Influence of heat sink mounting procedure on package reliability

In this paper, a general finite element analysis (FEA) software ANSYSreg is employed to investigate the influence of heat sink mount process on the package reliability. Different leadframe design and leadframe material options for a power packages are provided for modeling optimization. In simulation, the dynamic procedure of heat sink mounting process is simplified as a qusi static problem. A half package model is built due to its symmetrical structure. In addition, the advanced simulation techniques including both contact analysis and pretension method are introduced to simulate the mounting process. Maximum torque within recommended torque range is applied on different package designs for optimization of the mounting process. Meanwhile possible problems with die cracking and EMC can be predicted. In order to verify the results, actual heat sink mounting process is performed with both previous package design and the optimized package design. Comparison between both designs prove that the optimized package designed by simulation is more robust and reliable.