JP2009032685A - High-speed differential transmission cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat high-speed differential transmission cable comprising a plurality of signal line pairs reduced in loss without increasing the thickness of a conductor of a cable. <P>SOLUTION: The high-speed differential transmission cable is composed by forming each signal line pair S (Sp, Sn) carrying out differential transmission by using two electric conductors 11 as a set, arranging the plurality of signal line pairs in a flat shape, and covering them by extruding an insulation resin. The high-speed differential transmission cable is structured such that the plurality of electric conductors 11 formed of a single core or a stranded wire are arranged in a line in parallel to one another at predetermined intervals P and integrally covered with an insulator 12 formed of the insulation rein, and the outer periphery of the insulator 12 is covered by longitudinally lapping a metal foil tape 13. The high-speed differential transmission cable may be structured to cover the outer periphery of the insulator 12 with a coating formed of the insulation resin. Ground wires G are arranged between the signal line pairs S. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flat high-speed differential transmission cable used for transmitting digital data and the like at high speed.

  When digital data is to be transmitted at a high speed, it is necessary to shorten the time (referred to as transition time) until the data signal is shifted from a high level to a low level (or from a low level to a high level). In order to shorten the transition time, the signal amplitude may be reduced. However, if the signal amplitude is reduced, there is a problem that it becomes weak against external noise. Therefore, a differential transmission method is known in which a signal having an opposite phase is transmitted using a pair of signal lines, and the difference between the transmission signals is data on the data reception side. In this method, a difference between signals having opposite phases is output on the reception side of the transmission signal. This differential output doubles the signal amplitude on the receiving side even if the signal width on the transmitting side is reduced. Noise entering the transmission line is canceled out because it is similarly superimposed on the pair of signal lines.

  The above signal transmission is said to be low voltage differential signaling (LVDS), and the data signal is transmitted as a differential signal with a small voltage change with a pair of conductors, and high speed and low consumption. Power and low noise can be realized. Such a signal transmission method includes HDMI (High-Definition Multimedia Interface), which is an integrated interface for transmitting video signals, audio signals, and control signals through a single cable, and Serial ATA, which is an interface for connecting a personal computer and a hard disk. It is said that it is efficient to use for (Advanced Technology Attachment).

  It is known that, for example, a cable as disclosed in Patent Document 1 is used to transmit a high-speed differential signal in the above-described application. As this cable, for example, there is a cable called a suede cable in which a plurality of differential cables as shown in FIG. As shown in FIG. 5 (A), this cable 9 has a differential cable 8 formed by shielding a pair of signal lines as shown in FIG. 5 (B). It is formed by heat-sealing cables.

  Each differential cable 8 is formed by covering the center conductor 1 with a dielectric layer 2 and providing a skin layer 3 on the outer periphery thereof as a signal line, and arranging two signal lines (4a, 4b) in parallel. . Next, drain lines 5a and 5b are disposed on both outer sides of the signal lines 4a and 4b arranged in parallel. Then, while maintaining this arrangement structure, the outer conductor 6 made of a metal foil tape is wound around the outer periphery thereof, and the outer side thereof is covered with the jacket layer 7 to form a final structure.

  As the central conductor 1, for example, a stranded wire having an outer diameter of 0.609 mm (AWG No. 24) is used by twisting seven silver-plated annealed copper wires. The dielectric layer 2 is formed by covering the outer periphery of the center conductor 1 with a porous PTFE (tetrafluoroethylene resin) tape having a thickness of 0.37 mm. The skin layer 3 is formed of FEP (tetrafluoroethylene-hexafluoropropylene copolymer resin) having a thickness of 0.09 mm and covers the outer surface of the dielectric layer 2.

As the drain wires 5a and 5b, twisted wires having a diameter smaller than that of the central conductor 1 and having an outer diameter of 0.306 mm (AWG 30) by twisting seven silver-plated annealed copper wires are used. The outer conductor 6 is formed by winding a metal vapor-deposited tape or the like spirally or vertically. The jacket layer 7 is formed of a halogen-free flame-retardant olefin resin with a thickness of 0.25 mm, the outer diameter on the long diameter side is 4.3 mm, and a plurality of sets of these are arranged in a parallel line to fuse the long diameter side surfaces together. It is integrated.
JP 2002-304921 A

  As a plasma display or a liquid crystal display becomes larger, a signal transmission cable used as an in-device wiring material becomes longer. At present, wiring with a length of about several tens of centimeters is attempted, for example, with a length of 2 m or more. In this case, a problem of transmission loss occurs, and it is difficult to cope with the problem by simply lengthening the current cable. For example, when the signal transmission cable is used in a high frequency region, the dielectric loss of the dielectric layer covering the signal line also increases as the frequency increases. In particular, the use frequency of HDMI is 825 MHz or more, and the transmission loss in this case is a value that cannot be ignored.

In order to avoid an increase in the transmission loss of the signal transmission cable, it is necessary to increase the thickness of the center conductor or the like, but the cable diameter of the suede cable disclosed in FIG. 5 is increased. For this reason, flexibility is lowered, handling becomes worse, and a problem of wiring space also arises.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a flat high-speed differential transmission cable including a plurality of signal line pairs reduced in loss without increasing the cable diameter.

  A high-speed differential transmission cable according to the present invention is a high-speed differential cable in which two electric conductors are paired as a signal line pair for differential transmission, a plurality of signal line pairs are arranged in a flat shape, and an insulating resin is extruded and covered. In a transmission cable, electric conductors consisting of multiple single core wires or stranded wires are arranged in parallel in a row at a predetermined interval and covered with an insulator made of insulating resin, and the outer periphery of the insulator is vertically attached with metal foil tape. Covered. Moreover, it is good also as a structure which covered the outer periphery of the said metal foil tape with the jacket which consists of insulating resin.

  A ground line is provided between the plurality of signal line pairs to reduce coupling between the signal line pairs. Further, the drain line is disposed in electrical contact with the metal foil tape to facilitate ground connection of the metal foil tape. The interval between the plurality of electric conductors is set to a narrow pitch of 0.5 mm or less so that predetermined transmission characteristics can be obtained. Moreover, an insulator and a metal foil tape are adhere | attached with an adhesive agent, and the adhesive agent for that is apply | coated to an insulator or a metal foil tape with the pattern of a striped steel plate.

In addition, the metal foil tape is provided with flame retardancy by being wound 1.5 times or more around the insulator. When the outer periphery of the metal foil tape is covered with a jacket, the jacket is formed of a mixed resin of a polyurethane resin and an ethylene vinyl acetate copolymer resin to provide flame retardancy.
In addition, 0.4% to 0.6% by weight of carbon black is added to the insulator to facilitate the processing of the metal foil with a YAG laser. Moreover, it is good also as a structure which attached the bending control member of the bending radius larger than the minimum bending radius which a metal foil tape does not cut | disconnect to the location where a cable is bent.

  According to the present invention, a low-loss high-speed differential transmission cable can be realized without increasing the diameter of the signal line, and the loss can be increased even when the wiring distance between the electronic devices or in the electronic device becomes long. Therefore, high-speed signal transmission can be performed efficiently.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section of a cable without a jacket, and FIG. 2 shows a cross section of a cable with a jacket. In the figure, 10a and 10b are high-speed differential transmission cables, 11 is an electrical conductor, 12 is an insulator, 13 is a metal foil tape, 14 is a drain wire, 15 is a jacket, Sp and Sn are signal lines, and S is a signal line. A pair G represents a ground line.

  As shown in FIG. 1, the high-speed differential transmission cable 10a of the present invention is formed by arranging a plurality of electric conductors 11 in a parallel row at a predetermined interval. The plurality of electric conductors 11 are covered with an insulator 12 made of an insulating resin, and a metal foil tape 13 serving as a shield conductor is wound around the outside in the longitudinal direction of the cable. If necessary, the drain wire 14 is disposed between the insulator 12 and the metal foil tape 13 so as to be in electrical contact. The drain line 14 is preferably disposed on one side or both sides of the side edge of the cable.

  The electric conductor 11 can be a good electric conductor such as copper or aluminum, or a single core wire or a stranded wire obtained by applying tin or silver plating to these. The electric conductor 11 preferably has a round line shape whose outer shape is substantially equal in length and width. Some flat cables use a flat conductor, but by using a round wire conductor, the coupling between signals that are differentially transmitted can be increased. Further, by strengthening the coupling between the signals, the eddy current induced in the shield conductor (metal foil tape 13) and the resulting Joule loss can be reduced and the attenuation can be reduced.

  Further, the electric conductor 11 is preferably a stranded wire rather than a single core wire from the viewpoint of flexibility. For example, seven conductor wires having an outer diameter of 0.06 mm are twisted (corresponding to AWG No. 34, outer diameter 0.18 mm). Can be used. The electric conductors are arranged in parallel on the same plane at a predetermined pitch P, and are integrally covered with an insulator 12 by extrusion molding of an insulating resin to form a flat multi-core insulated cable shape.

  The insulator 12 electrically insulates between the electric conductors 11, and is interposed between the electric conductors 11 and the metal foil tape for use in a high frequency region to form a capacitive coupling. Function as. For this reason, the insulator 12 is also called a dielectric, and its dielectric loss tangent (tan δ) and relative dielectric constant (ε) are also parameters that affect the characteristics of the transmission cable. The dielectric tangent of the insulator 12 is desirably small in terms of reducing dielectric loss, and the relative dielectric constant is desirably small in order to reduce the cable diameter.

  Therefore, it can be said that the lower the dielectric loss tangent and the relative dielectric constant of the insulator 12, the smaller the transmission loss, and the high-frequency signal can be transmitted efficiently. However, it is also necessary to ensure a predetermined characteristic impedance in connection with the device, and it is necessary to consider the combination of the dielectric material and the shape.

In the present invention, for example, a polyolefin-based resin is used as the insulating resin forming the insulator 12, and for example, a polyethylene resin or the like can be used. Polyethylene resin, the dielectric loss tangent is 4 × ¹⁰ about ^-4, relative dielectric constant is 2.3 to 2.4, a polyester resin (e.g., a dielectric loss tangent of 2 × ¹⁰ about ^-3 PET, the dielectric constant is It is smaller than 2.9 to 3.0) and can be said to be a preferable material. In addition, it is desirable that the insulator 12 is extruded by using an extruder with respect to a plurality of electric conductors 11 arranged at a predetermined interval.

  When the insulator 12 is extrusion-molded, the upper and lower planes of the insulator 12 are preferably formed as flat surfaces that do not cause dents between the electric conductors 11. Thereby, the space | interval of each electric conductor 11 and the metal foil tape 13 wound around the outer periphery of the insulator 12 can be made constant, and it can be set as uniform characteristic impedance.

  The metal foil tape 13 forms a predetermined capacitance distribution with the signal line of the electric conductor 11 as described above so that a predetermined characteristic impedance is obtained. In addition, the metal foil tape 13 has a function as a shield conductor that covers the outer periphery of the insulator 12 and prevents intrusion of noise signals (noise signals) from the outside or leakage of signals to the outside.

  The metal foil tape 13 is formed by bonding a metal foil 13a such as aluminum or copper to a plastic substrate 13b such as polyethylene terephthalate (PET) or by vapor deposition. The metal foil 13a and the plastic substrate 13b can be used with a thickness of several μm to several tens of μm, and the total thickness of the metal foil tape 13 is 0.01 mm to 0.05 mm. Is done. For example, a 9 μm thick copper foil can be used as the metal foil 13a, a 6 μm thick PET can be used as the tape substrate 13b, and a 15 μm thick CuPET tape can be used.

  The metal foil tape 13 is vertically attached to the insulator 12 with the metal foil surface inside, and is bent by the width of the insulator 12, and at least the overlapping portion is bonded and fixed by an adhesive 13c. By setting the metal foil surface of the metal foil tape 13 to the inside, the metal foil is not exposed on the outer surface of the cable, so that a certain range of durability as a cable can be provided even without a jacket.

  In addition, since the metal foil tape 13 needs to be impedance matched with the electric conductor 11, the distance from the electric conductor 11 needs to be constant. For this purpose, it is preferable that the metal foil tape 13 is firmly attached to the insulator 12 when the outer periphery of the metal foil tape 13 is not covered with the jacket 15. However, it is not necessary that the adhesive is applied on the entire surface without any gap. As will be described later, if the metal foil tape 13 is attached so as not to float from the insulator 12, the adhesive is striped or the like. It may be applied partially.

  The drain wire 14 is not necessarily required when the metal foil tape 13 itself can be easily grounded. However, by using the drain wire 14, the ground connection of the metal foil tape 13 can be facilitated and provided as necessary. The drain wire 14 is disposed separately from the electric conductor 11 described above, and is disposed so as to be sandwiched between the insulator 12 and the metal foil tape 13 on one side or both sides of the side edge of the cable. The drain wire 14 may be the same as the electric conductor 11, but may be thinner or thicker than the electric conductor 11. For example, it is possible to use a twisted lead wire having an outer diameter of 0.08 mm (corresponding to AWG No. 32, outer diameter of 0.24 mm).

  FIG. 2 shows a high-speed differential transmission cable 10b in which the outer side of the metal foil tape 13 is covered with a jacket 15 with respect to the high-speed differential transmission cable 10a without the jacket around which the metal foil tape 13 is wound. is there. Since the high-speed differential transmission cable 10b can have substantially the same configuration as the configuration described in FIG. 1 except for the configuration covered with the jacket 15, detailed description thereof is omitted.

  The jacket 15 is also called a jacket and is provided for protecting the entire cable including the metal foil tape 13. The outer cover 15 can be formed by extruding polyvinyl chloride, polyethylene or a mixed resin of a polyurethane resin and an ethylene vinyl acetate copolymer resin, which will be described later, using an extruder, or by winding a resin tape. . The outer jacket 15 electrically insulates and protects the metal foil tape 13, reinforces its mechanical strength, and further increases the strength to withstand bending.

  When the outer periphery of the metal foil tape 13 is covered with a jacket, the metal foil tape 13 may be wound so that the metal foil surface is on the outside. In this case, it can be protected and covered by covering with the outer jacket 15. When the metal foil tape 13 is wound so that the metal foil surface is on the outside, the drain wire 14 is disposed outside the metal foil tape 13. And it is set as the form pressed with the outer sheath 15 so that a metal foil surface may be contact | connected. Further, when the metal foil tape 13 is covered with the outer cover 15, the metal foil tape 13 does not necessarily have to adhere to the insulator 12.

  The high-speed differential transmission cables 10a and 10b according to the present invention are multi-core cables formed as described above, and two adjacent electric conductors 11 are made into one signal line pair. As shown in FIGS. 1 and 2, the signal line pair has at least two or more (for example, five pairs of S1 to S5). One signal line (Sp1 to Sp5) forming these signal line pairs is used for a positive potential signal, and the other signal line (Sn1 to Sn5) is used for an opposite negative potential signal. Further, when there is a margin in the number of electrical conductors 11, the electrical conductor between each signal line pair S is used as a ground line G to reduce signal coupling between adjacent signal line pairs S and crosstalk does not occur. You may do it.

  In the transmission path using the high-speed operation transmission cables 10a and 10b described above, on the transmission side, for example, in the signal line pair S1, the signal line Sp1 transmits a (+ V1) signal having a positive polarity, and the signal line Sn1 The (−V1) signal having a negative polarity is transmitted. On the receiving side, a level signal of 2V1 can be received by taking the difference between both signal levels “(+ V1) − (− V1)”. An external noise signal that enters the transmission path is added to the signal lines Sp1 and Sn1 in phase, but is canceled by taking a difference signal on the receiving side. The signal line pairs S are provided in a form in which a plurality of signal line pairs are arranged in parallel, and each signal line pair (S1 to S5) can individually transmit different signals.

  The ground line G arranged between each signal line pair S is set to the ground potential. The ground line G is preferably disposed so as to sandwich both sides of each signal line pair (S1 to S5), and is in an arrangement state in which both the signal lines Sp and Sn are electrically and physically balanced. However, the outside of the signal line pair S1 and S5 located at both ends of the cable can be omitted because the signal line pair S does not exist. In addition to this, in a form that does not affect the signal line pair S, for example, a power line or the like may be provided at a distance several times the arrangement pitch of the signal line group.

  The arrangement pitch P of the electric conductors 11 that form the signal lines Sp and Sn and the ground line G is a distance that can ensure electrical insulation, and considering the degree of coupling between the signal lines Sp and Sn, When the outer diameter of the conductor 11 is 0.18 mm (corresponding to AWG 34), it can be set to about 0.5 mm. The covering width D1 of the insulator 12 is selected in consideration of the dielectric constant of the insulator 12 so that the characteristic impedance becomes a predetermined value (for example, 100Ω). In the case where the outer cover 15 is provided, the outer cover width D2 is about 0.2 mm. The thickness depends on the thickness of the internal electrical conductor 11 and the thickness of the insulator 12. It is about 3.0 mm.

  In the above configuration, in order to increase the characteristic impedance, the diameter of the electric conductor 11 is reduced or the thickness of the insulator 12 is increased, but it is preferable to increase the thickness of the insulator 12 in terms of characteristics. . On the contrary, in order to reduce the characteristic impedance, the diameter of the electric conductor 11 is increased or the thickness of the insulator 12 is decreased, but it is preferable to increase the thickness of the electric conductor 11 in terms of characteristics.

  Further, the transmission loss of the cable is normally allowed up to 5.0 dB / use length. With a working length of 2 m, 2.5 dB / m is allowed. The transmission loss also varies depending on the frequency used. For example, at an HDMI usage frequency of 825 MHz, the electrical conductor 11 is 7 strands and the outer diameter is 0.18 mm (equivalent to AWG 34), and the conductor pitch P is The thickness D1 of the insulator 12 is 0.5 mm, which is the same as the conductor pitch P, 0.5 mm. When polyethylene is used for the insulator 12, the transmission loss is estimated to be 1.5 dB to 2.0 dB / m.

  On the other hand, in order to obtain a predetermined characteristic impedance by forming the same conductor pitch of 0.5 mm as described above with a suede cable using an extremely fine coaxial structure as shown in FIG. It is necessary to make the diameter 0.07 mm (twisted AWG # 40, outer diameter 0.09 mm). As a result, the transmission loss at the same use frequency 825 MHz as described above is 4 dB to 5 dB / m, which is twice that of the case of the present invention. On the other hand, in the conventional structure, in order to achieve the same transmission loss as that of the present invention, the width and thickness of the cable are increased, the wiring space is increased, and the handleability is also lowered.

  FIG. 3 is a diagram for explaining an embodiment relating to adhesion of a metal foil tape. FIG. 3 (A) is a diagram for explaining an example of the application form of the adhesive according to the present invention, FIG. 3 (B) is a diagram for explaining the electrical contact and adhesion state between the drain wire and the metal foil tape, and FIG. 3 (C). These are the figures explaining the adhesion part and non-adhesion part of a metal foil tape. In the figure, 16 is an adhesive stripe, 16a and 16b are short bar-like adhesive stripes, 17 is an adhesive stripe, 18 is a gap, 19 is an adhesive surface, and 20 is a non-adhesive surface.

  As described in the configuration example of FIGS. 1 and 2, the metal foil tape 13 maintains a constant separation distance between the metal foil of the metal foil tape 13 and the electric conductor 11, and the characteristic impedance is uniform over the entire length of the cable. It is desirable that When there is no jacket 15, it is preferable that the metal foil tape 13 and the insulator 12 are bonded and integrated with each other. For this reason, the adhesive is applied to the adhesive surface of either the metal foil tape 13 or the insulator 12. For example, a polyester-based adhesive can be used as the adhesive.

  The metal foil tape 13 and the insulator 12 need not be bonded uniformly over the entire surface. For this reason, the adhesive can be applied and adhered to the adhesive surface in various forms such as a zebra shape, a lattice shape, a polka dot shape, and a striped steel plate shape. However, various problems may occur depending on the application shape and application state. For example, when the drain wire 14 shown in FIGS. 1 and 2 is used, it is desirable that the drain wire 14 be fixed with an adhesive so that the drain wire 14 does not move or move. However, when the adhesive is applied to the metal foil tape 13 side, since the adhesive is usually an electrically insulating material, the electrical contact between the metal foil tape 13 and the drain wire 14 may be impaired. .

  FIG. 3B shows a form in which the drain wire 14 is in contact with the metal foil surface of the metal foil tape 13. As shown in this figure, the drain line 14 is held by being bonded with the width a of the adhesive stripe 17 generated by the application of the adhesive. A gap 18 having a distance b is formed between the adhesive stripes 17, and the drain wire 14 is bent so as to fall into the gap 18 and is in electrical contact with the metal foil tape 13. Therefore, if the space | interval b of the space | gap 18 is narrow, the contact state of the drain wire 14 and the metal foil tape 13 will fall. It has been found that there is no problem if the width a of the adhesive stripe 17 and the interval b of the gap 18 are a / b ≦ 2.

  Further, as shown in FIG. 3C, when the adhesive surface 19 and the non-adhesive surface 20 of the metal foil tape 13 and the insulator 12 are diagonally striped, for example, the NN line of the non-adhesive surface 20 When the metal foil tape is bent along the line A, the metal foil tape floats on the non-adhesive surface 20, and the impedance of the cable changes. Furthermore, if the sheet is repeatedly bent in this state, there is a possibility that a fold line is generated and the metal foil is broken.

  In consideration of the above matters, when there is no jacket and there is a drain wire, as an application form of the adhesive, as shown in FIG. It was found that it is preferable to apply to a pattern (also called a card plate). FIG. 3A shows an example in which adhesive stripes 16 are formed in a striped steel plate pattern on the adhesion surface of the developed metal foil tape 13. If there is no jacket 15 and no drain wire 14, the entire surface of the portion where the metal foil tape 13 and the insulator 12 are in contact with each other may be bonded, and any method of applying the adhesive may be used.

  When covering the metal foil tape 13 with the jacket 15, the jacket 15 presses the metal foil tape 13, so the metal foil tape 13 may or may not be bonded to the insulator 12. In this case, as shown in FIG. 3A, the striped steel plate-shaped adhesive stripes 16 may be bonded to one surface of the insulator or may be formed on the entire surface.

  This striped steel plate pattern is formed by alternately arranging short bar-shaped adhesive stripes 16a and 16b orthogonal to each other and inclining the whole in the longitudinal direction or the width direction. For example, the width of one piece of the adhesive stripes 16a and 16b is about 0.5 mm and the length is about 4.5 mm, and the adhesive stripes 16a and 16b are applied to the adhesive surface on the insulator or metal foil tape side at an arbitrary density. By using the striped steel plate-shaped adhesive stripes 16, for example, “a / b” described with reference to FIG. 3B can be reduced to about “1/8”. The foil can be brought into sufficient contact. Further, it is possible to prevent the linear non-adhesive surface 20 as described with reference to FIG. 3C from occurring, and the metal foil tape 13 does not float up in a streak shape.

In recent years, there is a high demand for a cable having flame retardancy, and a flame retardant cable having a hardness that passes the UL vertical combustion test VW-1 is required.
FIG. 4 is a diagram showing a configuration example for increasing the flame retardancy of the cable according to the present invention. In the cable without a jacket shown in FIG. 1, the overlapping portion where the metal foil tape 13 is wound vertically is formed with a narrow overlapping amount so as to hold the wound state by adhesion. However, if the overlapping amount of winding of the metal foil tape 13 is small, the adhesive at the overlapping portion melts due to combustion. Then, the polyethylene resin inside the tape is vaporized and leaks from the overlapped portion, and this burns and promotes the spread of the cable.

Therefore, as shown in FIG. 4, it is desirable to enlarge the overlapping portion of the winding of the metal foil tape 13. As a result of the test, the leakage of the combustion gas could be suppressed by winding the metal foil tape 13 1.5 times. Therefore, it is preferable that the metal foil tape 13 is wound 1.5 or more times around the outer periphery of the insulator, and the overlapping portion of the winding is 0.5 or more turns.
Further, in the case of the aluminum foil, the metal foil of the metal foil tape 13 was perforated at a thickness of 7 μm and failed the flame retardant test, and a thickness of 10 μm or more was necessary. In the case of copper foil, the flame retardant test was passed with a thickness of 7 μm. Therefore, it is preferable to use a copper foil tape to increase the flame retardancy.

  Further, in the cable having the jacket of FIG. 2, the flame retardancy can be enhanced by using a flame-retardant jacket material. Conventionally, flame-retardant polyethylene and polyvinyl chloride resin to which halogen-based flame retardants are added have been used as flame-retardant jackets. However, there is a demand for halogen-free flame-retardant cables that do not contain halogens due to environmental problems. It is high. In the present invention, as a cable jacket, a mixed resin of polyurethane resin and ethylene-vinyl acetate copolymer (EVA) resin (for example, see JP-A-2008-117609) is used to make the cable flame-retardant. Is realized. When covering the metal foil tape 13 with a flame retardant outer jacket, the metal foil tape 13 only needs to partially overlap.

When forming a terminal for connector connection or the like, it is desirable to cut the shield conductor portion using a YAG laser. Note that a CO ₂ laser is usually used for cutting the insulator portion. However, if the insulator is transparent or natural, the conductor inside the insulator may be deteriorated when the shield conductor is cut with a YAG laser. On the other hand, if the insulator is colored to make it difficult for the YAG laser to pass through, it becomes difficult to cut the insulator with the CO ₂ laser.

In the present invention, it is desirable to add carbon black to the insulator so that the color of the insulator is light black. The amount of carbon black added is preferably about 0.5 wt% (0.4 wt% to 0.6 wt%). With this amount of carbon black added, the YAG laser can cut only the metal foil tape without affecting the internal conductor. In addition, the insulator can be cut by a CO ₂ laser.

  In addition, in flat cables with shield conductors, the metal foil of the metal foil tape forming the shield conductor cracks if it is extremely bent (bent below the minimum bend diameter) regardless of whether there is a jacket or not. Or may be cut off. For this reason, a bending restricting means having a bending radius larger than the minimum bending radius at which the metal foil tape does not cut is provided at a portion to be bent so that the cable is not bent at a radius equal to or less than a predetermined bending radius. Is desired.

  In the present invention, a bending restricting member is previously provided by bonding or the like at a place where bending is assumed so that the cable cannot be bent below a predetermined bending diameter. The bending restricting member can be formed of a cylindrical member, a cylindrical member, a semicylindrical member, or a semicylindrical rod member. The radius of the curved surface of these bending regulating members is, for example, a bending radius of about 1.5 mm when the cable is bent at 90 °, and a bending radius of about 2.5 mm when the cable is bent at 180 °. can do.

It is a figure explaining the structural example of the high-speed differential transmission cable (without a jacket) by this invention. It is a figure explaining the structural example of the high-speed differential transmission cable (with a jacket) by this invention. It is a figure explaining embodiment regarding adhesion of the metal foil tape in the present invention. It is a figure explaining the incombustibility of the high-speed differential transmission cable by this invention. It is a figure explaining a prior art.

Explanation of symbols

10a, 10b ... high-speed differential transmission cable, 11 ... electrical conductor, 12 ... insulator, 13 ... metal foil tape, 14 ... drain wire, 15 ... jacket, 16 ... adhesive stripe, 16a, 16b ... short bar-like adhesive Stripes, 17 ... adhesion stripes, 18 ... gap, 19 ... adhesion surface, 20 ... non-adhesion surface, Sp, Sn ... signal line, S ... signal line pair, G ... ground line.

Claims (11)

A high-speed differential transmission cable in which two electric conductors are paired as a signal line pair for differential transmission, the signal line pairs are arranged in a flat shape, and an insulating resin is extruded and covered.
Electric conductors composed of a plurality of single core wires or stranded wires are arranged in parallel at a predetermined interval and are integrally covered with an insulator made of an insulating resin, and the outer periphery of the insulator is covered with a metal foil tape vertically. A high-speed differential transmission cable characterized by that.   The high-speed differential transmission cable according to claim 1, wherein an outer periphery of the metal foil tape is covered with an outer sheath made of an insulating resin.   The high-speed differential transmission cable according to claim 1, wherein a ground line is arranged between the plurality of signal line pairs.   The high-speed differential transmission cable according to any one of claims 1 to 3, wherein a drain wire is disposed in electrical contact with the metal foil tape.   The high-speed differential transmission cable according to any one of claims 1 to 4, wherein an interval between the plurality of electric conductors is 0.5 mm.   The high-speed differential transmission cable according to claim 1, wherein the insulator and the metal foil tape are bonded to each other.   The high-speed differential transmission cable according to claim 6, wherein an adhesive is applied to the insulator or the metal foil tape in a pattern of a draft steel plate.   The high-speed differential transmission cable according to claim 6, wherein the metal foil tape is wound about 1.5 times or more around the insulator.   The high-speed differential transmission cable according to claim 2, wherein the jacket is formed of a mixed resin of a polyurethane resin and an ethylene vinyl acetate copolymer resin.   10. The high-speed differential transmission cable according to claim 1, wherein carbon black is added to the insulator in an amount of 0.4 wt% to 0.6 wt%.   The bending restricting member having a bending radius larger than a minimum bending radius at which the metal foil tape is not cut is attached to the bent portion at at least one place. The high-speed differential transmission cable described in the section.

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