Wiring board

1. A wiring board comprising:

an insulating layer,

an electrode located on the insulating layer, and

the electrode including:

a first conductor layer located on the surface of the insulating layer, and containing any one of nickel and chromium, a metal belonging to group 4 of the periodic table, or a metal belonging to group 6 of the periodic table,

a second conductor layer located inside away from the outer circumferential edge of the first conductor layer, and containing copper,

a third conductor layer located on the surface of the insulating layer in a state of covering the first conductor layer and the second conductor layer and containing nickel, and

a fourth conductor layer located in a state of covering the third conductor layer, and containing gold,

wherein the third conductor layer comprises an overhanging part extending outward from the outer circumferential edge of the first conductor layer and located to form a gap with the insulating layer, and the fourth conductor layer covers the third conductor layer containing the overhanging part, and is located in the gap and reaches to the insulating layer, and extends outward from the outer circumferential edge of the overhanging part.

2. The wiring board according to claim 1 , wherein the insulating layer has a via hole with a via land located at the bottom thereof, and the first conductor layer is located on the surface of the insulating layer around the opening of the via hole and inside the via hole.

3. The wiring board according to claim 1 , wherein, in plan view, a surface roughness of the insulating layer in which the overhanging part is located is greater than the surface roughness of the insulating layer in which the first conductor layer is located.

4. The wiring board according to claim 3 , wherein the surface roughness of the insulating layer in which the overhanging part is located is 0.05 to 0.2 μm, and the surface roughness of the insulating layer in which the first conductor layer is located is 0.02 to 0.1 μm.

5. The wiring board according to claim 1 , wherein the insulating layer comprises a core insulating layer and a build-up insulating layer located on the upper surface and the lower surface of the core insulating layer, and the electrode is located on one or both of the build-up insulating layer located on the upper surface and the lower surface of the core insulating layer.

6. The wiring board according to claim 1 , wherein an outermost surface of the third conductor layer is formed with a palladium film.

7. A wiring board comprising:

a core insulating layer,

a first electrode located on the upper surface of the an uppermost build-up insulating layer,

a second electrode located on the lower surface of the a lowermost build-up insulating layer, and

the first electrode including:

a first conductor layer located on the surface of the uppermost build-up insulating layer and containing any one of nickel and chromium, a metal belonging to group 4 of the periodic table, or a metal belonging to group 6 of the periodic table,

a second conductor layer located inside away from the outer circumferential edge on the first conductor layer and containing copper,

a third conductor layer located on the surface of the insulating layer in a state of covering the first conductor layer and the second conductor layer and containing nickel, and

a fourth conductor layer located in a state of covering the third conductor layer and containing gold,

wherein the third conductor layer comprises an overhanging part extending outward from the outer circumferential edge of the first conductor layer and located to form a gap with the insulating layer, and the fourth conductor layer covers the third conductor layer containing the overhanging part, and is located in the gap and reaches to the insulating layer, and extends outward from the outer circumferential edge of the overhanging part, and

wherein the second conductor layer is formed by depositing copper-plate metal on the lower surface of the lowermost build-up insulating layer.