Research on Longitudinal Ultrasonic Vibration Assisted Flip Chip Bonding Process

The current flip-chip bonding technology still faces defects such as surface thermal burnout of chips due to excessively high process temperature and significant mechanical stress leading to solder joint fracture and chip damage. This paper proposes a longitudinal ultrasonic-assisted flip-chip bonding process. By introducing ultrasonic vibration of a certain frequency in the bonding direction, stress on the device during the bonding process is reduced, leading to lower bonding temperatures and improved bonding quality and reliability. However, unreasonable ultrasonic bonding parameters may result in the fracture at the bonding interface by hammering effect. Based on the longitudinal ultrasonic-assisted bonding experimental platform was constructed to conduct bonding experiments. Through orthogonal contrast experiments, it has been determined that longitudinal ultrasonic assisted technology could reduce the bonding temperature at most by 180°C and bonding duration by 3-5s with ultrasonic parameter of 26W/cm
²
sound intensity and 4~4.66MPa prebonding pressure. This study provides valuable insights for optimizing flip-chip bonding processes.