マグネシウム添加によるハンダ中のアンチモン除去
ハンダの精製に関する研究 (第1報)
1982 年 98 巻 1137 号 p. 1159-1164
詳細
1982 年 98 巻 1137 号 p. 1159-1164
One of the most injurious among impurities in soft solder is antimony originating from lead recovered frombattery scraps. As soft solder contains tin which is easy to be oxidised, removal of antimony by the preferentialoxidation is not applicable to the soft solder unlike the case of lead.
In this study the property of antimony to form with magnesium an intermetallic compound, Mg3 Sb2, wasutilized in removing antimony from molten soft solder. As the compound has a high melting point of 1228° and lowdensity of 1.33g/cm3, when large crystals of the compound were formed, they gathered by buoyant force near the top ofthe molten soft solder and most of antimony could be removed from the bulk.
A sample composed of Sb-containing soft solder and magnesium was melted and kept for lh at 900° in an evacuated quartz ampoule, then cooled at a slow cooling rate down to a set holding temperature. It was again keptfor 1h at the holding temperature and quenched in water for observation of the distribution of the crystals and for analysis ofresidual antimony and magnesium.
A slow cooling rate and a low holding temperature are necessary for the growth of the crystals. At aholding temperature of 350° and by addition of as much wt%Mg as the initial wt%Sb in soft solder can lower the residualantimony to less than 0.01wt%. The solubility relation can be represented by log[%Mg]3[%Sb]2=11.8-11400/T
