Electrochemical behavior of through-hole electrodeposition inhibitor EO-PO under periodic pulse reverse

Uniform electrodeposition of through-hole (TH) with a high aspect ratio is the key to the reliability of printed circuit board (PCB) interconnection. Inhibitors produce stronger inhibition at high potentials during TH electrodeposition and thus reduce the difference in electrodeposition rates between inside and outside the TH. In this paper, the electrochemical behavior of an ethylene oxide propylene oxide random copolymer (EO-PO) as an inhibitor on the cathode during periodic pulse reverse (PPR) electrodeposition was systematically studied. The results show that EO-PO will rotate under the effect of reverse pulse, and adsorb more strongly on the cathode surface, which inhibits the "cathode stripping" process of the reverse pulse. Through the electrodeposition experiments, compared with direct current (DC) electrodeposition, the PPR method effectively eliminates the copper nodule and improves the concentration window of EO-PO. The results pave the way for regulating and controlling TH electrodeposition with other additives.