Device embedded substrate and manufacturing method of device embedded substrate

A method for manufacturing a device embedded substrate, comprising:

• a mounting step of bonding a metal film on a support plate having rigidity, and mounting an electric or electronic device on the metal film;
• a lay-up step of passing the device through a through perforation of a perforated insulator, the through perforation through which the device is passed being formed in advance, and disposing a non-perforated insulator, in which a sheet-shaped glass cloth is embedded, at a position for covering the through perforation;
• a lamination step of forming an insulation layer by pressing while heating the perforated insulator and the non-perforated insulator against each other, and embedding the device in the insulation layer;
• a via forming step of forming a via which reaches a terminal included in the device from an outer side of the insulation layer;
• and
• a pattern forming step of forming a conductor pattern on a surface of the insulation layer, and filling the via with a conductor for electrically connecting the conductor pattern with the terminal to form a conducting via;
• wherein
• in the lay-up step, the perforated insulator is formed from a fluid body having fluidity and a rigid body having rigidity, and a thickness of the fluid body is 30% to 90% of that of the perforated insulator, and wherein
• in the via forming step, after a large-diameter via having a large diameter and penetrating the glass cloth is formed, a small-diameter via having a diameter smaller than that of the large-diameter via is formed such that the small-diameter via reaches the terminal while forming a stepped section with respect to the large-diameter via.