Experimental analysis of pinhole on electrolytic copper foil and its prevention

Pinhole is one of the major defects of copper foils, which affects both of the mechanical performances and the physical properties greatly. It was deduced that the pinholes were formed because the lead anode dissolved in CuSO₄-H₂SO₄ electrolyte. In this paper, the copper foil samples were electrodeposited on a titanium cathode and a lead anode in CuSO₄-H₂SO₄ electrolyte system with different additions of the suspended state lead sulfate (PbSO₄) and hydroxyethyl cellulose (HEC), in which the other electro-deposition parameters were according with the manufacture line. The results show that PbSO₄ in electrolyte is the reason leading to pinhole formation on copper foils. The addition of HEC in the electrolyte can prevent the formation of pinhole and promote fine crystallization, accordingly it improves the mechanical properties of copper foil.