A Comparison of Contact Attachment Methodology on the Electrical Performance of AgSnO2 Contacts

The electrical performance of contacts can vary depending on the method and degree of success with which the contacts were attached to their current carrying substrates. Contact attachment methodology is particularly important in medium power devices which see many switching operations and where the thermal and electrical conductivity of the bond can significantly influence the overall thermal dynamics within the device and the service life of the device. This paper will review a series of evaluations using NEMA Size 1 AC contactors equipped with AgSnO2 and AgCdO contact assemblies. The contact attachment methodology variations include: welded, continuously brazed, and the influence of various braze alloys. Bond quality will be verified using C-Scan imaging techniques and the performance evaluated under AC4 testing conditions. Results will show the difference in electrical life achieved in a commercial device using similar materials but different attachment methods.