LED WITH PHOSPHOR TILE AND OVERMOLDED PHOSPHOR IN LENS
Overmolded lenses and certain fabrication techniques are described for LED structures. In one embodiment, thin YAG phosphor plates are formed and affixed over blue LEDs mounted on a submount wafer. A clear lens is then molded over each LED structure during a single molding process. The LEDs are then separated from the wafer. The molded lens may include red phosphor to generate a warmer white light. In another embodiment, the phosphor plates are first temporarily mounted on a backplate, and a lens containing a red phosphor is molded over the phosphor plates. The plates with overmolded lenses are removed from the backplate and affixed to the top of an energizing LED. A clear lens is then molded over each LED structure. The shape of the molded phosphor-loaded lenses may be designed to improve the color vs. angle uniformity. Multiple dies may be encapsulated by a single lens. In another embodiment, a prefabricated collimating lens is glued to the flat top of an overmolded lens.
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This is a continuation-in-part (CIP) of U.S. application Ser. No. 11/093,961, filed Mar. 29, 2005, entitled “Wide Emitting Lens for LED Useful for Backlighting,” by Willem Smits, Grigorily Basin, et al., which is a CIP of U.S. application Ser. No. 11/069,418, filed Feb. 28, 2005, by Grigoriy Basin et al., entitled “Overmolded Lens Over LED Die,” which is a CIP of U.S. application Ser. No. 10/990,208, filed Nov. 15, 2004, by Grigoriy Basin et al., entitled “Molded Lens Over LED Die,” all incorporated herein by reference.
FIELD OF THE INVENTIONThis invention relates to light emitting diodes (LEDs) and, in particular, to certain lens designs and a technique for forming a lens over an LED die.
BACKGROUNDLED dies typically emit light in a lambertian pattern. It is common to use a lens over the LED die to narrow the beam or to make a side-emission pattern. A common type of lens for a surface mounted LED is preformed molded plastic, which is bonded to a package in which the LED die is mounted. One such lens is shown in U.S. Pat. No. 6,274,924, assigned to Philips Lumileds Lighting Company and incorporated herein by reference.
SUMMARYA technique for forming a molded lens for surface mounted LEDs is described herein along with various designs of lenses. Also described are various techniques for providing color converting phosphors within the lens.
In one method for forming lenses, one LED die or multiple LED dice are mounted on a support structure. The support structure may be a ceramic substrate, a silicon substrate, or other type of support structure with the LED dice electrically connected to metal pads on the support structure. The support structure may be a submount, which is mounted on a circuit board or a heat sink in a package.
A mold has indentations in it corresponding to the positions of the LED dice on the support structure. The indentations are filled with a liquid, optically transparent material, such as silicone, which when cured forms a hardened lens material. The shape of the indentations will be the shape of the lens. The mold and the LED dice/support structure are brought together so that each LED die resides within the liquid lens material in an associated indentation.
The mold is then heated to cure (harden) the lens material. The mold and the support structure are then separated, leaving a complete lens over each LED die. This general process will be referred to as overmolding. In contrast to injection molding techniques where the liquid material is injected at high pressure after the empty mold is encased around the object to be encapsulated, the present invention uses no such injection and the LED and any wire bonds are not stressed by the molding process. Also, there is very little waste of the lens material. Further, there are no conduits between mold indentions, as would be required for injection molding.
The overmolding process may be repeated with different molds to create overlapping shells of lenses. The lenses may contain any combinations of phosphors to convert the LED light to any color, including white.
In one embodiment, thin ceramic phosphor plates are formed by sintering phosphor grains under heat and pressure or by drying a slurry of phosphor grains. Each plate has a surface approximately the size of the top surface of the energizing LED, such as a blue LED. The phosphor may be YAG phosphor, where the combination of the blue light from the LED and the green-yellow light from the YAG phosphor produces white light. The plates may be affixed over LEDs mounted on a submount wafer, and a clear lens is then molded over each LED structure. The submount is then singulated to separate the LED structures.
In another embodiment, the molded lens over the LED and YAG phosphor plate includes red phosphor to generate a warmer white light.
In another embodiment, the phosphor plates are first temporarily mounted on a backplate, and a lens containing a red phosphor is molded over the phosphor plates. The plates with overmolded lenses are removed from the backplate and affixed to the top of an energizing LED. A clear lens is then molded over each LED structure.
Since the phosphor plate is flat, the color temperature becomes hotter (more blue) as the viewing angle approaches an angle normal to the surface of the LED/phosphor. To compensate for this color vs. angle non-uniformity, the shape of the mold containing the red phosphor is defined so that the color temperature is more uniform as the viewing angle changes. The shape of the mold is therefore dependent on the particular LED and phosphor plate used.
In one embodiment, the cured silicone used to form the outer lens by overmolding is much harder than any inner lens formed by overmolding. The softer inner lens does not put stress on the delicate LED when the lens is being formed or when the LED generates heat, while the hard outer lens protects against the outside elements and remains clean.
In another embodiment, multiple LEDs or an LED and another chip, such as for electrostatic discharge (ESD) protection, are encapsulated by a single overmolded lens, where the shape of the lens is based on the particular chips being encapsulated.
In another embodiment, an molded lens is formed over an LED, where the lens may be clear or phosphor loaded. The top of the lens has a flat portion. A prefabricated collimating lens, such as a Fresnel lens, approximately the same size as the LED, is then affixed to the flat portion of the overmolded lens. Such a small collimated light source is particularly useful as a cell phone camera flash.
In another embodiment, a soft silicone gel is used as an underfill between the LED and the submount to fill in any voids. The underfill may optionally coat the sides of the LED. The resulting structure is then overmolded with a hard lens. The underfill helps support the LED die during processing and operation, couples heat to the submount, and reduces stress between the LED die and the hard outer lens.
Many other embodiments of lenses and applications are described.
Elements labeled with the same numeral in the various figures may be the same or equivalent.
DETAILED DESCRIPTIONAs a preliminary matter, a conventional LED is formed on a growth substrate. In the example used, the LED is a GaN-based LED, such as an AlInGaN LED, for producing blue or UV light. Typically, a relatively thick n-type GaN layer is grown on a sapphire growth substrate using conventional techniques. The relatively thick GaN layer typically includes a low temperature nucleation layer and one or more additional layers so as to provide a low-defect lattice structure for the n-type cladding layer and active layer. One or more n-type cladding layers are then formed over the thick n-type layer, followed by an active layer, one or more p-type cladding layers, and a p-type contact layer (for metallization).
Various techniques are used to gain electrical access to the n-layers. In a flip-chip example, portions of the p-layers and active layer are etched away to expose an n-layer for metallization. In this way the p contact and n contact are on the same side of the chip and can be directly electrically attached to the package (or submount) contact pads. Current from the n-metal contact initially spreads laterally through the n-layer. In contrast, in a vertical injection (non-flip-chip) LED, an n-contact is formed on one side of the chip, and a p-contact is formed on the other side of the chip. Electrical contact to one of the p or n-contacts is typically made with a wire or a metal bridge, and the other contact is directly bonded to a package (or submount) contact pad. A flip-chip LED is used in the examples of
Examples of forming LEDs are described in U.S. Pat. Nos. 6,649,440 and 6,274,399, both assigned to Philips Lumileds Lighting Company and incorporated by reference.
Optionally, a conductive substrate is bonded to the LED layers (typically to the p-layers) and the sapphire substrate is removed. One or more LED dice may be bonded to metal pads on a submount, with the conductive substrate directly bonded to the metal pads, to be described in greater detail with respect to
The particular LEDs formed and whether or not they are mounted on a submount is not important for purposes of understanding the invention.
A mold 14 has indentations 16 corresponding to the desired shape of a lens over each LED die 10. Mold 14 is preferably formed of a metal. A very thin non-stick film 18, having the general shape of mold 14, is placed or formed over mold 14. Film 18 is of a well known conventional material that prevents the sticking of silicone to metal.
Film 18 is not needed if the lens material does not stick to the mold. This may be accomplished by using a non-stick mold coating, using a non-stick mold material, or using a mold process that results in a non-stick interface. Such processes may involve selecting certain process temperatures to obtain the minimum stick. By not using film 18, more complex lenses can be formed.
In
A vacuum seal is created between the periphery of the support structure 12 and mold 14, and the two pieces are pressed against each other so that each LED die 10 is inserted into the liquid lens material 20 and the lens material 20 is under compression.
The mold is then heated to about 150 degrees centigrade (or other suitable temperature) for a time to harden the lens material 20.
The support structure 12 is then separated from mold 14. Film 18 causes the resulting hardened lens to be easily released from mold 14. Film 18 is then removed.
In another embodiment, the LED dice 10 in
The lens 22 not only improves the light extraction from the LED die and refracts the light to create a desired emission pattern, but the lens also encapsulates the LED die to protect the die from contaminants, add mechanical strength, and protect any wire bonds.
The LED die 10 in
In one embodiment, the circuit board 45 itself may be the support structure 12 of
A common prior art encapsulation method is to spin on a protective coating. However, that encapsulation process is inappropriate for adding a phosphor coating to the LED die since the thickness of the encapsulant over the LED die is uneven. Also, such encapsulation methods do not form a lens. A common technique for providing a phosphor over the LED die is to fill a reflective cup surrounding the LED die with a silicone/phosphor composition. However, that technique forms a phosphor layer with varying thicknesses and does not form a suitable lens. If a lens is desired, additional processes still have to create a plastic molded lens and affix it over the LED die.
Processes for coating an LED with a phosphor are time-consuming. To eliminate the process for coating the LED die with a phosphor, the phosphor powder may be mixed with the liquid silicone so as to become embedded in the lens 62, shown in
As shown in
Many other shapes of lenses can be formed using the molding technique described above.
Additionally, the molded lens can be made very small (e.g., 1-2 mm diameter), unlike a conventional lens. Thus, a very small, fully encapsulated LED can be formed. Such LEDs can be made to have a very low profile, which is beneficial for certain applications.
As discussed with respect to
An underfill material may be injected to fill any gap between the bottom of the LED die 10 and the support substrate 12 to prevent any air gaps under the LED and to improve heat conduction, among other things.
The requirements for the inner lens are generally different from the requirements for the outer lens. For example, the inner lens should have good adhesion to the support structure, not yellow or become more opaque over time, have a high index of refraction (greater than 1.4), not break or stress any wires to the LED, withstand the high LED temperatures, and have a compatible thermal coefficient. The inner lens should be non-rigid (e.g., silicone) to not provide stress on the LED or any wires. In contrast, the outer lens material generally only needs to be able to be patterned with the desired pattern and adhere to the inner lens. The outer lens may overmolded or may be preformed and adhesively affixed to the inner lens. The material for the outer lens may be UV curable, while the material for the inner lens may be thermally cured. Thermal curing takes longer than UV curing.
Generally, the range of hardness for the inner lens material is Shore 00 5-90, while the range of hardness for the outer shell(s) is Shore A 30 or more.
The surface patterns of FIGS. 19 and 21-23 may be configured (e.g., by changing the surface angles) to create any light pattern. Holographic structures, TIR, and other patterns may be formed. Collimating light patterns are typically used for rear projection TVs, while side-emitting light patterns are typically used for backlighting LCD screens.
The LEDs in all figures may be flip-chips or wire bonded types.
As described above, the primary lens or secondary lens can be designed to create a side-emitting pattern. Such a side emitting pattern is particularly useful when light from multiple LEDs is intended to be mixed, such as when light from multiple LEDs is for creating a uniform backlight for an LCD panel, or for decorative lighting, or for another use.
As shown in
Applicants have invented a wide-emitting lens, shown in
The brightness profile should have no sharp transitions like those that typically appear with funnel shaped lenses at the center cusp.
The optimum ratio of the center axis intensity to the 50-80 degree peak intensity will depend on the application, such as the pitch of the LEDs needed to achieve the specified brightness of the backlight. The peak intensity is at least three times the intensity along the center axis and, in the embodiment of
The submount 196 is then separated out and then mounted on a backplane 190 (a PCB) by a solder reflow technique or other suitable technique.
A secondary lens 202 is preformed to have the desired wide-emitting characteristics. The secondary lens may be injection-molded or machined plastic or other material. Such materials include COC, COP, PMMA, epoxy, silicone, glass, or any other suitable material. The secondary lens 202 is then mounted to overlie the first lens 198 and contact the backplane 190 for support. An air gap 204 (or other low index of refraction material gap) creates an internal refractive interface that bends light towards the sides. The interface of the outer surface of the secondary lens 202 with air further bends the light to achieve the peak intensity within 50-80 degrees. The secondary lens 202 may directly contact the first lens 198; however, the shape of the secondary lens 202 would have to be changed to achieve the same wide-emitting pattern.
In another embodiment, the secondary lens 202 contacts and is supported by the submount 196 rather than the backplane 190.
The secondary lens 202 may be fixed to the backplane or the submount with an adhesive such as epoxy or may be affixed with a snap-tab connection.
By fixing the secondary lens 202 referenced to the submount, slightly better control over the light emission is achieved as compared to fixing the secondary lens 202 referenced to the backplane because the height of the LED and first lens 198 above the backplane may vary slightly with the mounting parameters.
The aspherical secondary lens 202 with the aspherical dome internal air gap is a simple design that is easily molded. The lens 202 is undercut near the backplane 190 to reflect light upward at the undercut surface so that light is not emitted downward toward the backplane 190. This avoids light rings and increases the backlight's light output.
In another embodiment, the surface of the secondary lens 202 contains microstructures, as described with respect to
The secondary lenses in
One way to form a sheet of ceramic phosphor is to sinter grains of the phosphor powder using heat and pressure. The percentage of the blue LED light passing through the plate is dependent on the density of the phosphor and the thickness of the plate, which can be precisely controlled. Another way to form a thin sheet of phosphor is to form a slurry of phosphor in a thin sheet and then dry the slurry. Forming such ceramic phosphor plates is described in U.S. patent publication 20050269582, entitled Luminescent Ceramic for a Light Emitting Diode, by Gerd Mueller et al., incorporated herein by reference.
A popular phosphor to use with a blue LED is a YAG:Ce phosphor (Yttrium Aluminum Garnet doped with about 2% Cerium), which is commercially available.
In
The backplate 212 and the mold 214 are then brought together so as to immerse the phosphor wafer 211 into the silicone 215. The backplate 212 and mold 214 are clamped together, a vacuum is created around the structure, and the silicone 215 is under compression. Any air bubbles in the liquid silicone are evacuated during this overmolding step. The silicone 215 is then cured by heat or UV. The backplate 212 and mold 214 are then separated, aided by the release film.
The resulting molded phosphor wafer is then sawed to form individual molded phosphor plates, where each plate is approximately the size of an LED. The phosphor-loaded silicone forms a lens over the phosphor plate. In one embodiment, the molded phosphor wafer is retained on the backplate 212 during the sawing process, and the saw blade only cuts through the wafer. This makes the plates easier to pick and place by an automated pick and place machine. In another embodiment, the molded wafer is removed from the backplate 212, then sawed.
In
In one embodiment, to be elaborated on later, the shape of the mold indention 213 is determined by computer modeling to compensate for the non-uniformity of the color temperature vs. angle of the light emitted by the LED/plate combination.
In
In another embodiment, the outer lens 234 is harder than the phosphor-loaded silicone 221. This results in a mechanically strong outer lens for protection as well as a smooth outer surface that is resistant to dust particles while reducing stress on the LED and interconnections.
The submount 226 is then diced to singulate the LED structures. The LEDs in the above example emit a warm white light, such as within 3000-4000K. Any other phosphors can be used for the phosphor plate and the phosphor in the silicone.
The color temperatures can be further controlled by binning the molded phosphor plates 218 in accordance with their color characteristics after a test. The LEDs 224 on the submount 226 are then tested and categorized in accordance to their color characteristics. The binned molded phosphor plates 218 are then selected for a particular LED to achieve a target color temperature.
In
The backplate 222 and the mold 230 are then brought together so as to immerse the plates 228 into the silicone 231. The backplate 222 and mold 230 are clamped together, a vacuum is created around the structure, and the silicone 231 is under compression. The silicone 231 is then cured by heat or UV. The backplate 222 and mold 230 are then separated, aided by the release film.
In
In one embodiment, to be elaborated on later, the shape of the mold indentions 229 is determined by computer modeling to compensate for the non-uniformity of the color temperature vs. angle of the light emitted by the LED/plate combination.
In
The submount 238 is then diced to singulate the LED structures. The LEDs in the above example emit a warm white light, such as within 3000-4000K. Any other phosphors can be used for the phosphor plate and the phosphor in the silicone. The advantages of binning and matching were described with respect to
In
In
In
In
In
In
The color temperature graph shown in
It would be very difficult to precisely form a phosphor coating that varies in thickness so that the blue light travels the same distance through the phosphor at all angles.
To compensate for this color vs. angle non-uniformity, a molded lens containing a substantially homogenous distribution of a compensating phosphor is used. In one example, a red phosphor is dispersed in liquid silicone in a mold, similar to mold 250 in
In
A hard outer lens 276 is then molded over the softer compensating lens 272. The lens 276 may be clear or contain a phosphor.
In
As shown in
The footprint of the molded phosphor lens 286 need not be rounded like the footprint of a hemispherical outer lens. The footprint of the phosphor lens 286 may be rectilinear to just cover the LED and TVS pair.
As in all embodiments, the outer lens may contain one or more phosphor types to achieve any color temperature, such as warm white.
Although an outer silicone lens may be simply molded over an inner silicone lens, it has been discovered that an intermediate plasma treatment of the inner lens increases the adhesion between the two lenses. The plasma treatment slightly etches and roughens the lens. Subjecting the inner lens to a plasma power of 200 Watts for a few minutes (e.g., 2-15 minutes) is sufficient to ensure the adhesion between the two silicone lenses is greater than the adhesion of the outer lens to the mold release film. The plasma power may be approximately 200-600 Watts. The plasma gas may be any suitable inert gas, such as argon, and the process may be performed in any suitable chamber that can create a plasma.
In
The arrangement, colors, and ratio of each color are not limited. For example, the group of LEDs could also include a white LED, or the group could include 2-3 red LEDs by themselves or along with one or more green and blue LEDS, or the group may be 2 white LEDs plus an amber LED.
In
In
In
A preformed Fresnel lens 318 is then affixed to the flat portion of the molded lens 316 by silicone glue 319, epoxy, or by other means. The Fresnel lens 318 has very fine features that collimate the light. The reason why the Fresnel lens cannot be directly formed in the molded lens 316 by a pattern in the mold is that the release film (which forms a 50 micron layer over the mold) cannot contour to such fine patterns in the mold. If the mold is formed of a non-stick substance and the release layer is not needed, then a Fresnel lens may be directly molded into the lens. The separate Fresnel lens 318 may be formed by stamping a softened plastic material or using other means. In one embodiment, the Fresnel lens 318 has a circular footprint.
A wall portion 320 of the molded lens 316 surrounds each Fresnel lens 318 and is approximately the same height as the Fresnel lens 318. This wall portion 320 has angled sides that reflect upward any light emitted from the sides of the Fresnel lens 318. Additionally, the wall portion 320 protects the Fresnel lens 318 from being bumped. Providing the molded lens with wall portions is optional, and the molded lens can be any shape that supports another lens on top.
The submount wafer 310 is then sawed along the saw lines 322 to singulated the collimated light sources. In one embodiment, the light sources of
The molded lens may also contain phosphor, as shown in
An excimer laser beam is then applied to the transparent growth substrate, which heats the GaN LED surface and disassociates the GaN at the surface to create gallium and nitrogen gas. The nitrogen expands to lift the sapphire substrate off the GaN LED, and the sapphire substrate is removed. Tremendous downward pressure is created during this process, and the underfill 348 mechanically supports the thin LED layers to prevent breakage of the LED. The underfill 348 also helps to conduct heat from the LED to the submount during operation of the LED.
A hard silicone lens 350, either clear or phosphor-loaded, is then molded over the LED using the techniques described herein. The underfill 348 prevents the liquid outer lens material in the mold from entering the voids. This reduces the thermal stress on the LED during operation, which otherwise may result in the LED lifting off from the submount. The underfill can be optimized to perform its function without concern over its optical properties.
In all embodiments described herein, an underfill silicone gel may be employed. Further, an LED emitting UV light may be used in place of the blue LEDs described herein, and a blue phosphor may be dispersed in a molded lens.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention.
Claims
1-12. (canceled)
13. A light emitting diode (LED) structure comprising:
- an LED emitting blue light or UV light on a submount;
- a substantially flat phosphor layer overlying the LED;
- a molded phosphor-loaded lens over the phosphor layer; and
- a clear lens, containing no phosphor, molded over the LED and phosphor-loaded lens.
14. The structure of claim 13 wherein the phosphor layer is a phosphor plate that is affixed to the LED.
15. The structure of claim 13 wherein the phosphor-loaded lens is affixed to the LED with the phosphor layer adjacent the LED.
16. The structure of claim 13 wherein the phosphor layer contains YAG phosphor and the phosphor in the phosphor-load lens comprises red phosphor.
17. The structure of claim 13 wherein the LED in combination with the phosphor layer has a color temperature vs. viewing angle, and wherein the phosphor-loaded lens is shaped to increase uniformity of the color temperature vs. viewing angle.
18. The structure of claim 13 wherein the phosphor layer is a phosphor layer conformally coating the LED.
19. The structure of claim 13 wherein the combination of light from the LED, the phosphor layer, and the phosphor-loaded lens produces white light.
20-22. (canceled)
23. A light emitting diode (LED) structure comprising:
- an LED emitting blue light or UV light on a submount;
- a molded first phosphor-loaded lens containing a first phosphor over the LED;
- a molded second phosphor-loaded lens containing a second phosphor over the first phosphor-loaded lens;
- a molded clear lens, containing no phosphor over the second phosphor-loaded lens.
24. The structure of claim 23 wherein the first phosphor is different from the second phosphor.
25. The structure of claim 23 wherein the LED in combination with the first phosphor-loaded lens has a color temperature vs. viewing angle, and wherein the second phosphor-loaded lens is shaped to increase uniformity of the color temperature vs. viewing angle.
26. A light emitting diode (LED) structure comprising:
- an LED on a submount along with one or more semiconductor dice mounted on the submount; and
- a single lens molded over the LED and the one or more semiconductor dice.
27. The structure of claim 26 further comprising a molded phosphor-loaded lens overlying the LED and the one or more semiconductor dice, where the single lens is molded over the phosphor-loaded lens.
28. The structure of claim 26 wherein the one or more semiconductor dice comprise one or more LEDs.
29. The structure of claim 26 wherein the one or more semiconductor dice comprise a plurality of LEDs emitting different colors.
30. The structure of claim 26 wherein the one or more semiconductor dice comprise a transient voltage suppressor.
31. The structure of claim 26 wherein the one or more semiconductor dice comprise a photodetector.
32. The structure of claim 26 wherein the single lens molded over the LED and the one or more semiconductor dice is not symmetrical about a central axis.
33. The structure of claim 26 wherein the single lens encapsulates the LED and the one or more semiconductor dice.
34. A light emitting diode (LED) structure comprising:
- an LED mounted on a substrate:
- a first lens molded over and encapsulating the LED, the lens having a substantially flat top; and
- a prefabricated second lens affixed to the substantially flat top of the first lens.
35. The structure of claim 34 wherein the second lens is a collimating lens.
36. The structure of claim 34 wherein the second lens is a Fresnel lens.
37. The structure of claim 34 wherein the first lens has wall portions surrounding the substantially flat top such that a top of the wall portions is substantially coplanar with a top of the second lens.
38. The structure of claim 37 wherein the wall portions are angled
- to reflect light from sides of the second lens away from the LED.
39. The structure of claim 34 wherein a surface of the second lens is approximately a same size as a surface of the LED.
40. The structure of claim 34 wherein the first lens contains phosphor and light from the LED energizes the phosphor and mixes with light generated by the phosphor.
41. The structure of claim 34 wherein the structure emits white light.
42. The structure of claim 41 wherein the structure is a flash in a camera.
43. The structure of claim 34 wherein the first lens comprises silicone.
44. A process for forming a light emitting diode (LED) structure comprising:
- mounting an LED on a submount, wherein at least a first electrode on the LED is bonded to at least a second electrode on a surface of the submount, a void existing between the LED and the surface of the submount;
- filling the void with an underfill material;
- providing a mold having an indention corresponding to a lens;
- filling the indention with a liquid lens material;
- after the step of filling, immersing the LED and the underfill material into the liquid lens material in the mold, the underfill preventing the liquid lens material from entering the void;
- curing the liquid lens material to encapsulate the LED and underfill material with a molded lens; and
- removing the LED with the molded lens from the mold.
45. The method of claim 44 wherein a transparent substrate forms a top surface of the LED, wherein a portion of the underfill material is disposed on side surfaces of the LED, including the substrate.
46-49. (canceled)
50. A light emitting diode (LED) structure comprising:
- an LED on a submount;
- a molded first lens over the LED, wherein the molded first lens has a plasma treated outer surface;
- a molded second lens formed directly over the first lens, wherein the plasma treated outer surface of the first lens increases adherence of the first lens to the second lens.
51. A process for forming a light emitting diode (LED) structure comprising:
- providing an arrangement of a plurality of LED dies mounted on a single submount substrate;
- providing a first mold having first indentions in an arrangement corresponding to the arrangement of the plurality of LED dies, each first indentation corresponding to outer dimensions of a first lens to be formed over each of the LED dies mounted on the submount substrate;
- aligning the submount substrate with respect to the first mold;
- molding first lenses, not containing a phosphor, directly over each of the LED dies using the first mold;
- providing a second mold having second indentions in an arrangement corresponding to the arrangement of the plurality of LED dies, each second indentation corresponding to outer dimensions of a second lens to be formed over each of the LED dies mounted on the submount substrate, dimensions of each second indention being larger than dimensions of each first indention;
- aligning the submount substrate with respect to the second mold; and
- molding second lenses, containing a phosphor, over each of the LED dies and first lenses using the second mold;
- whereby inner dimensions of the second lenses over the LED dies are defined by outer dimensions of the first lenses over the LED dies, such that identical misalignments of the submount substrate with respect to the first mold and the second mold, within a range, do not affect a thickness of the second lenses.
52. The process of claim 51 wherein molding clear first lenses, not containing a phosphor, over each of the LED dies using the first mold comprises:
- filling the first indentions with a first liquid lens material not containing a phosphor, prior to aligning the submount substrate with respect to the first mold;
- immersing all the LED dies simultaneously into the first liquid lens material in the first mold; and
- curing the first liquid lens material to form the first lens over each of the LED dies;
- and wherein molding second lenses, containing a phosphor, over each of the LED dies and first lenses using the second mold comprises:
- filling the second indentions with a second liquid lens material containing a phosphor, prior to aligning the submount substrate with respect to the second mold;
- immersing all the LED dies and first lenses simultaneously into the second liquid lens material in the second mold; and
- curing the second liquid lens material to form the second lens over each of the LED dies and over each of the first lenses.
53. The process of claim 51 further comprising dicing the substrate to form individual LED structures.
54. The process of claim 51 further comprising molding one or more additional lenses over the second lenses.
55. The process of claim 51 wherein the phosphor in the second lenses, in conjunction with light emitted by the LED dies, generates white light.
56. A light emitting diode (LED) structure comprising:
- an LED die mounted on a submount substrate:
- a first lens molded directly over the LED die using a first mold aligned to the substrate, the first lens containing no phosphor; and
- a second lens molded directly over the first lens using a second mold aligned to the substrate, the second lens containing a phosphor,
- whereby inner dimensions of the second lens over the LED die are defined by outer dimensions of the first lens over the LED die, such that identical misalignments of the substrate with respect to the first mold and the second mold, within a range, do not affect a thickness of the second lens.
Type: Application
Filed: Nov 15, 2010
Publication Date: Mar 10, 2011
Applicant: (EINDHOVEN)
Inventors: Gerd Mueller (San Jose, CA), Regina Mueller-Mach (San Jose, CA), Grigoriy Basin (San Francisco, CA), Robert Scott West (Morgan Hill, CA), Paul S. Martin (Pleasanton, CA), Tze-Sen Lim (Bayan Lepas), Stefan Eberle (Mountain View, CA)
Application Number: 12/945,962
International Classification: H01L 27/15 (20060101); H01L 33/58 (20100101); H01L 27/14 (20060101); H01L 23/12 (20060101);