Semiconductor light emitting devices including a luminescent conversion element and methods for packaging the same

• US 20050221519A1
• Filed: 02/10/2005
• Published: 10/06/2005
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Becerra, Maryanne, Coleman, Thomas G., Leung, Michael
• Granted Patent: US 7,517,728 B2
• Time in Patent Office: Days
• US Class Current: 438/27
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• 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 33/52 Encapsulations
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

Methods of packaging a semiconductor light emitting device include dispensing a first quantity of encapsulant material into a cavity including the light emitting device. The first quantity of encapsulant material in the cavity is treated to form a hardened upper surface thereof having a selected shape. A luminescent conversion element is provided on the upper surface of the treated first quantity of encapsulant material. The luminescent conversion element includes a wavelength conversion material and has a thickness at a middle region of the cavity greater than proximate a sidewall of the cavity.

Claims

1. A method of packaging a semiconductor light emitting device, comprising:

dispensing a first quantity of encapsulant material into a cavity including the light emitting device;

treating the first quantity of encapsulant material in the cavity to form a hardened upper surface thereof having a selected shape; and

providing a luminescent conversion element on the upper surface of the treated first quantity of encapsulant material, the luminescent conversion element including a wavelength conversion material and having a thickness at a middle region of the reflective cavity greater than at a region proximate a sidewall of the cavity.

2. The method of claim 1 wherein the thickness of the luminescent conversion-element continuously decreases as the luminescent conversion element extends radially outward from the middle region to the sidewall.

3. The method of claim 1 wherein the thickness of the luminescent conversion element varies by more than ten percent of a maximum thickness of the luminescent conversion element.

4. The method of claim 1 wherein the luminescent conversion element has a biconvex, plano-convex or concavo-convex shape.

5. The method of claim 1 further comprising:

dispensing a second quantity of encapsulant material onto the luminescent conversion element to form a convex meniscus of encapsulant material in the cavity providing a desired shape of a lens; and

curing the second quantity of encapsulant material to form the lens for the packaged light emitting device from the encapsulant material.

6. The method of claim 1 further comprising:

dispensing a second quantity of encapsulant material onto the luminescent conversion element;

positioning a lens in the cavity on the dispensed second quantity of encapsulant material; and

curing the dispensed second quantity of encapsulant material to attach the lens in the cavity.

7. The method of claim 1 wherein providing a luminescent conversion element comprises:

dispensing a second quantity of encapsulant material onto the upper surface of the first quantity of encapsulant material, the second quantity of encapsulant material having the wavelength conversion material therein; and

curing the second quantity of encapsulant material to define the luminescent conversion element.

8. The method of claim 7 wherein the luminescent conversion element has a biconvex shape and wherein the selected shape is concave and wherein dispensing and curing the second quantity of encapsulant material comprise dispensing and curing the second quantity of encapsulant material to form a convex upper surface of the second quantity of encapsulant material.

9. The method of claim 7 wherein the luminescent conversion element has a plano-convex shape and wherein the selected shape is concave and wherein dispensing and curing the second quantity of encapsulant material comprise dispensing and curing the second quantity of encapsulant material to form a planar upper surface of the second quantity of encapsulant material.

10. The method of claim 7 wherein the luminescent conversion element has a plano-convex shape and wherein the selected shape is planar and wherein dispensing and curing the second quantity of encapsulant material comprise dispensing and curing the second quantity of encapsulant material to form a convex upper surface of the second quantity of encapsulant material.

11. The method of claim 7 wherein the luminescent conversion element has a concavo-convex shape and wherein the selected shape is convex and wherein dispensing and curing the second quantity of encapsulant material comprise dispensing and curing the second quantity of encapsulant material to form a convex upper surface of the second quantity of encapsulant material.

12. The method of claim 7 wherein the luminescent conversion element has a concavo-convex shape and wherein the selected shape is concave and wherein dispensing and curing the second quantity of encapsulant material comprise dispensing and curing the second quantity of encapsulant material to form a concave upper surface of the second quantity of encapsulant material.

13. The method of claim 1 wherein the wavelength conversion material comprises phosphor and/or nano-crystals.

14. The method of claim 1 wherein treating the first quantity of encapsulant material comprises curing the first quantity of encapsulant material.

15. The method of claim 1 wherein treating the first quantity of encapsulant material comprises pre-curing the first quantity of encapsulant material to form a hardened skin on the upper surface thereof and wherein the method further comprises curing the first quantity of encapsulant material after providing the luminescent conversion element.

16. The method of claim 1 wherein the wavelength conversion material comprises phosphor and wherein the first quantity of encapsulant material is substantially free of phosphor.

17. The method of claim 1 wherein the wavelength conversion material comprises phosphor and wherein the first quantity of encapsulant material includes phosphor, the first quantity of encapsulant material having a lower percentage of phosphor by weight than the luminescent conversion element.

18. The method of claim 1 wherein the luminescent conversion element comprises a pre-formed insert and wherein providing the luminescent conversion element on the upper surface comprises placing the pre-formed insert on the upper surface of the treated first quantity of encapsulant material.

19. The method of claim 18 wherein the pre-formed insert comprises a molded plastic phosphor-loaded piece part.

20. The method of claim 18 wherein placing the pre-formed insert on the upper surface is preceded by testing the pre-formed insert.

21. A packaged semiconductor light emitting device, comprising:

a body having a sidewall portion defining a cavity;

a light emitting device positioned in the cavity;

a first quantity of cured encapsulant material in the cavity including the light emitting device; and

a luminescent conversion element on an upper surface of the first quantity of encapsulant material, the luminescent conversion element including a wavelength conversion material and having a thickness at a middle region of the cavity greater than at a region proximate a sidewall of the cavity.

22. The device of claim 21 wherein the thickness of the luminescent conversion element continuously decreases as the luminescent conversion element extends radially outward from the middle region to the sidewall.

23. The device of claim 21 wherein the thickness of the luminescent conversion element varies by more than ten percent of a maximum thickness of the luminescent conversion element.

24. The device of claim 21 wherein the luminescent conversion element has a biconvex, plano-convex or concavo-convex shape.

25. The device of claim 21 wherein the light emitting device comprises a light emitting diode (LED).

26. The device of claim 21 wherein the device has a minimum color temperature no more than 30 percent below a maximum color temperature thereof over a 180 (+/−

90 from central axis)-degree range of emission angles.

27. The device of claim 21 wherein the device has a primary emission pattern having a total correlated color temperature (CCT) variation of less than about 1000K over a 180 (+/−

90 from central axis)-degree range of emission angles.

28. The device of claim 21 wherein the device has a primary emission pattern having a total CCT variation of about 500K over a 180 (+/−

90 from central axis)-degree range of emission angles.

29. The device of claim 21 wherein the device has a primary emission pattern having a total correlated color temperature (CCT) variation of less than about 1000K over a 120 (+/−

45 from central axis)-degree range of emission angles.

30. The device of claim 21 wherein the device has a primary emission pattern having a total correlated color temperature (CCT) variation of less than about 500K over a 90 (+/−

45 from central axis)-degree range of emission angles.

31. The device of claim 21 wherein the body comprises a reflector and wherein the cavity comprises a reflective cavity.

32. A packaged semiconductor light emitting device, comprising:

a body having a sidewall portion defining a cavity;

a light emitting device positioned in the cavity;

a first quantity of cured encapsulant material in the cavity including the light emitting device; and

a luminescent conversion element on an upper surface of the first quantity of encapsulant material, the luminescent conversion element including a wavelength conversion material; and

wherein the packaged semiconductor light emitting device exhibits a variation of correlated color temperature across a 180 (+/−

90 from central axis)-degree range of emission angles of less than 2000K.

33. The device of claim 32 wherein the luminescent conversion element has a thickness at a middle region of the cavity greater than at a region proximate a sidewall of the cavity.

34. The device of claim 33 wherein the thickness of the luminescent conversion element varies by more than ten percent of a maximum thickness of the luminescent conversion element.

35. The device of claim 32 wherein the luminescent conversion element has a biconvex, plano-convex or concavo-convex shape.

36. The device of claim 32 wherein the light emitting device comprises a light emitting diode (LED).

37. The device of claim 32 wherein the device has a minimum color temperature no more than 30 percent below a maximum color temperature thereof over a 180 (+/−

90 from central axis)-degree range of emission angles.

38. The device of claim 32 wherein the device has a primary emission pattern having a total correlated color temperature (CCT) variation of less than about 1000K over a 180 (+/−

90 from central axis)-degree range of emission angles.

39. The device of claim 32 wherein the device has a primary emission pattern having a total CCT variation of about 500K over a 180 (+/−

90 from central axis)-degree range of emission angles.

40. The device of claim 32 wherein the device has a primary emission pattern having a total correlated color temperature (CCT) variation of less than about 1000K over a 120 (+/−

45 from central axis)-degree range of emission angles.

41. The device of claim 32 wherein the device has a primary emission pattern having a total correlated color temperature (CCT) variation of less than about 500K over a 90 (+/−

45 from central axis)-degree range of emission angles.

42. The device of claim 32 wherein the body comprises a reflector and wherein the cavity comprises a reflective cavity.