Process development and reliability evaluation for inline Package-on-Package (pop) assembly

Traditionally, most of the miniaturization for printed circuit board assemblies (PCBA) has been accomplished by stacking bare dice inside the package, reducing the pitch of the package, and/or reducing the component and pad spacing on the printed circuit board (PCB). There is a limit, however, on what can be done with regards to component pitch and spacing. Package on package stacking (PoP) offers a new alternative for further miniaturization and densification of PCBA. This paper describes the PoP process requirement, and the impact on mechanical and thermo mechanical reliability using different pad layouts and with/without underfill.