NNTP-Posting-Date: Tue, 07 Jan 2003 15:28:27 -0600
From: firstname.lastname@example.org (John Fields)
Subject: Re: Reducing contact resistance for low volt use?
Date: Tue, 07 Jan 2003 21:23:26 GMT
Organization: Austin Instruments, Inc.
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On Tue, 07 Jan 2003 04:16:14 GMT, DarkMatter
>On Mon, 06 Jan 2003 15:20:41 GMT, firstname.lastname@example.org (John Fields) Gave
>>I don't believe I made any mention of the reason the military uses
>>it all. However, if you'd like to start a thread on that subject
>>I'd be glad to join in.
> For the silver at 24 gauge it is 25.2 ohms per 1000 feet
That depends on the plating thickness.
> For copper (bare) at the same gauge, it is 25.67 ohms per 1000 feet.
> As for the reasons for silver on wire in the military, it was
>originally used soled in transmitter equipment initially because the
>cost for silver was a lot higher back then.
Your argument that it was used originally because it was more
expensive back then is nonsensical _and_ untrue. Check the Silver
Institute website for the facts.
As I recall, silver was/is used to plate the wire used to make coils
in HF equipment in order to minimize skin effect. I don't recall
silver plated chassis wiring or cables on vintage military radio
>It has since migrated to
>power cabling for corrosion resistance reasons, mainly.
> One of the mentions in the mil specs are susceptibility to "rd
>plague" corrosion, A galvanic response at the copper/silver interface.
>No electrical stimulus needed. It surround plating thickness and
>integrity as oxygen seems to be the culprit. I guess that is why they
>call it "oxidation".
"Red plague" isn't oxidation, it's a form of galvanic corrosion
which occurs in the presence of humidity because of the location of
copper and silver in the electrochemical series. It is exacerbated,
but not caused by the presence of oxygen, and occurs when the silver
plating is too thin, allowing moisture to form an electrolyte
between the two metals, which then become a shorted battery.
> I'm sure there are many other factors. Another good one is that SPC
>is far more solderable (especially over time and environ)than is TPC
>or straight copper even. It remains "wettable" longer.
Since it's the flux in the solder which is responsible for removing
the chemical contaminants from the surfaces to be soldered, I don't
think there's a really big difference between tinned copper, copper,
or silver plated copper.
Professional circuit designer