Study of electromigration in eutectic SnPb solder stripes using the edge displacement method

Electromigration (EM) parameters in the eutectic SnPb solder were measured using the edge displacement method (EDM) and an atomic force microscope (AFM) in the temperature range of 60° to 140°C. The measured drift velocity was found to be 0.3 Å/sec when the solder stripe was stressed under 4.9×10⁴ A/cm² at 80°C, and it increased as the current density or the temperature increased. The products of DZ* at 60°C, 80°C, 100°C, 120°C, and 140°C were also obtained. In addition, the EM activation energy was determined to be 0.45 eV at the temperature range 60–100°C and 0.55 eV at the temperature range 100–140°C. These two activation energies may correspond to the Sn and Pb diffusion at the two temperature ranges. These values are very fundamental to current-carrying capability and mean-time-to-failure measurement for solder joints.