微小SACはんだ試験片の疲労寿命に対する初晶Snの分布形態の影響

抄録

In the previous study, we conducted tensile tests using a miniature specimen of Sn-3.0Ag-0.5Cu (SAC) solder and found out that the tensile strength of the specimen showed larger variability in the tensile strength than the ordinary size specimen even though the loading conditions were the same. Having investigated the shape and distribution morphology of primary Tin crystal in the specimen after the tests, it was found that the high-strength specimen had the primary Tin crystals which had grown in directions vertical to or parallel to tensile direction, while the low-strength specimen had the crystals which had grown in directions of about 45-degree. In addition, we found out that the growth direction of the primary Tin crystal also affected the creep resistance of the miniature SAC solder specimen. Since the fatigue lives of solders are affected by both the strength and the creep characteristics, the fatigue life of the miniature SAC solder specimen could be affected by the distribution morphology of primary Tin crystal. Therefore, in this study, we carried out fatigue tests using the miniature SAC solder specimens under multiple load conditions and discuss the correlation between the fatigue life and the distribution morphology of primary Tin crystal.