AgSnO2 electrical contact material is a new Cd-free contact material newly developed by electrical contact researchers from various countries in recent years. It has good electrical and thermal conductivity, and has high heat resistance to arcs during the making and breaking process. It has excellent arc corrosion resistance and welding resistance, thereby ensuring the reliability of electrical appliance operation and increasing its service life. This material is close to or even better than AgCdO material in many properties. It does not pollute the environment during production and application and is non-toxic to the human body. It is currently an ideal material to replace AgCdO.

    Since the 1970s, domestic and foreign research institutes and large companies have focused on research on AgSnO2 electrical contact materials. At that time, Japan and West Germany used the internal oxidation method to develop AgSnO2 contact materials. When the silver-tin alloy is oxidized, a layer of SnO2 is formed on the surface, which prevents the silver-tin alloy from further oxidation. This is called "oxidation resistance" phenomenon. For this reason, adding a certain amount of In can accelerate oxidation, break the "oxidation resistance" phenomenon, allow oxidation to continue, and ultimately form a new electrical contact material AgSnO2In2O3. It was first put into production in Japan and used to replace AgCdO contacts on some switches. But it has two shortcomings: First, it adds metal In, which has very few reserves in the world, and most people think it is not suitable for large-scale promotion. Second, although the temperature rise of AgSnO2In2O3 contacts is higher than that of AgCdO contacts, the contact pressure of Japanese plastic circuit breakers is greater. During the making and breaking process, the oxide on the contact surface is easily broken under greater pressure, and Japan does not rely on IEC standards and does not assess the temperature rise after the test, so there is no problem of low temperature rise. Western European electrical appliances have low contact pressure and rely on IEC standards.  The temperature rise must be assessed after testing. Therefore, the temperature rise of AgSnO2In2O3 contacts has become the main problem to be solved in the development of this type of material.

    Over the years, experts from various countries have done a lot of research and exploration on ways to reduce the temperature rise of AgSnO2 electrical contact materials. In the early 1980s, the German Degussa Company successfully developed AgSnO2 (SPW) contact materials using a powder sintering extrusion process. It was used in AC contactors greater than 75A. Its electrical life is twice as long as that of AgCdO, while the temperature rise is similar. The company conducted comparative analysis tests between AgSnO2 (SPW) and various other AgMeO, proving that only AgSnO2 (SPW) has the best performance. Its welding resistance and temperature rise are as good as AgCdO(SP), and its arc corrosion resistance is more than twice that of AgCdO. Therefore, AgSnO2 (SPW) can completely replace AgCdO contacts on electrical appliances with a current level greater than 75A, and can also avoid Cd contamination; however, AgCdO is still preferred for electrical appliances with a current level less than 75A.

    At present, the performance of AgSnO2 alloy contacts is equivalent to that of AgCdO. However, because the AgSnO2 material is relatively "personalized", it is not as "universal" as the AgCdO material. AgSnO2 materials with different contents and different processes are often developed according to different electrical structures and usage requirements. At present, some domestic companies have noticed this and are constantly improving AgSnO2 materials in terms of material system and processing technology.
    Fudar Alloy has developed more than 20 AgSnO2 materials through nearly ten years of research, which have been successfully used in contactors, air conditioning contactors, magnetic latching relays, automotive relays, wall switches and other fields.

——The content of the article comes from the Internet