High powered light emitter packages with compact optics

• US 20040227149A1
• Filed: 04/29/2004
• Published: 11/18/2004
• Est. Priority Date: 04/30/2003
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Keller, Bernd, Bharathan, Jayesh
• Granted Patent: US 9,666,772 B2
• Time in Patent Office: Days
• US Class Current: 257/100
• CPC Class Codes: H01L 2224/48091 Arched
• 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 2924/00014 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 2924/12044 OLED
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/641 characterized by the materials

Abstract

A light emitter includes a planar supporting surface, a light source positioned on the spreader region, and an encapsulant positioned on the spreader region to surround the light source. Except where constrained by adhesion to the planar supporting surface, the encapsulant is capable of expanding and contracting in response to a change in temperature so that forces caused by differences in the coefficient of thermal expansion between the different components is minimized. One or more reflective elements can be positioned proximate to the light source to increase the light emitting efficiency of the light emitter. The reflective elements can include the a reflective layer on the spreader region and/or a reflective layer on a portion of the encapsulant.

Claims

1. A light emitter, comprising:

a substantially planar supporting surface;

a solid state light source positioned on said supporting surface; and

an encapsulant positioned on said supporting surface surrounding said light source, said encapsulant being capable of expanding and contracting in response to a change in temperature and constrained only by adhesion to said planar supporting surface.

2. The emitter of claim 1, further comprising a reflective element integrated with at least one of said supporting surface and said encapsulant.

3. The emitter of claim 1, wherein a surface of said light source is adjacent to said supporting surface, said encapsulant covering all other surfaces of said light source.

4. The emitter of claim 1, wherein said encapsulant hermetically seals said light source, said hermetic seal remaining unbroken with the change in temperature.

5. The emitter of claim 1, further comprising a barrier region positioned adjacent to said supporting surface at the base of said encapsulant, said barrier region forming a seal between said surface and said encapsulant.

6. The emitter of claim 1, wherein said supporting surface is planar so that expansion and contraction of said encapsulant is constrained only at said supporting surface.

7. The emitter of claim 1, wherein said supporting surface is reflective to the light emitted by said light source.

8. The emitter of claim 1, wherein said encapsulant is shaped around its base to provide an angled surface that reflects some of the light emitted from said light source.

9. The emitter of claim 8, wherein said encapsulant is shaped so that said reflected light flows through a focusing surface of said encapsulant.

10. The emitter of claim 8, wherein said angled surface includes a reflective coating which is reflective to said light emitted by said light source.

11. The emitter of claim 1, wherein said supporting structure comprises a highly thermally conductive spreader region to draw heat away from said light source.

12. The emitter of claim 1, wherein said light source comprises a light emitting diode.

13. A light emitter, comprising:

a heat spreader;

a light source positioned in thermal contact with a substantially planar surface of said heat spreader with said heat spreader providing support for said light source;

an encapsulant positioned to surround said light source, said encapsulant being capable of expanding and/or contracting in response to a change in temperature constrained only be adhesion to said planar surface; and

a first reflective element positioned to reflect light from said light source, said reflective element being integrated with at least one of said heat spreader and said encapsulant.

14. The emitter of claim 13, wherein said first reflective element includes an angled surface on the base of said encapsulant, said angled surface being capable of reflecting light from said light source to increase the light emitting efficiency of said emitter.

15. The emitter of claim 14, further comprising a second reflective element on said angled surface.

16. The emitter of claim 13, wherein said encapsulant is one of bullet shaped, concave shaped, and mushroom shaped.

17. The emitter of claim 13, wherein said encapsulant includes a second reflective element positioned to increase the reflectivity of said first reflective element.

18. The emitter of claim 17, wherein said second reflective element includes at least one of silver (Ag), aluminum (Al), titanium oxide (TiO), white resin, and another material region reflective at the wavelengths of interest.

19. The emitter of claim 13, wherein said encapsulant includes a preformed lens having a cavity in its base, said light source being positioned in said cavity.

20. The emitter of claim 19, further comprising a bonding material which fills the space in said cavity and holds said lens to said heat spreader, the index of refraction of said bonding material being chosen to obtain a desired light emitting efficiency.

21. The emitter of claim 20, wherein said bonding material includes at least one of epoxy, glue, silicone gel, and another material which has an index of refraction chosen to increase the light emitting efficiency of said emitter.

22. The emitter of claim 20, wherein said bonding material is chosen to compensate for differences in the coefficient of thermal expansion between said encapsulant, light source, and/or heat spreader.

23. The emitter of claim 13, wherein said heat spreader includes at least one of copper (Cu), aluminum (Al), aluminum nitride (AlN), aluminum oxide (AlO), silicon (Si), silicon carbide (SiC) and another high thermal conductivity material which can dissipate heat away from said light source.

24. The emitter of claim 13, wherein said first reflective element includes the surface of said heat spreader.

25. The emitter of claim 24, wherein said the surface of said heat spreader includes at least one of aluminum (Al), silver (Ag), and another material reflective at the wavelengths of interest.

26. The emitter of claim 13, wherein further including a barrier region positioned proximate to said first reflective element, said barrier region providing a hermetic seal between said encapsulant and heat spreader.

27. An optical display, comprising:

a heat spreader with a substantially planar surface;

a plurality of light emitters positioned on said substantially planar surface, each light emitter comprising

a light source positioned in thermal contact with said heat spreader;

an encapsulant positioned on said heat spreader to surround said light source, said encapsulant being capable of expanding and contracting in response to a change in temperature, constrained only by adhesion to said substantially planar surface; and

at least one reflective element positioned on said heat spreader and/or one or more encapsulants to increase the light emitting efficiency of said display.

28. A method of fabricating a light emitter, comprising:

providing a substantially planar supporting surface;

providing a light source positioned on said planar supporting surface; and

providing an encapsulant positioned on said supporting surface and over said light source so that said encapsulant can expand and contract with changes in temperature, constrained only by adhesion to said planar surface.

29. The method of claim 28, further including a step of providing a first reflective element positioned to increase the optical efficiency of said light emitter.

30. The method of claim 28, wherein the step of providing said first reflective element includes providing an angled surface on the base of said encapsulant.

31. The method of claim 28, further including a step of providing a second reflective element positioned to increase the reflectivity of said angled surface.

32. The method of claim 31, wherein the step of providing said second reflective element includes a step of forming a reflective material region by using one of painting, plating, and deposition.

33. The method of claim 29, wherein the step of providing said first reflective element includes a step of providing a heat spreader with a reflective surface corresponding to said supporting surface.

34. The method of claim 28, wherein the step of providing said encapsulant includes a step of positioning said encapsulant so that it hermetically seals said light source, said hermetic seal remaining unbroken with the change in temperature.

35. The method of claim 28, wherein the step of providing said encapsulant includes a step of positioning said encapsulant so that the relative position of said encapsulant and light source remains unchanged with changes in temperature.

36. The method of claim 28, further including a step of positioning a barrier region adjacent to said supporting surface and a base of said encapsulant, said barrier region forming a seal for said light source.