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 FeSn 2 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.

Abstract. Sn-3mass%Ag-0.5mass%Cu lead-free solder causes strong erosion of Fe plating, which is used in hand soldering. In order to improve the durability of the soldering iron tip, we tried Fe-MWCNT (Multi-walled Carbon Nanotube) composite plating on the tip. Microstructures and the erosion resistance of the Fe-MWCNT composite plating under heating were examined. On the basis of the SEM/EDS analysis, it was confirmed that there were MWCNTs in the Fe-MWCNT composite plating. Even when heated to 673 K, MWCNTs were found to be present in the plating film under a stable condition. It was shown that the performance of erosion resistance for lead-free solders under high temperature (673 K) is improved due to the MWCNT addition to the Fe plating.

Recently the soldering iron tip has been severely damaged by molten Pb-free solders during operation due to the high reaction rate of metals in molten lead-free solder. The tip is usually protected by plated iron to prevent the direct contact of copper with molten solders. However, the plated iron tip is heavily dissolved into molten Pb-free solders and the life time of the iron tip is reduced. In this study the simple reaction test between Sn-3.0Ag-0.5Cu (mass%) solder and plated iron was carried out to estimate the dissolution of plated iron in molten Pb-free solder and the effect of the grain size of plated surface on the reaction between Pb-free solder and plated iron. An iron-plated copper was used as the test piece. The Pb-free solder was placed on the test piece and it was put into an oven held at 673, 703 and 733K for 3.6, 10.8 and 32.4ks. After heating, the dissolution thickness of plated iron was measured and the intermetallic compound between Pb-free solder and plated iron was analyzed by XRD. As a result, it has been made clear that the dissolution thickness of plated iron decreases with the decrease of the grain size and then the dissolution of plated iron in molten Pb-free solder is attributable to the grain size of plated iron.

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