You have a very bad situation. It�s tough for the gas, flux material, er whatever to escape when the BGA is sitting on top of it and the blind via is blocking it from the other side. Obviously the vias should have been: * Placed on the edge of the pad and not near the center of the pad. * Plugged and plated over.
Since they weren�t, someone has to pay and apparently THAT someone is you.
It�s interesting that this board is HASL, given the high density design of the board that necessitated via in pad.
It�s tough to get real optimistic about this situation. Ordinarily, the approaches to reach a half-way tenable situation are: * Playing with your reflow profile [ie, reduce peak; soak will not help, providing it�s over 150 seconds; etc]. * Selecting a less voiding solder paste [ie, larger paste-powder sizes, decreased paste solvent volatility, lower paste metal content, etc]. * Using other good stuff on voiding talked about in the fine SMTnet Archives.
� but given this board is HASL, try fluxing and reflowing the bare boards to fill the via with solder. Then print, place, reflow, as in good practice �
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