Sn-58Biの応力集中部からのき裂発生および伝ぱ挙動に及ぼす添加元素の影響

Abstract

This study discusses the effect of additive elements on crack initiation and propagation behavior for Sn-Bi solders at high temperatures. Sn-Bi solders are lower melting point temperature materials, so that it is useful for low temperature soldering. Cyclic push-pull fatigue test with center through holed specimen were conducted at 313K and 353K in order to investigate the crack initiation and propagation behavior from stress concentration part of three kinds of Sn-Bi solders. Crack initiated at the early stage and almost of the life period were crack propagation process for the three kinds of Sn-Bi solders. Crack propagation direction at 353K was the maximum shear direction although the maximum principal direction at 313K. The reason for the crack propagation direction difference might be change of slip system at high temperature. There were additive elements Ag, Cu, Ni and Ge effect on the crack propagation rate although there was no effect on the crack initiation cycle. The crack propagation of Ag, Cu, Ni and Ge added solder seems to have a slower rate than that of Sn-58Bi solder. We also investigated the adaptation of J-integral range parameter which is usual used for crack propagation rate evaluation for conventional steel. The J-integral range parameter evaluates the crack propagation rate independent of the additive elements at high temperatures.