Does this mean I have to be nice to Doug?
Dewey, one would hope this is always the case...........
Doug Pauls
From: "Whittaker, Dewey (EHCOE)" <[log in to unmask]>
To: <[log in to unmask]>
Date: 04/01/2014 10:35 AM
Subject: Re: [TN] Pins and Needles
Sent by: TechNet <[log in to unmask]>
Dave,
Thank you for the reply. As usual an excellent reply. In this application,
the impact of nickel would a non-issue, but I will forgo it and specify
the copper. If this was a PB I would have no problem, but I'm speculating
on a copper plating spec and thickness. I'm hoping my cross-section of the
pin will give me a target. The silver finish will be per ASTM B 700 with
minimum thickness of 200-300 micro-inches (more for the durability end
then a soldering concern). It's good to hear that standard solder and
soldering process is acceptable. I wouldn't feel comfortable trying to
specify what and how to solder.
Does this mean I have to be nice to Doug?
Dewey
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, March 28, 2014 2:40 PM
To: TechNet E-Mail Forum; Whittaker, Dewey (EHCOE)
Subject: Re: [TN] Pins and Needles
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
[log in to unmask]<mailto:[log in to unmask]>
From: "Whittaker, Dewey (EHCOE)" <[log in to unmask]<
mailto:[log in to unmask]>>
To: <[log in to unmask]<mailto:[log in to unmask]>>
Date: 03/28/2014 09:39 AM
Subject: [TN] Pins and Needles
Sent by: TechNet <[log in to unmask]<mailto:[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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