SMT solder paste storage and stencil setup lessons

Solder paste problems used to show up for us as small print defects that people wanted to fix at the placement or reflow stage. Most of the time the trouble started earlier. A jar was pulled from the fridge late, opened too soon, or left on the printer long enough that the first good board after lunch was not the same as the first board at 8 a.m. The routine that worked was simple but strict…