Today I received some PCBs I ordered, and they look like they are missing the gold from the ENIG process in some areas. Am I correct? What is the cause, and should I be concerned? They seem to still be conductive, but I am worried about in field failures and what I can't see, which is under the solder mask.
These gold skip-plating anomalies appear to be exposing a immersion Ni layer.
Test for high humidity temp corrosion and solderability and complain if correction required. Send back photos at least.
It may be insufficient rinsing between Cu microetch and catalyst ... or over-dip/rinsing between catalyst and EN..
just a guess or a SWAG