The impact and performance of electromigration on fine pitch Cu pillar with different bump structure for flip chip packaging

The electromigration (EM) behavior and performance of solder capped Cu pillar assembled with bump on trace (BOT) processed by mass reflow is measured and analyzed. The interconnections with two different Cu pillar bump structures were tested: Cu post + SnAg solder tip and Cu post + Ni barrier +SnAg solder tip. Emphasis is placed on the EM impact and performance of the two different Cu pillar bump structures. The test temperature ranged from 130–150°C and the current of 500–900mA was applied, which is corresponding to the current density 25–45kA/cm². The substrate side finish is organic solderability preservative (OSP) on Cu trace. The Cu pillar bump pitch is 87µm and the bump size is 50µm. Some important results are summarized in the following.