A novel four layers package-on-package stacking technique

Currently, the multilayer Package-on-Package (PoP) stacking technique as the mainstream 3D vertical packaging solution is extensively applied in the manufacture process of portable electronic instruments. While the warpages on the packages caused by the mismatch of the Coefficient of Thermal Expansion (CTE) and stiffness during the assembly and stacking processes are seriously threaten to the stability and reliability. In this paper, a novel four layers PoP stacking technique in which the number of memory die packaged are increased to twice of the traditional two layers PoP is presented. The metal cylinders with stable CTE are placed between the neighboring layers to reduce the warpages on the packages. The high memory density and excellent reliability could meet the requirements of the miniaturization and lightening of the portable instruments.