The effect of silver composition and additives on switching characteristics of silver tin oxide type contacts for automotive inductive loads

Four silver tin indium oxide materials with different total oxide content and minor additives have been tested with an automotive inductive load under different conditions by using a model switch. The contact erosion, contact temperature rise, contact resistance and welding force have been measured and analyzed. The results indicate that the total metal oxide content is the predominant factor for all measured characteristics and that the minor addition tellurium (Te) has very little effects only on material transfer under the inductive load testing conditions. The longer electrical endurance testing results show that the short make bounce (<80 μs) is the cause of high contact welding strength. The local pip and crater formation is result of making bounce arc erosion and it is always associated with the contact weld. The high contact over-travel can delay the pip and crater formation, thus prolonging the number of contact operations or the contact life.