Electrical bus with associated porous metal heat sink and method of manufacturing same

• US 20030218057A1
• Filed: 03/04/2003
• Published: 11/27/2003
• Est. Priority Date: 11/07/2000
• Status: Abandoned Application

• Current Assignee: Anthony C. Evans, Craig Joseph, Dorsch T. James, Kelly W. Arnold
• Original Assignee: Anthony C. Evans, Craig Joseph, Dorsch T. James, Kelly W. Arnold
• Inventors: Joseph, Craig, Arnold, Kelly W., Dorsch, T. James, Evans, Anthony C.
• Application Number:
  US10/382,286
• Publication Number:
  US 20030218057A1
• Time in Patent Office: Days
• US Class Current: 228/183
• CPC Class Codes: B23K 1/0012 Brazing heat exchangers
• CPC Class Codes: B23K 2101/14 Heat exchangers
• CPC Class Codes: B23K 2101/34 Coated articles , e.g. plated or painted; Surface treated articles
• CPC Class Codes: B23K 2103/12 Copper or alloys thereof
• CPC Class Codes: B23K 2103/18 Dissimilar materials
• CPC Class Codes: B23K 2103/26 Alloys of Nickel and Cobalt and Chromium
• CPC Class Codes: B23K 31/02 relating to soldering or welding dip or wave soldering in the manufacture of printed circuits H05K3/34
• CPC Class Codes: F28F 13/003 by using permeable mass, perforated or porous materials F28F13/18 takes precedence
• CPC Class Codes: F28F 3/12 Elements constructed in the shape of a hollow panel, e.g. with channels F28D1/02, F28D1/03 take precedence
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H02M 7/003 Constructional details, e.g. physical layout, assembly, wiring or busbar connections
• CPC Class Codes: H05K 7/14329 specially adapted for the configuration of power bus bars
• CPC Class Codes: H05K 7/20927 Liquid coolant without phase change

Abstract

A module is formed in which semiconductor components are soldered to an electrically conductive heat sink. The electrically conductive heat sink is formed so that it will serve as an electrical bus in an electronic device. The chips of the semiconductor component are metallurgically bonded to the surface of the heat sink. The heat sink uses a heat transfer fluid that flows through an interior of the heat sink, the interior containing an internal element. In the preferred embodiment, the internal element is a plurality of silver plated copper balls. The copper balls are brazed to each other and to the walls of the heat sinks in an assembly process. The heat sink housing will typically be made from copper, with one surface made from molybdenum so that the expansion and contraction of the heat sink housing molybdenum surface will be similar to that of the silicon substrate of the chips, thereby avoiding the problem of the chip substrate cracking and breaking due to thermal flexing.

Claims

1. A process for forming a heat sink comprising:

a) nickel plating exterior and interior surfaces of a heat sink housing,

b) subjecting said molybdenum components of said nickel plated heat sink housing to a thermal diffusion process,

c) silver plating a metallic internal element with a plurality of throughways therein,

d) placing said internal element in an interior of said heat sink housing,

e) securing said heat sink housing in a brazing fixture, and

e) thermally processing said heat sink housing and said internal element, such that

said silver layer and surface metal material of said internal element liquefies to form a bond between adjacent components of said internal element and to any contacting surfaces of said heat sink housing, and to form a bond between the adjacent components of said heat sink housing.

2. The process of claim 1 wherein:

said thermal processing comprises;

a) heating said heat sink housing and said internal element to 1,000°

F.±

25°

F. in sixty minutes,

b) holding said heat sink housing and said internal element at 1,000°

F.±

25°

F. for twenty minutes,

c) heating said heat sink housing and said internal element to 1,400°

F.±

15°

F. in thirty minutes,

d) holding said heat sink housing and said internal element at 1,400°

F.±

15°

F. for twenty minutes,

e) heating said heat sink housing and said internal element to 1,500°

F.±

10°

F. in five minutes,

f) holding said heat sink housing and said internal element at 1,500°

F.±

10°

F. for ten minutes, and

g) furnace cooling said heat sink housing and said internal element to 500°

F.

3. The process of claim 1 wherein:

nickel plating of said exterior and interior surfaces of said heat sink housing is accomplished by an electrodeposit process.

4. The process of claim 1 wherein:

nickel plating of said exterior and interior surfaces of said heat sink housing is accomplished by an electroless process.

5. The process of claim 1 wherein:

said thermal diffusion process is performed at 1436-1472°

F.

6. The process of claim 5 wherein:

said thermal diffusion is performed in a hydrogen atmosphere.

7. The process of claim 5 wherein:

said thermal diffusion is performed in a vacuum.

8. The process of claim 1 wherein:

said internal element is made of copper

9. The process of claim 1 wherein:

said internal element is chemically milled prior to silver plating.

10. The process of claim 1 wherein:

said silver plating process deposits a layer of dull silver 0.0005 to 0.0010 inch thick on said internal element.

11. The process of claim 1 wherein:

end manifolds of said heat sink housing are secured to a main body of said heat sink housing during said thermal processing.

12. The process of claim 8 wherein:

said end manifolds of said heat sink housing are secured to said main body of said heat sink housing through the use of brazing sheet.

13. The process of claim 1 wherein:

the mounting surface of said heat sink is secured to a main body of said heat sink housing during said thermal processing.

14. The process of claim 10 wherein:

said mounting surface of said heat sink housing is secured to said main body of said heat sink housing through the use of brazing sheet.

15. The process of claim 1 wherein:

a mounting surface of said heat sink housing is secured to a main body of said heat sink housing during said thermal processing.

16. The process of claim 1 wherein:

said internal element comprises a plurality of metal balls.

17. The process of claim 16 wherein:

said metal balls are made of copper.

18. The process of claim 16 wherein:

said metal balls are chemically milled prior to silver plating.

19. The process of claim 1 wherein:

said internal element comprises a metallic block with said plurality of throughways machined therein.

20. The process of claim 1 wherein:

said internal element comprises a metal foam.

21. The process of claim 1 wherein:

said internal element comprises a metal wool.

22. The process of claim 1 wherein:

said internal element comprises a metal felt.

23. The process of claim 1 wherein:

at least one surface of said housing is formed from molybdenum.

24. A process for forming a heat sink comprising:

a) nickel plating exterior and interior surfaces of a heat sink housing with a plurality of throughways therein,

b) subjecting molybdenum components of said nickel plated heat sink housing to a thermal diffusion process,

c) silver plating an internal element so that a silver layer is formed on an exterior of said internal element,

d) placing said internal element in an interior of said heat sink housing,

e) securing said heat sink housing in a brazing fixture,

f) heating said heat sink housing and said internal element to 1,000°

F.±

25°

F. in sixty minutes,

g) holding said heat sink housing and said internal element at 1,000°

F.±

25°

F. for twenty minutes,

h) heating said heat sink housing and said internal element to 1,400°

F.±

15°

F. in thirty minutes,

i) holding said heat sink housing and said internal element at 1,400°

F.±

15°

F. for twenty minutes,

j) heating said heat sink housing and said internal element to 1,500°

F.±

10°

F. in five minutes,

k) holding said heat sink housing and said internal element at 1,500°

F.±

10°

F. for ten minutes, and

l) furnace cooling said heat sink housing and said internal element to 500°

F.;

such that

said silver layer and surface copper material of said internal element liquifies to form a bond with adjacent components of said internal element and to any contacting surfaces of said heat sink housing, and a bond between the adjacent components of said heat sink housing is formed.

25. The process of claim 24 wherein:

nickel plating of exterior surfaces of said heat sink housing is accomplished by an electrodeposit process.

26. The process of claim 24 wherein:

nickel plating of exterior surfaces of said heat sink housing is accomplished by an electroless process.

27. The process of claim 24 wherein:

said thermal diffusion process is performed at 1436-1472°

F.

28. The process of claim 27 wherein:

said thermal diffusion is performed in a hydrogen atmosphere.

29. The process of claim 27 wherein:

said thermal diffusion is performed in a vacuum.

30. The process of claim 24 wherein:

said internal element comprises a plurality of metal balls.

31. The process of claim 30 wherein:

said metal balls are chemical milled prior to silver plating.

32. The process of claim 30 wherein:

said metal balls are made of copper.

33. The process of claim 30 wherein:

said silver plating process deposits a layer of dull silver 0.0005 to 0.0010 inch thick on said copper balls.

34. The process of claim 24 wherein:

said internal element comprises a metallic block with said plurality of throughways machined therein.

35. The process of claim 24 wherein:

said internal element comprises a metal foam

36. The process of claim 24 wherein:

said internal element comprises a metal wool.

37. The process of claim 24 wherein:

said internal element comprises a metal felt

38. The process of claim 24 wherein:

end manifolds of said heat sink housing are secured to a main body of said heat sink housing during said thermal processing.

39. The process of claim 38 wherein:

said end manifolds of said heat sink housing are secured to said main body of said heat sink housing through the use of brazing sheet.

40. The process of claim 24 wherein:

a mounting surface of said heat sink housing is secured to a main body of said heat sink housing during said thermal processing.

41. The process of claim 40 wherein:

said mounting surface of said heat sink housing is secured to said main body of said heat sink housing through the use of brazing sheet.