Research on Electroplating Bonding of Flip-Chip Under the Action of Additives

In the flip-chip interconnection technology, Cu–Cu bonding is one of the key technologies. Currently, the industry commonly uses hot-press bonding to achieve high-density Cu–Cu interconnection. However, this method requires high temperature, high pressure, and high vacuum environment, and the process conditions are relatively harsh. In the semiconductor manufacturing industry, electroplating technology is widely used, such as the preparation of copper column bumps, redistribution layers, and silicon vias, which often take place in a room temperature and low-pressure environment. This article proposes to use electroplating technology to achieve bonding interconnection between the chip and the copper substrate. First, the COMSOL is used to simulate and analyze the electroplating process between the chip and the board under the synergistic effect of the flow field and the accelerator and inhibitor. Then, electroplating bonding experiments were carried out, and the results showed that under the action of additives, the electroplating bonding showed a “from inside to outside” preference for deposition, which is consistent with the convection-dependent adsorption mechanism. Under strong convection conditions, most bump bonding can be achieved, and the morphology of the bonded bumps is good. The overall shear strength of the chip bump reaches 101.8 MPa, which has good process superiority and electromechanical reliability compared with tin-based solder bonding. At the same time, combined with the shear fracture surface diagram, it can be seen that the electroplating primarily deposits at the bottom of the copper pillar, indicating that more reliable interconnection technology can be achieved through optimization of the bonding process in the future.