AI-Mg合金によるハンダ中のSb, Cuの同時除去

Abstract

Antimony and copper, which are included in soft solder as impurities, are difficult to be removed by the normal refining procedures applied to lead bullion. It was shown in the 1st report that antimony could be removed by addition of magnesium, which formed the intermetallic compound, Mg3Sb2, having a high melting point and a low density. It is shown in the 2nd report that aluminium, which is almost immiscible into soft solder, is an excellent reagent for the removal of copper from soft solder.The soft solder which contains copper as the impurity was melted with a small amount of aluminium at 900° and was cooled slowly to 400°C. Aluminium phase floats on the surface of the soft solder and copper is absorbed in this aluminium phase. Copper content in the soft solder is decreased from 0.45% to 0.01% by the addition of 1 wt% of aluminium.Magnesium or aluminium must be added in the soft solder at the higher temperatures than the melting points of these metals for the effective removal of antimony or copper. The soft solder which contains magnesium or aluminium is easily oxidized in air at above 500°C, so the alloy of magnesium and aluminium which has a lower melting point was used for the practical application for the simultaneous removal of antimony and copper.The allo of maesiumand aluminium, of which the melting point is about 450°, is added into the molten soft solder at 450°. The scum which contains a lot of minute Mg3Sb2 and Al-Cu is formed and floats out on the surface. The antimony and copper can be removed from about 1% and 0.45% to less than 0.01% and 0.001% by the small semi-continuous refining apparatus.