Optimization of Thermocompression Bonding Process for Fine-Pitch Flip-Chip Applications

With the trend towards miniaturization in the electronics packaging industry, solder joint sizes have been steadily decreasing and spacing has become increasingly dense, so narrow pitch flip-chip interconnects have attracted considerable research interest. To meet this challenge, flip-chip thermocompression bonding (TCB) has emerged as the dominant chip bonding technique. In this process, process parameters play a critical role in bond strength and reliability. However, traditional flip-chip underfill techniques, such as capillary underfill, tend to create voids in narrow-pitch interconnect applications, reducing product reliability. To address this issue, the industry has developed prefabricated underfill techniques specifically designed for narrow-pitch flip-chip interconnects, including non-conductive underfill and wafer-level underfill. This research, based on traditional flip-chip thermocompression bonding techniques, systematically investigates the effect of factors such as pressure, peak temperature, peak temperature duration and temperature ramp rate on the strength of the thermocompression bond. By optimizing these process parameters, we have identified a combination of techniques that improve bond strength.