Immersion White Tin

Repeated thermal excursions cause a growth of the intermetalic layer. If your
PWB fabricator increases the tin thickness, the intermetalic effect on
solderability diminishes.

Although the immersion process is self-limiting it can be biased to the
"high" or thicker side by increased bath concentration, dwell and/or
temperature. A reliable reference on these parameters (in the US) is Florida
CirTek (Greely, CO).

Also, make sure your PWB fabricator is applying the white tin at the end of
the process. If the tin is applied BEFORE silk screen cure, the cure process
can artificially cause a dry-age acceleration, promoting intermetalic growth
before you even get the product.

Cheers -

Bob Lazzara
Marketing & Tech Support
Circuit Connect, Inc.
+1 706.245.4232

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