Fatigue Life Predictions of SnPb Solder Ball in A Ceramic PoP Device

In this study the fatigue life of the critical SnPb solder ball of a ceramic package-on-package (PoP) device containing two layers of SnPb solder balls was predicted via a suitable fatigue model based on nonlinear finite element analysis (FEA). The viscoplastic constitutive relationship was applied for SnPb solder and the other materials have linear elastic behaviors in FEA. The evolution of the stress in the solder balls under thermal-cycle loadings (−55°C to 125°C) was simulated by ABAQUS. Using the stress analysis results, we predicted the fatigue life of the ceramic PoP device by the empirical Darveaux-based lifetime model. The fatigue life of the critical solder ball in the top layer is over 5 folds than that of the critical solder ball in the bottom layer. The computation results illustrated that the creep energy density plays an important role in fatigue life. The analysis showed that the critical solder ball in PoP may not suffer serious fatigue problems under thermal cycling loads comparing with the 2D packaging case that removed the top component.