JP2000138425A - Connecting wiring structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To damp unnecessary noise outside the frequency band of the signal transmitted through wiring without increasing hardware resources. SOLUTION: A connecting wiring board is provided with a first wiring layer connecting first and second electronic circuit boards PC1 and PC2 to each other and a second wiring layer W2 which is faced oppositely to the first wiring layer in an insulating state. The second wiring layer W2 has a plurality of holes HL which are distributed in such a pattern that an impedance which damps unnecessary noise outside the frequency band of the signal transmitted through the first wiring layer is obtained at part of the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a connection wiring structure for connecting a plurality of electronic circuit boards, for example, a connection wiring structure having a wiring layer for shielding noise radiation.

[0002]

2. Description of the Related Art In a small electronic device, an electronic circuit is often mounted by being divided into a plurality of electronic circuit boards due to a limitation of an accommodation space. These electronic circuit boards are connected to each other by, for example, a flexible printed wiring board. The flexible printed wiring board has a structure in which wiring layers including various signal lines, power lines, ground lines, and the like are formed on a base film. If radiation noise from the flexible printed wiring board is a problem, the shield layer should be used for signal lines, power lines,
The wiring layer is formed as a wiring layer that extends so as to face the entire wiring layer such as a ground wire and is disposed on the back side of the base film.

[0003] Such a flexible printed wiring board is mounted at an acute angle or gently bent, except when a plurality of electronic circuit boards are arranged side by side in the same plane. The shape of the shield layer is set to, for example, a mesh shape or a porous shape in order to avoid the stress caused by the bending. Further, the shield layer is preferably formed as wide as possible in order to obtain good shield characteristics capable of sufficiently suppressing noise radiation, but this increases the parasitic capacitance between the signal line and the shield layer, and increases The high frequency component of the signal transmitted at high speed is lost. The shape of the shield layer described above is also effective in reducing the loss of the high frequency component.

[0004]

By the way, the conventional flexible printed wiring board has no unnecessary outside the signal frequency band transmitted through the signal line, the power supply line, the ground line, etc. even if the shield layer has the above-mentioned shape. Noise cannot be removed. When a return current is applied to the ground line to remove the unnecessary noise, noise radiation is generated from the shield layer capacitively coupled to the ground line. To prevent this, it is necessary to insert an additional component such as a low-pass filter on the output side of each electronic circuit board.

SUMMARY OF THE INVENTION An object of the present invention is to provide a connection wiring structure capable of attenuating unnecessary noise outside a signal frequency band transmitted through a wiring without increasing hardware resources.

[0006]

According to the present invention, there is provided a first wiring layer connecting a plurality of electronic circuit boards, and a second wiring layer insulated from and opposed to the first wiring layer. Layer 1
Provided is a connection wiring structure having a plurality of holes that partially distribute an impedance for attenuating unnecessary noise outside a signal frequency band transmitted through a wiring layer in a pattern obtained.

In this connection wiring structure, the plurality of holes provided in the second wiring layer are distributed in a pattern that partially obtains an impedance for attenuating unnecessary noise outside the signal frequency band transmitted through the first wiring layer. I do. Since this impedance portion does not significantly affect the overall parasitic capacitance between the first and second wiring layers, noise radiation from the second wiring layer can be avoided. Therefore, unnecessary noise can be attenuated without increasing hardware resources.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A connection wiring board according to an embodiment of the present invention will be described below with reference to the drawings.

This connection wiring board is formed as a flexible printed wiring board for connecting a plurality of electronic circuit boards incorporated in an electronic device to each other, and connects, for example, a personal computer body and a liquid crystal display device.

FIG. 1 shows a wiring structure of a connection wiring board, and FIG.
Shows a cross-sectional structure of the connection wiring board along the line II-II shown in FIG. As shown in FIG. 1, the connection wiring board FPC includes an insulating base film BS, a first wiring layer W1 disposed on the front side of the base film BS, and a second wiring layer W2 disposed on the back side of the base film BS. And an insulating cover film CF covering these wiring layers W1 and W2. The first wiring layer includes power supply lines VDD connected to electronic circuit boards PC1 and PC2 via pads PD,
It includes a ground line GND and signal lines S1-S4. The second wiring layer W2 is a shield layer that is insulated from the first wiring layer W2 by the base film BS and shields noise radiation from the first wiring layer W1. The second wiring layer W2 extends so as to face the entire first wiring layer W1 in order to obtain a good shielding effect. These wiring layers W1 and W2
Are obtained by printing a conductive film on the base film BS and patterning the conductive film.

As shown in FIG. 3, the second wiring layer W2 is
It has a plurality of circular holes HL for reducing capacitive coupling with the wiring layer W1 and reducing bending stress. Further, the first wiring layer W2 is divided into an area N located substantially at the center in the longitudinal direction of the first wiring layer W1, and areas M located on both sides of the area N adjacent to the electronic circuit boards PC1 and PC2, respectively. The holes HL are distributed in a pattern shown in FIG. 3 in order to partially obtain an impedance for attenuating unnecessary noise outside the signal frequency band transmitted via the first wiring layer W1. Specifically, the diameter D1
Are arranged in the area N, and a hole HL having a diameter D2 smaller than the diameter D1 is arranged in the area M. Note that D1
/D2=1.5.

In this case, when the capacity of the circular hole is represented by Cm in the area M and represented by Cn in the area N, these capacity ratios are as follows.

Cm / Cn = 1.5 × 1.5 = 2.25 Here, assuming that the wavelength of the unnecessary noise is λ, when m is sufficiently smaller than λ / 4, the noise attenuation ratio of Cm to Cn becomes It looks like an expression.

20 log (Cm / Cn) = 7 db Such a connection wiring board FPC is shown in FIG.
Are bent corresponding to the mounting positions of the electronic circuit boards PC1 and PC2 as shown in FIG.

According to this embodiment, the plurality of holes HL provided in the second wiring layer W2 provide an impedance in the area M for attenuating unnecessary noise outside the signal frequency band transmitted through the first wiring layer W1. Are distributed in a given pattern. Since this impedance portion does not significantly affect the overall parasitic capacitance between the first wiring layer W1 and the second wiring layer W2, noise radiation from the second wiring layer W2 can be avoided. Therefore, unnecessary noise can be attenuated without increasing hardware resources such as a low-pass filter formed as an independent component.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist thereof.

In the second wiring layer W2, the above-mentioned effects can be obtained even if the plurality of holes HL are polygons represented by, for example, a square as shown in FIG.

Further, by setting the size of these holes HL to two or more types as shown in FIG. 6, unnecessary noise can be more effectively attenuated.

In the above embodiment, the connection wiring board is formed as a flexible wiring board, but may be formed as a rigid wiring board. In this case, the electronic circuit board P
C1 and PC2 may be formed integrally with the rigid wiring board.

[0020]

As described above, according to the present invention, it is possible to provide a connection wiring structure capable of attenuating unnecessary noise outside the signal frequency band transmitted via wiring without increasing hardware resources.

[Brief description of the drawings]

FIG. 1 is a diagram showing a wiring structure of a connection wiring board according to one embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of a connection wiring board taken along line II-II shown in FIG.

FIG. 3 is a diagram showing a planar structure of a second wiring layer shown in FIG. 2 together with an equivalent circuit.

FIG. 4 is a view showing a connection wiring board bent at an acute angle according to a mounting position of the first and second electronic circuit boards shown in FIG. 1;

FIG. 5 is a view showing a connection wiring board which is gently bent in accordance with a mounting position of the first and second electronic circuit boards shown in FIG. 1;

FIG. 6 is a diagram showing a first modification of the second wiring layer shown in FIG. 3;

FIG. 7 is a diagram showing a second modification of the second wiring layer shown in FIG. 3;

[Explanation of symbols]

 PC1, PC2: Electronic circuit board FPC: Connection wiring board VDD: Power supply line GND: Ground line S1-S4: Signal line W1: First wiring layer W2: Second wiring layer BS: Base film CF: Cover film HL: Hole

Claims (6)

[Claims] A first wiring layer connecting a plurality of electronic circuit boards; and a second wiring layer insulated from and opposed to the first wiring layer, wherein the second wiring layer is interposed through the first wiring layer. A connection wiring structure comprising a plurality of holes in which an impedance for attenuating unnecessary noise outside a signal frequency band to be transmitted is distributed in a pattern obtained partially. 2. The pattern according to claim 1, wherein the plurality of hole patterns are set such that a parasitic capacitance between the first and second wiring layers is different in a length direction of the first wiring layer. Connection wiring structure. 3. The second wiring layer is divided into a plurality of regions in a length direction of the first wiring layer, and the size of the plurality of holes is smaller in a region closer to the plurality of electronic circuit boards in these regions. The connection wiring structure according to claim 2, wherein the connection wiring structure is set. 4. The connection wiring structure according to claim 1, wherein said first and second wiring layers are formed on the front and back of an insulating substrate, respectively. 5. The connection wiring structure according to claim 1, wherein said first wiring layer includes a signal line, a power supply line, and a ground line which are insulated from each other. 6. The connection wiring structure according to claim 1, wherein said second wiring layer is a shield layer for shielding noise radiation from said first wiring layer.