| Thermal fatigue of solder joints is a major reliability issue in electronic packaging. Accurate predictions of solder joint fatigue life are therefore critical to electronic designs. However, due to the nonlinear behavior of solder, analytical methods for evaluating the fatigue life can be quite complex and the results are often of unknown accuracy. In this work, a finite element analysis has been conducted to predict the plastic effective strain range of a 60/40 tin-lead solder joint during thermal cycling between 185{dollar}spcirc{dollar}F and {dollar}-49spcirc{dollar}F. The plastic behavior of the solder was modeled as a bilinear kinematic hardening material following the von Mises yield criterion and the associative Prandtl-Reuss flow rule. Time-dependent nonlinear behavior was neglected. The configuration consisted of a pinned hybrid attached to a glass polyimide printed wiring board. The plastic effective strain results were incorporated into a Coffin-Manson low cycle fatigue law to predict the solder fatigue life. The results indicate that the analytical prediction is within an order of magnitude of observed test results. It is concluded that, for the configuration and environments evaluated, the time-independent bilinear elastic-plastic analysis was a reasonable approach for predicting the solder joint fatigue life. |
