Effects of Multi-stack Ball Grid Array on Multi-stack Printed Circuit Board

Abstract

In the customary underfill (CUF) epitome process, there are couple of downsides experienced for instance, extended filling time, divided filling and voids improvement. Test and FVM reenactments have been directed to examine CUF dispensing systems for different types of ball grid array (BGA) tendencies out of a solitary layered PCB. In this task, the principle point is to enhance the stream of under filling mold crosswise over multi-stacks BGA. Package on Package (PoP), a strategy for coordinated circuit bundling, is utilized to consolidate BGA bundles vertically to permit higher segment thickness in devices. The L-type liquid stream in multi-stack BGA with edge introduction is contemplated and parameters of CUP exemplification, for example, void development and filling time were examined. The results demonstrated that the BGA sizes with the little weld balls put at the base layer, trailed by the medium size bind balls in the center stack and the biggest patch balls at the top layer has appeared to enhance the stream rate of the encapsulant ideally. Other arrangement in which the medium size solders placed are at the base layer, small solders at the center layer and largest solders on top of it, requires longest total filling time. The result also shows that the racing effect is present at central region and at the side of the layer. Because of the perimeter orientation design, the void formation is minimal and the race effect is not affecting much according experimental and computational result. This investigation additionally uncovers the capability of air gaps in improving velocity and pressure distribution near inlet and outlet to achieve faster total filling time at all layers of the BGA.