Solder Joint Geometry Effects on Thermomechanical Fatigue Lifetime of End-Capped Chip Component Assemblies

Electronic component assemblies are exposed to thermal cycles that lead to the thermomechanical fatigue of the solder joints. The effect of the joint geometry on the fatigue lifetime of the assembly is investigated for rectangular end-capped chip components in order to both increase the predictive capabilities of integrity assessment schemes and to guide toward more durable designs. A two-step approach is developed including two models considering the region of the joint underneath the component and the filet, respectively. Local values of the inelastic strain energy density are extracted from finite element (FE) simulations. Phenomenological failure power-law models are identified based on experimental data and previously developed cohesive zone model (CZM) describing the fatigue cracking process. The analysis proves that the filet and its shape play a primary role in setting the fatigue lifetime of the solder layer.