Investigation of Void Nucleation and Propagation in the Joule Heating Effect During Electromigration in Flip-Chip Solder Joints

Abstract

This study analyzes the effect of void propagation on the temperature increase of solder joints by using x-ray microscopy, Kelvin probes, and infrared microscopy. It was found that the temperature rise due to void formation was less than 1.3 degrees C when the voids depleted about 75% of the contact opening, even though bump resistance had increased to 10.40 times its initial value. However, the temperature rose abruptly with an increase of up to 8.0 degrees C when the voids depleted 96.2% of the contact opening. A hot spot was observed immediately before the occurrence of open failure in the solder bump. The local increase in temperature was about 30.2 degrees C at the spot. This spot may be the remaining contact area immediately before the occurrence of open failure.