The Effect of Crystallographic Orientation on the Mechanical Behavior of Cu6Sn5 by Micropillar Compression Testing

The anisotropy of the micromechanical behavior of single-crystal Cu6Sn5 was studied by nanoindentation and microcompression testing of pillars. Electron backscattered diffraction was employed to determine the crystallographic orientation and texture of Cu6Sn5 nodules. Characterization results from orientation imaging mapping show that the growth direction of the nodules is somewhat aligned to the c-axis of the unit cell of Cu6Sn5, although a fair amount of deviation exists in several grains. Normal to the growth axis the orientation is random, indicating a fiber texture. The mechanical properties indicate a 20% increase in strength and 7% increase in Young's modulus close to the c-axis relative to normal to the c-axis. Careful analysis of the results based on angle to the c-axis shows a linear decrease in strength with increasing deviation from the c-axis. Our results should help understanding and fracture modeling of Cu6Sn5 under thermal and mechanical loading conditions.