Light emitting device packages using light scattering particles of different size

• US 20090050911A1
• Filed: 08/24/2007
• Published: 02/26/2009
• Est. Priority Date: 08/24/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chakraborty, Arpan
• Granted Patent: US 11,114,594 B2
• Time in Patent Office: Days
• US Class Current: 257/89
• 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 33/504 Elements with two or more wavelength conversion materials
• 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: Y10T 428/2991 Coated

Abstract

A radiation emitting device comprising light scattering particles of different sizes that at least partially surround an emitter, improving the spatial color mixing and color uniformity of the device. Multiple sizes of light scattering particles are dispersed in a medium to at least partially surround a single- or multiple-chip polychromatic emitter package. The different sizes of light scattering particles interact with corresponding wavelength ranges of emitted radiation. Thus, radiation emitted over multiple wavelength ranges or sub-ranges can be efficiently scattered to eliminate (or intentionally create) spatially non-uniform color patterns in the output beam.

Claims

1. An emitting device, comprising:

at least one emitter that emits a spectrum of radiation;

a first plurality of scattering particles of a first size at least partially surrounding said at least one emitter; and

a second plurality of scattering particles of a second size at least partially surrounding said at least one emitter;

wherein respective portions of the radiation emitted from said emitter interacts with said first and second pluralities of scattering particles.

2. The emitting device of claim 1, wherein said emitted spectrum comprises visible light.

3. The emitting device of claim 1, further comprising additional pluralities of scattering particles such that said emitting device comprises scattering particles of at least three different sizes.

4. The emitting device of claim 1, wherein said first plurality of light scattering particles interacts with radiation emitted within a first wavelength range and said second plurality of light scattering particles interacts with radiation emitted within a second wavelength range.

5. The emitting device of claim 1, further comprising multiple emitters, each of said emitters emitting a respective spectrum of radiation.

6. The emitting device of claim 1, wherein said first and second pluralities of light scattering particles are disposed in an encapsulant arranged such that substantially all of the emitted radiation passes through said encapsulant.

7. The emitting device of claim 1, wherein said first and second pluralities of light scattering particles are disposed in a wavelength conversion layer that at least partially surrounds said at least one emitter.

8. The emitting device of claim 1, wherein said first and second pluralities of light scattering particles are disposed in a lens element that interacts with said emitted radiation.

9. The emitting device of claim 1, wherein said first plurality of light scattering particles comprises alumina (Al₂O₃).

10. The emitting device of claim 1, wherein said first and second pluralities of light scattering particles are homogenously mixed.

11. The emitting device of claim 1, wherein said first scattering particle size is chosen such that the sum of radiation scattered at all wavelengths within a first sub-spectrum is substantially maximized.

12. The emitting device of claim 1, wherein said second scattering particle size is chosen such that the sum of radiation scattered at all wavelengths within a second sub-spectrum is substantially maximized.

13. The emitting device of claim 1, wherein said first plurality of scattering particles at least partially surrounds said emitter according to a first particle density.

14. The emitting device of claim 1, wherein said second plurality of scattering particles at least partially surrounds said emitter according to a second particle density.

15. The emitting device of claim 1, wherein the density of said first plurality of particles and the density of said second plurality of particles are related according to a density ratio.

16. The emitting device of claim 1, wherein said first plurality of scattering particles comprises alumina particles, said alumina particles having diameters ranging from approximately 1-2 micrometers and distributed at approximately 0.08% per volume in a medium surrounding said at least one emitter.

17. The emitting device of claim 16, wherein said second plurality of scattering particles comprises submicron alumina particles, said submicron alumina particles having diameters less than approximately 1 micrometer and distributed at approximately 0.14% per volume in said medium.

18. A light emitting device, comprising:

at least one light emitter;

an encapsulant arranged such that substantially all of the light emitted from said light emitter passes through said encapsulant; and

a plurality of scattering particles disposed throughout said encapsulant, said plurality of scattering particles comprising at least two different sizes of particles.

19. The light emitting device of claim 18, said at least one light emitter comprising multiple light emitters of at least two different colors.

20. The light emitting device of claim 18, wherein said different scattering particles of different sizes are homogenously mixed within said encapsulant.

21. The light emitting device of claim 18, wherein said different scattering particles of different sizes are inhomogeneously mixed within said encapsulant.

22. The light emitting device of claim 18, said at least one emitter comprising at least one red light emitter and at least one white light emitter.

23. The light emitting device of claim 18, wherein said encapsulant has beam-shaping properties.

24. The light emitting device or claim 18, said plurality of scattering particles comprising alumina (Al₂O₃).

25. The light emitting device of claim 18, wherein said different sizes of scattering particles are disposed in said encapsulant according to respective particle densities, each size of scattering particle corresponding to a respective particle density.

26. The emitting device of claim 18, wherein said plurality of scattering particles comprises a first and second size of alumina particles, said first size having diameters ranging from approximately 1-2 micrometers and distributed at approximately 0.08% per volume in said encapsulant, said second size having diameters less than approximately 1 micrometer and distributed at approximately 0.14% per volume in said encapsulant.

27. An encapsulant, comprising:

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

a second material having a particulate characteristic dispersed within said first material, said second material having a second refractive index; and

a third material having a particulate characteristic dispersed within said first material, said third material having a third refractive index.

28. The encapsulant of claim 27, further comprising additional materials having a particulate characteristic such that the encapsulant comprises scattering particles having at least three different indices of refraction.

29. The encapsulant of claim 27, wherein said second and third materials are homogenously mixed throughout said first material.

30. The encapsulant of claim 27, wherein said second and said third materials are inhomogeneously mixed throughout said first material.

31. The encapsulant of claim 27, wherein said second material is disposed throughout said first material according to a corresponding particle density.

32. The encapsulant of claim 27, wherein said third material is disposed throughout said first material according to a corresponding particle density.

33. The encapsulant of claim 27, wherein the particle density of said second material is related to the particle density of said third material according to a ratio.

34. An encapsulant, comprising:

a first material defining the shape of said encapsulant;

a second material having a particulate characteristic dispersed within said first material, said second material comprising particles of an average size; and

a third material having a particulate characteristic dispersed within said first material, said third material comprising particles of an average size different than that of said particles in said second material.

35. The encapsulant of claim 34, further comprising additional materials having a particulate characteristic such that said encapsulant comprises materials having at least three different particle sizes.

36. The encapsulant of claim 34, wherein said second and third materials are homogenously mixed throughout said first material.

37. The encapsulant of claim 34, wherein said second and said third materials are inhomogeneously mixed throughout said first material.

38. The encapsulant of claim 34, wherein said second material is disposed throughout said first material according to a corresponding particle density.

39. The encapsulant of claim 34, wherein said third material is disposed throughout said first material according to a corresponding particle density.

40. The encapsulant of claim 34, wherein the particle density of said second material is related to the particle density of said third material according to a ratio.

41. The emitting device of claim 34, wherein said second material comprises alumina particles, said alumina particles having diameters ranging from approximately 1-2 micrometers and distributed at approximately 0.08% per volume in said first material.

42. The emitting device of claim 34, wherein said third material comprises submicron alumina particles, said submicron alumina particles having diameters less than approximately 1 micrometer and distributed at approximately 0.14% per volume in said first material.