High reflective substrate of light emitting devices with improved light output

• US 9,012,938 B2
• Filed: 04/09/2010
• Issued: 04/21/2015
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Yuan, Thomas Cheng-Hsin, Keller, Bernd, Le Toquin, Ronan, Lowes, Theodore
• Primary Examiner(s): Mandala, Victor A
• Application Number:
  US12/757,179
• Publication Number:
  US 20110248287A1
• Time in Patent Office: 1,838 Days
• Field of Search: 257/88, 257/98, 257/99, 257/100, 257/E33.059, 257/E33.061, 257/E33.072
• US Class Current: 257/98
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

Apparatuses and methods for producing light emitting devices maximizing luminous flux output are disclosed. In one possible embodiment, a light emitting device comprises a substrate and a reflective layer at least partially covering the substrate. The reflective layer is non-yellowing, and may be substantially light transparent. One or more light emitting diode (LED) chips are disposed on the substrate. The light emitting device may emit white light. The reflective layer may comprise a silicone carrier with light reflective particles dispersed in the silicone carrier. A light diffusion lens may also be disposed on the substrate and surrounding the LED chips. Furthermore, one or more microspheres, light scattering particles, and/or phosphor particles may be dispersed in the lens. In one possible method for producing a light emitting device, a substrate is provided. One or more LED chips are coupled with the substrate, and a high reflective, non-yellowing coating is applied on at least a portion of the top surface of the substrate. The coating comprises a carrier with reflective particles dispersed throughout.

Claims

1. A light emitting device, comprising:

a substrate;

a reflective coating comprising a transparent carrier at least partially covering said substrate, with said reflective coating being resistant to discoloration, wherein said reflective coating redirects incident light towards a lens; and

one or more light emitting diode (LED) chips on said substrate, wherein said reflective coating is configured such that the bottom portion of said one or more LED chips remains uncovered by said reflective coating, wherein said reflective coating covers less than all of at least one sidewall of said one or more LED chips.

2. The device of claim 1, wherein said reflective coating is resistant to yellowing.

3. The device of claim 1, wherein said substrate comprises a printed circuit board.

4. The device of claim 1, wherein said reflective coating comprises a carrier, with light reflective particles in said carrier.

5. The device of claim 4, wherein said carrier comprises one or more of silicone, plastic, glass, or a polymeric matrix.

6. The device of claim 4, wherein said light reflective particles comprise one or more of titanium dioxide or aluminum oxide.

7. The device of claim 4, wherein said light reflective particles comprise a reflective index different from the reflective index of said carrier.

8. The device of claim 1, wherein said reflective coating is light transparent, with said reflective coating being non-discoloring and non-degrading over prolonged use, or exposure to blue light.

9. The device of claim 1, wherein said reflective coating covers said substrate outside the perimeter of said LED chips.

10. The device of claim 9, wherein said reflective coating is on said substrate between each of said LED chips.

11. The device of claim 1, further comprising a light diffusing lens on said substrate and LED chips, with said light diffusing lens comprising one or more of light scattering particles, hollow microspheres, or phosphor particles.

12. The device of claim 11, wherein said reflective coating redirects light that is scattered or back-reflected from said light scattering particles, hollow microspheres, or phosphor particles such that said light is effectively emitted from said device, increasing the light output of said device.

13. The device of claim 11, wherein said light diffusing lens comprises one or more of silicone, glass, or plastic.

14. The device of claim 1, wherein said light emitting device emits red light, green light, blue light, yellow light, white light, or any combination thereof.

15. A light emitting device, comprising:

a substrate;

a reflective coating at least partially covering said substrate, with said reflective coating being resistant to discoloration;

one or more light emitting diode (LED) chips on said substrate, wherein said light emitting device comprises an LED lamp; and

one or more walls with an interior surface in the light emission paths of said LED chips, said interior surfaces coated with said reflective coating.

16. A light emitting device, comprising:

a substrate;

a stable reflective coating at least partially covering said substrate, said reflective coating comprising a silicone carrier and being resistant to discoloration, wherein said reflective coating redirects incident light towards a light diffusion lens;

light reflective particles in said carrier;

one or more light emitting diode (LED) chips on said substrate, wherein said stable reflective coating is configured such that the bottom portion of said one or more LED chips remains uncovered by said stable reflective coating; and

said light diffusion lens on said substrate and over said LED chips;

wherein said light diffusion lens comprises at least one of the group consisting of scattering particles, air bubbles, or microspheres.

17. The device of claim 16, wherein said coating is resistant to yellowing through use.

18. The device of claim 16, wherein said light emitting reflective particles comprise one or more of titanium dioxide or aluminum oxide.

19. The device of claim 16, wherein said reflective coating covers said substrate outside the perimeter of said LED chips or is on said substrate between each of said LED chips and outside the perimeter of said LED chips.

20. The device of claim 16, wherein said light diffusion lens comprises one or more of light scattering particles, phosphor particles, or hollow microspheres.

21. The device of claim 16, wherein said light diffusion lens comprises one or more of silicone, plastic, or glass.

22. A light emitting device, comprising:

a substrate;

one or more light emitting diode (LED) chips on said substrate;

a light diffusion lens on said substrate and surrounding said LED chips;

one or more microspheres in said light diffusion lens; and

a stable reflective coating at least partially covering said substrate, said reflective coating resistant to discoloration, wherein said reflective coating redirects incident light towards the light diffusion lens, wherein said stable reflective coating is configured such that the bottom portion of said one or more LED chips remains uncovered by said stable reflective coating.

23. The device of claim 22, wherein said reflective coating comprises a carrier which is transparent to light from at least one of said LED chips, and a reflective material.

24. The device of claim 22, wherein said reflective coating at least partially covers said substrate.

26. The device of claim 22, wherein said reflective coating comprises a silicone carrier, with one or more of titanium dioxide or aluminum particles in said carrier.

27. The device of claim 22, wherein said light diffusion lens further comprises one or more of light scattering particles or phosphor particles.

25. A light emitting device, comprising:

a substrate;

one or more light emitting diode (LED) chips on said substrate;

a light diffusion lens on said substrate and surrounding said LED chips;

one or more microspheres in said light diffusion lens, wherein said microspheres comprise hollow glass, said microspheres enhancing the light scattering and mixing of light emitted by said LED chips; and

a stable reflective coating at least partially covering said substrate, wherein said reflective coating redirects incident light towards the light diffusion lens, wherein said stable reflective coating is configured such that the bottom portion of said one or more LED chips remains uncovered by said stable reflective coating.

28. A method for producing a light emitting device, said method comprising:

providing a substrate;

mounting one or more light emitting diode (LED) chips to said substrate; and

applying a reflective, discoloration resistant coating on at least a portion of the top surface of said substrate such that the bottom portion of said one or more LED chips remains uncovered by said stable reflective coating, said coating comprising a transparent carrier with reflective particles in said carrier, wherein said reflective coating redirects incident light towards a lens.

29. The method of claim 28, further comprising disposing a light diffusion lens on said substrate and LED chips, said light diffusion lens comprising one or more of scattering particles, hollow microspheres, or phosphor particles.

30. The method of claim 28, wherein said carrier comprises one or more of silicone, plastic, or glass, and said reflective particles comprise one or more of titanium dioxide or aluminum oxide.

31. The method of claim 28, further comprising applying said coating on said substrate outside the perimeter of said LED chips or between each of said LED chips as well as outside the perimeter of said LED chips.

32. The method of claim 28, further comprising applying said coating on said substrate by one or more of the following methods:

printing, brushing on, or utilizing a dispensing mechanism.