1-(2-Pyridylazo)-2-naphthol as a synergistic additive for improving throwing power of through hole copper electronic electroplating

In this work, we develop a novel 1-(2-Pyridylazo)-2-naphthol (PAN)-based acidic sulfate copper electronic electroplating process for compact, homogeneous and conformal copper thickening of through hole (TH). The adsorption characteristics, electrochemical properties and the interaction mechanisms of three additives (PEG, SPS and PAN) are studied in detail. Scanning electron microscope (SEM) and optical microscope (OM) reveal that PAN can make the copper coating in fine grains and high throwing power of 90.35% in TH without an overhang phenomenon. Theoretical calculations illustrate that the binding energies between additive molecules and copper surface decrease in the order: PAN > SPS > PEG. Cyclic voltammetry experiments at rotating rates of 1200 and 200 r/min prove that PAN itself can accelerate and weakly suppress copper electrodeposition at the center and mouth of TH, respectively. PAN behaves respectively the synergistic and antagonistic effects with PEG at the mouth and center of TH, and the weakly synergistic effects with SPS both at the mouth and center of TH. The addition of PAN to the virgin make-up solution (VMS) containing PEG and SPS causes decreasing the relative electric charge (ΔQ) at high and low rotating rates from 18.52 ± 0.08% to 8.25 ± 0.05%, which satisfies the closer copper electronic electroplating rate at the center and mouth of TH. The effective and complicated synergistic effects of the additives PEG, SPS and PAN can achieve compact, homogeneous and conformal copper thickening of TH.