Reliability assessment of a thin (flex) BGA using a polyimide tape substrate

Wireless communication customers require thinner, smaller footprint packaging to allow for reduction in phone and paging product sizes. Currently, the thin MAP (mold array process) BGA package is in production which converted from glob-top BGA to reduce the overall package profile from 1.60 to 1.30 mm. MAP BGA limitations are substrate routing on finer geometries or more dense designs and meeting overall package thickness requirement (1.1 mm max. before collapse). In addition, major issues were experienced with the manufacturing of the thin MAP BGA due to substrate warpage. The fleXBGA^TM package is a thin package that uses polyimide tape as a substrate to reduce the overall package profile to 1.1 mm. This paper reviews results from the evaluation of this new package as compared to the thin MAP BGA. This report discusses how substrate processing issues were addressed in thin MAP BGA and on the flex BGA. The critical considerations for using polyimide tape which is ⩽0.1 mm thick are solder joint reliability, moisture effects (preconditioning, vapor phase reflow, autoclave and temperature cycling), coplanarity, and warpage performance when compared to BT resin substrates. The advantages and disadvantages of using a polyimide tape substrate are included. The report discusses manufacturability and reliability issues with this package. Also included is a discussion comparing this wire-bond solution to a flip-chip version of the package. A comparison is made to when the wire-bond solution is more feasible than flip-chip. The discussion includes substrate design issues that must be addressed as compared to required BGA pin-out