Method of fabricating a reworkable module
Disclosed is a reworkable circuit .package formed by controlled collapse chip connection ("C4") bonding of integrated circuit chips to circuit cards and boards, and direct chip attachment ("DCA") where an encapsulant is disposed under the chip. The encapsulant offers protection of the C4 connections and a thermal expansion matched to that of the C4 joints. However, most encapsulants interfere with reworkability. The disclosed circuit package overcomes this problem by the provision of a passivating layer of Parylene is reworkable, dry processable, uniformly depositable by vapor phase deposition, forming thin films on facing surfaces at the 3-5 micron film thickness corresponding to the C4 lift-off distance.
International Business Machines Corporation
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Kurt R. Jack M. Darbha Ho-Ming
Grebe McCreary Suryanarayana Tong