The Shape Control Process of a Cu/SnAg Solder Joint with a Ni insertion Using Thermo-Compression Bonding

With the trend of miniaturization of electronic products, the integration and performance requirements of microelectronic chip are continuously increasing. Under this background, three-dimensional integrated circuit (3D IC) technology has received more and more attention. Fine-pitch microbump solder joint, as the vital part of 3D IC, has received extensive attention and researches. However, there is still insufficient studies on the shape control technique of Cu-pillar-based solder joint and the correlation between joint shape and the microstructure of solder layer. Hence, in this paper, three types of solder joints with different shapes were fabricated using Thermo-compression bonding (TCB) combined with displacement control in the Z-axis. Two main bonding structures, Cu/Sn and Sn/Sn, were applied in the experiment. The TCB process condition and parameters for fabricating the general type solder joints were studied first, and the adverse effects of temperature distribution inhomogeneity of TCB process on bonding quality and subsequent shape control of solder joint were discussed. Finally, through the improvement of bonding recipe, including the adjustment of bonding temperature and movement order of bonding head, a good bonding quality for general type solder joint was obtained, and the accurate control of stretch and compression type solder joints was also achieved.