Wiring board and mounting structure thereof

1. A wiring board, comprising:

an inorganic insulating layer provided with a penetrating hole; and

a penetrating conductor disposed inside the penetrating hole,

wherein the inorganic insulating layer includes first inorganic insulating particles connected to each other and second inorganic insulating particles that are larger in particle size than the first inorganic insulating particles and are connected to each other via the first inorganic insulating particles, the inorganic insulating layer having, at an inner wall of the penetrating hole, a protrusion including at least part of the second inorganic insulating particle, and

the protrusion is covered with the penetrating conductor.

2. The wiring board according to claim 1 , further comprising:

a resin layer disposed on the inorganic insulating layer,

wherein the penetrating hole passes through both the inorganic insulating layer and the resin layer, and includes a first penetrating portion located in the inorganic insulating layer and a second penetrating portion located in the resin layer, and

wherein a ten-point average roughness of the inner wall of the first penetrating portion is greater than a ten-point average roughness of the inner wall of the second penetrating portion.

3. The wiring board according to claim 1 , further comprising:

a resin layer disposed on the inorganic insulating layer,

wherein the penetrating hole passes through both the inorganic insulating layer and the resin layer, is so shaped that its diameter becomes smaller from a inorganic insulating layer side toward a resin layer side, and includes a first penetrating portion located in the inorganic insulating layer and a second penetrating portion located in the resin layer, and

wherein an inclination angle of the inner wall of the first penetrating portion relative to a penetrating direction of the penetrating hole is greater than an inclination angle of the inner wall of the second penetrating portion relative to the penetrating direction.

4. The wiring board according to claim 1 ,

wherein a ten-point average roughness of the inner wall of the penetrating hole of the inorganic insulating layer is greater than a ten-point average roughness of a main surface of the inorganic insulating layer.

5. The wiring board according to claim 1 ,

wherein the inorganic insulating layer has, at the inner wall of the penetrating hole, a recess which is created as a result of separation of the second inorganic insulating particle, at least part of which is buried in the inorganic insulating layer, from the inorganic insulating layer, and

wherein the recess is filled with part of the penetrating conductor.

6. The wiring board according to claim 1 ,

wherein the second inorganic insulating particle has a spherical shape.

7. The wiring board according to claim 1 ,

wherein the first inorganic insulating particles have a particle size of not less than 3 nm and not more than 110 nm, and

wherein the second inorganic insulating particles have a particle size of not less than 0.5 μm and not more than 5 μm.

8. The wiring board according to claim 1 ,

wherein the inorganic insulating layer is made of silicon oxide, and

wherein the penetrating conductor is made of copper.

9. A mounting structure, comprising:

the wiring board according to claim 1 ; and

an electronic component mounted on the wiring board and electrically connected to the penetrating conductor.