Study on the feasible mesh size control method for WLP 3D finite element modeling

Under thermal cycling loading, solder joint fatigue is a common failure mechanism for wafer-level packaging (WLP). 3D finite element method is often applied to estimate this solder fatigue risk. However, the most critical solder joint exhibits strain concentration, and careful mesh density control is critical to obtain a proper prediction value.In this research, a 3D finite element model is established, where the profile of the solder joint is obtained from the Surface Evolver. All the materials are assumed to be linear besides the solder joint, in which the Chaboche material constitutive equation is applied. The 3D finite element model undergoes cyclic thermal loading, following the JESD22-A104D condition G. Coffin-Manson empirical equation is applied to convert the equivalent inelastic strain to the predicted cycles.