Microcracks initiated from steps at the boundary between the Sn-dendrite and the Sn-Ag eutectic structure and cavities along the boundaries especially around the Ag 3Sn particles. After failure, the longitudinal cross sections were also examined using scanning electron microscopy (SEM). Without local deformation and stress concentration at contact points between the extensometer and the specimen surface in strain-controlled fatigue tests, crack initiation and propagation behavior was observed on the specimen surface using a replication technique. ![]() The fatigue behavior followed the Coffin-Manson equation with a fatigue-ductility exponent of 0.76. Low-cycle fatigue tests of as-cast Sn-Ag eutectic solder (96.5Sn/3.5Ag) were performed using a noncontact strain controlled system at 20☌.
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