Chuang Weber said:
>Please forgive my ignorance but what is the impact if there is solder on
the gold finger, I mean is there any >defect? What is it then? Thanks for
your kind reply!

>Best Regards
>Weber Chuang
>SI Engineer, SYSTEM Team.
>VIA Technologies, Taiwan, ROC

Chuang: I'm almost as ignorant, but I was recently at a presentation by
J.M. Ney Company about the need for gold plating. If a tin plated connector
is mated to a gold plated connector, the result is that the termination
robustness is equal to if both connectors are tin. Tin has the problem that
it oxidizes. The tin oxide can built up over time in a physical mechanism
called fretting, where small vibrations at the contact point causes
successive breaking of oxide to form cracks that allows more oxidation in
the cracks.
The long and the short of it is that if you have tin over the gold fingers,
and the terminal is a low current connection/low contact force connector,
the contact resistance grows over time (hotter is faster), until the
connection goes open circuit.
If you are connecting to 12V or higher, a tin plating with grease is OK,
because the voltage will breakdown the oxide layer (dielectric breakdown).
They have some figures showing the robustness of various contact materials
including (of course) some of their own. You can contact them to get the
info @
http://www.jmney.thomasregister.com/olc/jmney/
or
E-mail:
[log in to unmask]

Dave Weber
Visteon

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