CONDUCTION IN FAILING ALUMINUM CONNECTIONS

Conduction in failing aluminum contacts is studied using oscilloscope observation of the current-voltage characteristics. Crossed wire and twisted pair contacts are employed in these studies. The dual crossed wire configuration employed permits evaluation of the distribution of the conducting channels. Measurement of contact resistance as normal force is increased shows that there is little metallic contact established through the aluminum oxide by application of normal force alone. Conduction in these aluminum connections is found to be predominantly metallic, however, established and sustained by the electrical breakdown mechanism known as A-fritting. The metallic conductive channels formed by this mechanism deterioriate and open, causing frequent repetition of the breakdown process. The results indicate that there is likely to be only one conducting channel active at a time. Observations made on aluminum-aluminum twisted pair and twist-on connector splices demonstrate that the same mechanism is operative for these connections. The relationship of the results to behavior of failing aluminum connections is discussed.