FVM based Simulation on Multi-Stack Ball Grid Array (BGA)

In the conventional undertill (CTIF) encapsulation process, there are few drawbacks encountered such as extended tilling time, incomplete-filling and voids formation. Finite volume method (FVM) simulations have been conducted to study different CUT dispensing method for different types of ball grid array (BGA) orientations in a single layered PCB. It is investigated that the most ideal combination of orientations and dispensirtg type is middle empty orientation with L-type flow achieving relatively fast tilling time. The findings show that the arrangement of BOA sizes with the small solder balls placed at the bottom layer, followed by the medium size solder balls in the middle stack and the largest solder balls at the top layer has been shown to enhance the flow rate of the encapsulant.This study also reveals the potential of air gaps in improving velocity and pressure distribution near inlet and outlet to achieve faster total filling time in all layers of BGA.