Electroplated Aluminum Pillars for Ultrasonic Flip Chip Bonding

Abstract

Flip chip bonding is a widely used method in 3D integration. In this study, the use of electroplated Aluminum as pillar structure for ultrasonic flip chip bonding is demonstrated for the first time. Al pillars were deposited from a chloroaluminate ionic liquid on a 6 inch silicon wafer. The influences of ultrasonic bonding parameters (bonding time, ultrasonic power and bonding force) were investigated at room temperature. Al pillar bonding was performed successfully in less than 1 s. High bonding forces are recommended as more pillars get mechanical contact to the substrate, thus, ultrasonic energy can be transferred to the interface causing bonding.