<Abstrate>

Uniaxial compression experiments on micron-sized bicrystalline and single-crystalline

pillars in tin (Sn) using a flat punch nanoindenter tip, have enabled us to quantify the

difference in stress-strain behavior associated with grain boundaries in tin. It was

found that bicrystalline micropillars containing a twin boundary nearly parallel to the

loading axis were characterized by numerous strain bursts and a yield stress either

lower than or comparable to its single-crystalline counterparts. Transmission electron

microscopy on the deformed micropillar revealed that the twin boundary migration

is associated with partial dislocation activity. The slip systems interacting with the

boundary have also been identified using stereographic projections. Micropillar

compression indicated different findings for bicrystalline pillars containing random

angle grain boundaries, which displayed strengthening by acting as a barrier to

dislocation glide. These results indicate that the grain boundary character plays a

very crucial role in controlling the mechanical response of Sn-rich solder joints

and provide insights into the deformations mechanisms occurring at different boundaries.
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