Reliability of Fine-Pitch Flip-Chip (COG) Bonding with Non-Conductive Film Using Ultrasonic Energy

This study evaluated the reliability of fine-pitch, flip-chip bonding with ultrasonic energy and non-conductive film (NCF). The surface treatment was carried out with H2SO4 before flip-chip bonding (FCB). The electro-plated Cu bumps on the Si wafer and Cu-coated glass substrate were prepared for chip on glass (COG). The ultrasonic bonding was carried out, with and without NCF, under optimum bonding pressure and time. The mechanical properties were tested by die shear testing. The reliabilities of COG with and without NCF were evaluated with thermal shock testing, humidity and temperature (HT) testing, and high temperature storage (HTS) testing after FCB. The contact resistances of COG were evaluated for electrical reliability. To determine the variation in the initial value of the contact resistance of the flip-chip bumps according to the bonding method, the bonded interface of each sample was analyzed with scanning electron microscopy (SEM).