Modeling and Experimental Verification of Intermetallic Compounds Grown by Electromigration and Thermomigration for Sn-0.7Cu Solders

Printed circuit boards that use fine pitch technology have a greater risk of open-circuit failure, due to void formations caused by the growth of intermetallic compounds. This failure mode is reported to be a result of electromigration (EM) damage. Current stressing occurs when current flows in a solder bump, thereby producing EM. Joule heating is also a significant occurrence under current stressing conditions, and induces thermomigration (TM) in solder bumps during EM. This study investigated the intermetallic compound (IMC) growth kinetics for Sn-0.7Cu solders, modeled by EM, TM, and chemical diffusion. The modeling results concurred with the observed kinetics of IMC growth. Electromigration influenced the growth of IMCs most significantly for a current density of 10 kA/cm 2 . The effect of TM on the IMC growth had to be considered for a thermogradient of 870°C/cm. However, the effect of chemical diffusion was insignificant on IMC growth, specifically for a current density of 10 kA/cm 2 .