JP4265001B2 - Flexible printed circuit board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer flexible printed circuit board.
[0002]
[Prior art]
Conventionally, a single-sided or double-sided flexible printed circuit board (hereinafter referred to as FPC) has been used to connect a circuit in a personal computer body to a circuit in a display unit that includes a liquid crystal unit and can be opened and closed. In this case, since the FPC expands and contracts and bends as the display unit is opened and closed, a flexible and highly durable FPC is required.
[0003]
FIG. 2 is a perspective view showing an example of the shape of the FPC connected to the circuit in the personal computer main body and the circuit in the display unit .
[0004]
In FIG. 2, one FPC includes a terminal portion 1 connected to the circuit of the display portion, a wound portion 2, a bent portion 3, and a terminal portion 4 connected to the circuit of the personal computer body. The terminal portion 1 and the terminal portion 4 move according to the rotation of the display unit. The wound portion 2 absorbs this movement to enhance the durability of the FPC and smooth the opening / closing operation of the display portion. For example, when the terminal part 1 and the terminal part 4 are pulled together, the wound part 2 becomes a smaller diameter winding, and when the terminal part 1 and the terminal part 4 are pressed together, the wound part 2 becomes a larger diameter winding. Become.
[0005]
Therefore, the FPC that connects the circuit of the display portion and the circuit of the main body, particularly the wound portion 2 and the bent portion 3, are required to have flexible bending performance and high durability of bending.
[0006]
Further, the FPC that connects the circuit of the display portion and the circuit of the main body is required to have a shielding performance that reduces unnecessary radiation and crosstalk between wires 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.
[0007]
FIG. 3 is a cross-sectional perspective view for explaining the configuration of a conventional FPC .
As shown in FIG. 3, in order to improve the above-described bending performance and unnecessary radiation and crosstalk, both sides of the back surface 6 of the circuit surface 5 of the FPC are provided with a shield pattern in a lattice shape at least at the bent portion. FPC is proposed in Japanese Utility Model Laid-Open No. 5-41171, for example. When the entire back surface 6 is made of copper foil, it is effective in reducing unwanted radiation and crosstalk, but since flexible and durable bending performance cannot be obtained, the copper foil of the grid eyes 7 is removed. .
[0008]
However, even in the above-described conventional double-sided FPC, when the frequency of the clock signal or the like becomes even higher, unnecessary radiation and crosstalk increase from the wound part and the bent part.
[0009]
Further, as the personal computer is downsized, the winding diameter of the FPC wound portion shown in FIG. 2 is reduced, and the portion A and the portion B shown in FIG. It has been difficult to reduce crosstalk, and the bending angle of the bent portion 3 has been reduced, making it difficult to obtain flexible and durable bending performance .
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and in particular, provides an FPC that can reduce crosstalk and unnecessary radiation at a bent portion and a wound portion, and can obtain a flexible and highly durable bending performance. For the purpose.
[0011]
[Means for Solving the Problems]
In the FPC of the present invention, a grid-like shield pattern is provided on both the front and back surfaces of the signal line layer , and the grid eyes (copper foil removed portions) from which the copper foil of the shield pattern is removed are on the front and back surfaces. It is characterized by being shifted so as not to overlap.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a grid-like shield pattern, that is, a GND copper foil is provided on the front and back surfaces of the signal copper foil layer, and the copper foil removed portions of the shield pattern are arranged so as not to overlap on the front and back surfaces. The flexible printed circuit board is characterized in that it is flexible and highly flexible, and has the effect of reducing unnecessary radiation and crosstalk.
[0013]
In the present invention, the GND copper foil is provided on both sides of the signal copper foil, and an effect of reducing high-quality unnecessary radiation and crosstalk can be obtained.
[0014]
Further, the present invention is such that the copper foil portions of the shield pattern on the front surface and the back surface are connected to each other through a plurality of through holes , thereby making the ground potential on the front surface and the back surface more equal and improving the shielding effect. Is obtained.
[0015]
Hereinafter, embodiments of the flexible printed circuit board (FPC) of the present invention will be described.
[0016]
(Embodiment 1)
FIG. 1A is a cross-sectional perspective view of the first embodiment of the FPC of the present invention, and FIG. 1B is a perspective view of the front and back shield patterns of the first embodiment of the FPC of the present invention.
[0017]
In FIG. 1A, the FPC has a three-layer configuration in which the 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.
[0018]
The surface 12 includes a grid-like shield pattern having a through-hole 16 in a grid-eye portion (copper foil-removed portion) 14 from which the copper foil has been removed, a grid-like GND copper foil 15 and a GND copper foil 15 portion. Yes. The GND copper foil 15 is held at the ground potential.
[0019]
The inner layer 11 includes a high-frequency signal copper foil 18 sandwiched between a GND copper foil 17 connected to the through hole 16.
[0020]
The back surface 13 is provided with a grid-like shield pattern having through-holes 21 in a grid eye portion (copper foil removed portion) 20 from which copper foil has been removed, a grid-like GND copper foil 19 and a GND copper foil 19 portion. Yes. The GND copper foil 19 is a GND pattern.
[0021]
The through hole 21 is connected to the GND copper foil 17 of the inner layer 11, and is further connected to the GND copper foil 15 of the surface 12 through the through hole 16.
[0022]
A plurality of through-holes 16 and 21 are provided, and the GND copper foils 15, 17 and 19 of the three layers of the front surface 12, the inner layer 11 and the back surface 13 are connected. Therefore, the signal copper foil 18 is surrounded by the adjacent GND copper foil 17, the GND copper foil 15 on the front surface 12, the GND copper foil 19 on the back surface 13, and the conductive through holes 16 and 21. To reduce.
[0023]
FIG. 1B is an explanatory diagram showing the relationship between the copper foil removed portion 14 on the front surface 12 and the copper foil removed portion 20 on the back surface 13.
[0024]
In FIG. 1B, a circle with a large solid line indicates a copper foil removed portion 14 on the front surface 12, a circle with a large dotted line indicates a copper foil removed portion 20 on the back surface 13, and a small circle indicates a through hole 16 on the front surface 12 and a through hole on the back surface 13. Hall 21 is shown.
[0025]
As shown in FIG. 1B, the flexible and durable flexibility of the FPC is unnecessary by shifting the positions of the copper foil removing portion 14 on the front surface 12 and the copper foil removing portion 20 on the back surface 13 so as not to overlap. Reduction of radiation and crosstalk can be obtained.
[0026]
Here, if the positions of the copper foil removal portion 14 on the front surface 12 and the copper foil removal portion 20 on the back surface 13 overlap, there may be cases where there is no GND copper foil of the shield pattern above and below the signal copper foil 18 of the inner layer 11. Radiation and crosstalk increase.
[0027]
By disposing the center point of the circle of the copper foil removed portion 20 of the back surface 13 at the midpoint of a regular triangle connecting the center points of the circles of the adjacent copper foil removed portions 14 of the surface 12, the back surface and the surface are shifted, Increase flexibility.
[0028]
The copper foil removal portions 14 and 20 are designed to have optimum dimensions and shapes so as to obtain both flexibility and unnecessary radiation and crosstalk performance. Although a slight overlap as shown in FIG. 1B is effective, it is effective to arrange the copper foil removed portion so as not to have a small overlap portion, but both bending radiation performance and crosstalk performance are slightly reduced. Will improve.
[0029]
The radiated electromagnetic wave generated from the high frequency signal flowing in the signal copper foil 18 includes the adjacent GND copper foil 17, the GND copper foil 15 on the top surface 12 of the high frequency signal copper foil 18, and the GND copper foil 19 on the back surface 13 obliquely below. Alternatively, it is absorbed by the GND copper foil 15 on the diagonally upper surface 12 of the high-frequency signal copper foil 18 and the GND copper foil 19 on the lower back surface 13 to reduce crosstalk and unnecessary radiation to other signal copper foils. Furthermore, crosstalk and unwanted radiation are also reduced by the through holes 16 and 21 provided close to each other.
[0030]
In addition, although Embodiment 1 of FPC of this invention demonstrated the copper foil removal part circular, other shapes may be sufficient. The present invention includes any arrangement in which the copper foil removal portion is shifted so that it does not overlap between the front surface and the back surface, and the GND copper foil is disposed on at least one of the upper and lower signal copper foils .
[0031]
【The invention's effect】
As described above, according to the FPC of the present invention, it is possible to realize a flexible and highly durable bendability and a reduction in crosstalk and unnecessary radiation even with respect to a bend with a small size, a small winding diameter, and a small angle.
[0032]
In addition, since it can be bent freely, it is possible to save space compared to coaxial cables and shielded wires.
[Brief description of the drawings]
1A is a cross-sectional perspective view of an FPC according to Embodiment 1 of the present invention. FIG. 1B is a plan perspective view of a shield pattern on the front and back surfaces of Embodiment 1 of the FPC according to the present invention. FIG. 3 is a perspective view for explaining an example of the shape of an FPC connected to the circuit in the display unit and the circuit in the display unit. FIG. 3 is a cross-sectional perspective view for explaining the configuration of a conventional FPC.
DESCRIPTION OF SYMBOLS 11 Inner layer 12 Front surface 13 Back surface 14 Copper foil removal part 15 GND copper foil 16 Through hole 17 GND copper foil 18 Signal copper foil 19 GND copper foil 20 Copper foil removal part 21 Through hole

Claims (2)

An inner layer comprising a signal copper foil and a GND copper foil arranged so as to sandwich the signal copper foil, a surface comprising a GND copper foil formed in a lattice shape by forming a plurality of copper foil removal portions, and a plurality of A back surface provided with a GND copper foil formed in a lattice shape by forming a copper foil removal portion, and a plurality of through holes provided in each of the GND copper foil portions of the front surface and the back surface,
By sandwiching the inner layer between the front surface and the back surface and arranging the center point of the copper foil removed portion on the back surface at the midpoint of a regular triangle connecting the center points of the adjacent copper foil removed portions on the surface, It arranges so that the copper foil removal part on the front surface and the copper foil removal part on the back surface do not overlap, and is configured in three layers, and each GND copper foil by a through hole provided in each GND copper foil part on the front surface and the back surface Is connected to the GND copper foil of the inner layer, and the signal copper foil of the inner layer is connected to the GND copper foil of the inner layer in a state where the GND copper foil of the front surface, the back surface and the inner layer are connected by a plurality of through holes. A flexible printed circuit board configured to be surrounded by GND copper foils and through holes on the front surface and the back surface . The flexible printed circuit board according to claim 1, wherein each copper foil removal portion formed on each GND copper foil on the front surface and the back surface has a circular shape .

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