Metal finishing Q&As since 1989

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Nickel Contamination in Methanesulfonic Tin Baths

Hello folks,

I am working in the electronics industry, specifically with multilayer ceramic capacitors. We plate nickel and tin onto silver termination. My main problem is that my methanesulfonic tin baths get nickel metal contamination to a 1000 ppm levels, which it is not acceptable. I have been dummy plating at low current densities to reduce the nickel level, but I plate out at the same time the tin from the bath. Is there anything else to reduce or eliminate the nickel from the tin baths besides: electrolytic removal(dummy plating), adding more DI-Water rinses in the line or making new baths?

Thanks.

Reynaldo Arroyo
-Valencia, CA, U.S.A.
2001

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2001

Reynaldo, I think you have two problems, one is that you have a Sn bath that is contaminated above acceptable Ni contamination levels, and the other is that Ni is getting into your Sn bath. For reducing the Ni, dummy plating and/or diluting are probably your two options. However, I would be focusing on prevention.

• You should be able to prevent Ni from entering your Sn bath via rinsing and should focus on this area. What is your rinse scheme?
• How do you maintain clean rinse water?
• Conductivity, pH?
• Is it counter-flowing?
• Do you have a sacrificial Sn bath between rinsing and Sn plating?
• Do you have adequate drip times set up between each process step?

You did not mention if you are barrel plating or using RFT's. If it's barrel plating I can assure you that with adequate rinsing, drip times and a Sn predip you will not see the Ni contamination increase in your Sn bath. If you are using RFT's there are other issues that we need to discuss.

Rich Reifenheiser
- Monterrey, Nuevo Leon, Mexico