A surface treatment method for increasing adhesion of a surface of copper
foil to an insulating epoxy-impregnated substrate used in printed circuit
boards is provided. The method includes nodularizing a surface of an
electrolytic copper foil, surface-treating the surface of the nodularized
electrolytic copper foil by Zn--As alloy electrodeposition to form a
Zn--As composite layer thereon, and coating the surface of the
surface-treated electrolytic copper foil with a silane coupling agent
mixture, whose compounding ratio of 3-aminopropyltriethoxysilane with
respect to vinyltriethoxysilane is between 6:4 and 9:1. This method is
very effective to prevent discoloration of copper foil caused by oxidation
and the like.
