Low temperature camera module assembly using acrylic-based solder ACFs with ultrasonic-assisted thermo-compression bonding method

In this study, in order to improve thermal stability and reliability of camera module assembly for high yield rate, the camera module assembly using low temperature curable acrylic solder ACFs with ultrasonic-assisted thermo-compression (TC) bonding has been introduced. In general, the acrylic-based ACFs are cured at lower bonding temperature than conventionally used epoxy-based ACFs. And, the recently adopted ultrasonic-assisted TC bonding utilizes ultrasonic vibration during vertical thermo-compression to break solder oxide layers. Bonded solder ACF joints of camera modules for this study were investigated in terms of curing behavior, peel adhesion strength, and solder wetting. In addition, thermal stability of internal camera module assembly at this bonding condition was also investigated. According to the experiment results, acrylic-based solder ACF joints showed peel adhesion strength above recommendation with full degree of cure and excellent solder wetting on the electrodes at the low bonding temperature of 150°C and the ultrasonic amplitude of 6 μm. At the bonding temperature of 150°C, the internal temperature of a camera module was about 110°C which was lower than 137°C, the glass transition temperature of the lens. Therefore, the low temperature curable acrylic-solder ACFs with ultrasonic-assisted TC bonding is appropriate for the camera modules, since the ACFs were optimized in terms of degree of cure, peel adhesion strength and solder wetting and the camera modules were thermally stable at the low bonding temperature of 150°C.