Wiring board and semiconductor package using the same

1. A wiring board comprising:

a base insulating film which has a thickness of 20 to 100 μm and in which via holes are formed;

a lower wiring which is formed on the under surface of said base insulating film and which is connected to said via holes; and

an upper wiring which is formed on said base insulating film and which is connected to said lower wiring through said via holes,

said base insulating film being composed of a heat-resistant resin, which has a glass-transition temperature of 150° C. or higher and which contains reinforcing fibers made of glass or aramid, and having the following physical properties (1) to (6) when an elastic modulus at a temperature of T° C. is given as D T (GPa), and when a breaking strength at a temperature of T° C. is given as H T (MPa),

(1) A coefficient of thermal expansion in the direction of thickness thereof is 90 ppm/K or less,

(2) D 23 ≧5

(3) D 150 ≧2.5

(4) (D −65 /D 150 )≦3.0

(5) H 23 ≧140

(6) (H −65 /H 150 )≦2.3

wherein a concave portion is formed on the under surface of said base insulating film, and said lower wiring is embedded in said concave portion wherein the under surface of said lower wiring is located higher than the under surface of said base insulating film by 0.5 to 10 μm.

2. The wiring board according to claim 1 , wherein said reinforcing fiber has a diameter of 10 μm or smaller.

3. The wiring board according to claim 1 , further comprising one or more wiring structure layers, each of said wiring structure layers comprising:

an intermediate wiring placed between said base insulating film and said upper wiring and connected to said lower wiring through said via holes; and

an intermediate insulating film which is formed so as to cover said intermediate wiring and in which other via holes connecting said intermediate wiring to said upper wiring are formed.

4. The wiring board according to claim 1 , further comprising a protective film which is formed under said base insulating film, cover a part of said lower wiring, and exposes the remainder of said lower wiring.

5. The wiring board according to claim 1 , further comprising a solder resist layer which covers a part of said upper wiring and exposes the remainder of said upper wiring.

6. A semiconductor package comprising:

the wiring board according to claim 1 ; and

a semiconductor device mounted on said wiring board.

7. The semiconductor package according to claim 6 , wherein said semiconductor device is connected to said lower wiring.

8. The semiconductor package according to claim 6 , wherein said semiconductor device is connected to said upper wiring.

9. The semiconductor package according to claim 6 , further comprising a connecting terminal which is used for connection to external device and is connected to said upper wiring or said lower wiring.

10. A wiring board comprising:

a base insulating film which has a thickness of 20 to 100 μm and in which via holes are formed;

a lower wiring which is formed on the under surface of said base insulating film and which is connected to said via holes; and

an upper wiring which is formed on said base insulating film and which is connected to said lower wiring through said via holes,

said base insulating film being composed of a heat-resistant resin, which has a glass-transition temperature of 150° C. or higher and which contains reinforcing fibers made of glass or aramid, and having the following physical properties (1) to (6) when an elastic modulus at a temperature of T° C. is given as D T (GPa), and when a breaking strength at a temperature of T° C. is given as H T (MPa),

(1) A coefficient of thermal expansion in the direction of thickness thereof is 90 ppm/K or less,

(2) D 23 ≧5

(3) D 150 ≧2.5

(4) (D −65/ D 150 )≦3.0

(5) H 23 ≧140

(6) (H −65/ H 150 )≦2.3

wherein a concave portion is formed on the lower surface of the base insulating film, and the lower wiring is embedded in the concave portion, and at least a part of the lower wiring is a connecting electrode for mounting a semiconductor device.

11. The wiring board according to claim 10 , wherein said reinforcing fiber has a diameter of 10 μm or smaller.

12. The wiring board according to claim 10 , further comprising one or more wiring structure layers, each of said wiring structure layers comprising:

an intermediate wiring placed between said base insulating film and said upper wiring and connected to said lower wiring through said via holes; and

an intermediate insulating film which is formed so as to cover said intermediate wiring and in which other via holes connecting said intermediate wiring to said upper wiring are formed.

13. The wiring board according to claim 10 , further comprising a protective film which is formed under said base insulating film, cover a part of said lower wiring, and exposes the remainder of said lower wiring.

14. The wiring board according to claim 10 , further comprising a solder resist layer which covers a part of said upper wiring and exposes the remainder of said upper wiring.

15. A semiconductor package comprising:

the wiring board according to claim 10 ; and

a semiconductor device mounted on said wiring board.

16. The semiconductor package according to claim 15 , wherein said semiconductor device is connected to said lower wiring.

17. The semiconductor package according to claim 15 , wherein said semiconductor device is connected to said upper wiring.

18. The semiconductor package according to claim 15 , further comprising a connecting terminal which is used for connection to external device and is connected to said upper wiring or said lower wiring.