Effects of solder constitutive models and FE models on fatigue life of dual-row QFN package

In this study, the board level solder joint reliability analysis and fatigue life prediction of dual-row QFN package are carried out. The effects of solder constitutive model and finite element (FE) model on solder fatigue life are studied. Three different constitutive models of SnAgCu lead-free solder including viscoplastic Anand model, steady-state creep hyperbolic sine model and double power law model are implemented. In addition, three FE models including full 3D-Quarter model, 3D-Quarter/Octant model with constraint equation (CE) technique are used. The volume-averaged method is used for accumulated inelastic strain energy density calculation. Zhu´s energy based fatigue model for QFN package is taken to predict fatigue life. The FE modeling results show that the critical solder joint is at the package corner and crack is likely to occur along lead and solder interface. The maximum accumulated inelastic strain energy are located at top layer elements of critical solder joint for all solder constitutive models and FE models. The predicted fatigue life of dual-row QFN package calculated from Anand model is slightly higher than that from the other two models. The predicted fatigue life obtained from different FE models have almost the same value, which indicating FE model with the CE technique can well be applied for fatigue life prediction.