Effect of electrolyte compositions on the physical property and surface morphology of copper foil

This study examined the effect of copper and sulfuric acid concentrations on the surface morphology and physical properties of copper plated on a polyimide (PI) film. Electrochemical experiments with SEM and a four-point probe were performed to characterize the morphology and mechanical characteristics of copper electrodeposited in the composition of an electrolyte. The resistivity and peel strength were controlled using a range of electrolyte compositions. A lower resistivity and high flexibility were obtained when an electrolyte with 20 g/l of copper was used. However, a uniform surface was obtained when a high current density that exceeded 20 mA/cm² was applied, which was maintained at copper concentrations exceeding 40 g/l. Increasing sulfuric acid to > 150 g/l decreased the peel strength and flexibility. The lowest resistivity and fine adhesion were detected at a Cu₂₊: H ₂SO₄ ratio of 50:100 g/l.