Metal oxide on the surface of contacts having excellent contact performance

Ammonium sulfate was found on the speech path contacts of XS type crossbar switches in the electronic switching systems of NTT when the contact failures occurred. On the basis of this finding, the contacts of 99%Au-1%Ni alloy in contact with Pd were developed for the push button dial contacts of telephone sets. These contacts maintain excellent contact performance. This development was based on the hypothesis that some metal oxides preserve the contact performance from the contact failures due to air pollution. A mechanism for the occurrence of contact failure by air pollution is proposed, and some experiments on the surface characteristics of 99%Au-1%Ni alloy, which support the verification of the mechanism, are described