Method for the production of sintered electrical contact material for low voltage power switching

摘要

Contact materials based on AgSnO.sub.2 and having Bi.sub.2 O. sub.3 and CuO as further metal oxide additives were previously disclosed. In these materials the total content of all metal oxides was supposed to be between 10 and 25% by volume with the SnO.sub.2 share equal to or greater than 70% by volume of the total amount of oxide.PP According to this invention the quantity of SnO.sub.2 is kept smaller than 70% by volume; specifically at about 65%, but in any case equal to or greater than 50%. The SnO.sub.2 weight content is to be in the 4% to 8% range and the weight percentage ratio of SnO.sub.2 to CuO is to be between 8:1 and 12:1.PPIn the associated production process, either Bi.sub.2 O.sub.3 powder is purposely admixed to an internally oxidized alloy powder (IOAP) in an additional operation, a grain restructuring with locally different Bi.sub.2 O.sub.3 concentrations occurring in the structure after sintering and compacting. Alternatively, higher bismuth percentages in the alloy powder can be worked with directly, which is again internally oxidized to an IOAP. From these starting materials two-layer sintered contact elements with a solderable silver layer can be efficiently produced.