| CPC H01G 4/008 (2013.01) [H01G 4/33 (2013.01)] | 6 Claims | 

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               1. A method of preparing an electrolytic nickel foil for a thin film capacitor, on at least one surface thereof, a flat surface having an arithmetic average roughness (Ra) of 0.05 μm or less, a ten-point average roughness (Rz) of 0.20 μm or less, a maximum protrusion height (Rt) of 0.50 μm or less, and a 60° specular gloss of 200 GU or more, 
            wherein the method comprises performing electrolytic plating with an electrolyte including 400 to 600 g/L of a nickel ion precursor, 10 to 30 g/L of a pH buffer, and 0.5 to 2.0 g/L of a roughness controlling agent and having a pH of 1 to 5, and 
                wherein the roughness controlling agent comprises saccharin and sodium allyl sulfonate, and 
                the concentration ratio of saccharin and sodium allyl sulfonate is 1:0.05 to 1:20. 
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