Electrodeposition, microstructure and characterization of high-strength, low-roughness copper foils with polyethylene glycol additives.

Electroplating additives play a key role in enhancing the physical and chemical performances of electrodeposited copper foils. Currently, a lot of research on polyethylene glycol (PEG) additives has been reported on the metallisation interconnections for printed circuit boards (PCBs); however, research on its applications for electrodeposited copper foils is rarely documented. Herein, high-quality copper foils with high tensile strength (433.2 MPa) and low surface roughness (Rz = 1.7 μm) were electrodeposited on titanium substrates with 4 mg L PEG. The characterization results showed that the copper foil possesses a high (220) crystal plane orientation and low twin layer thickness. Further analysis suggested that twin boundaries strengthened by stacking faults were the main reason for the high tensile strength of copper foils. Electrochemical behavioral studies indicated that PEG increased the cathodic polarization and improved the nucleation rate, thereby refining the copper foil grain size. The high (220) crystal plane orientation and high density of twin grain boundaries caused by the stacking faults strengthened the copper foil more than the fine-grain strengthening. This work offers theoretical guidance for modulating the properties of copper foil using PEG.