In a message dated 2/12/01 10:07:41 AM, [log in to unmask] writes:

<< What about any traces or ground planes which are not covered with

solder mask?  These locations would not get solder coated, therefore would

remain IWT.  Wouldn't there be a concern of tin whisker growth over time in

the field? >>

James, wait: Your application is going beyond the intent of the material. IWT
is not applied to the PWB as a post assembly finish. IWT, like your other
interest OSP, are designed to preserve a solderable pre-assembly finish,
nothing more. Tin whiskering becomes moot as there would be worse things
waiting for immersion and organic coatings after assembly.

The idea of using immersion coatings or OSP as a post assembly finish is, in
my opinion, a bad idea. This will be argued by people who have had OSP coated
groundplanes on backpanels in the tropics since 1975, but I won't put my
warranty on it.

Robert Lazzara

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