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Other indices for solder plating apart from Thickness and Composition

Hi,

I'm doing tin/lead plating on copper leadframe process for an IC packaging firm. The plating thickness is aroung 500um. I've been complained by the trim/form process frequently that succeeds me for unstable plating performance. The major complain is that the plating is too soft/loose and plating scratch is severe. However, measures of plating thickness and composition cannot reveal any abnormalities.

Can anyone advise what other indices or measures can be taken so that I can establish a criteria for "soft/loose" plating?

Many thanks for your info in advance.

Donna Poon
- Hong Kong
2000

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The one thing I can think of is a Hull Cell, and the two things I would look for is excessive treeing and poor or de-wetting reflow, or reflow at excessively high temperature. I would try to replicate the preplate process as closely as possible (grab solutions from the plating line).

The other possibility to investigate is organic or inorganic contamination of the plating bath, and the Hull Cell will show this.

James Totter, CEF
- Tallahassee, Florida
2000