Leadframe-based packages for solid state light emitting devices and methods of forming leadframe-based packages for solid state light emitting devices

• US 20080121921A1
• Filed: 07/13/2006
• Published: 05/29/2008
• 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: Keller, Bernd, Loh, Ban P., Medendorp, Nicholas W.
• Granted Patent: US 7,960,819 B2
• Time in Patent Office: Days
• US Class Current: 257/99
• 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 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2224/73265 Layer and 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 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01068 Erbium [Er]
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/3011 Impedance
• 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 33/642 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 having a top surface and including a central region having a bottom surface and having a first thickness between the top surface of the leadframe and the bottom surface of the central region. The leadframe may further include an electrical lead extending away from the central region. The electrical lead has a bottom surface and has a second thickness from the top surface of the leadframe to the bottom surface of the electrical lead. The second thickness may be less than the first thickness. The package further includes a package body on the leadframe surrounding the central region and exposing the bottom surface of the central region. The package body may be at least partially provided beneath the bottom surface of the lead and adjacent the bottom surface of the central region. Methods of forming modular packages and leadframes are also disclosed.

Claims

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

a leadframe having a top surface and including a central region having a bottom surface and having a first thickness between the top surface of the leadframe and the bottom surface of the central region, the leadframe further including an electrical lead extending laterally away from the central region, the electrical lead having a bottom surface and a second thickness from the top surface of the leadframe to the bottom surface of the electrical lead adjacent the central region, wherein the second thickness is less than the first thickness; and

a package body on the leadframe surrounding the central region and exposing the bottom surface of the central region;

wherein the package body is at least partially provided beneath the bottom surface of the lead and adjacent the bottom surface of the central region.

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

3. The modular package of claim 2, wherein the upper sidewalls include oblique inner surfaces that define a reflector cup surrounding the die mounting region.

4. The modular package of claim 3, further comprising an encapsulant above the reflector cup, the encapsulant defining a lens above the reflector cup.

5. The modular package of claim 2, further comprising a circumferential rim surrounding the die mounting region, and a lens on the circumferential rim.

6. The modular package of claim 5, further comprising a circumferential moat surrounding the circumferential rim.

7. The modular package of claim 1, wherein the package body defines an optical cavity above the top surface of the leadframe, and at least a portion of the package body extends through the leadframe.

8. The modular package of claim 1, wherein the central 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 central region is greater than the second thickness.

9. The modular package of claim 8, wherein a width of the central region is greater than a width of the base of the reflector cup.

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

11. The modular package of claim 8, further comprising a submount on the base of the reflector cup, a solid state light emitting device on the submount, and a wirebond connection fi-om the solid state light emitting device to the electrical lead.

12. The modular package of claim 8, wherein the package body includes upper sidewalls that define an optical cavity above the reflector cup.

13. The modular package of claim 12, 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.

14. The modular package of claim 12, further comprising a encapsulant above the reflector cup, the encapsulant forming a lens above the reflector cup.

15. The modular package of claim 8, further comprising a circumferential rim surrounding the reflector cup and a lens on the circumferential rim.

16. The modular package of claim 15, further comprising a circumferential moat surrounding the circumferential rim.

17. The modular package of claim 1, wherein the package body has a bottom surface that is substantially coplanar with the bottom surface of the central region of the leadframe.

18. The modular package of claim 1, further comprising a plurality of electrical leads, wherein the central region comprises a plurality of die 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.

19. The modular package of claim 1, wherein the leadframe has a thickness less than 30 mils.

20. The modular package of claim 19, wherein the leadframe has a thickness of about 15 mils.

21. A leadframe for a package for a light emitting device, comprising:

a top surface;

a central region having a bottom surface and having a first thickness between the top surface of the leadframe and the bottom surface of the central region; and

an electrical lead extending laterally away from the central region, the electrical lead having a bottom surface and a second thickness from the top surface of the leadframe to the bottom surface of the electrical lead adjacent the central region, wherein the second thickness is less than the first thickness.

22. The leadframe of claim 21, wherein the central 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 central region is greater than the second thickness.

23. The leadframe of claim 22, wherein a width of the central region is greater than a width of the base of the reflector cup.

24. The leadframe of claim 22, wherein a width of the central region is greater than or equal to a width of the reflector cup at the upper corner thereof.

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

providing a leadframe having a top surface and including a central region having a bottom surface and having a first thickness between the top surface of the leadframe and the bottom surface of the central region and including an electrical lead extending laterally away from the central region, the electrical lead having a bottom surface and a second thickness from the top surface of the leadframe to the bottom surface of the electrical lead adjacent the central region, wherein the second thickness is less than the first thickness; and

forming a package body on the leadframe surrounding the central region and exposing the bottom surface of the central region;

wherein the package body is at least partially formed beneath the bottom surface of the lead and adjacent the bottom surface of the central region.

26. The method of claim 25, wherein the central region comprises a die mounting region, and wherein the package body includes upper sidewalls that define an optical cavity above the die mounting region and that include oblique inner surfaces that define a reflector cup surrounding the die mounting region, the method further comprising dispensing an encapsulant in the reflector cup.

27. The method of claim 26, wherein the encapsulant forms a lens above the reflector cup.

28. The method of claim 26, further comprising positioning a lens above the reflector cup.

29. The method of claim 28 wherein the package body further includes a circumferential rim surrounding the die mounting region, and wherein positioning the lens above the reflector cup comprises bringing the lens into contact with the circumferential rim.

30. The method of claim 25, wherein the central 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 central 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.

31. The method of claim 30, wherein forming the package body comprises forming the package body to expose a bottom surface of the central region of the leadframe.

32. The method of claim 30, further dispensing an encapsulant into the reflector cup.

33. The method of claim 32, wherein the encapsulant forms a lens above the reflector cup.

34. The method of claim 32, wherein the package body further includes a circumferential rim surrounding the central region, the method further comprising bringing a lens into contact with the circumferential rim.

35. A method of forming a leadframe for a solid state light emitting package, comprising:

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

stamping a reflector cup into the central region.

36. The method of claim 35, wherein stamping the reflector cup into the central 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 central region;

and

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

37. The method of claim 36, further comprising trimming excess material squeezed out while stamping the reflector cup from the leadframe blank.

38. The method of claim 37, 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 central region is greater than the second thickness.

39. The method of claim 38, wherein a width of the central region is greater than a width of the base of the reflector cup.

40. The leadframe of claim 38, wherein a width of the central region is greater than or equal to a width of the reflector cup at the upper corner thereof.

41-44. -44. (canceled)