Die thickness impact on thermo-mechanical stress in 3D packages

In this study, Finite Element Modeling (FEM) is used to predict the stress and deformation induced by packaging and temperature hot spots for 3D-IC packages. The studied packages consist of a stack of two Si dies attached with flip chip technology to a laminate in a ball grid array (BGA) configuration. Three packages were considered in this paper: two molded packages with different epoxy mold compounds (EMCs) and one bare die package without EMC. The impact of the bottom die thickness on the stress and package deformation is investigated. The finite element simulation results indicate that thinning the bottom die will cause larger stress and more warpage induced by packaging. Moreover, temperature hot spots cause larger stress and more deformation for thinner bottom dies. Furthermore, the results show that the stress and deformation caused by processing are much higher than those induced by temperature hot spots.