LED with Phosphor Tile and Overmolded Phosphor in Lens

• US 20080048200A1
• Filed: 02/26/2007
• Published: 02/28/2008
• Est. Priority Date: 11/15/2004
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Lim, Tze-Sen, West, Robert, Mueller, Gerd, Mueller-Mach, Regina, Basin, Grigoriy, Martin, Paul, Eberle, Stefan
• Granted Patent: US 7,858,408 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: B29C 41/14 Dipping a core B29C41/10 takes precedence
• CPC Class Codes: B29C 41/20 incorporating preformed parts or layers, e.g. moulding inserts or for coating articles
• CPC Class Codes: B29C 41/22 Making multilayered or multicoloured articles
• CPC Class Codes: B29K 2995/0031 Refractive
• CPC Class Codes: B29L 2011/00 Optical elements, e.g. lenses, prisms
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/81 using a bump connector
• CPC Class Codes: H01L 2224/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01023 : Vanadium [V]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01055 : Cesium [Cs]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/12041 : LED
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/1815 : Shape
• CPC Class Codes: H01L 2924/207 : Diameter ranges
• CPC Class Codes: H01L 2924/351 : Thermal stress
• CPC Class Codes: H01L 2933/0041 : relating to wavelength conversion elements
• CPC Class Codes: H01L 33/504 : Elements with two or more wavelength conversion materials
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/54 : having a particular shape
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin

Abstract

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.

Claims

1. A process for forming a light emitting diode (LED) structure comprising:

providing an LED emitting blue light or UV light on a submount;

providing a substantially flat phosphor layer;

providing a mold having an indention corresponding to an intermediate lens;

filling the indention with a liquid lens material containing a phosphor;

after the step of filling, immersing at least the phosphor layer into the liquid lens material in the mold;

curing the liquid lens material to form a phosphor-loaded lens over the phosphor layer; and

providing the phosphor layer over the LED.

2. The process of claim 1 wherein the phosphor layer is a phosphor plate that is affixed to the LED prior to the step of immersing at least the phosphor layer into the liquid lens material, wherein the step of immersing at least the phosphor layer into the liquid lens material comprises immersing the LED and the phosphor plate affixed to the LED into the liquid lens material to encapsulate the LED and phosphor plate.

3. The process of claim 1 wherein the phosphor layer is a phosphor plate that is affixed to the LED after the step of immersing at least the phosphor layer into the liquid lens material, wherein the phosphor-loaded lens containing the phosphor layer is affixed to the LED after the phosphor-loaded lens is formed.

4. The process of claim 3 wherein the phosphor-loaded lens containing the phosphor plate is affixed to the LED with the phosphor plate adjacent the LED.

5. The process of claim 3 wherein the phosphor-loaded lens containing the phosphor plate is affixed to the LED with the lens adjacent the LED.

6. The process of claim 1 further comprising molding a clear lens over the phosphor-loaded lens and the LED by immersing the phosphor-loaded lens and the LED in a liquid lens material in a mold indention and then curing the liquid lens material.

7. The process of claim 1 wherein the phosphor layer contains YAG phosphor and the phosphor in the phosphor-load lens comprises red phosphor.

8. The process of claim 1 wherein the phosphor layer is a phosphor plate that is affixed to a backplate when immersed in the liquid lens material.

9. The process of claim 1 further comprising determining a color temperature vs. viewing angle of the LED with the phosphor layer affixed to it, and then shaping the mold indention to increase uniformity of the color temperature vs. viewing angle.

10. The process of claim 1 wherein the phosphor layer is a phosphor layer conformally coating the LED prior to the step of immersing at least the phosphor layer into the liquid lens material.

11. The process of claim 1 wherein the combination of light from the LED, the phosphor layer, and the phosphor-loaded lens produces white light.

12. The process of claim 1 wherein the LED is mounted on a submount along with a plurality of identical LEDs, wherein the step of immersing at least the phosphor layer into the liquid lens material in the mold comprises immersing all the LEDs on the submount into the liquid lens material in an associated mold indentation at the same time.

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. A process for forming a light emitting diode (LED) structure comprising:

providing an LED emitting blue light or UV light on a submount;

molding a phosphor-loaded lens over the LED by a process comprising;

providing a mold having an indention corresponding to an intermediate lens;

filling the indention with a liquid lens material containing a phosphor;

after the step of filling, immersing at the LED into the liquid lens material in the mold; and

curing the liquid lens material to form a phosphor-loaded lens over the LED; and

molding a clear lens over the phosphor-loaded lens.

21. The process of claim 20 wherein the phosphor-loaded lens is a first phosphor-loaded lens containing a first phosphor, the process further comprising molding a second phosphor-loaded lens over the first phosphor-loaded lens, the second phosphor-loaded lens containing a second phosphor different from the first phosphor.

22. The process of claim 21 further comprising determining a color temperature vs. viewing angle of the LED with the first phosphor-loaded lens, and then molding the second phosphor-loaded lens to increase uniformity of the color temperature vs. viewing angle.

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. A process for forming a light emitting diode (LED) structure comprising:

providing an LED on a submount;

providing a first mold having a first indention with a shape corresponding to a first lens;

filling the first indention with a first liquid lens material;

after the step of filling, immersing the LED into the first liquid lens material in the first mold;

curing the first liquid lens material to form the first lens over the LED;

removing the LED with the first lens from the first mold;

plasma treating the first lens;

providing a second mold having a second indention with a shape corresponding to a second lens;

filling the second indention with a second liquid lens material;

after the step of filling the second indentation, immersing the LED and first lens into the second liquid lens material in the second mold;

curing the second liquid lens material to form the second lens over the LED, wherein the step of plasma treating increases adherence of the first lens to the second lens; and

removing the LED with the first lens and second lens from the second mold.

47. The process of claim 46 wherein the first lens material is the same as the second lens material.

48. The process of claim 46 wherein the first lens contains phosphor.

49. The process of claim 46 wherein plasma treating comprises plasma treating the first lens at between approximately 200-600 Watts to etch the first lens.

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.