I believe most mechanical switches use silver plated contacts, but
that's an entirely different surface finish than the ImAg you are
working with--its just a point that silver is OK for switch contacts.  I
know ImAg is designed as a temporary coating and is ultra-thin, so if I
were you I'd also be concerned about long term consequences.  Here's
another data point--I've recently purchased two different PC
motherboards and both appear to have ImAg board finish, as can be seen
by the support mounting holes, which didn't receive any solder.  If
that's true, than somebody must think that ImAg is not likely to cause a
problem if left exposed within the life of a PC.

Wayne Thayer

>>> [log in to unmask] 9/14/2006 1:09 am >>>
We've been using Immersion Silver instead of HASL for several years
now.

A new design has connector pins that are held to the surface of the
board
with springs, so there is no solder, just connector contacts touching
SMT
pads.

The silver pads are starting to tarnish,
but I have heard that silver oxide is conductive.

My questions are:
How Conductive?
Is there going to be resistance?
Is silver okay for switch contacts?
Does Immersion Tin corrode the same way?
Do I need to go back to HASL on this one?
(or is gold not a cost adder anymore?)
Is this too many questions?
Should I stop now?

thanks in advance?
Jack

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