JP7340384B2 - Small diameter coaxial cable with excellent flexibility - Google Patents

Description

The present invention relates to a coaxial cable, and more particularly to a coaxial cable that is small in diameter, has good flexibility, and has excellent flexibility such that its characteristics do not easily deteriorate even when it is bent or bent back.

Coaxial cables have excellent shielding properties against noise and the like, and are therefore used for transmitting high frequency signals. Such coaxial cables have a problem in that when an external force is applied to the cable, the insulator deforms, impedance changes, reflection loss occurs, and transmission efficiency decreases. Furthermore, coaxial cables used for internal antenna wiring and semiconductor devices are required to have a smaller diameter, and are also required to have good flexibility and bending characteristics.

In response to these demands, Patent Document 1 proposes a coaxial cable that satisfies shielding characteristics, flexibility, reduced diameter configuration, bending resistance, and economic efficiency, and improves terminal processability. This coaxial cable has a structure in which a center conductor, an insulator, an outer conductor having a horizontally wound shield structure, and a jacket are sequentially laminated coaxially. If the outer jacket is PFA, the insulator is formed by fluorinated PFA, and if the outer jacket is FEP or FTFE, the insulator is one of fluorinated FEP, PFA, and fluorinated PFA. formed by. Furthermore, a tape layer with metal vapor-deposited or plated is provided between the insulator and the external conductor, the horizontal winding angle of the horizontal winding of the external conductor is set to 70 to 85 degrees, and the center conductor is made of multiple wires or It has been proposed that it is preferable to use a single wire conductor.

Japanese Patent Application Publication No. 2007-188782

In recent years, coaxial cables have been used to transmit high-frequency signals in electronic devices that are becoming smaller and smaller, such as computers, smartphones, and tablet devices. There is a demand for smaller diameters. In particular, coaxial cables used for internal antenna wiring and semiconductor devices are expected to have excellent flexibility to facilitate routing during wiring, as well as to avoid problems caused by repeated bending stress during equipment use. ing.

However, conventional coaxial cables such as those disclosed in Patent Document 1 have a solid structure in which the insulator provided on the conductor is thick, and furthermore, the horizontal winding angle of the horizontal winding of the outer conductor is 70° to 85° and the winding pitch is It is large at 12-13mm. Therefore, it was somewhat hard and had insufficient flexibility. Further, since the horizontally wound shield arranges conductors having the same outer diameter (for example, 0.05 mm), there is a gap, which causes bending starting from the gap, resulting in a shortened bending life.

Furthermore, if a coaxial cable is provided with a thin metal foil as the first outer conductor layer around the outer periphery of the insulator and a braided wire as the second outer conductor layer on the outer periphery of the insulator, bending or returning the coaxial cable during wiring will cause damage to the coaxial cable. The twists peculiar to the braided structure sometimes caused wrinkles in the thin metal foil attached vertically. The braided structure has a high degree of tightness and is said to strongly restrain the vertically attached metal foil, thereby suppressing the occurrence of wrinkles. However, when a coaxial cable is bent and returned with the thin metal foil biting into the strands of a thick braided structure, the existence of the strands may actually cause wrinkles. .

The present invention has been made to solve the above problems, and its purpose is to provide a coaxial cable that is small in diameter, has good flexibility, and exhibits good flexibility even when bent and returned. be.

The coaxial cable according to the present invention includes a center conductor, a low dielectric constant insulator provided on the outer periphery of the center conductor, and a first outer conductor made of a metal resin tape longitudinally attached to the outer periphery of the insulator. A coaxial cable comprising a second outer conductor made of a thin metal wire wound horizontally around the outer periphery of the first outer conductor, and an outer jacket covering the second outer conductor, the second outer conductor comprising: , characterized in that the insulator is horizontally wound in a single layer at a pitch of 0.5 to 11 times the outer diameter of the insulator.

According to this invention, since the insulator has a low dielectric constant, the outer diameter of the insulator can be reduced for the same dielectric constant, and diameter reduction can be achieved. As a result, rigidity can be reduced and flexibility can be increased. Since the second outer conductor has a single layer structure made of horizontally wound metal wires instead of a braided structure with twists, the metal resin tape constituting the first outer conductor is It is possible to prevent wrinkles from forming in the metal layer. By setting the single-layer horizontal winding pitch of the thin metal wire constituting the second outer conductor within the above range, even when bending or unbending the second outer conductor, gaps or lifting are unlikely to occur in the second outer conductor, and there is no problem with the metal resin tape. It also does not easily cause wrinkles. As a result, a coaxial cable whose characteristics are less likely to deteriorate even when bent can be obtained.

In the coaxial cable according to the present invention, the winding pitch of the second outer conductor is 0.5 to 11 mm. According to this invention, since the winding pitch is within the above range, the "tension" of the second outer conductor as a whole is reduced, the rigidity is reduced, and the flexibility is improved.

In the coaxial cable according to the present invention, a gap formed in the second outer conductor is equal to or less than an outer diameter of the thin metal wire. According to this invention, for example, when the outer diameter of the thin metal wire is 0.05 mm, the gap is 0.05 mm or less, so bending starting from the gap is less likely to occur, and the bending life can be improved. Furthermore, if they are lined up so as to completely eliminate the gap, there will be a part where the second external conductor cannot be lined up on top of the insulator, and a part of the thin metal wire will pop out to the outer cover side and float. It's easy to do. In this case, the protruding thin metal wire becomes a starting point, and bending occurs at that starting point, resulting in a shortened bending life.

In the coaxial cable according to the present invention, the outer diameter of the thin metal wire is 0.04 to 0.1 times the outer diameter of the insulator.

In the coaxial cable according to the present invention, a metal resin tape is longitudinally attached so that the first outer conductor has a thickness of 0.004 to 0.036 mm.

In the coaxial cable according to the present invention, the width of the metal-resin tape is 3.5 to 4.5 times the outer diameter of the insulator, and the metal-resin tape is arranged so that the metal surface faces outward and both ends partially overlap. Attach the tape vertically.

In the coaxial cable according to the present invention, the insulator is made of resin having a dielectric constant of 2.0 to 2.5. Preferably, this insulator has a hollow or foamed structure.

According to the present invention, it is possible to provide a coaxial cable that is small in diameter, has good flexibility, and exhibits good flexibility even when bent and returned.

FIG. 1 is a perspective configuration diagram showing an example of a coaxial cable according to the present invention. (A) is an example of a hollow structure, and (B) is an example of a foamed or solid structure. FIG. 7 is an explanatory diagram of the cross-sectional form of the second external conductor, showing (A) a case where no gap or lifting occurs, (B) a case where a gap occurs, and (C) a case where lifting occurs. It is an explanatory view showing the mode of a flexibility test. FIG. 3 is an explanatory diagram showing an aspect of a bending test.

Embodiments of a coaxial cable according to the present invention will be described with reference to the drawings. Note that the present invention includes inventions having the same technical idea as the embodiments described below and the forms described in the drawings, and the technical scope of the present invention is limited only to the description of the embodiments and drawings. It's not something you can do.

[coaxial cable]
As shown in FIG. 1, a coaxial cable 10 according to the present invention includes a center conductor 11, a low dielectric constant insulator 12 provided on the outer periphery of the center conductor 11, and a metal resin longitudinally attached to the outer periphery of the insulator 12. A coaxial device comprising a first outer conductor 13a made of tape, a second outer conductor 13b made of thin metal wire wound horizontally around the outer periphery of the first outer conductor 13a, and an outer cover 14 covering the second outer conductor. In the cable 10, the second outer conductor 13b is wound horizontally in a single layer at a pitch of 90.5 to 11 times the outer diameter of the insulator 12.

In this coaxial cable 10, (a) the insulator 12 has a low dielectric constant; therefore, if the dielectric constant is the same, the outer diameter of the insulator 12 can be reduced, and the diameter can be reduced. As a result, rigidity can be reduced and flexibility can be increased. In particular, when the insulator 12 has a hollow or foamed structure, the dielectric constant is low and the material density of the insulator 12 is small, so that the insulator 12 can be made soft. When the insulator 12 has a solid structure, the outer diameter of the insulator 12 is reduced by lowering the dielectric constant using a low dielectric constant material, thereby achieving a thinner diameter. Reducing the diameter reduces rigidity and increases flexibility. (B) Since the second outer conductor 13b has a single layer structure made of horizontally wound metal wires instead of a braided structure with twists, the first outer conductor 13a is formed due to the twists like in a braided structure. This can prevent wrinkles from forming in the metal layer of the metal-resin tape. (c) By setting the single-layer horizontal winding pitch of the thin metal wire constituting the second external conductor 13b within the above range, even if the second external conductor 13b is bent or unbended, gaps or lifting are unlikely to occur. Wrinkling of the metal resin tape is also less likely to occur. As a result, a coaxial cable 10 whose characteristics are unlikely to deteriorate even when bent can be obtained.

Each component will be explained in detail below.

As shown in FIG. 1, the coaxial cable 10 includes a center conductor 11, an insulator 12 provided continuously in the longitudinal direction on the outer periphery of the center conductor 11, and an outer conductor 13 provided on the outer periphery of the insulator 12. (13a, 13b) and an outer cover 14 that covers the outer conductor 13.

(center conductor)
The center conductor 11 is composed of one strand extending in the longitudinal direction of the coaxial cable 10, or is composed of a plurality of strands twisted together. The type of wire is not particularly limited as long as it is a metal with good conductivity, but it may be a metal conductor with good conductivity such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, copper-aluminum composite wire, or the surface thereof. Preferred examples include those on which a plating layer is applied. From the viewpoint of high frequencies, copper wires and copper alloy wires are particularly preferred. As the plating layer, a solder plating layer, a tin plating layer, a gold plating layer, a silver plating layer, a nickel plating layer, etc. are preferable. The cross-sectional shape of the wire is also not particularly limited, but the wire may have a circular or substantially circular cross-sectional shape, or may have a rectangular shape.

The cross-sectional shape of the center conductor 11 is also not particularly limited. It may be circular (including elliptical) or rectangular, but is preferably circular. The outer diameter of the center conductor 11 is desirably as large as possible so as to reduce electrical resistance (AC resistance, conductor resistance), but in order to reduce the final outer diameter of the coaxial cable 10, for example, 0.09 A range of about 1 mm can be mentioned. An insulating film (not shown) may be provided on the surface of the center conductor 11 if necessary. The type and thickness of the insulating film are not particularly limited, but for example, one that decomposes well during soldering is preferable, and a thermosetting polyurethane film can be preferably mentioned.

(Insulator)
The insulator 12 is a low dielectric constant insulating layer provided continuously in the longitudinal direction around the outer periphery of the center conductor 11 . Examples of the structure of the insulator 12 include a hollow structure shown in FIG. 1(A), and a foamed structure or solid structure shown in FIG. 1(B). The insulator 12 generally has a solid structure, but preferably has a hollow structure or a foamed structure. Note that the foamed structure is shown in FIG. 1(B) as a cross section similar to a solid structure because the voids generated by foaming are minute.

When the insulator 12 has a hollow structure, it has a void inside the structure as shown in FIG. Further, the dielectric constant can be further reduced. For example, in the case of a hollow structure with a hollow ratio of 40%, the dielectric constant can be lowered from about 2.1 to about 1.6. Therefore, when the dielectric constants of the insulators 12 are made the same, the outer diameter of the insulators 12 can be reduced, and the diameter can be reduced to improve flexibility. For example, in order to make the characteristic impedance of AWG 29 wire (0.287mm) 50Ω, a solid structure requires an outer diameter of about 0.9mm, but by creating a hollow structure, the outer diameter can be reduced to 0.83mm. The outer diameter can be reduced by about 7%. By reducing the dielectric constant in this way, the diameter of the coaxial cable 10 can be reduced, for example, by about 7%.

When the insulator 12 has a foam structure, it has a cross-sectional form similar to that of a solid structure, as shown in FIG. 1B, except that it has minute foam pores as voids. The insulator 12 made of a foamed structure has a lower material density and can be made softer, as in the case of a hollow structure. In addition, since the dielectric constant can be further reduced, if the dielectric constants of the insulators 12 are kept the same, the outer diameter of the insulators 12 can be made smaller, realizing a thinner diameter and increasing flexibility. .

When the insulator 12 has a solid structure, by employing a low dielectric constant material, the dielectric constant can be lowered and the outer diameter of the insulator 12 can be reduced. As a result, the diameter can be reduced, the rigidity can be reduced, and the flexibility can be increased.

The form of the insulator 12 having a hollow structure is not particularly limited, but as shown in FIG. 2, it may have a cross-sectional form in which the cavity is surrounded by an inner annular part 12a, an outer annular part 12b, and a connecting part 12c. The material of the insulator 12 is not particularly limited and can be arbitrarily selected depending on the required impedance characteristics, but for example, dielectric materials such as PFA (ε2.1), ETFE (ε2.5), FEP (ε2.1), etc. A fluororesin having a low dielectric constant of 2.0 to 2.5 is preferred, and PFA resin is particularly preferred. Note that the material of the insulator 12 may contain a coloring agent. The thickness of the insulator 12 is also not particularly limited and can be arbitrarily selected depending on the required impedance characteristics, but it is preferably within a range of about 0.15 to 1.5 mm, for example. Although the method for forming the insulator 12 is not particularly limited, the hollow structure can be easily formed by extrusion.

Insulator 12 having a foam or solid structure can be easily formed by conventional extrusion. A foamed structure differs from a resin material forming a solid structure in that the resin material contains a foaming agent. The foam structure has foam pores as voids, and the voids can lower the dielectric constant, so it can be formed with the same structural design as the hollow structure. On the other hand, in the case of a solid structure, since there is no void, a resin material with a small dielectric constant is used. By configuring the solid structure using a resin material with a low dielectric constant, the outer diameter of the insulator 12 can be reduced, and the rigidity and flexibility can be increased, as described above.

(outer conductor)
The outer conductor 13 is provided around the outer periphery of the insulator 12 . The outer conductor 13 includes a first outer conductor 13a formed by vertically attaching a metal resin tape with the metal layer side facing outward on the insulator 12, and a thin metal wire wound horizontally on the first outer conductor 13a. It has a double structure consisting of a second external conductor 13b. The outer conductor 13 having such a double structure has a large conductor cross-sectional area and can reduce insertion loss. In addition, in this application, the code|symbol 13a is also used for the metal resin tape which comprises the 1st external conductor 13a, and the code|symbol 13b is also used for the metal thin wire which comprises the 2nd external conductor 13b.

(first outer conductor)
The first external conductor 13a is formed by vertically attaching a metal resin tape on the insulator 12 (also referred to as the periphery of the insulator 12). Vertical splicing is performed with the metal layer surface constituting the metal resin tape facing outward (toward the second external conductor 13b that will be provided subsequently). A metal resin tape has a metal layer provided on a resin base material. Although the resin base material is not particularly limited, polyester films such as polyethylene terephthalate and polyethylene naphthalate can be preferably used. The thickness of the resin base material is arbitrarily selected, for example, from a range of about 2 to 20 μm. Preferred examples of the metal layer include a copper layer and an aluminum layer. Preferred examples of the metal layer include those formed on a resin base material by vapor deposition or plating, or metal foils bonded together via an adhesive layer (eg, polyester thermoplastic adhesive resin, etc.). The thickness of the metal layer is not particularly limited and varies depending on the formation method, but for those formed by vapor deposition or plating, it can be arbitrarily selected within the range of about 2 to 8 μm, and for those formed by laminating metal foil. can be arbitrarily selected from within the range of about 6 to 16 μm. Even with such a thin metal layer thickness, the second outer conductor 13b provided thereon is a horizontally wound thin metal wire, and there are no twists like in a braided structure, so the coaxial cable 10 is Even if the metal layer or metal foil is bent and unbended, wrinkles can be prevented from forming in the metal layer or metal foil.

As shown in Fig. 1, vertical attachment is performed by placing the metal resin tape in the longitudinal direction so that the resin base side of the tape is on the insulator 12 side and the metal layer side is on the outside (second external conductor side) so that they partially overlap. It is rolled up to wrap it. The width of the metal resin tape is not particularly limited, but is preferably 3.5 to 4.5 times the outer diameter of the insulator 12. Partially overlapping means overlapping in the vertical direction with a width within the range of 0.1 to 3 mm, as shown in FIG. By vertically connecting the coaxial cables 10 so as to partially overlap, it is possible to prevent cuts and gaps between the metal layers even when the coaxial cable 10 is bent or bent back. The total thickness of the metal resin tape including the partially overlapping portion is preferably within a range of about 0.004 to 0.072 mm.

The first outer conductor 13a is pressed down by a second outer conductor 13b provided thereon. As a result, it is possible to prevent the vertically attached first external conductor 13a from being twisted, and it is possible to prevent wrinkles caused by the twisting from occurring in the metal layer or metal foil of the first external conductor 13a. Therefore, even when bent or unbent, the distance between the outer conductor 13 (13a, 13b) and the center conductor 11 does not change, so phase fluctuations are less likely to occur and deterioration of signal transmission characteristics (attenuation, skew) is suppressed. be able to. In particular, even when transmitting differential signals at high speed, it is possible to suppress changes in signal transmission speed between two lines and prevent transmission characteristics from deteriorating. Furthermore, due to this outer conductor structure, no change in dielectric constant occurs even when repeated bending stress is applied.

(Second outer conductor)
As shown in FIGS. 1 and 2, the second outer conductor 13b is formed by horizontally winding a thin metal wire to form a single layer on the first outer conductor 13a. Since the single-layer horizontally wound thin metal wire does not have twists like a braided structure, wrinkles occur in the metal layer of the metal resin tape constituting the first external conductor 13a due to the twists like a braided structure. can be prevented. In addition, compared to a braided structure in which thin wires intersect to form a strand, horizontally wound metal wires are provided in a single layer with smaller gaps between the wires, so they can achieve the same effect (sealing effect, etc.). The thickness of the second outer conductor 13b can be reduced within the range in which this occurs, which is advantageous from the viewpoint of reducing the diameter of the coaxial cable 10.

The thin metal wire is not particularly limited as long as it is a thin metal wire with good conductivity that can be provided on the outer periphery of the first outer conductor 13a (vertical attachment of the metal resin tape) as the second outer conductor 13b of the coaxial cable 10. For example, various metal thin wires such as tin-plated copper wire can be preferably used.

The outer diameter of the thin metal wire is set to be larger than the gap created in the second outer conductor 13b. In other words, the gap created in the second external conductor 13b is equal to or less than the outer diameter of the thin metal wire. For example, when the outer diameter of the thin metal wire is 0.05 mm, the gap will be 0.05 mm or less, so bending starting from the gap is unlikely to occur, and the bending life can be improved. Note that if the second outer conductor 13b is lined up so as to completely eliminate the gap, there will be a part where the second outer conductor 13b cannot be lined up on the upper part of the insulator 12, and a part of the thin metal wire will protrude to the outer cover side and float. is likely to occur. In this case, the protruding thin metal wire becomes a starting point, and bending occurs at that starting point, resulting in a shortened bending life. The outer diameter of the thin metal wire thus designed is preferably 0.04 to 0.1 times the outer diameter of the insulator 12. The specific outer diameter is determined depending on the degree of the gap and the relationship with the outer diameter of the insulator 12, and may be, for example, within a range of about 0.04 to 0.1 mm. The number of thin metal wires is also arbitrarily selected depending on the outer diameter of the first outer conductor 13a, the outer diameter of the planned coaxial cable 10, and the like.

When horizontally winding the thin metal wire, the horizontal winding pitch is preferably 0.5 to 11 mm. By doing so, the "tension" of the second outer conductor as a whole is reduced and flexibility is improved. Further, by setting the horizontal winding pitch of the thin metal wire within the above range, even when bending or unbending, gaps or lifting are less likely to occur in the second outer conductor 13b, and wrinkles are less likely to be caused in the metal resin tape. As a result, a coaxial cable whose characteristics are less likely to deteriorate even when bent can be obtained.

The total thickness of the first external conductor 13a and the second external conductor 13b constituting the double-structured external conductor 13 depends on the wire diameter and number of twists of the thin metal wire used, the thickness of the metal layer of the metal resin tape, and the resin base material. It is not particularly limited as it varies depending on the thickness etc.

(outer covering)
The outer cover 14 is provided around the outer periphery of the outer conductor 13, and its material is not particularly limited as long as it has insulation properties. Although it may be provided by spirally winding a resin tape with an adhesive layer on one side, it is preferably provided by extruding the resin. In the case of resin extrusion, various resins used for the insulator 12 can be used as the constituent resin of the outer cover 14, and for example, fluororesins such as PFA, ETFE, and FEP may be used. , vinyl chloride resin, polyolefin resin such as polyethylene, or polyester resin such as polyethylene terephthalate. The thickness of the outer cover 14 can be, for example, within a range of about 0.1 to 1.0 mm.

In addition, when using a resin tape, it is possible to prevent the second outer conductor 13b (horizontally wound thin metal wire) from shifting by fusing it with the second outer conductor 13b. When using a resin tape with a fusing layer, it is wound horizontally with the fusing layer side facing the second external conductor 13b. Examples of the material of the resin tape include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide (PA), polyimide (PI), polyphenylene sulfide (PPS), and ethylene-tetrafluoroethylene copolymer (ETFE). , tetrafluoroethylene-hexafluoropropylene copolymer (FEP), fluorinated resin copolymer (perfluoroalkoxy fluororesin: PFA), polyether ether ketone (PEEK), and the like. The thickness of the resin tape is not particularly limited as long as it is thick enough to ensure the necessary dielectric strength, but it can be about 0.004 to 0.01 mm. The adhesive layer is provided on one side of the resin tape, and its material includes, for example, thermosetting resin such as polyurethane resin, polyester resin, and polyesterimide resin. The thickness of the fusion layer is also not particularly limited, but can be approximately 0.001 mm.

The final outer diameter of the obtained coaxial cable 10 is preferably within a range of about 0.6 to 3.5 mm. Such a coaxial cable 10 has a small diameter and good flexibility, and exhibits good flexibility even when it is bent and returned.

The present invention will be explained in more detail below by giving Examples. Note that the present invention is not limited to the following examples.

[Example 1]
First, a coaxial cable 10 having the form shown in FIG. 1 was produced. As the center conductor 11, a silver-plated annealed copper wire with an outer diameter of 0.203 mm was used. Next, PFA resin (manufactured by DuPont, dielectric constant 2.1) with a thickness of 0.21 mm is extruded around the outer periphery of the center conductor 11 to form a hollow structure as shown in FIG. 2, so that the outer diameter is 0.623 mm. did. Next, a double-layered outer conductor 13 consisting of a first outer conductor 13a and a second outer conductor 13b was formed. The first external conductor 13a is made of a metal resin tape having a width of 2.5 mm and a total thickness of 0.02 mm, in which copper foil with a thickness of 0.008 mm is provided on a PET base material with a thickness of 0.004 mm. They were placed vertically so that the foil side was on the outside (the side of the second external conductor 13b that would be provided later) and overlapped by a width of 0.54 mm. The portion where the metal resin tape partially overlapped had the maximum thickness of the first outer conductor 13a, which was 0.04 mm. The second outer conductor 13b is made by using 38 silver-plated annealed copper wires each having an outer diameter of 0.05 mm and wound to the left in a single layer at a pitch of 6.5 mm, and after forming the second outer conductor 13b, the outer diameter is 0.05 mm. It was set to 763 mm. Thereafter, a PFA resin (manufactured by DuPont) layer was extruded as the outer cover 14 to produce a coaxial cable 10 with an outer diameter of 0.85 mm.

In the obtained coaxial cable 10, the gap G generated in the second outer conductor 13b was 0.018 mm, which was 1/2.8 of the outer diameter D3 of the thin metal wire. The winding pitch P (6.5 mm) of the thin metal wire was 10.4 times the outer diameter D2 (0.623 mm) of the insulator 12. The width W1 (2.5 mm) of the metal resin tape was 4.01 times the outer diameter D2 (0.623 mm) of the insulator 12. The outer diameter D3 (0.05 mm) of the thin metal wire was 0.08 times the outer diameter D2 (0.623 mm) of the insulator 12. Note that the insulator 12 made of a hollow structure is made by extruding PFA resin (manufactured by DuPont) at 350° C. using a die nipple for forming hollow structures, so that the void part is an inner annular part with a thickness of 0.05 mm. 12a, a hollow structure having a cross-sectional shape surrounded by an outer annular portion 12b with a thickness of 0.05 mm and a connecting portion 12c with a thickness of 0.05 mm is molded, and the porosity is 54%.

[Example 2]
In Example 1, the outer diameter of the center conductor 11 was changed to 0.287 mm, the outer diameter of the insulator 12 was changed to 0.90 mm, and the metal resin tape was 3.5 mm wide and overlapped by a width of 0.67 mm. The number of thin metal wires was changed to 55 with a pitch of 9.0 mm, and the outer diameter after forming the second outer conductor 13b was changed to 1.08 mm. A coaxial cable of Example 2 having an outer diameter of 1.14 mm was produced in the same manner as in Example 1 except for the above.

[Example 3]
In Example 1, the number of thin metal wires was changed to 35, and after forming the second outer conductor 13b, a PET tape (resin tape) with a fusion layer having a thickness of 0.025 mm and a width of 3 mm was used as the outer cover 14. The horizontal winding pitch was changed to 1.5 mm using 1/2 wrap. A coaxial cable of Example 3 having an outer diameter of 0.86 mm was produced in the same manner as in Example 1 except for the above.

[Example 4]
In Example 1, the center conductor 11 was changed to one with an outer diameter of 0.381 mm made by twisting seven silver-plated annealed copper wires with an outer diameter of 0.127 mm at a pitch of 5 mm, and the thickness of the insulator was changed to 0.380 mm. did. The first external conductor 13a was made of a metal resin tape having a width of 4.0 mm and overlapped by a width of 0.42 mm. The number of thin metal wires in the second outer conductor 13b was 44, and the outer diameter after forming the second outer conductor 13b was changed to 1.32 mm. A PET tape (resin tape) with a fusion layer having a thickness of 0.05 mm and a width of 3.5 mm was used as the outer cover 14, and the tape was 1/3 wrapped at a horizontal winding pitch of 4 mm. A coaxial cable of Example 4 having an outer diameter of 1.40 mm was produced in the same manner as in Example 1 except for the above.

[Examples 5 to 7]
In Example 1, the number N of the thin metal wires and the horizontal winding pitch P of the thin metal wires were changed as shown in Table 1. A coaxial cable 10 having the dimensions shown in Table 1 was manufactured in the same manner as in Example 1 except for the above.

[Comparative example 1]
In Example 1, the center conductor 11 and the first outer conductor 13a were the same, and a thin metal wire braid was provided on the first outer conductor 13a. The metal thin wire braid was made by braiding tin-plated annealed copper wire (metal thin wire) with an outer diameter of 0.05 mm with a number of wires of 4, a number of strokes of 16, and a pitch of 6 mm, and the outer diameter was 0.91 mm. The outer cover 14 was made by extruding PFA to a thickness of 0.05 mm. The outer diameter of the coaxial cable after extrusion was 1.11 mm. In this way, a coaxial cable of Comparative Example 1 was produced.

[Comparative example 2]
In Example 1, the pitch was changed to 14 mm using 38 second outer conductors 13b, and a coaxial cable of Comparative Example 2 was produced.

The structural dimensions of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Table 1.

[Flexibility test]
FIG. 3 is an explanatory diagram showing an aspect of the flexibility test. In the flexibility test, both ends of a 500 mm long coaxial cable 10 are fixed with fixtures 31, and the maximum width W when no weight 32 is attached, and when a 50 g weight 32 is attached to the lowest point of the coaxial cable 10. The maximum width W was measured. It can be said that the smaller the maximum width W is, the more flexible it is. The coaxial cables of Examples 1 to 7 and Comparative Examples 1 and 2 were tested, and the results are shown in Table 2. From the results in Table 2, Examples 1 to 7 were flexible. On the other hand, Comparative Example 1 had a braided structure and had poor flexibility.

[Bending test]
FIG. 4 is an explanatory diagram showing an aspect of a bending test. In the bending test, a coaxial cable 10 with a length of 1000 mm is sandwiched between two rolls 42 and 42 with a diameter of 10 cm, a load 41 is attached to the lower end of the coaxial cable 10, and the cable is swung between the roll 42 and the lower end. It was clamped with stops 43, 43. After this configuration, the coaxial cable 10 above the roll 42 was bent 180° left and right along the arc of the roll 42 at a rate of 20 times/min for 50 minutes.

The attenuation and bending phase of the coaxial cables of Examples 1 to 3 and Comparative Examples 1 and 2 were measured before and after the test. The bending phase was measured by cutting the obtained coaxial cable to a length of 700 mm, attaching a connector, bending the coaxial cable to form a circle with a radius of curvature of 50 mm, and conducting network analysis at a frequency of 26.5 GHz. I got it. For network analysis, a network analyzer (manufactured by KEYSIGHT Co., Ltd.) was used, and the measurement cable and connector that came with the network analyzer were used. In network analysis, changes in the amplitude and phase of a signal can be measured by reflection measurement and transmission measurement when a high frequency sine wave signal is input to the coaxial cable 10. The measurement results of the changed amplitude and phase are calculated inside the network analyzer to obtain coaxial cable characteristics (attenuation, phase). The results are shown in Table 2. The numerical value is the average value of 12 measurement samples at 8 GHz.

10 Coaxial cable 11 Center conductor 12 Insulator 12a Inner annular portion 12b Outer annular portion 12c Connecting portion 13 Outer conductor 13a First outer conductor (metal resin tape)
13b Second outer conductor (thin metal wire)
14 Outer cover 31 Fixture 32 Weight 41 Load 42 Roll 43 Steady rest W Maximum width

Claims (6)

a center conductor, a low dielectric constant insulator provided around the outer periphery of the center conductor, a first outer conductor made of a metal resin tape attached vertically to the outer periphery of the insulator, and a first outer conductor made of a metal resin tape attached vertically to the outer periphery of the insulator; A coaxial cable comprising a second outer conductor made of a plurality of wound thin metal wires and an outer sheath covering the second outer conductor, the second outer conductor having an outer diameter of the insulator. The second outer conductor has a winding pitch of 0.5 to 11 mm, and the outer diameter of the thin metal wire is 0.5 to 11 times the outer diameter of the insulator. 04 to 0.1 times, and a gap formed in the second outer conductor is less than or equal to the outer diameter of the thin metal wire . The coaxial cable according to claim 1 , wherein the outer diameter of the thin metal wire is 0.04 to 0.1 mm . The coaxial cable according to claim 1 or 2 , wherein the first outer conductor has a thickness of 0.004 to 0.036 mm. The width of the metal resin tape is 3.5 to 4.5 times the outer diameter of the insulator, and the metal resin tape is attached vertically so that the metal surface faces outward and both ends partially overlap. The coaxial cable according to any one of items 1 to 3 . The coaxial cable according to claim 1, wherein the insulator is made of a resin having a dielectric constant of 2.0 to 2.5 . The coaxial cable according to any one of claims 1 to 5 , wherein the insulator has a hollow structure or a foam structure.

Images