Mechanism of Warpage Increase Behavior Induced by Thermal Cycling in Semiconductor Package

Abstract

Copper has been used for high power semiconductor package to satisfy thermal radiation performance. However, copper easily deforms and warpage increases during thermal cycle. In this research, warpage increase mechanism of copper package during thermal cycle is clarified using experiment and finite element analysis (FEA). As a result, this phenomenon occurs as a interaction with plastic deformation of copper at low temperature and a stress relaxation due to solder creep at high temperature. Therefore, warpage increases with minimum temperature of thermal cycle increase or maximum temperature decrease. Minimum temperature conditions affect plastic deformation of copper and maximum temperature conditions affect solder creep. In addition, we found this phenomenon is sensitively controlled by the temperature condition. And the results of elasto-plastic FEA that includes plasticity of copper and solder creep deformation agree well with the experimental result under various thermal cycle conditions.