Silver has the highest electrical conductivity and the highest thermal conductivity of any metal. In this respect it is the best contact material available. It is, however, rarely recommended for use in light-duty applications because of its tendency to tarnish.
The voltage at heavier duties is normally sufficient to break down these sulphide films so that their presence does not affect contact performance.
The addition of copper to Fine Silver has the beneficial effect of increasing hardness and arc-resistance. These alloys have better anti-welding properties for applications up to 100A, but are not as good as Silver-Nickel on “make”. At the same time, however, contact resistance increases as does tarnishing.