Light emitting device packages with improved heat transfer

• US 8,598,602 B2
• Filed: 06/28/2010
• Issued: 12/03/2013
• Est. Priority Date: 01/12/2009
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Hussell, Christopher P., Joo, Sung Chul, Pyles, Robert S.
• Primary Examiner(s): POTTER, ROY KARL
• Application Number:
  US12/825,075
• Publication Number:
  US 20110031865A1
• Time in Patent Office: 1,254 Days
• Field of Search: 257/88, 257/99, 257/E21.499, 257/E33.056
• US Class Current: 257/88
• 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 2224/49113 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 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 2924/00014 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 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/642 characterized by the shape
• CPC Class Codes: H01L 33/647 the elements conducting electric current to or from the semiconductor body

Abstract

Packages containing one or more light emitting devices, such as light emitting diodes (LEDs), are disclosed. In one embodiment, LED package can include a thermal element having improved solder reliability to improve heat dissipation capacity of the LED package. LED package can include a molded plastic body having one or more LEDs attached to one or more electrical elements. The LEDs can be connected to an upper surface of the thermal element. The thermal element can include a bottom surface which can extend further away in distance from a body of the LED package than a bottom surface of the electrical element. This configuration can result in an improved connection between the LED package and an external circuitry source, thereby increasing heat transfer ability of the LED package.

Claims

1. A light emitting device package, the package comprising:

a body having a recess with a thermal element disposed in the recess, and the body having at least one electrical element wherein the at least one electrical and thermal elements have bottom surfaces;

at least one light emitting device mounted on a top surface of the thermal element and electrically connected to the electrical element; and

the bottom surface of the electrical element extending away from the body a first distance and the bottom surface of the thermal element extending away from the body a second distance that is greater than the first distance.

2. The light emitting device package of claim 1, wherein the thermal element comprises a base portion and a protruding portion.

3. The light emitting device package of claim 1, wherein the second distance is greater than the first distance by from 0 μ

m to 100 μ

m.

4. The light emitting device package of claim 1, wherein the second distance is greater than the first distance by greater than 100 μ

m.

5. The light emitting device package of claim 1, wherein the thermal element comprises a first exposed portion located above the bottom surface of the electrical element and a second exposed portion located below the bottom surface of the electrical element.

6. The light emitting device package of claim 1, wherein the electrical element comprises a first portion extending vertically downward from the body, and a second portion extending in a linear direction away from the body and away from the recess.

7. The light emitting device package of claim 1, wherein the thermal element comprises a first exposed portion located above the second plane and a second exposed portion located below the second plane.

8. The light emitting device package of claim 1, wherein the electrical element extends to a first plane and the thermal element extends to a second plane which is further away from the body than the first plane.

9. A light emitting device package, the package comprising:

a body having at least one thermal element and at least one electrical element, the at least one electrical and thermal elements having bottom surfaces wherein the electrical element comprises a bend and a first portion which is substantially orthogonal to a second portion;

at least one light emitting device mounted on a top surface of the thermal element and electrically connected to the electrical element; and

the bottom surface of the electrical element extending away from the body a first distance, and the bottom surface of the thermal element extending away from the body a second distance that is greater than the first distance.

10. The light package according to claim 9, wherein the electrical element comprises a J-bend type lead component.

11. The light package according to claim 10, wherein the first portion extends vertically down from the body and the second portion extends in a linear direction towards the body.

12. The light package according to claim 9, wherein the electrical element comprises a gull wing type lead component.

13. The light package according to claim 12, wherein the first portion extends vertically down from the body and the second portion extends in a linear direction away from the body.

14. The light package according to claim 9, wherein the thermal element comprises a first exposed portion located above the bottom surface of the electrical element and a second exposed portion located below the bottom surface of the electrical element.

15. The light emitting device package of claim 9, wherein the second distance is greater than the first distance by from about 0 μ

m to 100 μ

m.

16. The light emitting device package of claim 9, wherein the second distance is greater than the first distance by greater than 100 μ

m.

17. The light emitting device package of claim 9, wherein the electrical element extends to a first plane and the thermal element extends to a second plane which is lower than the first plane.

18. A molded leadframe light emitting device package, the package comprising:

a molded body having at least one thermal element and at least one electrical lead extending directly from a bottom surface of the molded body;

at least one light emitting device mounted on a top surface of the thermal element and electrically connected to the electrical element; and

the electrical lead extending away from the body a first distance and the thermal element extending away from the body a second distance that is greater than the first distance.

19. The light emitting device package according to claim 18, wherein the thermal element comprises an exposed portion flush with a first exterior lateral surface of the body.

20. The light emitting device package according to claim 19, wherein the electrical lead comprises an exposed portion flush with the first exterior lateral surface of the body.

21. The light emitting device package according to claim 18, wherein the thermal element comprises one or more grooves.

22. The light emitting device package of claim 18, wherein the second distance is greater than the first distance by from about 0 μ

m to 100 μ

m.

23. The light emitting device package of claim 18, wherein the second distance is greater than the first distance by greater than 100 μ

m.

24. The light emitting device package of claim 18, wherein the electrical lead extends to a first plane and the thermal element extends to a second plane which is lower than the first plane.

25. The light emitting device package of claim 18, wherein the thermal element and the electrical lead extend only from the bottom surface of the molded body.

26. A light emitting device package, the package comprising:

a body having at least one thermal element and at least one electrical element disposed on a bottom surface of the body, the at least one thermal and electrical elements having bottom surfaces;

at least one light emitting device mounted on a top surface of the body; and

the bottom surface of the electrical element extending away from the body a first distance and the bottom surface of the thermal element extending away from the body a second distance that is greater than the first distance, wherein the second distance is greater than the first distance by from about 0 μ

m to about 100 μ

m.

27. The light emitting device package according to claim 26, further comprising a lens.

28. The light emitting device package according to claim 26, wherein the second distance is greater than the first distance by greater than about 100 μ

m.

29. The light emitting device package according to claim 26, wherein the body comprises an insulating material.

30. The light emitting device package of claim 26, wherein the electrical element extends to a first plane and the thermal element extends to a second plane which is lower than the first plane.

31. A light emitting device package mounted to an external substrate comprising:

a body having at least one electrical element and at least one thermal element;

at least one light emitting device mounted on a top surface of the thermal element and electrically connected to the electrical element; and

the external substrate comprising a notch configured to receive at least a portion of the at least one thermal element.

32. The light emitting device package according to claim 31, wherein the external substrate comprises a printed circuit board (PCB).

33. The light emitting device package according to claim 31, wherein a bottom surface of the electrical element extends away from the body a first distance and a bottom surface of the thermal element extends away from the body a second distance that is greater than the first distance.

34. The light emitting device package according to claim 32, wherein a smaller gap exists between a bottom surface of the thermal element and the external substrate than a larger gap that exists between a bottom surface of the electrical element and the PCB.

35. The light emitting device package according to claim 33, wherein the second distance is greater than the first distance by greater than 100 μ

m.

36. The light emitting device package according to claim 31, wherein the notch comprises a width and is configured for receiving at least a portion of the thermal element that substantially corresponds to the width of the notch.

37. The light emitting device package according to claim 31 wherein the notch extends partially through the substrate.

38. The light emitting device package according to claim 31 wherein the notch extends entirely through the substrate.

39. The light emitting device package according to claim 38 further comprising a heat sink and wherein the thermal element of the body extends through the notch of the substrate and is in thermal contact with the heat sink.

40. The light emitting device package according to claim 39 further comprising a heat transfer layer disposed adjacent the substrate and between the thermal element and the heat sink.

41. A light emitting device package, the package comprising:

a body having at least one electrical element and at least one thermal element, the at least one electrical and thermal elements having bottom surfaces;

at least one light emitting device mounted on a top surface of the thermal element and electrically connected to the electrical element; and

the thermal element having a first exposed portion disposed above a bottom surface of the electrical element and a second exposed portion disposed below the bottom surface of the electrical element, and the bottom surface of the electrical element extending away from the body a first distance and the bottom surface of the thermal element extending away from the body a second distance that is greater than the first distance.

42. The light emitting device package according to claim 41, wherein the body comprises a recess and at least a portion of the thermal element is disposed in the recess.

43. The light emitting device package according to claim 41, wherein the at least one light emitting device comprises a light emitting diode (LED).

44. The light emitting device package according to claim 41, wherein the body comprises at least two electrical elements having top and bottom surfaces.

45. The light emitting device package according to claim 44, wherein the electrical elements comprise portions which extend outside of the body to form an electrical contact with an external source.

46. The light emitting device package according to claim 45, wherein the external source comprises a printed circuit (PCB), and the electrical contact is formed by wetting the bottom surface of the electrical elements with solder.

47. The light emitting device package according to claim 41, wherein the bottom surface of the thermal element connects to a printed circuit board (PCB).

48. The light emitting device package according to claim 47, wherein the bottom surface of the thermal element connects to the PCB by wetting the bottom surface of the thermal element with solder.

49. The light emitting device package according to claim 41, wherein the body comprises a molded plastic body with plastic molded about the at least one thermal and electrical elements.

50. The light emitting device package according to claim 44, wherein the electrical elements protrude from the body and extend away from the body in opposing directions.

51. The light emitting device package according to claim 44, wherein the electrical elements extend from the body and toward each other.

52. The light emitting device package according to claim 44, wherein the electrical elements extend from a bottom surface of the body.

53. The light emitting device package according to claim 41, wherein the bottom surface of the thermal element is attached to a PCB by wetting the bottom surface of the thermal element with solder to form a solder joint.

54. The light emitting device package according to claim 53, wherein the solder comprises a metal paste comprising gold, tin, silver, lead, copper, flux, and any combination thereof.

55. The light emitting device package according to claim 54, wherein the solder joint is essentially free of voids.

56. The light emitting device package according to claim 55, wherein the package has improved heat transfer between the bottom surface of the thermal element and the PCB.