We have a small PCB that has been manufactured and assembled several thousand times. However, the last lot showed inconsistencies with the solder mask:
It looks like the solder mask is very thin, almost exposing the copper. The expected color would be what you see next to the SOT23 pads.
We contacted the PCB manufacturer about this, who claims that it is most likely an issue from too high soldering temperature or too long solder duration.
So we contacted the assembly company, but they say that the soldering process did not change from the previous runs and it must be a problem with the PCB manufacturing process.
- Did anyone experience this kind of issue and what is the likeliest cause?
- How critical is this? I can't quantify if I am looking at slightly less solder mask or nearly no solder mask at all.