HIGH REFLECTIVE BOARD OR SUBSTRATE FOR LEDS

• US 20120199843A1
• Filed: 02/10/2012
• Published: 08/09/2012
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: HEIKMAN, Sten, IBBETSON, James, YAO, Zhimin Jamie, ZHANG, Fan
• Granted Patent: US 9,105,824 B2
• Time in Patent Office: Days
• US Class Current: 257/76
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 33/54 having a particular shape
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Light emitting devices and methods are disclosed that provide improved light output. The devices have an LED mounted to a substrate, board or submount characterized by improved reflectivity, which reduces the absorption of LED light. This increases the amount of light that can emit from the LED device. The LED devices also exhibit improved emission characteristics by having a reflective coating on the submount that is substantially non-yellowing. One embodiment of a light emitting device according to the present invention comprises a submount having a circuit layer. A reflective coating is included between at least some of the elements of the circuit layer. A light emitting diode mounted to the circuit layer, the reflective coating being reflective to the light emitted by the light emitting diode. In some embodiments, the reflective coating comprises a carrier with scattering particles having a different index of refraction than said carrier material.

Claims

1. A light emitting device, comprising:

a submount having a circuit layer;

a reflective coating between at least some of the elements of said circuit layer; and

a light emitting diode mounted to said circuit layer, said reflective coating being reflective to the light emitted by said light emitting diode.

2. The device of claim 1, wherein said reflective coating comprises a carrier material with scattering particles having a different index of refraction than said carrier material.

3. The device of claim 1, wherein said carrier material comprises silicone or glass.

4. The device of claim 1, wherein said submount comprises a dielectric layer, said circuit layer and reflective coating on said dielectric layer.

5. The device of claim 1, wherein said submount comprises a metal core board.

6. The device of claim 1, wherein said circuit layer comprises elements from the list comprising conductive traces, die attach pads and wire bond pads.

7. The device of claim 1, wherein said LED is wire bonded to said circuit layer.

8. The device of claim 1, wherein said LED is flip-chip mounted to said circuit layer.

9. The device of claim 1, wherein said circuit layer comprises a top and a bottom layers that are in thermal contact and electrical contact, wherein said top and bottom layers cover different surface area on said submount.

10. The device of claim 9, wherein said bottom layer covers more surface area than said top layer.

11. The device of claim 1, wherein the top surface of said circuit layer covers less surface area than the bottom surface of said circuit layer.

12. The device of claim 1, wherein said circuit layer comprises extension portions not covered by said LEDs.

13. The device of claim 1, wherein at least one portion of said reflective coating is thinner than the circuit layer.

14. The device of claim 1, wherein at least a portion of the top surface of said reflective layer is below the top surface of said circuit layer.

15. The device of claim 1, wherein said reflective coating being substantially non-discoloring and non-degrading over time, prolonged use, or exposure to blue light.

16. The device of claim 1, further comprising a lens.

17. The device of claim 1, further comprising a reflective cup.

18. The device of claim 1, wherein said reflective coating further comprises a conversion material.

19. A method for fabricating an LED device, comprising:

providing a submount with a circuit layer;

applying a reflective coating to said submount over said circuit layer, and in spaces between said circuit layer elements; and

removing said reflective coating to top surface of said circuit layer.

20. The method of claim 19, further comprising removing a portion of said reflective coating so that its top surface is below the top surface of said circuit layer.

21. The method of claim 20, wherein said removing of a portion of said reflective coating comprises etching said reflective coating.

22. The method of claim 19, further comprising applying a reflective finish to said circuit layer prior to applying said reflective coating.

23. The method of claim 19, further comprising applying a final finish or coating to said circuit layer following said removal of said reflective coating to said top surface.

24. The method of claim 19, further comprising additional removal of said reflective coating so that the circuit layer is thicker than said reflective coating.

25. The method of claim 19, wherein said removing of said reflective coating comprises grinding or polishing or sand belting of said reflective coating.

26. The method of claim 19, further comprising cleaning of said circuit layer and said reflective coating following removal of said reflective coating.

27. The method of claim 19, further comprising polishing of circuit layer following removal of said reflective coating.

28. The method of claim 19, further comprising mounting of an LED to said submount.

29. A light emitting device, comprising:

a submount having a circuit layer;

a reflective coating between at least some of the elements of said circuit layer; and

a light emitting diode flip-chip mounted to said circuit layer, said LED spanning the space between at least two of said circuit layer elements, the top surface of said reflective coating below said LED being lower than the surface of said circuit layer.

30. The light emitting device of claim 29, wherein the thickness of said reflective coating below said LED is less than the thickness of said circuit layer below said LED.

31. A light emitting device, comprising:

a submount having a circuit layer, the top surface of said circuit layer having a smaller surface area than the bottom surface of said circuit layer;

a reflective coating between at least some of the elements of said circuit layer; and

a light emitting diode mounted to said circuit layer.

32. The device of claim 31, wherein said reflective coating is reflective to the light emitted by said LED.

33. The device of claim 31, wherein said circuit layer comprises a top circuit layer and a bottom circuit layer, wherein the top circuit layer covers less surface area than said bottom circuit layer.

34. The device of claim 31, wherein said reflective coating comprises a carrier material with scattering particles having a different index of refraction than said carrier material.

35. A multiple element light emitting device, comprising:

a submount having a circuit layer;

a reflective coating between at least some of the elements of said circuit layer; and

a plurality of light emitting diodes mounted to said circuit layer, wherein at least some of said light emitting diodes have different geometries, said reflective coating being reflective to the light emitted by at least some of said light emitting diodes.

36. The device of claim 35, wherein at least one of said LEDs has a lateral geometry.

37. The device of claim 35, wherein at least one of said LEDs is directly attached to said circuit layer.

38. The device of claim 35, wherein at least one of said LEDs has a vertical geometry.

39. The device of claim 35, wherein at least one of said LED is attached to said circuit layer with a wire bond.

40. The device of claim 35, further comprising a lens over at least one of said LEDs.

41. The device of claim 35, wherein said circuit layer comprises a top circuit layer and a bottom circuit layer, wherein the top circuit layer covers less surface area than said bottom circuit layer.

42. The device of claim 35, wherein said reflective coating comprises a carrier material with scattering particles having a different index of refraction than said carrier material.

43. The device of claim 35, wherein said circuit layer comprises extension portions not covered by said LEDs.

44. A multiple element light emitting device, comprising:

a submount having a circuit layer; and

a plurality of light emitting diodes and electrically connected to said circuit layer, wherein at least one of said light emitting diodes are electrically connected by a wire bond to said circuit layer, and at least one of said LEDs directly attached to said circuit layer.

45. The device of claim 44, further comprising a reflective coating between at least some elements of said circuit layer.

46. The device of claim 45, wherein said reflective layer is reflective to the light emitted by said light emitting diodes.

47. The device of claim 44, wherein at least some of said LEDs have different geometries.

48. The device of claim 44, further comprising a lens over at least one of said LEDs.

49. The device of claim 44, wherein said circuit layer comprises a top circuit layer and a bottom circuit layer, wherein the top circuit layer covers less surface area than said bottom circuit layer.

50. The device of claim 44, wherein said reflective coating comprises a carrier material with scattering particles having a different index of refraction than said carrier material.

51. The device of claim 44, wherein said circuit layer comprises extension portions not covered by said LEDs.

52. The device of claim 44, wherein at least some of said LEDs comprise a Group-III nitride material.

53. The device of claim 44, wherein at least some of said LEDs comprise gallium nitride (GaN).