JP2021064570A - Arrangement structure of flexible flat cable - Google Patents

Abstract

To prevent a deterioration of a transmission quality due to a dielectric constant of a conductor in a vicinity of a flexible flat cable, when using the flexible flat cable in a signal transmission where a crosstalk influence is not problematic.SOLUTION: An arrangement structure of a flexible flat cable arranges a flexible flat cable 10 in a proximity of a conductor such as a metal plate 20. An insulation sheet 30 configured to prevent a characteristic impedance of a signal that flows in a wire of the flexible flat cable 10 from varying by a dielectric constant of a conductor is arranged between the flexible flat cable 10 and the metal plate 20.SELECTED DRAWING: Figure 3

Description

The present invention relates to a flexible flat cable arrangement structure that suppresses deterioration of transmission quality due to the dielectric constant of a conductor in the vicinity of the flexible flat cable when the flexible flat cable is used for signal transmission in which the influence of crosstalk does not matter.

Many electric wires, that is, signal lines, are used in AV equipment such as VCRs, OA equipment such as copiers, and electronic equipment products such as home appliances to supply signals and electric power. A flexible flat cable (FFC) is used as a wiring material in order to reduce the size, density, weight, etc. of electronic devices. A flexible flat cable is a strip-shaped wiring material in which an electric wire is a flat conductor and a plurality of flat conductors are incorporated in an insulator in parallel in a plane. Such wiring materials are used not only as internal wiring materials for electronic device products, but also as connection wiring materials for connecting electronic devices to each other.

When a signal is transmitted in a state where a plurality of flexible flat cables are stacked, the transmission quality deteriorates due to the influence of crosstalk. Therefore, as described in Patent Document 1, a crosstalk suppressing means should be provided between the flexible flat cables. Wiring equipment has been developed. Crosstalk is a phenomenon in which a signal flowing through an electric wire of a wiring material is mixed with a signal or noise flowing through an electric wire of another wiring material, and the original signal is disturbed. It has been found that when a signal with a frequency of 1 GHz or higher flows through the wiring material, it disturbs the signal flowing through the other wiring material, and as the frequency rises, the signal and noise mixed in the signal of the other wiring material increase. , It is necessary to increase the thickness of the crosstalk suppressing member so that the distance between the wiring materials becomes long.

Japanese Unexamined Patent Publication No. 2014-863332

In the flexible flat cable, the maximum width of the strip-shaped wiring material is determined from the functional aspect, and the maximum number of cores that can be transmitted by one wire is determined by the conductor pitch of the metal conductor, that is, the flat conductor, which is incorporated in parallel within the width. The number of conductors is determined. When the number of cores exceeding the number of cores in one cable is required, it is necessary to stack a plurality of cables and install them in an electronic device product.

Even if there is only one part, component unit, or board assembly on the signal transmitting side in the electronic device, if there are multiple components, component units, or component units on the signal receiving side that are far from the signal transmitting side, the signal is received. In the vicinity of the side, only one end on the output side of the cable is arranged, whereas in the vicinity of the component on the signal transmission side, multiple ends on the input side of multiple cables are arranged in an overlapping manner. There are times. Even if the signal transmitting side and the receiving side are reversed, the arrangement is similarly performed.

Further, the flexible flat cable can be arranged close to the housing due to the strip-shaped flat thin structure. For this reason, the flexible flat cable can be effectively utilized in the space inside the housing by arranging the flexible flat cable close to the housing without occupying a mounting space, and is often installed so as to crawl on the housing. When the housing is made of metal, a flexible flat cable is laid on the metal housing, and in the case where a metal plate is added to the plastic housing body, the flexible flat cable is attached to the metal plate. Cables may crawl and be installed.

In this way, when the flexible flat cables are arranged so as to crawl on a metal housing or a metal plate, or when a plurality of flexible flat cables are arranged at least partially overlapped, crosstalk is as follows, as in 700 MHz or less. However, even if the digital signal has a low transfer speed that does not affect the transmission quality, the dielectric constant of the adjacent metal material causes an increase in the variation range of the characteristic impedance, which is one of the causes of lowering the transmission quality. In other words, the signal flowing through the wires of other wiring materials does not mix the signals and noise flowing through the wires of other wiring materials, but the dielectric constant of the metal material placed near the wiring material causes the characteristic impedance to vary. It was found that it occurred and caused a decrease in transmission quality.

An object of the present invention is to suppress deterioration of transmission quality due to the dielectric constant of a conductor in the vicinity of the flexible flat cable when the flexible flat cable is used for signal transmission in which the influence of crosstalk does not matter.

In order to solve the above problems, the flexible flat cable arrangement structure of the present invention according to claim 1 is a flexible flat cable arrangement structure in which the flexible flat cable is arranged close to the conductor, and the flexible flat cable is arranged. It is characterized in that an insulating sheet that suppresses the characteristic impedance of a signal flowing through an electric wire from fluctuating due to the dielectric constant of the conductor is arranged between the flexible flat cable and the metal material.

The arrangement structure of the flexible flat cable of the present invention according to claim 2 is an arrangement structure of a flexible flat cable in which a plurality of flexible flat cables are arranged in an overlapping manner, and one electric wire of two adjacent flexible flat cables is connected. An insulating sheet that suppresses the characteristic impedance of the flowing signal from fluctuating due to the dielectric constant of the other electric wire is arranged between the two adjacent flexible flat cables.

The arrangement structure of the flexible flat cable of the present invention according to claim 3 is an arrangement structure of a flexible flat cable in which the flexible flat cable is arranged along a metal component, and is a characteristic of a signal flowing through an electric wire of the flexible flat cable. An insulating sheet that suppresses the impedance from fluctuating due to the dielectric constant of the metal component is arranged between the flexible flat cable and the metal member.

The arrangement structure of the flexible flat cable of the present invention according to claim 4 corresponds to at least the position of a signal flowing through an electric wire in the flexible flat cable in the invention according to any one of claims 1 to 3. It is characterized in that the insulating sheet is arranged.

In the present invention, when a metal material such as a conductor of another flexible flat cable or a metal member is brought close to a flexible flat cable provided with a conductor for transmitting a signal, the characteristic impedance of the signal flowing through the flexible flat cable is the same as that of the metal material. It was developed because it was found to vary depending on the dielectric constant, and when a flexible flat cable is placed on another flexible flat cable or metal material via an insulating sheet, it is possible to suppress the variation in the characteristic impedance of the signal line. It was made with knowledge. If the variation in the characteristic impedance value can be suppressed by the insulating sheet, the deterioration of the transmission quality due to the flexible flat cable can be suppressed.

It is a perspective view which shows the flexible flat cable arranged on the metal plate. (A) is a plan view showing an end portion of the flexible flat cable shown in FIG. 1, and (B) is a vertical cross-sectional view showing a portion of a conductor in (A). It is a cut surface along the line I-I in FIG. 1, (A) shows one embodiment of the present invention, and (B) shows a comparative example. It is a perspective view which shows a plurality of flexible flat cables arranged in a stack. It is a cut surface along the line II-II in FIG. 3, (A) shows another embodiment of the present invention, and (B) shows a comparative example. (A) to (D) are plan views which show the arrangement structure of the flexible flat cable of another embodiment of this invention, respectively. It is a characteristic diagram which shows the change of the characteristic impedance of a flexible flat cable by comparison for each arrangement form. (A) is an impedance characteristic diagram of an example of a flexible flat cable when used alone, (B) is an impedance characteristic diagram when two flexible flat cables of (A) are stacked, and (C) is an impedance characteristic diagram. It is an impedance characteristic diagram when an insulating sheet is arranged between two flexible flat cables. (A) is an impedance characteristic diagram when the flexible flat cable of another example is used alone, and (B) is an impedance characteristic diagram when two flexible flat cables of (A) are stacked. ) Is an impedance characteristic diagram when an insulating sheet is arranged between two flexible flat cables. (A) is an impedance characteristic diagram when the flexible flat cable of another example is arranged on the copper foil, and (B) is the impedance characteristic when the insulating sheet is arranged between the flexible flat cable and the copper foil. It is a diagram.

Hereinafter, embodiments as an example of the present invention will be described in detail with reference to the drawings. In addition, in the drawing for demonstrating the embodiment, in principle, the same components are designated by the same reference numerals, and the repeated description thereof will be omitted.

FIG. 1 shows a state in which the flexible flat cable 10 is arranged on the metal plate 20, the flexible flat cable 10 is in contact with the metal plate 20 at the central portion 11 in the longitudinal direction, and both end portions 12 are made of metal. It is away from the board 20. As described above, on the metal plate 20 which is a metal component, the flexible flat cable 10 is arranged on the metal plate 20 so that the central portion 11 in the longitudinal direction thereof follows.

The flexible flat cable 10 has a plurality of flat conductors 13 arranged in parallel with each other at predetermined intervals, and one surface of both ends of the conductor 13 is exposed and the other portion is elastically deformable. It is covered with an insulator layer 14 made of the resin material of. Each conductor 13 transmits a signal having a frequency of 700 MHz or less. In the flexible flat cable 10 shown in FIG. 1, five conductors 13 are shown, but the number of conductors 13 is not limited to the number shown in the figure, and may be set to various numbers.

As shown in FIG. 2, the insulator layer 14 has an insulator layer 14a covering the lower surface of the conductor 13 in FIG. 1 and an insulator layer 14b covering the upper surface, and is between the conductors 13 adjacent to each other in the width direction. Is also involved. As described above, both sides of the conductor 13 are covered with the insulator layer 14, and one side is exposed at both end portions 12. A ground plate 15 is provided on the surface of the insulator layer 14a of both end portions 12 opposite to the conductor 13 via an insulating reinforcing plate 18, and the ground plate 15 is a flexible flat cable. When 10 is inserted into the connector, it comes into contact with the ground terminal of the connector and becomes a ground potential. An insulating adjusting material layer 16 is provided on the insulating layer 14a so as to be sandwiched between reinforcing plates 18 at both ends. A shield layer 17 is provided on the surface of the adjusting material layer 16 opposite to the insulator layer 14a, and both ends of the shield layer 17 are in contact with the ground plate 15.

As shown in FIG. 3A, an insulating sheet 30 is arranged between the metal plate 20 and the flexible flat cable 10. The flexible flat cable 10 may be abutted against the metal plate 20 via the insulating sheet 30, or may be fixed by adhesives applied to both sides of the insulating sheet 30. The insulating sheet 30 is formed of a resin such as polyethylene terephthalate, blocks the influence of the metal plate 20 on the signal line of the flexible flat cable 10, and the characteristic impedance of the signal flowing through the conductor 13 of the flexible flat cable 10 is a metal component. It suppresses variation due to the conductivity of the metal plate 20. As a result, it is possible to prevent the transmission quality of the signal transmitted by the conductor 13 of the flexible flat cable 10 from deteriorating.

FIG. 3B shows a case where the flexible flat cable 10 is placed in the metal plate 20 in direct contact with the metal plate 20 as a comparative example.

FIG. 4 shows a state in which two flexible flat cables 10a and 10b are overlapped and arranged at the central portion 11 in the longitudinal direction. Both ends 12 of one flexible flat cable 10a and both ends 12 of the other flexible flat cable 10b are separated from each other. The structure of the end portion 12 of each of the flexible flat cables 10a and 10b is the same as that of the flexible flat cable shown in FIG.

As shown in FIG. 5A, an insulating sheet 30 is arranged between both flexible flat cables 10a and 10b. As described above, the insulating sheet 30 is made of a resin such as polyethylene terephthalate, and the characteristic impedance of the signal flowing through the conductor 13 of one flexible flat cable 10a is the conductor 13 which is the electric wire of the other flexible flat cable 10b. Suppresses variation due to the conductivity of. Similarly, the characteristic impedance of the signal flowing through the conductor 13 of the other flexible flat cable 10b is suppressed from fluctuating due to the conductivity of the conductor 13 which is the electric wire of the other flexible flat cable 10a. As a result, it is possible to block the influence of the capacitance peculiar to the flexible flat cables 10a and 10b on the signal line and suppress the deterioration of the signal transmission quality of the flexible flat cables 10a and 10b.

FIG. 5A shows a case where two flexible flat cables are stacked, but three or more flexible flat cables may be arranged so as to be stacked, and between two adjacent flexible flat cables. Insulation sheets 30 are arranged respectively. As shown in FIG. 4, the flexible flat cables overlap not only when the central portions 11 in the longitudinal direction are parallel to each other and overlap, but also when one flexible flat cable overlaps so as to cross the other flexible flat cable. Also, the conductor 13 can suppress the variation in the characteristic impedance.

FIG. 5B shows a case where the two flexible flat cables 10a and 10b are arranged in direct contact with each other as a comparative example.

6 (A) to 6 (D) are plan views showing the arrangement positions of the insulating sheet 30 with respect to the flexible flat cable 10. FIG. 6A shows a case where the insulating sheet 30 is arranged at the center in the longitudinal direction except for both ends of the flexible flat cable 10. FIG. 6B shows a case where the insulating sheet 30 is arranged so as to correspond to the portion of the specific conductor 13 among the plurality of conductors 13. FIG. 6C shows a case where the insulating sheets 30 are arranged at both ends except for the central portion in the longitudinal direction. FIG. 6D shows a case where the insulating sheet 30 is arranged so as to correspond to the plurality of conductors 13.

As described above, the arrangement position of the insulating sheet 30 with respect to the flexible flat cable can be variously set according to the usage pattern of the flexible flat cable.

As the insulating sheet 30, a polyethylene terephthalate (PET) resin having a thickness of 0.025 mm can be used, and the relative permittivity of the insulating sheet 30 is about 3.3. Further, a polyphenylene sulfide (PPS) resin having a thickness of 0.025 mm can be used, and the relative permittivity of the insulating sheet 30 is about 3.0. Further, a liquid crystal polymer (LCP) resin having a dielectric constant of about 3.5, a polypropylene resin having a relative permittivity of 2.2 to 2.6, and a foamed polypropylene having a relative permittivity of 2.1 or less can be used.

Further, a vinyl chloride resin having a relative permittivity of 2.8 to 8.0, a polyethylene resin having a permittivity of 2.3 to 2.4, a polyurethane resin having a permittivity of 5.0 to 5.3, and a dielectric constant of 2 Polystyrene resin or the like of .4 to 2.6 can be used as an insulating sheet.

FIG. 7 shows the disturbance of the characteristic impedance of the flexible flat cable, that is, the change in the difference in impedance value, in each of the arrangement modes shown in FIGS. 3 (A), 3 (B), 5 (A), and 5 (B). It is a characteristic diagram which shows by comparison with.

When the flexible flat cable was used alone without contacting a metal material in the vicinity thereof, the variation in the characteristic impedance was as shown on the leftmost side in FIG. As a comparative example, as shown in FIG. 5B, when two flexible flat cables 10a and 10b are brought into direct contact with each other, one flexible flat cable is affected by the conductor 13 of the other flexible flat cable and has a characteristic impedance. The variation has more than doubled. On the other hand, as shown in FIG. 5A, when the insulating sheet 30 is arranged between the two flexible flat cables 10a and 10b, the variation in the characteristic impedance of each flexible flat cable is different from that in the case of single use. It was almost the same.

Similarly, when the flexible flat cable 10 is brought into direct contact with the metal plate 20, the flexible flat cable 10 is affected by the metal plate 20 and the variation in the characteristic impedance becomes large. On the other hand, as shown in FIG. 3B, when the insulating sheet 30 is arranged between the flexible flat cable 10 and the metal plate 20, the variation in the characteristic impedance of the flexible flat cable 10 is different from that in the case of single use. It was almost the same.

FIG. 8A is an impedance characteristic diagram when the flexible flat cable 10 having a conductor 13 thickness of 35 μm is used alone away from the metal product, FFC shows the part of the flexible flat cable, and ε is the impedance value difference. Is shown. FIG. 8 (B) is an impedance characteristic diagram when two flexible flat cables 10 of FIG. 8 (A) are stacked, and FIG. 8 (C) shows two flexible flat cables as shown in FIG. 5 (A). It is an impedance characteristic diagram when the insulating sheet 30 is arranged between 10a and 10b. Each ε indicates the impedance value difference. As the insulating sheet 30, a foamed polypropylene resin having a thickness of 0.2 mm was used. As shown in FIG. 8, it was found that when the insulating sheet 30 was arranged between the two flexible flat cables, the impedance value difference was the same as when used alone.

FIG. 9A is an impedance characteristic diagram when the flexible flat cable 10 having a conductor 13 having a thickness of 75 μm is used in a single motion away from the metal product. 9 (B) is an impedance characteristic diagram when two flexible flat cables 10 of FIG. 9 (A) are stacked, and FIG. 9 (C) is a diagram of two flexible flat cables as shown in FIG. 5 (A). It is an impedance characteristic diagram when the insulating sheet 30 is arranged between 10a and 10b. As the insulating sheet 30, a foamed polypropylene resin having a thickness of 0.2 mm was used. FIG. 9C shows that when the insulating sheet 30 is arranged between the two flexible flat cables, the impedance value difference is the same as when used alone.

FIG. 10A is an impedance characteristic diagram when a flexible flat cable 10 having a conductor 13 thickness of 75 μm is placed in contact with a copper foil having a thickness of 150 μm, as in the case shown in FIG. FIG. 10B is an impedance characteristic diagram when an insulating sheet is arranged between the flexible flat cable and the copper foil. As shown in FIG. 10, when the flexible flat cable 10 is arranged on the copper foil, the impedance value difference becomes large, whereas when the insulating sheet 30 is arranged between the flexible flat cable and the copper foil, the impedance value difference ε becomes large. Could be reduced to.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof.

The flexible flat cable arrangement structure of the present invention can be used not only as an arrangement of internal wiring materials for electronic device products but also as a connection wiring material between electronic device products.

10, 10a, 10b Flexible flat cable 11 Longitudinal center 12 End 13 Conductor 14 Insulator layer 15 Ground plate 16 Adjuster layer 17 Shield layer 18 Reinforcing plate 20 Metal plate 30 Insulation sheet

Claims (4)

It is a flexible flat cable arrangement structure in which the flexible flat cable is arranged close to the conductor.
A flexible flat characterized by arranging an insulating sheet that suppresses variation in the characteristic impedance of a signal flowing through an electric wire of the flexible flat cable due to the dielectric constant of the conductor between the flexible flat cable and the metal material. Cable placement structure. It is a flexible flat cable arrangement structure in which multiple flexible flat cables are stacked and arranged.
An insulating sheet that suppresses the characteristic impedance of the signal flowing through one electric wire of the two adjacent flexible flat cables from varying due to the dielectric constant of the other electric wire is arranged between the two adjacent flexible flat cables. Flexible flat cable arrangement structure featuring. It is a flexible flat cable arrangement structure in which the flexible flat cable is arranged along the metal parts.
A flexible flat cable is characterized in that an insulating sheet that suppresses variation in the characteristic impedance of a signal flowing through an electric wire due to the dielectric constant of the metal component is arranged between the flexible flat cable and the metal member. Flat cable layout structure. The arrangement structure of the flexible flat cable according to any one of claims 1 to 3, wherein the insulating sheet is arranged at least corresponding to the position of a signal flowing through an electric wire among the flexible flat cables.

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