A Novel Anisotropic Conductive Film (ACF) Bonding Method Using Vertical Ultrasonic Vibration

In this study, a novel anisotropic conductive film (ACF) bonding method using vertical ultrasonic vibration was developed and demonstrated in flex-on-board applications. In terms of ultrasonic bonding processes, the relations between ACF temperature and ultrasonic variables were both experimentally and theoretically investigated. Considering the effects ultrasonic variables on ACF temperature, a novel ACF bonding equipment utilizing vertical ultrasonic vibration was newly developed in combination with a vision alignment system and pneumatic actuators without any external heat sources. ACF temperature was successfully controlled with a range from room temperature to above 250°C by adjusting ultrasonic vibration amplitude. The ACF temperature showed rapid heating rates and stable plateau regions within 2 sec with ±10°C temperature uniformity through the bonding area. Ultrasonic bonded ACF joints showed similar peel adhesion strengths and daisy-chain resistances as thermo- compression bonded ACF joints and showed stable resistances during 85°C/85 % RH test and 125°C high temperature storage test for 1000 hours, and -55°C/125°C thermal cycling test for 1000 cycles.