RELIABILITY ASSESSMENT OF A THIN (FLEX) BGA USING A POLYIMIDE TAPE SUBSTRATE
Author: Trent Thompson Company: Motorola Semiconductor Product Date Published: 9/12/1999
Abstract: Wireless communication customers require thinner, smaller footprint packaging to allow for reductions in phone and paging product sizes. Currently, the thin MAP (Mold Array Process) BGA (Ball Grid Array) package is in production which converted from glob-top BGA to reduce the overall package profile from 1.60 to 1.30 mm. The limitations of the MAP BGA is substrate routing on finer geometries or more dense designs and meeting the overall package thickness requirement (1.10 mm max. before collapse). In addition, major issues were experienced with the manufacturing of the thin MAP BGA package due to substrate warpage. The fleXBGA package is a thin package that uses polyimide tape as a substrate to reduce the overall package profile to 1.10 mm. This paper will review results received from the evaluation of this new package as compared to the thin MAP BGA currently in production. This report discusses how the substrate processing issues were addressed in thin MAP BGA and on the flex BGA. The critical considerations for using the polyimide tape which is 0.10 mm thick or less 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. This report will discuss manufacturability and reliability issues with using this package solution. Also included is a discussion comparing this wire-bond solution to a flip-chip version of the package. A comparison will be made to when the wire-bond solution is more feasible than flip-chip. The discussion will include substrate design issues that need to get addressed as compared to required pin-out on the ball grid array package.