CIRCUIT BOARD, METHOD FOR MANUFACTURING CIRCUIT BOARD, AND ELECTRONIC DEVICE

1 . A circuit board characterized in that

a plurality of laminates which include a first insulating substrate, a metal layer formed on a first surface of the first insulating substrate to have a pattern, a second insulating substrate stacked in a place of the first surface where the metal layer is not disposed so as to have a same thickness as the metal layer, a third insulating substrate stacked on a second surface at an opposite side to the first surface of the first insulating substrate, and a via formed from a surface at an opposite side to the first insulating substrate side of the third insulating substrate until the via reaches the metal layer, is stacked.

2 . The circuit board according to claim 1 characterized in that

the metal layer and the via are formed so as to decrease in cross-sectional area in a direction from the third insulating substrate toward the second insulating substrate.

3 . The circuit board according to claim 1 characterized in that

the second insulating substrate is formed of one of a photosensitive resin film and a photosensitive resin varnish.

4 . The circuit board according to claim 1 characterized in that

a surface at the second surface side in the metal layer is subjected to a surface roughening treatment so as to have an arithmetic average roughness (Ra) no lower than 1.0 μm and no higher than 2.0 μm.

5 . A method for manufacturing a circuit board characterized by comprising:

a first step of forming a laminate with a metal layer formation step of forming a metal layer on a first surface of a first insulating substrate to have a pattern, a first stacking step, as a subsequent step, of stacking a second insulating substrate to have a same thickness as the metal layer in a place of the first surface where the metal layer is not disposed, to expose a surface of the metal layer, a second stacking step, as a subsequent step, of stacking a third insulating substrate which is uncured and a resin film in this order on a second surface at an opposite side to the first surface of the first insulating substrate, a via formation step, as a subsequent step, of forming a via from a surface at an opposite side to the first insulating substrate side of the resin film until the via reaches the metal layer, and a separation step, as a subsequent step, of separating the resin film; and

a second step of stacking a plurality of the laminates.

6 . The method for manufacturing the circuit board according to claim 5 characterized by including

a surface roughening step, as a subsequent step to the first stacking step, of performing a surface roughening treatment on a surface at an opposite side to the first surface side in the metal layer to have an arithmetic average roughness (Ra) no lower than 1.0 μm and no higher than 2.0 μm.

7 . The method for manufacturing the circuit board according to claim 5 characterized in that

the second insulating substrate is formed of a photosensitive resin film, and

the first stacking step includes a step of attaching the photosensitive resin film so as to cover the metal layer from the first surface side, and a step of making the metal layer and the photosensitive resin film coplanar with each other.

8 . The method for manufacturing the circuit board according to claim 5 characterized in that

the second insulating substrate is formed of a photosensitive resin varnish, and

the first stacking step includes a step of printing the photosensitive resin varnish so as to cover the metal layer from the first surface side, and a step of making the metal layer and the photosensitive resin varnish coplanar with each other.

9 . An electronic device characterized by comprising:

the circuit board according to claim 1 ; and an electronic component.