Abstract
The deformation behavior of solder alloys shows remarkable strain rate dependency. Then, the fatigue life of solder alloys is possibly affected by the strain rate for the cyclic loading. In this work, the fatigue tests of Sn-3.0Ag-0.5Cu (SAC) solder were conducted using cyclic tension-compression loadings under several strain rate conditions. The fatigue life of solders alloys showed the strain rate dependency: the fatigue life under the slow-fast condition was shorter than that under the fast-slow condition even though the strain amplitude and the time period for the loading were equal. The appearance of the fatigue fracture surface also differed by the strain rate condition, such as the slow-fast condition or the fast-slow condition. To discuss the causes of these strain rate dependencies, the development behavior of the plastic and creep strains generated during each cyclic loading was investigated by employing stepped ramp wave loading. Using the investigated results, a method which can evaluate the fatigue life of the SAC solder suitably was also discussed.
