Encapsulant with scatterer to tailor spatial emission pattern and color uniformity in light emitting diodes

• US 20080308825A1
• Filed: 06/14/2007
• Published: 12/18/2008
• Est. Priority Date: 06/14/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Keller, Bernd, Chakraborty, Arpan
• Granted Patent: US 7,999,283 B2
• Time in Patent Office: Days
• 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 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• 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: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

A light emitting device having an encapsulant with scattering features to tailor the spatial emission pattern and color temperature uniformity of the output profile. The encapsulant is formed with materials having light scattering properties. The concentration of these light scatterers is varied spatially within the encapsulant and/or on the surface of the encapsulant. The regions having a high density of scatterers are arranged in the encapsulant to interact with light entering the encapsulant over a desired range of source emission angles. By increasing the probability that light from a particular range of emission angles will experience at least one scattering event, both the intensity and color temperature profiles of the output light beam can be tuned.

Claims

1. A light emitting device, comprising:

at least one light emitter; and

an encapsulant arranged such that substantially all light that is emitted from said at least one emitter passes through said encapsulant, said encapsulant having light scattering properties that vary spatially in relation to the emission angle of light propagating through said encapsulant.

2. The light emitting device of claim 1, said encapsulant comprising light scattering particles.

3. The light emitting device of claim 2, said light scattering particles comprising one or more material from the group of titanium dioxide (TiO₂), alumina (Al₂O₃), and fumed silica (SiO₂).

4. The light emitting device of claim 2, said encapsulant comprising multiple three-dimensional (3-D) regions, at least one of said regions containing a higher concentration of said light scattering particles relative to the other of said regions.

5. The light emitting device of claim 4, wherein said encapsulant has a bisecting cross-section, said cross-section showing a tip area disposed distal to said at least one light emitter, said tip area defining one of said 3-D regions having a high concentration of light scattering particles relative to an adjacent region.

6. The light emitting device of claim 4, wherein said encapsulant has a bisecting cross-section, said cross-section showing two wedge-shaped areas extending in opposite directions along the bottom surface of said encapsulant such that said wedge-shaped areas are coextensive with the outer surface of said encapsulant, said wedge-shaped areas defining one of said 3-D regions having a high concentration of light scattering particles relative to an adjacent region.

7. The light emitting device of claim 4, said encapsulant comprising multiple 3-D regions having a high concentration of light scattering particles relative to the other of said regions.

8. The light emitting device of claim 1, wherein one or more portions of the surface of said encapsulant are modified to scatter emitted light incident on said surface.

9. The light emitting device of claim 8, wherein a portion of the surface of said encapsulant is modified to scatter emitted light incident on said surface.

10. The light emitting device of claim 8, wherein a dome-shaped portion of the surface of said encapsulant opposite said emitter is modified.

11. The light emitting device of claim 1, further comprising a layer of wavelength conversion material surrounding the exposed portions of said at least one light emitter.

12. The light emitting device of claim 1, further comprising a reflector element disposed on said substrate, said reflector having a substantially toroidal shape with said encapsulant and said at least one emitter arranged in the center, said reflector element comprising inner walls to redirect light from said at least one emitter toward said encapsulant.

13. The light emitting device of claim 12, wherein said reflector element inner walls are modified to scatter incident light.

14. The light emitting device of claim 1, wherein said at least one emitter comprises a plurality of emitters disposed on said base.

15. A light emitting device, comprising:

at least one emitter disposed on a surface; and

an encapsulant disposed above said emitter such that substantially all of the light emitted from said device passes through said encapsulant, said encapsulant having multiple three-dimensional (3-D) regions with associated concentrations of light scattering particles, said 3-D regions arranged within said encapsulant to modify the output intensity and color temperature profiles of said light emitting device.

16. The light emitting device of claim 15, wherein said 3-D regions are arranged within said encapsulant to improve the color uniformity of the emitted light over a range of viewing angles.

17. The light emitting device of claim 15, wherein said 3-D regions are arranged within said encapsulant to tune the intensity profile of the emitted light as a function of the viewing angles.

18. The light emitting device of claim 15, said encapsulant comprising a 3-D region having a high concentration of light scattering particles relative to an adjacent region, said 3-D region disposed at the tip of said encapsulant opposite said at least one emitter.

19. The light emitting device of claim 15, said encapsulant comprising a 3-D region having a high concentration of light scattering particles relative to an adjacent region, said 3-D region disposed near the surface of said encapsulant proximal to said at least one emitter and extending from the center of said encapsulant outward toward the surface of said encapsulant, the volume of said 3-D region increasing with distance from the center of said encapsulant.

20. The light emitting device of claim 15, said encapsulant comprising a 3-D region having a high concentration of light scattering particles relative to an adjacent region, said 3-D region disposed in a substantially toroidal region having an outer radius that is coextensive with the surface of said encapsulant and an inner radius at a distance from the center of said encapsulant.

21. The light emitting device of claim 15, said encapsulant comprising multiple 3-D regions having a high concentration of light scattering particles relative to the other of said regions.

22. The light emitting device of claim 21, wherein said multiple 3-D regions comprise more than two different concentrations of light scattering particles.

23. The light emitting device of claim 15, further comprising a plurality of emitters disposed on said surface.

24. A method of tuning the output intensity and color temperature profile of light emitted from a source, comprising:

providing an encapsulant proximate to said source such that substantially all of the emitted light passes through said encapsulant;

redirecting light emitted from said source using selectively arranged clusters of light scattering elements within said encapsulant and along the surface of said encapsulant; and

emitting light from said encapsulant with an output profile that is determined by the selective arrangement of said clusters.

25. The method of claim 24, wherein said light scattering elements comprise light scattering particles.

26. The method of claim 25, wherein said light scattering particles comprise one or more material from the group of titanium dioxide (TiO₂), alumina (Al₂O₃), and fumed silica (SiO₂).

27. The method of claim 24, wherein said light scattering elements comprise modified portions of the surface of said encapsulant.

28. The method of claim 24, wherein said light scattering elements comprise light scattering particles within said encapsulant and modified portions of the surface of said encapsulant.

29. An encapsulant, comprising:

a first material defining the shape of said encapsulant, said first material having a first refractive index; and

a second material having a particulate characteristic dispersed within said first material such that said second material has a non-uniform density throughout said first material, said second material having a second refractive index.

30. The encapsulant of claim 29, wherein said encapsulant comprises a high density region having a higher concentration of said second material than adjacent regions within said encapsulant.

31. The encapsulant of claim 30, wherein said encapsulant has a convex curved surface and a flat surface.

32. The encapsulant of claim 31, wherein said encapsulant is positioned to receive light from at least one source, said light incident on said flat surface.

33. The encapsulant of claim 32, wherein said high density region is disposed within said encapsulant such that said high density region interacts with light that is emitted from said at least one source over a range of low emission angles.

34. The encapsulant of claim 33, wherein said high density region is disposed in the tip of said encapsulant.

35. The encapsulant of claim 32, wherein said high density region is disposed within said encapsulant such that said high density region interacts with light that is emitted from said at least one source over a range of high emission angles.

36. The encapsulant of claim 35, wherein said high density region is disposed along the flat edge of said encapsulant such that said high density region forms an inverse cone within said encapsulant.

37. The encapsulant of claim 32, wherein said high density region is disposed within said encapsulant such that said high density region interacts with light that is emitted from said at least one source over a middle range of emission angles.

38. The encapsulant of claim 37, wherein said high density region has a substantially toroidal shape.

39. The encapsulant of claim 32, wherein said high density region is disposed within said encapsulant such that said high density region interacts with light that is emitted from said at least one source over a combination of ranges of low angles, mid-range angles and/or high angles.

40. The encapsulant of claim 29, wherein said encapsulant comprises a plurality of high density regions having a higher concentration of said second material than adjacent regions within said encapsulant.

41. The encapsulant of claim 29, wherein a portion of the surface of said encapsulant has been modified.

42. A method of fabricating an encapsulant, comprising:

providing a mold for shaping said encapsulant;

introducing an amount of a first material having particular light scattering properties into said mold; and

introducing additional materials having particular light scattering properties into said mold in a sequence such that said encapsulant comprises distinct regions, each of said regions having particular light scattering properties.

43. The method of claim 42, wherein each of said materials introduced into said mold is allowed to set before introducing the next of said materials in said sequence into said mold.

44. The method of claim 42, wherein said materials include light scattering particles.

45. The method of claim 44, wherein the light scattering properties of said materials are at least partially determined by the concentration of said light scattering particles in each of said materials.

46. The method of claim 44, wherein said encapsulant is substantially hemispherical, and wherein said first material has the highest concentration of light scattering particles relative to said additional materials, said additional materials disposed to have decreasing concentrations of light scattering particles with increasing distance from the tip of said encapsulant.

47. The method of claim 42, wherein said encapsulant comprises at least three of said distinct regions.