3-((2-ethoxyethanethioyl)thio)propane-1-sodium sulfonate as a new accelerator for copper electroplating: Electrochemical and theoretical calculation studies

Superfilling of blind holes is essential for a high density interconnect printed circuit board (PCB), for which accelerators are essential for its high quality. However, the mechanical properties of copper obtained by electroplating with accelerators commonly used in industry still need to be further improved. It has been reported that 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid (DPS) can improve the copper crystal orientation and optimize the microstructure of copper plating by utilizing its CS bond. Based on this behavior, in this paper, 3-((2-ethoxyethanethioyl)thio)propane-1-sodium sulfonate (ETPS), an organic compound containing dithioester (─C(═S)─S─) special functional groups is proposed as a new accelerator for brightening coating. According to the experimental results, it is found that with ETPS as the accelerator, the superfilling of blind holes can be achieved with the reduced grain size and enhanced Cu (1 1 1) crystal surface for the copper electroplating layers; the copper microstructure with fine grains could contribute to improve the mechanical properties of copper plating. Molecular dynamics calculations have demonstrated that the inclusion of CS double bond can enhance the adsorption of ETPS on the surface of copper, leading to the accelerated deposition process of copper. This work will promote the research and development of new accelerators in the future.