METHOD FOR MANUFACTURING CIRCUIT BOARD

1 . A method for manufacturing a circuit board comprising a high-frequency circuit, wherein the high-frequency circuit comprises a substrate, a ground layer, and a signal layer, and at least the signal layer is a layer derived from a copper foil, wherein the method comprises:

(a) designing a specification of a high-frequency circuit having a predetermined impedance Z 1 based on an assumption that the high-frequency circuit is manufactured using a copper foil without an adhesive layer; and

(b) forming a high-frequency circuit in accordance with the specification, except for using, instead of the copper foil without the adhesive layer as assumed in the specification, an adhesive-layer-attached copper foil to form the signal layer so that an adhesive layer is interposed between the substrate and the signal layer, thereby manufacturing a circuit board in which the high-frequency circuit has an impedance Z 2 that is greater than Z 1 .

2 . The method for manufacturing the circuit board according to claim 1 , wherein a copper foil without an adhesive layer is used to form the ground layer.

3 . The method for manufacturing the circuit board according to claim 1 , wherein an impedance excess rate calculated by the formula ((Z 2 −Z 1 )/Z 1 )×100 is 1% or more and 20% or less.

4 . The method for manufacturing the circuit board according to claim 1 , wherein when the length of the high-frequency circuit is L (mm), Z 2 satisfies the following formula: Z 1 <Z 2 ≤{(1/15)×(L+755)}×Z 1 /50.

5 . A circuit board manufactured by the method according to claim 1 , wherein an impedance excess rate calculated by the formula ((Z 2 −Z 1 )/Z 1 )×100 is 1% or more and 20% or less.

6 . The circuit board according to claim 5 , wherein when the length of the high-frequency circuit is L (mm), Z 2 satisfies the following formula:

Z

1

<

Z

2

≤

{

(

1

/

1

⁢

5

)

×

(

L

+

7

⁢

5

⁢

5

)

}

×

Z

1

/

5

⁢

0

.