JP2000151115A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board that can constitute circuits with excellent characteristics and high density in mounting at a low cost. SOLUTION: Since a capacitance element 22 for matching impedances of circuit parts 24, 25 is constituted by an insulating layer of a printed wiring board 11 itself and copper foils opposed to the insulating layer, no electrical part is required for matching the impedances. Furthermore, since the electrical characteristics of the capacitance element 22 are accurately determined by the material of the insulating layer and the area of the copper foils 13, 14, the impedances can be accurately matched with a small number of capacitance elements 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board for mounting a circuit component to form a circuit.

[0002]

2. Description of the Related Art Even if circuit components are mounted on a printed wiring board and connected by wiring, it is unnecessary if the impedance of the circuit component on the signal sending side and the impedance of the circuit component on the signal receiving side do not match. Radiation or the like occurs, and a circuit having excellent characteristics cannot be formed. In particular, a digital circuit having a higher signal transmission speed than an analog circuit has a large effect due to impedance mismatch.

For example, in an analog circuit for video signal processing, the frequency is at most about 10 MHz, but in a digital circuit, the frequency is 100 MHz or more, so that the influence of impedance mismatch cannot be ignored.
For this reason, in the conventional printed wiring board, the impedance of the mounted circuit components has been matched by additionally mounting electric components such as a filter including an inductive element and a capacitive element.

[0004]

However, despite the fact that the capacitance of the capacitive element required for impedance matching is only a few pF, when an electric component is mounted by soldering, this may also be affected by the degree of solder adhesion. Electric characteristics such as stray capacitance of electric components fluctuate. For this reason, in the conventional printed wiring board, it is difficult to accurately match the impedances of the mounted circuit components, and it is necessary to mount additional electrical components to compensate for the changed electrical characteristics. .

That is, in the conventional printed wiring board, it has been difficult to construct a circuit having excellent characteristics and high mounting density at low cost. Accordingly, an object of the invention of the present application is to provide a printed wiring board capable of forming a circuit having excellent characteristics and high mounting density at low cost.

[0006]

According to a first aspect of the present invention, there is provided a printed wiring board, wherein a capacitive element is connected to a wiring for connecting circuit components to be mounted, and matches impedances of the circuit components. Are composed of an insulating layer of the printed wiring board itself and a conductive layer facing through the insulating layer. Therefore, there is no need to mount a separate electric component for matching the impedance of these circuit components other than the circuit component to be mounted.

Moreover, when an electrical component is mounted by soldering, the electrical characteristics such as the stray capacitance of the electrical component fluctuate depending on the degree of adhesion of the solder. The electrical characteristics of the capacitor composed of the conductive layer formed are determined accurately by the material of the insulating layer and the area of the conductive layer. Therefore, the impedances of the circuit components to be mounted can be accurately matched with a small number of capacitive elements.

In the printed wiring board according to the second aspect, a conductive layer forming wiring for connecting circuit components to be mounted and a capacitor for matching impedances of the circuit components to be mounted. The conductive layers constituting the element are different from each other. For this reason, the wiring for connecting the circuit components to be mounted and the capacitance element for matching the impedances of these circuit components can be three-dimensionally arranged.

In the printed wiring board according to the third aspect, the circuit components to be mounted are digital circuit components, and a digital circuit having a higher signal transmission speed than an analog circuit is greatly affected by impedance mismatch. But,
By the capacitive element composed of the insulating layer of the printed wiring board itself and the conductive layer facing through the insulating layer,
The impedances of the digital circuit components can be accurately matched.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to a four-layer printed wiring board will be described below with reference to FIGS. FIG. 1 shows the present embodiment. Before describing the present embodiment, the basic concept of the present invention is described with reference to FIG.
This will be described with reference to FIG. FIG. 2 shows a four-layer printed wiring board. That is, in this printed wiring board 11, 4
The copper foil layers 12 to 15 are sequentially laminated via insulating layers 16 to 18 made of phenol resin or the like.

Accordingly, one capacitance element 21 is constituted by the stray capacitance of the copper foil layer 12, the insulating layer 16 and the copper foil layer 13, and the copper foil layer 13, the insulating layer 17 and the copper foil layer 14
Another capacitance element 22 is constituted by the stray capacitance due to the above, and another capacitance element 23 is constituted by the stray capacitance due to the copper foil layer 14, the insulating layer 18 and the copper foil layer 15.

Next, this embodiment will be described. As shown in FIG. 1, in the printed wiring board 11 of the present embodiment, the copper foil layer 1
2 is processed into a wiring pattern.
The digital circuit components 24 and 25 are connected to both ends of each by soldering. Capacitive element 22 is via hole 26
Connected to the copper foil layer 12 via the
Is connected to the copper foil layer 15 via the.

The capacitive element 22 includes digital circuit components 24, 2
5 are used to match the impedances of each other.
2, the copper foil layers 13 and 14 are processed into patterns of both electrodes of the capacitor 22. Note that in order to match the impedances of the digital circuit components 24 and 25, it is also possible to use a capacitor element 21 in which one electrode is formed of the copper foil layer 12 similarly to the wiring.

However, in the printed wiring board, the wiring width is becoming narrower and shorter in order to increase the mounting density and optimize the arrangement of circuit components.
It is becoming difficult to arrange the wiring connecting the elements 4 and 25 and the capacitor 21 in a plane. On the other hand, in the printed wiring board 11 of the present embodiment, the wiring connecting the digital circuit components 24 and 25 and the capacitor 2
2 are different from each other in the copper foil layers 12, 13, 1
4, these wirings and the capacitor 22
Are three-dimensionally arranged, and these can be easily arranged.

The printed wiring board 1 of the above embodiment
Although digital circuit components 24 and 25 are mounted on 1, analog circuit components may be mounted instead of digital circuit components 24 and 25, and digital circuit components 2 and 25 may be mounted.
4, 25 and analog circuit components may be mixedly mounted. In the above embodiments, the invention of the present application is applied to a four-layer printed wiring board, but the invention of the present application can also be applied to printed wiring boards other than four layers.

[0016]

In the printed wiring board according to the first aspect, it is not necessary to mount a separate electric component for matching impedances of these circuit components other than the circuit component to be mounted, and moreover, it is mounted. Since the impedance of the circuit components to be matched can be accurately matched with a small number of capacitance elements, a circuit having excellent characteristics and high mounting density can be formed at low cost.

In the printed wiring board according to the second aspect, the wiring for connecting the circuit components to be mounted and the capacitance element for matching the impedance of these circuit components can be three-dimensionally arranged. Therefore, a circuit with a higher mounting density can be configured.

In the printed wiring board according to the third aspect, since the impedances of the digital circuit components can be accurately matched, a digital circuit having excellent characteristics can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a four-layer printed wiring board to which the present invention can be applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Printed wiring board, 12-15 ... Copper foil layer (conductive layer), 16-18 ... Insulating layer, 21-23 ... Capacitance element, 2
4, 25 ... Digital circuit parts (circuit parts)

Claims (3)

[Claims] 1. A plurality of conductive layers sequentially laminated via an insulating layer, wiring formed of the conductive layer and connecting circuit components to be mounted, and the insulating layer A printed wiring board, comprising: a conductive element facing the conductive layer, the conductive layer being opposed to the conductive layer via the insulating layer, and connected to the wiring, and having a capacitance element for matching impedances of the circuit components. 2. The printed wiring board according to claim 1, wherein said conductive layer forming said wiring and said conductive layer forming said capacitance element are different from each other. 3. The printed wiring board according to claim 1, wherein said circuit component is a digital circuit component.