Size and Volume Effects on the Strength of Microscale Lead-Free Solder Joints.

The fracture behavior of microscale lead-free Sn-3.0Ag-0.5Cu solder joints of different sizes was investigated under quasistatic microtension loading. The experimental results show that the ultimate tensile strength of a joint does not always increase with decreasing thickness-to-diameter ratio ( d/ t), which is commonly regarded as the dominant factor for mechanical constraint in the joint. A clear joint volume effect on the strength has been found, i.e., the joint’s strength increases with decreasing joint volume $$ \left( {V = {\frac{\pi }{4}}d^{2} t} \right), $$ and the correlation follows an inverse proportional function reasonably well. [ABSTRACT FROM AUTHOR]