Simulation methodology development of warpage estimation for epoxy molding compound under considerations of stress relaxation characteristics and curing conditions applied in semiconductor packaging

The thermal mismatch between different components has been a serious issue in the reliability of electronic products. The effect of epoxy molding compound (EMC) on the warpage of electronic package should be considered. The finite element method (FEM) is widely adopted to predict the warpage induced by the molding process. However, no previous studies focused on the warpage during the molding process and post process. In this study, several material characteristics of the EMC, such as cure reaction, cure shrinkage, and viscoelasticity, are measured. This study analyzes the corresponding mathematical model completely and substitutes the above properties into the FEM while the process conditions are considered through measurement. A process-oriented simulation methodology is proposed, and the estimated warpage results show that the simulation methodology with stress relaxation of EMC is in good agreement with the experimental value. The characteristics of stress relaxation behavior undergoing the molding process are discussed through the evolution of warpage. The warpage is different from the two process steps at room temperature due to the stress relaxation. This study demonstrates how the conditions of the post molding cure (PMC) process affect the warpage. The warpage can decrease with the extension of PMC time but the degree of reduction has a limit.