Semiconductor package having heat sinks and method of fabrication

• US 6,330,158 B1
• Filed: 06/05/2000
• Issued: 12/11/2001
• Est. Priority Date: 06/08/1998
• Status: Expired due to Fees

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Akram, Salman
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): DATSKOVSKIY, MICHAIL V
• Application Number:
  US09/587,610
• Time in Patent Office: 554 Days
• Field of Search: 361/700-712, 361/714-719, 257/706-727, 257/692-693, 257/686, 257/685, 257/797, 257/666, 174/15.1, 174/15.2, 174/16.3, 174/200, 174/201, 174/52.4, 165/80.2, 165/80.3, 165/80.4, 165/185, 298/32, 298/37
• US Class Current: 361/704
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/291 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/29111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/29144 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/2929 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/29339 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45015 being circular
• 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 2224/4826 Connecting between the body and an opposite side of the item with respect to the body
• CPC Class Codes: H01L 2224/73215 Layer and wire connectors
• CPC Class Codes: H01L 2224/83805 involving forming a eutectic alloy at the bonding interface
• CPC Class Codes: H01L 2224/85399 Material
• CPC Class Codes: H01L 23/4334 Auxiliary members in encapsulations H01L23/49568 takes precedence
• CPC Class Codes: H01L 23/4951 Chip-on-leads or leads-on-chip techniques, i.e. inner lead fingers being used as die pad
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/33 of a plurality of layer connectors
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• 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 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 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 : Silicon [Si]
• CPC Class Codes: H01L 2924/01026 : Iron [Fe]
• CPC Class Codes: H01L 2924/01028 : Nickel [Ni]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01032 : Germanium [Ge]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01042 : Molybdenum [Mo]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01055 : Cesium [Cs]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/0132 : Binary Alloys
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/0695 : Polyamide
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15738 : the principal constituent melting at a temperature of greater than or equal to 950 C and less than 1550 C
• CPC Class Codes: H01L 2924/15747 : Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2924/1576 : Iron [Fe] as principal constituent
• CPC Class Codes: H01L 2924/15763 : the principal constituent melting at a temperature of greater than 1550 C
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/207 : Diameter ranges
• CPC Class Codes: H05K 1/18 : Printed circuits structurally associated with non-printed electric components H05K1/0201, H05K1/023, H05K1/0243, and H05K1/16 take precedence
• CPC Class Codes: H05K 2201/10151 : Sensor
• CPC Class Codes: H05K 2201/10454 : Vertically mounted
• CPC Class Codes: H05K 2201/10522 : Adjacent components
• CPC Class Codes: H05K 2201/10696 : Single-in-line [SIL] package

Abstract

A semiconductor package includes a semiconductor die, a lead frame wire bonded to the die, and a plastic body encapsulating the die. The package also includes a first heat sink attached to a face of the die, and a second heat sink attached to a back side of the die. Thermally conductive adhesive layers attach the heat sinks to the die, and provide a thermal path therebetween. In addition, the heat sinks project from the plastic body, and have end portions that are sized and shaped to interlock with heat sinks on an adjacent package to form an electronic assembly. In the electronic assembly, the interlocking heat sinks maintain contact surfaces on the heat sinks in physical contact and improve heat dissipation from the packages. An alternate embodiment package includes a thermally conductive encapsulant which attaches a pair of heat sinks, and encapsulates the die.

Claims

1. A semiconductor package comprising:

a semiconductor die;

a package body at least partially encapsulating the die;

a first heat sink in thermal communication with the die and projecting from the body; and

a second heat sink in thermal communication with the die and projecting from the body, the second heat sink configured to physically engage a heat sink substantially similar to the first heat sink on a second semiconductor package substantially similar to the semiconductor package to provide a thermal path between the semiconductor package and the second semiconductor package.

2. The package of claim 1 wherein the first heat sink, or the second heat sink, comprises a ribbed surface.

3. The package of claim 1 wherein the first heat sink is generally perpendicular to a plane of the die.

4. A semiconductor package comprising:

a semiconductor die comprising a first side and a second side;

a plurality of external leads in electrical communication with the die configured for attachment to a substrate;

a first heat sink attached to the first side comprising a first contact surface;

a second heat sink attached to the second side comprising a second contact surface;

the first heat sink and the second heat sink comprising complementary elements configured to maintain the first contact surface or the second contact surface in physical contact with a heat sink on a second package.

5. The package of claim 4 wherein the first contact surface and the second contact surface comprise planar surfaces oriented along a plane generally perpendicular to the die.

6. The package of claim 4 wherein the die comprises an edge and the first heat sink or the second heat sink contacts the edge.

7. The package of claim 4 wherein the first heat sink is generally perpendicular to the first side of the die and the second heat sink is generally perpendicular to the second side of the die.

8. The package of claim 4 wherein the first heat sink is attached to a first half of the die, and the second heat sink is attached to a second half of the die.

9. A semiconductor package comprising:

a semiconductor die comprising a face and a back side;

a package body at least partially encapsulating the die;

a first heat sink in thermal communication with the face and projecting from the body; and

a second heat sink in thermal communication with the back side and projecting from the body, the second heat sink configured to physically engage a heat sink substantially similar to the first heat sink on a second package substantially similar to the package to provide a thermal path between the second package and the package.

10. The package of claim 9 further comprising a first thermally conductive adhesive layer attaching the first heat sink to the face and a second thermally conductive adhesive layer attaching the second heat sink to the back side.

11. The package of claim 9 wherein the first heat sink includes a first end portion and the second heat sink includes a second end portion, with the first end portion and the second end portion configured as complimentary elements of an interlocking structure.

12. The package of claim 9 wherein the first heat sink has a thickness about one half a width of the die and substantially covers a first half of the face, and the second heat sink has the thickness and substantially covers a second half of the back side.

13. The package of claim 9 wherein the die comprises a first edge and a second edge and the first heat sink substantially covers the first edge and the second heat sink substantially covers the second edge.

14. A semiconductor package comprising:

a semiconductor die comprising a face, a back side, and a plurality of bond pads on the face;

a lead frame attached to the face comprising a plurality of lead fingers in electrical communication with the bond pads and forming a plurality of terminal leads;

a first heat sink attached to the face and a first thermally conductive adhesive layer attaching the first heat sink to the face, the first heat sink oriented generally orthogonally to the face and proximate to a first half of the die; and

a second heat sink attached to the back side and a second thermally conductive adhesive layer attaching the second heat sink to the back side, the second heat sink oriented generally orthogonally to the back side and proximate to a second half of the die,

the first heat sink and the second heat sink configured as complimentary elements such that with the terminal leads attached to a substrate the first heat sink or the second heat sink is in thermal communication with a heat sink on a second package on the substrate substantially identical to the package.

15. The package of claim 14 wherein the first thermally conductive adhesive layer and the second thermally conductive adhesive layer comprise a material selected from the group consisting of epoxy and polyimide.

16. The package of claim 14 wherein the first thermally conductive adhesive layer and the second thermally conductive adhesive layer comprise solder.

17. The package of claim 14 wherein the first thermally conductive adhesive layer and the second thermally conductive adhesive layer comprise glass.

18. The package of claim 14 wherein the first heat sink and the second heat sink comprise a metal selected from the group consisting of copper, aluminum, molybdenum, titanium and alloys of these materials.

19. The package of claim 14 wherein the first heat sink and the second heat sink comprise a copper clad composite material.

20. A semiconductor package comprising:

a semiconductor die comprising a back side, a face, and a plurality of bond pads on the face;

a lead frame comprising a plurality of lead fingers attached to the face of the die in electrical communication with the bond pads;

a package body at least partially encapsulating the die and at least a portion of the lead frame;

a first heat sink attached to the face generally perpendicular to the face and the lead frame, the first heat sink comprising a first plate projecting from a first surface of the body; and

a second heat sink attached to the back side generally perpendicular to the back side and the lead frame, the second heat sink comprising a second plate projecting from a second surface of the body and configured to physically engage a heat sink substantially similar to the first heat sink contained on a second package substantially similar to the package to provide a thermal path between the second package and the package.

21. The package of claim 20 wherein the lead frame comprises a plurality of terminal leads projecting from a third surface of the body.

22. The package of claim 20 wherein the first heat sink or the second heat sink comprise a ribbed structure for increasing a surface area thereof.

23. The package of claim 20 wherein the first heat sink includes a first contact surface and the second heat sink includes a second contact surface.

24. The package of claim 20 wherein the first heat sink includes a first contact surface substantially planar to an axis of the package and the second heat sink includes a second contact surface substantially planar to the axis.

25. The package of claim 20 wherein the lead frame comprises a lead on chip lead frame wire bonded to the die.

26. A semiconductor package comprising:

a semiconductor die comprising a back side, a face, and a plurality of bond pads on the face;

a lead frame comprising a plurality of lead fingers attached to the face;

a plurality of wires bonded to the bond pads and to the lead fingers;

a thermally conductive adhesive encapsulating the face, the back side, the wires and at least a portion of the lead frame;

a first heat sink attached to the face by the thermally conductive adhesive; and

a second heat sink attached to the back side by the thermally conductive adhesive,

the first heat sink and the second heat sink configured as complimentary elements to provide a thermal path between the package and a second package substantially identical to the package.

27. The package of claim 26 wherein the thermally conductive adhesive comprises a material selected from the group consisting of a silver filled epoxy, a silver filled polyimide and a boron filled polymer.

28. The package of claim 26 wherein the first heat sink is generally parallel to the face and the second heat sink is generally parallel to the back side.

29. An electronic assembly comprising:

a substrate;

a first semiconductor package on the substrate comprising a die, a first heat sink projecting from and in thermal communication with the die, and a second heat sink projecting from and in thermal communication with the die; and

a second semiconductor package on the substrate substantially similar to the first semiconductor package and comprising a third heat sink substantially similar to the first heat sink physically contacting the second heat sink on the first semiconductor package to provide a thermal path between the first semiconductor package and the second semiconductor package.

30. The assembly of claim 29 wherein the first heat sink and the second heat sink comprise ribbed surfaces.

31. The assembly of claim 29 wherein the first heat sink includes a first end portion comprising a first planar contact surface and the third heat sink includes a third end portion comprising a third planar contact surface configured for physical contact with the first planar contact surface.

32. An electronic assembly comprising:

a substrate;

a plurality of semiconductor packages on the substrate, each package comprising;

a semiconductor die;

a body at least partially encapsulating the die and having a first side and an opposing second side;

a first heat sink attached to the die and projecting from the first side; and

a second heat sink attached to the die and projecting from the second side, the second heat sink configured to physically engage the first heat sink on an adjacent package to provide a thermal path to the adjacent package.

33. The assembly of claim 32 wherein the first heat sink comprises a first planar surface and the second heat sink comprises a second planar surface configured for mating engagement with the first planar surface on the adjacent die.

34. The assembly of claim 32 wherein the first heat sink comprises a first end portion and the second heat sink comprises a second end portion configured to interlock with the first end portion on the adjacent die.

35. The assembly of claim 32 wherein the first heat sink comprises a first plate having a thickness about one half a width of the die and substantially covers a first half of the die, and the second heat sink comprises a second plate having the thickness and substantially covers a second half of the die.

36. A method for fabricating a semiconductor package comprising:

providing a semiconductor die comprising a face and a back side;

providing a first heat sink and a second heat sink comprising complimentary elements configured to provide a thermal path between the package and a second package substantially identical to the package;

attaching the first heat sink to the die in thermal communication with the face;

attaching the second heat sink to the die in thermal communication with the back side; and

molding a plastic body to the lead frame to at least partially encapsulate the die leaving at least a first end portion of the first heat sink and a second end portion of the second heat sink exposed.

37. The method of claim 36 wherein attaching the first heat sink to the die comprises forming a thermally conductive adhesive layer between the face and the first heat sink.

38. The method of claim 36 further comprising mounting the package to a substrate and forming the thermal path to the second package.

39. The method of claim 36 wherein the first end portion and the second end portion comprise planar surfaces generally perpendicular to the die.

40. The method of claim 36 wherein the first end portion and the second end portion comprise ribbed surfaces.

41. A method for fabricating a semiconductor package comprising:

providing a semiconductor die comprising a face and a back side;

attaching a first heat sink to the face using a first thermally conductive adhesive layer, the first heat sink oriented generally orthogonally to the face and having a first contact surface;

attaching a second heat sink to the back side using a second thermally conductive adhesive layer, the second heat sink oriented generally orthogonally to the back side and having a second contact surface configured for physical contact with a contact surface of a heat sink substantially similar to the first heat sink contained on a second package substantially similar to the package to provide a thermal path between the second package and the package; and

molding a plastic body to the lead frame to at least partially encapsulate the die leaving the first contact surface and the second contact surface exposed.

42. The method of claim 41 wherein the first contact surface and the second contact surface comprise planar surfaces parallel to an axis of the package.

43. The method of claim 41 wherein the first contact surface and the second contact surface comprise complimentary elements of an interlocking structure.