Printed wiring board and method of manufacturing printed wiring board

A printed wiring board comprising:

• a substrate including a planar insulating layer having a through hole in a thickness direction of the planar insulating layer;
• and
• a via comprising a conductive material that fills the through hole, the via having a first filled portion of the conductive material in at least a central portion of the through hole, a second filled portion of the conductive material in a region of the through hole that is not filled by the first filled portion, and an interface between the second filled portion and the first filled portion, or between the second filled portion and the planar insulating layer,
• wherein the first filled portion has a shape of a conical frustum having a conical surface that is inclined in the thickness direction so as to taper from a first surface of the planar insulating layer toward a second surface of the planar insulating layer that is opposite to the first surface,
• wherein the first filled portion has an upper base surface that is parallel to the second surface and the conical surface,
• wherein the second filled portion is in contact with the upper base surface and the conical surface of the first filled portion, and
• wherein a first surface diameter of the through hole on the first surface is larger than a second surface diameter of the through hole on the second surface.