Abstract
Power modules are used for all types of electric power control and key devices for energy saving. One of the important parts
for a power module is the wire-to-semiconductor chip joint. This joint is subjected to repeated temperature cycles, and repeated
thermal stress acts on the joint due to the difference in coefficient of linear thermal expansion between a wire and a die material.
Wire-liftoff is the thermal fatigue caused by such repeated thermal stress. In recent years, power modules are expected to be used
at high temperatures of 200℃ or higher. Finite element analysis considering both creep and plastic behavior is a powerful tool for
evaluating the wire-liftoff lifetime. Stress reversal occurs in a bonding wire under a repeated thermal stress condition. It is known
that the modified strain hardening rule should be utilized in the transient creep analysis instead of the conventional strain hardening
rule. In this paper, we performed the fund amental study on the application of the modified strain hardening rule to wire-liftoff
phenomenon for an Al wire-Si die system.
