| I'm very familiar with the great board space savings of BGA and all the "claims to fame." However, can someone out there tell me if any concern exist in the inspection realm. Additionally, solder cracking, CTE/TCE mismatches, no leads for stress relief, package internal construction, thermal concerns with the smaller package .... in short, reliability concerns are of interest to me ... and quite possibly other Product Assurance Engineers out there. | What's the scoop on BGAs and MiniBGAs, FBGAs, et cetera??? James
TCE mismatches are not an issue with plastic devices as the mounting surfaces for boards and devices move about the same ppm/C.. The same can be true for some ceramic types provided balls are attached to a "compliant" interface within the package. However, older designs had problems using this interface as it was a polyimide film bonded with an acrylic adhesive. This has mostly been overcome. Motorola provided concerns about using electroless gold over electroless nickel. I've gone into this before so you had best contact them and observe industry postings as this issue heats up. Concerning inspection, the best sample level type is X-Ray and you don't need to buy $200,000 worth of the stuff with independent non destructive test labs on every corner. High resolution black and white processes work best and very clearly show any excessive voiding. On that subject, IPC is working diligently to develop acceptability criteria for voiding ammounts. I require, for all solder joints, no more than 20% voiding preferrably not in one big lump. This is based on cycles to failure testing done on many solder joint types. And on it goes. Earl Moon
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I'm very familiar with the great board space savings of BG...
- Sep 10, 1998
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