devices. The efficiency of an electronic device is highly dependent on the solder: the failure rate
of lead-free solders has been found to correlate to its orientation relative to current flow. Leadfree
solders, such as the tin-based solder SnAg-Cu (SAC 305), have a body-centered tetragonal
(BCT) structure with the c-axis being the shortest. When the c-axis is oriented parallel to the
current flow, Cu-Sn intermetallics grow faster in the solder joint, leading to failure. The
reliability of the device can thus be increased by controlling the crystallinity and grain
orientation of the soldered joints. This project studies the effects of copper surfaces on the
crystallinity and orientation of SAC solder joints. The SAC solder was mounted between Cu
pads with surface finishes ranging from 78 μm to 7 μm. The orientations of the Sn and Cu were
examined using electron backscatter diffraction analysis (EBSD). This study has concluded that
increased roughness of the copper surface refines the grain size and strengthens the SAC solders.
No clear correlation was found between the orientation of the Sn to the Cu surface. Additional
studies are being conducted to investigate whether a relationship between orientation and
crystallization of Sn on Cu surfaces can be established.