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March 2014

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Subject:
From:
"Whittaker, Dewey (EHCOE)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Whittaker, Dewey (EHCOE)
Date:
Fri, 28 Mar 2014 14:37:53 +0000
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Dear Technet,
For the record I'm looking for a special talent. Old, old product that has beryllium pins ultrasonically bonded in a plastic switch housing. The pin is silver plated prior to installation. The spec  and materials have been obsolete for 25-30 years. They asked me to write a new one, so my first question was why silver? Watching too many Lone Ranger episodes as a child or hooked on oxides?
One end of the pin rubs on the sliding switch plate (proprietary finish) which is probably silver. The other end
of the pin is installed in a PBA and flow soldered .
So the pin has to be conductive, solderable and let's say hard. There is  no specific information on the beryllium pin, so how do I help them without knowing how I helped them. My questions are as follows:

*         Do I apply a copper plate on the pin first

*         Do I apply  a nickel barrier layer over the copper plate

*         What nickel plating spec (ASTM B 700) do I use and what minimum thickness (200-300 micro-inches) when one end needs to be soldered

*         Should the solder in the flow solder bath be 2% Ag
I would not have designed this  is and what I want to change it may not be possible, I'm open to suggestions to try anyway. Whole new pin with one special surface finish, would be my reply.

Dewey

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