High Temperature Storage Simulation and Strain Analysis of Solder Ball in Fan-Out Wafer Level Package (FOWLP)

More and more Fan-Out Wafer Level Package (FOWLP) are introduced to the harsh work environment such as high temperature storage. The high temperature storage reliability of packages and solder balls will face more serious challenges. In this paper, the effects of storage time, Epoxy Molding Compounds (EMC) material and EMC thickness on the high temperature storage reliability of FOWLP were investigated. The Garofaro-Arrhenius model is used as the creep constitutive model. The stress and creep strain responses of solder balls during high temperature storage were simulated. The simulation results show that as the storage time increases, the creep strain increases sharply at first and then approaches an equilibrium value slowly. The creep strain of solder ball accumulates continuously. The maximum creep strain solder ball away from the center of the printed circuit board (PCB). The weak position of solder ball is located at the interface between ubm and solder ball on the die side. With the increase of EMC thickness, the creep strain of solder ball decreases gradually. Increasing the thickness of EMC and selecting high Young's modulus EMC materials can improve the reliability of FOWLP in high temperature storage.