Wiring substrate and manufacturing method for wiring substrate

1. A wiring substrate comprising:

a plate-like base material containing carbon fibers;

a wiring layer formed on a surface of the base material;

a first via including a first through hole penetrating through the base material, a first resin layer formed on an inner wall of the first through hole and including a second through hole, and a first conductive layer formed on an inner wall of the second through hole; and

a second via including a third through hole penetrating through the base material and a second conductive layer formed on an inner wall of the third through hole,

wherein an inside diameter of the third through hole is greater than an inside diameter of the second through hole,

wherein spaces inside the first conductive layer and the second conductive layer are filled with a resin, and

wherein the inside diameter of the third through hole is equal to an inside diameter of the first through hole.

2. The wiring substrate according to claim 1 ,

wherein the resin filling the spaces inside the first conductive layer and the second conductive layer has the same thermal expansion coefficient and the same elasticity modulus as those of the first resin layer.

3. A wiring substrate comprising:

a plate-like base material containing carbon fibers;

a wiring layer formed on a surface of the base material;

a first via including a first through hole penetrating through the base material, a first resin layer formed on an inner wall of the first through hole and including a second through hole, and a first conductive layer formed on an inner wall of the second through hole; and

a second via including a third through hole penetrating through the base material and a second conductive layer formed on an inner wall of the third through hole,

wherein an inside diameter of the third through hole is greater than an inside diameter of the second through hole,

wherein a second resin layer including a fourth through hole is formed on an inner wall of the second conductive layer, and an inside diameter of the fourth through hole is equal to the inside diameter of the second through hole.

4. The wiring substrate according to claim 3 ,

wherein the second resin layer has the same thermal expansion coefficient and the same elasticity modulus as those of the first resin layer.

5. A manufacturing method for a wiring substrate, comprising:

forming a first through hole having a first diameter in a carbon composite substrate;

filling the first through hole with a first resin;

forming a first conductive layer on upper and lower surfaces of the carbon composite substrate;

forming a second through hole having a second diameter less than the first diameter at a position of the carbon composite substrate filled with the first resin;

forming a third through hole having a diameter greater than the second diameter at a position of the carbon composite substrate not filled with the first resin;

forming a second conductive layer on an inner wall of the second and third through holes; and

partially removing the first conductive layer to form a wiring layer on the upper and lower surfaces of the carbon composite substrate,

wherein the forming the third through hole includes forming the third through hole, a diameter of which is greater than a diameter of the second through hole and equal to a diameter of the first through hole, and

the forming the second conductive layer is followed by filling a space inside the second conductive layer with a second resin.