2018 年 82 巻 5 号 p. 153-161
Many studies have been done so far about the occurrence of whiskers in Sn-plating. However, very few study has been conducted on the suppression method of whiskers, how to prevent occurrence of whiskers. It is empirically known that whiskers are suppressed by heat treatment. However, its suppression mechanism is still unknown.
In the present study, we investigated that how the amount and form of the intermetallic compounds, generated by heat treatment, change with an elapsed time. Then, effect of the amount and form of the intermetallic compounds on the occurrence of Sn whiskers was studied in detail. As a result, it was clarified that, in order to suppress the whiskers, the amount of the intermetallic compounds should be above 15%. The parameter, named as contour-length ratio, was introduced for expressing the uniformity of occurrence of the intermetallic compounds. This value should be above 1.2 to suppress the whiskers.
