US Patent 7977780 Multi-layer package-on-package system

A package-on-package system includes: providing a bottom package module incorporating a bottom package substrate; attaching a central internal stacking module, incorporating a central interposer, on top of the bottom package module; placing a spacer on the top surface of the central internal stacking module; mounting a first top package module, incorporating a first top interposer with an opening, on the spacer; and enclosing at least portions of the bottom package module, the central internal stacking module, and the first top package module with an encapsulant.