Low temperature bonding studies of Au-studs and AuSn-solder bumps on Au-surface using ultrasonic energy

Conventional flip chip bonding requires heating process to enable solder to melt and electrically conductive adhesives to cure. Applying ultrasonic dose, successful flip chip bonding can be achieved at lower temperatures and bonding pressures. Using ultrasonic flip chip bonding is attractive as the reduction in bonding temperature reduces processing time, by reducing time taken for ramping up and cooling down of bonding arm in thermal compression; it also reduces the mismatch of coefficient of thermal expansion (CTE) between the chip and substrate during bonding compared to thermal compression bond and flux and reflow process. In this study, feasibility of room-temperature ultrasonic flip chip bonding of eutectic AuSn solder and Au-stud bumps was evaluated. Design of experiment was carried out on Argon and Hydrogen plasma process as a pre-flip chip cleaning treatment. Investigation of critical ultrasonic flip chip bonding parameters such as ultrasonic power, bonding force and chuck temperature was carried out. In the full manuscript, details of the experimental trials and results of room-temperature bonding of Au-studs and eutectic AuSn solder bumps on Au-surface would be discussed.