Letter 2653

Removing Electroless Nickel from steel

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I am trying to remove electroless Nickel coating and Copper strike from steel without corroding steel surface. So far my results are very inconsistent: parts cleaned in the same acid vat never look the same. My acid bath is basically Hydrochloric/Sulfuric acids at 1 to 3 ratio with some surfactants and wetting agents. What am I missing in this process?

Thank you in advance,
Nina

Nina Geller

There are a number of commercial strippers for electroless nickel and copper. Both immersion strippers and electrolytic strippers will remove the coating without significantly etching the substrate. My favorite is an ammonium nitrate based solution which operates at a pH of about 6 and is quite fast, especially for EN.

Carl Steinecker
MacDermid, Inc. - Waterbury, CT

Best way to remove platings is let the platers do it. We have to de-plate and re-plate more often then we wish to remember. We send it back to the platers. They in turn use proprietary mixes to selectively attack the plating while leaving the base metal alone. Reverse plating is also another option. Proprietary plating removers are mixtures of acids, highly buffered, with selective chemicals to focus the acids on the platings and leave the parent materials alone. More than that, I cannot help, except to point you to some references. I remember several covered stripping, but it was not my focus and I took no notes:

1. The Canning Handbook

2. Electroplating 1978; American Society of Electroplaters McGraw-Hill Book Co, NY ISBN 0-07-038836-0

3. Electroplating Engineering Handbook, 4th Edition 1984: L.D. Durney.

4. Electrodeposition of Alloys, Vol 1 (Principles and Practice) 1963: A. Brenner Academic Press, NY CCN 62-13044

5. The Modern Electroplating Laboratory Manual 1965: I.C. Armet Robert Draper Ltd, Teddington, England No I.D.

University Libraries are godsends of good data. Good luck.

Lee R. Williams
transducers - Costa Mesa, CA

Please also see our FAQs on Stripping of Electroless Nickel.

Regards,

 
Ted Mooney, P.E.
Finishing.com Inc. - Brick, NJ

Dear Sirs:

I am looking for information on electroless (Ni/P, Ni/B) plating and electrolytic Ni plating. The specific application of these processes are to coat solder ball land sites of BGA semiconductor packages.

I would greatly appreciate any help in getting a better understanding differences and problems seen with these plating processes. Thanks.

Sam Yoon
Altera Corp - San Jose, CA

Dear Sir,
For Stripping electroless nickel from mild steel substrate you can try with mixture comprising 7 parts of nitric acid and 3 parts of acetic acid with /without additives. Care should be taken to check the basis metal often during the stripping process to avoid etching of basis metal.

With regards,

Karthick Duraisamy
- Bangalore, Karnataka, India

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