Chlorine residue on this ENIG land caused corrosion of the underlying nickel and copper to form copper and nickel oxides on the gold surface.
Apparently the 3 – 7 micro-inches thick immersion gold layer is not always impervious to chloride migration.
Check out SEM Lab, Inc. to learn more.
SJOKER says:
Our FAB doing ENIG process with nickel plating -> sintering -> repeat 3 times and then final nickel & gold plating , I don’t know why should repeat it many times and wondering if it exist an efficient way to do only 1~2 times of plating ??
Ed Hare says:
Sorry for the delayed response. I am unfamiliar with sintering of electroless nickel during the ENIG plating process. What is the purpose of the multiple plating & sintering steps? Thanks!