Patent ID: 8262769

Claim:
A method of detinning a Sn plating layer on a Cu-based material for recycling the Cu-based material on which the Sn plating layer including a Sn layer and/or a CuSn layer is formed, said method comprising: immersing the Cu-based material into an alkali hydroxide solution with a concentration of 3.0 to 37.5 mass % and adding a H 2 O 2 solution with a concentration of 3.0 to 50.0 mass % in the alkali hydroxide solution, wherein a temperature of the alkali hydroxide solution when the Cu-based material is immersed ranges from 60 to 105° C., wherein a ratio A/B between a mol number A of alkali hydroxide in the alkali hydroxide solution and a mol number B of H 2 O 2 in the H 2 O 2 solution is 10 or more, and wherein where a mol number of Sn in the Sn layer is C and a mol number of Sn in the CuSn layer is D, B≧C×2+D×6.