Microstructural evidence of the chemical driving force in eutectic SnPb electromigration

An observation of electromigration behavior in a eutectic SnPb solder with various line lengths was performed using an in-situ scanning electron microscope chamber with a 100 °C, 3 × 104 A/cm2 condition. Edge-drift occurred at the cathode, and hillocks formed at the anode were observed at the eutectic SnPb solder stripe during current stressing. The incubation time for the edge-drift and the edge-drift velocity increased as the line length was increased. This result is discussed along with the void nucleation stage of the solder bump and the electromigration back flux force. The existence of the electromigration product (jL) and its line length dependency are also discussed.