Method of cooling an electronic power module using a high performance heat exchanger incorporating metal foam therein

• US 6,397,450 B1
• Filed: 05/12/2000
• Issued: 06/04/2002
• Est. Priority Date: 06/17/1998
• Status: Expired due to Fees

• Current Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Ozmat, Burhan
• Primary Examiner(s): Bryant, David P.
• Application Number:
  US09/570,009
• Time in Patent Office: 753 Days
• Field of Search: 165/80.1, 165/80.2, 165/80.3, 165/80.4, 165/80.5, 165/133, 165/185, 165/907, 298/900.35, 298/900.54, 294/28, 228/173.1
• US Class Current: 29/428
• CPC Class Codes: F28F 13/003 by using permeable mass, perforated or porous materials F28F13/18 takes precedence
• CPC Class Codes: H01L 23/3733 having a heterogeneous or anisotropic structure, e.g. powder or fibres in a matrix, wire mesh, porous structures H01L23/3732, H01L23/3737 take precedence
• CPC Class Codes: H01L 23/473 by flowing liquids H01L23/4332, H01L23/4338 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: Y10S 165/907 Porous
• CPC Class Codes: Y10T 29/49359 Cooling apparatus making, e.g., air conditioner, refrigerator
• CPC Class Codes: Y10T 29/49393 with metallurgical bonding
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

A heat exchanger and method for cooling power electronics modules. The power electronics module transferring heat generated during operation to the heat exchanger through a thermal base of the power module. The heat exchanger being directly bonded to the thermal base and comprising a metal foam. The metal foam having a network of metal ligaments forming numerous open cells to provide porosity. The metal ligaments are aligned to provide a higher metal density in cross-sectional planes of the foam perpendicular to the intended direction of heat flow.

Claims

1. A method of cooling an electronic power module comprising the steps of:

(a) providing a block of metal foam in a heat transfer relationship to the module to be cooled, the metal foam having a network of ligaments forming randomly distributed open pores, each of the pores having an approximately spherical shape which is elongated in a direction orthogonal to a surface of the module;

(b) bonding the block to the surface of the module;

(c) directing a fluid coolant through the pores of the foam to remove heat in a substantially perpendicular direction to the surface of the module through the network of ligaments.

2. The method of claim 1 wherein the bonding of the block is direct to the flat surface of the module by a thermally conducting bonding material,

wherein the metal of the block and the material of the module have substantially different coefficients of thermal expansion, and

wherein the structural compliance of the block is such that the physical integrity of the block, the module, and the bond between said block and module is not substantially degraded by temperature variations.

3. The method of claim 1 wherein the bond is thermally conducting.

4. The method of claim 3 wherein the bond is formed by brazing.

5. The method of claim 3 wherein the bond is formed by soldering.

6. The method of claim 1 wherein the foam of the block has a porosity of between about 5 and about 50 pores per inch.

7. The method of claim 1 wherein the foam of the block has a volumetric density of between about 2% and 50%.

8. The method of claim 7 wherein the foam of the block has total surface area of between about 2 and about 300 inches squared per cubic inch of foam.

9. The method of claim 1 further comprising the steps of:

providing a foam having network of ligaments forming pores of equiaxed shape; and

compressing the foam to elongate the pores and increase the density of ligaments perpendicular to the surface of the foam.

10. The method of claim 9 wherein the foam is biaxially compressed.

11. The method of claim 1 wherein the step of providing a block of metal foam is formed by providing plural strips of metal foam positioned in series,

each of the strips having a bonding surface.

12. The method of claim 1 wherein the ligaments are formed from a metal from a group consisting of aluminum, copper, and silver.

13. The method of claim 11 wherein the foam is for providing a junction to ambient thermal resistance of up to about 0.12°

C./Watt for a 1 inch surface contact.

14. A method of cooling an electronic power module comprising the steps of:

(a) providing a power module having a flat surface;

(b) providing a block of metal foam in a heat transfer relationship to the module to be cooled, the metal foam having numerous void cells randomly distributed in the foam with the void cells having an orientation perpendicular to the flat surface of the module and having openings for passing a fluid coolant from cell to cell parallel to the flat surface;

(c) bonding the block to the flat surface of the module;

(d) directing a fluid coolant through the void cells of the foam in a generally parallel direction to the flat surface of the module to remove heat.

15. The method of claim 14 wherein the bonding of the block is direct to the flat surface of the electronic module by a thermally conducting bonding material,

wherein the metal of the block and the material of the module have substantially different coefficients of thermal expansion, and

wherein the structural compliance of the block is such that the physical integrity of the block, the module, and the bond between the block and the module is not substantially degraded by temperature variations.

16. The method of claim 14 wherein the metal of the block is one of the group consisting of aluminum, copper, and silver.

17. The method of claim 14 wherein the block is between about 0.050 inches and about 1.000 inch in thickness.

18. The method of claim 14 wherein the foam of the block has a porosity between about 5 and about 100 voids per inch.

19. The method of claim 14 wherein the bond is thermally conducting.

20. The method of claim 19 wherein the bond is formed by brazing.

21. The method of claim 19 wherein the bond is formed by soldering.

22. The method of claim 14 wherein the block is adapted to bond directly to a metallized ceramic surface of the module.

23. The method of claim 14 wherein the block is adapted to bond directly to a metal surface of the module.

24. The method of claim 14 wherein the step of providing a block of metal foam is formed by providing plural strips of metal foam positioned in series,

each of the strips having a bonding surface.

25. The method of claim 14 further comprising the steps of:

providing a foam having void cells of equiaxed shape; and

compressing the foam to elongate the cells and increase the density of the foam perpendicular to the surface of the module.

26. The method of claim 25 wherein the foam is uniaxially compressed.

27. The method of claim 25 wherein the foam is axially compressed.

28. A method of cooling an electronic power module by providing an integrated heat sink/thermal base plate assembly comprising the steps of:

(a) providing a block of metal foam having a bonding surface;

(b) providing a thermal base plate of an electronic module made of a material from the group of a metal, metal matrix compound, and ceramic, where the base plate is coated with metallization for direct bonding with the bonding surface of the block;

(c) bonding the block to the base plate;

(d) providing a casing for housing the block having paths for directing a coolant through the casing parallel to the base plate;

(e) sealing the casing to the base plate;

(f) directing a fluid coolant through the casing in a generally parallel direction to the base plate to remove heat.

29. The method of claim 28 wherein the step of providing a block of metal foam is formed by providing plural strips of metal foam positioned in series,

each of the strips having a bonding surface.

30. The method of claim 28 wherein the casing is primarily formed from a metal.

31. The method of claim 28 wherein the casing is primarily formed from a material which is one of a group consisting of a polymer, a metal, a composite polymer, and a composite metal.

32. The method of claim 28 wherein the casing comprises plural manifolds as paths for directing a coolant through the casing.

33. The method of claim 28 wherein the bond is formed by brazing.

34. The method of claim 28 wherein the bond is formed by soldering.

35. The method of claim 28 wherein the block and base plate are directly bonded through a thermally conducting bonding material.

36. The method of claim 28 wherein the block of metal foam has numerous void cells randomly distributed in the foam with the void cells having an orientation perpendicular to the flat surface of the module and having openings for passing a fluid coolant from cell to cell parallel to the flat surface.

37. The method of claim 36 wherein the block is between about 0.050 inches and about 1.000 inch in thickness.

38. The method of claim 36 wherein the foam of the block has a porosity between about 5 and about 50 voids per inch.

39. The method of claim 28 wherein the foam comprises a network of metal ligaments forming numerous randomly distributed elongated substantially ellipsoidal shaped voids of approximately the same size oriented in a first direction, the ligaments having gaps for passing the fluid coolant through adjacent of the voids, and a higher ligament density in a direction generally perpendicular to the first direction than in a direction generally parallel to the first direction.

40. The method of claim 39 wherein the foam of the block has a porosity between about 5 and about 100 voids per inch.

41. The method of claim 39 wherein the foam of the block has a volumetric density of between 2% and 50%.

42. The method of claim 39 wherein the foam is for providing a junction to ambient thermal resistance of up to about 0.12°

C./Watt for a 1 inch surface contact.

43. The method of claim 28 further comprising the steps of:

providing a foam having void cells of equiaxed shape; and

compressing the foam to elongate the cells and increase the density of the foam perpendicular to the surface of the module.

44. The method of claim 43 wherein the foam is uniaxially compressed.

45. The method of claim 43 wherein the foam is axially compressed.