Effect of a Third Doping Agent to Ag-Pd Alloy on the Formation of Oxide Films Grown on the Surface

Terutaka TAMAI  Hiroshi OHSAKI  Tetsushi KAWANO  Ichiro TAKANO  

IEICE TRANSACTIONS on Electronics   Vol.E81-C   No.3   pp.369-376
Publication Date: 1998/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Electromechanical Devices and their Surface Science)
Ag-Pd alloy,  micro relay,  contact resistance,  doping with Mg and Cr,  

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On account of its superior electrical contact performance, Ag (40wt%)-Pd(60wt%) alloy has been widely used to the electrical contacts of electromechanical devices. However, regarding small devices, some important difficulties arise due to the small size such as the degradation of the contact resistance caused by the oxide film grown on the surface. To solve these problems, it was reported previously that doping Mg and Cr into the Ag-Pd alloy was tried to improve the oxide film. As a result, the oxide film grown on the Ag-Pd-Mg surface exhibited a remarkably low contact resistance. However, for the oxide film on Ag-Pd-Cr, no improvement of the contact resistance was observed. In this study, to clarify the cause of the low contact resistance for Ag-Pd-Mg, the effect of the doping with a third element on the composition and formation of the oxide film was analyzed using electron diffractometry, XPS and STM. As a result, Ag was found to be distributed on the outermost surface and inside the oxide film formed on Ag-Pd-Mg. However, Ag was not found on the surface of and inside the oxide film formed on Ag-Pd-Cr. Therefore, it was concluded that the presence of Ag on the surface of and inside the oxide film reduces the resistivity of the film.