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Non-metallic deposit during EN plating

I have recently encountered a problem with electroless nickel plating that I am curious about. The plating problem, on printed circuit board, was noticed due to defects in a gold plating layer and solder wetting problems. Cross sections of the nickel plating show an irregular and sometimes very thick nonmetallic deposit where the nickel plating should be. The nickel always covers the copper, but in some areas up to 2/3 of the expected nickel thickness is nonmetallic. The composition of the deposit determined by EDS analysis shows mostly nickel but with much higher phosphorus than in the metallic plating.

Could this nonmetallic material be a nickel phosphite created as a byproduct of the plating reaction? Why does this occur?

Thanks for your input.

Larry Hanke
Minneapolis, Minnesota
1998

Without being able to see it, it sounds like the cleaning process is inadequate or the EN is not being properly run. The Vendor(s) need to be involved in this problem. The larger EN manufacturers labs should be able to help with this. Probably is going to require running test parts under different conditions to determine where the problem lies. A good troubleshooter should be able to do this in a few tries.

James Watts
- Navarre, Florida
1997