Au-Sb and Au-Ag-Sb alloys as low-voltage contact materials

A recent investigation has shown that the increase in contact resistance of low-voltage, noble-metal electrical contacts with the number of on-off switch cycles is primarily due to carbon formation on the contact surfaces. Moreover, when contact electrodes were made of the base metals Ni, Fe, Ti, or Sb, carbon formation was delayed, though not eliminated. Among these, Sb was found to be most effective against carbon formation. Because of its high electrical resistivity and poor oxidation resistance, however, pure Sb cannot be used for electrical contacts. Thus in this study Au-Sb and Au-Ag-Sb alloys of various compositions were prepared and tested to evaluate their carbon formation behavior. An impact tester that simulated the operation of electromechanical relay contacts was used, and experiments were conducted in an atmosphere of air-benzene mixture at room temperature. Of the alloys tested, the ternary Au-7Ag-30Sb alloy was found to be the best