipation module. The driving mechanism is electrically connected to the control unit and the second heat dissipation module. When the temperature exceeds a first temperature, the control unit informs the driving mechanism to extend away from the second heat dissipation module with respect to the first heat dissipation module.

Abstract: A radiator structure includes a radiator frame, a radiator and a plurality of elastic latch members. The radiator frame is mounted onto a main board corresponding to an electronic element, and has a plurality of coupling sections and an opening corresponding to the electronic element and the surface of the electronic element exceeds its peripheral edges. The radiator is mounted on the radiator frame in contact with the surface of the electronic element, and has a plurality of latch sections corresponding to the coupling sections. The elastic latch member coupled on the latch section is bent to form a force applying section, a latch arm and a swinging arm. After the force applying section receives a force, the swinging arm coupled on the latch section is turned to enable the latch arm to latch on the coupling section thereby to anchor the radiator on the radiator frame to disperse heat.

Abstract: An electric circuit module comprising: an electric device comprising an electric circuit to serve for passage and interruption of electric current, a packing material packing the electric circuit and a plurality of wiring members to electrically connect the electric circuit with an external circuit; and a heat sink to radiate heat from the electric device. The electric circuit module includes a fixture to fix the heat sink and the electric device together so that a heat radiating surface of the electric device comes into contact with the heat sink. The fixture is formed with a recess to accommodate therein a part of the electric device so that the heat radiating surface of the electric device is exposed from the fixture. When the electric device is fixed to the heat sink by the fixture, the heat radiating surface comes into contact with the heat sink.

Abstract: Methods and associated apparatus of reducing stress in a package are described in which a package is provided comprising an array of interconnects that are connected to a substrate, and then reducing the stress of the interconnects located near a weak area in the package, during flexure of the substrate, by spring loading the weak area of the package.

Abstract: Structures and methods for holding heat sinks in contact with electronic devices are described herein. In one embodiment, an assembly for holding a heat sink in contact with an electronic device includes a coil spring in transverse compression. When transversely compressed, the coil spring presses the heat sink against the electronic device with a uniform, or at least approximately uniform, pressure that enables the heat sink to efficiently conduct heat away from the electronic device without damaging the device.

Abstract: A heat sink protecting retention module is described. The heat sink protecting retention module has a main frame, protective feet, hooks, and a positioning mechanism. The protective feet are disposed under the main frame to keep screws therein before the heat sink protecting retention module is installed on the motherboard so as to avoid scratching the motherboard or damaging electric components thereon. The hooks are disposed on the main frame for clamping the heat sink and the positioning mechanism are disposed around and under the main frame for aligning the heat sink protecting retention module to a central processing unit socket.

Abstract: A retainer (20) for a heat sink includes a supporting member (22), a bracket member (24), a pair of locking members (26) and an operating member (28). The supporting member defines a pair of openings (222) at opposite ends thereof. The bracket member is located above the supporting member and has a pair of abutting portions (246) extending therefrom. The locking members respectively pass through the openings of the supporting member and are pivotably attached to the bracket member. Each locking member has a spring portion (264) depressed on one of said abutting portions to maintain the locking member at a releasing position. The operating member is pivotable relative to the bracket member to cause the bracket member and the associated locking members to move upward and the supporting member to drive the locking members to turn toward each other to a locking position.

Abstract: Heat sink retention assemblies and related methods are described. In one embodiment, a system comprises a base, a handle rotatably mounted on the base, and heat sink retention structure joined with the handle and moveable by the handle between an opened and a closed position effective to secure a heat sink on a substrate.