Patent ID: 11503709

Abstract:
A printed wiring board includes resin insulating layers including an outermost resin insulating layer, conductor layers laminated on the resin insulating layers, a copper layer formed in the outermost insulating layer, and metal bumps formed on the copper layer such that the bumps have upper surfaces protruding from the outermost insulating layer and that each metal bump includes Ni film, Pd film and Au film. The copper layer is reduced in diameter toward upper surface side such that the copper layer has upper and bottom surfaces and each upper surface has diameter that is smaller than diameter of each bottom surface, the outermost insulating layer has cylindrical sidewalls formed such that at least part of the copper layer is not in contact with the sidewalls, and the bumps are formed such that the Ni film is filling spaces between the copper layer and the sidewalls of the outermost insulating layer.