Optical-electrical wiring board and optical module

1. An optical-electrical wiring board, comprising:

a substrate;

a dielectric layer disposed on a main face of the substrate, the dielectric layer comprising a first region and a second region, the dielectric layer configured to constitute a plurality of light transmission portions in the first region; and

a plurality of pairs of electrically conductive layers located at the second region, wherein

a plurality of overlap portions are provided in which conductive layers constituting each pair of the plurality of pairs of electrically conductive layers overlap each other, when viewed in a laminated direction of the dielectric layer and the substrate, the laminated direction being perpendicular to the main face of the substrate,

the dielectric layer further comprises a third region that is located such that the second region is disposed between the third region and the first region, and the plurality of overlap portions extend from the third region toward the first region, and

a distance between two adjacent overlap portions of the plurality of overlap portions increases as the two adjacent overlap portions approach a side of the first region, when viewed in the laminated direction.

2. The optical-electrical wiring board according to claim 1 , wherein a coefficient of thermal expansion of each conductive layer of the plurality of pairs of electrically conductive layers is lower than a coefficient of thermal expansion of the dielectric layer.

3. The optical-electrical wiring board according to claim 1 , wherein

each conductive layer of the plurality of pairs of electrically conductive layers has a longitudinal direction when seen through in the laminated direction, and

in a cross-section of the each conductive layer orthogonal to the longitudinal direction, a length of the each conductive layer in a width direction in contact with the dielectric layer is longer than a length thereof in the laminated direction.

4. The optical-electrical wiring board according to claim 1 , wherein the third region comprises a mount portion configured to mount an integrated circuit device thereon.

5. The optical-electrical wiring board according to claim 1 , wherein the plurality of overlap portions each comprises a plurality of straight line portions comprising mutually different longitudinal directions.

6. The optical-electrical wiring board according to claim 5 , wherein

the plurality of light transmission portions are located side by side in a first direction, and

the plurality of straight line portions each comprise:

a first straight line portion that is parallel to the first direction;

a second straight line portion that is inclined with respect to the first direction; and

a third straight line portion that is perpendicular to the first direction.

7. The optical-electrical wiring board according to claim 6 , wherein

the plurality of overlap portions comprise a first overlap portion and a second overlap portion, and

the first overlap portion is located farthest from a center of the integrated circuit device among the plurality of overlap portions, the second overlap portion is located closest to the center among the plurality of overlap portions, and a length of the first straight line portion in the first overlap portion is longer than a length of the first straight line portion in the second overlap portion.

8. The optical-electrical wiring board according to claim 1 , wherein

the plurality of pairs of electrically conductive layers comprise a plurality of first conductive layers, and a plurality of second conductive layers that are located such that the second region is clipped between the plurality of second conductive layers and the plurality of first conductive layers,

the plurality of first conductive layers are located between the substrate and the second region, and

the optical-electrical wiring board further comprises a plurality of through conductors that are electrically connected to both end portions of each of the plurality of first conductive layers and that are located so as to pass through both main faces of the dielectric layer.

9. An optical module, comprising:

the optical-electrical wiring board according to claim 1 ;

an integrated circuit device that is mounted on a mount portion of the optical-electrical wiring board and connected to the plurality of pairs of electrically conductive layers;

a plurality of photoelectric conversion elements that are each optically coupled to at least one of the plurality of light transmission portions; and

a plurality of drive circuit elements that are each electrically connected to at least one of the plurality of photoelectric conversion elements, and electrically connected to the integrated circuit device via at least one pair of the plurality of pairs of electrically conductive layers.