I would like to replace the gold plating of an electrical spring contact with
another material to save money.  Currently we use two gold plated surfaces that
are electrically connected by a gold wire spring which makes surface contact
with the two gold pads.  The spring is in place to compensate for expansion and
contraction driven by temperature changes.  I really do not know of any need to
replace the spring but would like to replace the plating on the two contact
surfaces.  The processing problems associated with plating the gold on the
contact surfaces is the main driver for change.  Currently they are brush
plated and this will not facilitate the production volumes anticipated.  The
intent of the package is to function for a minimum of twenty years and may be
hermetic if required.

The current subcontractor for the two contact surfaces has suggested
replacement by simple solder plate (Pb/Sn).  I am concerned that this would be
unreliable due to migration or dendrites or something.  I have never seen Pb/Sn
used as a contact surface.

Could carbon be used when applied by a thick film process?  Would Palladium
work?  Would it be any cheaper?  Any other ideas?