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Integrated Circuit Chips Directly Mounted on Organic Printed Circuit Cards

IP.com Disclosure Number: IPCOM000043499D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Hermann, K: AUTHOR

Abstract

The cost of electronic circuitry can be reduced by mounting integrated circuit chips and discrete components, such as resistors and capacitors, directly on a planar printed circuit card or board. A major problem with directly attaching a chip to a copper land area on an organic circuit board is the significant difference in the thermal expansion coefficients between the copper and the silicon. The heat generated by the chip may ultimately fracture either the silicon-to-copper bond or the chip itself due to this expansion differential. This invention involves a method of making this direct chip attachment whereby the coefficients of expansion have no effect on either the bond or the structural integrity of the chip.

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Integrated Circuit Chips Directly Mounted on Organic Printed Circuit Cards

The cost of electronic circuitry can be reduced by mounting integrated circuit chips and discrete components, such as resistors and capacitors, directly on a planar printed circuit card or board. A major problem with directly attaching a chip to a copper land area on an organic circuit board is the significant difference in the thermal expansion coefficients between the copper and the silicon. The heat generated by the chip may ultimately fracture either the silicon-to-copper bond or the chip itself due to this expansion differential. This invention involves a method of making this direct chip attachment whereby the coefficients of expansion have no effect on either the bond or the structural integrity of the chip. The integrated circuit chip (A) is mounted on a copper alloy or other suitable metal carrier (B) with a dimple (C) protruding from one surface. Radial slots (D) extend to the perimeter of the carrier to relieve the stresses initiated by the dimple and to allow the resulting appropriate number of fingers to independently contact the surface of the ship with a slight spring pressure. This contact between the chip and the carrier will be used to draw heat away from the chip. The backside of the circuit chip (A) is attached to the carrier with a drop of epoxy or other suitable adhesive
(E) placed in the dimple (C). It is important to note that the chip is attached to the carrier only by the small spot in the center of the chip, with the balance of the chip surface contacting the carrier by the spring pressure of the fingers. This allows the major portion of the chip surface and carrier surface to move independently of each other ba...