LEADFRAME-BASED PACKAGES FOR SOLID STATE LIGHT EMITTING DEVICES AND METHODS OF FORMING LEADFRAME-BASED PACKAGES FOR SOLID STATE LIGHT EMITTING DEVICES

• US 20120012879A1
• Filed: 09/23/2011
• Published: 01/19/2012
• Est. Priority Date: 07/13/2006
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Loh, Ban P., Medendorp, Nicholas W. Jr., Tarsa, Eric, Keller, Bernd
• Granted Patent: US 8,941,134 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/32257 the layer connector connecting to a bonding area disposed in a recess of the surface of the item
• 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 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 23/49861 Lead-frames fixed on or encapsulated in insulating substrates H01L23/4985, H01L23/49805 take precedence
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• 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 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01068 Erbium [Er]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H01L 33/483 Containers
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H01L 33/641 : characterized by the materials
• 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

A modular package for a light emitting device includes a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness. The leadframe further includes an electrical lead extending laterally away from the second region, and the package further includes a thermoset package body on the leadframe and surrounding the first region. The thermoset package body may be on both the top and bottom surfaces of the second region. A leak barrier may be on the leadframe, and the package body may be on the leak barrier. Methods of forming modular packages including thermoset package bodies on leadframes are also disclosed.

Claims

1. A modular package for a light emitting device, comprising:

a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness, the leadframe further including an electrical lead extending laterally away from the second region; and

a thermoset package body on the leadframe and surrounding the first region, wherein the thermoset package body is on the top and bottom surfaces of the second region.

2. The modular package of claim 1, wherein the second region comprises a recess in the leadframe, wherein the thermoset package body at least partially fills the recess.

3. The modular package of claim 1, wherein the first region comprises a mounting region, and wherein the electrical lead is isolated from the mounting region, and wherein the thermoset package body includes upper sidewalls that define an optical cavity above the mounting region.

4. The modular package of claim 3, wherein the upper sidewalls include oblique inner surfaces that define a reflector cup surrounding the mounting region, the package further comprising an encapsulant in the reflector cup.

5. The modular package of claim 1, wherein at least a portion of the thermoset package body extends through the leadframe.

6. The modular package of claim 1, wherein the first region includes a reflector cup therein, the reflector cup including oblique sidewalls extending from an upper corner of the reflector cup to a base of the reflector cup;

wherein a third thickness between the base of the reflector cup and the bottom surface of the first region is greater than the second thickness.

7. The modular package of claim 6, wherein a width of the first region is greater than a width of the base of the reflector cup.

8. The modular package of claim 6, wherein a width of the first region is greater than or equal to a width of the reflector cup at the upper corner thereof.

9. The modular package of claim 6, further comprising a submount on the base of the reflector cup, a solid state light emitting device on the submount, and a wirebond connection from the solid state light emitting device to the electrical lead.

10. The modular package of claim 6, wherein the thermoset package body includes upper sidewalls that define an optical cavity above the reflector cup.

11. The modular package of claim 10, wherein the reflector cup comprises a first reflector cup and wherein the upper sidewalls include oblique inner surfaces that define a second reflector cup surrounding the first reflector cup.

12. The modular package of claim 1, wherein the thermoset package body has a bottom surface that is substantially coplanar with the bottom surface of the first region.

13. The modular package of claim 1, further comprising a plurality of electrical leads, wherein the first region comprises a plurality of mounting pads that are electrically connected to respective ones of the plurality of electrical leads and that are configured to receive a light emitting device.

14. The modular package of claim 1, wherein the thermoset package body comprises a thermoset plastic.

15. A method of forming a package for a solid state light emitting device, comprising:

providing a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness, the leadframe further including an electrical lead extending laterally away from the second region;

placing the leadframe into a mold having a mold cavity;

dispensing a thermoset precursor material into the mold cavity;

applying pressure to the mold; and

curing the thermoset precursor material to form a thermoset package body on the leadframe.

16. The method of claim 15, wherein the thermoset package body exposes the bottom surface of the first region, and wherein the thermoset package body is at least partially formed beneath a bottom surface of the electrical lead.

17. The method of claim 15, wherein the first region comprises a mounting region, and wherein the thermoset package body includes upper sidewalls that define an optical cavity above the mounting region and that include oblique inner surfaces that define a reflector cup surrounding the mounting region, the method further comprising dispensing an encapsulant in the reflector cup.

18. The method of claim 17, wherein the thermoset package body further includes a circumferential rim surrounding the first region, and wherein positioning the lens above the reflector cup comprises bringing the lens into contact with the circumferential rim.

19. The method of claim 18, wherein the first region includes a reflector cup therein, the reflector cup including oblique sidewalls extending from an upper corner of the reflector cup to a base of the reflector cup, wherein a third thickness between the base of the reflector cup and the bottom surface of the first region is greater than the second thickness, the method further comprising positioning a submount on the base of the reflector cup, positioning a solid state light emitting device on the submount, and forming a wirebond connection from the solid state light emitting device to the electrical lead.

20. The method of claim 19, wherein forming the thermoset package body comprises forming the thermoset package body to expose a bottom surface of the first region of the leadframe.

21. The method of claim 15, wherein providing the leadframe comprises:

providing a leadframe blank having a top surface, a first region having a bottom surface and having a first thickness between the top surface of the leadframe blank and the bottom surface of the first region, and a portion extending laterally away from the first region, the portion extending laterally away from the first region having a bottom surface and a second thickness adjacent the first region from the top surface of the leadframe to the bottom surface of the portion extending away from the first region, wherein the second thickness is less than the first thickness; and

stamping a reflector cup into the first region.

22. The method of claim 21, wherein stamping the reflector cup into the first region comprises bringing a stamp including a protrusion having a shape defining a desired shape of the reflector cup into contact with the upper surface of the leadframe blank above the first region;

and

applying sufficient energy to the stamp to impress an image of the protrusion into the first region of the leadframe blank.

23. The method of claim 22, further comprising trimming excess material squeezed out while stamping the reflector cup from the leadframe blank.

24. The method of claim 23, wherein the reflector cup includes oblique sidewalls extending from an upper corner of the reflector cup to a base of the reflector cup;

and

wherein a third thickness between the base of the reflector cup and the bottom surface of the first region is greater than the second thickness.

25. The method of claim 15, wherein providing the leadframe comprises:

providing a leadframe blank having a top surface and a bottom surface; and

selectively etching, rolling and/or milling the leadframe blank to provide a first region having a bottom surface and having a first thickness between the top surface of the leadframe blank and the bottom surface of the region, and a second region having a bottom surface and a second thickness from the top surface of the leadframe to the bottom surface of the second region, wherein the second thickness is less than the first thickness.

26. The method of claim 25, wherein selectively etching, rolling and/or milling the leadframe blank comprises selectively etching, rolling and/or milling the leadframe blank to form a recess in the leadframe.

27. The method of claim 15, wherein dispensing the thermoset precursor material comprises dispensing a thermoset plastic precursor material.

28. A modular package for a light emitting device, comprising:

a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness, the leadframe further including an electrical lead extending laterally away from the second region and a leak barrier on a surface of the first region or a surface of the second region; and

a package body on the leadframe and surrounding the first region, wherein the package body is on the top and bottom surfaces of the second region, and wherein the package body is on the leak barrier.

29. The modular package of claim 28, wherein the leak barrier comprises a notch or groove in the leadframe, wherein the package body is at least partially within the notch or groove.

30. The modular package of claim 28, wherein the leak barrier comprises a protrusion on the leadframe, wherein the package body is on the protrusion.

31. The modular package of claim 28, wherein the package body comprises a thermoset.

32. The modular package of claim 28, wherein the second region comprises a recess in the leadframe, wherein the thermoset package body at least partially fills the recess.

33. The modular package of claim 28, wherein the first region comprises a mounting region on the top surface thereof, wherein the leak barrier is on the top surface of the first region outside the mounting region, and wherein the package body is on the leak barrier.

34. The modular package of claim 33, wherein the package body includes upper sidewalls that define an optical cavity above the mounting region, and wherein the upper sidewalls include oblique inner surfaces that define a reflector cup surrounding the mounting region, the package further comprising an encapsulant in the reflector cup.

35. The modular package of claim 28, wherein the leak barrier is on the electrical lead.

36. The modular package of claim 28, wherein the leadframe includes a support lead, wherein the leak barrier is on the support lead.

37. The modular package of claim 28, wherein the first region includes a sidewall between the top surface and the bottom surface thereof, and wherein the leak barrier is on the sidewall.

38. The modular package of claim 37, wherein the leak barrier comprises a protrusion from the sidewall.

39. The modular package of claim 28, wherein the first region includes a sidewall between the top surface and the bottom surface thereof, the package further comprising a peripheral notch on a corner of the first region adjacent the bottom surface thereof, wherein the package body at least partially fills the peripheral notch and exposes the bottom surface of the first region.

40. A method of forming a package for a solid state light emitting device, comprising:

providing a leadframe including a first region having a top surface, a bottom surface and a first thickness and a second region having a top surface, a bottom surface and a second thickness that is less than the first thickness, the leadframe further including an electrical lead extending laterally away from the second region and a leak barrier on a surface of the first region or the second region;

placing the leadframe into a mold having a mold cavity;

dispensing a precursor material into the mold cavity;

applying pressure to the mold; and

curing the precursor material to form a package body on the leadframe, wherein the package body is on the leak barrier.

41. The method of claim 40, wherein the package body comprises a thermoset.

42. The method of claim 40, wherein the package body exposes the bottom surface of the first region, and wherein the package body is at least partially formed beneath a bottom surface of the electrical lead.

43. The method of claim 40, wherein the first region comprises a mounting region on the top surface thereof, and wherein the package body includes upper sidewalls that define an optical cavity above the mounting region and that include oblique inner surfaces that define a reflector cup surrounding the mounting region, the method further comprising dispensing an encapsulant in the reflector cup.

44. The method of claim 40, wherein the leak barrier comprises a notch or groove in the leadframe, wherein the package body is at least partially formed within the notch or groove.

45. The method of claim 40, wherein the leak barrier comprises a protrusion on the leadframe, wherein the package body is formed on the protrusion.

46. The method of claim 40, wherein the second region comprises a recess in the leadframe, wherein the package body at least partially fills the recess.

47. The method of claim 40, wherein the first region comprises a mounting region on the top surface thereof, wherein the leak barrier is on the top surface of the first region outside the mounting region, and wherein the package body is formed on the leak barrier.

48. The method of claim 40, wherein the leak barrier is on the electrical lead.

49. The method of claim 40, wherein the leadframe includes a support lead, wherein the leak barrier is on the support lead.

50. The method of claim 40, wherein the first region includes a sidewall between the top surface and the bottom surface thereof, and wherein the leak barrier is formed on the sidewall.

51. The method of claim 50, wherein the leak barrier comprises a protrusion from the sidewall.