Method for manufacturing printed wiring board and printed wiring board

A printed wiring board, comprising:

• a single insulating layer comprising an insulative resin base material and having a first surface and a second surface opposite the first surface;
• first and second conductive circuits embedded in the first surface and the second surface of the insulative resin base material respectively;
• a filled via comprising:
• an electroless plated film formed on an inner wall of a via opening that reaches from the second surface of the single insulating layer to the first conductive circuit embedded in the first surface of the single insulating layer, and
• an electrolytic plated film filled in the via opening having the electroless plated film;
• a first solder resist layer formed on the first surface and the first conductive circuit, the first solder resist layer having a first opening which exposes the first conductive circuit which is connected to the filled via;
• a second solder resist layer formed on the second surface and the second conductive circuit, the second solder resist layer having a second opening which exposes the filled via;
• a first solder bump formed on the first conductor circuit which is exposed from the first opening in the first solder resist layer;
• and
• a second solder bump formed on the filled via which is exposed from the second opening in the second solder resist layer such that the filled via is sandwiched between the first and second solder bumps.