Other

Hewlett-packard Company

Peter F Dawson

Jacques Leibovitz

Voddarahalli K Nagesh

Greg M Irby

Hilmar W Spieth

A silicon die, such as an integrated circuit, is reworkably bonded to a copper heat spreader. The silicon-copper bond exhibits high compliance under conditions of thermal stress even though there is a significant thermal coefficient of expansion difference between silicon and copper. A compliant adhesive is applied to the surface of one of the silicon die and the copper heat spreader and is cured. Thereafter, a thermoplastic adhesive is applied to bond the silicon die to the copper heat spreader. A composite bond is thereby produced, including a highly compliant layer and a thermoplastic layer. The die may be reworked by heating the thermoplastic adhesive until the bond begins to soften and the die is released.

Reworkable die attachment to heat spreader

An integrated circuit is reworkably attached to a circuit board in a manner that forms a compliant bond which is stable under conditions of high thermal stress and thermal coefficient of expansion mismatch. A thermoplastic adhesive having a melting temperature higher than integrated circuit operating temperature is coated on the integrated circuit and dried. The adhesive is then cured. The coated integrated circuit is bonded to the circuit board with a thermosetting epoxy having a low curing temperature, such that curing the adhesive does not damage the circuit board. The integrated circuit is readily removed from the circuit board without damaging the board by heating the integrated circuit to soften the bond between the integrated circuit and the circuit board at the thermoplastic adhesive interface. An alternate embodiment of the invention provides a copper plate interface that is soldered to the circuit board, and to which an integrated circuit is permanently bonded. Reworkability is achieved by flowing the solder bond and removing the copper plate/integrated circuit assembly.

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Portola Valley, CA, United States of America

Peter F Dawson