Surface Contaminant Characterization Using Potential-Current Curves

Results are reported of an investigation of potentialcurrent curves for the characterization of contaminants on electrical contact surfaces. It was found that pronounced leveling of the potential (decreasing contact resistance) occurs as the junction temperature is raised through the melting temperature of the contaminants. Thus the characteristic shape of potential-current curves may be used to distinguish between low- and high-melting organic contaminants and between these and oxides or refractory particles. This in situ diagnostic test has found recent industrial application in the manufacture of sensitive switches and in troubleshooting switches after prolonged inactive storage in the field.