Warpage variations of Si/solder/OFHC-Cu layered plates subjected to cyclic thermal loading

Warpage variations of Si/solder/OFHC-Cu layered plates under cyclic thermal loading were investigated as a fundamental subject for inverter power modules. Two different solders, fully annealed and as-received OFHC-Cu plates, and three thickness ratios of the Si and Cu layers were used for the layered plates tested. It was experimentally observed that the initial warpage induced by soldering either grew or recovered with an increase in the number of temperature cycles: the cyclic growth of warpage occurred when the OFHC-Cu layer was fully annealed before soldering and was relatively thick. By performing 3D finite element analysis using available material data, it was then shown that the observed cyclic growth/recovery of warpage can be simulated well if an appropriate constitutive model is employed for the cyclic plastic behavior of OFHC-Cu plates. (C) 2011 Elsevier Ltd. All rights reserved.