Effect of 1.10-Phenanthroline on Electroless Copper Plating Using Formaldehyde as Reductant

The effects of 1.10-phenanthroline on the utilization of formaldehyde and copper deposition behavior from electroless copper plating was studied by analyzing the content of formaldehyde in electrolyte in real-time, polarization curves, electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP). The morphology and microstructure of copper coating was observed by SEM and XRD. The results showed that 1.10-phenanthroline can accelerate the oxidation of formaldehyde and increase the utilization of formaldehyde. When 1.10-phenanthroline was added to electrolyte, the resistance of electrolyte reduces, the current density at mixed potential raises, the surface potential of copper at electrolyte moves negatively, and then the copper deposition rate increases. The utilization of formaldehyde raises from 28% to 39%, the deposition rate increases by 50% when 1.5 mg· L -1 1.10-phenanthroline was added to electrolyte. Besides, 1.10-phenanthroline is helpful to obtain uniform and fine copper coating, and increases the preferred orientation of Cu (111).