PURPOSE: To obtain solder paste having excellent solderability and preservable stability by coating the surfaces of solder alloy powder particles with a rust preventive or other metals.
CONSTITUTION: The powder of, for example, an eutectic alloy (Sn 91.2%-Zn 8.8%) of tin and zinc and having a grain size of 20 to 40μm is used as the zinc-contg. solder alloy powder. The powder is coated with a coating material. The rust preventive, such as 1,2,3-benzotriazole or methyl imidazole, is used as the coating material. Gold, silver, tin or palladium or the alloy thereof is used as the coating material. The solder paste comps. is formed by mixing the solder alloy powder contg. the zinc coated with these metals with a flux. As a result, the deterioration in the stability of the solder paste and the degradation in solderability are prevented.
ANADA TAKAAKI
SHIMA TOSHINORI
KONO MASANAO
