Effects on ENIG PCB surfaces due to corrosion of the nickel layer when depositing the gold in the gold bath. In the as-delivered condition of the PCBs, this is often not visible until soldering, when these surfaces show very poor or no wetting. If solder joints nevertheless form, their adhesion is very low and the solder joints separate from the pad already under low stress. A dark grey to black-bluish surface becomes visible, which gives the effect its name.

Overview