Hello Technetters,

I am writing as a fabricator, but my question is about design...more
specifically, the functionality of keypad contacts.

In jobs we produce, the "contact coating" of the circuit geometry is usually
specified as carbon ink or electrolytic gold where the elastomeric button
makes contact. However, there is a new job in the design stage right now that
utilizes a stainless steel pill/button to make contact, and (for various
reasons) I was wondering why bare copper would not work. The field environment
is "indoor" but there is expected to be high temperture and humidity swings,
and the contact resistance must remain very, very low I am told (less than
what is achievable with a carbon coating), and remain so "forever".

I know solderability degrades as the copper surface ages and oxidizes, but
does it also become less conductive? Is there any other reason bare copper
should not be considered for this application?

Thanks in advance for your help.

Bill Parlin

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