CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims the benefit of priority to Japanese Patent Application No. 2019-081006, filed Apr. 22, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an inductor built-in substrate that has an inductor built therein.

Description of Background Art

Japanese Patent Application Laid-Open Publication No. 2016-197624 describes a method for manufacturing an inductor component built in a wiring substrate. The entire contents of this publication are incorporated herein by reference.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an inductor built-in substrate includes a core substrate having openings, a magnetic resin filled in the openings and having through holes, and through-hole conductors formed in the through holes respectively such that each of the through-hole conductors includes a metal film. The magnetic resin is formed such that each of the through holes has an angle part having an obtuse angle formed by an upper surface of the magnetic resin and a side wall of a respective one of the through holes.

According to another aspect of the present invention, a method for manufacturing an inductor built-in substrate includes preparing a core substrate including a resin substrate and a metal foil laminated on the resin substrate, forming openings in the core substrate, filling a magnetic resin in the openings formed in the core substrate, forming through holes in the magnetic resin, and forming a plating film on the core substrate, on a surface of the magnetic resin, and in the through holes. The filling of the magnetic resin includes polishing an upper surface of the magnetic resin in each of the openings such that a central portion of the upper surface of the magnetic resin in each of the openings is recessed relative to a peripheral portion of the upper surface of the magnetic resin in each of the openings.

