Solid state lighting devices and methods

• US 8,686,445 B1
• Filed: 12/15/2010
• Issued: 04/01/2014
• Est. Priority Date: 06/05/2009
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Hussell, Christopher P., Abare, Amber C., Reiherzer, Jesse Colin
• Primary Examiner(s): POTTER, ROY KARL
• Application Number:
  US12/969,267
• Time in Patent Office: 1,203 Days
• Field of Search: 257/88, 257/89, 257/98, 257/99, 257/E33.055, 257/E33.058, 438/27, 438/28
• US Class Current: 257/88
• CPC Class Codes: H01L 2224/45099 Material
• 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 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/49113 the connectors connecting different bonding areas on the semiconductor or solid-state body to a common bonding area outside the body, e.g. converging wires
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/49 of a plurality of wire connectors
• 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 2924/00012 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 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12035 Zener diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

A light emission package includes at least one solid state emitter, a leadframe including at least one electrical lead and a body structure encasing a portion of the leadframe. A thermal transfer material can be isolated from the at least one electrical lead. The body structure can include a plastic body structure wherein a rim portion can be disposed along a portion of the upper surface of the body structure. The light emission package can also include the at least one solid state emitter mounted over thermal transfer material using a direct metal-to-metal bond such as by eutectic die attachment. The light emission package is operable to emit light with an output of approximately 70% or greater of an initial light output for an extrapolated time of at least approximately 150,000 hours or more.

Claims

1. A light emission package, the package comprising:

a leadframe comprising at least one electrical lead;

a body structure encasing at least a portion of the leadframe;

at least one light emitting diode (LED) with a bonding layer mounted to the light emission package at approximately a eutectic temperature of the bonding layer; and

the body structure comprising a plastic material having a melting point within approximately 28°

Celsius (C) or less of the eutectic temperature of the bonding layer.

2. The light emission package of claim 1, wherein the bonding layer comprises a Au/Sn alloy.

3. The light emission package of claim 1, wherein the bonding layer comprises an 80/20 Au/Sn alloy and the eutectic temperature of the bonding layer is approximately 280°

C.

4. The light emission package of claim 1, comprising a thermal transfer material retained by the body structure and electrically isolated from the at least one electrical lead.

5. The light emission package of claim 4, wherein the at least one LED comprises six LEDs mounted over the thermal transfer material.

6. The light emission package of claim 1, wherein the plastic material comprises a melting point temperature (T_m) less than approximately 315°

C.

7. The light emission package of claim 6, wherein the plastic material comprises a melting point (T_m) of approximately 307°

C.

8. The light emission package of claim 1, wherein the plastic material comprises a glass transition temperature (T_g) greater than approximately 110°

C.

9. The light emission package of claim 8, wherein the plastic material comprises a glass transition temperature (T_g) of approximately 123°

C.

10. The light emission package of claim 1 wherein the plastic material comprises:

an elongation value of approximately 1.4% or greater;

a flexural strength as measured by ASTM D790 standards of approximately 150 MPa or lower;

a flexural modulus of approximately 6.9 GPa or lower; and

/or a tensile strength of approximately 100 MPa or lower as measured by ASTM D638 standards.

11. The light emission package of claim 1, wherein the at least one electrical lead comprises a bent portion.

12. The light emission package of claim 4, wherein the thermal transfer material has an average thickness that is substantially greater than an average thickness of the leadframe.

13. The light emission package of claim 1, wherein a first electrical lead of the at least one electrical lead comprises a plurality of first electrical lead segments extending through at least one exterior side wall, and wherein each first electrical lead segment is separated from each other first electrical lead segment along the at least one exterior side wall by at least one first aperture, and at least a portion of the at least one first aperture is disposed outside the at least one exterior wall.

14. The light emission package of claim 1, wherein the at least one electrical lead comprises a distal portion extending away from at least one exterior side wall in a direction outward from a center portion of the package.

15. The light emission package of claim 14, wherein the at least one electrical lead comprises a first and second electrical lead, each of first and second electrical leads comprising a distal portion extending outward from the center portion of the package.

16. The light emission package of claim 1, wherein the body structure comprises a rim portion disposed at least partially over an upper surface of the body structure.

17. The light emission package of claim 1, wherein the primary bond between the LED and an underlying mounting substrate comprises a direct metal-to-metal bond.

18. The light emission package of claim 1, wherein the package is operable to emit light with an output of approximately 70% or greater of an initial light output for an extrapolated time of at least approximately 150,000 hours or more.

19. A method of fabricating a light emission package, the method comprising:

providing a leadframe comprising at least one electrical lead;

mounting at least one light emitting diode (LED) with a bonding layer over the light emission package at approximately a eutectic temperature of the bonding layer; and

encasing a body structure about at least a portion of the leadframe, the body structure comprising a plastic body structure with a melting point within approximately 28°

Celsius or less of the eutectic temperature of the bonding layer.

20. The method of claim 19, wherein encasing a body structure about at least a portion of the leadframe comprises molding the plastic body structure about at least a portion of the leadframe.

21. The method of claim 19, wherein providing a leadframe comprises providing a leadframe comprising at least first and second electrical leads, and further comprising providing a thermal transfer material electrically isolated from the first and second electrical leads.

22. The method of claim 19, wherein mounting the at least one LED comprises facilitating a direct metal-to-metal bond between the bonding layer of the LED and an underlying mounting substrate.

23. A light emission package, the package comprising:

a leadframe comprising at least one electrical lead;

a body structure encasing at least a portion of the leadframe;

at least one light emitting diode (LED) mounted over the light emission package at a mounting temperature of approximately 280°

Celsius or greater; and

the body structure comprising a plastic material with a melting point of approximately 28°

Celsius or less from the mounting temperature.

24. The light emission package of claim 23, further comprising a thermal transfer material retained by the body structure and electrically isolated from the at least one electrical lead.

25. The light emission package of claim 24, wherein the at least one LED comprises six LEDs mounted over the thermal transfer material.

26. The light emission package of claim 23, wherein the plastic material comprises a melting point temperature (T_m) less than approximately 315°

C.

27. The light emission package of claim 26, wherein the plastic material comprises a melting point (T_m) of approximately 307°

C.

28. The light emission package of claim 23, wherein the plastic material comprises a glass transition temperature (T_g) greater than approximately 110°

C.

29. The light emission package of claim 28, wherein the plastic material comprises a glass transition temperature (T_g) of approximately 123°

C.

30. The light emission package of claim 24, wherein the thermal transfer material is electrically isolated from a first and second electrical lead.

31. The light emission package of claim 23, wherein the body structure comprises a rim portion disposed at least partially over an upper surface of body structure.

32. The light emission package of claim 23, wherein the primary bond between the LED and an underlying mounting substrate comprises a direct metal-to-metal bond.

33. The light emission package of claim 23, wherein the package is operable to emit light with an output of approximately 70% or greater of an initial light output for an extrapolated time of at least approximately 150,000 hours or more.

34. The light emission package of claim 23, wherein the plastic material comprises:

an elongation value of approximately 1.4% or greater;

a flexural strength as measured by ASTM D790 standards of approximately 150 MPa or lower;

a flexural modulus of approximately 6.9 GPa or lower; and

/or a tensile strength of approximately 100 MPa or lower as measured by ASTM D638 standards.

35. A method of fabricating a light emission package, the method comprising:

providing a leadframe comprising at least one electrical lead;

mounting at least one light emitting diode (LED) over the light emission package at a mounting temperature of approximately 280°

C. or greater; and

forming a body structure about at least a portion of the leadframe, the body structure comprising a plastic body structure having a melting point of approximately 28°

C. or less from the mounting temperature.

36. A light emission package fabricated by the method according to claim 35, wherein the light emission package is operable to emit light with an output of approximately 70% or greater of an initial output for at least approximately 150,000 hours or more.

37. The method of claim 35, wherein encasing a body structure about at least a portion of the leadframe comprises molding the plastic body structure about at least a portion of the leadframe.

38. The method of claim 35, wherein providing a leadframe comprises providing a leadframe comprising at least first and second electrical leads, and further comprising providing a thermal transfer material electrically isolated from the first and second electrical leads.

39. The method of claim 35, wherein mounting the at least one LED comprises facilitating a direct metal-to-metal bond between a bonding layer of the LED and an underlying mounting substrate.

40. A light emission package, the package comprising:

a leadframe comprising at least one electrical lead;

a body structure encasing at least a portion of the leadframe;

a thermal transfer material retained by the body structure and electrically isolated from the at least one electrical lead;

at least one light emitting diode (LED) with a bonding layer mounted over the light emission package at a eutectic temperature of the bonding layer; and

the light emission package being operable to emit light with an output of approximately 70% or greater of an initial light output for at least approximately 150,000 hours or more.

41. The light emission package of claim 40, wherein the output of approximately 70% or greater of the initial light output for at least approximately 150,000 hours or more is extrapolated from data measured using a current of 350 mA and an ambient air temperature (Ta) of 55°

C.

42. The light emission package of claim 40, wherein the bonding layer comprises a Au/Sn alloy.

43. The light emission package of claim 42, wherein the bonding layer comprises an 80/20 Au/Sn alloy and the eutectic temperature of the bonding layer is approximately 280°

C.

44. The light emission package of claim 40, wherein the at least one LED comprises six LEDs mounted over the thermal transfer material.

45. The light emission package of claim 40, wherein the body structure comprises a plastic material.

46. The light emission package of claim 45, wherein the plastic material comprises a melting point temperature (T_m) less than approximately 315°

C.

47. The light emission package of claim 46, wherein the plastic material comprises a melting point (T_m) of approximately 307°

C.

48. The light emission package of claim 45, wherein the plastic material comprises a glass transition temperature (T_g) greater than approximately 110°

C.

49. The light emission package of claim 48, wherein the plastic material comprises a glass transition temperature (T_g) of approximately 123°

C.

50. The light emission package of claim 40, wherein the at least one electrical lead comprises first and second electrical leads, and the thermal transfer material is electrically isolated from each of the first and second electrical leads.

51. The light emission package of claim 40, wherein the body structure comprises a rim portion disposed at least partially over an upper surface of body structure.

52. The light emission package of claim 40, wherein the primary bond between the LED and an underlying mounting substrate comprises a direct metal-to-metal bond.

53. The light emission package of claim 45, wherein the plastic material comprises:

an elongation value of approximately 1.4% or greater;

a flexural strength as measured by ASTM D790 standards of approximately 150 MPa or lower;

a flexural modulus of approximately 6.9 GPa or lower; and

/or a tensile strength of approximately 100 MPa or lower as measured by ASTM D638 standards.

54. A light emission package, the package comprising:

a leadframe comprising at least one electrical lead;

a body structure encasing at least a portion of the leadframe;

a thermal transfer material retained by the body structure and electrically isolated from the at least one electrical lead;

at least one light emitting diode (LED) mounted over the light emission package; and

the light emission package operable to emit light with an output of approximately 70% or greater of an initial light output for at least approximately 150,000 hours or more.

55. The light emission package of claim 54, wherein the at least one LED comprises six LEDs mounted over the thermal transfer material.

56. The light emission package of claim 54, wherein the at least one LED is mounted over the thermal transfer material using a metal-to-metal bond facilitated using a flux eutectic die attach.

57. The light emission package of claim 54, wherein the body structure comprises a plastic material comprising a melting point temperature (T_m) less than approximately 315°

C.

58. The light emission package of claim 57, wherein the plastic material comprises a melting point (T_m) of approximately 307°

C.

59. The light emission package of claim 54, wherein body structure comprises a plastic material comprising a glass transition temperature (T_g) greater than approximately 110°

C.

60. The light emission package of claim 59, wherein the plastic material comprises a glass transition temperature (T_g) of approximately 123°

C.

61. The light emission package of claim 54, wherein the plastic material comprises:

an elongation value of approximately 1.4% or greater;

a flexural strength as measured by ASTM D790 standards of approximately 150 MPa or lower;

a flexural modulus of approximately 6.9 GPa or lower; and

/or a tensile strength of approximately 100 MPa or lower as measured by ASTM D638 standards.

62. A light emission package, the package comprising:

a leadframe comprising at least one electrical lead;

a body structure encasing at least a portion of the leadframe;

at least one light emitting diode (LED) mounted over the light emission package, wherein the at least one LED is mounted over the thermal transfer material using a metal-to-metal bond facilitated using a flux eutectic die attach; and

the light emission package operable to emit light with an output of approximately 70% or greater of an initial light output for an extrapolated time of at least approximately 150,000 hours or more.

63. The light emission package of claim 62, further comprising a thermal transfer material retained by the body structure and electrically isolated from the at least one electrical lead.

64. The light emission package of claim 63, wherein the at least one LED comprises six LEDs mounted over the thermal transfer material.

65. The light emission package of claim 62, wherein the body structure comprises a plastic material.

66. The light emission package of claim 65, wherein the plastic material comprises a melting point temperature (T_m) less than approximately 315°

C.

67. The light emission package of claim 66, wherein the plastic material comprises a melting point (T_m) of approximately 307°

C.

68. The light emission package of claim 65, wherein the plastic material comprises a glass transition temperature (T_g) greater than approximately 110°

C.

69. The light emission package of claim 68, wherein the plastic material comprises a glass transition temperature (T_g) of approximately 123°

C.

70. The light emission package of claim 65, wherein the plastic material comprises:

an elongation value of approximately 1.4% or greater;

a flexural strength as measured by ASTM D790 standards of approximately 150 MPa or lower;

a flexural modulus of approximately 6.9 GPa or lower; and

/or a tensile strength of approximately 100 MPa or lower as measured by ASTM D638 standards.

71. A light emission package, the package comprising:

a leadframe comprising at least one electrical lead; and

a body structure encasing at least a portion of the leadframe, the body structure comprising a rim portion disposed at least partially over an upper surface of body structure.

72. The light emission package of claim 71, further comprising a thermal transfer material retained by the body structure and electrically isolated from the at least one electrical lead.

73. The light emission package of claim 72, wherein the thermal transfer material is electrically isolated from each of the first and second electrical leads.

74. The light emission package of claim 71, wherein the leadframe comprises a first and a second electrical lead.

75. The light emission package of claim 71, wherein the first and second electrical leads extend outwardly from a center portion of the body structure.

76. The light emission package of claim 71, wherein the body structure comprises a molded plastic.

77. The light emission package of claim 71, further comprising an encapsulant dispensed within the body structure to a level flush with upper surface of body structure.

78. The light emission package of claim 71, wherein the rim portion is disposed along an outermost edge portion of the upper surface.