Why Gold interconnects?

[33 1/3]

I was reading up on which metal was the best conductor, and it seems to be silver.

I'm wondering therefore why gold is so often used for interconnects, as silver would be cheaper and better?

[Ali Tait]

Silver tarnishes. Gold does not.

[Barry]

Gold won't oxidise or tarnish at normal temperatures, which is why it has been used since antiquity for jewellery. Silver readily tarnishes, although the tarnish (silver sulphide) is soft and is easily wiped away through the action of mating and demating the connector.

Silver has a conductivity that is only 6% better than that of copper, whereas for gold the conductivity is 29% poorer. However since the amount of gold in the signal path is low, the implied relative losses are academic. This would explain why the use of rhodium has become increasingly prevelant as a plating finish on connectors: it is hard wearing (which it is why it is used a plating option on wristwaches), yet has an electrical conductivity that is only 40% that of copper.