Hi, I have received a report form a board supplier, analysing the reuslts form non wetting problems we have been expereincing with their boards. I assumed it was due to the gold layer being too thin, thus allowing the nicklel layer to be exposed and thus not easy to solder to. However, the report suggets that the cause of the problem is in the pre heat stage of the reflow process, where the flux has not had enough time to vapourise and clean the surface for soldering??!!! This does not sit well with me as we run another suppliers boards, exactly the same board design, and we expereince no problmes with the same profile. Now the question I am asking is, wrt the cross sectional analysis, should these always have air bubbles present in the solder fillet formation? My expereince and tehcnical sessions I have been involved with suggestes up to 20% of a solder joint can have voids ( or air bubbles) without any detreimental affect on the solder fillet quality. Further to that, the air bubbles have no relation to the way the flux activity works on the PCB. The submitted report shows signs of silicon and carbon containination, and the report suggestes the flux from the solder paste is not being released out of the solder paste to clean the PCB finish.( whichh I think is a load of crap) Any assisitance or guidelines in relation to this problem would be very much appreciated.
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