Printed wiring board

A printed wiring board, comprising:

• a first conductor layer;
• a resin insulating layer formed on the first conductor layer;
• a second conductor layer formed on a surface of the resin insulating layer;
• and
• a via conductor formed in an opening formed in the resin insulating layer such that the via conductor is connecting the first conductor layer and the second conductor layer,
• wherein the second conductor layer and the via conductor include a seed layer and an electrolytic plating layer formed on the seed layer such that the seed layer has a first portion formed on the surface of the resin insulating layer, a second portion formed on an inner wall surface of the resin insulating layer in the opening, and a third portion formed on the first conductor layer exposed from the opening and that the first portion has a thickness that is greater than a thickness of the second portion and a thickness of the third portion, the seed layer is formed such that the second portion has a thickness that is greater than a thickness of the third portion, and the seed layer has a first layer and a second layer formed on the first layer such that the first portion of the first layer has a thickness that is greater than a thickness of the second portion of the first layer and a thickness of the third portion of the first layer and that the first portion of the second layer has a thickness that is greater than a thickness of the second portion of the second layer and a thickness of the third portion of the second layer.