Wiring board, laminated wiring board, and semiconductor device

1. A wiring board comprising:

a first interconnect layer;

a first insulating layer covering the first interconnect layer;

a second interconnect layer, thinner than the first interconnect layer, formed on a first surface of the first insulating layer, the second interconnect layer having an interconnect density higher than an interconnect density of the first interconnect layer;

a second insulating layer, formed on the first surface of the first insulating layer, and covering the second interconnect layer; and

a third interconnect layer,

wherein the first insulating layer includes a first layer including no reinforcing material and covering the first interconnect layer, and a second layer including a reinforcing material and laminated directly on the first layer,

wherein the third interconnect layer integrally penetrates the first layer and the second layer and electrically connects the first interconnect layer and the second interconnect layer,

wherein the first layer and the second layer respectively include a non-photosensitive thermosetting resin as a main component thereof,

wherein the first layer has a coefficient of thermal expansion higher than a coefficient of thermal expansion of the second layer,

wherein the second insulating layer includes a photosensitive resin as a main component thereof, and

wherein the second interconnect layer includes an interconnect formed directly on the first surface of the first insulating layer and electrically connected to the first interconnect layer.

2. The wiring board as claimed in claim 1 , wherein

the first insulating layer includes a third layer laminated on the second layer and including no reinforcing material, and

the third layer includes a non-photosensitive thermosetting resin as a main component thereof, and has a rigidity lower than a rigidity of the first layer.

3. The wiring board as claimed in claim 2 , wherein

the third layer includes, as the main component thereof, the non-photosensitive thermosetting resin identical to that forming the main component of the first layer, and

the third layer is thinner than the first layer.

4. The wiring board as claimed in claim 1 , wherein one surface, located on a side closer to the first insulating layer, and side surfaces of the first interconnect layer, are covered by the first layer.

5. The wiring board as claimed in claim 1 , wherein the first surface of the first insulating layer is smoother than a second surface of the first insulating layer opposite to the first surface of the first insulating layer.

6. The wiring board as claimed in claim 5 , further comprising:

a fourth interconnect layer, thinner than the first interconnect layer, formed on a first surface of the second insulating layer, the fourth interconnect layer having an interconnect density higher than the interconnect density of the first interconnect layer; and

a third insulating layer, formed on the first surface of the second insulating layer, and covering the fourth interconnect layer,

wherein the third insulating layer includes a photosensitive resin as a main component thereof, and

wherein the first surface of the second insulating layer is smoother than the first surface of the first insulating layer.

7. The wiring board as claimed in claim 1 , wherein

the third interconnect layer is a via interconnect embedded in the first insulating layer and filling a via hole that penetrates the first layer and the second layer of the first insulating layer,

one end face of the via interconnect is exposed from the first surface of the first insulating layer and is directly connected to the second interconnect layer, and

the other end face of the via interconnect is directly connected to the first interconnect layer inside the first insulating layer.

8. The wiring board as claimed in claim 1 , wherein

the first interconnect layer is an external connection terminal, and

one surface of the first interconnect layer is exposed from one surface of the first layer.

9. The wiring board as claimed in claim 8 , further comprising:

a solder layer formed on the one surface of the first interconnect layer; and

a bonding layer, formed on the one surface of the first layer, and covering the solder layer.

10. A laminated wiring board comprising:

a base board; and

the wiring board according to claim 1 , mounted on the base board,

wherein the first interconnect layer and an external connection terminal of the base board are connected.

11. The laminated wiring board as claimed in claim 10 , wherein

the first insulating layer of the wiring board includes a third layer laminated on the second layer and including no reinforcing material, and

the third layer includes a non-photosensitive thermosetting resin as a main component thereof, and has a rigidity lower than a rigidity of the first layer.

12. The laminated wiring board as claimed in claim 11 , wherein

the third layer includes, as the main component thereof, the non-photosensitive thermosetting resin identical to that forming the main component of the first layer, and

the third layer is thinner than the first layer.

13. The laminated wiring board as claimed in claim 10 , wherein one surface, located on a side closer to the first insulating layer, and side surfaces of the first interconnect layer of the wiring board, are covered by the first layer.

14. The laminated wiring board as claimed in claim 10 , wherein the first surface of the first insulating layer of the wiring board is smoother than a second surface of the first insulating layer opposite to the first surface of the first insulating layer.

15. A semiconductor device comprising:

the laminated wiring board according to claim 10 ; and

a semiconductor chip mounted on the wiring board of the laminated wiring board.

16. The semiconductor device as claimed in claim 15 , wherein

the first insulating layer of the wiring board includes a third layer laminated on the second layer and including no reinforcing material, and

the third layer includes a non-photosensitive thermosetting resin as a main component thereof, and has a rigidity lower than a rigidity of the first layer.

17. The semiconductor device as claimed in claim 16 , wherein

the third layer includes, as the main component thereof, the non-photosensitive thermosetting resin identical to that forming the main component of the first layer, and

the third layer is thinner than the first layer.

18. The semiconductor device as claimed in claim 15 , wherein one surface, located on a side closer to the first insulating layer, and side surfaces of the first interconnect layer of the wiring board, are covered by the first layer.

19. The semiconductor device as claimed in claim 15 , wherein the first surface of the first insulating layer of the wiring board is smoother than a second surface of the first insulating layer opposite to the first surface of the first insulating layer.

20. The wiring board as claimed in claim 1 , wherein

the first interconnect layer is embedded in the first layer of the first insulating layer, and does not extend through the entire first layer,

the second interconnect layer is formed directly on the second layer of the first insulating layer, and

the second insulating layer is formed on the second layer of the first insulating layer, and covers the second interconnect layer.