Flat cable

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

Technical Field

[0001] The present invention relates to a flat cable.

Background Art

[0002] Patent Document 1 discloses a flat cable in which a plurality of coaxial lines having an outer conductor as the outermost layer are arranged in parallel, and the periphery thereof is collectively covered with a jacket.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the miniaturization of electronic devices such as tablets and notebook computers, the wiring space inside these electronic devices has become extremely small. And for signal transmission inside these electronic devices, it has been required to be very fast. Therefore, even in the flat cables used as internal wiring of these electronic devices, it is required to be small and capable of high-speed transmission.

[0005] Therefore, an object of the present invention is to provide a flat cable that is small and capable of high-speed transmission.

Means for Solving the Problems

[0006] The present invention aims to solve the above problems, and provides a flat cable including: a plurality of coaxial lines provided with a shield layer having an outermost layer covered with a collective plating portion made of molten plating around a horizontally wound shield portion; and a covering portion that collectively covers the periphery of the plurality of coaxial lines arranged in parallel.

Effects of the Invention

[0007] According to the present invention, a flat cable that is small and capable of high-speed transmission can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0009] [Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] (Flat Cable 100) FIG. 1 is a diagram showing a flat cable 100 according to the present embodiment, (a) is a plan view, and (b) is a sectional view taken along line A-A of (a). The flat cable 100 is used, for example, as internal wiring for small electronic devices such as tablets and notebook computers.

[0011] As shown in FIGS. 1(a) and 1(b), the flat cable 100 includes a plurality of coaxial lines 1 arranged in parallel in a width direction perpendicular to the longitudinal direction, and a covering portion 10 that collectively covers the periphery of the plurality of coaxial lines 1.

[0012] In this embodiment, although the flat cable 100 is shown as being composed of five coaxial lines 1, the number of coaxial lines 1 is not limited to this. In the flat cable 100 according to this embodiment, a plurality of coaxial lines 1 are closely arranged such that adjacent coaxial lines 1 are in contact with each other (the shield layers 4 are in contact with each other, more specifically, the integrally plated portions 42 described later are in contact with each other).

[0013] Connectors 101 are provided at both ends of the flat cable 100, respectively. Note that this is not the only case. For example, a substrate having an edge connector or the like may be connected to the end of the flat cable 100. Further, 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 in which one or more coaxial lines 1 are connected to each of a plurality of connectors 101 at one end or both ends of the flat cable 100 may also be used. For example, at one end of the flat cable 100, all of the plurality of coaxial lines 1 may be connected to one connector 101, and at the other end of the flat cable 100, a connection structure in which a predetermined number (one or more) of the plurality of coaxial lines 1 are connected to each of different connectors 101 may also be used.

[0014] (Coaxial line 1) Fig. 2 is a diagram showing the coaxial line 1. (a) is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction, and (b) is an enlarged view of a part of (a). As shown in Figs. 2(a) and 2(b), the coaxial line 1 has a conductor 2, an insulator 3 covering the periphery of the conductor 2, and a shield layer 4 covering the periphery of the insulator 3. 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.

[0015] The conductor 2 is composed of a stranded conductor formed by twisting a plurality of metal strands 21. For example, a conductor 2 formed by twisting 7 metal strands 21 made of soft copper wire with an outer diameter of 0.023 mm can be used. Note that the present invention is not limited to this, and as the conductor 2, a compressed stranded conductor obtained by compressing the metal strands 21 after twisting so that the cross-sectional shape perpendicular to the cable longitudinal direction is circular can also be used. By using a compressed stranded conductor as the conductor 2, the conductivity can be improved to obtain good transmission characteristics, and the bendability can also be maintained. Further, from the viewpoint of improving the conductivity and mechanical strength, the metal strand 21 may be a copper alloy wire containing tin (Sn), silver (Ag), indium (In), titanium (Ti), magnesium (Mg), iron (Fe), etc.

[0016] 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 a foamed resin or may be composed of a crosslinked resin to improve heat resistance. Further, 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 a second non-foamed layer made of non-foamed polyethylene, polypropylene, etc. is provided around the foamed layer to form a three-layer structure. Since the insulator 3 has such a three-layer structure, when the flat cable 100 is wired in a bent state in an electronic device with a very small wiring space, cracks are less likely to occur in the insulator 3, so it is effective for miniaturization and high-speed transmission. Note that when the above-described three-layer structure is adopted, the thickness of the first non-foamed layer is preferably smaller than the thicknesses of the foamed layer and the second non-foamed layer, respectively. In the present embodiment, an insulator 3 made of FEP is formed around the conductor 2 by tube extrusion. By forming the insulator 3 by tube extrusion, it becomes easier to peel the insulator 3 from the conductor 2 during terminal processing, and the terminal processability is improved.

[0017] (Shield layer 4) In the coaxial line 1 according to this embodiment, the shield layer 4 includes a horizontally wound shield portion 41 in which a plurality of metal strands 411 are spirally wound so as to cover the periphery of the insulator 3, and a conductive integral plating portion 42 made of fusion plating and provided so as to cover the entire periphery of the horizontally wound shield portion 41.

[0018] In this embodiment, since the metal strands 411 are fixed by the integral plating portion 42, in order to ensure the bendability of the coaxial line 1, it is necessary to use the metal strands 411 made of a material with low strength that is easily plastically deformed. More specifically, as the metal strands 411, those having a tensile strength of 200 MPa or more and 380 Pa or less and an elongation of 7% or more and 20% or less are preferably used.

[0019] In this embodiment, as the metal strands 411, a silver-plated soft copper wire having a plating layer 411b made of silver around a metal wire 411a made of a soft copper wire is used. Note that the metal wire 411a is not limited to a soft copper wire, and a copper alloy wire, an aluminum wire, an aluminum alloy wire, or a wire material with a low softening temperature obtained by adding a small amount of metal elements (for example, titanium, magnesium, etc.) to pure copper can be used. Further, the metal constituting 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 conductivity, and it is preferably made of a material having a higher conductivity than at least the integral plating portion 42. That is, it can be said that it is more preferable to use the plating layer 411b made of silver having a high conductivity.

[0020] Also, in this embodiment, as the integral plating portion 42 made of fusion plating, one made of tin is used. However, it is not limited to this, and as the integral plating portion 42, one made of, for example, silver, gold, copper, zinc, etc. can be used. However, from the viewpoint of ease of manufacture, it can be said that it is more preferable to use the integral plating portion 42 made of tin.

[0021] When forming the lump-sum plated portion 42, first, the cable base having the horizontally wound shield portion 41 formed around the insulator 3 is introduced into a flux tank, and a flux is applied around the horizontally wound shield portion 41 to facilitate the molten tin to adhere to the entire cable. The flux is mainly composed of, for example, chlorine and zinc. For example, a rosin-based flux can be used as the flux. After that, the cable base that has passed through the flux tank is introduced into a plating tank that stores molten tin at a temperature of 230°C or higher and lower than 300°C, and then passed through a die. The tin remaining after passing through the die is cooled to form the lump-sum plated portion 42. That is, the lump-sum plated portion 42 is a hot-dip plating layer formed by hot-dip plating.

[0022] When forming the lump-plated portion 42, the silver constituting the plating layer 411b in the portion in contact with the molten tin (i.e., hot-dip plating) diffuses into the tin in the plating tank, and an intermetallic compound 411c containing copper and tin is formed between the metal wire 411 and the lump-plated portion 42 (i.e., between the metal wire 411a and the lump-plated portion 42 and in the portion 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 an SEM (scanning electron microscope), it was confirmed that the intermetallic compound 411c made of copper and tin exists in a layer on the surface of the metal wire 411 (between the metal wire 411 and the lump-plated portion 42). That is, the intermetallic compound 411c is a compound layer formed on the surface of the metal wire 411 by a metallic diffusion reaction between a metal element (such as tin) constituting the lump-plated portion 42 made of hot-dip plating and a metal element (such as copper) constituting the main component of the metal wire 411. The thickness of the layer of the intermetallic compound 411c is, for example, about 0.2 μm to 1.5 μm. Note that although the intermetallic compound 411c is considered to contain silver that constitutes the plating layer 411b, the amount of silver contained in the intermetallic compound 411c is so small that it is difficult to detect it by EDX analysis.

[0023] When an intermetallic compound 411c is formed between the metal strands 411 and the integral plating portion 42, the integral plating portion 42 is less likely to peel off from the surface of the metal strands 411 and a gap is less likely to occur between the metal strands 411 and the integral plating portion 42 when the coaxial line 1 (flat cable 100) is repeatedly bent or twisted. As a result, even when bending or twisting is applied, the integral plating portion 42 can keep the transverse winding shield portion 41 fixed from the outside of the transverse winding shield portion 41, and the distance between the shield layer 4 and the conductor 2 is less likely to change. Therefore, it is less likely that the shielding effect decreases due to bending or twisting, and it is possible to prevent a sharp attenuation from occurring in a predetermined frequency band. The thickness of the layer of the intermetallic compound 411c can be determined, for example, by observing a cross section of the coaxial line 1 (a cross section perpendicular to the longitudinal direction of the coaxial line 1) using an optical microscope or an electron microscope.

[0024] A plating layer 411b made of silver remains on the metal strands 411 in a portion that does not contact the integral plating portion 42 (the metal strands 411 in a portion that does not contact the molten tin during plating). That is, a plating layer 411b made of silver remains on the metal strands 411 in the inner portion (on the insulator 3 side) in the cable diameter direction. That is, in the shield layer 4 of the coaxial line 1 according to the present embodiment, the conductivity of the inner peripheral portion 4b where the plurality of metal strands 411 are not covered by the integral plating portion 42 and the plating layer 411b is exposed is higher than that of the outer peripheral portion 4a where the plurality of metal strands 411 are covered by the integral plating portion 42. In the transmission of high-frequency signals, since the current concentrates on the insulator 3 side in the shield layer 4, the presence of the plating layer 411b having a high conductivity such as silver in the inner peripheral portion 4b of the shield layer 4 suppresses a decrease in the conductivity of the shield layer 4 and makes it possible to maintain good attenuation characteristics. The conductivity of the tin plating constituting the integral plating portion 42 is 15% IACS, and the conductivity of the silver plating constituting the plating layer 411b is 108% IACS.

[0025] Here, the outer peripheral portion 4a refers to the portion where the metal wire 411 contacts the molten plating (such as tin) during molten plating (i.e., the portion where the intermetallic compound 411c is formed). The inner peripheral portion 4b refers to the portion where the plating layer 411b made of silver plating or the like remains.

[0026] Also, when forming the batch plating portion 42, by passing through a plating bath storing high-temperature molten tin, the strain (residual strain) of the metal wire 411 constituting the horizontally wound shield portion 41 is removed. As a result, the force that tries to untwist is eliminated and the shape of the metal wire 411 becomes stable. Consequently, the coaxial line 1 can be bent more smoothly, and the flexibility of the flat cable 100 is improved. Also, by removing the strain (residual strain) of the metal wire 411 constituting the horizontally wound shield portion 41, it is possible to suppress the occurrence of twisting due to the influence of strain (residual strain) in the flat cable 100. Conventionally, in order to suppress such twisting, measures such as arranging the coaxial lines 1 with different winding directions of the metal wire 411 alternately were necessary. However, according to the present embodiment, even if the winding method of the metal wire 411 is the same for all the coaxial lines 1, it is possible to suppress the twisting due to the influence of strain (residual strain), and the manufacture of the flat cable 100 becomes easier.

[0027] The shield layer 4 has a separated portion where the metal wires adjacent to each other in the circumferential direction are separated. Note that it is not necessary for all the metal wires 411 to be separated, and there may be a contact portion where some of the metal wires 411 adjacent to each other in the circumferential direction are in contact. In the contact portion, on the outer periphery of the horizontally wound shield portion 41, there is a filled portion filled by the batch plating portion 42 between the metal wires 411 adjacent to each other in the circumferential direction.

[0028] And the shield layer 4 has a connecting portion 43 in which the metal strands 411 adjacent to each other in the circumferential direction are connected by a batch plating portion 42. The batch plating portion 42 preferably covers the entire periphery of the circumferentially and axially wound shield portion 41 in a batch so as to mechanically and electrically connect the plurality of metal strands 411. In the shield layer 4 of the coaxial line 1, the connecting portion 43 is provided between the adjacent inner peripheral portions 4b. Since the periphery of the inner peripheral portion 4b is not covered by the batch plating portion 42, an air layer exists between the inner peripheral portions 4b of the adjacent metal strands 411 and between the outer surface of the insulator 3 and the inner surface of the batch plating portion 42 (connecting portion 43).

[0029] By having the connecting portion 43, for example, when compared with the case where all the metal strands 411 adjacent to each other in the circumferential direction are in contact, it becomes difficult for the batch plating portion 42 to crack or peel when bending or twisting is applied. That is, the connecting portion 43 in which the portions where the metal strands 411 are separated from each other are connected by the batch plating portion 42 is composed only of the batch plating portion 42 made of a fusion plating that is more flexible than the metal strands 411. When bending or twisting is applied, the batch plating portion 42 of the connecting portion acts to stretch, and the flexibility of the entire shield layer 4 is improved. As a result, it becomes difficult for the batch plating portion 42 to crack or peel when bending or twisting is applied. Note that when the distance between the metal strands 411 adjacent to each other in the circumferential direction is such that the shortest distance from the surface of one metal strand 411 to the other metal strand 411 is half or less of the outer diameter of the metal strand 411, the above-described effects are easily obtained.

[0030] Furthermore, since each shield layer 4 of the coaxial line 1 constituting the flat cable 100 has the connecting portion 43, when the flat cable 100 is bent, it becomes easy to maintain the shape in the bent state. As a result, it becomes possible to bend the flat cable 100 in a shape along the wiring path in advance and perform the wiring of the flat cable 100, improving the wiring property.

[0031] Also, when the thickness W along the radial direction of the integral plating portion 42 in the connecting portion 43 (the minimum straight-line distance from the inner surface to the outer surface of the integral plating portion 42 in the connecting portion 43) is, for example, 30% (0.3×d) or more of the outer diameter (diameter) d of the metal wire 411, cracking of the integral plating portion 42 is less likely to occur. In particular, when the thickness W of the integral 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, and further cracking is less likely to occur. The upper limit value of the thickness W of the integral plating portion 42 in the connecting portion 43 is, for example, preferably 130% (1.3×d) of the outer diameter d of the metal wire 411. The thickness W of the connecting portion 43 and the outer diameter d of the metal wire 411 can be obtained, for example, by observing a cross-section along the coaxial line 1 (a cross-section perpendicular to the longitudinal direction of the coaxial line 1) using an optical microscope or an electron microscope.

[0032] For example, if the shield layer 4 is composed only of the horizontally wound shield portion 41, gaps will occur between the metal wires 411, resulting in a deterioration of the noise characteristics. Furthermore, due to the influence of the gaps generated between the metal wires 411, a phenomenon called suck-out occurs, in which rapid attenuation occurs in a predetermined frequency band (for example, a band of 10 GHz to 25 GHz). By providing an integral plating portion 42 made of fusion plating so as to cover the entire periphery of the horizontally wound shield portion 41 as in the present embodiment, the integral plating portion 42 can block the gaps between the metal wires 411, improving the shielding effect. As a result, signal transmission loss is less likely to occur. Furthermore, since the gaps between the metal wires 411 are eliminated, it becomes possible to suppress the occurrence of suck-out.

[0033] Furthermore, by providing the integral plating portion 42 so as to cover the periphery of the horizontally wound shield portion 41, when processing the terminal of the flat cable 100, that is, when connecting to the connector 101, when the covering portion 10 is removed and the shield layer 4 is exposed at the terminal portion, the metal wires 411 are less likely to come loose, making it possible to easily perform terminal processing and connection to the connector 101. Moreover, by providing the integral plating portion 42 so as to cover the periphery of the horizontally wound shield portion 41, it is also possible to stably maintain the impedance constant in the longitudinal direction of the cable.

[0034] When the flat cable 100 is used as internal wiring for an electronic device and is required to be thinner, the outer diameter of the coaxial line 1 (that is, the outer diameter up to the shield layer 4 which is the outermost layer) is preferably 0.1 mm or more and 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 a coaxial line 1 with an outer diameter of less than 0.1 mm. In the present 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 in a small electronic device with a very small wiring space.

[0035] (Thickness of the mass plating portion 42) For the coaxial line 1 according to the present embodiment, when the diameter of the metal strand 411 of the horizontally wound shield portion 41 is d and the thickness of the mass plating portion 42 from the outer surface of the metal strand 411 is t, the following formula (1) t < 0.5d ···(1) is satisfied over the entire circumference of the coaxial line 1. As a result, it is possible to suppress the thickness t of the mass plating portion 42 from becoming non-uniform in the circumferential direction of the coaxial line 1 or in the longitudinal direction of the coaxial line 1 (that is, the variation in the thickness t is suppressed within a range of less than 0.5d), and it is possible to suppress the strain applied to the horizontally wound shield portion 41 from becoming non-uniform when the coaxial line 1 is bent. As a result, it is possible to suppress the variation in the flexibility and the variation in the bending characteristics (variation for each bending direction and variation in the longitudinal direction of the coaxial line 1) of the coaxial line 1.

[0036] Further, by making the thickness t of the mass plating portion 42 less than 0.5d, the strain εs applied to the surface of the shield layer 4 becomes small, so that the flexibility of the coaxial line 1 can be improved. Also, the bending life can be extended even when the coaxial line 1 is repeatedly bent (that is, the shield layer 4 is less likely to be broken by repeated bending). Note that the strain εs applied to the surface of the shield layer 4 is given by the following formula (2) εs = (t + d) / (2·R) ···(2) However, d: diameter of the metal strand 411 (thickness of the horizontally wound shield portion 41) R: Bending radius is represented by

[0037] Furthermore, by making the thickness t of the integral plating portion 42 less than 0.5d, when the coaxial line 1 is bent with a small bending radius, cracks are less likely to occur in the integral plating portion 42. Note that the thickness t of the integral plating portion 42 means the thickness of the integral plating portion 42 located radially outward of the horizontally wound shield portion 41 (metal wire 411), and 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 on the outer surface of the metal wire 411 (the position farthest from the center of the coaxial line 1). That is, the thickness t of the integral plating portion 42 indicates the thickness of the integral plating portion 42 at the thinnest portion around the metal wire 411.

[0038] Note that if the metal wire 411 is not covered by the integral plating portion 42, there is a risk of adverse effects on the transmission characteristics. Therefore, it is desirable that the thickness t of the integral plating portion 42 is greater than 0, and the following formula (3) 0 < t < 0.5d ···(3) is more desirably satisfied.

[0039] (Coating portion 10) The coating portion 10 covers the periphery of the plurality of coaxial lines 1, protects the coaxial lines 1, and serves to insulate the shield layer 4 so that it is not electrically connected to surrounding members. In the present embodiment, the coating portion 10 is composed of a pair of film members 11 provided so as to sandwich the plurality of coaxial lines 1 in the thickness direction perpendicular to the longitudinal direction and the arrangement direction (width direction) of the plurality of coaxial lines 1. Here, as the film member 11, a laminate tape having 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 is used.

[0040] With the next layer on the inner side (the coaxial line 1 side), a plurality of coaxial lines 1 are sandwiched between a pair of film members 11 and heated in a pressed state (for example, a state sandwiched between a pair of rollers), so that the pair of film members 11 are adhesively fixed to the plurality of coaxial lines 1. The film member 11 located between adjacent coaxial lines 1 is slightly recessed into the space between the adjacent coaxial lines 1. Also, at the end portions in the width direction, 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 line 1 is a sheath made of a fluororesin or the like, there is a possibility that the film member 11 cannot be sufficiently adhered. However, in this embodiment, since the coaxial line 1 comes into contact with the film member 11 at the integral plating portion 42 made of metal, the film member 11 can be adhered sufficiently firmly.

[0041] In order to make the flat cable 100 thinner, the thickness of the film member 11 is preferably 15 μm or less. And in order for the film member 11 to sufficiently serve 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.

[0042] (Modification example) In this embodiment, as shown in FIG. 1(a), a plurality of coaxial lines 1 are arranged so as to be parallel to each other and adjacent coaxial lines 1 (shield layers 4) are in contact with each other. However, it is not limited to this. For example, as shown in FIG. 3(a), the coaxial lines 1 may be separated from each other near the longitudinal end portion of the flat cable 100, and the distance between the coaxial lines 1 may be adjusted according to the position of the electrodes of the connector 101 or the like. By bringing all the coaxial lines 1 into contact with each other as shown in FIG. 1(a) or FIG. 3(a), the width of the flat cable 100 can be made the narrowest, and wiring can be performed even in a narrow wiring space. 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, so that the noise resistance is further improved.

[0043] Further, as shown in Fig. 3(b), each coaxial line 1 may be arranged at intervals (with a predetermined-width air layer in between) along the width direction of the flat cable 100 so that adjacent coaxial lines 1 do not come into contact with each other. In particular, when completely different signals are transmitted on each coaxial line 1 and interference between the coaxial lines 1 is to be suppressed, the configuration of Fig. 3(b) is effective.

[0044] Also, as shown in Fig. 3(c), a plurality of coaxial lines 1 may be divided into a plurality of groups, the coaxial lines 1 in each group may be brought into contact with each other, and the coaxial lines 1 in different groups may be separated from each other. Thereby, for example, it is possible 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 interference does not occur between them. Further, at one end or both ends of the flat cable 100, the flat cable 100 may have a connection structure in which each of a group of coaxial lines 1 used as signal lines and a group of coaxial lines 1 used as power lines is connected to a different connector 101. For example, at one end of the flat cable 100, all of a plurality of coaxial lines 1 may be connected to one connector 101, and at the other end of the flat cable 100, the flat cable 100 may have a connection structure in which the flat cable 100 is divided into signal lines and power lines and is connected to different connectors 101 for each predetermined number (one or more). At this time, one end of the flat cable 100 is not limited to a connection structure in which all of a plurality of coaxial lines 1 are connected to one connector 101, and may also have a connection structure in which the flat cable 100 is divided into signal lines and power lines and is connected to different connectors 101 for each predetermined number (one or more).

[0045] 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 irradiating it with a YAG laser. In order to suppress the laser light from passing through the insulator 3 and damaging the conductor 2 during the irradiation of this YAG laser, it is more desirable that the color of the insulator 3 be a color that reflects or absorbs the YAG laser (for example, white, black, yellow, red, blue, etc.).

[0046] In the above-described embodiment, the case where all the coaxial lines 1 included in the flat cable 100 have the same configuration has been described. However, 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, by adjusting the thickness of the insulator 3, the outer diameter of the insulator 3 can be made substantially constant, and the outer diameters of all the coaxial lines 1 can be made uniform. Making the outer diameters of all the coaxial lines 1 uniform, more specifically, by setting the outer diameters of all the coaxial lines 1 within the range of ±10% of a reference outer diameter (for example, 0.15 mm), it is possible to suppress problems such as only a part of the flat cable 100 being difficult to bend and being twisted.

[0047] (Functions and Effects of the Embodiment) As described 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 has a horizontally wound shield portion 41 in which a plurality of metal strands 411 are spirally wound so as to cover the periphery of the insulator 3, and a batch plating portion 42 made of molten plating that covers the periphery of the horizontally wound shield portion 41.

[0048] By omitting the sheath of the coaxial line 1 and making the outermost layer the shield layer 4, the arrangement pitch of the coaxial line 1 can be narrowed, and the flat cable 100 can be miniaturized and thinned. Also, when the size is the same as that of the conventional one, it is possible to increase the number of coaxial lines 1 used, and high-speed transmission by high-density wiring becomes possible.

[0049] When the horizontally wound shield portion 41 is used for the shield layer 4 in order to miniaturize the flat cable 100 and make it easy to bend, there is a problem that the winding of the metal strands 411 comes loose during terminal processing or manufacturing. However, in the present embodiment, by providing the batch plating portion 42, it becomes possible to suppress the loosening of the horizontally wound shield portion 41. As a result, the sheath becomes unnecessary, the outer diameter of the coaxial line 1 is reduced, and effects such as miniaturization and thinning can be obtained. In addition, the coaxial line 1 can be held in a state where the metal strands 411 do not come loose regardless of the thickness and material of the film member 11, and further miniaturization and thinning become possible. Furthermore, in the flat cable 100, operations such as pre-soldering during terminal processing can be omitted, and the workability during terminal processing is improved.

[0050] Also, in the flat cable 100, the batch plating portion 42 is arranged as the outermost portion of the coaxial line 1, and since the batch plating portion 42 and the covering portion 10 are in contact with each other, at a predetermined position that is not the terminal in the longitudinal direction of the flat cable 100, the batch plating portion 42 can be exposed only by removing the covering portion 10. It is also possible to adopt a connection structure in which the horizontally wound shield portion 41 is grounded or the like using the exposed batch plating portion 41 without performing operations such as pre-soldering.

[0051] In addition, since the shield layer 4 is connected in a substantially full circumference via the batch plating portion 42, it becomes possible to close the gaps between the metal strands 411 of the horizontally wound shield portion 41 with the batch plating portion 42, improve the noise characteristics, and suppress the occurrence of suck-out. That is, according to the present embodiment, it is possible to realize a flat cable 100 suitable for high-speed transmission in which a decrease in the shielding effect hardly occurs and rapid attenuation hardly occurs in a predetermined frequency band (for example, a frequency band up to 26 GHz).

[0052] Furthermore, by having the batch plating portion 42, it becomes easier to maintain the shape of the flat cable 100 in the bent shape with respect to its width direction and thickness direction. As a result, for example, operations such as attaching the flat cable 100 in a bent state along a pre-determined wiring path in advance become possible, and the wiring work becomes easier.

[0053] (Summary of Embodiments) Next, regarding the technical idea grasped from the embodiments described above, it will be described by referring to the reference numerals and the like in the embodiments. However, each reference numeral and the like in the following description are not limited to the members and the like that specifically show the components in the claims in the embodiments.

[0054] [1] A flat cable (100) comprising: a plurality of coaxial lines (1) provided with a shield layer (4) having a coating portion (42) made of a melt plating around the circumferences of the horizontal winding shield portions (41) as the outermost layer; and a coating portion (10) that collectively coats the circumferences of the plurality of coaxial lines (1) arranged in parallel.

[0055] [2] The flat cable (100) according to [1], wherein the outer diameter of the coaxial line (1) is 0.1 μm or more and 0.3 μm or less.

[0056] [3] The flat cable (100) according to [1] or [2], wherein the collective plating portion (42) is made of tin.

[0057] [4] The coating portion (10) is composed of a pair of film members (11) provided so as to sandwich the plurality of coaxial lines (1) in the thickness direction perpendicular to the longitudinal direction and the arrangement direction of the plurality of coaxial lines (1). The pair of film members (11) are made of an insulating resin and are adhesively fixed to the plurality of coaxial lines (1). The flat cable (100) according to [1] or [2].

[0058] [5] The flat cable (100) according to [4], wherein the thickness of the film member (11) is 4 μm or more and 15 μm or less.

[0059] Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential means for solving the problems of the invention. Further, the present invention can be appropriately modified and implemented without departing from its gist.

Explanation of Reference Numerals

[0060] 1... Coaxial line 2... Conductor 3... Insulator 4... Shield layer 41... Horizontally wound shield portion 411... Metal strand 42... Integral plating portion 10... Coating portion 11... Film member 100... Flat cable

Claims

1. A plurality of coaxial lines provided with a shield layer coated with a batch plating portion made of molten plating around the circumferential winding shield portion as the outermost layer, and a covering portion that collectively covers the circumferences of the plurality of coaxial lines arranged in parallel. The covering portion is composed of a pair of film members provided so as to sandwich the plurality of coaxial lines in a thickness direction perpendicular to the longitudinal direction and the arrangement direction of the plurality of coaxial lines. The pair of film members is made of an insulating resin and is adhesively fixed to the plurality of coaxial lines. A flat cable.

2. The outer diameters of the plurality of coaxial lines are 0.1 mm or more and 0.3 mm or less. The flat cable according to claim 1.

3. The batch plating portion is made of tin. The flat cable according to claim 1 or 2.

4. The thickness of the film member is 4 μm or more and 15 μm or less. The flat cable according to claim 1 or 2.

5. The circumferential winding shield portion is formed by winding a plurality of metal strands in a spiral shape. The shield layer has a separation portion where the plurality of metal strands adjacent to each other in the circumferential direction are separated at least in a part of the circumferential winding shield portion. The batch plating portion enters the separation portion, and the inner surface of the entered portion is concave and recessed toward the covering portion side. The flat cable according to claim 1.

6. The circumferential winding shield portion is formed by winding a plurality of metal strands in a spiral shape. In the batch plating portion located radially outward of the plurality of metal strands, the thickness of the batch plating portion is less than 0.5 times the diameter of the plurality of metal strands. The flat cable according to claim 1.

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