Patent Application
20250191811
The present invention relates to a coaxial cable and more specifically to a coaxial cable used in in-device antenna wiring and semiconductor devices compatible with the fifth generation communication standard (5G), and having excellent shieldability and processability of an external conductor.
Coaxial cables are utilized for transmission of high-frequency signals because of their excellent shieldability against noise and the like. In particular, coaxial cables used in in-device antenna wiring and semiconductor devices require a smaller diameter and favorable bending characteristics along with excellent shieldability. In response to such requirements, Patent Document 1, for example, proposes a coaxial cable that satisfies shieldability, flexibility, a smaller 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 external conductor having a lateral winding shield structure, and an outer coating are coaxially laminated sequentially.
In recent years, coaxial cables have been used to transmit high-frequency signals in electronic devices that are being increasingly miniaturized, such as personal computers, smartphones, and tablet terminals. In particular, coaxial cables used in in-device antenna wiring and semiconductor devices compatible with the fifth generation communication standard (5G) require a higher shielding effect due to leakage current being amplified by the in-device antennas.
In the process of studying coaxial cables to improve the shielding effect, the present inventors fabricated and studied the following types of external conductors: (1) an external conductor having a double structure provided with a fine wire lateral winding shield and polyethylene terephthalate (PET) tape provided with a copper layer having a thickness of 6 μm, for example, on one side, in this order; (2) an external conductor having a triple structure provided with a fine wire lateral winding shield, PET tape provided with a copper layer having a thickness of 6 μm, for example, on one side, and PET tape provided with a copper layer having a thickness of 6 μm, for example, on the other side, in this order; and (3) an external conductor having a double structure provided with a fine wire lateral winding shield and copper foil tape having a thickness of 15 μm, for example, in this order.
However, the coaxial cable including the external conductor of (1) described above did not have a sufficient shielding effect due to the copper layer having a thin thickness. Further, the coaxial cable including the external conductor of (2) described above was wound with two layers of PET tape, each provided with a copper layer having a thickness of 6 μm on one side, as the external conductor, resulting in the PET tape insulating the respective copper layers on the inner side and the outer side, and thus, to ensure that the total 12-μm copper layer functioned to improve shieldability, the copper layer positioned on the outer side had to be further grounded, making the processability complex. The coaxial cable including the external conductor of (3) described above had the drawback that the copper foil tape was hard, difficult to wind, and easy to break.
The present invention has been made to resolve the above-described problems, and an object thereof is to provide a coaxial cable used in in-device antenna wiring and semiconductor devices compatible with the fifth generation communication standard (5G), and having excellent shieldability and processability of an external conductor.
A coaxial cable according to the present invention comprises a center conductor, an insulator provided on an outer periphery of the center conductor, an external conductor provided on an outer periphery of the insulator, and an outer coated body covering the external conductor. The external conductor is constituted by a lateral winding shield provided with metal fine wires laterally wound on the outer periphery of the insulator, and a metal layer double-sided resin tape, with metal layers disposed on both sides, wound on the lateral winding shield.
According to this invention, the coaxial cable includes the metal layer double-sided resin tape with metal layers disposed on both sides, and thus, with the metal layer double-sided resin tape being wound, the metal layers on both sides conduct electricity. This makes it possible to ensure a metal amount sufficient for enhancing shieldability, and does not require further grounding of the metal layer positioned on the outer side, as in the case of a resin tape including a metal layer on one side being wound in layers, resulting in excellent processability. Further, the metal layers are provided on both sides, making it possible to make a thickness of the layer on each side thinner, and thus avoid disconnection and winding difficulty such as with copper foil tape. Such a coaxial cable can constitute a coaxial cable having excellent shieldability and favorable processability, such as ground connection processing and tape windability, and is preferred for use in in-device antenna wiring and semiconductor devices compatible with the fifth generation communication standard (5G).
In the coaxial cable according to the present invention, preferably a thickness of each of the metal layers provided on both sides of the metal layer double-sided resin tape is 6 μm or more and 12 μm or less. According to this invention, the thickness of each metal layer is within the above-described range and thus, with the metal layer double-sided resin tape being wound, the conducting metal layers on both sides can ensure a metal amount sufficient for enhancing shieldability. Further, the metal layers are provided on both sides, making it possible to make a thickness of the layer on each side thinner, and thus avoid disconnection and winding difficulty such as with copper foil tape.
In the coaxial cable according to the present invention, preferably a thickness of the metal layer double-sided resin tape is 8 μm or more and 24 μm or less. According to this invention, the thickness of the metal layer double-sided resin tape is within the above-described range, making it possible to meet the demand for a smaller diameter of a coaxial cable.
In the coaxial cable according to the present invention, preferably a metal layer single-sided resin tape is provided by being laterally wound between the metal layer double-sided resin tape and the resin tape. According to this invention, it is possible to further increase a total quantity of the metal layers of the metal layer double-sided resin tape while keeping the thickness of each metal layer within a range that does not result in a reduction in flexibility, and further enhance the shieldability while maintaining productivity.
In the coaxial cable according to the present invention, preferably the outer coated body is constituted by a resin tape wound on the external conductor and an extruded sheath covering the resin tape.
In the coaxial cable according to the present invention, preferably an adhesive layer is provided on one surface of the resin tape and winding is performed so that the adhesive layer is on an inner side. According to this invention, the adhesive layer of the resin tape fixes the metal layer double-sided resin tape and the metal layer single-sided resin tape so that there is no position shift and thus, even if stress is applied during the wiring of the coaxial cable, a position shift does not occur in the lateral winding shield. As a result, it is possible to suppress a reduction in the shielding effect.
According to the present invention, it is possible to provide a coaxial cable used in in-device antenna wiring and semiconductor devices compatible with the fifth generation communication standard (5G), and having excellent shieldability and processability of an external conductor. In particular, the coaxial cable includes the metal layer double-sided resin tape with the metal layers disposed on both sides and, with the metal layer double-sided resin tape being wound, the metal layers on both sides conduct electricity. This makes it possible to ensure a metal amount sufficient for enhancing shieldability, and does not require further grounding of the metal layer positioned on the outer side, as in the case of a resin tape including a metal layer on one side being wound in layers, resulting in excellent processability. Further, the metal layers are provided on both sides, making it possible to make a thickness of the layer on each side thinner, and thus avoid disconnection and winding difficulty such as with copper foil tape.
Embodiments of a coaxial cable according to the present invention will now be described with reference to the drawings. It should be noted that the present invention includes aspects of the same technical concept as that of the forms set forth in the embodiments and the drawings described below, and the technical scope of the present invention is not limited only to the description of the embodiments and the description of the drawings.
A coaxial cable 10 according to the present invention, as illustrated in
This coaxial cable 10 includes the metal layer double-sided resin tape 14 with the metal layers 14a, 14b disposed on both sides and thus, with the metal layer double-sided resin tape 14 being wound, the metal layers 14a, 14b on both sides conduct electricity. This makes it possible to ensure a metal amount sufficient for enhancing shieldability, and does not require further grounding of the metal layer positioned on the outer side, as in the case of a resin tape including a metal layer on one side being wound in layers, resulting in excellent processability. Further, the metal layers 14a, 14b are provided on both sides, making it possible to make a thickness of the layer on each side thinner, and thus avoid disconnection and winding difficulty such as with copper foil tape.
In the following, each component will be described in detail.
The coaxial cable 10, as illustrated in
The center conductor 11 is constituted by a single strand extending in a longitudinal direction of the coaxial cable 10, or is constituted by a plurality of strands twisted together. The type of strand is not particularly limited as long as composed of a metal having favorable conductivity, but preferable examples include a metal conductor having favorable conductivity, such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, copper-aluminum composite wire, or any of these with a plating layer on a surface thereof. Copper wire and copper alloy wire are particularly preferred from the standpoint of high frequency use. As the plating layer, a solder plating layer, a tin plating layer, a gold plating layer, a silver plating layer, a nickel plating layer, or the like is preferred. A cross-sectional shape of the strand is also not particularly limited and, in the wire material thereof, may be circular or substantially circular or may be rectangular.
A cross-sectional shape of the center conductor 11 is also not particularly limited. The shape may be circular (including oval) or may be rectangular or the like, but is preferably circular. An outer diameter of the center conductor 11 is desirably as large as possible so that an electric resistance (alternating-current resistance, conductor resistance) is reduced and, to reduce a final outer diameter of the coaxial cable 10, examples thereof include an outer diameter within a range of about 0.09 to 1 mm. A surface of the center conductor 11 may be provided with an insulating film (not illustrated), as necessary. A type and a thickness of the insulating film are not particularly limited, but a film that breaks down well during soldering, for example, is preferred, and preferable examples thereof include a thermosetting polyurethane film or the like.
The insulator 12, as illustrated in
The insulator 12 may be a solid structure illustrated in
The external conductor (13, 14), as illustrated in
Further, as illustrated in
The lateral winding shield 13 is formed by laterally winding metal fine wires on the insulator 12, as illustrated in
The metal fine wire is not particularly limited as long as the wire has favorable conductivity and can be provided on the outer periphery of the insulator 12 as the lateral winding shield 13 that constitutes the coaxial cable 10. For example, various types of metal fine wires represented by tin-plated copper wires and the like can be preferably used. An outer diameter of the metal fine wire is not particularly limited and is determined in relation to an outer diameter of the insulator 12, but examples thereof include an outer diameter within a range of about 0.04 to 0.1 mm. The quantity of metal fine wires is also selected as desired depending on the outer diameter of the insulator 12, a planned outer diameter of the coaxial cable 10, and the like. A lateral winding pitch during the laterally winding of the metal fine wires is also not particularly limited, but is normally preferably about 0.5 to 11 mm.
The metal layer double-sided resin tape 14 is provided by being laterally wound (spirally wound) on the lateral winding shield 13, as illustrated in
The metal layer double-sided resin tape 14 is wound on the lateral winding shield 13, and thus the metal layers 14a, 14b on both sides conduct electricity. This makes it possible to ensure a metal amount sufficient for enhancing shieldability, and does not require processing in which the metal layer positioned on the outer side is further grounded, as in the case of a resin tape including a metal layer on one side being wound in layers, resulting in excellent processability. Further, the metal layers 14a, 14b are provided on both sides, making it possible to make the thickness of the layer on each side thinner, and thus avoid disconnection and winding difficulty such as with copper foil tape. Such a metal layer double-sided resin tape 14 is provided, making it possible to realize the coaxial cable 10 having excellent shieldability and favorable processability, such as ground connection processing and tape windability.
The resin base material 14c is not particularly limited, but a polyester film such as polyethylene terephthalate and polyethylene naphthalate can be preferably used. A thickness of the resin base material 14c is selected as desired from those within a range of about 2 to 16 μm, for example, which are readily available.
Preferable examples of the metal layers 14a, 14b include a copper layer, an aluminum layer, or the like. Preferable examples of the metal layers 14a, 14b include a film formed on the resin base material 14c by vapor deposition or plating, metal foil bonded via an adhesive layer (for example, polyester-based thermoplastic adhesive resin, or the like) provided as necessary, or the like.
With the metal layer double-sided resin tape 14 being wound, the metal layers 14a, 14b on both sides conduct electricity, and thus thicknesses of the metal layers 14a, 14b are preferably thicknesses that can ensure a metal amount sufficient for making the shieldability favorable. The thickness of each of the metal layers 14a, 14b capable of ensuring the metal amount is preferably within a range of 6 μm or more and 12 μm or less. Within the thickness range described above, the metal layers 14a, 14b having the same thickness may be provided or the metal layers 14a, 14b having different thicknesses may be provided on both sides. When the thickness of each of the metal layers 14a, 14b is less than 6 μm, a total thickness is less than 12 μm and the metal amount is also insufficient, resulting in insufficient shieldability. When the thickness of each of the metal layers 14a, 14b exceeds 12 μm and the total thickness exceeds 24 μm, a rigidity of each metal layer increases, making winding difficult. With the standpoint of ease of winding taken into further consideration, the thickness of each of the metal layers 14a, 14b is more preferably within a range of 6 μm or more and 10 μm or less. It should be noted that, as the thickness of the metal layer increases, the rigidity increases and the ease of winding decreases, but this ease of winding depends on an outer diameter of the lateral winding shield 13 to be wound. In a case in which the thickness of each of the metal layers 14a, 14b is 12 μm, maximum, and the total thickness is 24 μm, maximum, as long as the outer diameter after the lateral winding shield 13 is wound is about 0.7 mm to about 2.1 mm as in the example described below, winding can be performed without reducing the ease of winding.
An overall thickness of the metal layer double-sided resin tape 14, which is a total thickness of the resin base material 14c and the metal layers 14a, 14b, is preferably, as a thickness that can contribute to making the diameter of the coaxial cable 10 smaller, within a range of about 14 to 26 μm.
The metal layer double-sided resin tape 14 is wound in layers within a range of ¼ wrap to ½ wrap. With the wrap set within this range, it is possible to ensure direct contact between the metal layers 14a, 14b constituting the metal layer double-sided resin tape 14 and the lateral winding shield 13, and realize a stable shielding effect. Furthermore, by being laterally wound on the basis of the above-described wrap, the metal layers of the metal layer double-sided resin tape 14 can be directly disposed on the metal fine wires without producing gaps between the metal layers. When the wrap is less than ¼, the overlap is small and thus a shift in position may occur during lateral winding, and when the wrap exceeds ½, an overlap thickness of the metal layer double-sided resin tape 14 increases, which may be disadvantageous in terms of achieving a smaller diameter. It should be noted that a winding pitch of the metal layer double-sided resin tape 14 is set as desired by a width and the wrap of the metal layer double-sided resin tape 14 and thus is not particularly limited, but in a case in which the width of the metal layer double-sided resin tape 14 is within a range of about 3 to 6 mm, for example, the winding pitch is preferably within a range of 1.5 to 10 mm, for example. A lateral winding direction of the metal layer double-sided resin tape 14 may be the same as a lateral winding direction of the metal fine wires described above or may be a winding direction opposite thereto, but the direction opposite thereto is preferred.
It should be noted that, with the metal layer double-sided resin tape 14 provided with the metal layers 14a, 14b on both sides, even in a case in which a gap temporarily occurs in the lateral winding shield 13, the fine wires of the lateral winding shield 13 and the metal layer of the metal layer double-sided resin tape 14 come into direct contact, making it possible to suppress a reduction in the shielding effect.
The metal layer single-sided resin tape 14′ may be further provided by being laterally wound (spirally wound) on the metal layer double-sided resin tape 14, as illustrated in
The resin base material and the metal layer constituting the metal layer single-sided resin tape 14′ are preferably constituted by the same materials and within thickness ranges as those of the resin base material and metal layers constituting the metal layer double-sided resin tape 14 described above. Here, the descriptions thereof will be omitted. The thickness of the metal layer is not particularly limited, but from the standpoint of being able to further ensure the metal amount of the external conductor as a whole, is preferably within a range of 3 μm or more and 12 μm or less, and is more preferably within a range of 3 μm or more and 6 μm or less. It should be noted that a total thickness of the metal layer single-sided resin tape 14′ differs depending on a thickness of the resin base material as well, but is preferably within a range of 5 μm or more and 18 μm or less. Such an external conductor having a triple structure including the metal layer single-sided resin tape 14′ can further increase the total of the metal amount and enhance shieldability.
Further, when the thickness of each of the metal layers (14a, 14b) of the metal layer double-sided resin tape 14 described above is set to a thickness exceeding 12 μm, for example, to increase the metal amount, the rigidity of each metal layer increases and flexibility decreases, making winding difficult and reducing productivity. To solve this problem, the metal layer single-sided resin tape 14′ is provided on the metal layer double-sided resin tape 14, making it possible to further increase the total quantity of the metal layers while keeping the thickness of each metal layer (14a, 14b) of the metal layer double-sided resin tape 14 described above within the range (6 to 12 μm) previously described that does not result in a reduction in flexibility, and further enhance the shieldability while maintaining productivity. With the metal layer single-sided resin tape 14′ being provided on the metal layer double-sided resin tape 14, the overall total thickness of the metal layers of each tape is increased, making it possible to further enhance the shieldability while maintaining ease of winding. The overall total thickness is preferably 15 μm or greater than the sum of the lower limit values of the respective metal layers.
It should be noted that the metal layer single-sided resin tape 14′ is preferably wound in layers within the same wrap range as that of the metal layer double-sided resin tape 14 described above, and exhibits the same effects as described above. A lateral winding direction of the metal layer single-sided resin tape 14′ may be the same winding direction as the lateral winding direction of the metal layer double-sided resin tape 14 or may be a winding direction opposite thereto, but the direction opposite thereto is preferred.
The outer coated body 15, as illustrated in
The resin tape 15a is provided by being laterally wound (spirally wound) on the metal layer double-sided resin tape 14 illustrated in
The resin tape 15a, similar to the above-described metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′, is wound in layers within a range of ¼ wrap to ½ wrap. With the wrap set within this range, the adhesive layer constituting the resin tape 15a can fix the resin tape 15a itself, and adhere to the metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′ to fix the metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′. When the wrap is less than ¼, the overlap is small and thus a shift in position may occur during lateral winding, and when the wrap exceeds ½, an overlap thickness of the resin tape 15a increases, which may be disadvantageous in terms of achieving a smaller diameter. It should be noted that a winding pitch of the resin tape 15a is set as desired by a width and the wrap of the resin tape 15a, but in a case in which the width of the resin tape 15a is within a range of about 3 to 6 mm, for example, the winding pitch is preferably within a range of 1.5 to 10 mm, for example. A lateral winding direction of the resin tape 15a may be the same winding direction as the lateral winding direction of the metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′ described above or may be a winding direction opposite thereto, but the winding direction opposite thereto is preferred.
The resin base material constituting the resin tape 15a is not particularly limited, and examples include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide (PA), polyimide (PI), polyphenylene sulfide (PPS), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), fluorinated resin copolymer (perfluoroalkoxy fluororesin: PFA), polyether ether ketone (PEEK), and the like. In particular, a polyester film such as polyethylene terephthalate and polyethylene naphthalate can be preferably used. A thickness of the resin base material is selected as desired from those within a range of about 2 to 6 mm, for example.
The adhesive layer desirably constituting the resin tape 15a is provided on one side of the resin base material, and examples of a material thereof include a urethane adhesive, an epoxy adhesive, an acrylic adhesive, and the like. A thickness of the adhesive layer is also not particularly limited, but may be about 1 to 3 μm.
For this resin tape 15a, given T2 as a thickness of the resin tape 15a and T1 as the thickness of the metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′, T2/T1 is preferably within a range of ⅙ (=0.167) or more and ⅘ (=0.8) or less, and T2/T1 is more preferably within a range of ¼ (=0.25) or more and ⅗ (=0.600) or less. This way, it is possible to reduce a size of a step (approximately 7 μm or less) that occurs due to the thickness of the resin tape 15a compared with a case in which the metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′ is used alone. Therefore, appearance irregularities caused by air existing in these steps can be suppressed. As a result, it is possible to suppress changes in outer diameter in the longitudinal direction and process terminals under the same conditions when connecting the terminals to connectors.
It should be noted that the present air expands with heat during subsequent extrusion molding of the extruded sheath 15b, resulting in a problem of the occurrence of unevenness and deterioration in appearance. Therefore, extrusion molding is performed while suctioning with a vacuum pump so that as little air as possible remains, but this has not been a sufficient solution. Such appearance irregularities change the outer diameter of the coaxial cable in a longitudinal direction and, when the terminals are connected to connectors under the same terminal processing conditions, the processing yield deteriorates, and thus the terminal processing conditions must be changed each time. In response to such problems, in the coaxial cable 10 obtained with T2/T1 set within the above-described range, appearance irregularities are suppressed, making it possible to suppress changes in outer diameter in the longitudinal direction and process the terminals under the same conditions when connecting the terminals to the connectors. Further, it is possible to realize a smaller diameter compared with a case of a braided shield alone and, even in a case in which gaps temporarily occur in the lateral winding shield, suppress a reduction in the shielding effect. As a result, it is possible to realize a smaller diameter that enables in-device wiring in a narrow space, which is particularly preferred for use in in-device antenna wiring and semiconductor devices compatible with the fifth generation communication standard (5G).
In a case in which T2/T1 is preferably greater than ⅘, more preferably greater than ⅗, a step occurs in the resin tape 15a as well, and thus a sufficient improvement effect may not be obtained. In a case in which T2/T1 is preferably less than ⅙, more preferably less than ¼, the resin tape 15a is too thin, and an extent of the step in the metal layer double-sided resin tape 14 or the metal layer single-sided resin tape 14′ may remain as is, and thus a sufficient improvement effect may not be obtained. A size of the step that affects the appearance differs depending on the overall outer diameter as well, but in a case in which a step of 10 μm or greater occurs, for example, the appearance becomes noticeably uneven, and thus a step of less than 10 μm is preferably the limit. It should be noted that the thickness T2 of the resin tape 15a preferably satisfies the relationship “T2/T1=⅙ to ⅘,” more preferably satisfies the relationship “T2/T1=¼ to ¾,” and preferably is specifically a thickness of 4 μm or more and less than 10 μm, more specifically 4 μm or more and 9 μm or less.
The extruded sheath 15b is provided by extrusion molding on the resin tape 15a. As the constituent resin of the extruded sheath 15b, various resins applied to resin extrusion for outer coated bodies can be used. For example, the resin may be a fluorine-based resin such as PFA, ETFE, or FEP, may be a vinyl chloride resin, may be a polyolefin resin such as polyethylene, or may be a polyester resin such as polyethylene terephthalate. In the coaxial cable 10 according to the present invention, a fluororesin is preferred.
In a case in which the extruded sheath 15b is provided, preferably extrusion molding is performed while suctioning with a vacuum pump so that as little air as possible remains between the extruded sheath 15b and the resin tape 15a. A total thickness of the outer coated body 15 constituted by this extruded sheath 15b and the above-described resin tape 15a may be within a range of about 0.1 to 1.0 mm, for example.
The final outer diameter of the coaxial cable 10 obtained is preferably within a range of about 0.6 to 3.5 mm.
In the following, the present invention will be more specifically described through examples. It should be noted that the present invention is not limited to the examples below.
First, the coaxial cable 10 having a form illustrated in
Next, the resin tape 15a having a total thickness of 4 μm and a width of 3 mm and provided with an adhesive layer having a thickness of 1 μm on one side thereof, was wound on the metal layer double-sided resin tape 14, with the adhesive layer side being on the inner side (side of the metal layer double-sided resin tape 14). The winding form was ⅓ wrap (overlapping by a width of 1 mm only), and the resin tape 15a was wound in the direction opposite to the winding direction of the metal layer double-sided resin tape 14. Heating was performed during the winding process, and the adhesive layer and the metal layer double-sided resin tape 14 were adhered. Subsequently, as the extruded sheath 15b, a PFA resin (manufactured by DuPont) layer was extruded and formed to a thickness of 50 μm while suctioning with a vacuum pump, and the coaxial cable 10 having an outer diameter of 0.879 mm was fabricated. In this coaxial cable 10, the thickness T2 of the resin tape 15a and the thickness T1 of the metal layer double-sided resin tape 14 had a relationship such that T2/T1 was 4/14.5=0.276.
In Example 1, as the metal layer double-sided resin tape 14, a tape having a total thickness of 22.5 μm and a width of 3 mm and provided with a copper foil having a thickness of 10 μm on both surfaces of a PET base material having a thickness of 2.5 μm, was used. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.903 mm was fabricated. In this coaxial cable 10, the thickness T2 of the resin tape 15a and the thickness T1 of the metal layer double-sided resin tape 14 had a relationship such that T2/T1 was 4/22.5=0.178.
In Example 1, as the resin tape 15a, the resin tape 15a having a total thickness of 8 μm and a width of 3 mm and provided with an adhesive layer having a thickness of 1 μm on one side thereof, was used. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.891 mm was fabricated. In this coaxial cable 10, the thickness T2 of the resin tape 15a and the thickness T1 of the metal layer double-sided resin tape 14 had a relationship such that T2/T1 was 8/14.5=0.552.
In Example 1, as the metal layer double-sided resin tape 14, a tape having a total thickness of 18.5 μm and a width of 3 mm and provided with a copper foil having a thickness of 6 μm on one surface and a copper foil having a thickness of 10 μm on the other surface of a PET base material having a thickness of 2.5 μm, was used. This metal layer double-sided resin tape 14 was wound in the direction opposite to the winding direction of the lateral winding shield 13 by the same wrap as in Example 1 so that the metal layer having a thickness of 6 μm was on the side of the lateral winding shield 13. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.903 mm was fabricated.
In Example 1, the metal layer single-sided resin tape 14′ was provided by being laterally wound between the metal layer double-sided resin tape 14 and the resin tape 15a. The metal layer single-sided resin tape 14′ used was a tape having a total thickness of 16 μm and a width of 3 mm and provided with a copper foil having a thickness of 12 μm on one surface of a PET base material having a thickness of 4 μm. This metal layer single-sided resin tape 14′ was wound in the direction opposite to the winding direction of the metal layer double-sided resin tape 14 by ⅓ wrap (overlapping by a width of 1 mm only) on the metal layer double-sided resin tape 14 so that the metal layer was on the metal layer double-sided resin tape 14 side. On the metal layer single-sided resin tape 14′, the resin tape 15a was wound in a direction opposite to the winding direction of the metal layer single-sided resin tape 14′. As the resin tape 15a, a tape having a total thickness of 9 μm and a width of 3 mm and provided with an adhesive layer having a thickness of 1 μm on one side thereof, was used. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.903 mm was fabricated.
In Example 1, instead of the metal layer double-sided resin tape 14, a metal layer single-sided resin tape having a total thickness of 10.5 μm and a width of 3 mm and provided with a copper foil having a thickness of 8 μm on one surface of a PET base material having a thickness of 2.5 μm, was used and wound so that the copper foil was on the lateral winding shield 13 side. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.867 mm was fabricated.
In Example 1, instead of the metal layer double-sided resin tape 14, a metal layer single-sided resin tape having a total thickness of 13 μm and a width of 3 mm and provided with a copper foil having a thickness of 10.5 μm on the one surface of a PET base material having a thickness of 2.5 μm, was used and wound so that the copper foil was on the lateral winding shield 13 side. Subsequently, the same metal layer single-sided resin tape as described above was wound on the metal layer single-sided resin tape already wound in a direction opposite to that winding direction, with an orientation of the metal layer being the same. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.874 mm was fabricated.
In Example 1, instead of the metal layer double-sided resin tape 14, a copper foil tape having a thickness of 15 μm and a width of 3 mm was used and wound on the lateral winding shield 13. With all other conditions being the same as in Example 1, the coaxial cable 10 having an outer diameter of 0.904 mm was fabricated.
Shieldability was evaluated by shielding effect measurements based on a measurement method in accordance with MIL-C-85485A. As for the quality determination by that measurement method, shieldability was identified as favorable in a case in which the evaluation result was 70 dB or higher, and as insufficient in a case in which the evaluation result was less than 70 dB. The results for the coaxial cables in Examples 1 to 5 were 72.4, 77.2, 73.8, 76.5, and 75.4, respectively, indicating favorable shieldability. On the other hand, the results for the coaxial cables in Reference Examples 1 to 3 were 62.2, 60.5, and 68.5, respectively, indicating insufficient shieldability.
The reason that the evaluation results of Examples 1 to 5 were favorable is that, with the metal layer double-sided resin tape 14 or the metal layer double-sided resin tape 14 and the metal layer single-sided resin tape 14′ being wound, the metal layers 14a, 14b on both sides conduct electricity, making it possible to ensure a metal amount (total thickness within the range of 12 to 24 μm) sufficient for enhancing the shieldability. In Example 5, the metal layer single-sided resin tape 14′ provided with the copper foil having a thickness of 12 μm was further wound while keeping the thickness of each metal layer (14a, 14b) of the metal layer double-sided resin tape 14 within a thickness range (6 to 12 μm) that did not result in a reduction in flexibility, making it possible to further increase the total quantity of the metal layers without a loss in the flexibility required for tape winding and further enhance the shieldability while maintaining productivity. The reason that the evaluation result of Reference Example 1 was insufficient is that, although the metal layer single-sided resin tape was wound, the thickness of one side was only 8 μm, which could not ensure a metal amount sufficient for enhancing shieldability. The reason that the evaluation result of Reference Example 2 was insufficient is that, although the metal layer single-sided resin tape was wound in two layers, the metal layer constituting each of the metal layer single-sided resin tapes did not conduct electricity, and thus the thickness of one side was only 10.5 μm, which could not ensure a metal amount sufficient for enhancing shieldability. It should be noted that, in Reference Example 3, a copper foil tape having a thickness of 15 μm was used, which exhibited favorable shieldability, but the thickness exceeded 12 μm, making tape windability unfavorable and cracking and disconnection easy to occur.
Processability was evaluated by the ease of the processing of grounding from the external conductor. In the coaxial cables of Examples 1 to 5, a metal layer double-sided resin tape 14 with the metal layers 14a, 14b on both sides conducting electricity was laterally wound on the lateral winding shield 13, and thus the lateral winding shield 13 and the metal layers 14a, 14b conducted electricity. Therefore, it was not necessary to further ground the metal layer positioned on the outer side, as in the case in Reference Example 2 in which the resin tape including the metal layer on one side was wound in layers, and thus grounding needed only to be performed once, making the processing easy. On the other hand, in the coaxial cable in Reference Example 2, the resin tape including the metal layer on one side was wound in layers, further requiring the grounding of the metal layer positioned on the outer side, making the processing difficult. It should be noted that, in Reference Example 1, the metal layer single-sided resin tape was laterally wound on the lateral winding shield 13 and, in Reference Example 3, the copper foil tape was laterally wound on the lateral winding shield 13, and thus grounding needed only to be performed once in both cases, making the processing easy.
The steps and the appearances were visually evaluated. The steps were all less than 10 μm in Examples 1 to 5. The final appearance of the coaxial cable after being provided with the extruded sheath 16 fluctuated slightly in Examples 1 to 5, but the terminals could also be processed under the same conditions. In this way, it was visually confirmed that, with the step made smaller, an air layer was reduced, the appearance was improved, and waviness (outer diameter fluctuation) in the longitudinal direction was reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-164404 | Oct 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/039939 | 10/29/2021 | WO |
