Semiconductor Light Emitting Devices with Densely Packed Phosphor Layer at Light Emitting Surface

• US 20120068594A1
• Filed: 09/21/2010
• Published: 03/22/2012
• Est. Priority Date: 09/21/2010
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Andrews, Peter S.
• Granted Patent: US 8,410,679 B2
• Time in Patent Office: Days
• US Class Current: 313/501
• CPC Class Codes: F21K 9/64 using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• 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 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources

Abstract

An LED includes a chip having a light emitting surface, and a coating of phosphor-containing material on the light emitting surface. Phosphor particles are arranged in a densely packed layer within the coating at the light emitting surface, and such that the light emitting surface is in contacting relationship with the phosphor particles.

Claims

1. A semiconductor light emitting device, comprising:

a semiconductor light emitting element having a light emitting surface; and

a coating of phosphor-containing material on the light emitting surface, wherein phosphor particles are arranged in a densely packed layer within the coating at the light emitting surface, and such that the light emitting surface is in contacting relationship with the layer of phosphor particles.

2. The semiconductor light emitting device of claim 1, wherein coating material above the densely packed layer of phosphor particles is devoid of phosphor particles.

3. The semiconductor light emitting device of claim 1, wherein an average distance that heat generated by the phosphor particles travels from the densely packed layer to the semiconductor light emitting element is substantially less than half the thickness of the coating.

4. The semiconductor light emitting device of claim 1, wherein the light emitting surface comprises a pattern of features extending outwardly to form receptacles for receiving the phosphor particles.

5. The semiconductor light emitting device of claim 1, further comprising an intermediate layer of material between the light emitting surface and coating of phosphor-containing material, wherein the intermediate layer of material comprises a pattern of features extending outwardly therefrom to form receptacles for receiving the phosphor particles.

6. The semiconductor light emitting device of claim 5, wherein the intermediate layer of material comprises silicon nitride.

7. The semiconductor light emitting device of claim 1, wherein the light emitting surface emits light having a first dominant wavelength upon the application of a voltage to the semiconductor light emitting element, and wherein the phosphor particles convert light emitted by the light emitting surface to light having a second dominant wavelength different from the first dominant wavelength.

8. The semiconductor light emitting device of claim 1, wherein the semiconductor light emitting element is selected from the group consisting of light emitting diodes and laser diodes.

9. The semiconductor light emitting device of claim 1, wherein the coating of phosphor-containing material comprises silicone or silicon.

10. A method of making a semiconductor light emitting device, comprising:

applying a phosphor-containing material on at least a portion of a light emitting surface of a semiconductor light emitting element;

causing phosphor particles in the material to become arranged in a densely packed layer within the material at the light emitting surface, and such that the light emitting surface is in contacting relationship with the layer of phosphor particles; and

curing the material without disturbing the densely packed layer of phosphor particles.

11. The method of claim 10, further comprising removing cured material above the densely packed layer of phosphor particles that is devoid of phosphor particles.

12. The method of claim 10, wherein causing the phosphor particles in the material to become arranged in a densely packed layer at the light emitting surface comprises subjecting the semiconductor light emitting element to centrifugal force.

13. The method of claim 10, wherein causing the phosphor particles in the material to become arranged in a densely packed layer at the light emitting surface comprises subjecting the phosphor-containing material to at least one harmonic vibration.

14. The method of claim 10, wherein causing the phosphor particles to become arranged in a densely packed layer at the light emitting surface comprises heating the material to a predetermined temperature and for a predetermined time to lower viscosity of the material prior to curing.

15. The method of claim 10, wherein causing the phosphor particles to become arranged in a densely packed layer at the light emitting surface comprises applying a solvent to the phosphor-containing material prior to curing the material.

16. The method of claim 10, further comprising forming a pattern of features extending outward from the light emitting surface prior to applying the phosphor containing material, wherein the features form receptacles for receiving the phosphor particles.

17. The method of claim 10, further comprising applying an intermediate layer of material on the light emitting surface prior to applying the phosphor containing material, wherein the intermediate layer of material comprises a pattern of features extending outward therefrom, wherein the features form receptacles for receiving the phosphor particles, and wherein applying the phosphor containing material comprises applying the phosphor containing material to the intermediate layer of material.

18. The method of claim 17, wherein the intermediate layer of material comprises silicon nitride.

19. The method of claim 10, wherein the semiconductor light emitting element is selected from the group consisting of light emitting diodes and laser diodes.

20. The method of claim 10, wherein the phosphor-containing material comprises silicone.

21. A method of making a semiconductor light emitting device, comprising sequentially applying first, second and third quantities of phosphor particles to at least a portion of a light emitting surface of a semiconductor light emitting element, wherein the phosphor particles in the second quantity are larger than the phosphor particles in both the first and third quantities, and wherein the phosphor particles in the first and third quantities become closely arranged around the phosphor particles in the second quantity so as to form a densely packed layer at the light emitting surface.

22. The method of claim 21, further comprising:

applying a layer of encapsulating material to the densely packed layer of phosphor particles; and

curing the material without disturbing the densely packed layer of phosphor particles.

23. The method of claim 22, wherein the encapsulating material comprises silicone.

24. The method of claim 21, wherein the first, second and third quantities of phosphor particles are sequentially applied to at least a portion of the light emitting surface through a liquid material, wherein a viscosity of the liquid material has been reduced.

25. The method of claim 24, wherein the viscosity of the liquid material is reduced by heating the liquid material.

26. The method of claim 24, wherein the viscosity of the liquid material is reduced by a solvent.

27. The method of claim 26, wherein the solvent is selected from the group consisting of xylene and hexane.

28. The method of claim 24, wherein the liquid material comprises silicone.

29. A method of making a semiconductor light emitting device, comprising:

applying an amount of phosphor-containing material on at least a portion of a light emitting surface of a semiconductor light emitting element, wherein the light emitting surface emits light having a first dominant wavelength upon the application of a voltage to the semiconductor light emitting element, and wherein phosphor particles in the phosphor-containing material convert light emitted by the light emitting surface to light having a second dominant wavelength different from the first dominant wavelength;

causing phosphor particles in the material to become arranged in a densely packed layer within the material at the light emitting surface, when the amount of phosphor-containing material is sufficient to convert light to a desired color point; and

curing the material without disturbing the densely packed layer of phosphor particles.

30. The method of claim 29, further comprising measuring light conversion by the phosphor-containing material as the phosphor-containing material is being applied to the light emitting surface.

31. The method of claim 29, wherein causing the phosphor particles to become arranged in a densely packed layer at the light emitting surface comprises applying a solvent to the phosphor-containing material.

32. The method of claim 31, further comprising removing the solvent prior to curing.

33. A method of making a semiconductor light emitting device, comprising:

applying a phosphor-containing carrier material on at least a portion of a light emitting surface of a semiconductor light emitting element;

causing phosphor particles in the carrier material to become arranged in a densely packed layer at the light emitting surface, and such that the light emitting surface is in contacting relationship with the layer of phosphor particles;

removing the carrier material without disturbing the densely packed layer of phosphor particles;

applying a layer of encapsulating material to the densely packed layer of phosphor particles; and

curing the material without disturbing the densely packed layer of phosphor particles.

34. The method of claim 33, further comprising agitating the semiconductor light emitting element to obtain a uniform distribution of phosphor particles across the light emitting surface prior to causing the phosphor particles in the carrier material to become arranged in a densely packed layer at the light emitting surface.

35. The method of claim 33, further comprising forming a pattern of features extending outward from the light emitting surface prior to applying the phosphor containing carrier material, wherein the features form receptacles for receiving the phosphor particles.

36. The method of claim 33, further comprising applying an intermediate layer of material on the light emitting surface prior to applying the phosphor containing carrier material, wherein the intermediate layer of material comprises a pattern of features extending outward therefrom, wherein the features form receptacles for receiving the phosphor particles, and wherein applying the phosphor containing carrier material comprises applying the phosphor containing carrier material to the intermediate layer of material.

37. The method of claim 36, wherein the intermediate layer of material comprises silicon nitride.

38. The method of claim 33, wherein causing the phosphor particles in the material to become arranged in a densely packed layer at the light emitting surface comprises subjecting the semiconductor light emitting element to centrifugal force.

39. The method of claim 33, wherein the semiconductor light emitting element is selected from the group consisting of light emitting diodes and laser diodes.

40. The method of claim 33, wherein the encapsulating material comprises silicone.

41. A lighting device, comprising:

a semiconductor light emitting element that emits light having a first dominant wavelength upon the application of a voltage thereto; and

a coating of phosphor-containing material on a light emitting surface of the element, wherein phosphor particles are arranged in a densely packed layer within the material at the light emitting surface, and such that the light emitting surface is in contacting relationship with the layer of phosphor particles, and wherein the phosphor particles convert light emitted by the light emitting surface to light having a second dominant wavelength different from the first dominant wavelength.

42. The lighting device of claim 41, wherein the light emitting surface comprises a pattern of features extending outward from the light emitting surface that form receptacles for receiving the phosphor particles.

43. The lighting device of claim 41, further comprising an intermediate layer of material between the light emitting surface and coating of phosphor-containing material, wherein the intermediate layer of material comprises a pattern of features extending outward therefrom that form receptacles for receiving the phosphor particles.

44. A semiconductor light emitting device, comprising:

a semiconductor light emitting element having a light emitting surface;

an element in adjacent, spaced spaced-apart relationship with the light emitting surface; and

a coating of phosphor-containing material on the element, wherein phosphor particles are arranged in a densely packed layer within the coating.

45. The semiconductor light emitting device of claim 44, wherein the element comprises a lens.

46. The semiconductor light emitting device of claim 44, wherein the element comprises a reflective element.