Packages for semiconductor light emitting devices utilizing dispensed encapsulants and methods of packaging the same

• US 20070029569A1
• Filed: 08/04/2005
• Published: 02/08/2007
• Est. Priority Date: 08/04/2005
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Andrews, Peter
• Granted Patent: US 7,365,371 B2
• Time in Patent Office: Days
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 2924/00012 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 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2933/005 relating to encapsulations
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/52 Encapsulations
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

A submount for mounting an LED chip includes a substrate, a die attach pad configured to receive an LED chip on an upper surface of the substrate, a first meniscus control feature on the substrate surrounding the die attach pad and defining a first encapsulant region of the upper surface of the substrate, and a second meniscus control feature on the substrate surrounding the first encapsulant region and defining a second encapsulant region of the upper surface of the substrate. The first and second meniscus control features may be substantially coplanar with the die attach pad. A packaged LED includes a submount as described above and further includes an LED chip on the die attach pad, a first encapsulant on the substrate within the first encapsulant region, and a second encapsulant on the substrate within the second encapsulant region and covering the first encapsulant. Method embodiments are also disclosed.

Claims

1. A submount for mounting an LED, the submount comprising:

a substrate having an upper surface;

a die attach pad on the upper surface of the substrate, the die attach pad configured to receive an LED chip;

a first meniscus control feature on the substrate, the first meniscus control feature surrounding the die attach pad and defining a first encapsulant region of the upper surface of the substrate and configured to limit the flow of a liquid encapsulant material, and

a second meniscus control feature on the substrate, the second meniscus control feature surrounding the first encapsulant region and defining a second encapsulant region of the upper surface of the substrate and configured to limit the flow of a liquid encapsulant material.

2. The submount of claim 1, wherein the substrate comprises a printed circuit board (PCB).

3. The submount of claim 1, wherein the die attach pad and the first and second meniscus control features comprise metal traces.

4. The submount of claim 1, wherein the first and/or second meniscus control features comprises a metal film.

5. The submount of claim 1, wherein the die attach pad and the first and second meniscus control features comprise the same material.

6. The submount of claim 5, wherein the first and/or second meniscus control features comprise a plated metal film or a polymer feature.

7. The submount of claim 1, wherein the die attach pad and the first and second meniscus control features are directly on the substrate.

8. The submount of claim 1, further comprising a wirebond pad on the substrate, the wirebond pad disposed within the second encapsulant region.

9. The submount of claim 8, wherein the wirebond pad is disposed within the first encapsulant region.

10. The submount of claim 1, wherein the substrate comprises a lower surface opposite the upper surface of the substrate, and wherein the submount further comprises an electrode on the lower surface of the substrate.

11. The submount of claim 10, further comprising a conductive via extending through the substrate from the electrode to the die attach pad.

12. The submount of claim 10, further comprising:

a wirebond pad on the substrate, the wirebond pad disposed within the second encapsulant region; and

a conductive via extending through the substrate from the electrode to the wirebond pad.

13. The submount of claim 1, further comprising an electrode on the upper surface of the substrate.

14. The submount of claim 13, wherein the electrode on the upper surface of the substrate 110 and the first and second meniscus control features comprise the same material.

15. The submount of claim 13, wherein the substrate comprises a lower surface opposite the upper surface of the substrate, and the submount further comprises a lower electrode on the lower surface of the substrate and a conductive via extending through the substrate from the lower electrode to the electrode on the upper surface of the substrate.

16. The submount of claim 1, further comprising:

a third meniscus control feature disposed within the first encapsulant region and surrounding the die attach pad.

17. The submount of claim 16, wherein the third meniscus control feature defines a third encapsulant region within the first encapsulant region and wherein the first meniscus control feature and the third meniscus control feature define a region in the first encapsulant region surrounding the third encapsulant region.

18. The submount of claim 17, wherein the region of the first encapsulant region defined by the first meniscus control feature and the third meniscus control feature is ring-shaped.

19. The submount of claim 1, further comprising a plurality of surface features on the substrate between the first meniscus control feature and the second meniscus control feature, wherein a path extending in a radial direction from the first meniscus control feature to the second meniscus control feature is interrupted by at least one surface feature.

20. The submount of claim 19, wherein the surface features are discontinuous.

21. The submount of claim 1, further comprising at least one surface feature on the substrate between the first meniscus control feature and the second meniscus control feature.

22. The submount of claim 21, wherein the at least one surface feature and the first and second meniscus control features comprise a metal film.

23. The submount of claim 21, wherein the at least one surface feature and the first and second meniscus control features comprise the same material.

24. The submount of claim 23, wherein the at least one surface feature and the first and second meniscus control features comprise a plated metal film, and/or a polymer.

25. The submount of claim 23, wherein the first and/or second meniscus control feature comprises a patterned feature on the substrate.

26. The submount of claim 25 wherein the patterned feature comprises a patterned metal feature.

27. The submount of claim 23, wherein the first and/or second meniscus control feature comprises a corner of a patterned feature on the substrate.

28. The submount of claim 1, wherein the die attach pad and the first and second meniscus control features comprise metal traces and wherein the die attach pad further comprises a metal stack on the metal trace.

34. A packaged LED comprising a submount as recited in claim 1, further comprising:

an LED chip on the die attach pad;

a first encapsulant on the substrate within the first encapsulant region; and

a second encapsulant on the substrate within the second encapsulant region, the second encapsulant covering the first encapsulant.

35. The packaged LED of claim 34, further comprising a wirebond connection between the LED chip and the wirebond pad.

36. The packaged LED of claim 34, further comprising an electrostatic discharge (ESD) protection chip on the die attach pad.

37. The packaged LED of claim 34, wherein the first encapsulant comprises silicone gel and/or epoxy resin.

38. The packaged LED of claim 34 wherein the first encapsulant comprises a wavelength conversion material.

39. The packaged LED of claim 38 wherein the wavelength conversion material comprises a phosphor and/or a nanocrystal.

40. The packaged LED of claim 34, wherein the second encapsulant comprises silicone gel and/or epoxy resin.

41. The packaged LED of claim 34 wherein the second encapsulant comprises a wavelength conversion material.

42. The packaged LED of claim 38 wherein the wavelength conversion material comprises a phosphor and/or a nanocrystal.

43. A packaged LED comprising a submount as recited in claim 17, further comprising:

an LED chip on the die attach pad;

a first encapsulant on the substrate within the region of the first encapsulant region defined by the first meniscus control feature and the second meniscus control feature;

a second encapsulant on the substrate within the third encapsulant region; and

a third encapsulant on the substrate within the second encapsulant region, the third encapsulant covering the first encapsulant and the second encapsulant.

29. A submount for mounting an LED, the submount comprising:

a substrate having an upper surface;

a patterned film on the upper surface of the substrate, wherein the patterned film comprises;

a portion configured to receive an LED chip;

a first meniscus control feature on the substrate defining a first encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the first encapsulant region, and

a second meniscus control feature on the substrate defining a second encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the second encapsulant region.

30. The submount of claim 29, wherein the patterned film comprises a conductive trace directly on the substrate.

31. The submount of claim 29, wherein the patterned film further comprises a wirebond pad disposed within the second encapsulant region.

32. The submount of claim 31, wherein the wirebond pad is disposed within the first encapsulant region.

33. The submount of claim 29, wherein the patterned film further comprises an electrode disposed outside the second encapsulant region.

44. A method of forming an LED submount, comprising:

forming a patterned metal layer on a substrate, the patterned metal layer including a die attach pad;

forming a first meniscus control feature surrounding the die attach pad and defining a first encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the first encapsulant region, and a second meniscus control feature surrounding the first encapsulant region and defining a second encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the second encapsulant region.

45. A method of forming a packaged LED, comprising:

depositing a film on a substrate;

patterning the film to form a die attach pad;

forming a first meniscus control feature surrounding the die attach pad and defining a first encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the first encapsulant region, and a second meniscus control feature surrounding the first encapsulant region and defining a second encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the second encapsulant region;

mounting an LED chip on the die attach pad;

dispensing a first encapsulant material on the substrate and the LED chip within the first encapsulant region;

curing the first encapsulant material;

dispensing a second encapsulant material on the substrate within the second encapsulant region; and

curing the second encapsulant material.

46. The method of claim 45, wherein patterning the film comprises patterning the film to form a wirebond pad within the second encapsulant region, the method further comprising forming a wirebond connection between the LED chip and the wirebond pad.

47. The method of claim 45, further comprising pre-dispensing a quantity of encapsulant material adjacent the LED chip prior to dispensing the first encapsulant material.

48. The method of claim 45, wherein dispensing the first encapsulant material comprises dispensing a sufficient quantity of the first encapsulant material to cover the LED chip.

49. The method of claim 45, wherein the first encapsulant material comprises a wavelength conversion material.

50. The method of claim 45, further comprising forming at least one surface feature between the first and second meniscus control features.

51. The method of claim 45, further comprising forming a meniscus extension feature outside the second encapsulant region, the meniscus extension feature surrounding the second encapsulant region and defining a encapsulant extension area of the upper surface of the substrate.

52. The method of claim 51, further comprising:

dispensing a third encapsulant material in the encapsulant extension area after curing the second encapsulant material; and

curing the third encapsulant material.

53. The method of claim 52, wherein the encapsulant extension area has a peripheral shape that is different from a peripheral shape of the second encapsulant region.

54. The method of claim 53, wherein the encapsulant extension area has a peripheral shape that is oval.

55. The method of claim 53, wherein the encapsulant extension area has a peripheral shape that is generally square or rectangular.

56. A method of forming a packaged LED, comprising:

forming a patterned metal film on a substrate, the patterned metal film including a die attach pad;

forming a first meniscus control feature surrounding the die attach pad and defining a first encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the first encapsulant region, a second meniscus control feature surrounding the first encapsulant region and defining a second encapsulant region of the upper surface of the substrate and configured to limit the flow of an encapsulant material out of the second encapsulant region, and a third meniscus control feature within the first encapsulant region and surrounding the die attach pad to define a third encapsulant-region within the first encapsulant region and wherein the first meniscus control feature and the third meniscus control feature define a region in the first encapsulant region surrounding the third encapsulant region;

mounting an LED chip on the die attach pad;

dispensing a first encapsulant material within the region in the first encapsulant region defined by the first meniscus control feature and the third meniscus control feature,

curing the first encapsulant material;

dispensing a second encapsulant material on the substrate within the third encapsulant region; and

curing the second encapsulant material.

57. The method of claim 56, further comprising:

dispensing a third encapsulant material within the second encapsulant region; and

curing the third encapsulant material.

58. The method of claim 56, wherein the dispensed first encapsulant material defines a cavity around the LED chip.

59. The method of claim 58, wherein dispensing the second encapsulant material comprises dispensing the second encapsulant material into the cavity around the LED chip after curing the first encapsulant material.

60. The method of claim 59, wherein the third encapsulant material comprises a wavelength conversion material.

61. The method of claim 56, wherein patterning the metal layer comprises patterning the metal layer to form a meniscus extension feature outside the second encapsulant region, the meniscus extension feature surrounding the second encapsulant region and defining an encapsulant extension area of the upper surface of the substrate.

62. The method of claim 56, further comprising:

dispensing a fourth encapsulant material in the encapsulant extension area after curing the second encapsulant material; and

curing the fourth encapsulant material.

63. The method of claim 62, wherein the encapsulant extension area has a peripheral shape that is different from a peripheral shape of the second encapsulant region.

64. The method of claim 63, wherein the encapsulant extension area has a peripheral shape that is oval.

65. The method of claim 63, wherein the encapsulant extension area has a peripheral shape that is generally square or rectangular.

66. The method of claim 56, wherein dispensing the first encapsulant material comprises dispensing an encapsulant in a shape corresponding to a shape of the region surrounding the third encapsulant region.

67. The method of claim 66, wherein the shape of the region surrounding the third encapsulant region is annular, and wherein dispensing the first encapsulant material comprises moving a dispensing needle in a circular motion.

68. The method of claim 56, wherein forming the first meniscus control feature, the second meniscus control feature and/or the third meniscus control feature comprises forming a patterned metal film on the substrate.

69. The method of claim 56, wherein forming the first meniscus control feature, the second meniscus control feature and/or the third meniscus control feature comprises forming a polymer feature on the substrate.