Effect of iron plating conditions on reaction in molten lead-free solder

Abstract

To demonstrate the dissolution of plated iron in molten lead-free solder and the effect of iron-plating conditions on reactions in molten lead-free solder, the reaction test between Sn-3.0Ag-0.5Cu (mass%) solder and plated iron was performed. An Iron-plated copper plate, which was made by electroplating iron onto an oxygen-free copper substrate, was used as the test piece. The reaction test was carried out by using an oven in normal air. The solder was placed on the test piece and it was put into an oven held at 400, 430 and 460°C. The interface between the solder and plated iron was particularly examined. It was found that the intermetallic compound of FeSn2 was formed at the interface regardless of the plating conditions. The results showed that the grain size of plated iron decreased with the increased current density and the dissolution thickness of plated iron in molten lead-free solder increased with the increased current density in the rack plating. In the barrel plating, the grain size was rather small in all the test pieces and the dissolution thickness was rather thick. Thus it has been made clear that the dissolution of plated iron in molten lead-free solder is attributable to the grain size of plated iron.