We had some problems with dendritic growth under BGAs when we first incorporated them into our assembly process. We have since resolved the issue with a very tightly controlled cleaning process both during initial assembly and more critically, during rework - and let me stress this - ANY rework, no matter where it occurs on the board. The combination of flux residue, moisture, and time results in dendritic growth and test failure. The flux residue required to start the process is microscopic - literally. The residue does NOT have to be associated with BGA rework. We found that rework in any area of the board could contribute to dendrites since the cleaning process can initially deposit flux and leave it there if the cycle duration isn't long enough to reclean the area out. This requires an intrusive cleaning process. Hand cleaning or spot cleaning will not cut it. We use an aqueous cleaning process, so our flux is compatible with that. Jan Pelchat ______________________________ Reply Separator _________________________________ Subject: Re: [TN] BGA'S IN SPACE Author: Charles Barker <[log in to unmask]> at 0UTG0ING Date: 8/20/98 3:43 PM Hi Jim, I'm no BGA expert, but I would think you would tend to experience dendrite growth on anything that doesn't get cleaned properly. Some people may have equated this to BGA's since it may be harder to clean thoroughly under some of them. I would thank that if you get the cleaning down pat, the dendrite thing would go away. Good luck in your new role. ; > ) Charlie B. [log in to unmask] Jim Marsico 516-595-5879 <[log in to unmask]> on 08/20/98 03:07:00 PM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to Jim Marsico 516-595-5879 <[log in to unmask]> To: [log in to unmask] cc: (bcc: Charles Barker/US/I-O INC) Subject: [TN] BGA'S IN SPACE Dear Experts: I've been asked to investigate this concern, so here goes: When someone in my company mentioning using BGAs for a space application, one of our customers raised a concern about dendrite growth. Unfortunately, this is the only information I have. I don't know any specifics regarding the assembly or the application (or the customer, for that matter) or where or what kind of dendrites. All I know is that I'm now deemed the "company expert" on BGAs, so I got the task. Has anyone heard of a dendrite growth problem associated with BGAs? Thanks for your help. Jim Marsico AIL Systems Inc. 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