JP2023141622A - flat cable - Google Patents

Abstract

To provide a flat cable that is small and is applicable for high speed transmission.SOLUTION: A flat cable 100 includes: a plurality of coaxial wires 1, each of which includes, as an outermost layer, a shield layer 4 in which surroundings of a served shield part 41 are coated with a batch plating part 42 composed of molten plating; and a coating part 10 that coats in one batch surroundings of the plurality of coaxial wires 1 arranged in parallel.SELECTED DRAWING: Figure 1

Description

The present invention relates to a flat cable.

Patent Document 1 discloses a flat cable in which a plurality of coaxial wires each having an outer conductor as the outermost layer are arranged in parallel and the periphery of the coaxial wires is collectively covered with a jacket.

Japanese Patent Application Publication No. 2-142019

In recent years, with the miniaturization of electronic devices such as tablets and notebook computers, the wiring space within these electronic devices has become extremely small. Signal transmission within these electronic devices is also required to be extremely fast. Therefore, flat cables used as internal wiring of these electronic devices are also required to be small and capable of high-speed transmission.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a flat cable that is small in size and capable of supporting high-speed transmission.

In order to solve the above-mentioned problems, the present invention provides a plurality of coaxial wires in which a shield layer is provided as the outermost layer, and a shield layer is formed by covering the periphery of a horizontally wound shield part with a bulk plating part made of hot-dip plating. A flat cable is provided, comprising a covering part that collectively covers the periphery of the plurality of coaxial wires arranged.

According to the present invention, it is possible to provide a flat cable that is small and compatible with high-speed transmission.

1 is a diagram showing a flat cable according to an embodiment of the present invention, in which (a) is a plan view and (b) is a cross-sectional view taken along the line AA in (a). FIG. 4 is a diagram showing a coaxial line, in which (a) is a sectional view showing a cross section perpendicular to the longitudinal direction, and (b) is an enlarged view of a part of (a). (a) to (c) are plan views showing modified examples of the flat cable.

[Embodiment]
Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Flat cable 100)
FIG. 1 is a diagram showing a flat cable 100 according to the present embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along the line AA in (a). The flat cable 100 is used, for example, as internal wiring for small electronic devices such as tablets and notebook computers.

As shown in FIGS. 1(a) and 1(b), the flat cable 100 includes a plurality of coaxial wires 1 arranged in parallel in the width direction perpendicular to the longitudinal direction, and a periphery of the plurality of coaxial wires 1. A covering part 10 that collectively covers the.

Although the present embodiment shows a case where the flat cable 100 is configured using five coaxial wires 1, the number of coaxial wires 1 is not limited to this. In the flat cable 100 according to the present embodiment, adjacent coaxial wires 1 of the plurality of coaxial wires 1 are in contact with each other (shield layers 4 are in contact with each other, more specifically, collective plating portions 42 to be described later are in contact with each other). ) are placed closely together.

Connectors 101 are provided at both ends of the flat cable 100, respectively. Note that the present invention is not limited to this, and for example, a substrate having an edge connector or the like may be connected to the end of the flat cable 100. In addition, the connectors 101 connected to both ends of the flat cable 100 are not limited to the case where all of the plurality of coaxial lines 1 are connected to one connector 101 as shown in FIG. 1(a). A connection structure may be used in which one or more coaxial wires 1 are connected to each of the plurality of connectors 101 at one end or both ends of the cable 100. For example, at one end of the flat cable 100, all of the multiple coaxial wires 1 are connected to one connector 101, and at the other end of the flat cable 100, all of the multiple coaxial wires 1 are connected to one connector 101. A connection structure may be used in which a predetermined number (one or more) of connectors are connected to different connectors 101.

(coaxial line 1)
FIG. 2 is a diagram showing the coaxial line 1, in which (a) is a sectional view showing a cross section perpendicular to the longitudinal direction, and (b) is a partially enlarged view of (a). As shown in FIGS. 2(a) and 2(b), the coaxial line 1 includes a conductor 2, an insulator 3 surrounding the conductor 2, and a shield layer 4 surrounding the insulator 3. There is. The coaxial line 1 does not have a sheath (or jacket), and the shield layer 4 is the outermost layer of the coaxial line 1.

The conductor 2 is made of a stranded conductor in which a plurality of metal wires 21 are twisted together. For example, it is possible to use a conductor 2 made by twisting together seven metal wires 21 made of annealed copper wire with an outer diameter of 0.023 mm. Note that the present invention is not limited to this, and as the conductor 2, it is also possible to use a compressed stranded conductor in which the metal wires 21 are twisted together and then compressed so that the cross-sectional shape perpendicular to the longitudinal direction of the cable becomes circular. . By using a compressed stranded wire conductor as the conductor 2, conductivity is improved and good transmission characteristics are obtained, and bendability can also be maintained. In addition, the metal wire 21 may be made of tin (Sn), silver (Ag), indium (In), titanium (Ti), magnesium (Mg), iron (Fe, etc.) from the viewpoint of improving electrical conductivity and mechanical strength. It may be a copper alloy wire containing.

The insulator 3 is made of, for example, a fluororesin such as PFA (tetrafluoroethylene/perfluoroalkoxyethylene copolymer) or FEP (tetrafluoroethylene/hexafluoropropylene copolymer), polyethylene, polypropylene, or the like. The insulator 3 may be made of a foamed resin or may be made of a crosslinked resin to improve heat resistance. Furthermore, the insulator 3 may have a multilayer structure. For example, a first non-foamed layer made of non-foamed polyethylene, polypropylene, fluororesin, etc. is provided around the conductor 2, a foamed layer made of foamed polyethylene, foamed polypropylene, etc. is provided around the first non-foamed layer, and the foamed layer is It is also possible to have a three-layer structure in which a second non-foamed layer made of non-foamed polyethylene, polypropylene, etc. is provided around the second non-foamed layer. Because the insulator 3 has such a three-layer structure, cracks are less likely to occur in the insulator 3 when the flat cable 100 is wired in a bent state in an electronic device with a very small wiring space. Therefore, it is compact and effective for high-speed transmission. In addition, when using the above-mentioned three-layer structure, it is preferable that the thickness of the first non-foamed layer is smaller than the thickness of each of the foamed layer and the second non-foamed layer. In this embodiment, an insulator 3 made of FEP is formed around the conductor 2 by tube extrusion. By forming the insulator 3 by tube extrusion, the insulator 3 can be easily peeled off from the conductor 2 during terminal processing, and the terminal processing properties are improved.

(Shield layer 4)
In the coaxial line 1 according to the present embodiment, the shield layer 4 includes a horizontally wound shield part 41 in which a plurality of metal wires 411 are spirally wound so as to cover the periphery of the insulator 3, and a horizontally wound shield part 41. It has a conductive bulk plating part 42 made of hot-dip plating, which is provided so as to collectively cover the entire periphery of the plate.

In this embodiment, since the metal wire 411 is fixed by the bulk plating portion 42, in order to ensure the ease of bending the coaxial wire 1, the metal wire 411 has a low yield strength that is easily plastically deformed. It is necessary to use materials made of suitable materials. More specifically, the metal wire 411 preferably has a tensile strength of 200 MPa or more and 380 Pa or less, and an elongation of 7% or more and 20% or less.

In this embodiment, as the metal wire 411, a silver-plated annealed copper wire having a plating layer 411b made of silver around a metal wire 411a made of an annealed copper wire is used. Note that the metal wire 411a is not limited to an annealed copper wire, but may also be a copper alloy wire, an aluminum wire, an aluminum alloy wire, or a wire with a low softening temperature made by adding a small amount of metal elements (for example, titanium, magnesium, etc.) to pure copper. Can be used. Further, the metal forming the plating layer 411b is not limited to silver, and may be, for example, tin or gold. However, in order to improve the electrical characteristics of the coaxial line 1, it is desirable that the plating layer 411b has a high electrical conductivity, and it is desirable to use a material that has a higher electrical conductivity than at least the bulk plating portion 42. In other words, it is more preferable to use the plating layer 411b made of silver with high conductivity.

Furthermore, in this embodiment, the bulk plating portion 42 made of hot-dip plating is made of tin. However, the present invention is not limited to this, and materials made of, for example, silver, gold, copper, zinc, etc. can be used as the bulk plating portion 42. However, from the viewpoint of ease of manufacture, it is more preferable to use the batch-plated portion 42 made of tin.

When forming the bulk plating part 42, first, the cable base with the horizontally wound shield part 41 formed around the insulator 3 is introduced into a flux bath, and molten tin is applied around the horizontally wound shield part 41. Flux is applied to make it easier to adhere all at once. Flux, for example, has chlorine and zinc as its main components. Further, as the flux, for example, rosin-based flux or the like can be used. After that, the cable base that has passed through the flux tank is introduced into a plating tank that stores tin melted at a temperature of 230° C. or higher and lower than 300° C., and then passed through a die. When the tin remaining after passing through the die is cooled, a batch plating portion 42 is formed. That is, the bulk plating portion 42 is a hot-dip plating layer formed by hot-dip plating.

When forming the bulk plating section 42, the silver constituting the plating layer 411b in the portion that comes into contact with molten tin (that is, hot-dip plating) diffuses into the tin in the plating bath, and the metal wire 411 and the bulk plating section 42 are bonded together. An intermetallic compound 411c containing copper and tin is formed between the metal wire 411a and the bulk plating portion 42 (that is, the portion that is in contact with the surface of the metal wire 411a). When the present inventors performed EDX analysis (analysis by energy dispersive X-ray spectroscopy) using a SEM (scanning electron microscope), it was found that It was confirmed that an intermetallic compound 411c consisting of copper and tin existed in a layered form between the two layers. In other words, the intermetallic compound 411c is formed by a metallic diffusion reaction between the metal element (tin, etc.) that constitutes the hot-dipped hot-dip plating portion 42 and the metal element (copper, etc.) that constitutes the main component of the metal wire 411. A compound layer is formed on the surface of the metal wire 411. The thickness of the intermetallic compound 411c layer is, for example, about 0.2 μm to 1.5 μm. Note that although it is thought that the intermetallic compound 411c contains silver that constitutes the plating layer 411b, the content of silver in the intermetallic compound 411c is so small that it is difficult to detect by EDX analysis.

In the shield layer 4, an intermetallic compound 411c is formed between the metal wire 411 and the bulk plating portion 42, so that when the coaxial wire 1 (flat cable 100) is repeatedly bent or twisted, the metal The bulk plating portion 42 is less likely to peel off from the surface of the metal wire 411, and a gap is less likely to occur between the metal wire 411 and the bulk plating portion 42. As a result, even when bending or twisting is applied, the horizontally wound shield part 41 can be kept fixed by the bulk plating part 42 from the outside of the horizontally wound shield part 41, and the distance between the shield layer 4 and the conductor 2 can be maintained. becomes difficult to change. Therefore, the shielding effect is less likely to deteriorate due to bending or twisting, and rapid attenuation in a predetermined frequency band is less likely to occur. The thickness of the layer of the intermetallic compound 411c is determined by observing a cross section of the coaxial line 1 (a cross section perpendicular to the longitudinal direction of the coaxial line 1) using, for example, an optical microscope or an electron microscope.

A plating layer 411b made of silver remains on a portion of the metal wire 411 that does not come into contact with the bulk plating portion 42 (a portion of the metal wire 411 that does not come into contact with molten tin during plating). That is, the plating layer 411b made of silver remains on the metal wire 411 at the inner side (the insulator 3 side) in the cable radial direction. That is, in the shield layer 4 of the coaxial line 1 according to the present embodiment, the plurality of metal wires 411 are covered with the bulk plating portion 42 rather than the outer peripheral portion 4a where the plurality of metal wires 411 are covered with the bulk plating portion 42. The conductivity of the inner circumferential portion 4b where the plating layer 411b is not covered and the plating layer 411b is exposed is high. In the transmission of high-frequency signals, current concentrates on the insulator 3 side of the shield layer 4, so the presence of the plating layer 411b, which has high conductivity such as silver, on the inner circumferential portion 4b of the shield layer 4 prevents the shield layer from forming. It becomes possible to suppress the decrease in the conductivity of No. 4 and maintain good attenuation characteristics. The conductivity of the tin plating constituting the bulk plating portion 42 is 15% IACS, and the conductivity of the silver plating constituting the plating layer 411b is 108% IACS.

The outer peripheral portion 4a referred to herein is a portion where the metal wire 411 comes into contact with molten plating (tin, etc.) during hot-dip plating (that is, a portion where the intermetallic compound 411c is formed). Further, the inner peripheral portion 4b is a portion where a plating layer 411b made of silver plating or the like remains.

Furthermore, when forming the batch plating section 42, the strain (residual strain) of the metal wire 411 constituting the horizontally wound shield section 41 is removed by passing the high temperature molten tin through a plating bath. As a result, the force of untwisting is removed, and the shape of the metal wire 411 is stabilized. As a result, the coaxial line 1 becomes more flexible and easier to bend, and the flexibility of the flat cable 100 is improved. Further, by removing the strain (residual strain) of the metal wire 411 constituting the horizontally wound shield portion 41, it is possible to suppress twisting of the flat cable 100 due to the influence of the strain (residual strain). Conventionally, in order to suppress such twisting, it was necessary to take measures such as arranging the coaxial wires 1 in which the metal wires 411 were wound in different directions alternately, but according to the present embodiment, all the coaxial wires 1 Even if the method of winding the metal wire 411 in the wire 1 is the same, twisting due to the influence of strain (residual strain) can be suppressed, and the flat cable 100 can be manufactured easily.

The shield layer 4 has a spaced apart portion where metal wires adjacent to each other in the circumferential direction are spaced apart from each other. Note that all the metal wires 411 do not need to be separated, and there may be a contact portion where some of the metal wires 411 adjacent in the circumferential direction are in contact with each other. In addition, in the contact portion, on the outer periphery of the horizontally wound shield portion 41, there is a filling portion in which the spaces between the metal wires 411 adjacent to each other in the circumferential direction are filled with the bulk plating portion 42.

The shield layer 4 has a connecting portion 43 in which metal wires 411 adjacent to each other in the circumferential direction are connected to each other by a bulk plating portion 42. It is desirable that the bulk plating portion 42 be provided so as to collectively cover the entire circumference of the horizontally wound shield portion 41 in the circumferential direction and the axial direction, and to connect the plurality of metal wires 411 mechanically and electrically. In the shield layer 4 of the coaxial line 1, a connecting portion 43 is provided between adjacent inner peripheral portions 4b. Since the periphery of the inner circumferential portion 4b is not covered by the bulk plating portion 42, the inner circumferential portions 4b of adjacent metal wires 411 and the outer surface of the insulator 3 and the bulk plating portion 42 (the connecting portion 43 ) There is an air layer between the inner surface of the

By having the connecting portion 43, the collective plating portion 42 is less likely to crack or peel off when bending or twisting is applied, for example, compared to a case where all metal wires 411 adjacent in the circumferential direction are in contact with each other. In other words, the connecting portion 43 in which the separated parts of the metal wires 411 are connected by the bulk plating portion 42 is composed only of the bulk plating portion 42 made of hot-dip plating that is more flexible than the metal wires 411. . When bending or twisting is applied, the collectively plated portions 42 of the connecting portions act to expand, improving the flexibility of the shield layer 4 as a whole. This makes it difficult for the bulk plated portion 42 to crack or peel off when bending or twisting is applied. Note that the distance between the metal wires 411 adjacent to each other in the circumferential direction is such that the shortest distance from the surface of one metal wire 411 to the other metal wire 411 is less than half the outer diameter of the metal wire 411. Therefore, the above-mentioned effects can be easily obtained.

Furthermore, since the shield layer 4 of each coaxial line 1 constituting the flat cable 100 has the connecting portion 43, when the flat cable 100 is bent, it becomes easier to maintain the bent shape. As a result, it becomes possible to wire the flat cable 100 by bending the flat cable 100 in advance into a shape along the wiring route, thereby improving wiring performance.

Further, the thickness W along the radial direction of the bulk plating portion 42 in the connecting portion 43 (the minimum linear distance from the inner surface to the outer surface of the bulk plating portion 42 in the connecting portion 43) is, for example, the outer diameter of the metal wire 411. If the diameter is 30% (0.3×d) or more of d, cracks in the collectively plated portion 42 are less likely to occur. In particular, when the thickness W of the bulk plating portion 42 in the connecting portion 43 is the same as or larger than the outer diameter (diameter) d of the metal wire 411, the bonding strength between the metal wires 411 increases, Furthermore, cracks are less likely to occur. The upper limit of the thickness W of the bulk plating portion 42 in the connecting portion 43 is preferably 130% (1.3×d) of the outer diameter d of the metal wire 411, for example. The thickness W of the connecting portion 43 and the outer diameter d of the metal wire 411 can be determined by observing a cross section of the coaxial line 1 (a cross section perpendicular to the longitudinal direction of the coaxial line 1) using, for example, an optical microscope or an electron microscope. It is required by

For example, if the shield layer 4 is composed of only the horizontally wound shield portions 41, gaps will occur between the metal wires 411, resulting in a decrease in noise characteristics. Furthermore, due to the influence of the gap created between the metal wires 411, a phenomenon called suckout occurs in which rapid attenuation occurs in a predetermined frequency band (for example, a band of 10 GHz to 25 GHz). As in this embodiment, by providing the bulk plating portion 42 made of hot-dip plating so as to cover the entire circumference of the horizontally wound shield portion 41, the gap between the metal wires 411 can be closed by the bulk plating portion 42. , the shielding effect can be improved. This makes signal transmission loss less likely to occur. Furthermore, by eliminating the gaps between the metal wires 411, it is possible to suppress the occurrence of suckout.

Furthermore, by providing the bulk plating part 42 so as to cover the circumference of the horizontally wound shield part 41, the coating part 10 is removed at the terminal part when processing the terminal of the flat cable 100, that is, when connecting to the connector 101, and the shield layer 42 is removed. When the metal wire 411 is exposed, it becomes difficult to unravel, and the terminal processing and connection to the connector 101 can be easily performed. Furthermore, by providing the bulk plating part 42 so as to cover the periphery of the horizontally wound shield part 41, it is also possible to stably maintain the impedance constant in the longitudinal direction of the cable.

When using the flat cable 100 as internal wiring for electronic equipment, it is required to be thinner, so the outer diameter of the coaxial line 1 (that is, the outer diameter up to the outermost shield layer 4) should be 0.1 mm or more. It is good if it is 0.3 mm or less, and more preferably 0.1 mm or more and 0.2 mm or less. Note that it is technically difficult to manufacture the coaxial wire 1 with an outer diameter of less than 0.1 mm. In this embodiment, the outer diameter of the coaxial line 1 is 0.16 mm. By having such an outer diameter, the coaxial line 1 can be made into a flat cable that is wired inside a small electronic device with a very small wiring space.

(Thickness of bulk plating part 42)
The coaxial wire 1 according to the present embodiment has the coaxial The following formula (1) is applied over the entire circumference of line 1.
t<0.5d...(1)
is met. This prevents the thickness t of the bulk plating portion 42 from becoming non-uniform in the circumferential direction of the coaxial line 1 and the longitudinal direction of the coaxial line 1 (that is, the variation in the thickness t is within a range of less than 0.5 d). ), and the strain applied to the horizontally wound shield portion 41 when the coaxial line 1 is bent is suppressed from becoming non-uniform. As a result, it becomes possible to suppress variations in the flexibility and bending characteristics of the coaxial line 1 (variations in each bending direction and variations in the longitudinal direction of the coaxial line 1).

Further, by setting the thickness t of the bulk plating portion 42 to be less than 0.5 d, the strain εs loaded on the surface of the shield layer 4 is reduced, so that the flexibility of the coaxial line 1 can be improved. Further, even when the coaxial line 1 is repeatedly bent, the bending life can be extended (that is, the shield layer 4 is less likely to be destroyed by repeated bending). Note that the strain εs loaded on the surface of the shield layer 4 is expressed by the following formula (2).
εs=(t+d)/(2・R)...(2)
However, d: diameter of metal wire 411 (thickness of horizontally wound shield part 41)
R: Represented by bending radius.

Furthermore, by making the thickness t of the batch plating part 42 as thin as less than 0.5d, cracks are less likely to occur in the batch plating part 42 when the coaxial line 1 is bent with a small bending radius. The thickness t of the bulk plating portion 42 refers to the thickness of the bulk plating portion 42 located radially outward from the horizontally wound shield portion 41 (metal wire 411). It means the thickness along the radial direction of the coaxial line 1 from the outermost position in the radial direction of the coaxial line 1 (the farthest position from the center of the coaxial line 1) among the outer surfaces of the coaxial line 1. That is, the thickness t of the bulk plating portion 42 indicates the thickness of the bulk plating portion 42 at the thinnest portion around the metal wire 411.

Note that if the metal wire 411 is not covered by the bulk plating portion 42, there is a risk that the transmission characteristics will be adversely affected, so it is desirable that the thickness t of the bulk plating portion 42 is greater than 0. Formula (3) below throughout the entire circumference
0<t<0.5d...(3)
It is more desirable to satisfy the following.

(Coating part 10)
The covering portion 10 covers the periphery of the plurality of coaxial wires 1 to protect the coaxial wires 1 and serves to insulate the shield layer 4 from being electrically connected to surrounding members. In this embodiment, the covering section 10 includes a pair of coaxial wires 1 provided to sandwich the plurality of coaxial wires 1 in the thickness direction perpendicular to the longitudinal direction and arrangement direction (width direction) of the plurality of coaxial wires 1. It consists of a film member 11. Here, the film member 11 includes a resin layer made of an insulating resin such as PET (polyethylene terephthalate) or PI (polyimide), and an adhesive layer made of a hot melt adhesive provided on one surface of the resin layer. A laminated tape with

By sandwiching a plurality of coaxial wires 1 between a pair of film members 11 with the adhesive layer on the inside (on the coaxial wire 1 side) and heating them while pressed (for example, sandwiched between a pair of rollers), the pair of film members 11 is adhesively fixed to a plurality of coaxial lines 1. The film member 11 located between adjacent coaxial lines 1 slightly enters the space between adjacent coaxial lines 1 and has a concave shape. Further, at the widthwise end portions, the pair of film members 11 are in direct contact and adhesively fixed to each other. Note that, for example, if the outermost layer of the coaxial wire 1 is a sheath made of fluororesin or the like, there is a risk that the film member 11 cannot be bonded sufficiently. Since the portion 42 comes into contact with the film member 11, it is possible to adhere the film member 11 sufficiently firmly.

In order to make the flat cable 100 thinner, the thickness of the film member 11 is preferably 15 μm or less. In order for the film member 11 to sufficiently fulfill its role as a protective layer and an insulating layer, the thickness of the film member 11 is preferably 4 μm or more. That is, the thickness of the film member 11 is preferably 4 μm or more and 15 μm or less.

(Modified example)
In this embodiment, as shown in FIG. 1(a), a plurality of coaxial lines 1 are arranged parallel to each other, and adjacent coaxial lines 1 (shield layers 4) are arranged in contact with each other. did. However, the present invention is not limited to this. For example, as shown in FIG. It may be configured to be adjusted according to the position, etc. By bringing all the coaxial lines 1 into contact with each other as shown in Figures 1(a) and 3(a), the width of the flat cable 100 can be made the narrowest, allowing wiring even in narrow wiring spaces. become. Furthermore, when all the coaxial lines 1 are brought into contact with each other, the shield layers 4 of all the coaxial lines 1 are electrically connected and have the same ground potential, thereby further improving noise resistance.

In addition, as shown in FIG. 3(b), each coaxial wire 1 is spaced apart along the width direction of the flat cable 100 (with an air layer of a predetermined width in between) so that adjacent coaxial wires 1 do not come into contact with each other. ) may be arranged so as to be spaced apart from each other. In particular, the configuration shown in FIG. 3(b) is effective when each coaxial line 1 transmits completely different signals and it is desired to suppress interference between the coaxial lines 1.

Alternatively, as shown in FIG. 3(c), a plurality of coaxial wires 1 may be divided into a plurality of groups, the coaxial wires 1 of each group may be brought into contact with each other, and the coaxial wires 1 of different groups may be spaced apart. . This makes it possible, for example, to separate a group of coaxial lines 1 used as signal lines and a group of coaxial lines 1 used as power lines so that they do not interfere with each other. Further, at one end or both ends of the flat cable 100, a group of coaxial wires 1 used as signal wires and a group of coaxial wires 1 used as power wires are connected to different connectors 101, respectively. It may also be a structure. For example, at one end of the flat cable 100, all of the plurality of coaxial lines 1 are connected to one connector 101, and at the other end of the flat cable 100, they are separated into signal lines and power lines, and are separated into predetermined lines. The connection structure may be such that each number (one or more) is connected to a different connector 101. At this time, one end of the flat cable 100 is not limited to a connection structure in which all of the plurality of coaxial wires 1 are connected to one connector 101, but is divided into signal wires and power wires and a predetermined number of wires are connected. A connection structure may be used in which each (one or more) connectors are connected to different connectors 101.

Note that during terminal processing when attaching the connector 101, it is desirable to cut and remove the shield layer 4 of each coaxial line 1 by irradiation with a YAG laser. During irradiation with this YAG laser, in order to prevent the laser beam from transmitting through the insulator 3 and damaging the conductor 2, the color of the insulator 3 is changed to a color that reflects or absorbs the YAG laser (for example, white). , black, yellow, red, blue, etc.) is more desirable.

Further, in the above embodiment, a case has been described in which all the coaxial lines 1 included in the flat cable 100 have the same configuration, but the configurations of the coaxial lines 1 included in the flat cable 100 may be different. For example, the outer diameter of the conductor 2 of the coaxial line 1 used as a power line may be larger than that of the coaxial line 1 used as a signal line. In this case, it is preferable to make the outer diameter of the insulator 3 substantially constant by adjusting the thickness of the insulator 3 so that all the coaxial wires 1 have the same outer diameter. The outer diameters of all coaxial wires 1 should be the same, more specifically, the outer diameters of all coaxial wires 1 should be within ±10% of the reference outer diameter (for example, 0.15 mm). By doing so, it is possible to suppress the problem that only a part of the flat cable 100 is difficult to bend and gets twisted.

(Actions and effects of embodiments)
As explained above, in the flat cable 100 according to the present embodiment, the outermost layer of the coaxial line 1 constituting the flat cable 100 is the shield layer 4, and the shield layer 4 is arranged so as to cover the insulator 3. It has a horizontally wound shield part 41 in which a plurality of metal wires 411 are spirally wound, and a batch plating part 42 made of hot-dip plating that covers the periphery of the horizontally wound shield part 41.

By omitting the sheath of the coaxial line 1 and using the shield layer 4 as the outermost layer, the arrangement pitch of the coaxial line 1 can be narrowed, and the flat cable 100 can be made smaller and thinner. Furthermore, if the size is the same as that of the conventional one, it becomes possible to use a larger number of coaxial lines 1, and high-speed transmission with high-density wiring becomes possible.

If the horizontally wound shield portion 41 is used for the shield layer 4 in order to downsize the flat cable 100 and make it easier to bend, the problem is that the metal wire 411 may unwind during terminal processing or manufacturing. In this embodiment, by providing the bulk plating portion 42, it is possible to suppress the horizontally wound shield portion 41 from unraveling. As a result, a sheath is not required, the outer diameter of the coaxial wire 1 is reduced, and the coaxial wire 1 can be made smaller and thinner, and the metal wire 411 can be coaxially Since the wire 1 can be held, further miniaturization and thinning are possible. Furthermore, in the flat cable 100, work such as preliminary soldering can be omitted when processing the terminal, and workability during processing the terminal is improved.

Further, in the flat cable 100, the bulk plating portion 42 is arranged as the outermost part of the coaxial line 1, and the structure in which the bulk plating portion 42 and the coating portion 10 are in contact with each other allows the flat cable 100 to At a predetermined position that is not at the end in the longitudinal direction, the bulk plating portion 42 can be exposed simply by removing the coating portion 10, and the exposed bulk plating portion 41 can be used to perform horizontal winding without performing preliminary soldering or other work. It is also possible to use a connection structure in which the shield portion 41 is grounded or the like.

In addition, since the shield layer 4 is connected almost all around the circumference via the batch plating part 42, it becomes possible to close the gap between the metal wires 411 of the horizontally wound shield part 41 with the batch plating part 42, which reduces noise. It becomes possible to improve the characteristics and suppress the occurrence of suckout. That is, according to the present embodiment, it is possible to realize a flat cable 100 suitable for high-speed transmission, in which the shielding effect is less likely to deteriorate and rapid attenuation is less likely to occur in a predetermined frequency band (for example, a frequency band up to 26 GHz). .

Furthermore, by having the bulk plated portion 42, it becomes easier to maintain the shape of the flat cable 100 in a bent shape with respect to its width direction and thickness direction. As a result, for example, it becomes possible to attach the flat cable 100 in a pre-bent shape along the wiring route, which facilitates the wiring work.

(Summary of embodiments)
Next, technical ideas understood from the embodiments described above will be described using reference numerals and the like in the embodiments. However, each reference numeral in the following description does not limit the constituent elements in the claims to those specifically shown in the embodiments.

[1] A plurality of coaxial wires (1) in which the outermost layer is provided with a shield layer (4) in which the periphery of the horizontally wound shield part (41) is covered with a bulk plating part (42) made of hot-dip plating, and A flat cable (100) comprising: a covering part (10) that collectively covers the periphery of the plurality of coaxial wires (1) arranged in the coaxial cable (100).

[2] The flat cable (100) according to [1], wherein the coaxial line (1) has an outer diameter of 0.1 μm or more and 0.3 μm or less.

[3] The flat cable (100) according to [1] or [2], wherein the bulk plating portion (42) is made of tin.

[4] The covering portion (10) is provided to sandwich the plurality of coaxial wires (1) in a thickness direction perpendicular to the longitudinal direction and arrangement direction of the plurality of coaxial wires (1). [1] or [1] consisting of a pair of film members (11), the pair of film members (11) being made of insulating resin and adhesively fixed to the plurality of coaxial wires (1); 2] flat cable (100).

[5] The flat cable (100) according to [4], wherein the film member (11) has a thickness of 4 μm or more and 15 μm or less.

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are essential for solving the problems of the invention. Moreover, the present invention can be implemented with appropriate modifications within a range that does not depart from the spirit thereof.

1...Coaxial wire 2...Conductor 3...Insulator 4...Shield layer 41...Horizontally wound shield part 411...Metal wire 42...Batch plating part 10...Coating part 11...Film member 100...Flat cable

Claims (5)

A plurality of coaxial wires each having a shield layer formed as the outermost layer by covering the periphery of the horizontally wound shield part with a bulk plating part made of hot-dip plating;
a covering portion that collectively covers the periphery of the plurality of coaxial wires arranged in parallel;
flat cable. The outer diameter of the coaxial line is 0.1 μm or more and 0.3 μm or less,
The flat cable according to claim 1. the bulk plating portion is made of tin;
The flat cable according to claim 1 or 2. The covering portion is composed of a pair of film members provided to sandwich the plurality of coaxial wires in a thickness direction perpendicular to the longitudinal direction and the arrangement direction of the plurality of coaxial wires,
The pair of film members are made of insulating resin and are adhesively fixed to the plurality of coaxial wires.
The flat cable according to claim 1 or 2. The thickness of the film member is 4 μm or more and 15 μm or less,
The flat cable according to claim 4.

Images