JP2007188782A - Coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfy the shield characteristics, flexibility, reduced-diameter structure, bending resistance and economical efficiency, and to improve the terminal workability. <P>SOLUTION: This coaxial cable 1 has a structure in which a center conductor 11, an insulator 12, an outer conductor 13 having a spiral shield structure, and an outer sheath 20 are stacked one by one coaxially. When the outer sheath 20 is formed of PFA, the insulator 12 is formed of fluoridated PFA. When the outer sheath 20 is formed of FEP or FTFE, the insulator 12 is formed of any of fluoridated FEP, PFA, and fluoridated PFA. In addition to the above-listed configuration, a metal-deposited or metal-plated tape layer may be provided between the insulator 12 and the outer conductor 13. The coaxial cable 1 is designed so that the spiral winding of the outer conductor 13 is wound at a spiral winding angle of 70 to 85 degrees. The center conductor 11 can be a conductor composed of a plurality of wires of a single wire. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coaxial cable used in information communication devices such as notebook computers and mobile phones, game machines, white goods, in-vehicle devices, and the like.

  With the rapid advancement and expansion of wireless technology, wireless communication is rapidly progressing in information communication devices such as mobile phones and notebook PCs, game machines, white goods, in-vehicle devices, and the like. For example, a notebook PC or the like is provided with wireless communication means for performing wireless LAN, Bluetooth, infrared communication, or the like. For example, an in-vehicle device is provided with wireless communication means for realizing ETC or GPS functions.

  An antenna and its transmission / reception circuit are indispensable for the wireless device as described above. However, the antenna and the transmission / reception circuit are usually arranged at positions separated from each other in the device. For example, in these wireless devices, the display unit is normally configured to be foldable, the transmission / reception circuit is disposed on the mother board of the device, and the antenna is disposed as high as possible in the wireless device. For this reason, the electrical connection between the device main body and the display unit is a wiring structure that involves rotation or twisting.

In general, it is necessary to suppress the occurrence of electromagnetic interference (EMI) between circuits by electromagnetic waves radiated from high-frequency signal lines.
In order to cope with these, coaxial cables applied to wireless devices need characteristics such as high shielding, low attenuation, reduced diameter configuration, high flexibility, and high bending resistance. Naturally, the economics as a coaxial cable is regarded as important after satisfying these functions.

  As a coaxial cable used for the above-mentioned radio equipment, a braided shield structure or a semi-flexible structure is generally used. A coaxial cable having a braided shield structure is configured by providing a dielectric layer on the outer periphery of an inner conductor, providing a metal braid as an outer conductor on the outer periphery of the dielectric layer, and further covering a protective coating layer on the outer periphery.

As the above-described braided shielded coaxial cable, a braided coaxial cable in which the diameter of the metal wire braided structure is reduced to one is known (see, for example, Patent Document 1).
In addition, as a coaxial cable having a semi-flexible structure, there is a structure in which an outer plating layer is formed on the outer periphery of a laterally wound shield (for example, see Patent Document 2) or a structure in which each gap of a braid of an outer conductor is filled with molten metal plating. Are known.

  A semi-rigid coaxial cable in which an insulated wire made of resin coated on the center conductor is inserted into a metal tube such as copper or aluminum, and then uniformly sinked so that there is no gap between the metal tube and the insulated wire Alternatively, a coaxial cable having an outer conductor plating structure in which an insulator, an electroless metal plating layer, an electrolytic metal plating layer, and a protective film are provided coaxially on a conductor in order is known (for example, see Patent Document 3).

  Further, in Patent Document 3, a plurality of micro coaxial cables are bundled, and a control tape made of fluororesin, an outer shield in which a tin-plated annealed copper wire or the like is wound horizontally, and a sheath made of fluororesin are sequentially formed. A coaxial cable is disclosed. Here, the extra fine cable is made of a dielectric made of a fluororesin, an outer shield in which a tin plated annealed copper wire is wound in a horizontal winding, a fluororesin, and the like outside a central conductor made of a tinned hard copper wire or the like. The sheath is arranged in order.

Non-Patent Document 1 discloses a coaxial cable in which the dielectric characteristics of a dielectric used in the coaxial cable are evaluated, and the evaluation result is used to improve the transmission loss of the coaxial cable. Non-Patent Document 1 shows that the dielectric characteristics of materials such as PE, PTFE, and PFA are evaluated, and a cable is prototyped based on these results. As a result, the transmission characteristics of the cable are improved.
JP-A-8-102222 JP 2003-45244 A JP 2000-138013 A JP 2005-149818 A Mitsubishi Electric Industrial Time Report No. 100 (April 2003), pp. 79-83, “Development of low-loss materials for high-frequency coaxial cables”, Nozomi Fujita et al.

  As described above, coaxial cables used for communication devices such as notebook PCs and mobile phones are compatible with high shielding characteristics, low attenuation, reduced diameter configuration due to device miniaturization, and routing in communication devices. High flexibility, high bending resistance due to repeated bending of the device during use, suitability for terminal processing to cope with an automatic peeling machine, and economic efficiency as a coaxial cable are regarded as important.

  With regard to such required characteristics, a transversely wound shield configuration that does not have a semi-flexible structure or a semi-rigid structure is advantageous in terms of diameter reduction, flexibility, bending resistance, and economy. However, the horizontal winding shield configuration has a problem that it is difficult to reduce the attenuation.

For these reasons, a braided shield structure is generally employed that has relatively good shielding characteristics and attenuation, and is advantageous for terminal workability.
However, the braided shield structure as disclosed in Patent Document 1 is disadvantageous in reducing the diameter of the structure, and if the braid is not formed tightly at a predetermined pitch or less, there will be a problem in that the tip is peeled off during stepping. It becomes. If the braid is tightly formed with a small pitch at this time, the coaxial cable becomes stiff and the flexibility and bending resistance are impaired.
That is, the braided shield structure is disadvantageous for reducing the diameter, and if the terminal processability is satisfied, the braided shield structure becomes stiff and has poor flexibility and bending resistance. In addition to this, productivity deteriorates and costs increase.

Further, in the coaxial cable having the semi-flexible structure of Patent Document 2, since the plating is performed in a separate process, the diameter reduction configuration, flexibility, bending resistance, economy, and the like are hindered.
Further, since the above-described semi-rigid coaxial cable uses a metal tube, there is a problem with a reduced diameter configuration, flexibility, bending resistance, and the like, and the cost is very high. Moreover, as in Patent Document 3, the coaxial cable having an outer conductor plating structure is advantageous for reducing the diameter, but this configuration has a problem that it is stiff and easily buckled.

Further, the coaxial cable disclosed in Patent Document 4 has a problem that it is difficult to reduce the amount of attenuation because a common fluororesin is used for the insulator and the jacket and a laterally wound external shield is provided.
In Non-Patent Document 1, there is a description of a coaxial cable using a fluorine-based resin such as PTFE or PFA, but there is no description about the structure of the shield in particular, so that the advantages and disadvantages of the braided shield and the laterally wound shield are compensated. However, it does not disclose a technical idea that satisfies all of the required performance.

  As described above, in the coaxial cable applied to the communication device, it is actually difficult to realize a coaxial cable that can meet all the demands of diversified and sophisticated communication devices.

  The present invention has been made in view of the above-described circumstances, and is a coaxial cable that satisfies shielding characteristics, attenuation, flexibility, reduced diameter configuration, bending resistance, and economy, and has improved terminal processability. It is an object to provide a manufacturing method thereof.

A coaxial cable according to the present invention is a coaxial cable having a structure in which a central conductor, an insulator, a horizontal winding shield layer, and a jacket are sequentially stacked coaxially, the jacket is formed of PFA, and the insulator is fluorinated. It is formed by the made PFA.
A coaxial cable according to the present invention is a coaxial cable having a structure in which a central conductor, an insulator, a horizontal shield layer, and a jacket are sequentially stacked coaxially, and the jacket is formed of FEP or FTFE, Is formed of any one of fluorinated FEP, PFA, and fluorinated PFA.

Furthermore, in addition to the above configuration, another coaxial cable according to the present invention includes a tape layer in which a metal is vapor-deposited or plated between the insulator and the transversely wound shield layer.
In the coaxial cable according to the present invention, the horizontal winding angle of the horizontal shield layer is set to 70 to 85 °. The central conductor may be a multi-line or single-line conductor.

The coaxial cable according to the present invention satisfies the shielding characteristics, attenuation, flexibility, reduced diameter configuration, bending resistance, and economy, and can improve the terminal processability.
In particular, according to the present invention, a metal is evaporated or deposited between the central conductor, the insulator, the horizontal winding shield layer, and the coaxial cable having a structure in which the jacket is sequentially laminated coaxially, or between the insulator and the horizontal winding shield layer. In a coaxial cable having a plated tape layer, a conventional braided shield is formed by forming a transversely wound shield layer on an insulator made of a fluorinated fluororesin, and by combining the insulator with the jacket. Compared with the structure, the electrical characteristics can be improved by about 10%.

Further, at this time, by adopting the horizontal winding shield structure, the diameter can be reduced as compared with the conventional braided shield structure, and the mechanical characteristics can be greatly improved. Furthermore, the cost of the coaxial cable can be reduced.
Moreover, according to this invention, terminal processability is securable by making the horizontal winding angle of a horizontal winding shield layer into 70-85 degrees.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of a coaxial cable according to the present invention, and FIG. 2 is a diagram for explaining a layer structure of the coaxial cable of FIG. 1 and 2, 1 is a coaxial cable, 10 is a coaxial cable strand, 11 is a central conductor, 12 is an insulator, 13 is an external conductor, 13a is a horizontal winding, and 20 is a jacket.

  As the outer conductor 13, a flexible outer conductor (so-called shield) generally used in a thin coaxial cable can be appropriately selected and used. Such an external conductor 13 can be formed by winding a horizontal winding 13a made of a thin conductor wire around the outer periphery of the insulator 12 by horizontal winding. In general, a plurality of small-diameter conductive wires are used for the horizontal winding 13a.

  The jacket 20 is formed by extrusion coating a predetermined resin around the outer conductor 13. The resin material for forming the jacket 20 can be appropriately selected from jacket members generally used for coaxial cables, but a fluororesin can be preferably used. Fluorocarbon resin has the above-mentioned opening / closing function because it is suitable for reducing the diameter of the cable because of its good thin-wall processability, and in addition, its bending resistance is improved because of its low coefficient of dynamic friction. The present invention can be suitably applied to a coaxial cable for electronic equipment.

  Specific examples of the fluororesin used for the jacket include PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), and FEP (tetrafluoroethylene / hexafluoropropylene copolymer). ), ETFE (tetrafluoroethylene / ethylene copolymer), and the like can be used.

  Further, the center conductor 11 is not limited to a configuration in which a plurality of conductors are bundled as shown in FIG.

  The coaxial cable 1 of the present embodiment is characterized by using a fluorinated fluororesin having higher heat resistance than the conventional one for the insulator 12 and using the horizontal winding 13a having the horizontal winding shield structure as the outer conductor 13. It is said. Although the coaxial cable 1 having such a structure is a horizontal winding shield structure, it can realize better shielding characteristics than the conventional configuration. In addition, it is possible to obtain a coaxial cable excellent in narrowing, flexibility, bending resistance (mechanical characteristics), and economy, which are the essential features of the horizontal winding shield structure.

  The coaxial cable according to the present embodiment has a small attenuation amount, and particularly has a characteristic of a small attenuation amount in a high frequency region (2.4 to 6 GHz), and thus is optimal as an antenna line for a wireless device. The thickness of the coaxial cable can be made thinner than AWG (American Wire Gauge) # 30.

The reason why the attenuation is reduced in spite of the horizontal shield structure is that the deterioration of the insulator 12 is suppressed by the high heat-resistant fluorinated fluororesin used as the insulator 12. ing.
The conventional braided structure was considered to have a smaller attenuation than the conventional horizontal shield structure. However, even in the conventional braided structure, the overlapping of the braided wires is formed in the structure, and the contact point is the amount of attenuation. It is thought that it was a factor of deterioration.
However, the configuration of the present embodiment as described above uses a high heat-resistant fluorinated fluororesin as the insulator 12 to insulate the outer cover 20 when the outer cover 20 is formed by extrusion coating. The deterioration of the body 12 is suppressed, and the overlap between the braided wires as in the conventional braided structure is not formed by the laterally wound shield structure, so that the amount of attenuation can be further reduced as compared with the conventional braided structure.

  With the above configuration, even with a horizontally wound shield structure that has conventionally been difficult to reduce the amount of attenuation, the amount of attenuation can be reduced. A coaxial cable that maintains characteristics such as flexibility and economy can be obtained.

As the fluorinated fluororesin, a fluororesin having a terminal group fluorinated (—CF ₃ ) can be used, but a fully fluorinated fluororesin may be applied.

For the above reasons, in the coaxial cable, the resin that can be used for the insulator 12 differs depending on the resin material used for the jacket 20.
For example, when PFA (melting point: 300 to 310 ° C.) is used as the resin material of the jacket 20, fluorinated PFA is used as the material of the insulator 12. When FEP (melting point: 250 to 270 ° C.) or ETFE (melting point: 230 to 250 ° C.) is used as the resin material of the jacket 20, fluorinated FEP or PFA is used as the resin material for the insulator 12. (Which may not be fluorinated) can be used.
That is, as the insulator 12, it is necessary to apply a resin material having a melting point equal to or higher than that of at least the resin material used for the jacket 20.

  In addition, in order to obtain the effect of the horizontal winding shield structure as described above, it is necessary to set the thickness of the insulator 12 within a predetermined range. However, according to the configuration of the present invention, the thickness of AWG # 30 is 300 ± 30 μm. It has been confirmed that the characteristics are good at 230 ± 30 μm thickness for AWG # 32 and 140 ± 20 μm thickness for AWG # 36. This indicates that good characteristics can be obtained with the same thickness structure as that of the conventional insulator 12.

FIG. 3 is a diagram for explaining the horizontal winding angle of the horizontal winding, and shows only one turn of the horizontal winding 13a that is laterally wound with respect to the insulator 12. FIG.
In the coaxial cable according to the present invention, the horizontal winding angle α of the horizontal winding 13a is set in the range of 70 to 85 ° in order to improve the end workability in the horizontal winding shield structure. The horizontal winding angle is expressed as an inclination angle α of the horizontal winding 13a with respect to the height direction of the insulator 12 (a direction perpendicular to the longitudinal central axis of the insulator 12). By setting the horizontal winding angle α to 70 to 85 °, it is possible to prevent a variation in end processing in the coaxial cable having the horizontal shield structure.
In addition, as the horizontal winding 13a, tinned or silver-plated annealed copper wire or alloy wire is generally used. However, in the present invention, the material and dimensions of the horizontal winding are not limited. The winding direction is not limited.

FIG. 4 is a sectional view showing another embodiment of the coaxial cable according to the present invention, in which 14 is a metal-deposited tape layer.
The present embodiment has a configuration in which a metal vapor-deposited tape layer 14 is provided between the insulator 12 and the external conductor 13 in addition to the configuration of FIG. By providing the metal vapor-deposited tape layer 14, it is possible to reduce the attenuation and enhance the shielding effect.

  The metal vapor-deposited tape layer 14 is formed by vapor-depositing metal on the surface of a plastic tape. As the base material of the plastic tape, PET, polyphenylene sulfide, or the like can be suitably used in view of heat resistance and dimensional stability. Further, a highly conductive metal such as silver or copper is used for the vapor deposition metal or the plating metal. Moreover, it replaces with the said metal vapor deposition tape, and the metal plating tape formed by giving metal plating to the surface of a plastic tape can be applied.

  Further, when the metal vapor-deposited tape or the metal plating tape is disposed on the surface of the insulator 12, the tape may be disposed vertically or the tape may be wound around the surface of the insulator 12, It is preferable in terms of characteristics to arrange them as described above.

Examples of the coaxial cable according to the present invention and comparative examples will be described below. FIG. 5 is a diagram for explaining the configuration of an example and a comparative example of a coaxial cable.
As a first embodiment of the coaxial cable according to the present invention, a coaxial cable 1 corresponding to AWG # 36 was created with the configuration shown in FIG. The center conductor 11 was formed by twisting seven silver-plated annealed copper wires having an outer diameter of 0.05 mmφ. At this time, the diameter of the central conductor 11 was 0.15 mmφ. The central conductor 11 was covered with a fluorinated PFA having a thickness of 0.14 mm to form an insulator 12. The outer diameter of the insulator 12 at this time was 0.43 mmφ. Then, a lateral winding 13a made of a tin-plated annealed copper wire having an outer diameter of 0.05 mmφ was wound around the outer peripheral surface of the insulator 12 at a pitch of 7 mm to form an external conductor 13, whereby a coaxial cable strand 10 was obtained. The horizontal winding angle α of the horizontal winding at this time was 78 °.

  Then, the outer jacket 20 was formed by extrusion coating on the coaxial cable strand 10. PFA was used as the material of the outer cover 20, and the surface of the outer conductor 13 was coated in a state where the diameter of the PFA discharged from the crosshead die was pulled down to the target diameter. Here, by coating PFA with a thickness of 0.09 mm, a coaxial cable having an outer diameter of 0.7 mmφ was obtained.

Next, as a comparative example, a coaxial cable having the following configuration corresponding to the AWG # 36 was prepared.
First, the center conductor 11 was formed with the same configuration as in the above example, and the periphery of the center conductor 11 was covered with 0.13 mm thick FEP to form an insulator 12. The outer diameter of the insulator 12 at this time was 0.40 mmφ. Then, an outer conductor 13 having a single braided structure made of a tin-plated annealed copper wire having an outer diameter of 0.05 mmφ was formed on the outer peripheral surface of the insulator 12 to obtain a coaxial cable strand 10. The outer sheath 20 was formed by extrusion coating with respect to the coaxial cable strand 10 with the same configuration as in the above embodiment. As a result, a coaxial cable having an outer diameter of 0.81 mmφ was obtained.

  As a second example, the central conductor 11 was formed by twisting seven silver-plated annealed copper wires having an outer diameter of 0.102 mmφ corresponding to AWG # 30. At this time, the diameter of the central conductor 11 was 0.31 mmφ. The center conductor 11 was covered with fluorinated PFA having a thickness of 0.30 mm to form an insulator 12. The outer diameter of the insulator 12 at this time was 0.90 mmφ. Then, a lateral winding 13a made of a tin-plated annealed copper wire having an outer diameter of 0.10 mmφ was wound around the outer peripheral surface of the insulator 12 at a pitch of 12 mm to form an external conductor 13, whereby a coaxial cable strand 10 was obtained. The horizontal winding angle α of the horizontal winding at this time was 77 °.

  Then, the outer jacket 20 was formed by extrusion coating on the coaxial cable strand 10. PFA was used as the material of the outer cover 20, and the surface of the outer conductor 13 was coated in a state where the diameter of the PFA discharged from the crosshead die was pulled down to the target diameter. Here, a coaxial cable having an outer diameter of 1.35 mmφ was obtained by coating PFA with a thickness of 0.12 mm.

  As described above, the outer diameter of the coaxial cable of Example 1 was 0.70 mmφ, and the outer diameter of the coaxial cable of the comparative example was 0.81 mmφ. In other words, the diameter can be reduced by adopting a horizontal winding shield structure.

FIG. 6 is a diagram showing the electrical characteristics of the coaxial cables of the above-described examples and comparative examples. FIG. 7 is a graph showing the relationship between the frequency and the amount of attenuation in Example 1 and the comparative example, and FIG. 8 is a graph showing the relationship between the frequency and the amount of attenuation in Example 2.
Comparing Example 1 and the comparative example, as shown in FIG. 6, the attenuation at a frequency of 2.4 GHz is 4.1 (dB / m) in Example 1, and 4.5 (dB / m) in the comparative example. m). The attenuation at a frequency of 6.0 GHz was 6.8 (dB / m) in Example 1 and 7.9 (dB / m) in the comparative example.
As is apparent from FIG. 7, the attenuation amount of Example 1 is better than that of the comparative example over the entire frequency range (0 to 6 GHz).

  The attenuation in Example 2 was 2.0 (dB / m) at a frequency of 2.4 GHz and 3.5 (dB / m) at a frequency of 6.0 GHz. The attenuation amount of the conventional product in AWG # 30 is, for example, 3.9 dB / m at a frequency of 6 GHz, and it was confirmed that the attenuation amount is good also in this example.

Next, the result of the bending test in Example 1 and the comparative example of the coaxial cable will be described.
FIG. 9 is a diagram showing the bending test results of Example 1 and the comparative example, and FIG. 10 is a diagram showing an outline of a test apparatus for performing the bending test.
The apparatus shown in FIG. 10 is used for the bending test. The conditions are: load 1.0 (N), mandrel 30 diameter 10 mmφ (bending radius 5 mmφ), bending angle 90 °, bending speed 30 (times / minute). did.
As shown in FIG. 9, in Example 1 described above, 200,000 times of bending are all passed. On the other hand, in the comparative example, the disconnection was reached after about 37,000 to 47,000 times.

FIG. 11 is a diagram showing the electrical characteristics before and after the bending test of Example 1, and shows the electrical characteristics before the bending test and the electrical characteristics after bending 200,000 times.
As shown in FIG. 11, the electrical characteristics after the bending test in Example 1 were a decrease in the range of about 0.1 dB / km in the frequency region of 3 GHz or more, and there was almost no change before and after the bending test, and there was no problem. .
From the above results, it was possible to obtain a coaxial cable with good bending characteristics by adopting the configuration of Example 1.

  Further, when the terminal processing was performed using the coaxial cables obtained in Examples 1 and 2, the horizontal winding 13a was free from variations and good processing characteristics were obtained. Therefore, it was possible to maintain good terminal processing characteristics by configuring the horizontal winding shield structure at the horizontal winding angle of this example.

1 is a cross-sectional view of an embodiment of a coaxial cable according to the present invention. It is a figure for demonstrating the layer structure of the coaxial cable of FIG. It is a figure for demonstrating the horizontal winding angle of a horizontal winding. It is sectional drawing which shows other embodiment of the coaxial cable by this invention. It is a figure for demonstrating the structure of the Example and comparative example of a coaxial cable in connection with this invention. It is a figure which shows the electrical property of the coaxial cable of an Example and a comparative example. It is a graph which shows the relationship between the frequency of Example 1 and a comparative example, and attenuation amount. It is a graph which shows the relationship between the frequency of Example 2, and attenuation amount. It is a figure which shows the bending test result of Example 1 and a comparative example. It is a figure which shows the outline of the test apparatus which performs a bending test. It is a figure which shows the electrical property before and behind the bending test of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Coaxial cable, 10 ... Coaxial cable strand, 11 ... Center conductor, 12 ... Insulator, 13 ... Outer conductor, 13a ... Horizontal winding, 14 ... Metal vapor deposition tape layer, 20 ... Outer jacket, 30 ... Mandrel

Claims (5)

  A coaxial cable having a structure in which a central conductor, an insulator, a horizontally wound shield layer, and a jacket are sequentially stacked coaxially, wherein the jacket is formed of PFA, and the insulator is formed of fluorinated PFA Coaxial cable characterized by being made.   A coaxial cable having a structure in which a central conductor, an insulator, a horizontally wound shield layer, and a jacket are sequentially stacked coaxially, wherein the jacket is formed of FEP or FTFE, and the insulator is a fluorinated FEP A coaxial cable formed of any one of PFA, PFA, and fluorinated PFA.   The coaxial cable according to claim 1, further comprising a tape layer on which a metal is deposited or plated between the insulator and the horizontal shield layer.   The coaxial cable according to claim 1, wherein a horizontal winding angle of the horizontal winding shield layer is 70 to 85 °.   The coaxial cable according to any one of claims 1 to 4, wherein the central conductor is formed of a multi-line or single-line conductor.

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