| 摘要 |
PROBLEM TO BE SOLVED: To improve the creep resistance and the thermal fatigue resistance of a soldered part by containing Sn, Ge, Ti, Sb, Ag and Pb of prescribed quantity in the solder. SOLUTION: The solder has the composition consisting of, by weight, 61.997.5% Sn, 0.01-0.58% Ge, 0.001-0.04% Ti, 0.2-3.5% Sb, 0.5-2% Ag, and the balance substantially Pb. When the solder is solidified, Ge and Ti are dispersively solidified in the particles of the two-phase coexistent structure ofαPb phase andβSn phase. The particles form the solder structure of fine particle dispersion type, and precipitation ofβSn particles from theαPb phase and precipitation ofαPb particles from theβSn phase are suppressed. Thus, the solder structure is not coarsened, and the softening phenomenon is prevented. The creep resistance and the thermal fatigue resistance of a soldered part are improved. Sb is solid-solved in the structure, and Ag precipitates Ag3 Sn compound in the intergranular boundary to reinforce the solder structure. Ge and Ti prevent the solder structure from being coarsened or softened.
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