Hi Dewey - for what its worth, here are some thoughts. Silver is a very 
common contact material so that's no surprise. You can solder to silver 
over BeCu but having a copper underplate would make it more solderable. 
Also keep in mind that silver and copper love each other so the 
solderability will only be a short term function. BeCu is a very common 
pin material for contact applications so also no surprise. Using a nickel 
barrier is a big question as it would improve the contact characteristics 
in terms of both wear and solderability. However, sometimes nickel causes 
functional problems with the overall circuit characteristics. As for 
soldering, use Sn63, Sn60 or Sn62 as all three would work just fine (I 
don't see leaching being an issue as long as the soldering process is 
typical). What you really need is an old pin that you can do both XRF and 
then a cross section so you can backwards engineering what the original 
plating stackup looked like. Good Luck.

Dave Hillman
Rockwell Collins 
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From:   "Whittaker, Dewey (EHCOE)" <[log in to unmask]>
To:     <[log in to unmask]>
Date:   03/28/2014 09:39 AM
Subject:        [TN] Pins and Needles
Sent by:        TechNet <[log in to unmask]>



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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