Modeling and numerical study of thermal-compression bonding in the packaging process using NCA

Packaging technology used in liquid crystal displays (LCDs) faces the critical issues such as high density interconnects, thinner packaging size, and environmental safety. In order to reduce the packaging size, driver integrated circuit (IC) chips are directly attached to LCD panels using flip chip technology with adhesives, which is called chip on glass (COG) packaging processes. To investigate the effects of the bonding force and bonding temperature on the flip chip thermal-compression packaging, this study established a compression model to analyze the flip chip packaging processes with non-conductive adhesives (NCAs). The plastic deformation of bumps and the NCA flow dynamics between chip and substrate were taken into account in this model. The gap height, bump deformation, bump contact area, and residual stresses after bonding can be estimated with this model.According to the simulation in this work, the best tactic for the flip chip packaging process using NCA is bonded at a lower temperature. This reduces the maximum warpage and only slightly decreases the average compressive residual stress in the bottom of bumps. A larger bonding force results in a larger bump contact area with the substrate, but has a lower compressive residual stress at the contact areas. The bonding force during the flip chip thermal bonding process will affect the contact resistance and reliability of packaging at the same time.