Warpage study of plastic endapsulated IC package

Abstract

This project is to study and optimize the warpage of IC packages using statistical analysis. Design of Experiment is used and experiments are carried out to identify the factors that have significant effect on the warpage of packages. The factors to be studied are chip/pad ratio, pad size, downset, transfer molding pressure, transfer molding time and molding temperature. It was found that chip/pad ratio; pad size and downset had significant effect on warpage. Smaller chip/pad ratio, bigger pad size and higher downset result in asymmetry in the structure of the package. This causes the package to warp in order to compensate for the mismatch of coefficient of thermal expansion of the materials (leadframe, mold compound and silicon chip) used in the package. Also, the effect of chemical shrinkage is more significant with asymmetry in structure of the package.