Method of tin-plating copper alloy for electric or electronic parts and automobile parts and tin-plating material of copper alloy manufactured therefrom

A method for plating tin on a copper alloy for an electric or electronic part or automobile part, the method comprising:

• (a) electrolytic-degreasing and pickling a copper alloy base material;
• (b) plating an underlying copper layer on the copper alloy base material;
• (c) plating a tin or tin alloy layer on the underlying copper layer;
• (d) surface-treating the tin or tin alloy layer by mist-spraying a surface-treatment agent thereon to form a product;
• and
• (e) reflow-treating the product, wherein the reflow-treatment includes performing a first heat treating of the product at a temperature of 200 to 250° C. for 1 to 30 seconds, then a second heat treating of the product at a temperature of 300 to 700° C. for 3 to 1200 seconds,
• wherein an EBDS analysis of a resulting product shows that:
• a fraction in a crystal direction of <2-1-10>∥[001] of a Cu—Sn compound (Cu6Sn5) is in a range of 10 to 60%;
• a fraction in a crystal direction of <123>∥[001] of the Sn or Sn alloy layer is in a range of 10 to 60%;
• and
• a fraction in a crystal direction of <014>∥[001] of the Sn or Sn alloy layer is lower than or equal to 10%, and
• wherein a carbon (C), phosphorus (P), and oxygen (O) compound is present on a surface of the tin or tin alloy plated layer, wherein a relation between C, P, and O is 0.5<(C+P)/O<2.5.