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How to clean oxidized printed circuit boards

Some of my boards (they normally use batteries) shows traces of copper oxide.
How may I clean it, without damage to the printed circuit?

Luis Carlos Caruso
I'm an electronic designer - Porto Alegre, RS, Brazil
2005

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2005

What has worked for me in the past is:
1) Soak in hot acid clean solution for 5 min. @125 F
2) Cascade rinse
3) Soak in a 10% solution of sulfuric acid for 2 min.
4) DI water rinse
5) Hot air dry immediately
If you don't have any of these chemicals in house you could try 50% white distilled vinegar [in bulk on eBay or Amazon] in DI water with a tablespoon of salt. You may have to use fine 00 steel wool [on eBay or Amazon] if the boards are heavily oxidized, rubbing in the direction of the circuits. Be sure to rinse and dry right away.

Mark Baker
process engineer - Malone, New York

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Hi Luis ,
you will find a less aggressive etch is to use either Ammonium persulphate at 50 -100 grams / litre or a similar strength of a DuPont product called OXONE which contains no ammonia [on eBay or Amazon] . Both a safer to handle than Sulfuric acid . and provide a softer etch
regards,

John Tenison - Woods
- Victoria Australia
2005

Safe and good solution is ammonium citrate,5% pH 9.Take 1 lit water,50 gm citric acid [on eBay or Amazon] ,add some ammonia,until pH is 9 ). Good luck and hope it helps!

Goran Budija
- Cerovski vrh Croatia
2005