The invention relates to a black surface treatment process of an electrolytic
copper foil, belonging to the technical field of production processes of high and precision electrolytic
copper foils. The black surface treatment process of an electrolytic
copper foil is characterized in that a VLP (Very Low Profile) electrolytic
copper foil of 8-12 mu m is used as an
electrode, and then copper or
copper alloy is roughened, solidified, weakly roughened and electrically deposited at a running speed of 25.0+ / -0.1m / min; a layer of nano-scale
nickel or
cobalt alloy and a layer of nano-scale
zinc alloy are sequentially and electrically deposited; and then alkaline chromate
passivation is carried out and a layer of
coupling agent is coated. In the invention, the black
copper foil for an FPC (Flexible Printing Circuit) is obtained by carrying out a series of special surface treatments on the ultrathin and VLP electrolytic
copper foil of 8-12 mu m, wherein the
surface roughness Ra of the obtained copper foil is smaller than or equal to 0.30 mu m, Rz is smaller than or equal to 2.5 mu m; the thickness of the copper foil subjected to the surface treatments is increased by 1.40-1.80 mu m; the copper foil does not contain elements having serious damages to the
human body, such as lead, mercury,
cadmium, stibium, and the like and has excellent
oxidation resistance as well as
corrosion and
etching resistance; the peel strength of the copper foil on a PI (
Polyimide) film reaches higher than 1.0N / mm, and the folding strength on the PI film reach more than 100 thousand numbers of times; the copper foil has good appearance characteristics after the copper foil is microetched, and after the copper foil is made into an FCCL (Flexible
Copper Clad Laminate), the copper foil has similar appearance characteristics to a rolled copper foil; and the properties of the copper foil product are equivalent to that of an electrolytic copper foil with the same specification for the FCCL.