Synthesis and application of isoindigo quaternary ammonium salts in copper plating

Achieving uniform through-hole filling by copper electrodeposition is important for the fabrication of printed circuit boards (PCBs), and the development of suitable additives is a key process to realize efficient electrodeposition. Five isoindigo (IID) quaternary ammonium salts were synthesized using isoindigo molecules as the core skeleton. Electrochemical tests, theoretical calculations, and molecular dynamics simulations demonstrated that the isoindigo derivatives have the ability to act as leveler and exhibit electrode absorption capacity, among which IID-C4-QL showed the best inhibition of copper deposition as well as the best cathodic adsorption ability. The high through-hole filling and excellent leveling performance of IID-C4-QL were confirmed by actual electroplating tests.