Study of void formation due to electromigration in flip-chip solder joints using Kelvin bump probes

Kelvin bump probes were fabricated in flip-chip solder joints, and they were employed to monitor the void formation during electromigration. We found that voids started to form at approximately 5% of the failure time under 0.8A at 150°C, and the bump resistance increased only 0.02mΩ in the initial stage of void formation. Three-dimensional simulation was performed to examine the increase in bump resistance at different stages of void formation, and it fitted the experimental results quite well. This technique provides a systematic way for investigating the void formation during electromigration.