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 are difficult to produce a sharp attenuation in a predetermined frequency band. A shield layer (4) of a coaxial cable (1) has a transversely-wound shield portion (41) which is formed by spirally winding a plurality of metal wires (411) having a plating layer (411b) on the outermost layer around an insulator (3), and a collectively-plated portion (42) which covers around the transversely-wound shield portion (41) and is formed by hot-dip plating, and a thickness of the collectively-plated portion (42) is 0.015 mm 2 or more and 0.300 mm 2 When element analysis is performed in any of the following analysis regions (51), an area of a region in which chlorine exists on the analysis region (51), that is, a chlorine-existing region (52) is 5% or less of an area of the analysis region (51).

Description

TECHNICAL FIELD

[0001] The present application relates to a coaxial cable and a cable assembly. BACKGROUND

[0002] As internal wiring of electronic devices such as a camera, a smart phone, a tablet terminal, and the like used in automatic operation and the like, or a cable for high-frequency signal transmission used as wiring in machine tools such as an industrial robot and the like, a coaxial cable is used.

[0003] As a conventional coaxial cable, a coaxial cable in which a tape member such as a copper tape provided with a copper foil on a resin layer is spirally wound around an insulator to constitute a shield layer is known (for example, refer to Patent Document 1).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-285747 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the above-described conventional coaxial cable, there is a problem that a phenomenon called a frequency band gap in which sharp attenuation occurs in a predetermined frequency band (for example, a frequency band of several GHz such as 1.25 GHz) occurs.

[0009] In contrast to this, for example, by forming the shield layer by plating the outer surface of the insulator, occurrence of the frequency band gap can be suppressed. However, when the coaxial cable is repeatedly bent, there are cases in which a crack occurs in the shield layer formed by plating and peeling from the outer surface of the insulator occurs. If a crack occurs in the shield layer formed by plating and peeling from the outer surface of the insulator occurs, the shielding effect decreases. That is, the effect of shielding noise generated in the coaxial cable by the shield layer decreases.

[0010] Therefore, an object of the present application is to provide a coaxial cable and a cable assembly in which a decrease in shielding effect is less likely to occur and sharp attenuation in a predetermined frequency band is less likely to occur.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] To address the aforementioned problems, this invention provides a coaxial cable comprising: a conductor; an insulator covering the conductor; a shielding layer covering the insulator; and a sheath covering the shielding layer. The shielding layer includes: a transverse shielding portion formed by spirally winding a plurality of plated metal wires around the insulator; and a plating portion covering the transverse shielding portion, formed by hot-dip plating, extending 0.015 mm in the insulator-side surface of the shielding layer peeled from the insulator. 2 Above and 0.300mm 2 When elemental analysis is performed in any of the following analytical regions, the area of ​​the region where chlorine exists, i.e., the area of ​​the chlorine-containing region, is less than 5% of the area of ​​the analytical region.

[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 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 formed by spirally winding a plurality of metal wires having a plating layer on the outermost layer around 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 where adjacent metal wires in the circumferential direction are separated from each other, and a connecting portion where adjacent metal wires in the circumferential direction are connected to each other by the plating portion. Furthermore, the shielding layer has an inner circumferential portion where the plating layer is exposed and the plurality of metal wires are not covered by the plating portion, and the connecting portion is provided between adjacent inner circumferential portions.

[0015] The effects of the invention are as follows.

[0016] 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

[0017] 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.

[0018] Figure 2 This diagram illustrates the formation of the plated portion.

[0019] Figure 3These are photographs taken after the shielding layer was removed for observation, along with magnified photographs.

[0020] Figure 4 (a) is a photograph showing the results of analysis on the areas containing silver in the stripped shielding layer, and (b) is a photograph showing the results of analysis on the areas containing tin in the stripped shielding layer.

[0021] Figure 5 This is a flowchart illustrating the steps involved in analyzing an area where chlorine is present.

[0022] Figure 6 (a) and (b) are photographs showing an example of SEM images.

[0023] Figure 7 (a) and (b) are photographs showing an example of a chlorine mapping image.

[0024] Figure 8 It is a line graph showing the evaluation results of frequency characteristics.

[0025] Figure 9 This is a cross-sectional view showing the end portion of a cable assembly according to one embodiment of the present invention.

[0026] Symbol Explanation

[0027] 1—Coaxial cable, 2—Conductor, 3—Insulator, 4—Shielding layer, 4a—Outer peripheral portion, 4b—Inner peripheral portion, 41—Wrapped shielding portion, 411—Metallic wire, 411a—Metallic wire, 411b—Platinum coating, 411c—Intermetallic compound, 42—Co-plated portion, 43—Connecting portion, 45—Separating portion, 5—Sheath, 10—Cable assembly, 11—Terminal component, 51—Analytical region, 52—Chlorine presence region. Detailed Implementation

[0028] [Implementation Method]

[0029] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0030] (Overall structure of coaxial cable 1)

[0031] Figure 1 The diagram shows the coaxial cable 1 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.

[0032] 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.

[0033] The conductor 2 is composed of a stranded conductor in which a plurality of metal wires 21 are stranded. In the present embodiment, a conductor 2 in which seven metal wires 21 each composed of a soft copper wire having an outer diameter of 0.023 mm are stranded is used. This is not limiting, and as the conductor 2, a compressed stranded conductor in which the metal wires 21 are compressed after being stranded so as to have a circular cross-sectional shape perpendicular to the cable length direction can also be used. By using a compressed stranded conductor as the conductor 2, the electrical conductivity can be improved, good transmission characteristics can be obtained, and the ease of bending can also be maintained. In addition, from the viewpoint of improving the electrical 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), or the like.

[0034] The insulator 3 is composed of, for example, PFA, FEP (tetrafluoroethylene-hexafluoropropylene copolymer) fluororesin, polyethylene, polypropylene, or the like. The insulator 3 can be a foamed resin, or can be composed of a resin crosslinked to improve heat resistance. Furthermore, the insulator 3 can also be multilayered. For example, it can be a three-layer structure in which a first non-foamed layer composed of non-foamed polyethylene is provided around the conductor 2, a foamed layer composed of foamed polyethylene is provided around the first non-foamed layer, and a second non-foamed layer composed of non-foamed polyethylene is provided around the foamed layer. In the present embodiment, the insulator 3 composed of PFA is formed around the conductor 2 by pipe extrusion. By forming the insulator 3 by pipe extrusion, the insulator 3 is easily peeled from the conductor 2 at the time of end processing, and the end processing property is improved.

[0035] The sheath 5 is composed of, for example, fluororesin such as PFA, FEP, polyvinyl chloride, crosslinked polyolefin, or the like. In the present embodiment, the sheath 5 composed of fluororesin is formed by pipe extrusion.

[0036] (Shielding layer 4)

[0037] In the coaxial cable 1 of the present embodiment, the shielding layer 4 has a transposition shielding portion 41 in which a plurality of metal wires 411 are spirally wound around the insulator 3, and a conductive blanket plating portion 42 that is provided so as to cover the entire circumference of the transposition shielding portion 41.

[0038] In the present embodiment, since the metal wires 411 are fixed by the blanket plating portion 42, in order to ensure the ease of bending of the coaxial cable 1, as the metal wires 411, it is necessary to use wires composed of a material having a low yield strength that easily plastically deforms. More specifically, as the metal wires 411, it is preferable to use metal wires 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.

[0039] In the present embodiment, as the metal wire 411, a silver-plated soft copper wire having a plating layer 411b composed of silver around a metal wire 411a composed of a soft copper wire is used. Further, as the metal wire 411a, it is not limited to a soft copper wire, and a copper alloy wire, an aluminum wire, an aluminum alloy wire, or a low-softening-temperature wire in which a trace amount of a metal element such as titanium, magnesium, or the like is added to pure copper, or the like can be used. Also, the metal constituting the plating layer 411b is not limited to silver, and can be, for example, tin, gold. Among them, in order to make the electrical characteristics of the coaxial cable 1 good, the plating layer 411b is preferably high in electric conductivity, and it is preferable to use a plating layer composed of a material having an electric conductivity at least higher than that of the one-plating portion 42. That is, it can be said that it is more preferable to use a plating layer 411b composed of silver high in electric conductivity. Here, the transverse shielding portion 41 is formed by using 22 metal wires 411 composed of a silver-plated soft copper wire having an outer diameter of 0.025 mm.

[0040] Also, in the present embodiment, as the one-plating portion 42 formed by hot dipping, a one-plating portion composed of tin is used. However, it is not limited thereto, and as the one-plating portion 42, for example, a member composed of silver, gold, copper, zinc, or the like can be used. However, from the viewpoint of easiness of manufacture, it can be said that it is more preferable to use a one-plating portion 42 composed of tin.

[0041] Figure 2 is a view for explaining the formation of the one-plating portion 42. First, before the one-plating portion 42 is formed, a plurality of metal wires 411 are stranded around the insulator 3 to form the transverse shielding portion 41. The structure in which the transverse shielding portion 41 is formed around the insulator 3 is referred to as a cable base 101. At the time of formation of the one-plating portion 42, first, a reel 102a on which the cable base 101 is wound is set to a feeding device 102, and the cable base 101 is fed from the feeding device 102. The cable base 101 fed from the feeding device 102 is introduced to a flux tank 103, and a flux is applied around the cable base 101 (i.e., around the transverse shielding portion 41). The flux is used to make the molten tin easily adhere to the entire circumference of the transverse shielding portion 41, and is mainly composed of chlorine and zinc. As the flux, for example, a flux of a rosin type or the like can be used.

[0042] The cable base 101 that has passed through the flux tank 103 is introduced to a plating tank 104 in which tin that melts at a temperature of 250°C or higher and less than 300°C is stored, and passes through a die 105. The tin that remains after passing through the die 105 is cooled, thereby forming the simultaneous plating portion 42. That is, the simultaneous plating portion 42 is hot-dip plating formed by hot-dip plating. After that, the cable base 101 on which the simultaneous plating portion 42 is formed is wound by a winding machine 106. In addition, the linear velocity when the cable base 101 on which the transverse-wound shield portion 41 is formed passes through the plating tank 104 is, for example, 40 m / min or higher and 80 m / min or lower, and more preferably 50 m / min or higher and 70 m / min or lower.

[0043] In the formation of the simultaneous plating portion 42, the silver that constitutes the plating layer 411b of the portion that comes into contact with the molten tin (i.e., hot-dip plating) diffuses into the tin in the plating tank 104, and an intermetallic compound 411c containing copper and tin is formed between the metal wire 411 and the simultaneous plating portion 42 (i.e., between the metal wire 411a and the simultaneous plating portion 42 and the portion that comes into contact with the surface of the metal wire 411a). The inventors and others performed EDX analysis (analysis based on energy dispersive X-ray spectroscopy) using an SEM (scanning electron microscope), and as a result, it was confirmed that the intermetallic compound 411c composed of copper and tin existed in layers on the surface of the metal wire 411 (between the metal wire 411 and the simultaneous plating portion 42). That is, the intermetallic compound 411c is a compound layer that is formed on the surface of the metal wire 411 as a result of a diffusion reaction between the metal element (tin, etc.) that constitutes the simultaneous plating portion 42 composed of hot-dip plating and the metal element (copper, etc.) that constitutes 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. In addition, it is considered that silver that constitutes the plating layer 411b is contained in the intermetallic compound 411c, but the amount of silver in the intermetallic compound 411c is an extremely small amount that is difficult to detect in EDX analysis.

[0044] The intermetallic compound 411c is formed between the metal wire 411 and the co-deposited portion 42 by the shield layer 4, so that the co-deposited portion 42 is difficult to peel off from the surface of the metal wire 411 and a gap is difficult to occur between the metal wire 411 and the co-deposited portion 42 when the coaxial cable 1 is repeatedly bent or twisted. Thus, in the coaxial cable 1, even when bending or twisting is applied, it is possible to maintain the state in which the transposition shield portion 41 is fixed by the co-deposited portion 42 from the outside of the transposition shield portion 41, and the distance between the shield layer 4 and the conductor 2 is difficult to change. Therefore, in the coaxial cable 1, it is difficult to cause a decrease in the shielding effect due to bending or twisting, and it is also difficult to cause a sharp attenuation in a predetermined frequency band. The thickness of the layer of the intermetallic compound 411c is found, for example, by observing the cross section (a section perpendicular to the longitudinal direction of the coaxial cable 1) of the coaxial cable 1 using an optical microscope or an electron microscope.

[0045] The plating layer 411b composed of silver remains in the metal wire 411 of the portion not in contact with the co-deposited portion 42 (the metal wire 411 of the portion not in contact with the molten tin at the time of plating). That is, the plating layer 411b composed of silver remains in the metal wire 411 of the portion on the inner side (the insulator 3 side) in the cable radial direction. That is, in the shield layer 4 in the coaxial cable 1 of the present embodiment, the electric conductivity of the inner peripheral portion 4b in which the plurality of metal wires 411 are not covered with the co-deposited portion 42 and the plating layer 411b is exposed is higher than that of the outer peripheral portion 4a in which the plurality of metal wires 411 are covered with the co-deposited portion 42. In the transmission of a high-frequency signal, the current concentrates on the insulator 3 side in the shield layer 4, and thus the plating layer 411b having high electric conductivity such as silver exists in the inner peripheral portion 4b of the shield layer 4, so that it is possible to suppress a decrease in the electric conductivity of the shield layer 4 and maintain a good attenuation characteristic. The electric conductivity of the tin plating constituting the co-deposited portion 42 is 15% IACS, and the electric conductivity of the silver plating constituting the plating layer 411b is 108% IACS.

[0046] Further, the outer peripheral portion 4a herein refers to the portion of the metal wire 411 in contact with the plating (tin or the like) molten at the time of hot dipping. Also, the inner peripheral portion 4b refers to the portion in which the plating layer 411b composed of silver plating or the like remains.

[0047] (Explanation of the connecting portion 43)

[0048] The shield layer 4 has a separation portion 45 in which the metal wires adjacent to each other in the circumferential direction are separated from each other. Here, it is not necessary that all of the metal wires 411 are separated, and a contact portion in which a part of the metal wires 411 adjacent to each other in the circumferential direction are in contact with each other can exist. Further, in the contact portion, on the outer periphery of the transposition shield portion 41, there is a filled portion in which the metal wires 411 adjacent to each other in the circumferential direction are filled with the co-deposited portion 42.

[0049] Further, the shield layer 4 has a linking portion 43 in which the metal wires 411 adjacent in the circumferential direction are linked to each other by a common plating portion 42. The common plating portion 42 is preferably provided so as to cover the entire circumference of the transversely wound shield portion 41 in the circumferential and axial directions, and mechanically and electrically connects the plurality of metal wires 411. In the shield layer 4 of the coaxial cable 1 of the present embodiment, the linking portion 43 is provided between the adjacent inner peripheral portions 4b. Since the circumference of the inner peripheral portion 4b is not covered by the common plating portion 42, an air layer 44 exists between the inner peripheral portions 4b of the adjacent metal wires 411 and between the outer surface of the insulator 3 and the inner surface of the common plating portion 42 (linking portion 43). With respect to the air layer 44, the inner surface of the linking portion 43 facing the outer surface of the insulator 3 has a curved shape that is concave toward the inside of the linking portion 43. Due to having such a curved shape, it is possible to provide the air layer 44 of a predetermined size between the outer surface of the insulator 3 and the inner surface of the linking portion 43, and thus it is possible to obtain a coaxial cable 1 in which a decrease in the shielding effect is difficult to occur, and a sharp attenuation in a predetermined frequency band (for example, a frequency band up to 26 GHz) is difficult to occur.

[0050] Figure 3 is a photograph and an enlarged photograph when actually manufacturing the coaxial cable 1 and peeling the shield layer 4 to observe. As shown in Figure 3 In the present embodiment, in at least a portion of the shield layer 4, the common plating portion 42 constituting the linking portion 43 and the plating layer 411b exposed at the inner peripheral portion 4b are alternately arranged in a direction perpendicular to the length direction of the metal wire 411 when viewed from the cable radial inner side (from the surface of the insulator 3 toward the shield layer 4). That is, if the shield layer 4 is observed from the cable radial inner side, the tin constituting the common plating portion 42 and the silver constituting the plating layer 411b become in a state of being alternately arranged in a striped manner.

[0051] The linking portion 43 is provided between the adjacent inner peripheral portions 4b, and thus the common plating portion 42 is difficult to crack or peel off when a bend or a twist is applied, as compared to a case where, for example, all of the metal wires 411 adjacent in the circumferential direction are in contact with each other. That is, the linking portion 43 in which the metal wires 411 are separated from each other is constituted only by the common plating portion 42 formed by hot dipping that has a softness compared to the metal wire 411. When a bend or a twist is applied, the common plating portion 42 of the linking portion functions in a stretched manner, and improves the softness of the entire shield layer 4. Due to this, the common plating portion 42 is difficult to crack or peel off when a bend or a twist is applied. Further, with respect to the distance in which the metal wires 411 adjacent in the circumferential direction are separated from each other, if the shortest distance from the surface of one metal wire 411 to the other metal wire 411 is half or less of the outer diameter of the metal wire 411, the above-mentioned effect is easily obtained.

[0052] Also, if the thickness W (the minimum straight-line distance from the inner surface to the outer surface of the plated portion 42 of the linking portion 43) of the plated portion 42 of the linking portion 43 along the radial direction is, for example, 30% (0.3 x d) or more of the outer diameter (diameter) d of the metal wire 411, it is difficult for a crack to occur in the plated portion 42. In particular, in a case where the thickness W of the plated portion 42 in the linking portion 43 is the same as or greater than the outer diameter (diameter) d of the metal wire 411, the joining strength of the metal wires 411 to each other becomes greater, and it is more difficult for a crack to occur. Also, in the coaxial cable 1, the plated portion 42 has the above-described linking portion 43, and thus, when the cable assembly is performed, the shielding layer 4 is easily removed while the plurality of metal wires 411 constituting the transposed shield portion 41 are spirally wound in the winding direction of the plurality of metal wires 411 in a state of being in close contact with the plated portion 42. As an upper limit value of the thickness W of the plated portion 42 in the linking portion 43, it can be, for example, 130% (1.3 x d) of the outer diameter d of the metal wire 411. Further, the outer diameter d of the metal wire 411 is, for example, 0.209 mm or more and 1.020 mm or less. The thickness W of the linking portion 43 and the outer diameter d of the metal wire 411 are, for example, found 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.

[0053] For example, if the shielding layer 4 is constituted only by the transposed shield portion 41, a gap occurs between the metal wires 411, which leads to a decrease in noise characteristics. Also, due to the influence of the gap occurring between the metal wires 411, a phenomenon called a frequency band gap, in which sharp attenuation occurs in a predetermined frequency band (for example, a frequency band of 10 GHz to 25 GHz), can occur. As described in the present embodiment, the plated portion 42 formed by hot-dip plating is provided so as to cover the entire periphery of the transposed shield portion 41, and thus it is possible to block the gap between the metal wires 411 with the plated portion 42, and it is possible to improve the shielding effect. Thus, it is difficult for a loss in signal transmission to occur. Also, since the gap between the metal wires 411 disappears, it is possible to suppress the occurrence of the frequency band gap.

[0054] Also, the plated portion 42 is provided so as to cover the periphery of the transposed shield portion 41, and thus, when the cable end portion is subjected to end processing in which the sheath 5 is removed to expose the shielding layer 4, the metal wires 411 are difficult to be untangled, and thus it is possible to easily perform the end processing. Also, by providing the plated portion 42 so as to cover the periphery of the transposed shield portion 41, it is also possible to stably maintain the impedance constant in the cable length direction.

[0055] Figure 4 (a) is a photograph showing the results of analysis on a region in which silver (Ag) is present in the shielding layer 4 after being peeled from the insulator 3, Figure 4(b) is a photograph showing the results of analysis on the areas containing tin (Sn) in the stripped shielding layer 4. Figure 4 Both (a) and (b) show the state of the stripped shielding layer 4 as viewed from the radial inside of the cable, and both are at the same scale. Figure 4 In (a), the lighter-colored areas indicate the regions where silver (Ag) is present. Figure 4 In (b), the lighter-colored areas indicate the regions where tin (Sn) is present. Furthermore, Figure 4 (a) and (b) are images obtained by element mapping from data obtained from EDX analysis using SEM.

[0056] like Figure 4 As shown in (a) and (b), in the shielding layer 4, when viewed from the radial inner side of the cable, the width of the area where silver (Ag) is present is greater than the width of the area where tin (Sn) is present. That is, in this embodiment, when viewed from the radial inner side of the cable, the width of the plating layer 411b exposed in the inner peripheral portion 4b is greater than the width of the co-plated portion 42 constituting the connecting portion 43. The width referred to here refers to the width of the plating layer 411b and the co-plated portion 42 in the arrangement direction ( Figure 5 The width in the vertical direction of (a) and (b), and refers to the width in the direction perpendicular to the length direction of the metal wire 411.

[0057] When the current (shielding current) flows from the insulator 3 to the shielding layer 4, and this shielding current flows to the plating layer 411b, which is made of silver with high conductivity, the loss is reduced and the transmission characteristics are improved. Therefore, as shown in this embodiment, when viewed from the radial inside of the cable, by making the width of the plating layer 411b larger than the width of the co-plated portion 42 (connecting portion 43), the shielding current can easily flow to the plating layer 411b, thereby improving the transmission characteristics. In particular, the larger the width of the plating layer 411b, the larger the area of ​​the inner peripheral portion 4b, and the farther the distance from the insulator 3 to the inner surface of the co-plated portion 42 (connecting portion 43), the more difficult it is for the shielding current to flow to the co-plated portion 42, which is made of tin, and the transmission characteristics are further improved.

[0058] (Suppression of the influence of flux residue)

[0059] As described above, when the plated portion 42 is formed, the flux is applied around the shield portion 41, and then introduced into the plating bath 104 to form the plated portion 42 by hot dipping. The inventors have conducted research, and as a result, it has been confirmed that even after the plated portion 42 is formed, the residue of the flux remains on the shield layer 4. It has been found that the residue of the flux exists in a portion that does not come into contact with the molten tin at the time of hot dipping, that is, the inner peripheral portion 4b in which the metal wire 411 is not covered with the plated portion 42 and the plated layer 411b is exposed. As described above, since the flux contains chlorine, if the residue of the flux exists, there is a concern that corrosion occurs in the plated portion 42 made of tin due to the influence of the chlorine contained in the residue. If corrosion occurs in the plated portion 42, for example, there is a possibility that a crack occurs in the connecting portion 43, or a hole that penetrates the connecting portion 43 in the radial direction is generated, and thus there is a concern that the shielding effect is reduced and the transmission characteristics are deteriorated.

[0060] Therefore, in the present embodiment, by reducing the chlorine, which is a component of the flux, remaining in the inner peripheral portion 4b, a coaxial cable 1 in which corrosion is less likely to occur in the plated portion 42 and which has excellent corrosion resistance is realized. More specifically, in the coaxial cable 1 of the present embodiment, the area of the region in which chlorine exists in the face of the shield layer 4 on the side of the insulator 3 after the insulator 3 is peeled is 5% or less (0% or more and 5% or less) of the area of the analysis region in the range of 0.015 mm 2 0.300 mm 2 When the element analysis is performed in any of the following analysis regions, the area of the region in which chlorine exists, that is, the chlorine existing region, is 5% or less (0% or more and 5% or less) of the area of the analysis region. Hereinafter, the method of analyzing the chlorine existing region will be described in detail.

[0061] (Analysis of Chlorine Existing Region)

[0062] Figure 5 is a flowchart showing the steps when the chlorine existing region is analyzed. As shown in Figure 6 first, in step S1, the shield layer 4 is peeled from the insulator 3 in the coaxial cable 1 that is the evaluation target. Thereafter, in step S2, any region of the face of the shield layer 4 on the side of the insulator 3 (the face on the inner side in the cable radial direction, the face on the side of the inner peripheral portion 4b) after the peeling is set as an analysis region, and an image (hereinafter, referred to as an SEM image) of the analysis region is acquired by SEM.

[0063] As for the analysis region, if it is set too wide, there is a concern that the evaluation accuracy is poor, and if it is set too narrow, there is a concern that the area of the region where chlorine exists as an evaluation object differs greatly depending on the selection method of the analysis region. Therefore, the size of the analysis region (i.e., the magnification of the SEM) needs to be appropriately set according to the size of the coaxial cable 1 to be evaluated (more specifically, the thickness of the metal wire 411). The inventors and others conducted research, and as a result, it was confirmed that, in a case where the outer diameter d of the metal wire 411 that makes up the transposed shield portion 41 is 0.209 mm or more and 1.020 mm or less, by making the area of the analysis region 0.015 mm 2 or more and 0.300 mm 2 or less, appropriate evaluation can be performed.

[0064] After that, in step S3, elemental analysis is performed by EDX analysis, and an image in which chlorine is mapped on the SEM image (hereinafter referred to as a chlorine mapping image) is acquired. After that, in step S4, by performing image analysis of the chlorine mapping image, a region where chlorine exists on the analysis region, i.e., a chlorine existing region, is extracted. At this time, binarization processing of the region where chlorine exists and the region where chlorine does not exist is performed within the analysis region. Also, when the binarization processing is performed, the area of only the region where chlorine exists within 2 μm 2 or more of the region is extracted. It is desirable to calibrate the above region. This is because a region that is too small within the region where chlorine exists can not be chlorine from the residue of the flux, and can be noise in terms of analysis accuracy.

[0065] After that, in step S5, the area of the chlorine existing region is calculated from the image after the binarization processing. As described above, by the binarization processing, the area of the region where chlorine exists within 2 μm 2 or more is not included in the chlorine existing region, and thus in the present embodiment, in the chlorine mapping image, the area of the region where chlorine exists is 2 μm 2 or more. The sum of the areas of the above regions is the area of the chlorine existing region. After that, in step S6, the area ratio of the chlorine existing region with respect to the analysis region is calculated by the following formula.

[0066] Area ratio = {(area of the chlorine existing region) / (area of the analysis region)} x 100

[0067] (Details of analysis of the chlorine existing region)

[0068] Two coaxial cables 1 for which there was no concern of degradation due to the residue of chlorine were prepared, and elemental analysis was performed on the coaxial cables 1. In the two coaxial cables 1, the outer diameter d of the metal wire 411 was set to 0.209 mm and 1.020 mm, respectively. Figure 6(a) shows an image obtained by SEM in a coaxial cable 1 with an outer diameter d of 0.209 mm for the metal wire 411. Furthermore, Figure 6 (b) shows a SEM image obtained in a coaxial cable 1 with an outer diameter d of 1.020 mm for the metal wire 411. The analysis region 51 is the entire SEM image, and the area of ​​the analysis region 51 is the area of ​​the entire SEM image. Figure 6 In (a), the SEM magnification was 800x, and the area of ​​the analysis region 51 was 18276 μm. 2 (0.018mm 2 ). Figure 6 In (b), the SEM magnification was 200x, and the area of ​​the analysis region 51 was 282238 μm. 2 (0.28mm 2 Furthermore, here, as a SEM, the S-4800 manufactured by Hitachi High Technology Corporation is used.

[0069] exist Figure 7 In cases (a) and (b) respectively, elemental analysis was performed using EDX analysis, and chlorine was mapped onto the SEM image to obtain a chlorine-mapped image. Figure 7 (a) and (b) show the obtained chlorine mapping images, respectively. Figure 7 In (a) and (b), the lighter-colored areas indicate the regions where chlorine is present, namely chlorine region 52. Furthermore, elemental analysis was performed here using Octane Elect Super from EDAX.

[0070] Afterwards, based on the obtained Figure 7 The chlorine mapping images (a) and (b) were analyzed using a microscope to determine the area of ​​the chlorine-containing region 52. Then, binarization was performed within the analysis region 51, separating the chlorine-containing and non-chlorine-containing regions. The area of ​​the chlorine-containing region 52 was determined based on the binarized image. Furthermore, in the binarization process, the area of ​​the chlorine-containing region extracted only from the chlorine mapping image was set to 2 μm. 2 The above areas were calibrated. The results, in... Figure 7 In example (a), the area of ​​region 52 where chlorine is present is 601 μm. 2 ,exist Figure 7 In example (b), the area of ​​the chlorine-containing region 52 is 12302 μm. 2 In addition, the Keyence VHX-5000 microscope was used.

[0071] Next, the ratio (area ratio) of the area of ​​the chlorine-containing region 52 to the area of ​​the analytical region 51 is calculated. Figure 7In the example of (a), the area of the analysis region 51 was 18276 μm 2 , and the area of the chlorine presence region 52 was 601 μm 2 . Thus, the area of the chlorine presence region 52 was 3.289% of the area of the analysis region 51. Similarly, in the example of (b), the area of the analysis region 51 was 282238 μm 2 , and the area of the chlorine presence region 52 was 12302 μm 2 . Thus, the area of the chlorine presence region 52 was 4.359% of the area of the analysis region 51. The above analysis results are collectively shown in Table 1. Outer diameter of the metal wire

[0072] Table 1

[0073] 0.209 mm 1.020 mm Area of the analysis region Area of the region where chlorine is present 18276 μm 2 ]] 282 238 μm 2 ]] Area ratio of the region where chlorine is present relative to the analysis area 601 μm 2 ]] 12302 μm 2 ]] Figure 8 3.289％ 4.359％

[0074] As shown in Table 1, it was found that in both coaxial cables 1, the area ratio of the chlorine presence region 52 with respect to the analysis region 51 (Cl area ratio) was 5% or less. That is, by making the area ratio of the chlorine presence region 52 with respect to the analysis region 51 5% or less, a coaxial cable 1 in which deterioration caused by the presence of chlorine is suppressed can be obtained. Furthermore, according to Table 1, the area of the analysis region 51 was 18276 μm 2 , 282238 μm 2 , respectively, in the two coaxial cables 1. According to the inventors' insight, by making the area of the analysis region 51 0.015 mm 2 or more and 0.300 mm 2 or less (more preferably 0.018 mm 2 or more and 0.280 mm 2 or less), the area ratio of the chlorine presence region 52 can be evaluated with high precision.

[0075] (Evaluation of Characteristics of Coaxial Cable 1)

[0076] ​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 forming PFA (perfluoroalkoxyalkane) through tubular extrusion; 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 8 The measurement results are shown.

[0077] like Figure 5 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 gaps were suppressed. Figure 9 The results confirmed that there are no unused frequency bands below 25 GHz.

[0078] (Cable assembly)

[0079] Next, the cable assembly using coaxial cable 1 will be described. Figure 9 This is a cross-sectional view showing the end portion of the cable assembly according to this embodiment.

[0080] like Figure 9 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.

[0081] Terminal component 11 is, for example, a connector, a sensor, a substrate mounted in a sensor, or a substrate in an electronic device. ​ 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.

[0082] In the end portion of the coaxial cable 1, the sheath 5 is removed from a portion of a predetermined length from the end to expose the shield layer 4, and further, the end portion of the exposed shield layer 4 and the insulator 3 is removed to expose the conductor 2. The exposed conductor 2 is fixed to the signal electrode 12 by a solder or the like connecting material 14, and the conductor 2 is electrically connected to the signal electrode 12. Also, the exposed shield layer 4 is fixed to the ground electrode 13 by a solder or the like connecting material 15, and the shield layer 4 is electrically connected to the ground electrode 13. Further, the connection of the conductor 2 and the shield layer 4 can be made without using the solder or the like connecting material 14, 15, and for example, the conductor 2 and the shield layer 4 can be fixed to a metal member for fixation by riveting or the like to connect the conductor 2 and the shield layer 4. Also, in the case where the terminal member 11 is a connector or a sensor, the conductor 2 and the shield layer 4 can be directly connected to the electrode or the element.

[0083] (Action and Effect of Embodiment)

[0084] As described above, in the coaxial cable 1 of the present embodiment, the shield layer 4 has the cross-wound shield portion 41 in which a plurality of metal wires 411 having a plating layer 411b on the outermost layer are spirally wound around the insulator 3, and the one-plating portion 42 which covers the periphery of the cross-wound shield portion 41 and is formed by hot-dip plating, the shield layer 4 has the inner peripheral portion 4b in which the plurality of metal wires 411 are exposed with the plating layer 411b not being covered by the one-plating portion 42, the area of the region in which chlorine exists, i.e., the chlorine-existence region 52, on the plating layer 411b exposed on the inner peripheral portion 4b is 5% or less of the area of the analysis region 51 in the surface of the shield layer 4 on the insulator 3 side after peeling the insulator 3, and the area of the chlorine-existence region 52 is 0.015 mm 2 and 0.300 mm 2 When element analysis is performed in any of the analysis regions 51 below, the area of the region in which chlorine exists, i.e., the chlorine-existence region 52, on the plating layer 411b exposed on the inner peripheral portion 4b is 5% or less of the area of the analysis region 51.

[0085] By being thus configured, the shield layer 4 is connected on substantially the entire periphery via the one-plating portion 42, the gap between the metal wires 411 of the cross-wound shield portion 41 can be plugged by the one-plating portion 42, the noise characteristic can be improved, and the occurrence of a frequency band gap can be suppressed. That is, according to the present embodiment, it is possible to realize the coaxial cable 1 which is difficult to cause a decrease in the shielding effect and difficult to cause a sharp attenuation in a predetermined frequency band (for example, a frequency band up to 26 GHz). Further, by reducing the chlorine-existence region 52, it is possible to suppress the corrosion of the one-plating portion 42 by the remaining chlorine, and thus it is possible to realize the coaxial cable 1 in which the characteristic deterioration is less even if used for a long period of time. Further, the one-plating portion 42 is provided so as to enter between the metal wires 411, it is possible to improve the joining strength of the metal wires 411, and the one-plating portion 42 is difficult to peel.

[0086] (Summary of Embodiment)

[0087] Next, the technical ideas grasped from the above-described embodiments are described with reference to symbols and the like in the embodiments. Note that each of the symbols and the like described below does not limit the components in the claims to the components and the like specifically shown in the embodiments.

[0088] [1] A coaxial cable 1 comprising: a conductor 2; an insulator 3 covering a periphery of the conductor 2; a shield layer 4 covering a periphery of the insulator 3; and a sheath 5 covering a periphery of the shield layer 4, the shield layer 4 having: a cross-wound shield portion 41 configured by spirally winding a plurality of metal wires 411 having a plating layer 411b on an outermost layer around the insulator 3; and a collectively plated portion 42 covering a periphery of the cross-wound shield portion 41, formed by hot-dip plating, an area of a region in which chlorine exists in a surface of the shield layer 4 on the insulator 3 side after peeling the insulator 3 being 0.015 mm 2 0.300 mm 2 When element analysis is performed in any of the analysis regions 51 below, an area of a region in which chlorine exists on the analysis region 51, that is, a chlorine existing region 52 is 5% or less of an area of the analysis region 51.

[0089] [2] The coaxial cable 1 according to [1], wherein the element analysis is performed by energy dispersive X-ray spectroscopy using a scanning electron microscope.

[0090] [3] The coaxial cable 1 according to [1] or [2], wherein, after the element analysis, binary processing of a region in which chlorine exists and a region in which chlorine does not exist in the analysis region 51 is performed, and an area of the chlorine existing region 52 is calculated from an image after the binary processing.

[0091] [4] The coaxial cable 1 according to [3], wherein the area of the chlorine existing region 52 is an area of the region in which chlorine exists in the analysis region 51 being 2 μm 2 a sum of areas of the regions above.

[0092] [5] A coaxial cable 1, comprising: a conductor 2; an insulator 3 covering a periphery of the conductor 2; a shield layer 4 covering a periphery of the insulator 3; and a sheath 5 covering a periphery of the shield layer 4, the shield layer 4 having: a cross-wound shield portion 41 configured by spirally winding a plurality of metal wires 411 having a plating layer 411b on an outermost layer around the insulator 3; and a collectively plated portion 42 covering a periphery of the cross-wound shield portion 41 and formed by hot-dip plating, the shield layer 4 having, at a separation portion 45 at which circumferentially adjacent ones of the metal wires 411 are separated from each other, a connection portion 43 at which the circumferentially adjacent ones of the metal wires 411 are connected to each other by the collectively plated portion 42, and the shield layer 4 having an inner peripheral portion 4b at which the plurality of metal wires 411 are not covered by the collectively plated portion 42 and at which the plating layer 411b is exposed, the connection portion 43 being provided between adjacent ones of the inner peripheral portion 4b.

[0093] [6] The coaxial cable 1 according to any one of [1] to [5], wherein an outer diameter of the metal wire 411 of the cross-wound shield portion 41 is 0.209 mm or more and 1.020 mm or less.

[0094] [7] The coaxial cable 1 according to any one of [1] to [5], wherein, in at least a portion of the shield layer 4, the collectively plated portion 42 configuring the connection portion 43 and the plating layer 411b exposed at the inner peripheral portion 4b are alternately arranged in a direction perpendicular to a length direction of the metal wire 411 when viewed from a cable radial inner side.

[0095] [8] The coaxial cable 1 according to any one of [1] to [6], wherein, when viewed from a cable radial inner side, a width of the plating layer 411b exposed at the inner peripheral portion 4b is larger than a width of the collectively plated portion 42 configuring the connection portion 43, a conductivity of the plating layer 411b is higher than a conductivity of the collectively plated portion 42, the plating layer 411b is configured by silver, and the collectively plated portion 42 is configured by tin.

[0096] [9] The coaxial cable 1 according to any one of [1] to [7], wherein the shield layer 4 has an outer peripheral portion 4a at which the plurality of metal wires 411 are covered by the collectively plated portion 42, and the outer peripheral portion 4a has an intermetallic compound 411c between the plurality of metal wires 411 and the collectively plated portion 42.

[0097]

[10] A cable assembly 10, comprising: the coaxial cable 1 according to any one of [1] to [9]; and a terminal member 11 integrally provided to at least one of end portions of the coaxial cable 1.

[0098] The above describes embodiments of the present application, but the above-described embodiments do not limit the application of the claims. Also, it should be noted that the combination of features described in the embodiments is not necessarily all required to be a solution to solve the problem of the application.

[0099] Also, the present application can be appropriately modified and implemented without departing from the scope of the gist thereof. For example, in the above-described embodiments, elemental analysis was performed by EDX analysis using a SEM, but elemental analysis can also be performed by other methods, for example, elemental analysis can also be performed by analysis using an Electron Probe Micro Analyzer (EPMA), analysis using Auger electron spectroscopy (AES).

Claims

1. A coaxial cable, characterized by Possessing: a conductor; an insulator covering the periphery of the conductor; a shield layer covering the periphery of the insulator; and a jacket covering the periphery of the shield layer, the shield layer has a cross-wound shield portion configured by spirally winding a plurality of metal wires having plating layers on the outermost layers around the insulator, and a collective plating portion covering the periphery of the cross-wound shield portion and formed by hot-dip plating, the shield layer has, at a separation portion where circumferentially adjacent ones of the metal wires are separated from each other, a connection portion where circumferentially adjacent ones of the metal wires are connected to each other by the collective plating portion, and the shield layer has inner peripheral portions where the plurality of metal wires are not covered by the collective plating portion and the plating layers are exposed, the connection portion is provided between adjacent ones of the inner peripheral portions, 0.015 mm or less in the surface of the insulator side of the shielding layer after peeling the insulator 2 0.300 mm or less 2 When element analysis is performed in any of the following analysis regions, the area of the region in which chlorine exists on the analysis region, that is, the chlorine existing region is 5% or less of the area of the analysis region.

2. The coaxial cable according to claim 1, wherein the elemental analysis is performed by energy dispersive X-ray spectroscopy using a scanning electron microscope.

3. The coaxial cable according to claim 1, wherein after the elemental analysis, a binary processing is performed on a region where chlorine exists and a region where chlorine does not exist within the analysis region, and an area of the region where chlorine exists is calculated based on an image after the binary processing.

4. The coaxial cable according to claim 3, wherein The area of the region where chlorine exists is an area of 2 μm 2 The sum of the areas of the above regions.

5. A coaxial cable characterized by, Possessing: a conductor; an insulator covering the periphery of the conductor; a shield layer covering the periphery of the insulator; and a jacket covering the periphery of the shield layer, the shield layer has a cross-wound shield portion configured by spirally winding a plurality of metal wires having plating layers on the outermost layers around the insulator, and a collective plating portion covering the periphery of the cross-wound shield portion and formed by hot-dip plating, the shield layer has, at a separation portion where circumferentially adjacent ones of the metal wires are separated from each other, a connection portion where circumferentially adjacent ones of the metal wires are connected to each other by the collective plating portion, and the shield layer has inner peripheral portions where the plurality of metal wires are not covered by the collective plating portion and the plating layers are exposed, the connection portion is provided between adjacent ones of the inner peripheral portions, in at least a portion of the shield layer, the collective plating portion constituting the connection portion and the plating layer exposed at the inner peripheral portion are alternately arranged in a direction perpendicular to a length direction of the metal wires when viewed from a radially inner side of the cable, a width of the plating layer exposed at the inner peripheral portion is larger than a width of the collective plating portion constituting the connection portion when viewed from the radially inner side of the cable.

6. The coaxial cable according to any one of claims 1 to 5, wherein an outer diameter of the metal wires of the cross-wound shield portion is 0.209 mm or more and 1.020 mm or less.

7. The coaxial cable according to any one of claims 1 to 5, wherein in at least a portion of the shield layer, the collective plating portion constituting the connection portion and the plating layer exposed at the inner peripheral portion are alternately arranged in a direction perpendicular to a length direction of the metal wires when viewed from a radially inner side of the cable.

8. The coaxial cable according to any one of claims 1 to 5, wherein the plating layer has a higher electrical conductivity than the plating layer of the one-plating portion, the plating layer is composed of silver and the one-plating portion is composed of tin.

9. The coaxial cable according to any one of claims 1 to 5, wherein the shield layer has a peripheral portion in which the plurality of metal wires are covered with the one-plating portion, and the peripheral portion has intermetallic compounds between the plurality of metal wires and the one-plating portion.

10. A cable assembly, characterized by provided with: the coaxial cable according to any one of claims 1 to 9; and a terminal member integrally provided to at least one of end portions of the coaxial cable.

Images