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March 2014

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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 20:30:46 +0000
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Mike,

Excellent reply, except I thought I was listening to a reply of my own speculative thoughts when I first conceptually addressed the issue. They shouldn't have been able to get there from here as first designed/built. Opposite ends of the spectrum on both sides of the issue at final assembly process.

So basically I told them that and they do can't do it right. This leaves me with the following (not due to logic, but simple functionality):

*         Start with a beryllium pin

*         Plate it with what (material) per what (spec)

*         Final finish to be what (material) per what (spec)

*         Acceptance quality is solderability and low resistance conductivity not susceptible to abrasion

*         Current acceptable final finish is Silver applied per QQ-S-365 to a minimum thickness of 0.0005 inches over a minimum 0.0005 inches of a

non-defined copper plate

Vinyl fact- This effort is bass-ackwards so pins and needles is needles and pins that I wanted to go on record (obvious) to be looking (The Searchers had a hit with this)  for talent (it made the charts).

Thanks Mike,

Dewey







-----Original Message-----
From: Mike Fenner [mailto:[log in to unmask]]
Sent: Friday, March 28, 2014 12:55 PM
To: 'TechNet E-Mail Forum'; Whittaker, Dewey (EHCOE)
Subject: RE: [TN] Pins and Needles



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]<mailto:[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]<mailto:[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]<mailto:[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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