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Bending of Flex Leads During Thermal Cycling

Published online by Cambridge University Press:  15 February 2011

L. T. Shi  and
H. Tong
L. T. Shi
Affiliation:
IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
H. Tong
Affiliation:
IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
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Abstract

A three dimensional finite-element stress model was used to simulate the lead bending incurred during thermal cycling of a Flex connector joined to a silicon carrier via an eutectic solder. Three different coating conditions (no coating, with a polyimide coating, and with a silicone coating) were simulated. With the polyimide coating, lead bending was found to occur at the corner inner leads of the Flex as a result of the plastic strains accumulated there during thermal cycling. In the case of silicone, the corresponding plastic strains grew during the first thermal cycle but saturated subsequently, confirming the negligible lead bending observed experimentally. For the case of no coating, the highest plastic strain was found to be borne in part by the polyimide film at its edge and thus no significant bending was observed. In all cases, the results provided by the model agree well with the experimental observations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 323: Symposium J – Electronic Packaging Materials Science VII , 1993 , 33
Copyright
Copyright © Materials Research Society 1994

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