My speculative 2 cents.
Be is added to Cu to harden it, it also makes it slightly springy. BeCu is
very difficult to solder. I'm not sure but I think it also resists
tarnishing. (Google that)
Ag? Who knows -could be a protective finish which as said doesn't matter if
it oxidises. Or it could erroneously (we know now) have been thought to
improve solderability.
How do you know it is Ag though?
More likely nickel, or it could be you have Ag over Nickel. If nickel then
for soldering just need more than 4um. If this is a wear resistant pluggable
finish, much thicker and probably not an easily solderable plating grade.
Whatever... suggest you look at contemporary finish specifications for
functionality required to make a recommendation.
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE)
Sent: Friday, March 28, 2014 7:32 PM
To: [log in to unmask]
Subject: Re: [TN] Pins and Needles
Don,
I'm trying to get a pin analyzed now. I was just asking if any old or young
experts had some insight/opinion on the situation so I could argue/justify
the additional research needed to correctly address the problem.
Thanks,
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Don Vischulis
Sent: Friday, March 28, 2014 12:18 PM
To: [log in to unmask]
Subject: Re: [TN] Pins and Needles
If a sample is available som lab work to analyze the materials might be
helpful. Probably beryllium copper for the pins. Silver thickness will
affect reliability.
Don Vischulis
Sent from my iPhone
> On Mar 28, 2014, at 11:16 AM, Patrick Goodyear <[log in to unmask]>
wrote:
>
> 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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