High Power Module Package Mounting and Temperature Cycling Reliability Study by Simulation

This paper studies the reliability of high power module package in torque mounting assembly process and temperature cycling reliability by simulation. The power module package, which with initial warpage, will be mounted on an outer heat sink with torque first and follow by in temperature cycling test. A complicated 3D non-linear finite element model was developed to simulate these two processes together. The package warpage and die stress/strain are discussed and analyzed to evaluate the die crack risk in customer's application. A warpage simulation was run firstly to get the package's initial status before torque mounting. Secondly the package with initial warpage is mounted on an outer heatsink with two screws at package two edges. Small pre-tightening torque and big final tightening torque are applied on two screws step by step. Finally, the temperature cycling loading is applied on the package together with the torque mounting loading. Silicon die stress/strain are studied to evaluate the die crack risk in customer's application. The actual measured warpage data at room temperature is correlated with the simulation results. Finally, the models with different package warpages and different final-tightening torques at screws were investigated to increase the reliability performance of this power module package.