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Date: | Fri, 28 Mar 2014 12:16:41 -0400 |
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Dewey,
More detail would be needed, old product name.... Was it Mil-spec?
etc. I am an old tech but don't remember seeing such an animal. The
silver plate was most likely used because silver oxide is has a high
conductivity, I think right next to copper but not as soft and the pin,
may have been copper-beryllium, since that is a common usage for some
tooling and most likely silver plated directly on. Check Keystone
Electronics to see if they have anything in their archives. Silver
over brass and bronze were very common for Mil-Spec equipment.
Pat Goodyear
Semi-retired Control Technician
On Fri, Mar 28, 2014 at 7:37 AM, Whittaker, Dewey (EHCOE) wrote:
> 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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