Defect of the Month
Avoid Green Solderable Finishes
A look at solder mask contamination on pads.
This month we look at solder mask contamination on pads. FIGURE 1 is a very, very bad example that never should have made it to the customer. Solder mask residues are visible on the surface and around the edge of the pad. There is also a level of solder mask undercutting.
This would not be acceptable per any standard and would have shown complete nonwetting during soldering. This would have led to a bad day in the office for the assembly engineer or, more important, the shop floor staff.

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Solder mask residues
Figure 1. Solder mask residues.
Bob Willis Caricature
Bob Willis
is a process engineering consultant; His column appears monthly.