We use a washer soluable solder flux for our solder wave. We then wash the boards in a dishwasher. We have done it this way for years without problems. We just got a new dishwasher and now we get residue on the solder (white marks) Anyone know of what causes this ?
The waste water is filtered then sent to city sewer. When we first started we had inspections and then they said our volume was so low and did not require continued testing. We wash 20-40 boards a month. Small 3x4 inch boards. If we hand rinse the boards with DI water with this help to reduce contaminates ?
We use compressed air to dry boards
We used this same methode for years without problems. Do you think its just a cheap dishwaser or could water temp be an issue ?
We dont do enough volume to make the investment in a DI washer.
We'd guess that your white residue on the solder is from minerals in the supply water. We expect the levels of these minerals that you see: * Vary depending on the season. Check with your public water authority for anaylsis. [Recognize that this maybe risky, because they may not be aware of your processes. If they were, they may not happy with you returning lead, flux residues, and other schmutz from your wave process to them.] * Percipitated differently between washers, depending on the water preheat process.
Our filter removes all contaminates authou it takes forever to evaporate 20 gallons it work quite well. I will check with local water supply for mineral analysis. Will a water softener remove the minerals that may be causing the problem ?
Never use a water softener for defluxing. They add sodium to the water which is bad for boards. The white residue may be flux. If that's the case, either the dishwasher is not powerful enough or the wash water is not hot enough. Another possibility is that you are not subjecting the board to enough rinse cycles. Dishwashers are for dishes, not circuit assemblies so there is a lack of rinse cycles.
DI water is you best bet. Rent (don't buy) a system from US Filter. Average rental price is between $ 50.00 - $ 100.00 per month (plus exchange fees).
You should also check the quality of your compressed air. If the proper filters and desiccants are not in place, you could be recontaminating your washed boards with condensed water and oil residues from the compressed air used for drying.
I had a similar problem a long time ago. I eventually traced the problem to undercured solder resist. The flux was reacting with what was left of the uncured resist, leaving a white residue. We could not even hand scrub this off. The solution was to soak the board for ten minutes in the flux, completely submerged, then re-wash. Undercured solder resist is not unusual. Board shop employees run the resist with the lowest amount of catalyst (sometimes too low) to increase their pot life, and reduce material changeout.
Sounds like the white stuff is flux. I doubt if 4 pcb mfgers could be undercuring all at once. Good point though.
Since you changed washers and now have the problem - it's your new washer. Can you bring back the old one to make sure? if not, double check to see if the old one refreshed it's water between cycles. Could be your new one is just recircing your water and not refreshing the water as much as the old one. Times of each cycle are another area to double check. Could be your rinse cycle if very short compared to the old one. Just a thought.