Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!rochester!kodak!ornitz
From: ornitz@kodak.UUCP (Barry Ornitz)
Newsgroups: sci.electronics
Subject: Re: Which is a better conductor: gold or silver?
Summary: more than just resistance involved
Keywords: gold, silver, microwave, tarnish, conductivity
Message-ID: <1986@kodak.UUCP>
Date: 18 Jul 89 13:13:19 GMT
References: <14172@swan.ulowell.edu> <19729@louie.udel.EDU> <20483@cup.portal.com> <996@maestro.htsa.aha.nl>
Reply-To: ornitz@kodak.UUCP (Barry Ornitz)
Followup-To: sci.electronics
Organization: Eastman Kodak Co, Rochester, NY
Lines: 33

In article <996@maestro.htsa.aha.nl> cees@htsa.UUCP (Cees Keyer) writes:
>In article <20483@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) 
writes:
>>As John Berryhill said, gold is used for corrosion resistance on contact
>>surfaces.  It's not a very good conductor, as metals go.  It's electrical
>>resistance is not important because it's a thin layer.
>I think that the resistance is important. 
>The reason that it's a thin layer is nonsense because 
>gold is also used in the high frequency technology
>but in that high freq. region the major part of the resistance
>is contributed by the "skin effect" so the reason 
>"it's just a thin layer" is nonsense. 

The reason gold is used in microwave work is not because of lower surface
resistance, but rather because of its chemical inertness.  Silver is a much
better material to plate microwave cavities with, but silver tarnish is a
much poorer conductor than silver.  Often an extremely thin layer of gold
is plated over silver to provide corrosion protection without seriously
degrading the high conductivity of the silver layer.  In the chemical industry,
connector corrosion on instrumentation is a severe problem.  It is even worse
in the pulp and paper industry.  Heavy gold plating of printed circuit edge
connectors is quite necessary.  On the custom PC boards we make, we first
plate with nickel and follow with gold to avoid problems.
                                        Barry
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|  ___  ________  |
| |  / /        | |  Dr. Barry L. Ornitz  UUCP:..rutgers!rochester!kodak!ornitz
| | / /         | |  Eastman Kodak Company
| |< < K O D A K| |  Eastman Chemicals Division Research Laboratories
| | \ \         | |  P. O. Box 1972
| |__\ \________| |  Kingsport, TN  37662       615/229-4904
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