Heat sink and method of making the same

• US 20050199371A1
• Filed: 03/15/2004
• Published: 09/15/2005
• Est. Priority Date: 03/15/2004
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kemink, Randall G., Singh, Prabjit
• Granted Patent: US 7,100,281 B2
• Time in Patent Office: Days
• US Class Current: 165/80.3
• CPC Class Codes: B23K 1/0012 Brazing heat exchangers
• CPC Class Codes: B23K 1/19 taking account of the properties of the materials to be soldered
• CPC Class Codes: B23K 2101/08 finned or ribbed
• CPC Class Codes: F28F 21/085 from copper or copper alloys
• CPC Class Codes: F28F 2275/06 by welding welding heat exchangers B23K2101/14
• CPC Class Codes: F28F 3/02 Elements or assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with recesses, with corrugations F28F3/08 takes precedence
• CPC Class Codes: H01L 21/4882 Assembly of heatsink parts
• CPC Class Codes: H01L 23/3672 Foil-like cooling fins or heat sinks being part of lead-frames H01L23/49568
• 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: Y10T 29/4935 Heat exchanger or boiler making
• CPC Class Codes: Y10T 29/49373 Tube joint and tube plate structure
• CPC Class Codes: Y10T 29/4938 Common fin traverses plurality of tubes
• CPC Class Codes: Y10T 29/49393 with metallurgical bonding

Abstract

A method for manufacturing a heat sink including heating a metal base to melt solder in grooves formed in the base. The base has a first coefficient of thermal expansion. The solder has a second coefficient of thermal expansion lower than the first coefficient of thermal expansion. The metal base and the solder are cooled and the metal base experiences tensile stresses and the solder experiences compressive stresses to form a concavity in a thermal face of the base. The thermal face is then planed. Over time, the tensile stresses and the compressive stresses reduce such that the thermal face becomes convex.

Claims

1. A method for manufacturing a heat sink comprising:

heating a metal base to melt solder in grooves formed in said base, said base having a first coefficient of thermal expansion, said solder having a second coefficient of thermal expansion lower than said first coefficient of thermal expansion;

positioning fins in said grooves, said fins having said first coefficient of thermal expansion;

cooling said metal base and said solder, said metal base experiencing tensile stresses and said solder experiencing compressive stresses to form a concavity in a thermal face of said base;

planing said thermal face;

wherein said tensile stresses and said compressive stresses reduce such that said thermal face is convex.

2. The method of claim 1 wherein:

said first coefficient of thermal expansion is about 17 ppm/C and said second coefficient of thermal expansion is about 15 ppm/C.

3. The method of claim 1 wherein:

said base and said fins are made from the same material.

4. The method of claim 3 wherein:

said base and said fins are copper.

5. The method of claim 1 wherein:

said base is copper and said solder is 90In-10Ag solder.

6. The method of claim 1 wherein:

said base is copper and said solder is Sn—

Bi solder.

7. The method of claim 1 further comprising:

installing fasteners around a periphery of said base for securing said base to a surface.

8. A heat sink comprising:

a metal base having a first coefficient of thermal expansion, said base having a thermal face for contacting a surface from which heat is to be conducted;

a plurality of grooves formed in said base;

a plurality of fins positioned in said grooves, said fins having said first coefficient of thermal expansion;

said fins secured to said base with solder, said solder having a second coefficient of thermal expansion lower than said first coefficient of thermal expansion so that said thermal face is convex.

9. The heat sink of claim 8 wherein:

said first coefficient of thermal expansion is about 17 ppm/C and said second coefficient of thermal expansion is about 15 ppm/C.

10. The heat sink of claim 8 wherein:

said base is copper and said solder is 90In-10Ag solder.

11. The heat sink of claim 8 wherein:

said base is copper and said solder is Sn—

Bi solder.

12. The heat sink of claim 8 wherein:

said fins are copper.

13. The heat sink of claim 8 further comprising:

fasteners around a periphery of said base for securing said base to a surface.