The influence of the joint size on low cycle fatigue characteristic of Sn-Ag-Cu has been investigated by a micro size joint specimen fabricated using solder balls. Although the effect of joint size on crack initiation life is not obvious at 298K, the reduction of the joint size changes the cyclic strain hardening nature and the fracture behavior that induces the life reduction at 398K. With a decrease in size, the failure mechanism transforms from a transgranular fracture to an intergranular fracture at the high energy grain boundary that is formed by high angle boundary formation following dynamic recovery in whole of joint. Therefore, the failure life is greatly reduced as a complete failure occurs simultaneously with the crack initiation at the grain boundaries. This is more remarkable at higher temperatures.

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