Surface Modification Effect on Ultrasonic Bonding for Aluminum Pad Arrays

Abstract

This study develops and optimizes Al-to-Al direct bonding for multi-level assembly using ultrasonic technique. Sputtered Al pads prepared by subtractive method were adopted. Effects of plasma pretreatment on joint strength are systematically investigated. Other than surface roughness and surface hardness, experimental results suggest that surface energy, which was affected by the plasma gas and input power, is the dominating factor for Al-Al direct bonding.