Summary for tin plating slivers Discussion
Tin plating slivers during stamping is discussed as a likely mechanical problem rather than something that can be fixed with a bath additive. Brian Shoemaker asked whether any plating bath additives or processes could prevent tin-plated copper alloy from scraping into slivers during forming, noting that some runs had been successful but recent ones were not. Jim Conner replied that tin is very soft and lubricious, so it can gall when pinched, and suggested the real issue may be that the copper sheet is slightly too thick for the punching tools, leaving insufficient clearance in the closed die. Years later, Sorin reported the same sliver problem on stamped material, even after inspection, because the customer still found slivers during assembly. The thread then sought clarification that the issue was indeed tin plating on copper and not a die sharpness or fit problem, reinforcing that tooling and clearance should be checked first.
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Q. We have a stamping job that requires forming .0325″ thick copper alloy with tin pre-plated material. We have run into problems with plating being scraped into slivers. Are there plating bath additives or processes that will prevent this? We have had many successful runs, but recently significant problems.
Brian Shoemaker
Stamping facility – Butler, Pennsylvania, USA
2004
A. Tin, even bright tin, is quite soft and lubricious; that is why it is used (often in conjunction with lead) as a bearing material. However, when pinched, it can sometimes gall. I wonder if your problem is that the copper sheet is slightly too thick for your punching tools and there is insufficient clearance for the sheet to fit in the closed die.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004
A. If it is a forming issue, the mating surfaces may have developed imperfections causing the scoring. Check them out with a strong magnifying glass. If it is a plating issue, the coating thickness may be out of tolerance. Depending on how tight the tolerances are, you can adjust the thickness accordingly. It’s also possible the plating bath is co-depositing impurities that are interfering with the forming process.
Jim Conner
Mabank, Texas USA
2004
Q. We have the same problem. Stamped material has slivers, and even though we check twice, our customer detects slivers during assembly.
Sorin
– Timisoara, Timis, Romania
January 18, 2013
A. Hi Sorin.
Just to be clear, you are still talking about tin plated copper, and it is the plating that is producing slivers, not a lack of sharpness/fit of the dies?
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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January 18, 2013