High reflective board or substrate for LEDs

• US 9,105,824 B2
• Filed: 02/10/2012
• Issued: 08/11/2015
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Heikman, Sten, Yao, Zhimin Jamie, Ibbetson, James, Zhang, Fan
• Primary Examiner(s): PERT, EVAN T
• Application Number:
  US13/370,696
• Publication Number:
  US 20120199843A1
• Time in Patent Office: 1,278 Days
• Field of Search: 257/98
• US Class Current: 1/1
• 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 comprising a circuit layer, said circuit layer comprising a plurality of elements;

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

a light emitting diode (LED) mounted to said circuit layer, said reflective coating being reflective to the light emitted by said light emitting diode, wherein said reflective coating physically contacts at least a portion of one of said plurality of elements.

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 2, 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 plurality of elements comprises 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 layer and a bottom layer that are in thermal contact and electrical contact, wherein said top and bottom layers cover different surface areas 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 9, wherein the top layer of said circuit layer covers less surface area than the bottom layer of said circuit layer.

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

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 a top surface of said reflective coating is below a 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. A light emitting device, comprising:

a submount comprising a circuit layer, said circuit layer comprising a plurality of elements;

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

a light emitting diode (LED) mounted to said circuit layer, said reflective coating being reflective to the light emitted by said light emitting diode, wherein said reflective coating further comprises a conversion material.

19. A light emitting device, comprising:

a submount comprising a circuit layer, said circuit layer comprising a plurality of elements;

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

a light emitting diode (LED) flip-chip mounted to said circuit layer, said LED spanning a space between at least two of said plurality of elements, a top surface of said reflective coating below said LED being lower than a surface of said circuit layer, wherein said reflective coating physically contacts at least a portion of one of said plurality of elements.

20. The light emitting device of claim 19, wherein the thickness of said reflective coating below said LED is less than the thickness of said circuit layer below said LED.

21. A light emitting device, comprising:

a submount comprising a circuit layer, said circuit layer comprising a plurality of elements, a top surface of said circuit layer having a smaller surface area than a bottom surface of said circuit layer;

a reflective coating between at least some of the plurality of elements of said circuit layer, wherein said reflective coating physically contacts at least a portion of one of said plurality of elements; and

a light emitting diode (LED) mounted to said circuit layer.

22. The device of claim 21, wherein said reflective coating is reflective to the light emitted by said LED.

23. The device of claim 21, 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.

24. The device of claim 21, wherein said reflective coating comprises a carrier material with scattering particles having a different index of refraction than said carrier material.

25. A multiple element light emitting device, comprising:

a submount comprising a circuit layer, said circuit layer comprising a plurality of elements;

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

a plurality of light emitting diodes (LEDs) mounted to said circuit layer, wherein at least some of said plurality of LEDs have different geometries, said reflective coating being reflective to the light emitted by at least some of said plurality of LEDs, wherein said reflective coating physically contacts at least a portion of one of said plurality of elements.

26. The device of claim 25, wherein at least one of said plurality of LEDs has a lateral geometry.

27. The device of claim 25, wherein at least one of said plurality of LEDs is directly attached to said circuit layer.

28. The device of claim 25, wherein at least one of said plurality of LEDs has a vertical geometry.

29. The device of claim 25, wherein at least one of said plurality of LED is attached to said circuit layer with a wire bond.

30. The device of claim 25, further comprising a lens over at least one of said plurality of LEDs.

31. The device of claim 25, 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.

32. The device of claim 25, wherein said reflective coating comprises a carrier material with scattering particles having a different index of refraction than said carrier material.

33. The device of claim 25, wherein said circuit layer comprises extension portions not covered by said plurality of LEDs.

34. A multiple element light emitting device, comprising:

a submount comprising a circuit layer, said circuit layer comprising a plurality of elements;

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

a reflective coating between at least some of said plurality of elements of said circuit layer, wherein said reflective coating physically contacts at least a portion of one of said plurality of elements.

35. The device of claim 34, wherein said reflective coating is reflective to the light emitted by said plurality of LEDs.

36. The device of claim 34, wherein at least some of said plurality of LEDs have different geometries.

37. The device of claim 34, further comprising a lens over at least one of said plurality of LEDs.

38. The device of claim 34, 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.

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

40. The device of claim 34, wherein said circuit layer comprises extension portions not covered by said plurality of LEDs.

41. The device of claim 34, wherein at least some of said plurality of LEDs comprise a Group-III nitride material.

42. The device of claim 34, wherein at least some of said plurality of LEDs comprise gallium nitride (GaN).