CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims the benefit of priority to Japanese Patent Application No. 2019-222582, filed Dec. 10, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a printed wiring board having metal posts, and a method for manufacturing the printed wiring board having the metal posts.

Description of Background Art

Japanese Patent Application Laid-Open Publication No. 2017-50315 describes a printed wiring board having metal posts. The entire contents of this publication are incorporated herein by reference.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a printed wiring board includes a conductor layer, an outermost resin insulating layer having a first surface and a second surface on the opposite side with respect to the first surface and laminated on the conductor layer such that the second surface faces the conductor layer, and metal posts formed in the outermost resin insulating layer such that the metal posts are penetrating through the outermost resin insulating layer and reaching the conductor layer. The metal posts include first metal posts and second metal posts such that each of the first metal posts has a first upper surface positioned above the first surface of the outermost resin insulating layer and having an entirely flat surface and that each of the second metal posts has a second upper surface positioned above the first surface of the outermost resin insulating layer and having a partly flat surface.

According to another aspect of the present invention, a method for manufacturing a printed wiring board includes forming a conductor layer, forming on the conductor layer an outermost resin insulating layer having a first surface and a second surface on the opposite side with respect to the first surface such that the second surface of the outermost resin insulating layer faces the conductor layer, forming openings in the outermost resin insulating layer such that the openings penetrate through the outermost resin insulating layer and reach the conductor layer, forming metal posts in the openings formed in the outermost resin insulating layer, respectively, and polishing the metal posts such that a height of each of the metal posts is reduced. The forming of the metal posts includes forming first metal posts and forming second metal posts, and the reducing includes forming the first metal posts such that each of the first metal posts has a first upper surface positioned above the first surface of the outermost resin insulating layer and having an entirely flat surface and forming the second metal posts such that each of the second metal posts has a second upper surface positioned above the first surface of the outermost resin insulating layer and having a partly flat surface.

