Microstructural features and vibration fracture behavior of Sn-Zn-Ag solder alloys

Mechanical properties of a potential lead-free solder, Sn-9Zn-xAg (x=0.5∼3.5 wt%), are examined in this study, particularly the vibration fatigue behavior. Results show that striated deformation of Sn-rich dendrites contributes to a greater damping capacity and thus the specimens with higher Ag content possessed a higher vibration life when suffering vibration with a constant vibration force. With respect to vibration under a fixed initial deflection amplitude, all the specimens had a similar vibration fracture resistance under low strain amplitude conditions, while high Ag specimens had a higher vibration cycles to failure under high strain conditions. This was closely related to the striated deformation along the main crack.