Metallographic Study of Dual Type Current Limiting Fuse Element

A newly developed dual-element current-limiting fuse with full protection capability has fuse element consisting of two sorts of metals, i. e. gold-silicon eutectic alloy wire and silver wire being connected in series. The results of the metallographic study is reported on the process of deterioration of fuse element caused by repetition of over-current using high temperature microscope, an electron probe microanalyzer and a regular optical microscope. It is clarified (1) that fusing of the dual-type current-limiting fuse element does not occur at the silver wire section but always at the gold-silicon eutectic alloy wire, and (2) that fine gold-silicon eutectic structure is unifomly distributed in gold primary crystal even after the repetition of over-current and the eutectic structure is stable up to the melting point.