Yes, weve designed several projects with the PCB copper used as a contact
for "carbon button" switches. The answer is pretty simple, Yes, copper
works fine, except that as it corrodes it no longer works; also, the carbon
button absorbs the copper oxide until it no longer works.

The answer is simple- simply gold plate that layer! In other words, have
the PCB shop add gold to the copper etches in the area exposed. The gold
will not be absorbed into the carbon button, nor will the pattern oxidize.

In high volume production, there are other metals that are cheaper than
gold, rhodium, for example, but most PCB shops won't have it.

Good luck!

Bob Axtell

At 04:31 PM 6/12/2003 -0700, you wrote:
>I picked up one of Forrest Mims III's mini notebooks at Radio Shack,
>"Electronic sensor circuits & projects". He has some ideas for making
>switches out of pcbs or copper clad boards (for instance, a sensor in which
>vibration causes a wire to touch the copper. Anyway, long story short, I'm
>thinking of doing something similar, essentially building a pushbutton on a
>pcb (a piece of metal that, when pressed, bridges two pads on the pcb), but
>I'm worried that the copper might oxidize or something, preventing good
>electrical contact.
>Any thoughts on the likelihood of that happening? Any ideas to prevent it?
>Maybe some sort of conductive coating for the copper?
>
>
>--m
>
>_________________________________________________________________
>Add photos to your e-mail with MSN 8. Get 2 months FREE*.
>http://join.msn.com/?page=features/featuredemail
>
>--
>http://www.piclist.com hint: The list server can filter out subtopics
>(like ads or off topics) for you. See http://www.piclist.com/#topics

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics