The effect of residual stress on the stress distribution of an IC solder joint

摘要

The variation of thermal stress distribution around solder joint of an IC device under a cyclic thermal load is presented in this article. The effect of residual stress produced in the solder solidification shrinkage process is considered. A model of coupled thermal-elastoplasticity is adopted to solve the stress distribution by employing the finite element packages MENTAT and MARC. The temperature dependent material properrties of the Sn63Pb37 solder, i.e., Young's modulus, thermal expansion coefficient, thermal conductivity and yield strength are modeled by curve fitting from limited available datum. Due to the preloaded residual stress distribution, the thermal stress introduced under the cyclic thermal loading may redistribute the stress around the solder joint. This stretching and compressing of the redistributed stress may result in unexpected damage to the IC joint at the highest or the lowest thermal load temperature. The residual stress produced by the solidification shrinkage is material dependent in nature, thus creating the results in only available to Sn63Pb37 solder. A parameter study based on the joint configuration has also been performed. This study revealed that the residual stress produced by the solder solidification shrinkage can not be ignored in the IC device stress analysis.