A General Methodology to Predict Fatigue Life in Lead-Free Solder Alloy Interconnects

The ubiquitous eutectic tin-lead (Sn-Pb) solder alloys are soon to be replaced with lead-free alternatives. In light of this transition, new computational tools for predicting the fatigue life of lead-free solders are required. A fatigue life prediction methodology was developed, based on stress-strain, creep, and isothermal fatigue data; the latter generated using a double lap-shear (DLS) test assembly. The proposed fatigue life prediction methodology builds on current practices in fatigue prediction for solder alloys, particularly the concepts of unpartitioned energy methods in finite element analysis (FEA) and continuum damage mechanics. As such, the current state of these fields is briefly discussed. Next, the global and local FEA simulations of the DLS test assembly are detailed. A correlation is then made between the empirical data and the FEA simulations. A general fatigue life prediction methodology is next described in detail. Finally, this methodology is tested and verified against the empirical data.