To provide a cross-sectional shape for a conductor foil where a resist (insulating film) can be applied uniformly to the surface of the conductor foil, without being affected by the surface tension of the resist.

Since two pieces of conductor foil 5 and 6 are formed to have hexagonal cross sections, curved surface, or semispherical cross sections, by eliminating corner sections 2b and 2c and 3b and 3c of the upper surface of foils 2 and 3 through etching treatment, etc., a resist 4 can be applied uniformly to the surface of the foil 2 and 3, and accordingly, the environmental resistance and insulation resistance of an electronic circuit board can be improved.