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Following the trend of miniaturization of VLSI devices, the current density of flip-chip ball bumps has increased significantly and each solder joint is supporting a current density close to 10/sup 4/ A/cm/sup 2/. Therefore, in SnPb eutectic solder, which has a high diffusivity at the operating temperature due to its low melting point, electromigration became a major reliability threat. We have investigated electromigration behavior of eutectic SnPb solder using thin stripe-type specimens. From the 80/spl deg/C and 100/spl deg/C testing, the activation energy for electromigration was calculated as 0.9 eV and the dominant diffusion paths were through interface and surface. From the compositional analysis, it was found that Pb is a dominant migrating species over Sn atoms for 100/spl deg/C testing.