Parametric study of warpage in Package-on-Package manufacturing

In package-on-package (PoP) manufacturing, warpages on both top and bottom packages are concerned. Excess warpage causes solder joint opening, and results in the electrical connection failure of the assembled module. Many parameters of materials, geometry, and process contribute to the warpage of the package. The objective of this paper is to investigate effects of these parameters on the warpage. The dimensions of dies, package and substrate, materials of molding compound and substrates are investigated by the finite element method (FEM) in the processes of molding and reflow. After running simulation, analysis of variance is employed to identify the influential parameters. The results show that the coefficient of thermal expansion (CTE) of molding compound and substrate as well as die sizes have significant influence on the warpage. Based on this study, the influential parameters can be optimized within practical range to achieve the lowest warpage value.