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February 17, 2010

Contact Pin Corrosion Problems

We are having a problem with corrosion and oxidation buildup on tin/lead plated contact pins on circuit boards. The circuit boards are typically in the field for more than 2 years before the problems surface.

We are looking for a solution to solve the current problem as well as proactively protecting new parts. I have read of cleaners and protecting lubes.

Also is it possible to strip and then plate these pins with gold without removing the pins from the circuit board assemblies?



J. C.

Experts Comments

I guess I need more data...

What kinds of environments are the boards in during the 2 years...

Also, it was a little disconcerting that the person has "heard of cleaners, etc." does this mean that the boards are not properly cleaned and/or coated before they are used?

Also, if any residues from manufacturing (i.e. chloride salts or other residues) are on the boards, then of course corrosion will eventually occur. Once well-cleaned, the boards can be coated with any number of coatings to prevent vapors, dust etc from contaminating interconnections and contact pins.

CLEAN CLEAN CLEAN...but again, what kind of environment "in-use".

Jim Williams
Chairman
Polyonics, Inc.
Jim Willimas is a PhD Chemist in Polymers and Materials Science. He specialize in printing, cleaning, inks, and coatings used in electronics manufacturng operations. Williams has more than 30 years experience.

The cleaner that I have used are only good for removal of surface contamination and surface oxide which is chemically bonded to the surface, so to remove the oxide you will probably need some sort of mild etch type chemistry.

This presents the problem of removal after cleaning. As for the protecting oils these in my experience provide only temporary protection of the order of months rather than days or years.

I know of no such process in the assembly industry, however going out side the box and speculating, their are some jewelry products for restoring silver plate (have not seen any for gold) that may be could be painted on the offending pins.

I do not know how successful this would be, and also you would need to rinse off the residues after the plating solution after. The silver is less prone to oxidation than the gold but has other potential problems, particularly if you have residue of the plating solution.

Neil Poole
Senior Applications Chemist
Henkel Electronics
Dr. Poole is a Senior Applications Chemist in Henkel Technologies, electronics assembly materials application engineering group. He is responsible for all of Henkel's assembly products including soldering products, underfills, PCB protection materials, and thermally conductive adhesives.

Zestron does have a cleaning agent VIGON S100 to remove the oxidation from metal surfaces from copper mainly.

However the only way to find out is to test in house at Zestron technical center. We highly recommend the client contacting us separately for scheduling in-house trials to verify the performance of removability.

The problem could be solved by removing the oxidation however full time protection against oxidation is not possible, unless they coat the metal surfaces with highly resistant non-porous polymer materials like conformal coating materials.

As for corrosion, we need to get more information what type of corrosion we are referring to here. Some of the corrosion are impossible remove from the boards surface. Even if we can, there is no guarantee the assembly would operate. Our cleaning agents do not touch metallic based corrosion.

For stripping and plating, this is not our specialty unfortunately.

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Umut Tosun
Application Technology Manager
Zestron America
Mr. Tosun has published numerous technical articles. As an active member of the SMTA and IPC organizations, Mr. Tosun has presented a variety of papers and studies on topics such as "Lead-Free Cleaning" and "Climatic Reliability".
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