Wiring board

A wiring board comprising:

• a first interconnect layer;
• an insulating layer covering an upper surface and a side surface of the first interconnect layer;
• a via hole penetrating the insulating layer and reaching an upper surface of the first interconnect layer;
• a second interconnect layer filling the via hole and extending on an upper surface of the insulating layer;
• and
• a cavity provided in the first interconnect layer, recessed from the upper surface toward a lower surface of the first interconnect layer and communicating with the via hole, and extending to an outer peripheral side than a lower end of an inner side surface of the via hole in a plan view, wherein
• the second interconnect layer includes:
• a first seed layer provided on the upper surface of the insulating layer;
• a second seed layer continuously covering an upper surface and an inner side surface of the first seed layer, the inner side surface of the via hole, a surface of the insulating layer exposed inside the cavity, and a surface of the first interconnect layer exposed inside the cavity;
• and
• an electrolytic plating layer provided on the second seed layer, and
• the first seed layer is thinner than the second seed layer.