Abstract
Sn and Pb-Sn plating steels are generally used as solderable outer-packaging materials for electrical machinery. Short-circuiting of electric machine parts due to the growth of Sn whiskers and the adverse influence of poisonous Pb on the environment arising with such materials have become increasingly serious problems.
Electrogalvanized steels have been used as replacements even though their solderability is not as good as that of Sn and Pb-Sn plating steels.
To improve solderability, we have studied Ni, Fe, and Sn preplating on electrogalvanized steels. In this report, we investigated solder spreadability, wettability, and peeling strength.
Ni or Fe preplating under the Zn plating layer effectively improved solderability. Ni preplating showed a particularly excellent value for solder peeling strength.
It was found that, while Zn gradually dissolved in solder, preplated Ni or Fe did not. This prevented the surface of the base steel from being exposed. Ni or Fe also formed Ni3Sn2, Ni3Sn, or FeSn2 with solder. These improve steel solderability.
