Light emitting device with a thermal insulating and refractive index matching material

• US 8,134,292 B2
• Filed: 01/13/2005
• Issued: 03/13/2012
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: LED Engin, Inc. (Ams-Osram AG)
• Original Assignee: Ledengin, Inc. (Ams-Osram AG)
• Inventors: Yan, Xiantao
• Primary Examiner(s): Won, Bumsuk
• Application Number:
  US11/036,559
• Publication Number:
  US 20060091788A1
• Time in Patent Office: 2,616 Days
• Field of Search: 313498-512
• US Class Current: 313/512
• 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 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin

Abstract

A light emitting device has a light emitting diode (LED) encapsulated by an encapsulant member. The encapsulant member includes a luminescent material, such as a phosphor, and a thermal insulating material. The thermal insulating material effectively insulates the luminescent material from the heat generated by the LED. A thermal conducting material is desirably placed in thermal contact with a back side of the LED to assist heat dissipation. The encapsulant member may be formed in two separate layers with the luminescent material forming a luminescent layer, and the thermal insulating material forming a thermal insulation layer disposed between the luminescent layer and the LED.

Claims

1. A light emitting device comprising:

a light emitting diode having a top surface; and

an encapsulant member covering the top surface of the light emitting diode, the encapsulant member including a luminescent layer and a thermal insulation layer,

the luminescent layer including a luminescent material separated from the light emitting diode by the thermal insulation layer,

the thermal insulation layer formed from a thermal insulating material and not including luminescent material, the thermal insulation layer material configured to prevent heat from being transferred from the light emitting diode to the luminescent layer,

the thermal insulation layer having an index of refraction of at least 1.6.

2. The light emitting device of claim 1 wherein the luminescent layer is conformally disposed over an outer surface of the thermal insulation layer.

3. The light emitting device of claim 1 wherein the thermal insulating material is transparent to a wavelength emitted by the light emitting diode.

4. The light emitting device of claim 1 wherein the thermal insulating material is transparent to a wavelength in a range of about 200 nm-2000 nm.

5. The light emitting device of claim 1 wherein the thermal insulating material comprises a polymer.

6. The light emitting device of claim 1 wherein the thermal insulating material comprises a polyimide.

7. The light emitting device of claim 1 wherein the thermal insulating material comprises a ceramic.

8. The light emitting device of claim 1 wherein the thermal insulating material comprises a glass.

9. The light emitting device of claim 1 wherein the thermal insulating material has a thermal conductivity of no more than 0.5 W/m°

K.

10. The light emitting device of claim 1 wherein the thermal insulating material has a thermal conductivity of no more than 0.15 W/m°

K.

11. The light emitting device of claim 1 wherein the thermal insulating material has a glass transition temperature above 200 °

C.

12. The light emitting device of claim 1 wherein the thermal insulating material has a glass transition temperature above 250 °

C.

13. The light emitting device of claim 1 wherein the thermal insulating material has a refractive index greater than 1.8.

14. The light emitting device of claim 1 wherein the thermal insulating material has a refractive index in a range of 1.7-2.1.

15. The light emitting device of claim 1 wherein the thermal insulating material has a coefficient of thermal expansion no greater than 100 ppm/°

C.

16. The light emitting device of claim 1 wherein the thermal insulating material has a coefficient of thermal expansion no greater than 30 ppm/°

C.

17. The light emitting device of claim 1 wherein the light emitting diode is capable of producing an output power of about 1 watt or higher.

18. The light emitting device of claim 1 wherein the light emitting diode is capable of producing an output power of about 5 watts or higher.

19. The light emitting device of claim 1 wherein the light emitting diode is capable of producing an output power of about 10 watts or higher.

20. The light emitting device of claim 1 wherein the light emitting diode is capable of producing an output power of about 15 watts or higher.

21. The light emitting device of claim 1 wherein the light emitting diode is capable of producing a blue light.

22. The light emitting device of claim 21 wherein the luminescent material produces a white light when excited by the blue light.

23. The light emitting device of claim 1 wherein the luminescent material includes a phosphor.

24. The light emitting device of claim 1 wherein the luminescent material includes an yttrium aluminum garnet material.

25. The light emitting device of claim 1 wherein the luminescent material includes a terbium aluminum garnet material.

26. The light emitting device of claim 1 wherein the luminescent material includes a ZnSeS+material.

27. The light emitting device of claim 1 wherein the luminescent material includes a silicon aluminum oxynitride material.

28. The light emitting device of claim 1 further comprising one or more additional light emitting diodes.

29. The light emitting device of claim 1 further comprising:

a thermal conducting material layer in direct thermal contact with a back side of the light emitting diode, the thermal conducting material layer being electrically non-conducting and having a thermal conductivity greater than 200 W/m°

K.

30. The light emitting device of claim 29 wherein the thermal conducting material layer includes a ceramic.

31. The light emitting device of claim 29 wherein the thermal conducting material layer has a thickness in a range of 0.2mm-0.4mm.

32. The light emitting device of claim 29 wherein the thermal conducting material layer includes aluminum nitride.

33. The light emitting device of claim 29 wherein the thermal conducting material layer includes aluminum oxide.