JP2000114728A - Flexible printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FPC(flexible printed circuit) which can suppress cross- talk and unnecessary radiation especially at a bent part and a wound part and obtain flexible and durable performance. SOLUTION: This FPC has a three-layer structure consisting of a wiring layer 11, a surface layer 12 and a rear layer 13. The surface layer 12 and the rear layer 13 have lattice-shaped shielding patterns so as to hold the wiring layer 11 between them. The copper foil removed parts 14 and 20 of the shielding patterns of the surface layer 12 and the rear layer 13 are shifted relatively to each other so as not to overlap each other. The copper foil parts 15 and 19 of shielding patterns of the surface layer 12 and the rear layer 13 and the GND pattern of the wiring layer 11 are connected to each other with a plurality of through-holes 16 and 21 and a signal copper foil 18 is totally surrounded by a ground potential (GND).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a multilayer flexible printed circuit board.

[0002]

2. Description of the Related Art Conventionally, a single-sided or double-sided flexible printed circuit board (hereinafter, referred to as a single-sided or double-sided printed circuit board) is used to connect a circuit in a personal computer main body and a circuit in a display unit including a liquid crystal unit and capable of being opened and closed.
FPC). In this case, the FPC expands and contracts or bends when the display unit is opened and closed, so that a flexible and highly durable FPC is required.

FIG. 2 is a perspective view illustrating an example of the shape of an FPC connected to a circuit in a personal computer and a circuit in a display unit.

In FIG. 2, one FPC has a terminal portion 1 connected to a circuit of a display unit, a wound portion 2, a bent portion 3, and a terminal portion 4 connected to a circuit of a personal computer main body. . The terminal portion 1 and the terminal portion 4 move according to the rotation of the display unit. The rolled portion 2 absorbs this movement to enhance the durability of the FPC and to smoothly open and close the display unit. For example, when the terminal portion 1 and the terminal portion 4 are pulled, the wound portion 2 has a smaller diameter winding, and when the terminal portion 1 and the terminal portion 4 are pressed, the wound portion 2 has a larger diameter winding. Become.

[0005] Therefore, the FPC for connecting the circuit of the display section and the circuit of the main body, in particular, the rolled portion 2 and the bent portion 3 are required to have flexible bending performance and high durability of bending.

Further, an FPC that connects a circuit of the display unit and a circuit of the main body is required to have a shielding performance for reducing unnecessary radiation and crosstalk between wirings because a high-frequency current such as a clock signal flows. In particular, strong unnecessary radiation and crosstalk are likely to occur from the wound portion 2 and the bent portion 3.

FIG. 3 is a sectional perspective view for explaining the structure of a conventional FPC. As shown in FIG. 3, in order to improve the aforementioned bending performance and unnecessary radiation and crosstalk, F
On the back surface 6 of the circuit surface 5 of the PC, a double-sided FPC in which a shield pattern is provided in a lattice shape at least in a bent portion,
For example, it is proposed in Japanese Utility Model Laid-Open No. 5-41171. When the entire surface of the back surface 6 is made of copper foil, it is effective in reducing unnecessary radiation and crosstalk, but since a flexible and highly durable bending performance cannot be obtained, the copper foil of the grid 7 is removed. .

However, even in the conventional double-sided FPC,
When the frequency of a clock signal or the like becomes higher, unnecessary radiation or crosstalk increases from a wound portion or a bent portion.

Further, as the size of the personal computer is reduced, the winding diameter of the portion where the FPC is wound as shown in FIG. 2 is reduced, and the portion A and the portion B shown in FIG.
It becomes difficult to reduce unnecessary radiation and crosstalk.
The bending angle of the bending portion 3 became small, and it became difficult to obtain a flexible and durable bending performance.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in particular, reduces crosstalk and unnecessary radiation at a bent portion and a wound portion, and is flexible and durable. An object of the present invention is to provide an FPC capable of obtaining bending performance.

[0011]

According to the FPC of the present invention, a grid-like shield pattern is provided on both the front surface and the back surface of the wiring layer, and the grid pattern (copper) from which the copper foil in the shield pattern has been removed is provided. (Foil-removed portion) are arranged so as to be shifted from each other so as not to overlap on the front surface and the back surface.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a grid-like shield pattern is provided on the front and back surfaces of a wiring layer, and the copper foil-removed portions of the shield pattern are formed on the front and back surfaces. A flexible printed circuit board characterized by being staggered so as not to overlap with each other. The flexible printed circuit board has a flexible and durable bendability and an effect of reducing unnecessary radiation and crosstalk.

According to a second aspect of the present invention, there is provided the flexible printed circuit board according to the first aspect, wherein a GND foil extends along both sides of the signal foil of the wiring layer, and has an effect of reducing unnecessary radiation and crosstalk. Is obtained.

According to a third aspect of the present invention, there is provided the flexible printed circuit board according to the first aspect, wherein the copper foil portions of the front and rear shield patterns are connected to each other by a plurality of through holes. The effect that the ground potential on the front surface and the ground potential on the back surface are more equal, and the shielding effect is improved can be obtained.

An embodiment of the flexible printed circuit (FPC) board of the present invention will be described below.

(Embodiment 1) FIG. 1 (a) shows the F of the present invention.
FIG. 1B is a perspective view of a shield pattern on the front surface and the back surface of the FPC according to the first embodiment of the present invention.

Referring to FIG. 1A, the FPC has a three-layer structure in which a wired inner layer 11 is sandwiched between a front surface 12 having a shield pattern and a back surface 13 having a shield pattern similar to the front surface 12. is there.

The surface 12 has a grid mesh portion (copper foil removed portion) 14 from which the copper foil has been removed, a grid-shaped GND copper foil 15 and a G
The ND copper foil 15 has a grid-like shield pattern having a through hole 16. The GND copper foil 15 is kept at the ground potential.

The inner layer 11 is composed of a high-frequency signal copper foil 1 sandwiched close to a GND copper foil 17 connected to a through hole 16.
8 is provided.

The back surface 13 has a grid portion (copper foil removed portion) 20 from which the copper foil has been removed, a grid-shaped GND copper foil 19 and a G
The ND copper foil 19 has a grid-like shield pattern having a through hole 21. GND copper foil 19 is GND
It is a pattern.

The through hole 21 is connected to the GND copper foil 17 of the inner layer 11,
The second GND copper foil 15 is also connected.

A plurality of through holes 16 and 21 are provided, and three layers of GND copper foils 15, 1
7 and 19 are connected. Therefore, the signal copper foil 18 is adjacent to the GND copper foil 17, the GND copper foil 15 on the front surface 12, and the back surface 13.
, And unnecessary radiation and crosstalk are reduced.

FIG. 1B shows a copper foil removal portion 14 on the surface 12.
FIG. 4 is an explanatory diagram showing a relationship between a copper foil removed portion 20 of the back surface 13.

In FIG. 1B, a large circle with a solid line indicates a copper foil removed portion 14 of the front surface 12 and a large circle with a dotted line indicates a back surface 13.
A small white dot indicates the through hole 16 on the front surface 12 and the through hole 21 on the back surface 13.

As shown in FIG. 1B, by shifting the positions of the copper foil removal portion 14 on the front surface 12 and the copper foil removal portion 20 on the rear surface 13 so as not to overlap, the flexible and durable bending of the FPC is achieved. And the following unwanted radiation and reduction of crosstalk can be obtained.

If the positions of the copper foil-removed portion 14 on the front surface 12 and the copper foil-removed portion 20 on the rear surface 13 overlap with each other, there may be no GND copper foil of the shield pattern above and below the signal copper foil 18 on the inner layer 11, which is unnecessary. Radiation and crosstalk increase.

By disposing the center point of the circle of the copper foil removal portion 20 of the back surface 13 at the midpoint of a regular triangle connecting the center points of the circles of the copper foil removal portion 14 of the front surface 12, the back surface and the front surface are shifted. Increase flexibility.

The copper foil-removed portions 14 and 20 are designed to have an optimum size and an optimum shape so as to obtain both flexibility and unnecessary radiation and crosstalk performance. As shown in FIG. 1 (b), even if a little overlap is effective, it is effective to arrange the copper foil removed portion so as not to have a small overlap portion, but the bending performance is slightly lowered, but both the unnecessary radiation and the crosstalk performance are reduced. Is improved.

The radiated electromagnetic wave generated from the high-frequency signal flowing through the signal copper foil 18 is transmitted to the adjacent GND copper foil 17, the GND copper foil 15 on the front surface 12 directly above the high-frequency signal copper foil 18, and the GND on the rear surface 13 obliquely below. Absorbed by the GND copper foil 15 on the obliquely upper surface 12 of the copper foil 19 or the high-frequency signal copper foil 18 and the GND copper foil 19 on the back surface 13 immediately below, reducing crosstalk and unnecessary radiation to other signal copper foils. I do. Further, crosstalk and unnecessary radiation are reduced by the through holes 16 and 21 provided close to each other.

In the first embodiment of the FPC of the present invention,
Although the copper foil removed portion has been described as being circular, other shapes may be used. The copper foil removal portion is shifted so that it does not overlap on the front and back surfaces, and GN is provided on at least one of the upper and lower signal patterns of the inner layer.
Any arrangement having D copper foil is included in the present invention.

[0031]

As described above, according to the FPC of the present invention,
For small size, small winding diameter and small angle bending,
Flexible and highly durable bendability and reduction of crosstalk and unnecessary radiation can be realized.

Also, since it can be freely bent, it is possible to realize a space saving compared with a coaxial cable or a shielded wire.

[Brief description of the drawings]

FIG. 1A is a cross-sectional perspective view of an FPC according to a first embodiment of the present invention. FIG. 1B is a perspective plan view of the front and back shield patterns of the FPC according to the first embodiment of the present invention.

FIG. 2 is a perspective view illustrating an example of the shape of an FPC connected to a circuit in a personal computer main body and a circuit in a display unit.

FIG. 3 is a cross-sectional perspective view illustrating a configuration of a conventional FPC.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 inner layer 12 front surface 13 back surface 14 copper foil removed portion 15 GND copper foil 16 through hole 17 GND pattern 18 signal copper foil 19 GND copper foil 20 copper foil removed portion 21 through hole

Claims (3)

[Claims] The present invention is characterized in that a grid-like shield pattern is provided on the front and back surfaces of a wiring layer, and a copper foil removed portion of the shield pattern is staggered so as not to overlap between the front and back surfaces. Flexible printed circuit board. 2. The flexible printed circuit board according to claim 1, wherein a GND foil extends along both sides of the signal foil of the wiring layer. 3. The flexible printed circuit board according to claim 1, wherein the copper foil portions of the front and rear shield patterns are connected to each other by a plurality of through holes.