Study on the Applicability of Multi-Point Constraints for 3D WLP Finite Element Model

Solder joint fatigue is a common failure mechanism in wafer-level packaging (WLP) under thermal cycle loading. The 3D finite element method is commonly employed to assess the risk of solder fatigue. However, the number of elements required for 3D finite element simulations often exceeds hundreds of thousands, leading to time-consuming simulations. Therefore, multi-point constraints (MPC) are utilized to reduce the number of elements effectively. In this study, a 3D finite element model with MPC is created. MPC is set on the area of four solder balls with the largest distance to the neutral point (DNP). Assuming all materials except for the solder joint behave linearly, the Chaboche kinematic hardening model is applied to the solder joint. The shape of the solder joint is derived from the Surface Evolver. The 3D finite element model is subjected to thermal cycling loads, following the JESD22-A104D Condition G. Substituting increment of plastic strain energy density into Modified energy empirical equation to predict the life.