Process for producing tinned copper wires

A process for producing a tinned copper wire, comprising:

• subjecting a copper wire sequentially to activation treatment, a first hot tinning treatment, a first cooling, a second hot tinning treatment, and a second cooling to obtain a tinned copper wire,
• wherein:
• the first hot tinning treatment is carried out in a first molten tin liquid at a first temperature;
• the second hot tinning treatment is carried out in a second molten tin liquid at a second temperature;
• the first temperature is higher than the second temperature;
• the first temperature is at least 38° C. higher than the melting point of tin;
• and
• the second temperature is at least 8° C. higher than the melting point of tin;
• wherein the first temperature is 320° C., and wherein the second temperature is 245° C.;
• the second molten tin liquid for the second hot tinning treatment comprises a rare metal in an amount of 0.08 wt %, and the rare metal is composed of indium, bismuth and nickel at a mass ratio of 1:1:1;
• the first hot tinning treatment is carried out with the first molten tin liquid comprising copper contamination from the copper wire in an amount of zero wt % to 2.0 wt %, and wherein the second hot tinning treatment is carried out with the second molten tin liquid comprising copper contamination from the copper wire in an amount of zero wt % to 0.7 wt %
• the first molten tin liquid for the first hot tinning treatment comprises phosphorus in an amount of 0.1 wt %.