Substrate for printed wiring board and printed wiring board

A printed wiring board comprising:

• a base film having a first main surface and a second main surface;
• a first wiring line having a first conductive layer disposed on the first main surface,
• a first electroless copper plating layer disposed on the first conductive layer, and a first electrolytic copper plating layer disposed on the first electroless copper plating layer;
• a second wiring line having a second conductive layer disposed on the second main surface, a second electroless copper plating layer disposed on the second conductive layer, and a second electrolytic copper plating layer disposed on the second electroless copper plating layer;
• a third electroless copper plating layer;
• and
• a third electrolytic copper plating layer,
• wherein, in the base film, a through hole extending through the base film along a thickness direction of the base film is formed,
• the third electroless copper plating layer is disposed on an inner wall surface of the through hole,
• the third electrolytic copper plating layer is disposed on the third electroless copper plating layer,
• the first wiring line is electrically connected to the second wiring line by the third electroless copper plating layer and the third electrolytic copper plating layer, and
• an amount of palladium in the base film at each of the first main surface and the second main surface is smaller than an amount of palladium in the base film at the inner wall surface.