Hi Kc! I went to Surface Mount International last week, and had a chance to see a way to reball BGA's that is very simple, and not expensive at all. I've seen the advertisements in a few magazines, but this was the first time I've seen it live. It's from a company called Solderquik, and they were re-balling BGA's at the show. It's a pre-formed array of balls that match the pattern of the device that you're "re-emasculating" (sorry, couldn't help myself...hehe), that's held in place by a propietary high-temp, water soluble paper material that was developed by Raychem. You clean up the pads on the bottom of the BGA, brush some paste flux over the bottom, place the BGA with the pads facing up in a little aluminum carrier they supply, peel a cover tape from the preform and place it in the proper orientation for the ball pattern (this is probably the hardest part, you got a 1-in-4 chance of screwing it up with some patterns), and then reflow it! That be it! After it's cooled from reflow, take the BGA and soak it in DI water which softens the paper carrier for the balls, and peel it from the bottom. Then do a final cleaning of the device to remove all remaining residues...like have a small basket made to hold them in and run `em thru your inline cleaner...it couldn't be simpler. There's quite a few players in the BGA re-balling business who sell tools to re-ball BGA's, most all lean towards printing paste and then placing the balls in paste and reflowing. Costs for the tools rise as the difficulty to print paste and place the balls into the paste decreases. For instance, I saw a system that uses this little table-top vacuum that has a nozzle on the end of a hose which has a removable plate that has holes drilled in the same pattern as the BGA. You print paste with a teeny munchkin stencil, in a teeny munchkin printing fixture, using a teeny munchkin squeegee. The grab the hose, activate the vacuum and put the nozzle in a tray full of the balls. One ball is sucked into each hole drilled into the plate and held there, then you place the nozzle over the BGA that's held in a special fixture that comes with the system, deactivate the vacuum and the balls stay in the paste. Reflow, clean, etc.. That complete system runs $6,000...and you have to get a new stencil made and a new nozzle plate for each BGA you want to re-ball. The things I like about the Solderquik product is that as long as you give someone the correct patterned preform, it's really a "no-brainer" to reball BGA's. Clean the bottom up, slap some flux on, put the preform on, reflow, clean, done. Oh...the cost, I asked what these preforms cost, and of course it depends on the pattern, number of balls, how many you buy, yada, yada, yada,...but the average price of all the patterns they carry is around $3.00-4.00 a piece, and the little aluminum carrier is $19.00. You can use the carrier for any pattern BGA just as long as it has the same outside dimensons. Just thinking about it in my instance, I'll save at least twice that in labor costs on our production floor using these preforms to reball BGA's myself vs. any other method, and I don't think I can come close to those costs sending parts to an outside reballing shop. As far as restesting, I think you need to assume that you're reballing a good part, put it on the board and hope that it works when the board is tested. Oh I suppose you could go to the extremes of having the part retested, but I don't think most people do that. I wouldn't spend the time reballing a BGA that got it's balls ripped from a board after the board got dropped, but ones that I feel can withstand two additional reflow cycles and survive. I hope this helps, -Steve Gregory- P.S. I don't work for Solderquik, nor do I have any interest in this company...I say that because I just reread this post and it looks like an advertisement...I suppose it is...word-of-mouth.
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Hi folks,
Lately I am also having problem with BGA ball p...
- Aug 27, 1998
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