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Low Melt Bond Between Piston and Module in an Air Cooled Conduction Module

IP.com Disclosure Number: IPCOM000045171D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 90K

Publishing Venue

IBM

Related People

Greenspan, SB: AUTHOR [+2]

Abstract

Structures are described for achieving a low cost solution for a heat sink module making use of IBM Controlled Collapse Chip Connection (C-4) format chip technology where it is required that heat be removed from the back of a chip. These structures are related to those described in the U.S. Patent 4,246,597. The structures set forth in the patent include a movable piston located within an air-cooled chamber wherein the piston is pressed against a chip in a C-4 configuration and associated substrate for the purpose of dissipating heat from the chip during operation.

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Low Melt Bond Between Piston and Module in an Air Cooled Conduction Module

Structures are described for achieving a low cost solution for a heat sink module making use of IBM Controlled Collapse Chip Connection (C-4) format chip technology where it is required that heat be removed from the back of a chip. These structures are related to those described in the U.S. Patent 4,246,597. The structures set forth in the patent include a movable piston located within an air-cooled chamber wherein the piston is pressed against a chip in a C-4 configuration and associated substrate for the purpose of dissipating heat from the chip during operation.

More specifically in the patented structures, there are two characteristics of interest, namely, (1) impact of the piston on the chip under vibration and shock conditions, and (2) the annulus gap between the piston and the module and resultant thermal resistance. Here, a low melt metal to metal bond is established between the piston and the module, which resolves both of these characteristics.

Chip 1 is mounted via C-4 bonds 2 to a substrate 3. The air-cooled conduction module 4 has a piston 5 in its cylindrical hole. Spring 6 exerts a predetermined force on the chip via the piston. Annulus 7 is formed by the module hole and the piston. A "low melt washer" 8 is introduced on the piston while assembling the module.

Step 1/Initial Phase The low melt washer 8 is introduced on the piston as shown in Figs. 1 and 2. The substrate 3 is then placed on the module, piston, washer and spring assembly. A thin layer of grease 12 is applied between chip 1 and piston 5. The module is then crimped, and sealant applied.

Step 2/Final Assembly The assembled module is allowed to pass (with pins downward) through the oven at a predetermined temperature (higher than sealant and lower than the C-4 joint melt point). While the module is going through the oven, the low melt washer melts and fills the annulus 7 due to capillary action.

Once the module is out of the oven, the molten slug solidifies, forming a solid...