Electrical Contacts and Hazardous Substances - Technical Backgrounds, Legal Restrictions, and Substitutions

The development of our civilization and our way of life is related in many respects to technical progress. On the other side, it became evident that some substances and materials with advantageous technical properties harm the environment and human health. Based on increasing concerns about hazardous substances, restrictions arose and triggered efforts to develop substitute materials or even new technological solutions. These environmental concerns also came up for electrical contacts, contact materials, contact carriers, and soldering alloys. The paper gives an overview of the use and replacement efforts for mercury, lead, beryllium, nickel, cobalt, and cadmium. The focus is on replacing silver cadmium oxide contact material for arcing contacts with different silver tin oxide or silver zinc oxide types. The paper shows how combinations of oxide content, oxide grain sizes, additives, and manufacturing techniques influence silver metal oxide switching properties. Based on these findings, it was possible to replace silver cadmium oxide with environmental-friendly silver tin oxide material in most applications.