Browse Prior Art Database

Chip Heat Transfer Structure

IP.com Disclosure Number: IPCOM000049570D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 84K

Publishing Venue

IBM

Related People

Hassan, JK: AUTHOR [+3]

Abstract

The illustrated structures provide a conformable heat transfer structure utilizing a low melting point bismuth alloy solder in combination with an elastomeric material with embedded wires to conduct heat from a chip to a heat sink, and to confine the plastic flow of the solder.

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Chip Heat Transfer Structure

The illustrated structures provide a conformable heat transfer structure utilizing a low melting point bismuth alloy solder in combination with an elastomeric material with embedded wires to conduct heat from a chip to a heat sink, and to confine the plastic flow of the solder.

Effective heat transfer from a chip to the ultimate heat sink requires intimate contact between successive members in the heat conducting path. Because of surface irregularities in the mating members and differences in their respective coefficients of expansion as well as the fragility of the chip, which precludes excessive pressure, effective heat transfer across the interface requires the use of a conformable material having a high thermal conductivity at the interface. Additionally, the interface material must have suitable plastic flow characteristics such that it will conform to the mating surfaces while retaining its basic shape so as not to flow out of the interface region.

By selection of the appropriate alloy of a low melting point bismuth solder having a solidus-liquidus temperature range of, for example, 86 degrees C to 100 degrees C, the solder residing at some temperature within this range will, through plastic flow, provide the necessary conformable interface to the chip. Additionally, by casting the solder in a shape complementary to both the chip and the so-called "hat" heatsink, the plastic flow of the solder will provide a self- healing conformable heat transfer medium between the chip and the heat sink. To restrain the plastic flow of the solder, an elastomeric material having operating temperatures of -55 degrees C to +200 degrees C is utilized as a gasket. This gasket material is further provided with convoluted wires arrayed generally perpendicular to the surfaces of the material at a density in the range of 100-150 wires per square centimeter to enhance the resilience and to some extent the thermal conductivity of the material.

The foregoing principles are embodied in the following structures. Fig. 1 illustrates one structured embodiment wherein the chip 10, supported on substrate 11, is overlaid with the stepped washer 12 of copper or aluminum and the low melting point solder cylindrical plug 13. The plug 13 fits within the cylindrical cav...