The effect of introducing –SO2 fragments into the structure of polydimethyldiallylammonium (PD) on through-hole copper plating performance: A theoretical and experimental study

In this study, SO 2 was used to chemically modify the commonly used leveling agent polydimethyldiallylammonium (PD) in through-hole electroplating, resulting in a more effective leveling agent, PDS, which improved the throwing power (TP), leading to through-hole circuit boards with better metal coverage in difficult-to-reach areas. Furthermore, theoretical and experimental studies were conducted to understand how the −SO 2 structure influences the leveling ability of the leveling agent. The study demonstrates that the −SO 2 -modified additive significantly enhances the copper plating process, resulting in thicker and more uniform deposits in through-holes, which are critical for ensuring high-quality circuit boards.Additionally, this study elucidates the mechanism of action of the leveling agent on the copper surface, providing theoretical support for the development of copper plating leveling agents. The leveling ability differences between the leveling agents PD and PDS were investigated using Cyclic Voltammetry, constant current method, and Electrochemical Impedance Spectroscopy. Additionally, the optimal concentrations of the additives were determined. Quantum chemical calculations were employed to analyze the electrostatic potential, HOMO/LUMO orbitals, and differential charge density on the Cu (111) surface for both leveling agents. These theoretical analyses provided insights into the reasons behind the differing leveling abilities of the two agents.