Printed wiring board and method for manufacturing the same

A method for manufacturing a printed wiring board, comprising:

• forming a conductor layer including a plurality of conductor pads on a base insulating layer;
• forming a solder resist layer on the base insulating layer such that the solder resist layer covers the conductor layer;
• forming, in the solder resist layer, a plurality of openings such that the plurality of openings exposes the plurality of conductor pads, respectively;
• forming a plurality of plating bumps on the plurality of conductor pads such that each of the plating bumps includes a base plating layer and a top plating layer;
• roughening a portion of a side surface of the base plating layer protruding from the solder resist layer such that the portion of the side surface has a rough surface before reflowing the top plating layer;
• and
• reflowing the top plating layer of each of the plating bumps formed on the plurality of conductor pads after the portion of the side surface of the base plating layer is roughened,
• wherein the forming of the plating bumps includes forming, in a respective one of the openings of the solder resist layer, the base plating layer having an upper surface and the side surface including the portion protruding from the solder resist layer, and forming the top plating layer on the base plating layer, the forming of the plating bumps includes forming an intermediate layer between the base plating layer and the top plating layer, and the forming of the intermediate layer includes forming an edge portion protruding from the side surface of the base plating layer.