Electrical instabilities in stationary contacts: Al/Al and Al/brass junctions

Electrical instabilities in Al/Al and Al/brass stationary point junctions has been examined in ultrahigh vacuum and in oxygen gas. It is found that Al/brass junctions are electrically stable in vacuum and in oxygen gas if the surfaces are sufficiently clean. The growth of intermetallic compounds in this interface affects stability only after a sufficiently long exposure of the contact, typically several hours, to a temperature typically higher than 150 degrees C. Surface contaminants, probably in the form of carbonaceous material, are deleterious to the performance of Al/Al and Al/brass junctions. However, the junctions often recover from contaminant-induced degeneration. This recovery is attributed in part to thermal dispersal of the contaminants from the electrical interface during the early stages of degeneration.<>