Correlation between incubation time for edge drift and Pb migration in electromigration of eutectic SnPb lines

The smaller flip chip electronic packages are likely to have the higher current densities through their bumps, and this caused a failure due to electromigration at the eutectic SnPb solder bumps. In this study, we have analyzed the edge displacement with time and the relative Pb contents along the line as a result of the electromigration of eutectic SnPb using "edge drift" structures. It was of interest that an incubation stage for the edge drift was observed in the eutectic SnPb electromigration, i.e. there was a time duration before an edge began to move. The time duration for the incubation stage, and the drift velocity decreased in the smaller line length. It was observed that Pb became depleted at the cathode end while a pile-up of Pb was formed near the cathode end after the end of the incubation stage.