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Controlled Gap in Semiconductor Packages

IP.com Disclosure Number: IPCOM000089081D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Doo, VY: AUTHOR [+2]

Abstract

For heat transfer control in semiconductor application, there is need for a compliant gap between a semiconductor chip unit and a cap. Such a compliant gap is desirable to avoid damage to the solder joints mounting a circuit chip to a conductor pattern (not shown) on a module substrate. For thermal considerations, such a gap should be as small as possible and have minimum variations. Normally, such variations would be the statistical summation of the tolerances on the circuit chip, the solder joints, module substrate flatness and the heat sink cap.

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Controlled Gap in Semiconductor Packages

For heat transfer control in semiconductor application, there is need for a compliant gap between a semiconductor chip unit and a cap. Such a compliant gap is desirable to avoid damage to the solder joints mounting a circuit chip to a conductor pattern (not shown) on a module substrate. For thermal considerations, such a gap should be as small as possible and have minimum variations. Normally, such variations would be the statistical summation of the tolerances on the circuit chip, the solder joints, module substrate flatness and the heat sink cap.

Heat variations can be substantially reduced by applying a compliant gap filler to either the chip extender (e.g., a silicon plate bonded to the back side of the circuit chip) or to the bottom of the top wall of a heat sink cap. A space is retained between the chip extender and the gap filler, which is bridged with a suitable material, such as conductive epoxy.

Illustratively, the gap filler can be a compliant wax which will conform with tolerance variations as the heat sink cap is secured or mounted to the module substrate. After mounting, the wax can be thermally or chemically (e.g., solvents) removed, and then replaced by another heat conductive material, or the gap can be retained in the final unit. The gap material can be uniformly applied by screening, spraying, decal transfer, and the like.

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