Simulation study on the influences of the bonding parameters on the warpage of chip-on-glass module with nonconductive film

Abstract

Nonconductive film (NCF) interconnection technology is now being used for the ultrafine pitch interconnections in chip-on-glass (COG) packaging. In comparison to traditional anisotropic conductive film (ACF) technology, NCF can reach less than 10μm ultrafine pitch interconnection, while ACF just reaches the limit of 30μm. For NCF interconnection technology used in COG bonding, it needs a higher bonding pressure and temperature than those in ACF bonding, so the warpage is very important for the reliability of the package. In this paper, an exploring study investigated the effects of the structure design and bonding process on the warpage in a COG module. The warpage increased linearly with the increase in bonding head temperature and bonding force, but it decreased with the increase in substrate temperature, substrate thickness, and chip thickness. The large temperature difference between the substrate and chip produced a high thermal stress, and the large bonding force generated a high mechanical stress. The thermal and mechanical stresses were the reasons for warpage in a COG module. For the high reliability, the design and bonding process to the COG module with NCF should adopt a thick substrate, an appropriate bonding force, and a low temperature difference.