Hi Neil,

There's two different gold finishings for PCBs, immersion gold or hard
gold. Immersion gold is usually good enough and it's pretty cheap. Maybe
the scary quote you got was for hard gold.

Cheerful regards, Bob

On Sun, Nov 23, 2014, at 06:17 AM, Neil wrote:
> I'm not familiar with conductive epoxy, so will investigate that.
>=20
> Silver (which I can get from the PCB house at much lower cost) will=20
> tarnish relatively quickly (few months) so won't be a good choice for=20
> the membrane-switch pads.
>=20
> Cheers,
> -Neil.
>=20
>=20
> On 11/23/2014 1:34 AM, RussellMc wrote:
> > On 23 November 2014 at 18:37, Neil <picdude3@narwani.org> wrote:
> >
> >> I'm looking for a conductive carbon coating that I can apply to PCBs
> >> myself, for conductive membrane switches.  Or something else
> >> ...
> >>
> >
> > Just some ideas.
> > I do not know how suitable any of these would be.
> > I've never tried  them. Each should have level of conductivity needed.
> > May have degree of wear resistance needed.
> >
> > - Conductive epoxy.
> >
> > - Silver-loaded track repair lacquer which does not conduct unti 'set'.
> > As carrier liquid evaporates silver particles produce conductive strip.
> > I've used this for repair of fractures in flexible carbon tracked keybo=
ard
> > tails.
> >
> > - Stick layer of eg butyl rubber (carbon loaded) to board surface in
> > contact with a conductor.
> >
> >
> >
> >        Russell

--=20
http://www.fastmail.com - The professional email service

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.