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 including a conductor circuit such that the conductor circuit includes a signal wiring;
• 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 layer and a second layer formed on the first layer, that the first layer has a width that is greater than a width of the second layer in a cross section of the conductor circuit in the second conductor layer and that the electrolytic plating layer has a width that is greater than the width of the first layer in the cross section of the conductor circuit in the second conductor layer, and the second conductor layer includes a plurality of conductor circuits such that the plurality of conductor circuits includes the conductor circuit including the signal wiring and a conductor circuit other than a signal wiring.