JP2010097882A - Extruded flat cable for differential transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aN extruded flat cable for differential transmission, capable of including DDC (display data channel) linea specialized in a low capacitance in a differential transmission line which requires transmission characteristics. <P>SOLUTION: Differential transmission conductors 3 constituting signal lines for differential transmission in sets each having two lines and low-capacitance lines are arranged in row and extrusion-coated with an insulating resin 12, and a common shield 13 is provided on the outside of the insulating resin. The short diameter of the insulating resin 12 is laterally uniform. The capacitance between a low-capacitance line conductor 4 constituting the low-capacitance line and the common shield is smaller than the capacitance between the differential transmission conductor 3 and the common shield 13, and the low-capacitance line conductor 4 is adjacent to only one pair of differential transmission conductors. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a differential transmission extruded flat cable that transmits 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 used as 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. Noise that enters 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). Data signals are transmitted as a differential signal with 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 over 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. 7A, a differential cable 508 formed by shielding a pair of signal lines as shown in FIG. 7A is arranged adjacent to each other in a plurality of parallel lines as shown in FIG. 7B. It is formed by heat-sealing cables.

  Each differential cable 508 is formed by covering a central conductor 501 with a dielectric layer 502 and providing a skin layer 503 on the outer periphery thereof as a signal line, and arranging two of these signal lines (504a, 504b) in parallel. . Next, drain lines 505a and 505b are disposed on both outer sides of the signal lines 504a and 504b arranged in parallel. Then, while maintaining this arrangement structure, the outer conductor 506 made of a metal foil tape is wound around the outer periphery, and the outer side thereof is covered with the jacket layer 507 to obtain a final structure.

  For example, a twisted wire having an outer diameter of 0.609 mm (AWG No. 24) is used as the center conductor 501 by twisting seven silver-plated annealed copper wires. The dielectric layer 502 is formed by covering the outer periphery of the central conductor 501 with a porous PTFE (tetrafluoroethylene resin) tape having a thickness of 0.37 mm. The skin layer 503 is formed of FEP (tetrafluoroethylene-hexafluoropropylene copolymer resin) having a thickness of 0.09 mm and covers the outer surface of the dielectric layer 502.

The drain wires 505a and 505b have a diameter smaller than that of the central conductor 501, and a stranded wire having an outer diameter of 0.306 mm (AWG 30) is formed by twisting seven silver-plated annealed copper wires. The outer conductor 506 is formed by winding a metal vapor-deposited tape or the like spirally or vertically. The jacket layer 507 is formed of a halogen-free flame-retardant olefin resin with a thickness of 0.25 mm, the outer diameter on the longer diameter side is 4.3 mm, and a plurality of sets of these are arranged in a parallel row to fuse the long diameter side surfaces. 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.
To avoid an increase in the transmission loss of signal transmission cables, it is necessary to increase the thickness of the center conductor, etc., but due to problems in handling and wiring space, the difference in which the loss is reduced without increasing the cable diameter. There is a demand for dynamic transmission extruded flat cables.

Further, in the HDMI standard, the upper limit of the capacitance of the DDC (Display Data Channel) line is determined, and the capacitance between SDA and GND and between SCL and GND in the cable assembly needs to be 700 pF / m. . For this reason, generally 100 pF / m or less is requested | required with respect to an electric wire, and about 65 pF / m may be calculated | required.
The present invention has been made in view of the above situation, and provides a flat cable having both a differential transmission line that requires transmission characteristics and a DDC line having a low capacitance.

The above object of the present invention is achieved by the following configuration.
(1) A differential transmission conductor and a low-capacity line constituting a signal line for differential transmission as a set of two wires are arranged in a row and are extrusion-coated with an insulating resin, and a common shield is placed outside the insulating resin. Provided,
The short diameter of the insulating resin is uniform in the width direction, and the capacitance between the low-capacity line conductor constituting the low-capacity line and the common shield is the difference between the differential transmission conductor and the common shield. A differential transmission extruded flat cable characterized in that there is only one pair of differential transmission conductor pairs adjacent to each other and having a low capacitance line conductor.

  According to this differential transmission extruded flat cable, the capacitance between the low-capacity line conductor and the common shield can be reduced. In addition, it is possible to include a differential transmission line requiring transmission characteristics and a DDC line specialized for low capacitance in one cable.

(2) The differential transmission extruded flat cable of (1),
The differential transmission extruded flat cable, wherein the low-capacity line conductor is thinner than the differential transmission conductor.

  According to this differential transmission extruded flat cable, the capacitance between the low-capacity line conductor and GND can be reduced.

(3) The differential transmission conductor of (2),
The low-capacity line conductor is individually coated with an insulator, and the dielectric constant of the insulator that individually covers the low-capacity line conductor is smaller than the dielectric constant of the insulating resin that covers the differential transmission conductor. Features differential transmission extruded flat cable.

(4) The differential transmission extruded flat cable according to any one of (1) to (3),
A differential transmission extruded flat cable, wherein an air layer is provided between the low-capacity line conductor and the common shield.

  According to this differential transmission extruded flat cable, the electrostatic capacity can be lowered by interposing an air layer.

(5) The differential transmission extruded flat cable of (4),
A differential transmission extruded flat cable, wherein a foamed resin layer is provided between the low-capacity line conductor and the common shield.

  According to this differential transmission extruded flat cable, the capacitance can be lowered by providing the foamed resin layer.

(6) The differential transmission extruded flat cable of (4),
A differential transmission extruded flat cable, wherein a spacer is disposed between the insulating resin and the common shield, and a space around the spacer is formed as a gas layer.

(7) The differential transmission extruded flat cable according to any one of (1) to (6),
A differential transmission extruded flat cable, wherein an intermediate shield is provided between the insulating resin around the differential transmission conductor and the common shield.

(8) The differential transmission extruded flat cable of (5),
An intermediate shield is provided between the insulating resin and the common shield around the differential transmission conductor,
The foamed resin layer and the intermediate shield are disposed on a single substrate,
A differential transmission extruded flat cable, wherein the base material is vertically attached to the insulating resin.

(9) The differential transmission extruded flat cable according to (6),
An intermediate shield is provided between the insulating resin and the common shield around the differential transmission conductor,
The spacer and the intermediate shield are disposed on a single substrate;
A differential transmission extruded flat cable, wherein the base material is vertically attached to the insulating resin.

(10) The differential transmission extruded flat cable according to any one of (1) to (9),
The differential transmission extrusion flat cable, wherein the insulating resin is made of a polyolefin resin, and the common shield is wound with 1.5 or more layers of the insulating resin.

  This differential transmission extruded flat cable can pass the vertical flame retardant test.

(11) The differential transmission extruded flat cable according to any one of (1) to (9),
The insulating resin is a polyolefin resin;
The common shield is covered with a jacket;
The differential transmission extruded flat cable, wherein the jacket is a flame retardant resin or a mixed resin of polyurethane and EVA.

  According to this differential transmission extruded flat cable, since the jacket is made of flame retardant, it passes the vertical flame retardant test without winding the common shield 1.5 times. PVC may be used as long as it is not related to a halogen-free material. The outer cover has not only a function of imparting flame retardancy but also a main effect of improving mechanical strength. A polyolefin (polyethylene or polypropylene) may be used as long as the mechanical strength is improved even if it is not flame retardant.

(12) The differential transmission extruded flat cable according to any one of (1) to (11),
A differential transmission extruded flat cable, wherein 0.1 wt% to 0.5 wt% of carbon black is added to the insulating resin.

According to this differential transmission extruded flat cable, the internal conductor is not affected when the common shield is cut by the YAG laser. Further, the insulator can be cut with a CO ₂ laser.

(13) The differential transmission extruded flat cable according to any one of (1) to (12),
A differential transmission extruded flat cable, wherein a bending restricting member having a bending radius larger than a minimum bending radius that is not cut by the common shield is attached to the bent portion at at least one portion.

  According to this differential transmission extruded flat cable, cracking and cutting of the metal foil tape (forming tape) forming the common shield by being bent at the minimum bending diameter or less are prevented.

(14) The differential transmission extruded flat cable according to any one of (1) to (13);
An electrical connector connected to at least one end thereof;
A differential transmission extruded flat cable with a connector, characterized by comprising:

  According to this differential transmission push-out flat cable, the connection to various systems can be easily performed by connecting the electrical connector to the end.

  According to the present invention, a flat cable including a differential transmission line that requires transmission characteristics such as low attenuation and impedance and a DDC line having a low capacitance can be realized.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a differential transmission extruded flat cable according to the invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a differential transmission extruded flat cable according to the present invention, and FIG. 2 is an enlarged view of a common shield bonding portion.
The differential transmission extruded flat cable 1 according to the present embodiment includes differential transmission conductors that constitute a plurality of signal lines that perform differential transmission as a set of two cables. Two differential transmission conductors are paired to transmit signals. The differential transmission extruded flat cable includes a low capacity wire. The low capacitance of the low capacitance line means that the capacitance between the low capacitance line conductor and the common shield included in the low capacitance line is larger than the capacitance between the differential transmission conductor 3 and the common shield. It means small. In FIG. 1, the low-capacity line is formed by covering a low-capacitance line conductor 4 with an insulator 16. However, the insulator 16 may not be provided, and in this case, the low-capacitance line conductor 4 becomes a low-capacity line. In FIG. 1, there are shown a plurality of low-capacitance lines that constitute the low-capacitance-line conductor group 5, but there may be one low-capacitance line. There are at least a pair of differential transmission conductors 3. There is only one pair of differential transmission conductor pairs adjacent to low-capacity line conductors. As shown in FIG. 1, it can also be said that the differential transmission conductors 3 form one group and the low capacitance line is not included in the group. Since the low-capacity line conductor is outside the differential transmission conductor group, the differential transmission conductor is only in one of the low-capacity line conductors. That is, the differential transmission conductor adjacent to the low-capacity line conductor is only on one side of the low-capacity line conductor. Since the differential transmission conductor 3 and the low capacitance line are arranged in a line, it can be said that the low capacitance line is not sandwiched between the differential transmission conductors 3. The differential transmission conductor group 2 may include a ground line conductor G disposed between the signal line pairs. The differential transmission conductor group 2 and the low-capacity line are extrusion-coated with an insulating resin 12 to cover the differential transmission conductor group 2 and the low-capacity line (the low-capacity line group 5 when there are a plurality of low-capacity lines). A metal foil tape 13 as a shield is provided outside the insulating resin 12.

  The low capacity line group 5 includes DDC (display data channel), SCL (serial clock input line), SDA (serial data input / output line), and the like. In FIG. 1, white circles 9 indicate undefined discarded cores.

  The differential transmission extruded flat cable 1 of the present invention is formed by arranging a plurality of differential transmission conductors 3 and low-capacity line conductors 4 in a parallel row at a predetermined interval. The plurality of differential transmission conductors 3 and the low-capacity line conductors 4 are integrally covered with an insulating resin 12, and a metal foil tape 13 is vertically wound around the outside in the longitudinal direction of the cable. Further, if necessary, the drain wire (not shown) is arranged in parallel with the conductor so as to be in electrical contact with the metal foil tape 13. The drain wire is preferably disposed on one side or both sides of the side edge of the cable.

  The differential transmission conductor 3 may be a good electrical conductor such as copper or aluminum, or a single core wire or a stranded wire in which tin or silver is plated. The differential transmission conductor 3 is preferably a round wire having a diameter of 0.1 to 0.254 mm. 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 differential transmission conductor 3 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 electrical conductors are arranged in parallel on the same plane at a predetermined pitch P, and are covered with the insulating resin 12 by extrusion molding to form a flat multi-core insulated cable.

  The insulating resin 12 electrically insulates between the differential transmission conductors 3 and is interposed between the differential transmission conductors 3 and the metal foil tape 13 for use in a high frequency region, It functions as a capacitor that forms electrostatic coupling. For this reason, the insulating resin 12 is also referred to as 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 loss tangent of the insulating resin 12 is desirably small in terms of reducing dielectric loss, and the relative dielectric constant is desirably small in order to reduce the capacitance.

  It can be said that the lower one of the dielectric loss tangent and the relative dielectric constant of the insulating resin 12 is, the smaller the transmission loss is, and the high frequency signal can be efficiently transmitted. 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 for the insulating resin 12, and for example, a polyethylene resin or the like can be used. The polyethylene resin has a dielectric loss tangent of about 4 × 10 ⁻⁴ , a relative dielectric constant of 2.3 to 2.4, and a polyester resin (for example, a dielectric loss tangent of about 2 × 10 ⁻³ and a relative dielectric constant of PET). Smaller than 2.9 to 3.0). Therefore, it is preferable that the insulating resin 12 is obtained by extrusion-molding polyethylene using an extruder because the dielectric loss of the high-frequency signal is small.

  When the insulating resin 12 is extruded, it is desirable that the upper and lower planes of the insulating resin 12 are formed as flat surfaces that do not cause a dent between the differential transmission conductor 3 and the low-capacity line conductor 4. . Thereby, the short axis (indicated by D1 in FIG. 1) of the insulating resin is uniform in the width direction of the insulating resin (left and right direction in FIG. 1). Therefore, the distances between the differential transmission conductors 3 and the low-capacitance line conductors 4 and the metal foil tape 13 wound around the outer periphery of the insulating resin 12 are constant, and uniform impedance can be obtained.

  As described above, the metal foil tape 13 forms a predetermined capacitance distribution with the signal line of the differential transmission conductor 3 so as to obtain a predetermined impedance. In addition, the metal foil tape 13 has a function as a shield conductor that covers the outer periphery of the insulating resin 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 attaching or vapor-depositing a metal foil 13a such as aluminum or copper shown in FIG. 2 to a plastic substrate 13b such as polyethylene terephthalate (PET). 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 overall 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 13 a, a 6 μm thick PET can be used as the tape base material 13 b, and a 15 μm thick CuPET tape can be used.

  The metal foil tape 13 is vertically attached to the insulating resin 12 with the metal foil surface inside, and is bent at the width of the insulating resin 12, and at least the overlapping portion is bonded and fixed by the adhesive 13c. By setting the metal foil surface of the metal foil tape 13 to the inner side, 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 the jacket 15. Further, since the metal foil tape 13 needs to be impedance matched with the differential transmission conductor 3, the separation distance from the differential transmission conductor 3 needs to be constant. The separation distance is the distance in the thickness direction of the flat cable between the conductor and the metal foil tape (shown in the figure). For this purpose, when the outer periphery of the metal foil tape 13 is not covered with the jacket 15, it is preferable that the metal foil tape 13 is firmly attached to the insulating resin 12. For example, a polyester-based adhesive can be used as an adhesive for attaching the two.

  When the outer periphery of the metal foil tape 13 is covered with the jacket 15, 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. Further, when the metal foil tape 13 is wound so that the metal foil surface is on the outside, the drain wire 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 touched. When covering the metal foil tape 13 with the jacket 15, the metal foil tape 13 does not necessarily have to adhere to the insulating resin 12.

  A differential transmission push-out flat cable 1 according to the present invention includes a signal line pair including two adjacent differential transmission conductors 3 as a set. A plurality of signal line pairs (for example, four pairs of S1 to S4) can be included. One signal line (Sp1 to Sp4) forming these signal line pairs is used for a positive potential signal, and the other signal line (Sn1 to Sn4) is used for an opposite negative potential signal. Further, when there is a margin in the number of the differential transmission conductors 3, the electric conductor between each signal line pair S is used as a ground line G, and signal coupling between adjacent signal line pairs S is reduced, and crosstalk is achieved. May not occur.

  In the transmission line using the differential transmission push-out flat cable 1 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 a parallel row, and each signal line pair (S1 to S4) 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 S4), 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 S4 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 differential transmission conductors 3 that form the signal lines Sp and Sn and the ground line G is a distance that can ensure electrical insulation, and also considers the degree of coupling between the signal lines Sp and Sn. Then, when the outer diameter of the differential transmission conductor 3 is 0.18 mm (equivalent to AWG 34), it can be set to about 0.5 mm. The short diameter D1 of the insulating resin 12 is selected in consideration of the dielectric constant of the insulating resin 12 so that the impedance becomes a predetermined value (for example, 100Ω). When the outer cover 15 is provided, the outer cover 15 has a coating thickness of about 0.2 mm. Depending on the thickness of the internal differential transmission conductor 3 and the insulating resin 12, the outer diameter of the outer cover 15 may be increased. D2 is about 1.0 mm to 3.0 mm.

  In the above configuration, in order to increase the impedance, the diameter of the differential transmission conductor 3 is reduced, or the thickness of the insulating resin 12 is increased. From the viewpoint of transmission loss, the thickness of the insulating resin 12 is increased. It is preferable to increase. On the other hand, in order to reduce the characteristic impedance, the diameter of the differential transmission conductor 3 is increased or the thickness of the insulating resin 12 is decreased. From the viewpoint of transmission loss, the thickness of the differential transmission conductor 3 is reduced. Is preferably increased.

  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 the HDMI usage frequency of 825 MHz, the conductor 3 for differential transmission 3 has seven strands and an outer diameter of 0.18 mm (equivalent to AWG 34). The pitch P is 0.5 mm, and the thickness D1 of the insulating resin 12 is 0.5 mm, which is the same as the conductor pitch P. When polyethylene is used for the insulating resin 12, the transmission loss is estimated to be 1.5 dB to 2.0 dB / m.

  On the other hand, in order to obtain an impedance of 100 Ω by forming the same conductor pitch as described above at 0.5 mm with a suede cable using an extremely fine coaxial structure as shown in FIG. It is necessary to make a small diameter of 03 mm 7-strand (corresponding to AWG No. 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.

  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. If the overlapping amount of winding of the metal foil tape 13 is small, the adhesive at the overlapping portion melts during the combustion test. Then, the polyethylene resin inside the tape is vaporized and leaks from this overlapping portion, and this burns and promotes the spread of the cable.

  On the other hand, as shown in FIG. 3, the differential transmission extruded flat cable 1 </ b> A in which the overlapping portion of the winding of the metal foil tape 13 is enlarged can pass the vertical flame retardant test. As a result of the test, it was possible to suppress the leakage of the combustion gas by winding the metal foil tape 13 1.5 times and setting the overlapping portion of the winding to 0.5. 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 turns or more.

  The metal foil of the metal foil tape 13 has a thickness of 6 to 20 μm. In the case of aluminum foil, a hole was perforated at 7 μm and the flame retardant test was rejected, and a thickness of 10 μm or more was required. 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. PET etc. can be used for resin of a metal foil tape, and the thickness shall be 7-20 micrometers.

  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 strengthens the strength to withstand bending.

  In the cable having the jacket 15, flame retardance can be improved by using a flame retardant material for the jacket. Conventionally, flame retardant outer sheath 15 is made of flame retardant polyethylene or polyvinyl chloride resin to which halogenated flame retardants are added. However, halogen-free flame retardant cables that do not contain halogen are required due to environmental problems. Is high. In the present invention, as the cable jacket 15, a mixed resin of polyurethane resin and ethylene-vinyl acetate copolymer (EVA) resin (see, for example, Japanese Patent Application Laid-Open No. 2008-117609) is used. Has been realized. When the metal foil tape 13 is covered with the flame retardant outer cover 15, the metal foil tape 13 only needs to partially overlap.

  In the case where the outer cover 15 is provided, if the outer cover 15 is made of a flame-retardant material, the common shield may not be wound 1.5 times. PVC may be used as long as it is not related to a halogen-free material. The outer cover 15 has not only a function of imparting flame retardancy but also a main effect of improving mechanical strength. A polyolefin (polyethylene or polypropylene) may be used as long as the mechanical strength is improved even if it is not flame retardant.

  When the metal foil tape 13 floats from the insulating resin 12, the impedance is different, so that the metal foil tape 13 is attached to the insulating resin 12 when there is no jacket.

  An intermediate shield 7 may be provided between the insulating resin 12 and the metal foil tape 13 around the differential transmission conductor group 2. The intermediate shield is made of metal foil or metal foil tape. As the metal foil, a copper foil or an aluminum foil having a thickness of several μm to several tens of μm can be used. A metal foil tape similar to the common shield can be used. In the case of using a metal foil tape, it is possible to use a metal foil such as copper, copper alloy, or aluminum attached to a base material such as PET. A base material layer such as PET is on the insulating resin 12 side (inner side), and the metal foil layer is on the outer side. As a result, the differential transmission conductor 3 is double-shielded to increase the shielding effect. Further, even when the common shield is removed at the end portion of the flat cable, the impedance can be brought close to a predetermined value at the end portion of the differential transmission line by leaving the intermediate shield. In this case, the metal foil tape 13 does not function as a ground layer. Drop from the middle shield 7 to ground. Since the metal foil is on the outside, the intermediate shield is exposed and a ground bar is connected to it, and the circuit connected to the ground bar is dropped to the ground. In this case, the drain line is unnecessary.

FIG. 4 is a cross-sectional view of the main part of the conductor group for low capacitance lines.
The low-capacity line conductor 4 is preferably formed with a smaller diameter than the differential transmission conductor 3. When the conductor diameter of the low-capacity line conductor 4 is reduced, the capacitance between the corresponding core and the common shield can be reduced. The diameter of the low-capacitance line conductor 4 can be 0.02 to 0.254 mm. It is preferable to make the diameter of the low-capacity wire, which may be either a single wire or a stranded wire, smaller than the diameter of the differential transmission conductor. In this case, the diameter of the low-capacity wire conductor is preferably 0.063 mm (diameter obtained by twisting seven strands having a diameter of 0.021 mm) or less. The low capacity line conductor 4 may be individually covered with the insulator 16. It is preferable that the diameter of the insulator 16 is formed to be the same as that of the differential transmission conductor 3. The insulator 16 preferably has a low dielectric constant, and in that respect, a fluororesin is preferable. Polyethylene, EVA, EEA, a mixture thereof, or the same material as the insulating resin 12 may be used.

  By making the differential transmission conductor 3 and the low-capacity wire conductor 4 have the same diameter, the hole diameter of the conductor guide at the extrusion point in the extruder can be unified, and the versatility of the conductor guide is ensured. The distance from the low capacity line conductor 4 to the metal foil tape 13 is longer than the distance from the differential transmission conductor 3 to the metal foil tape 13. As a result, the capacitance between the low-capacity line conductor 4 and the common shield is reduced.

  When polyethylene is used for the differential transmission conductor group 2 and the insulating resin 12, and a fluororesin having a dielectric constant lower than that of polyethylene is used for the low-capacity line insulator 16, the low-capacity line is a low-capacity line conductor. The capacity becomes lower when it is as thin as possible and the coating of the fluororesin is as thick as possible. In this case, the diameter of the low-capacity line (fluororesin insulator) may be larger than the diameter of the differential transmission conductor.

  In order to reduce the electrostatic capacitance between the low-capacitance line conductor 4 and the common shield, there is a means for lowering the dielectric constant between the low-capacity line conductor and the common shield by including an air layer. In order to include an air layer, the insulating resin 12 is foamed, a foam layer is provided between the insulating resin 12 and the common shield separately from the insulating resin 12, and a spacer is placed between the insulating resin 12 and the common shield. Thus, the common shield is lifted by the spacer, and a gas layer can be provided around (side) the spacer. Examples of the gas contained in the foam layer and the air layer include air, nitrogen, and carbon dioxide.

FIG. 5 is a cross-sectional view of a main part of a differential transmission extruded flat cable in which an air layer is formed. An air layer 17 is provided between the low-capacity line conductor 4 and the metal foil tape 13. By interposing the air layer 17 between the metal foil tape 13 and the insulating resin 12, the space between the low-capacitance line conductor 4 and the common shield can be reduced to a low capacitance. In order to provide the air layer 17, spacers 18 are placed between the metal foil tape and the insulating resin and at the upper and lower portions between the conductors. Air layers 17 are formed on the upper and lower portions of the conductor without the spacer 18. By providing the spacer 18, the air layer 17 is secured at a constant distance, and the capacitance between the low-capacitance line conductor 4 and the common shield is stabilized at a low value. The spacer 18 can be disposed on one common base 6 and the common base 6 can be vertically attached to the insulating resin 12. The air layer 17 can be easily formed by winding the metal foil tape 13 thereon. A low dielectric constant resin film can be used for the spacer and the common substrate. Fluororesin, polyethylene, EVA, EEA, etc., and mixtures thereof can be used. In FIG. 5, the spacers 18 are arranged between all the low-capacity line conductors 4. However, as long as an air layer is secured, the spacers 18 are not necessarily arranged between all the low-capacity line conductors 4. Good.
Even if a resin film with a groove cut is inserted between the insulating resin 12 and the common shield, an air layer can be formed in the same manner as the spacer and the common substrate.

  Even if a foamed layer containing a gas is provided between the low-capacity line conductor 4 and the common shield, the capacitance between them can be lowered. For example, a foamed resin film can be interposed between the insulating resin 12 and the common shield. A resin film obtained by foaming a fluororesin, polyethylene, polypropylene, EVA, EEA, or a mixture thereof can be used. The aforementioned spacer may be a foamed resin film.

As described above, an intermediate shield may be provided between the insulating resin 12 around the differential transmission conductor group 2 and the common shield. Thereby, the ground potential for the differential transmission conductor can be easily obtained, and the impedance between the differential transmission conductor and the intermediate shield (ground layer) can be stabilized. On the other hand, the low-capacity line conductor group 5 is less required to match the impedance and increase the shielding effect than the differential transmission conductor group 2, and the low-capacity line conductor 4 and the common shield are less than that. There is a high need for a low capacity. Therefore, an intermediate shield is provided between the insulating resin 12 and the common shield in the portion around the differential transmission conductor group, and at the same time, air is provided between the insulating resin 12 and the common shield in the portion around the low-capacity line conductor. When a layer or a foamed resin layer is provided, an effect required for each conductor group is exhibited. If these are arranged on a common base material, both can be made by simply interposing the common base material between the insulating resin 12 and the metal foil tape 13 which is a common shield in the manufacture of the extruded flat cable. Easy. Specifically, the following combinations are bonded and arranged on the common substrate 6.
(Things placed around the conductor group for differential transmission) (Things placed around the conductor (group) for low capacity wires)
Intermediate shield Foamed resin layer Intermediate shield Spacer for creating an air layer Intermediate shield Resin with grooves cut to create an air layer
Film The common base material is vertically attached to the insulating resin 12, and a metal foil tape 13 is wound around the same. In order to prevent the intermediate shield from floating, it is desirable to bond the common base 6 and the insulating resin 12 together.
The thickness of the intermediate shield and the height of the foamed resin layer or the spacer need not match. The thickness of the foam layer or the gas layer can be 0.03 to 0.1 mm. On the other hand, the thickness of the intermediate shield can be 0.013 to 0.04 mm.

In the differential transmission extruded flat cable 1, it is desirable to cut the metal foil tape 13 with a YAG laser when forming a terminal for connector connection or the like. However, if the insulating resin 12 is transparent or natural, the conductor inside the insulating resin 12 may be deteriorated when the metal foil tape 13 is cut with a YAG laser. Therefore, if the insulating resin 12 is colored to make it difficult for the YAG laser to pass through, it becomes difficult to cut the insulating resin 12 by the CO ₂ laser.

Therefore, it is desirable to add about 0.15 wt% (0.1 wt% to 0.5 wt%) of carbon black to the insulating resin 12 so that the color of the insulating resin 12 is light black. With this amount of carbon black added, only the metal foil tape 13 can be cut without the YAG laser affecting the internal conductor. Further, the insulating resin 12 can be cut by a CO ₂ laser.

  In a flat cable having a shield conductor, the metal foil tape 13 forming the shield conductor is cracked or cut when it is extremely bent (bent at or below the minimum bend diameter) regardless of the presence or absence of the jacket. There are things to do. For this reason, a bending restricting means (not shown) having a bending radius larger than the minimum bending radius at which the metal foil tape 13 is not cut is provided at a bent portion so that the cable is not bent at a radius equal to or less than a predetermined bending radius. It is desirable to have it.

  By providing the bending restricting member, cracking and cutting of the metal foil tape 13 forming the common shield by being bent at the minimum bending diameter or less are prevented. Whether or not the outer cover 15 is present, the metal foil tape 13 can be cut if it is bent extremely (if it is bent beyond the minimum bending radius). A bending restricting member having a radius equal to or larger than the minimum bending radius is applied to the bent portion and fixed so that the metal foil tape 13 is not cut. For example, a bar or the like that is a bending regulating member is bonded, and an adhesive tape is wound around the bent portion (fixed so that the bar is wrapped). In the case of bending at 90 °, about 1.5 mm is the lower limit bending radius at which the metal foil tape 13 (Cu-PET copper) does not crack. Moreover, when it is bent at 180 °, that is, when it is folded up, about 2.5 mm is the lower limit bending radius at which Cu-PET copper does not crack.

  In order to manufacture the differential transmission extruded flat cable 1 shown in FIG. 1, a plurality of differential transmission conductors 3, low-capacity line conductors 4, other ground line conductors G, etc. arranged at predetermined intervals are used. The insulating resin 12 is extruded and formed on the conductor using an extruder to obtain a flat cable body. When the flat cable body is pushed out, the upper and lower planes of the insulating resin 12 are formed as flat surfaces so that no dent is generated between the differential transmission conductor 3 and the low-capacity line conductor 4 as described above. Next, an intermediate shield 7, foamed polyethylene 8, or the like is pasted on the common substrate 6. The width of the intermediate shield 7 is the same as or slightly wider than the width of the differential transmission conductor group 2. The width of the foamed polyethylene 8 is the same as the width of the conductor group 5 for low-capacity wires, but is slightly wider. The common base 6 is vertically attached to the top and bottom of the insulating resin 12, and the upper and lower surfaces of the differential transmission conductor group 2 are sandwiched between the intermediate shields 7 and 7, and the upper and lower surfaces of the low capacitance line conductor group 5 are sandwiched between the foamed PP8. . After covering these outer periphery with the metal foil tape 13, the jacket 15 is coat | covered as needed, and the differential transmission extrusion flat cable 1 is obtained.

FIG. 6 is a plan view of a differential transmission extruded flat cable with a connector.
Electrical connectors 20 and 21 are connected to both ends of the differential transmission extruded flat cable 1 to form a differential transmission extruded flat cable 1B with a connector. In the terminal processing of the differential transmission extruded flat cable 1 for connection to the electrical connectors 20 and 21, if there is a jacket 15, it is removed by cutting with a CO ₂ laser. The metal foil tape 13 is removed by cutting with a YAG laser. When cutting the metal foil tape 13 with a YAG laser, the internal insulating resin 12 is not deteriorated. The intervening layer, the foamed PP8, and the insulating resin 12 are removed by cutting with a CO ₂ laser.

  Each conductor of the differential transmission extruded flat cable 1 subjected to terminal processing is connected to the electrical contact portions of the electrical connectors 20 and 21. The line pitch is constant, and the connector contacts are also the same pitch. When the differential transmission conductor and the low-capacity line are separated by a certain pitch or more, they are separated by an integral multiple of the certain pitch, and the connector contacts (or pins) between them are skipped. The differential transmission extruded flat cable 1B with connector thus obtained can be easily connected to various systems.

  According to the present invention, a differential transmission flat cable including a differential transmission line that requires transmission characteristics such as attenuation and impedance and a DDC line specialized for low capacitance can be realized.

  Since the present invention is a flat cable and is thinner than a round cable, it can be wired even in a narrow clearance portion when wiring in a device. In addition, since a plurality of differential transmission pairs and low-capacity lines such as DDC lines can be wired at once by simply connecting a single cable to the connector, it does not take time for wiring. If the differential transmission pair and the low-capacity line are separate cables, two connectors are provided at each end. However, in the present invention, one connector is provided at each end, and the exclusive area of the connector on the board can be reduced.

A result obtained by manufacturing a differential transmission extruded flat cable having a configuration corresponding to the above-described embodiment will be described.
A single conductor having a diameter of 0.16 mm was used as the differential transmission conductor.

  A wiring material used in HDMI has a DDC line in addition to a differential transmission line, a power supply line, a GND line, etc., and a DDC line which is a low capacity line does not require transmission characteristics such as attenuation and impedance. Therefore, the outer diameter of a silver-containing copper alloy wire of 0.063 mm (a wire obtained by twisting seven strands having a diameter of 0.021 mm) was selected as the conductor for the DDC line. PFA was insulated from this conductor so as to have a short diameter φ0.16 mm.

By making the diameter of the DDC line the same as that of the differential transmission conductor, it becomes easy to arrange the lines on the same plane. Since PFA has a melting point of 300 ° C. and is lower than the melting point of polyethylene to be coated (around 100 ° C.), problems such as external damage and abrasion can be prevented when a polyethylene-coated resin layer is extruded thereon.
The conductor for differential transmission and the conductor for low-capacity line were arranged at a pitch of 0.5 mm and extrusion-coated with polyethylene to make the short diameter (thickness) 0.475 mm.
The upper and lower surfaces of four differential pairs of insulating resin (polyethylene) were covered with an intermediate shield (metal tape) for impedance matching, and the upper and lower surfaces of the DDC line were covered with foamed polyethylene to achieve low capacitance. Copper PET tape was used for the intermediate shield. The thickness of the copper foil was 9 μm, and the thickness of PET was 12 μm. The thickness of the foamed polyethylene was 0.03 mm. Copper PET tape and polyethylene foam are affixed on a common substrate (PET tape), and the adhesive surface (polyester) is coated on the PET surface that comes in contact with the insulating resin, and the common substrate is affixed to the insulating resin. It was.
A copper PET tape of the same material and thickness as the intermediate shield was wrapped around it to make a common shield.

As a result of measuring the differential transmission extruded flat cable obtained in the example, the electrostatic capacitance between the conductor of the DDC line and the common shield is 100 pF / m with respect to the capacitance between the conductor of φ0.16 mm and the common shield. The capacity was successfully reduced to 65 pF / m.
The impedance of the differential wire could be 100Ω (50Ω per one), and the transmission loss per 1 m of cable could be 2.2 dB / 1 GHz, 3.4 dB / 2 GHz, 4.5 dB / 3 GHz. .

It is sectional drawing of the differential transmission extrusion flat cable which concerns on this invention. It is an enlarged view of a common shield adhesion part. It is sectional drawing of the differential transmission extrusion flat cable which concerns on the modification by which the common shield was wound 1.5 times. It is principal part sectional drawing of the conductor group for low capacity lines. It is principal part sectional drawing of the differential transmission extrusion flat cable in which the air layer was formed. It is a top view of a differential transmission extrusion flat cable with a connector. Similar to 108Y0218 (A) is a front view of the conventional differential transmission extrusion flat cable, (b) is the perspective view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Differential transmission extrusion flat cable 1B Differential transmission extrusion flat cable with a connector 2 Conductor group for differential transmission 3 Conductor for differential transmission 4 Conductor for low capacity line 5 Conductor group for low capacity line 6 Common base material (base material)
7 Intermediate shield 12 Insulating resin 13 Metal foil tape (common shield)
DESCRIPTION OF SYMBOLS 15 Outer coating 16 Insulator 17 Air layer 18 Foamed resin layer 20, 21 Electrical connector S Signal line pair

Claims (14)

A differential transmission conductor and a low-capacitance line constituting a signal line for differential transmission as a set of two wires are arranged in a row and extruded with an insulating resin, and a common shield is provided outside the insulating resin,
The short diameter of the insulating resin is uniform in the width direction, and the capacitance between the low-capacity line conductor constituting the low-capacity line and the common shield is the difference between the differential transmission conductor and the common shield. A differential transmission extruded flat cable characterized in that there is only one pair of differential transmission conductor pairs adjacent to each other and having a low capacitance line conductor. The differential transmission extruded flat cable according to claim 1,
The differential transmission extruded flat cable, wherein the low-capacity line conductor is thinner than the differential transmission conductor. The differential transmission conductor according to claim 2,
The low-capacity line conductor is individually coated with an insulator, and the dielectric constant of the insulator that individually covers the low-capacity line conductor is smaller than the dielectric constant of the insulating resin that covers the differential transmission conductor. Features differential transmission extruded flat cable. The differential transmission extruded flat cable according to any one of claims 1 to 3,
A differential transmission extruded flat cable, wherein an air layer is provided between the low-capacity line conductor and the common shield. The differential transmission extruded flat cable according to claim 4,
A differential transmission extruded flat cable, wherein a foamed resin layer is provided between the low-capacity line conductor and the common shield. The differential transmission extruded flat cable according to claim 4,
A differential transmission extruded flat cable, wherein a spacer is disposed between the insulating resin and the common shield, and a space around the spacer is formed as a gas layer. The differential transmission extruded flat cable according to any one of claims 1 to 6,
A differential transmission extruded flat cable, wherein an intermediate shield is provided between the insulating resin around the differential transmission conductor and the common shield. The differential transmission extruded flat cable according to claim 5, wherein an intermediate shield is provided between the insulating resin around the differential transmission conductor and the common shield, and the foamed resin layer and the intermediate shield are integrated. Placed on one substrate,
A differential transmission extruded flat cable, wherein the base material is vertically attached to the insulating resin. The differential transmission extruded flat cable according to claim 6, wherein an intermediate shield is provided between the insulating resin and the common shield around the differential transmission conductor,
The spacer and the intermediate shield are disposed on a single substrate;
A differential transmission extruded flat cable, wherein the base material is vertically attached to the insulating resin. The differential transmission extruded flat cable according to any one of claims 1 to 9,
The differential transmission extrusion flat cable, wherein the insulating resin is made of a polyolefin resin, and the common shield is wound with 1.5 or more layers of the insulating resin. The differential transmission extruded flat cable according to any one of claims 1 to 9,
The insulating resin is a polyolefin resin;
The common shield is covered with a jacket;
The differential transmission extruded flat cable, wherein the jacket is a flame retardant resin or a mixed resin of polyurethane and EVA. The differential transmission extruded flat cable according to any one of claims 1 to 11,
A differential transmission extruded flat cable, wherein 0.1 wt% to 0.5 wt% of carbon black is added to the insulating resin. The differential transmission extruded flat cable according to any one of claims 1 to 12,
A differential transmission extruded flat cable, wherein a bending restricting member having a bending radius larger than a minimum bending radius that is not cut by the common shield is attached to the bent portion at at least one portion. The differential transmission extruded flat cable according to any one of claims 1 to 13,
An electrical connector connected to at least one end thereof;
A differential transmission extruded flat cable with a connector, characterized by comprising:

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