Method for manufacturing multilayer printed wiring board

A method for manufacturing a printed wiring board, comprising:

• preparing a core substrate having a first surface and a second surface on an opposite side of the first surface;
• forming on a first-surface side of the core substrate a first opening portion tapering from the first surface toward the second surface;
• forming on a second-surface side of the core substrate a second opening portion tapering from the second surface toward the first surface;
• forming a third opening portion such that a penetrating hole comprising the first opening portion, the second opening portion and the third opening portion connecting the first opening portion and the second opening portion is formed in the core substrate;
• forming a first conductor on the first surface of the core substrate;
• forming a second conductor on the second surface of the core substrate;
• and
• filling a conductive material in the penetrating hole such that a through-hole conductor connecting the first conductor and the second conductor is formed through the core substrate.