WHITE LIGHT LED WITH MULTIPLE ENCAPSULATION LAYERS

• US 20090065791A1
• Filed: 09/06/2007
• Published: 03/12/2009
• Est. Priority Date: 09/06/2007
• Status: Active Grant

• Current Assignee: Semileds Optoelectronics Company Limited (SemiLEDs Inc)
• Original Assignee: Semileds Optoelectronics Company Limited (SemiLEDs Inc)
• Inventors: Liu, Tien-Min, YEN, JUI-KANG, Chen, Yung-Wei
• Granted Patent: US 8,866,185 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• 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 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/49109 outside the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• 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 2924/00014 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 2924/181 Encapsulation
• 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

Abstract

Light-emitting semiconductor devices with multiple encapsulation layers having more uniform white light when compared to conventional light-emitting devices and methods for producing the same are provided. The uniformity of the emitted white light may be quantified by comparing correlated color temperature (CCT) variations between devices, where embodiments of the present invention have a lower CCT variation when compared to conventional devices over a substantial range of light emission angles.

Claims

1. A packaged light-emitting semiconductor device, comprising:

a housing having a recessed volume;

one or more light-emitting semiconductor dies disposed in the recessed volume;

a first encapsulation material disposed above the one or more light-emitting semiconductor dies;

a second encapsulation material disposed above the first encapsulation material such that only a portion of an upper surface of the first encapsulation material is covered by the second encapsulation material; and

a third encapsulation material disposed above the first and second encapsulation materials.

2. The device of claim 1, further comprising a lead frame for external connection coupled to the one or more dies.

3. The device of claim 1, wherein the housing comprises a ceramic substrate coupled to the one or more light-emitting semiconductor dies.

4. The device of claim 1, wherein the one or more light-emitting semiconductor dies are light-emitting diode (LED) dies, vertical light-emitting diode (VLED) dies, or laser diode dies.

5. The device of claim 1, wherein the first encapsulation material comprises a transparent resin.

6. The device of claim 1, wherein the first encapsulation material comprises a resin and a diffuser.

7. The device of claim 6, wherein the diffuser comprises at least one of SiO₂, Al₂O₃, TiO₂, or Ta₂O₅.

8. The device of claim 1, wherein the second encapsulation material comprises a resin and one or more fluorescent materials.

9. The device of claim 8, wherein the weight ratio of the fluorescent materials in the second encapsulation material is greater than 10%.

10. The device of claim 8, wherein the fluorescent materials comprise at least one of YAG/Gd:

Ce, TAG;

Ce, silicate;

Eu, calcium scandate;

Ce, calcium aluminum silicon nitride;

Ce, or combinations thereof.

11. The device of claim 1, wherein the second encapsulation material comprises a pre-formed insert.

12. The device of claim 1, wherein an upper surface of the second encapsulation material is flat or convex.

13. The device of claim 1, wherein the second encapsulation material only covers the upper surface of the first encapsulation material in about an 80°

(±

40°

from a nominal axis) range of light emission angles.

14. The device of claim 1, wherein the third encapsulation material comprises a resin and one or more fluorescent materials.

15. The device of claim 14, wherein the weight ratio of the fluorescent materials in the third encapsulation material is less than 20%.

16. The device of claim 14, wherein the fluorescent materials comprise at least one of YAG/Gd:

Ce, TAG;

Ce, silicate;

Eu, calcium scandate;

Ce, calcium aluminum silicon nitride;

Ce, or combinations thereof.

17. The device of claim 1, wherein a phosphor concentration of the third encapsulation material is lower than a phosphor concentration of the second encapsulation material.

18. The device of claim 1, wherein a total correlated color temperature (CCT) variation is less than about 200 K over a 140°

(±

70°

from a nominal axis) range of light emission angles.

19. The device of claim 1, further comprising a lens disposed at least partially above the third encapsulation material.

20. A packaged light-emitting semiconductor device, comprising:

a housing having a recessed volume;

one or more light-emitting semiconductor dies disposed in the recessed volume;

a first encapsulation material disposed above the one or more light-emitting semiconductor dies;

a second encapsulation material disposed above the first encapsulation material; and

a third encapsulation material disposed above the second encapsulation material such that a total correlated color temperature (CCT) variation of the packaged device is less than about 200 K over a 140°

(±

70°

from a nominal axis) range of light emission angles.

21. The device of claim 20, wherein the second encapsulation material only covers a portion of an upper surface of the first encapsulation material.

22. The device of claim 21, wherein the second encapsulation material only covers the upper surface of the first encapsulation material in about an 80°

(±

40°

from the nominal axis) range of light emission angles.

23. The device of claim 20, wherein a phosphor concentration of the third encapsulation material is lower than a phosphor concentration of the second encapsulation material.

24. A method for packaging a light-emitting semiconductor device, comprising:

providing one or more light-emitting semiconductor dies disposed in a recessed volume of a housing;

partially filling the recessed volume with a first encapsulation material;

disposing a second encapsulation material above the first encapsulation material such that only a portion of an upper surface of the first encapsulation material is covered by the second encapsulation material; and

at least partially filling the recessed volume with a third encapsulation material above the first and second encapsulation materials.

25. The method of claim 24, wherein the one or more light-emitting semiconductor dies comprise light-emitting diode (LED) dies, vertical light-emitting diode (VLED) dies, or laser diode dies.

26. The method of claim 24, wherein partially filling the recessed volume with the first encapsulation material comprises dispensing the first encapsulation material into the recessed volume.

27. The method of claim 24, wherein partially filling the recessed volume with the first encapsulation material comprises dispensing a first portion of the first encapsulation material into the recessed volume, allowing the first portion to settle within the recessed volume, and dispensing a second portion of the first encapsulation material above the settled first portion.

28. The method of claim 24, wherein the first encapsulation material comprises a transparent resin.

29. The method of claim 24, further comprising combining a transparent resin and a diffuser to form the first encapsulation material.

30. The method of claim 29, wherein the diffuser comprises at least one of SiO₂, Al₂O₃, TiO₂, or Ta₂O₅.

31. The method of claim 24, further comprising fully curing or pre-curing the first encapsulation material before disposing the second encapsulation material above the first encapsulation material.

32. The method of claim 24, wherein disposing the second encapsulation material above the first encapsulation material comprises placing a pre-formed insert or dispensing, stamping, or inject printing the second encapsulation material in the recessed volume above the first encapsulation material.

33. The method of claim 24, wherein the second encapsulation material comprises a resin and one or more fluorescent materials and the weight ratio of the fluorescent materials in the second encapsulation material is greater than 10%.

34. The method of claim 24, further comprising fully curing or pre-curing the second encapsulation material before at least partially filling the recessed volume with the third encapsulation material.

35. The method of claim 24, wherein a phosphor concentration of the third encapsulation material is lower than a phosphor concentration of the second encapsulation material.

36. The method of claim 24, wherein the third encapsulation material comprises a resin and one or more fluorescent materials and the weight ratio of the fluorescent materials in the third encapsulation material is less than 10%.

37. The method of claim 24, further comprising curing the third encapsulation material after at least partially filling the recessed volume.

38. The method of claim 24, wherein the packaged light-emitting device has a total correlated color temperature (CCT) variation of less than about 200 K over a 140°

(±

70°

from a nominal axis) range of emission angles.