In article ,
Gareth Magennis wrote:

Is there a tried and trusted way of adding a conductive contact pad?

For what it's worth: I've had pretty good luck restoring conductive
pads using a product called Neolube #2. It's a water/alcohol
suspension of extremely fine graphite, with a small amount of a
thermoplastic resin (possibly cellulose acetate?) as a binder. It can
be applied with a fine brush or Q-tip.

I recently purchased a bunch of surplus Kenwood UHF mobile radios.
About half of them had intermittent or non-working keys on the molded
keypads. The pad sheet had originally been made with some sort of
sprayed-on or molded-on conductive coating, and I could see where it
had been worn off the keys in question (the rubber was shiny and I
could actually see the shapes of the corresponding PC-board traces).

Cleaned with alcohol, painted on a couple of thin coats of Neolube,
and they work fine.

I can't swear as to how long it will hold, but Neolube seems to have a
respectable "grip" on the surfaces I've painted it onto. Its info
sheet is interesting... they talk about how its carbon is so pure than
neutron activation of contaminants isn't an issue, and so it's rated
for use in nuclear reactors.