Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


James Michaud

#14366

Ball Grid Array (BGA) | 10 September, 1998

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

reply »

Dave F

#14369

Re: Ball Grid Array (BGA) | 10 September, 1998

| 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 James: You're correct that BGAs offer great benefits through providing for increased circuit density, while not proportionally increasing manufacturing complexity, compared to QFPs. Solder joint inspection and rework are two areas where complexity increases, compared to other SMT packages. The other points you make are also well considered. Other issues you might consider are: 1 Voiding in solder balls. 2 Solder mask defined versus non-solder mask defined pads. NSMD pads are preferred on both the board and the BGA component. These and other issues have been highlighted in the SMTnet and Technet archives. Trade and professional journals, such as "SMT Magazine," "Circuits Assembly," "SMTA Journal," and "EP&P" have published innumerable articles on BGAs over the past five years. Good luck in your search. Dave F

reply »

Rick Thompson

#14368

Re: Ball Grid Array (BGA) | 11 September, 1998

| 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 James, Motorola has a 28 page .pdf document that deals with BGA's from design through inspection & some reliability and test data. You can download it at the link below.

reply »

Earl Moon

#14367

Re: Ball Grid Array (BGA) | 11 September, 1998

| 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

reply »

PCB Soldering Tools

bga rework stations