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May 2004

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Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 12 May 2004 12:17:35 -0700
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Tom,

One other thought.
If this "exposed copper" is the base metal of the wire then there is
something seriously wrong with the stripping process!

David A. Douthit
Manager
LoCan LLC

Tom Gervascio wrote:

>We have an application where we think we are forming galvanic corrosion between silver plated wire and exposed copper (from mechanical stripping). One suggestion that we had was to permit us to pretin the wire with a ROL0 halide free flux, water wash and then crimp on the mating part.  The response I received was "In response to question 1. No. Stranded wire must not be tinned when using crimped contact.
>
>There are two reasons I'm aware of: 1. The crimp would not hold properly. 2.
>Tinning stranded wire makes it brittle. Brittleness is not an issue at the
>CCA end of this wire because it gets potted, but the crimp-connector end is
>subjected to movement and vibration. "
>
>Any feedback on this- the application is an high reliability avionics application and must conform to IPC-A-610 Class 3. I would think that pretinning the wire would effectively distribute any forces over a larger cross sectional area (the solder would wet between the individual stands of wire). I would think that pretinning would not make the wire brittle but the  downside I could think of- 1.making sure that all flux residues are out of the joint,
>2. the insulation is not damaged by the pretinning,
>3. and increasing the resistance of the interconnection
>
>Any information would be appreciated.
>
>
>
>
>Tom Gervascio
>Senior Process Engineer
>Sparton Electronics
>(352) 540-4040
>
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