WO2016104066A1

WO2016104066A1 - Signal transmission flat cable

Info

Publication number: WO2016104066A1
Application number: PCT/JP2015/083683
Authority: WO
Inventors: 市毛　敏明
Original assignee: 株式会社湘南合成樹脂製作所; 株式会社テクノ・コア
Priority date: 2014-12-25
Filing date: 2015-12-01
Publication date: 2016-06-30
Also published as: TW201640525A; JPWO2016104066A1

Abstract

Provided is a signal transmission flat cable that is capable of suppressing a decrease in signal transmission characteristics in a high-frequency frequency band. An upper electric insulation thin film layer 4 and a lower electric insulation thin film layer 5 are provided, whereby signal conductors 1, 2 and an electric insulation base body 3 are covered from the top and the bottom in the cable thickness direction. A protective insulation layer 8 comprises a metal layer 6 and an electric insulation plastic layer 7, and surrounds the outer periphery of the upper and lower electric insulation thin film layers in such a manner as to position the metal layer on the inside, and the electric insulation plastic layer on the outside. Grounding of the cable is achieved through the metal layer 6 of the protective insulation layer 8.

Description

Flat cable for signal transmission

The present invention relates to a flat cable for signal transmission that is thin and has excellent electrical characteristics, and more particularly to a flat cable for signal transmission suitable for internal wiring of a mobile phone, a notebook computer, or the like.

Signal transmission flat cables used in high-density wiring electronic devices such as mobile phones and laptop computers are required to be thin and have low transmission loss in the high-frequency band in order to enable wiring in narrow spaces. Is done.

As such a signal transmission flat cable, a signal conductor made of a metal thin film, a ground conductor made of a metal thin film, disposed on both sides of the signal conductor in the cable width direction, and an electric insulating base body laminated with the signal conductor and the ground conductor And an upper insulating thin film layer and a lower electrically insulating thin film layer covering these signal conductor, ground conductor and electric insulating base from above and below in the cable thickness direction, and an electrically insulating plastic layer is laminated on one surface of the metal layer, There has been proposed a coaxial cable provided with an upper insulating thin film layer and a protective shielding layer provided directly on the outer periphery of the lower electrically insulating thin film layer so that the electrically insulating plastic layer is on the outside (Patent Documents 1 and 2). .

In these coaxial cables, the ground conductor made of a metal thin film is formed as a ground pattern and is electrically connected to the metal layer of the protective shielding layer to stabilize the high frequency characteristics.

JP 2011-119198 A Japanese Patent No. 5534628

In the configuration described in

Patent Documents

1 and 2, for grounding the coaxial cable, a ground pattern serving as a ground conductor and a protective shielding layer are provided, and these are grounded to an external ground via a terminal connector portion. is doing. Thus, conventionally, since the ground pattern and the protective shielding layer are provided, the ground pattern is bent at both ends in the width direction for electrical connection thereof, and the bent portion of the protective shielding layer is formed. It was in contact with the metal layer.

However, since the ground pattern is made of copper foil and is extremely thin (about 0.01 mm), it is technically difficult to fold the ground pattern, which is a factor that deteriorates workability.

Also, especially when there are multiple signal conductors (multi-core), a ground conductor is provided between the signal conductors, but the ground conductor between them can be connected to the shield only at the end compared to the ground conductors at both ends. In addition, since the electrical connection is poor, there is a problem that the high-frequency characteristics are not stable and the quality is lowered due to the floating state.

The present invention has been made to solve such problems, and it is an object of the present invention to provide a flat cable for signal transmission that can improve work for grounding and can stabilize high-frequency characteristics.

The present invention which achieves the above-described problems
One or more signal conductors made of a metal thin film extending in the cable length direction;
An electrically insulating substrate on which the signal conductor is laminated;
An upper electrically insulating thin film layer and a lower electrically insulating thin film layer covering the signal conductor and the electrically insulating base from above and below in the cable thickness direction;
A protective shielding layer comprising a metal layer and an electrically insulating plastic layer, and surrounding the outer periphery of the upper electrically insulating thin film layer and the lower electrically insulating thin film layer such that the metal layer is located on the inner side and the electrically insulating plastic layer is located on the outer side. Prepared,
An electrical connection to the ground is made through the metal layer of the protective shielding layer.

In such a configuration, since the grounding is performed through the metal layer of the protective shielding layer, it is not necessary to provide a grounding conductor on the electrically insulating base on which the signal conductors are laminated, and the grounding which has been conventionally required Therefore, the electrical connection work between the grounding conductor and the metal layer of the protective shielding layer is eliminated, and the workability is improved. In addition, the instability of the high frequency characteristics due to the poor electrical connection that occurs during such electrical connection work for grounding is eliminated, and the quality can be improved.

It is the perspective view which showed a part of flat cable for signal transmission of the present invention transversely. It is explanatory drawing explaining the manufacturing method of the flat cable for signal transmission. It is a perspective view which shows the other Example of the flat cable for signal transmission. (A), (b) is a perspective view which shows other Example of the flat cable for signal transmission.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a perspective view showing a part of a flat cable 100 for signal transmission showing an embodiment of the present invention in a crossing manner. The flat cable 100 is configured as a multi-core coaxial cable, and two

signal conductors

1 and 2 made of a metal thin film are disposed on one surface of the electrically insulating base 3 on a plane. The

signal conductors

1 and 2 are arranged extending in the cable length direction in parallel with each other. In FIG. 1, two

signal conductors

1 and 2 are provided. However, the number of signal conductors is not limited to two, and a plurality of signal conductors can be provided.

In this specification, the cable width direction is a direction indicated by W extending in the left-right direction in FIG. 1 in a direction orthogonal to the cable longitudinal direction indicated by L in FIG. 1 in which the signal transmission flat cable 100 extends. The cable thickness direction is a direction indicated by D extending vertically in FIG.

The signal transmission flat cable 100 includes an upper electrically insulating thin film layer 4 and a lower electrically insulating thin film layer 5, and these electrically insulating

thin film layers

4 and 5 connect the

signal conductors

1 and 2 and the electrically insulating substrate 3 in the cable thickness direction. It is provided so as to cover from above and below. In addition, a protective shielding layer 8 in which an electrically insulating plastic layer 7 is laminated on one surface of a metal layer 6 is provided on the outer periphery of the upper electrically insulating thin film layer 4 and the lower electrically insulating thin film layer 5. It is provided as follows.

In this embodiment, the metal layer 6 of the protective shielding layer 8 is grounded to an external ground via a terminal connector (not shown), and the signal transmission flat cable 100 is interposed via the metal layer 6 of the protective shielding layer 8. Electrical connection to ground is made.

The protective shielding layer 8 is formed so as to surround the upper electric insulating thin film layer 4 and the lower electric insulating thin film layer 1 in the cable cross section by making one end face abut the other end edge in the cable longitudinal direction. ing. That is, the protective shielding layer 8 has a butt portion 8a formed by abutting both end edges continuously in the cable longitudinal direction in the vicinity of the upper left corner of the cable cross section.

The protective shielding layer 8 is preferably abutted so that the abutting portion 8a is formed as far away from the

signal conductors

1 and 2 as possible. The butting portion 8a is located at the left end in FIG. 1, but may be located at the right end. In this way, by separating the butting portion 8a from the

signal conductors

1 and 2, the influence on the signal conductor is reduced, and a decrease in signal transmission characteristics in the high frequency band can be suppressed.

In a state where the protective shielding layer 8 in which the metal layer 6 and the electrically insulating plastic layer 7 are laminated and integrated is formed on the outer periphery of the upper electrically insulating thin film layer 4 and the lower electrically insulating thin film layer 5, the protective shielding layer 8 is viewed from above and below. By applying heat and pressure (hot pressing), the upper electric insulating thin film layer 4 and the lower electric insulating thin film layer 5 are softened and melted and integrated with the metal layer 6, thereby causing the protective shielding layer 8 to be deformed. Can be prevented. Further, since both end edges of the protective shielding layer 8 are abutted with each other, the thicknesses of the upper electrically insulating thin film layer 4 and the lower electrically insulating thin film layer 5 at the time of heating and pressing are constant over the entire cable width, and the high frequency frequency It is possible to suppress a decrease in signal transmission characteristics in the band.

The

signal conductors

1 and 2 are made of a highly conductive metal, and specifically, copper (conductivity: 5.76 × 10 ⁷ Siemens / m), which is commonly used as a highly conductive metal industrially. Can be formed by laminating the foil into the electrically insulating thin film layer 4 or the electrically insulating substrate 3 or by depositing or plating copper on the electrically insulating thin film layer 4 or the electrically insulating substrate 3. As the metal other than copper, aluminum (conductivity: 3.96 × 10 ⁷ Siemens / m) can be given.

In electronic devices that transmit high-frequency signals exceeding 2 GHz, such as mobile phones and laptop computers, current concentrates on the surface layer of several microns due to a phenomenon called the skin effect, so that the conductivity is copper or aluminum. Since a smaller plating layer such as nickel increases transmission loss, it is necessary not to form such a plating layer on the surfaces of the

signal conductors

1 and 2.

The metal layer 6 that forms the protective shielding layer 8 is preferably formed of a highly conductive metal such as copper or aluminum, like the signal conductor 1.

In this example, the thickness of the upper electrically insulating thin film layer 4 is 0.125 mm, the thickness of the electrically insulating base 3 is 0.025 mm, and the thickness of the lower electrically insulating thin film layer 5 is 0.100 mm. Single-core coaxial flat for signal transmission having the same signal transmission characteristics as a round coaxial cable with characteristic impedance of 50Ω, with the thicknesses of the upper and lower insulators of

signal conductors

1 and 2 being equal (each 0.125 mm) The cable 100 is realized. A copper-clad laminate obtained by laminating a 0.025 mm thick electrically insulating base and a copper foil is commercially available. By using such a commercially available product, the cost of a flat cable for signal transmission can be reduced. .

The upper electrically insulating thin film layer 4 and the lower electrically insulating thin film layer 5 are made of a thermoplastic resin material having a property of being melt-bonded by heating, and the upper electrically insulating thin film layer 4 and the lower electrically insulating thin film layer 4 are heated by heat applied from the outside of the protective shielding layer 8. By melting and bonding the lower electric insulating thin film layer 5 and the metal layer 6, the upper electric insulating thin film layer 4 and the lower electric insulating thin film layer 5 and the protective shielding layer 8 are hardly peeled off. The upper electric insulating thin film layer 4 and the lower electric insulating thin film layer 5 and the metal layer 6 are directly bonded without an adhesive which causes an increase in transmission loss. Transmission is possible.

The electrically insulating plastic layer 7 is made of polyimide having heat resistance, thin film properties, mechanical strength, and slipperiness. The protective shielding layer 8 is formed by laminating the metal layer 6 on the inner side and the electrically insulating plastic layer 7 on the outer side with an adhesive such as thermoplastic polyimide interposed therebetween. The lower electrically insulating thin film layer 5 is enclosed at once.

The upper electrically insulating thin film layer 4, the lower electrically insulating thin film layer 5 and the electrically insulating substrate 3 have a property of being melt-bonded by heating, and are materials having a low dielectric constant and dielectric loss tangent in a high frequency band exceeding 2 GHz. Preferably, examples of such a material include liquid crystal polymer and polytetrafluoroethylene.

The liquid crystal polymer is a thermoplastic resin that exhibits optical anisotropy when melted. Specifically, it is a fully aromatic or semi-aromatic polyester, polyesterimide, polyesteramide, or a resin composition containing these. Among them, a liquid crystal polyester resin composition having (A) a liquid crystal polyester as a continuous phase and (B) a copolymer having a functional group having reactivity with the liquid crystal polyester as a dispersed phase is preferable.

In the present embodiment, since the grounding is performed through the metal layer 6 of the protective shielding layer 8, it is not necessary to provide the grounding conductor on the electrically insulating base 3 on which the

signal conductors

1 and 2 are laminated. Therefore, the electrical connection work between the grounding conductor for grounding and the metal layer 6 of the protective shielding layer 8 which is conventionally required is eliminated, and the workability is improved. In addition, the instability of the high frequency characteristics due to the poor electrical connection that occurs during such electrical connection work for grounding is eliminated, and the quality can be improved.

Next, a method for manufacturing a flat cable for signal transmission according to this embodiment will be described with reference to FIG. A copper foil C is laminated on the upper surface of the electrically insulating base 3 (FIG. 2A), and the

signal conductors

1 and 2 are formed by etching the copper foil C (FIG. 2B).

Next, the upper electric insulating thin film layer 4 is laminated on the

signal conductors

1 and 2 and the lower electric insulating thin film layer 5 is provided below the electric insulating substrate 3 (FIG. 2 (c)), FIG. 2 (d). As shown in FIG. 4, by covering the outer periphery of the upper electrical insulating thin film layer 4 and the lower electrical insulating thin film layer 5 with a protective shielding layer 8 and applying heat and pressure (hot pressing) from above and below the protective shielding layer 8, The upper electric insulating thin film layer 4 and the lower electric insulating thin film layer 5 are softened and melted and bonded to the metal layer 6 to produce a signal transmission flat cable 100 as shown in FIG.

FIG. 3 shows a signal transmission flat cable 200 configured as a single-core coaxial cable. The configuration is the same as that of the signal transmission flat cable 200 according to the first embodiment, except that one signal conductor 10 is provided on the electrical insulating base 3 at substantially the center in the width direction W. The signal transmission flat cable 200 can be manufactured in the same manner as in the first embodiment by the method shown in FIG.

Also in the second embodiment, no ground conductor is provided on the electrically insulating base 3, and the signal transmission flat cable 200 is electrically connected to the ground via the metal layer 6 of the protective shielding layer 8. Done. Accordingly, it is not necessary to provide a ground conductor on the electrically insulating base 3 as in the first embodiment, so that workability for grounding is improved and high-frequency characteristics can be stabilized and quality can be improved.

4A and 4B show a signal transmission flat cable 300 configured as a multi-core coaxial cable and a signal transmission flat cable 400 configured as a single-core coaxial cable.

In the examples shown in Examples 1 and 2, the protective shielding layer 8 has both end edges continuously abutted in the cable longitudinal direction to form the abutting portion 8a. FIGS. 4 (a) and 4 (b) In the embodiment shown in FIG. 1, one

end edge

6 a, 7 a of each of the metal layer 6 of the protective shielding layer 8 and the electrically insulating plastic layer 7 is overlaid on the other edge of the electrically insulating plastic device 7. Thereby, in the protective shielding layer 8, one end edge portion along the cable longitudinal direction is overlapped on the outer side of the other end edge portion to form an overlapping portion 8a '. In other configurations, the flat cable 300 and the flat cable 400 are the same as the flat cable 100 and the flat cable 200 shown in the first and second embodiments, respectively.

As shown in Examples 1 and 2, in the case where the protective shielding layer 8 is abutted to form the abutting portion 8a, a location where a gap is generated in the width direction of the protective shielding layer 8 may occur at a location where the abutting is insufficient. However, in the example shown in Example 3, since the edge portions of the protective shielding layer 8 are overlapped, there is less possibility that a gap is generated in the width direction, and the cable can be prevented from being deformed. There are advantages.

In Examples 1, 2, and 3, the example in which the flat cable for signal transmission is mainly used for high-density wiring electronic devices such as mobile phones and notebook computers has been described. However, the present invention is not limited to this. For example, the present invention can also be applied to a wire harness in which a plurality of signal conductor wires used for power supply and signal communication of automobiles and other electronic devices are bundled.

1, 2, 10 Signal conductor 3 Electrically insulating base 4 Upper electrically insulating thin film layer 5 Lower electrically insulating thin film layer 6 Metal layer 7 Electrically insulating plastic layer 8 Protective shielding layer 8a Butt portion 8a 'Overlapping portion

Claims

One or more signal conductors made of a metal thin film extending in the cable length direction;
An electrically insulating substrate on which the signal conductor is laminated;
An upper electrically insulating thin film layer and a lower electrically insulating thin film layer covering the signal conductor and the electrically insulating base from above and below in the cable thickness direction;
A protective shielding layer comprising a metal layer and an electrically insulating plastic layer, and surrounding the outer periphery of the upper electrically insulating thin film layer and the lower electrically insulating thin film layer such that the metal layer is located on the inner side and the electrically insulating plastic layer is located on the outer side. Prepared,
A flat cable for signal transmission, wherein electrical connection with a ground is made through a metal layer of the protective shielding layer.
The protective shielding layer is formed at a position where one end edge portion and the other end edge portion along the longitudinal direction of the cable are abutted to surround the outer periphery, and the abutting portion is separated from the position on the signal conductor. The flat cable for signal transmission according to claim 1.
2. The flat cable for signal transmission according to claim 1, wherein the protective shielding layer surrounds the outer periphery with one end edge portion being overlapped with the outside of the other end edge portion in the cable longitudinal direction.
Make the thickness of the upper and lower insulators equal so that the thickness of the upper electrically insulating thin film is equal to the thickness of the electrically insulating substrate plus the thickness of the lower electrically insulating thin film. The flat cable for signal transmission according to any one of claims 1 to 3, wherein the flat cable is for signal transmission.