Metal finishing Q&As since 1989

-----

Sn-Pb is unintentionally plating onto molded compound

2004

Hi,

Recently, our electrolytic plating lines faced some problems of Sn-Pb(85/15) being plated onto the molded compounds. The problem is sporadic, and when it happens, it only affects a handful of strips per thousand strips plated. The solder plated onto the molded compound is usually observed to 'creep' from the plating on the metal leads beside. As we are running 2 types of plating chemistry, Sn-Pb and Pure Sn, we also observed that the issue of solder been plated onto the molded compound occurs only on Sn-Pb plating operations, and not on Pure Sn plating operations.

Some background information: Substrate material: C194 or C7025

Would like to seek some expert opinions on what could be the cause of Sn-Pb being plated onto the molded compound which is unnatural, as the compound is not conductive in the first place. Where and What type of contaminant could cause such an effect. And why does it affect predominantly only Sn-Pb plating and not Pure Sn plating?

Thanks.

Best Regards,

YL Wong

Wong Yew Leong
Semiconductor Manufacturing - Singapore

Interesting problem! The things that I would check for is to make sure your metal concentration is high and your current density is low which will give you less chance for this creepage. If you are barrel plating these parts, beware of parts nesting in the barrel and your alloy composition. A high lead content in a barrel may lead to this problem. Good luck!

Karl Weyermann
- Lebanon, Kentucky, USA
2005