鉛フリーはんだ材の砂時計型試験片を用いた疲労強度と圧縮応力負荷による損傷回復に関する研究

抄録

Lead free solder materials have been widely used for electric circuit boards. Solder joints are subjected to fatigue damage due to the temperature change and creep damage due to long term load derived by elastic follow-up phenomena. And it was known that the interaction between fatigue damage and creep damage shorten the life of solder joint. In our previous study, fatigue tests were carried out for Sn-3.0Ag-0.5Cu solder material at an elevated temperature varying the strain rate. And lives varying the strain rate were discussed from view points of the interaction between creep and fatigue damages and the damage recovery under compressive stress. Hourglass test pieces, which could avoid buckling under compressive load, were applied to the low cycle fatigue tests instead of usual cylindrical test pieces of Sn-3.0Ag-0.5Cu in order to establish an experimental method for confirming directly damage recovery under compressive stress. As the result, the break definition based on 8% load drop condition with hourglass test piece corresponded with conventional fatigue curve obtained by 25% load drop with cylindrical test piece. In this study, fatigue test carried out for the solder material at an elevated temperature, and the damage mechanism was discussed from the viewpoint of cross-section observation.