Improving reliability of lateral thermosonic flip-chip bonding with ACF

For interconnection of liquid crystal display (LCD) driver IC, in this paper, thermosonic (TS) flip chip bonding technique which utilizes a lateral ultrasonic vibration as an additional heat source is considered. Larger amplitude of vibration produces more heat energy, which would accelerate the curing process of epoxy. In order to avoid potential problems due to large vibration amplitude such as misalignment between bump and pad, and the plastic deformation of epoxy resin, the viscoelastic characteristics of ACF epoxy are investigated. Based on experimental results, a useful guideline to determine the vibration amplitude is newly proposed. Moreover, the experimental results clearly show the relationship between curing degree and reliable amplitude range of vibration.