Welding behavior of Ag/SnO2 contact material with microstructure and additive modifications

Silver cadmium oxide (Ag/CdO) has been the preferred material for contacts due to its excellent performance properties and ease of manufacture into many configurations. Many alternative CdO free contacts, particularly silver tin oxide (Ag/SnO₂), are much more difficult to fabricate because of poor metallurgical properties. This leads to low process yields and higher costs. One correction is to have different mixing techniques to form more workable high oxide content microstructures. Another more simple solution is to have the least amount of oxides in the soft silver matrix. This latter approach is possible only if the anti-welding and arc erosion properties are sufficient. For this study several tin oxide mixtures are compared that can bridge the performances between pure Ag and 85 Ag/15 CdO. This included low oxide content composites with 2 to 8% oxides, mixed oxides with various silver particle sizes and mixes using the advantages of minor oxide additives. In this report, the welding properties are compared to help with contact selection.