Electromigration in a Liquid Bridge before Contact Break

Material transfer between electrode surfaces during contact make and break is usually associated with mechanisms such as evaporation of electrode material, gaseous ion transport due to arcing etc. Material transfer on contact break also occurs in the absence of arc formation. This paper focuses on material transfer during contact break, in the absence of an arc. It is proposed that transfer occurs largely by “solid state” electromigration rather than from the generation of Thomson heat in the liquid metal bridge before contact separation, conjectured by earlier investigators. Illustrative calculations are carried out for the case of separating silver contacts. The calculations show that electrotransport in the liquid metal bridge is appreciable due to the large rate of self diffusion of silver at the high temperatures in the molten bridge. The calculated mass transfer rates in the molten bridge due to electromigration are compared with experimental values reported in the literature.