Please advice,
Did anybody experienced sputtering solder effect?
When the PCB passes though the  wave soldering  machine, we observe solder
splatters though the multiple vias in the board. This splatter causes solder
shorts on the top side of the PCB.
I guess ,we  may have some moisture trapped in the vias, and as it passes
through the solder wave turns to steam causing the sputter.
Our PCB design allows solder mask over the vias. Because the mask is applied
wet, is fairly viscous, and the holes are small, most of the vias are
plugged with mask.

We may be having two issues:

1) Because not all of the holes can be plugged reliably, some of them are
left partially open. Because of the partial part, the inside of the hole can
be quite rough allowing moisture to collect. Of course each hole will be
closed to a different amount.

2) Since the solder mask is polymerized with light, the areas that are to be
covered with mask (like the vias in this case) need to be exposed so that it
doesn't develop off. Because of the thickness of the solder mask in the
hole, all of the mask may not be polymerized inside of the hole, which may
not be allowing it to fully cure.

What would you advice from the deign standpoint? Any recommendations?

Sincerely,
Stella Neyman

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