Micromechanical behavior of single crystalline Ni3Sn4 in micro joints for chip-stacking applications

The micromechanical behavior of single crystalline Ni3Sn4 with different crystallographic orientations are investigated by using micropillar compression and nanoindentation. Knowledge of the mechanical behavior of Ni3Sn4 is important because of its application in micro joints for chip-stacking applications. During high temperature aging, annealing twins easily form in Ni3Sn4 and the twin elements are identified. The stress-strain curves from micropillar compression show that Ni3Sn4 usually exhibits a brittle fracture behavior. However, pillars with certain orientations do not undergo catastrophic fracture, but are able to deform plastically. Transmission electron microscopy analysis shows that dislocations with Burgers vector [0 1 0] are involved in the plastic deformation and the slip system of Ni3Sn4 is (1 0 0)[0 1 0]. The reasons why Ni3Sn4 slips on (1 0 0) plane along [0 1 0] direction is discussed in terms of its crystal structure and Peierls-Nabarro model. In addition, grain orientations near (19 7 1) and (17̅ 6 1) are more likely to activate the slip system (1 0 0)[0 1 0], and exhibit better mechanical properties. Young's modulus, yield strength, fracture strength, strain at fracture, and strain at yield along several orientations are reported.