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Degradation and regeneration of copper electrical junctions.

Earlier theories proposed to explain the increase in contact resistance that occurs randomly in semipermanent copper junctions are shown to be inadequate in explaining several characteristics of the junction-degradation process. A theory is proposed that attributes the degradation to fretting corrosion which produces a granular metal interface. It is shown that the degraded junction retains its metallic conduction properties, but with greatly increased resistivity. It is further proposed that the decrease in the junction resistance by passage of current through the junction occurs by chemical reduction of oxide particles. Degradation of naturally adsorbed carbonaceous contaminants occurs at the elevated temperatures produced by Joule heating of the interface producing decomposition products that reduce the junction oxide as simulated by studies using Auger-electron spectroscopy and thermal desorption on copper foils.