Each wiring pattern is composed of a conductor layer and a tin plating layer, and includes a tip portion, a connection portion and a signal transmission portion. The width of the tip portion is equal to the width of the signal transmission portion, and the width of the connection portion is smaller than the widths of the tip portion and the signal transmission portion. The connection portions of wiring patterns and bumps of an electronic component are connected to one another, respectively, by heat-sealing when the electronic component is mounted. Respective distances A1, A2 are set to not less than 0.5 μm. Respective distances B1, B2 are set to not less than 20 μm. The thickness of the tin plating layer is set to not less than 0.07 μm and not more than 0.25 μm.