I was looking at the gerbers as I was zipping them up to place an order. I noticed that my cad software puts paste on both sides of the board on all the through hole via’s. What is the reason for that, and is it absolutely necessary to do it? Thanks…
In general, you don’t paste vias. If you plan to reflow, you should only have solder mask on one side (or neither), not both. Otherwise, the expanding air in the via would blow off the solder mask, and a floating piece of mask could end up somewhere bad.
/mike