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The relationship between electromigration behavior and the crystallographic orientation of Sn grains was investigated. The test vehicle was the Cu/Sn-3.0wt%Ag-0.5wt%Cu/Cu dummy flip-chip model, and the applied current density was 15 kA/cm2 at 160°C. The depletion of Cu atoms at the cathode side is a major cause of the early circuit failure. Electromigration behavior and the growth of intermetallic compounds were strongly depend on the orientation of Sn grains with respect to the electron flow. Rapid failure occurred when the c axis of Sn grains close to the parallel to the direction of the electron flow, due to the Cu depletion at the cathode side. Slight microstructural changes and improved electromigration properties were observed when the c axis of the Sn grains close to perpendicular to the direction of electron flow.