Hidekazu Sueyoshi1, Harunori Odo1,, Shinji Mizokuchi2, Shigeru Abe2 and Kazuya Saikusa2
1Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065
The consumption of soldering iron was examined using Pb-free solder and the solder/soldering iron reaction was discussed in connection with the kinetics. The consumption of soldering iron increased with an increase in solder/soldering iron contact time. When the fused solder was removed by compressed air cleaning, no thick reaction layer was observed at the solder/soldering iron interface. When the fused solder remained on the surface of the soldering iron after such cleaning, a thick reaction layer was observed. As fused solder was held for a long time on the surface of the soldering iron, a thick FeSn2 reaction layer of was formed at the solder/soldering iron interface. The rate of formation of the reaction layer seemed to be controlled by the diffusion of iron through the reaction layer. The reaction layer was relatively hard (Hv 378) and had many voids. It was possible to remove the reaction layer by compressed air cleaning. On the basis of these results, it is clear that the soldering iron consumption due to Pb-free solder occurs according to the mechanism of the formation of a reaction layer of about 30 nm thickness through one soldering process, followed by flaking away with compressed air cleaning.
soldering iron consumption, lead-free solder, reaction layer, diffusion of iron, intermetallic compound
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