Coaxial cable and cable assembly

Abstract

The present invention provides a coaxial cable and a cable assembly which are difficult to produce a reduction in shielding effect and difficult to produce a sharp attenuation in a predetermined frequency band. A shield layer (4) has a transverse-wound shield portion (41) in which a plurality of metal wires (411) are spirally wound so as to cover the periphery of an insulator (3), and a one-plating portion (42) formed by hot-dip plating which covers the periphery of the transverse-wound shield portion (41), the shield layer (4) having a separation portion (46) in which circumferentially adjacent metal wires (411) are separated from each other, in the separation portion (46) existing at a local site in the cable length direction, having a non-joining portion (44) in which the adjacent metal wires (411) are not joined to each other by the one-plating portion (42), the length of the non-joining portion (44) in the cable length direction being shorter than the winding pitch of the transverse-wound shield portion (41).

Description

Technical Field

[0001] This invention relates to coaxial cables and cable assemblies. Background Technology

[0002] Coaxial cables are used for internal wiring in electronic devices such as cameras, smartphones, and tablets used in automated operations, or for high-frequency signal transmission in machine tools such as industrial robots.

[0003] As for existing coaxial cables, there are known coaxial cables in which a shielding layer is formed by spirally winding a copper strip or other strip component with copper foil on a resin layer around an insulator (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-285747 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in the aforementioned existing coaxial cables, there is a problem of a phenomenon known as "suck out," which causes a sharp attenuation in a predetermined frequency band (e.g., a band of several GHz such as 1.25 GHz).

[0009] In contrast, for example, by plating the outer surface of the insulator to form a shielding layer, the generation of bandwidth gaps can be suppressed. However, when the coaxial cable is repeatedly bent, cracks may occur in the plating shielding layer, and peeling may occur from the outer surface of the insulator. If cracks occur in the plating shielding layer and peeling occurs from the outer surface of the insulator, the shielding effect is reduced. That is, the effectiveness of using the shielding layer to block noise generated in the coaxial cable is reduced.

[0010] Therefore, the object of the present invention is to provide a coaxial cable and cable assembly that are difficult to shield and are difficult to produce sharp attenuation in a predetermined frequency band.

[0011] Solution for solving the problem

[0012] To address the aforementioned problems, the present invention provides a coaxial cable comprising: a conductor; an insulator covering the periphery of the conductor; a shielding layer covering the periphery of the insulator; and a sheath covering the periphery of the shielding layer. The shielding layer has: a transverse shielding portion having a plurality of metal wires spirally wound around it in a manner covering the periphery of the insulator; and a plating portion covering the periphery of the transverse shielding portion, formed by hot-dip plating. The shielding layer has a separation portion in which adjacent metal wires in the circumferential direction are separated from each other. In the separation portion, which exists in a local portion in the cable length direction, there is a non-connection portion in which adjacent metal wires in the circumferential direction are not connected to each other by the plating portion. The length of the non-connection portion along the cable length direction is shorter than the winding pitch of the transverse shielding portion.

[0013] Furthermore, in order to solve the above-mentioned problems, the present invention provides a cable assembly comprising: the aforementioned coaxial cable; and a terminal component integrally disposed at at least one end of the aforementioned coaxial cable.

[0014] The effects of the invention are as follows.

[0015] According to the present invention, it is possible to provide coaxial cables and cable assemblies that are difficult to shield and are difficult to produce sharp attenuation in a predetermined frequency band. Attached Figure Description

[0016] Figure 1 The diagram shows a coaxial cable according to one embodiment of the present invention, (a) is a cross-sectional view showing a section perpendicular to the length direction, and (b) is an enlarged view of its main parts.

[0017] Figure 2 (a) is a photograph showing the shielding layer after it has been peeled off from the insulator surface, viewed from the insulator side, and (b) is a photograph showing the appearance of the shielding layer after it has been formed.

[0018] Figure 3 It is a line graph showing the evaluation results of frequency characteristics.

[0019] Figure 4 This is a cross-sectional view showing the end portion of a cable assembly according to one embodiment of the present invention.

[0020] Symbol Explanation

[0021] 1—Coaxial cable, 2—Conductor, 3—Insulator, 4—Shielding layer, 41—Cross-wound shielding part, 411—Metallic wire, 411a—Metallic wire, 411b—Platinum coating, 411c—Intermetallic compound, 42—Platinum coating part, 4a—Outer peripheral part, 4b—Inner peripheral part, 43—Connecting part, 44—Non-connecting part, 44a—Through hole, 45—Contact part, 46—Separating part, 5—Sheath, 10—Cable assembly, 11—Terminal component. Detailed Implementation

[0022] [Implementation Method]

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0024] Figure 1 The diagram shows the coaxial cable of this embodiment, (a) is a cross-sectional view showing a section perpendicular to the length direction, and (b) is an enlarged view of its main parts.

[0025] like Figure 1 As shown in (a) and (b), the coaxial cable 1 includes a conductor 2, an insulator 3 disposed around the conductor 2, a shielding layer 4 disposed around the insulator 3, and a sheath 5 disposed around the shielding layer 4.

[0026] Conductor 2 is composed of a stranded conductor formed by twisting multiple metal wires 21 together. In this embodiment, conductor 2 is formed by twisting seven soft copper wires 21 with an outer diameter of 0.023 mm together. However, it is not limited to this; a compressed stranded conductor can also be used as conductor 2. That is, after twisting the metal wires 21, a compressed stranded conductor is formed by compressing the metal wires to make the cross-sectional shape perpendicular to the cable length direction circular. By using a compressed stranded conductor as conductor 2, conductivity can be improved, good transmission characteristics can be obtained, and flexibility can be maintained. Furthermore, from the viewpoint of improving conductivity and mechanical strength, the metal wires 21 can also be copper alloy wires containing tin (Sn), silver (Ag), indium (In), titanium (Ti), magnesium (Mg), iron (Fe), etc.

[0027] The insulator 3 is made of, for example, PFA, FEP (tetrafluoroethylene-hexafluoropropylene copolymer) fluororesin, polyethylene, polypropylene, etc. The insulator 3 can be a foaming resin or a resin cross-linked to improve heat resistance. Furthermore, the insulator 3 can be a multilayer structure. For example, it can be a three-layer structure: a first non-foamed layer made of non-foamed polyethylene is provided around the conductor 2; a foamed layer made of foamed polyethylene is provided around the first non-foamed layer; and a second non-foamed layer made of non-foamed polyethylene is provided around the foamed layer. In this embodiment, the insulator 3 made of PFA is formed around the conductor 2 by tubing extrusion. Forming the insulator 3 by tubing extrusion makes it easier to peel the insulator 3 from the conductor 2 during end processing, improving end processability.

[0028] In the coaxial cable 1 of this embodiment, the shielding layer 4 has: a transverse shielding portion 41, which has a plurality of metal wires 411 spirally wound around the insulator 3; and a conductive plating portion 42, which is disposed to cover the periphery of the transverse shielding portion 41. The plating portion 42 is preferably configured to cover the entire periphery of the transverse shielding portion 41 in both the circumferential and axial directions, and to mechanically and electrically connect the plurality of metal wires 411.

[0029] The shielding layer 4 has a contact portion 45 that brings adjacent metal wires 411 in the circumferential direction into contact with each other, and a separation portion 46 that separates adjacent metal wires 411 in the circumferential direction. Furthermore, the shielding layer 4 has a connecting portion 43 in the separation portion 46 that connects adjacent metal wires 411 in the circumferential direction to each other by a plating portion 42, and a non-connecting portion 44 in the separation portion 46 that does not connect adjacent metal wires 411 in the circumferential direction to each other by a plating portion. The non-connecting portions 44 are irregularly distributed at arbitrary locations along the cable length direction. That is, when the shielding layer 4 is viewed in a cross-section perpendicular to the cable length direction, Figure 1 As shown in (a), only the cross-section of the connecting portion 43, which has the separation portion 46 connected by a plating portion, exists continuously along the cable length direction, but in local portions along the cable length direction, there are... Figure 1 (b) shows a cross-section of a non-connected portion 44 with separation portions 46 not connected by a co-plated portion. The non-connected portion 44, present in a localized area along the cable length, exists in one or both of the plurality of separation portions 46 present in the circumferential direction of the shielding layer 4. The circumferential width of the non-connected portion 44 (in the through-hole 44a described below, the size along the direction in which the plurality of metal wires 411 are arranged side-by-side) is preferably smaller than the outer diameter of the metal wires 411, for example, 0.005 mm or more and 0.050 mm or less. Furthermore, in the contact portion 45, a filling portion is provided around the outer periphery of the shielding layer 41, where adjacent metal wires 411 in the circumferential direction are filled with co-plated portions.

[0030] By having a connecting portion 43, compared to the case where all adjacent metal wires 411 in the circumferential direction are in contact with each other, the co-plated portion 42 is less likely to crack or peel off when bending or twisting is applied. That is, the connecting portion 43, where the parts of the metal wires 441 that are separated from each other are connected by the co-plated portion 42, is constructed solely using the co-plated portion 42, which is more flexible than the metal wires 411, in a hot-dip plating process. When bending or twisting is applied, the co-plated portion 42 of the connecting portion 43 functions in an extended manner, increasing the overall flexibility of the shielding layer 4. As a result, the co-plated portion 42 is less likely to crack or peel off when bending or twisting is applied. Furthermore, regarding the distance between adjacent metal wires 411 in the circumferential direction, if 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, the above-mentioned effects are easily obtained. Furthermore, the surface of the connecting portion 43, which faces the surface (outer peripheral surface) of the insulator 3, has a shape that bends inward toward the inner side of the connecting portion 43, thereby easily achieving the aforementioned effects. Moreover, by having such a bent shape, a predetermined gap can be provided between the surface of the insulator 3 and the surface of the connecting portion 43, thus enabling the coaxial cable 1 to achieve a reduction in shielding effect and to avoid drastic attenuation in a predetermined frequency band (e.g., up to 26 GHz).

[0031] Furthermore, if the radial thickness W of the co-plated portion 42 of the connecting portion 43 (the minimum straight-line distance from the inner surface to the outer surface of the co-plated portion 42 of the connecting portion 43) is, for example, 30% (0.3 × d) or more of the outer diameter (diameter) d of the metal wire 411, it is difficult for cracks to occur in the co-plated portion 42. In particular, when the thickness W of the co-plated 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, making it even more difficult for cracks to occur. Moreover, in the coaxial cable 1, the co-plated portion 42 has the aforementioned connecting portion 43, so that during cable assembly, with the multiple metal wires 411 constituting the transverse shielding portion 41 in close contact with the co-plated portion 42, it is easy to remove the shielding layer 4 while spirally winding along the winding direction of the multiple metal wires 411. The upper limit of the thickness W of the plating portion 42 in the connecting portion 43 can be, for example, 130% (1.3 × d) of the outer diameter d of the metal wire 411. Furthermore, the outer diameter d of the metal wire 411 is, for example, 0.02 mm to 0.10 mm. The thickness W of the connecting portion 43 and the outer diameter d of the metal wire 411 can be determined, for example, by observing the cross-section (a section perpendicular to the length direction of the coaxial cable 1) of the coaxial cable 1 using an optical microscope or an electron microscope.

[0032] For example, if the shielding layer 4 is formed solely by the transverse shielding portion 41, gaps will be generated between the metal wires 411, resulting in a decrease in noise characteristics. Furthermore, due to the effect of the gaps generated between the metal wires 411, a phenomenon known as a bandwidth gap will occur, causing a sharp attenuation in a predetermined frequency band (e.g., the 10GHz to 25GHz band). As described in this embodiment, a hot-dip galvanized plating portion 42 is provided to cover the entire periphery of the transverse shielding portion 41, thereby blocking most of the gaps between the metal wires 411 (the portion other than the non-connecting portion 44 described below), improving the shielding effect. This makes signal transmission loss less likely. Furthermore, since the gaps between the metal wires 411 are essentially eliminated, the generation of bandwidth gaps can be suppressed.

[0033] Furthermore, by providing the plating section 42 in a manner that covers the area around the shielding section 41, when the sheath 5 is removed at the end of the cable during end processing to expose the shielding layer 4, the metal wire 411 is difficult to untangle, thereby facilitating end processing. Moreover, by providing the plating section 42 in a manner that covers the area around the shielding section 41, the impedance can also be stably maintained at a constant value along the length of the cable.

[0034] like Figure 1 As shown in (b), the plated portion 42 is shaped in a wave pattern along the outline of each metal wire 411 constituting the transverse shielding portion 41. That is, the plated portion 42 is recessed at a circumferential position (i.e., the position of the connecting portion 43) corresponding to the circumferentially adjacent metal wires 411, and a gap 6 exists between the plated portion 42 and the sheath 5 in this recessed portion. Because the connecting portion 43 has a gap 6, when the coaxial cable 1 is bent, the outer surface of the plated portion 42 can extend in a manner following the bend, thus making it difficult for the plated portion 42 to crack. Furthermore, the gap 6 in the connecting portion 43 also improves the flexibility of the coaxial cable 1.

[0035] In this embodiment, since the metal wire 411 is fixed using the plating portion 42, in order to ensure the flexibility of the coaxial cable 1, the metal wire 411 needs to be made of a material with low yield strength that is easily plastically deformable. More specifically, it is preferable to use a metal wire 411 with a tensile strength of 200 MPa or more and 380 Pa or less, and an elongation of 7% or more and 20% or less.

[0036] In this embodiment, the metal wire 411 is a silver-plated soft copper wire with a silver plating layer 411b surrounding the metal wire 411a, which is made of soft copper wire. Furthermore, the metal wire 411a is not limited to soft copper wire; copper alloy wire, aluminum wire, aluminum alloy wire, or wire with a low softening temperature and containing trace amounts of metallic elements (such as titanium, magnesium, etc.) added to pure copper can be used. Also, the metal constituting the plating layer 411b is not limited to silver; for example, tin or gold can be used, and the plating layer 411b can be omitted. Here, the transversely wound shielding portion 41 is formed by using a metal wire 411 composed of 22 silver-plated soft copper wires with an outer diameter of 0.025 mm.

[0037] Furthermore, in this embodiment, a portion made of tin is used as the integrally plated portion 42 formed by hot-dip plating. However, it is not limited to this, and portions made of silver, gold, copper, zinc, etc., can be used as the integrally plated portion 42. However, from the viewpoint of ease of manufacture, it can be said that using an integrally plated portion 42 made of tin is more preferable.

[0038] After multiple metal wires 411 are twisted together around the insulator 3 to form a transverse shielding portion 41, it is passed through a tank containing molten tin to form a co-plated portion 42. That is, the co-plated portion 42 is a molten plating layer formed by hot-dip plating. In order to easily attach tin to the entire periphery of the transverse shielding portion 41, it is preferable to apply a flux around the transverse shielding portion 41 and then pass it through a tank containing molten tin at a temperature of 250°C or higher and lower than 300°C. The linear speed of the wire with the transverse shielding portion 41 passing through the tank is, for example, 40 m / min or higher and 80 m / min or lower, more preferably 50 m / min or higher and 70 m / min or lower. As a flux, for example, a rosin-based flux can be used. Furthermore, after the wire with the transverse shielding portion 41 is passed through the tank containing molten tin, it is passed through a mold to remove unwanted tin. At this time, by adjusting the aperture of the mold, the amount of tin adhering, i.e. the thickness of the co-plated portion 42, can be adjusted. By forming the co-plated portion 42 formed by hot-dip plating using the above method, the following tiny non-connected portion 44 can be formed in the shielding layer 4.

[0039] Figure 2 (a) is a photograph of the shielding layer 4 after it has been peeled off from the surface of the insulator 3, viewed from the insulator side; (b) is a photograph showing the appearance of the shielding layer 4 after its formation (before the sheath 5 is formed). Figure 1 and Figure 2As shown, in the coaxial cable 1 of this embodiment, a plurality of tiny non-connected portions 44 are formed in the shielding layer 4. Furthermore, each non-connected portion 44 is constituted by a through hole 44a that radially penetrates the plated portion 42. The through hole 44a is formed in a slit-like manner between circumferentially adjacent metal wires 411, and is spirally formed around the insulator 3 with its slit-like long side following the length direction of the metal wire 411. Figure 2 The through holes 44a shown in (a) and (b) are distributed discontinuously (irregularly) relative to the length of the cable.

[0040] The through-hole 44a, which is a non-connecting part 44, is formed as follows: when the molten tin attached to the metal wire 411 cools and solidifies, a portion of the tin moves downward in the vertical direction or towards the metal wire 411 due to gravity and surface tension. Therefore, the formation position and size (length along the length of the metal wire 411, hereinafter referred to as the length of the through-hole 44a) are irregular. For example, if the through-holes 44a are formed periodically along the cable length direction, there is a concern that a phenomenon known as a frequency band gap, which causes sharp attenuation in a predetermined frequency band (e.g., a frequency band of several GHz such as 1.25 GHz), may occur. However, by irregularly forming the through-holes 44a, the generation of frequency band gaps can be suppressed. Furthermore, the number and length of the through-holes 44a can be adjusted by the amount of tin attached, and can also be adjusted by adjusting the aperture of the mold.

[0041] By having multiple non-connecting portions 44 in the connecting portion 43 of the shielding layer 4, the non-connecting portions 44 can alleviate the stress when the coaxial cable 1 is bent, and can suppress the possibility of cracks in the plating portion 42 or breakage of the metal wire 411. As a result, a coaxial cable 1 that reduces the shielding effect when bending the wiring and is less prone to sharp attenuation in a predetermined frequency band can be achieved. Furthermore, in the case where the shielding layer 4 has a through hole extending along the cable length direction, the through hole can have a significant impact on the shielding characteristics. In this embodiment, the through hole 44a, which is a non-connecting portion 44, extends obliquely relative to the cable length direction (along the length direction of the metal wire 411), thereby suppressing the impact on the shielding characteristics of the through hole 44a, and even if the through hole 44a is present, it is difficult for the shielding characteristics to deteriorate.

[0042] Each of the multiple through holes 44a (non-connecting portions 44) has a length along the cable length direction that is shorter than the winding pitch of the transverse shielding portion 41. This is because if the length of each through hole 44a (non-connecting portion 44) along the cable length direction is greater than or equal to the winding pitch of the transverse shielding portion 41, the through holes 44a (non-connecting portions 44) will surround the insulator 3 once, causing an increase in the resistance of the shielding layer 4, which could adversely affect the transmission characteristics or degrade the shielding effect. Furthermore, the winding pitch of the transverse shielding portion 41 refers to the interval along the cable length direction between any metal wires 411 that are in the same position in the circumferential direction. The winding pitch of the transverse shielding portion 41 is preferably more than 6 times and less than 20 times the core diameter of the layer formed by the transverse shielding portion 41 (i.e., twice the value of the shortest distance between the center of the cable and the center of the metal wire 411). If the winding pitch is 6 times or more the core diameter Pd, the deterioration of the shielding effect of the transversely wound shielding portion 41 can be suppressed, and the reduction in production efficiency can also be suppressed. If the winding pitch is 20 times or less the core diameter Pd, the situation where the transversely wound shielding portion 41 becomes loose and the separation distance between adjacent metal wires 411 increases can be suppressed, thus the above-mentioned co-plated portion 42 can be stably formed, and the reduction in shielding effect can also be suppressed.

[0043] More specifically, it is preferable that the length of each of the plurality of through holes 44a (non-connecting portions 44) (the length along the length direction of the metal wire 411) is 1.0 mm or less. This helps to suppress the degradation of transmission characteristics and shielding effect caused by the presence of through holes 44a (non-connecting portions 44). Furthermore, if the through holes 44a (non-connecting portions 44) are too short, there is a concern that the stress relief during bending of the coaxial cable 1 may not be adequate. Therefore, the length of the through holes 44a (non-connecting portions 44) is preferably 0.1 mm or more, and more preferably 0.1 mm or more and 1.0 mm or less.

[0044] Regarding the width of the through-hole 44a (non-connecting portion 44) (width along the circumference of the cable), if it is too wide, there are concerns about deterioration of transmission characteristics and shielding effect. Since the width of the through-hole 44a (non-connecting portion 44) is approximately equal to the spacing between the metal wires 411, it can be adjusted by the spacing between the metal wires 411. In this embodiment, the value obtained by summing the spacing between adjacent metal wires 411 in the circumferential direction over the entire circumference is smaller than the outer diameter of a single metal wire 411. Therefore, the width of each of the plurality of through-holes 44a (non-connecting portions 44) is at least smaller than the outer diameter of the metal wire 411. More specifically, it is preferable that the maximum value obtained by summing the spacing between adjacent metal wires 411 in the circumferential direction over the entire circumference, i.e., the width of the through-hole 44a, is 5% or less of the diameter of the circle passing through the center of the metal wire 411 (the midpoint between the inner and outer diameters of the shielding portion 41). Therefore, it is possible to suppress the deterioration of transmission characteristics and shielding effect caused by the excessive width of the through hole 44a (non-connecting part 44).

[0045] Furthermore, regarding the number of through holes 44a (non-connecting portions 44), if there are too few, there is a concern that the stress relief effect when the coaxial cable 1 is bent cannot be sufficiently obtained; if there are too many, there is a concern that the transmission characteristics and shielding effect will deteriorate. The inventors manufactured a prototype coaxial cable 1 and conducted observations, confirming that: 10 to 20 through holes 44a (non-connecting portions 44) with a length of 0.1 mm to 1.0 mm are formed per 1 m of coaxial cable 1. Details are as follows. However, in the prototype coaxial cable 1, the occurrence of frequency band gaps was suppressed, and good transmission characteristics were obtained. Therefore, it can be said that at least 10 to 20 through holes 44a (non-connecting portions 44) can suppress the deterioration of transmission characteristics.

[0046] During the formation of the plating portion 42, the silver in the plating layer 411b, which constitutes the portion in contact with molten tin (i.e., hot-dip plating), diffuses into the tin in the plating bath, forming an intermetallic compound 411c containing copper and tin between the metal wire 411 and the plating portion 42 (i.e., between the metal wire 411a and the plating portion 42 and in contact with the surface of the metal wire 411a). The inventors conducted EDX analysis (energy-dispersive X-ray spectroscopy analysis) using SEM (scanning electron microscope), and the results confirmed that the intermetallic compound 411c composed of copper and tin exists in layers on the surface of the metal wire 411 (between the metal wire 411 and the plating portion 42). That is, the intermetallic compound 411c is formed on the surface of the metal wire 411 by a metallic diffusion reaction between the metal element (tin, etc.) constituting the plating portion 42 formed by hot-dip plating and the metal element (copper, etc.) constituting the main component of the metal wire 411. The thickness of the intermetallic compound 411c layer is, for example, about 0.2 μm to 1.5 μm. Furthermore, it is believed that the intermetallic compound 411c contains silver constituting the plating layer 411b, but the silver content in the intermetallic compound 411c is extremely small, to a degree that is difficult to detect in EDX analysis.

[0047] The shielding layer 4 forms an intermetallic compound 411c between the metal wire 411 and the co-plated portion 42, making it difficult for the co-plated portion 42 to peel off from the surface of the metal wire 411 when the coaxial cable 1 is repeatedly bent or twisted, and making it difficult for gaps to form between the metal wire 411 and the co-plated portion 42. Therefore, in the coaxial cable 1, even when bending or twisting is applied, the co-plated portion 42 can maintain the state where the shielding portion 41 is fixed from the outside of the shielding portion 41, and the distance between the shielding layer 4 and the conductor 2 is difficult to change. Therefore, in the coaxial cable 1, it is difficult for the shielding effect to decrease due to bending or twisting, and it is also difficult for a sharp attenuation to occur in the predetermined frequency band. The thickness of the intermetallic compound 411c layer can be determined, for example, by observing the cross-section (a section perpendicular to the length direction of the coaxial cable 1) using an optical microscope or an electron microscope.

[0048] In the portion of the metal wire 411 that does not contact the plating portion 42 (the portion of the metal wire 411 that does not contact the molten tin during plating), a silver plating layer 411b remains. That is, in the portion of the metal wire 411 on the inner side (insulator 3 side) in the radial direction of the cable, a silver plating layer 411b remains. In other words, in the shielding layer 4 of the coaxial cable 1 of this embodiment, it is preferable that the conductivity of the inner peripheral portion 4b of the plurality of metal wires 411 not covered by the plating portion 42 is higher than the conductivity of the outer peripheral portion 4a of the plurality of metal wires 411 covered by the plating portion 42. During the transmission of high-frequency signals, the current is concentrated on the insulator 3 side in the shielding layer 4. Therefore, the presence of a plating layer 411b with high conductivity, such as silver, in the inner peripheral portion 4b of the shielding layer 4 can suppress the decrease in conductivity of the shielding layer 4 and maintain good attenuation characteristics. The tin plating constituting the plating layer 42 has a conductivity of 15% IACS, and the silver plating constituting the plating layer 411b has a conductivity of 108% IACS.

[0049] Furthermore, the outer peripheral portion 4a mentioned here refers to the portion where the metal wire 411 comes into contact with the molten plating (such as tin) during hot-dip plating (i.e., the portion where the intermetallic compound 411c is formed). And the inner peripheral portion 4b refers to the portion where the plating layer 411b, composed of silver plating or the like, remains.

[0050] Furthermore, at the periphery of the through-hole 44a (non-connecting portion 44), there is a shrinkage portion after contact with the molten plating (tin, etc.). In such a portion, during the stage of contact with the molten plating (tin, etc.), the silver constituting the plating layer 411b diffuses, thus forming an intermetallic compound 411c on the surface of the metal wire 411. That is, at the periphery of the through-hole 44a (non-connecting portion 44), there is an exposed state of the intermetallic compound 411 that is not covered by the plating portion 4.

[0051] The sheath 5 is made of, for example, fluoropolymers such as PFA and FEP, polyvinyl chloride, or cross-linked polyolefins. In this embodiment, the sheath 5, made of fluoropolymer, is formed by extrusion of a pipe.

[0052] (Characteristic evaluation of coaxial cable 1)

[0053] The coaxial cable 1 of this embodiment was fabricated as an example, and its frequency characteristics were evaluated. The cable length was 1m. In the coaxial cable 1 of this embodiment, the conductor 2 was made by twisting seven metal wires 21, each with an outer diameter of 0.023mm, together; the insulator 3 was made by extruding PFA (perfluoroalkoxyalkane) tubing; the transverse shield 41 was made by spirally winding 22 metal wires 411, each with an outer diameter of 0.025mm (43AWG) and silver plating on the surface; the plating part 42 was hot-dip plated with molten tin; and the sheath 5 was made of fluororesin. In the evaluation of frequency characteristics, the transmission characteristic S21 was measured using a network analyzer. The measurement range was 10MHz to 30GHz, and the output power was -8dBm. Figure 3 The measurement results are shown.

[0054] like Figure 3 As shown, in the coaxial cable 1 of the embodiment, no sharp attenuation was observed up to 20 GHz (e.g., up to 26 GHz), confirming that the frequency band was suppressed. Figure 3 As a result, even with the formation of the through-hole 44a (non-connecting part 44), the attenuation characteristics are not significantly affected, and there is almost no degradation in transmission characteristics. Moreover, it can be confirmed that there are no bandwidth gaps at least below 25 GHz.

[0055] (Cable assembly)

[0056] Next, the cable assembly using coaxial cable 1 will be described. Figure 4 This is a cross-sectional view showing the end portion of the cable assembly according to this embodiment.

[0057] like Figure 4 As shown, the cable assembly 10 includes a coaxial cable 1 according to this embodiment and a terminal component 11 integrally disposed at at least one end of the coaxial cable 1.

[0058] Terminal component 11 is, for example, a connector, a sensor, a substrate mounted in a sensor, or a substrate in an electronic device. Figure 4 The diagram shows a terminal component 11 that is a substrate 11a. A signal electrode 12 connected to a conductor 2 and a ground electrode 13 connected to a shielding layer 4 are formed on the substrate 11a. The substrate 11a is made of a printed circuit board, on which a conductor pattern including the signal electrode 12 and the ground electrode 13 is printed on a resin substrate 16.

[0059] At the end of the coaxial cable 1, the sheath 5, a portion of which is a predetermined length from the end, is removed to expose the shielding layer 4. Then, the exposed shielding layer 4 and the end of the insulator 3 are removed to expose the conductor 2. The exposed conductor 2 is fixed to the signal electrode 12 by a connecting material 14 such as solder, and the conductor 2 is electrically connected to the signal electrode 12. Furthermore, the exposed shielding layer 4 is fixed to the ground electrode 13 by a connecting material 15 such as solder, and the shielding layer 4 is electrically connected to the ground electrode 13. Alternatively, the connection between the conductor 2 and the shielding layer 4 may not use connecting materials 14 and 15 such as solder. For example, the conductor 2 and the shielding layer 4 may be connected by fixing them to a fixing metal part using riveting or the like. Furthermore, when the terminal component 11 is a connector or a sensor, the conductor 2 and the shielding layer 4 may be configured to be directly connected to the electrode or component.

[0060] (The role and effects of the implementation method)

[0061] As described above, in the coaxial cable 1 of this embodiment, the shielding layer 4 has a transverse shielding portion 41 in which a plurality of metal wires 411 are spirally wound around the insulator 3, and a plating portion 42 formed by hot-dip plating covering the periphery of the transverse shielding portion 41. In the separation portion 46 where adjacent metal wires 411 in the circumferential direction are separated from each other, the shielding layer 4 has a connecting portion 43 in which adjacent metal wires 411 in the circumferential direction are connected to each other by the plating portion 42, and a non-connecting portion 44 in the separation portion 46 where adjacent metal wires 411 in the circumferential direction are not connected to each other by the plating portion 42. A plurality of non-connecting portions 44 are formed in the shielding layer 4, and the length of each of the plurality of non-connecting portions 44 along the cable length direction is shorter than the winding pitch of the transverse shielding portion.

[0062] By configuring the shielding layer 4 in this way, the shielding layer 4 is connected approximately around the circumference via the plating portions 42. The plating portions 42 can seal the gaps between the metal wires 411 that wrap around the shielding layer 41, improving noise characteristics and suppressing the occurrence of frequency band gaps. That is, according to this embodiment, a coaxial cable 1 that is difficult to shield effectively and is unlikely to experience sharp attenuation in a predetermined frequency band (e.g., up to 26 GHz) can be achieved. Furthermore, since the shielding layer 4 has multiple non-connecting portions 44, the stress when bending the coaxial cable 1 can be mitigated, and cracks in the plating portions 42 can be suppressed. Even in the case of bent wiring, it is difficult for defects to occur in the shielding layer 4. Moreover, since the shielding layer 4 has multiple non-connecting portions 44, the coaxial cable 1 is easy to bend, resulting in a coaxial cable 1 that is easy to bend. Furthermore, by making the length of the non-connecting portion 44 along the cable length direction shorter than the winding spacing of the transverse shielding portion 41, it is possible to suppress the adverse effects on transmission characteristics and shielding characteristics caused by the formation of the non-connecting portion 44.

[0063] (Summary of Implementation Methods)

[0064] Next, the technical ideas grasped from the embodiments described above will be described by reference to symbols and the like. It should be noted that the symbols and the like used in the following description do not limit the constituent elements in the claims to the components specifically shown in the embodiments.

[0065] [1] A coaxial cable 1 includes: a conductor 2; an insulator 3 covering the periphery of the conductor 2; a shielding layer 4 covering the periphery of the insulator 3; and a sheath 5 covering the periphery of the shielding layer 4. The shielding layer 4 has: a transverse shielding portion 41, which has a plurality of metal wires 411 spirally wound around the periphery of the insulator 3; and a plating portion 42 covering the periphery of the transverse shielding portion 41, which is formed by hot-dip plating. The shielding layer 4 has a separation portion 46 in which adjacent metal wires 411 in the circumferential direction are separated from each other. In the separation portion 46, which exists in a local part in the length direction of the cable, there is a non-connection portion 44 in which adjacent metal wires 411 in the circumferential direction are not connected to each other by the plating portion 42. The length of the non-connection portion 44 along the length direction of the cable is shorter than the winding pitch of the transverse shielding portion 41.

[0066] [2] According to the coaxial cable 1 described in [1], the non-connecting portion 44 is composed of a through hole 44a that radially penetrates the plated portion 42.

[0067] [3] According to the coaxial cable 1 described in [1] or [2], the length of the non-connecting portion 44 along the length direction of the metal wire 411 is 0.1 mm or more and 1.0 mm or less.

[0068] [4] According to any one of [1] to [3], the non-connecting portions 44 are discontinuously distributed along the length of the cable, and the number of the non-connecting portions 44 per 1m of cable is more than 10 and less than 20.

[0069] [5] In the coaxial cable 1 described in any one of [1] to [4], the width of the non-connecting portion 44 along the circumference of the cable is smaller than the outer diameter of the metal wire 411.

[0070] [6] According to any one of [1] to [5], the coaxial cable 1 has an outer peripheral portion 4a of the plurality of metal wires 411 covered by the co-plated portion 42 and an inner peripheral portion 4b of the plurality of metal wires 411 not covered by the co-plated portion 42, wherein the outer peripheral portion 4a has an intermetallic compound 411c between the plurality of metal wires 411 and the co-plated portion 42.

[0071] [7] According to the coaxial cable 1 described in [6], the above-mentioned plated portion 42 is made of tin, the above-mentioned metal wire 411 is made of silver-plated soft copper wire, and the above-mentioned intermetallic compound 411c containing copper and tin is formed between the above-mentioned metal wire 411 and the above-mentioned plated portion 42.

[0072] [8] A cable assembly 10 includes: a coaxial cable 1 as described in any one of [1] to [7]; and a terminal component 11 integrally disposed at at least one end of the coaxial cable 1.

[0073] The embodiments of the present invention have been described above, but the embodiments described above do not limit the invention as claimed. Furthermore, it should be noted that the combinations of features described in the embodiments are not necessarily all necessary for solving the problems of the invention. Moreover, the present invention can be implemented with appropriate modifications without departing from its spirit.

Claims

1. A coaxial cable, characterized in that, have: conductor; An insulator that covers the area surrounding the aforementioned conductor; A shielding layer that covers the area surrounding the aforementioned insulator; and A protective sleeve that covers the area surrounding the aforementioned shielding layer. The aforementioned shielding layer comprises: a transverse shielding portion, which has a plurality of metal wires spirally wound around it in a manner that covers the periphery of the aforementioned insulator; and a plating portion, which covers the periphery of the transverse shielding portion and is formed by hot-dip plating. The aforementioned shielding layer has a separation portion in which adjacent metal wires are separated from each other in the circumferential direction. In the aforementioned separation portion, which exists in a local portion in the cable length direction, there is a non-connecting portion in which adjacent metal wires in the circumferential direction are not connected to each other by the aforementioned plated portion. The length of the non-connecting portion along the cable length direction is shorter than the winding pitch of the transverse shielding portion, and the non-connecting portion is formed by a through hole that penetrates the plated portion in the radial direction.

2. The coaxial cable according to claim 1, characterized in that, The length of the non-connecting portion along the length direction of the metal wire is 0.1 mm or more and 1.0 mm or less.

3. The coaxial cable according to claim 1 or 2, characterized in that, The aforementioned non-connected portions are discontinuously distributed along the length of the cable. The number of non-connecting parts mentioned above per 1m of cable is more than 10 and less than 20.

4. The coaxial cable according to claim 1 or 2, characterized in that, The width of the non-connecting portion along the circumference of the cable is smaller than the outer diameter of the metal wire.

5. The coaxial cable according to claim 1 or 2, characterized in that, The aforementioned shielding layer has an outer peripheral portion of the plurality of metal wires covered by the aforementioned plated portion, and an inner peripheral portion of the plurality of metal wires not covered by the aforementioned plated portion. The aforementioned outer periphery contains an intermetallic compound between the aforementioned plurality of metal wires and the aforementioned co-plated portion.

6. The coaxial cable according to claim 5, characterized in that, The aforementioned plated portion is made of tin. The aforementioned metal wire is composed of silver-plated soft copper wire. An intermetallic compound containing copper and tin is formed between the aforementioned metal wire and the aforementioned plated portion.

7. A cable assembly, characterized in that, have: The coaxial cable as described in any one of claims 1 to 6; and A terminal component integrally disposed at at least one end of the aforementioned coaxial cable.

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