JP2010165561A - Shielded flat cable and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shielded flat cable which is ensured in grounding connection and in which mismatching of impedance is prevented, and to provide a method of manufacturing the same. <P>SOLUTION: The shielded cable 1 has a metal foil tape 6 for grounding connection adhered throughout the whole region in the longitudinal direction excluding the end on both sides of a flat cable 1a in which a plurality of conductors 2 are arranged in a row in parallel and are covered with an insulator 3, and the metal foil tape 6 has a plurality of breather holes penetrating the front and rear, and the insulator 3 is bridged by irradiation of ionizing radiation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a shielded flat cable in which a plurality of conductors are arranged in a row and integrally covered with an insulator, and a method for manufacturing the same.

  For the purpose of space saving and simple connection, flexible flat cables are used for wiring in electronic equipment and wiring of equipment moving parts. Further, since the influence of noise increases as the operating frequency of the device increases, a shielded shielded flat cable is used. Usually, conductors made of flat rectangular conductors or round conductors are arranged in a line at a predetermined interval, and the whole is integrated with an insulator made of an electrically insulating resin. Then, the outside of the insulator is covered with a common conductor to form a shield conductor, and the outside is protected with a resin jacket (see, for example, Patent Documents 1 and 2).

  A conventional shield flat cable uses a drain wire to connect a shield conductor to a connector or a ground terminal of a circuit board at a cable terminal portion. The drain wire is usually disposed inside the shield conductor covering the insulator of the shield flat cable so as to be in contact with the entire length in the longitudinal direction of the cable. In the terminal portion of the shield flat cable, the shield conductor is removed together with the jacket for connection to the terminal portion of the connector or the circuit board, but the shield conductor is grounded to the shield terminal by the drain wire.

JP-A-8-64037 JP 2003-16849 A

  The shield conductor and the drain wire are linearly contacted along the axial direction, but the contact area is less than half the surface area of the drain wire. In addition, since the contact state is obtained by winding the shield conductor or pressing the outer cover, the electrical contact may be insufficient, and the grounding reliability of the shield conductor may be reduced. In addition, since the shield conductor is removed at the cable terminal portion, there is a risk of causing an impedance mismatch in the area where the shield conductor is removed, and the shield function is degraded, which makes the transmission signal unstable. There is a problem.

  Therefore, an object of the present invention is to provide a shielded flat cable that ensures ground connection and prevents impedance mismatch.

  The shielded flat cable of the present invention capable of solving the above problems is a metal for ground connection over the entire longitudinal direction excluding the terminal on both sides of a flat cable in which a plurality of conductors are arranged in parallel and are integrally covered with an insulator. A foil tape is bonded, the metal foil tape has a plurality of air holes penetrating the front and back, and the insulator is cross-linked by irradiation with ionizing radiation.

  In the shielded flat cable of the present invention, it is preferable that the outer side of the metal foil tape is covered with a jacket.

  In the shielded flat cable of the present invention, it is preferable that the jacket is crosslinked by irradiation with ionizing radiation.

  The method for producing a shielded flat cable according to the present invention includes a plurality of conductors arranged in a parallel row, integrally covered with an insulator, and a metal foil tape for ground connection having a plurality of ventilation holes penetrating the front and back surfaces, excluding terminals. It is characterized in that both surfaces of the insulator are covered with the metal foil tape by being pasted over the entire longitudinal direction, and the insulator is crosslinked by irradiating ionizing radiation from the outside of the metal foil tape.

  The method for producing a shielded flat cable according to the present invention includes a plurality of conductors arranged in a parallel row, integrally covered with an insulator, and a metal foil tape for ground connection having a plurality of ventilation holes penetrating the front and back surfaces, excluding terminals. Covering both sides of the insulator with the metal foil tape by pasting over the entire lengthwise direction, covering the outer surface of the metal foil tape, irradiating ionizing radiation from the outer side of the jacket, The insulator is cross-linked.

  According to the present invention, since the metal foil tape for ground connection is bonded to both surfaces of the flat cable over the entire length direction excluding the terminal, the metal foil tape also has a shielding function. Therefore, by grounding the metal foil tape, the same effect as that of directly grounding the shield layer can be obtained. In addition, the metal foil tape can contact a ground bar or the like with a planar surface contact, thereby enabling reliable grounding. In addition, since the metal foil tape for ground connection is bonded throughout the longitudinal direction excluding the exposed portion of the conductor of the terminal, impedance mismatch is prevented, and signal transmission stability and reliability can be ensured.

  Moreover, since the insulator is cross-linked by irradiation with ionizing radiation, good heat resistance is imparted. In addition, since the metal foil tape has a plurality of air holes penetrating the front and back, hydrogen gas generated when the insulator is cross-linked by irradiating with ionizing radiation remains between the insulator and the metal foil tape. Released without. Thereby, the metal foil tape from the insulator is prevented from being lifted, impedance disturbance such as generation of a spike in which the impedance due to the lift is partially increased can be eliminated, and the target impedance can be obtained.

It is a perspective view which shows an example of the terminal part vicinity of the shield flat cable by this invention. It is sectional drawing which shows the cross section of the shield flat cable of FIG. It is sectional drawing which shows the other example of the shield flat cable by this invention. It is sectional drawing which shows the other example of the shield flat cable by this invention. It is a schematic plan view which shows the ventilation hole of a metal foil tape. It is a perspective view which shows the terminal part vicinity at the time of providing a jacket in the shield flat cable of FIG. It is sectional drawing of the shield flat cable which provided the jacket.

Hereinafter, an example of an embodiment of a shield flat cable and a manufacturing method for the same according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing the vicinity of a terminal of a shielded flat cable according to this embodiment, and FIG. 2 is a cross-sectional view of the shielded flat cable according to this embodiment.

  As shown in FIGS. 1 and 2, the shielded flat cable 1 according to the present embodiment has conductors 2 having a flat cross section arranged in a parallel row, and these are electrically insulated from each other by an insulator 3 made of an insulating resin. A metal foil tape 6 for ground connection is adhered to the outside thereof. The metal foil tapes 6 are attached one by one to both surfaces of the flat cable 1a covered with the insulator 3, and the metal foil tapes 6 are bonded to each other at both edges 6a in the width direction of the flat cable 1a. Further, the metal foil tape 6 is bonded over the entire longitudinal direction excluding the end of the flat cable 1a.

  As shown in FIGS. 3A and 3B, the metal foil tape 6 does not necessarily have to be bonded at both edge portions 6a. Depending on the application, this will sufficiently satisfy the shielding characteristics. Further, when the conductors G and G1 at both ends are used as ground lines in this form, there is a further shielding effect.

  The conductor 2 may be a conductor having a round cross section, or may be a stranded wire obtained by twisting a plurality of metal strands. For example, a tin-plated annealed copper foil is used as the flat conductor 2, and a conductor having a conductor thickness of 0.035 to 0.1 mm and a conductor width of 0.3 mm to 0.8 mm is used. At 25 mm, they are arranged in a line parallel to the width direction.

  As the round conductor, a single core wire or a stranded wire plated with tin or silver can be used. For example, a tin-plated annealed copper wire having an outer diameter of 0.16 mm is used. In view of flexibility, a stranded wire is preferable to a single core wire. As the stranded wire, for example, a wire in which seven conductor wires having an outer diameter of 0.06 mm are twisted (equivalent to AWG 34) is used. The conductor arrangement pitch depends on the signal voltage and the thickness of the round conductor, but is about 0.3 mm to 1.0 mm.

  Moreover, the metal foil tape 6 should just be affixed so that both surfaces of the flat cable 1a may be covered, and as shown in FIG. 4, you may wrap around by what is called a cigarette winding.

  The insulator 3 is made of polyolefin resin having a low dielectric constant in order to realize low loss, and the insulator thickness is determined by the dielectric constant of the insulating resin material and the characteristic impedance of the cable. The insulator 3 may be integrated by sandwiching the conductors 2 arranged on both sides with a resin tape having an adhesive layer from both sides, but is preferably formed by extrusion using an extruder. In the case of extrusion molding, since both surfaces of the insulator 3 can be flat surfaces without unevenness, unevenness does not occur on the adhesive surface with the metal foil tape 6, and the distributed capacity between the conductors 2 is constant. A uniform impedance can be obtained. Moreover, this insulator 3 is bridge | crosslinked by irradiation of ionizing radiation, and, thereby, favorable heat resistance is provided.

  As the metal foil tape 6, one obtained by laminating a metal foil on a resin sheet to increase the strength can be used. A metal foil tape 6 having a thickness of 0.01 mm to 0.05 mm is used, and a metal foil sheet comprising a metal foil layer 7 and a resin layer 8 obtained by laminating or vapor-depositing a metal foil such as copper or aluminum on a resin sheet. Can be used. In addition, polyethylene terephthalate (PET) etc. are used for the resin sheet base material of a metal foil sheet. The thicknesses of the metal foil layer 7 and the resin layer 8 are several μm to several tens of μm, respectively. As an example, the metal foil layer 7 is a 9 μm thick copper foil, and the resin layer 8 is a 6 μm thick PET sheet.

  The metal foil tape 6 is vertically attached so as to be in contact with both surfaces of the insulator 3 so that the metal foil layer 7 is on the inside, and is bonded via an adhesive. The adhesive may be applied to the metal foil tape 6 in advance, or may be applied to the surface of the insulator 3 before the metal foil tape 6 is attached. For example, a polyester-based adhesive can be used as the adhesive. Since the metal foil layer 7 of the metal foil tape 6 is affixed to the insulator 3, the electrostatic capacity and the external inductance through the insulator 3 between the conductor 2 and the metal foil layer 7 are kept uniform. Therefore, it is possible to prevent an impedance mismatch at this portion. In addition, the metal foil layers 7 are bonded to each other at both edges 6a in the width direction of the shield flat cable 1. If the metal foil layer 7 is exposed, the metal foil tape 6 may be peeled off or short-circuited. Therefore, at both edges in the width direction of the shielded flat cable 1, as shown in FIG. The metal foil layer 7 is preferably covered with the resin layer 8 facing the surface. As shown in FIGS. 3A, 3 </ b> B, and 4, the metal foil tape 6 may not be bonded at both edges in the cable width direction.

  It is desirable that the distance between the metal foil layer 7 of the metal foil tape 6 and the conductor 2 is kept constant, and the characteristic impedance is made uniform over the entire length of the cable. Therefore, the metal foil tape 6 does not need to be coated with an adhesive on the entire surface of the insulator 3 without any gaps. If the metal foil tape 6 is attached without floating from the insulator 3, the metal foil tape 6 is striped. For example, an adhesive may be partially applied. For example, the adhesive can be applied and adhered in various forms such as zebra, striped steel, polka dots, and lattice. Note that an adhesive is applied to the entire surface so as not to peel off at both edges 6a.

As shown in FIG. 5A, the metal foil tape 6 has a plurality of air holes 11 penetrating the front and back. These vent holes 11 are formed with a diameter of 0.1 mm and an interval of about 1 mm, for example.
In addition, as these ventilation holes 11, as shown in FIG.5 (b), you may form several slits penetrated in the front and back in zigzag form so that each may follow a longitudinal direction.

Next, the manufacturing method of said shield flat cable 1 is demonstrated.
In order to manufacture the shield flat cable 1, first, a plurality of conductors 2 are arranged in a parallel row, and these are integrally covered with an insulator 3 made of polyolefin resin.
Further, a metal foil tape 6 for ground connection, in which a plurality of ventilation holes 11 are formed in advance, is bonded and adhered to the entire outside of the insulator 3 in the longitudinal direction except for the terminals, so that both surfaces of the metal foil tape 6 are attached. Cover with.

Thereafter, ionizing radiation is applied from the outside of the metal foil tape 6 to crosslink the insulator 3 inside. Examples of ionizing radiation include electron beam irradiation and γ-ray irradiation which is cobalt irradiation.
Thereby, the insulator 3 is imparted with good heat resistance by being cross-linked by irradiation with ionizing radiation.

If it does in this way, hydrogen gas will be generated from insulator 3 which consists of polyolefin resin bridged and decomposed by irradiation of ionizing radiation.
Then, the hydrogen gas passes through the vent hole 11 of the metal foil tape 6 and is released to the outside.

  Thereby, hydrogen gas generated at the time of crosslinking and decomposition is released to the outside of the metal foil tape 6 without remaining between the insulator 3 and the metal foil tape 6. Therefore, the metal foil tape 6 can be prevented from lifting from the insulator 3, and impedance disturbance such as the occurrence of a spike (a spike of about 7Ω) that partially increases the impedance due to the lifting can be eliminated. It can be.

  And according to said manufacturing method, after performing the tandem forming which affixes the metal foil tape 6 at the time of the insulation process which integrates the conductor 2 with the insulator 3, it is suitable when irradiating the insulator 3 with ionizing radiation. is there.

The shielded flat cable 1 according to this embodiment manufactured as described above needs to be a terminal portion where the conductor 2 is exposed when connecting to a terminal portion of a connector or a circuit board. For the formation of this terminal portion, the tip portion of the metal foil tape 6 for ground connection is cut and removed using a YAG laser, and the insulator 3 is exposed. Further, the insulator 3 is cut and removed with a CO ₂ laser to expose the internal conductor 2 and connected to a terminal portion such as a connector while maintaining the arrangement pitch of the conductor 2.

When the metal foil tape 6 is cut, if the insulator 3 is transparent, the inner conductor 2 is damaged by the irradiation of the YAG laser. However, by coloring the insulator 3, the conductor 2 can be prevented from being damaged. . In addition, by adding an appropriate amount of carbon black to the insulator 3 and coloring it light black, it is possible to suppress the deterioration of the insulating characteristics of the insulator 3. Since carbon black is an electrically good conductor, if the amount of carbon black added is too large, the insulation characteristics deteriorate due to irradiation with a YAG laser. Also, when the colored dark, it is difficult to cut the insulation 3 with CO ₂ lasers. In view of these things, the preferable addition amount of carbon black is 0.1 to 0.5% by weight, particularly about 0.15% by weight. Thereby, the YAG laser does not reach the conductor 2, and the workability by the CO ₂ laser can be ensured.

In the terminal portion formed in this way, the metal foil tape 6 for ground connection is exposed, and a ground bar 9 is arranged so as to cross the width direction of the metal foil tape 6. The ground bar 9 is brought into contact. In order to make the metal foil layer 7 of the metal foil tape 6 and the ground bar 9 conductive, one or a plurality of holes are made in the resin layer 8 by a CO ₂ laser, and the metal foil layer 7 inside the hole and the ground bar 9 are grounded. The bar 9 is appropriately brought into contact with a conductive adhesive, or the end of the metal foil tape 6 in the longitudinal direction is folded back without being bonded to the insulator 3, and the ground bar is exposed to the portion where the metal foil layer 7 is exposed. 9 may be arranged. The ground bar 9 is connected to the ground terminal of the connector. Since the metal foil tape 6 and the ground bar 9 are in contact with each other, the connection state can be held and fixed, and a reliable and stable connection can be ensured. Further, the metal foil tape 6 is left to the terminal (immediately near the conductor exposed portion) for ground connection. For this reason, the electrostatic capacitance and the external inductance through the insulator 3 between the conductor 2 and the metal foil tape 6 can be kept uniform, and impedance mismatch can be prevented from occurring in this portion.

  Further, since the metal foil tape 6 covers both surfaces of the insulator 3, the metal foil tape 6 also has a shielding performance. By grounding the metal foil tape 6, the same effect as that of directly grounding the shield layer can be obtained. Therefore, the shielded flat cable 1 also has reliability against noise signals. The shielded flat cable 1 configured in this manner has a shielding function for suppressing electromagnetic radiation from the outside and suppressing electromagnetic radiation from the external device, and is used for wiring and movable parts of electronic devices in which high-frequency signals are used. It can be used for wiring.

  As shown in FIG. 6, the shield flat cable 1 may include a jacket 5 on the outside of the metal foil tape 6. As the shield flat cable 1 provided with the jacket 5, there are a sheath jacket type shown in FIG. 7A and a PET jacket type shown in FIG. 7B.

  In the shielded flat cable 1 having the sheath 5 of the sheath type, as shown in FIG. 7 (a), an aluminum-attached PET tape 21 in which an aluminum foil is laminated on a resin sheet made of polyethylene terephthalate (PET) is so-called. It is wound around the periphery by cigarette wrapping, and an extrusion jacket 22 is formed by resin extrusion coating. As the resin of the extrusion jacket 22, polyolefin (polyethylene or polypropylene), copolymers such as PVC, EVA, EEA, polyester, polyurethane, or the like can be used.

In the shielded flat cable 1 having the PET jacket type jacket 5, as shown in FIG. 7B, a copper-coated PET tape 23 in which a copper foil is laminated on a resin sheet made of polyethylene terephthalate (PET) is a so-called It is wrapped around by cigarettes.
In any of the above-described shielded flat cables 1 provided with such a jacket 5, the jacket 5 may be cut and removed by a CO ₂ laser when the terminal portion is processed.

In order to manufacture the shielded flat cable 1 provided with the jacket 5 described above, first, a plurality of conductors 2 are arranged in parallel, and these are integrally covered with an insulator 3 made of polyolefin resin.
Further, a metal foil tape 6 for ground connection, in which a plurality of ventilation holes 11 are formed in advance, is bonded and adhered to the entire outside of the insulator 3 in the longitudinal direction except for the terminals, so that both surfaces of the metal foil tape 6 are attached. Cover with.

Next, the outer cover 5 is coated on the outer periphery of the metal foil tape 6 by extrusion coating or tape winding.
The step of forming the jacket 5 may be performed immediately after the metal foil tape 6 is bonded to both surfaces of the insulator 3, or after winding the metal foil tape 6 bonded once, You may carry out in a process.
By forming the jacket 5 by extrusion molding with an extruder, the linear velocity can be increased more than the bonding of the resin tape, and the productivity is improved. When it is necessary to reduce the linear velocity in order to apply the metal foil tape 6 to the insulator 3, the metal foil tape 6 bonded together may be wound up once, and then drawn out and coated at a high linear velocity. .

  Thereafter, ionizing radiation is irradiated from the outside of the outer cover 5 to crosslink the outer cover 5 and the inner insulator 3. Thereby, the outer jacket 5 and the insulator 3 are given good heat resistance. At this time, hydrogen gas is generated from the insulator 3 made of a polyolefin resin crosslinked and decomposed by irradiation with ionizing radiation. The hydrogen gas passes through the air holes 11 of the metal foil tape 6 and is released to the outside of the metal foil tape 6.

  Thereby, hydrogen gas generated at the time of crosslinking and decomposition is released without remaining between the insulator 3 and the metal foil tape 6. Therefore, lifting of the metal foil tape 6 from the insulator 3 is prevented, impedance disturbance such as generation of a spike in which the impedance due to lifting partially increases can be eliminated, and the target impedance can be obtained.

For example, when the diameter of the vent hole 11 shown in FIG. 5A is 0.4 mm, the interval A is 1.75 mm, and the interval B is 1.5 mm, the aperture ratio is about 4.5%, and the impedance is the entire impedance. As a result, it becomes about 1.5Ω higher and no spike occurs.
Further, for example, if the diameter of the air hole 11 shown in FIG. 5A is 1.0 mm, the aperture ratio is about 30%, the impedance is increased by about 5Ω as a whole, and no spike is generated.
In these examples, the thickness of the insulator 3 is reduced to a predetermined impedance (for example, 100Ω) as much as the impedance is increased by forming the vent hole 11.

  DESCRIPTION OF SYMBOLS 1 ... Shield flat cable, 1a ... Flat cable, 2 ... Conductor, 3 ... Insulator, 5 ... Outer cover, 6 ... Metal foil sheet, 11 ... Vent

Claims (5)

  A metal foil tape for ground connection is bonded to both sides of a flat cable in which a plurality of conductors are arranged in parallel and integrally covered with an insulator over the entire longitudinal direction except for the terminal, and the metal foil tape penetrates the front and back sides. A shielded flat cable having a plurality of ventilation holes, wherein the insulator is crosslinked by irradiation with ionizing radiation. The shielded flat cable according to claim 1,
A shielded flat cable characterized in that the outer side of the metal foil tape is covered with a jacket. The shielded flat cable according to claim 2,
The shielded flat cable, wherein the jacket is crosslinked by irradiation with ionizing radiation.   A plurality of conductors are arranged in parallel in a row and covered integrally with an insulator, and a metal foil tape for ground connection having a plurality of ventilation holes penetrating the front and back is pasted over the entire region in the longitudinal direction excluding the terminal, thereby the insulator. A method for producing a shielded flat cable comprising: covering both sides with the metal foil tape, and irradiating ionizing radiation from the outside of the metal foil tape to crosslink the insulator.   A plurality of conductors are arranged in parallel in a row and covered integrally with an insulator, and a metal foil tape for ground connection having a plurality of ventilation holes penetrating the front and back is pasted over the entire region in the longitudinal direction excluding the terminal, thereby the insulator. The both sides of the metal foil tape are covered with the metal foil tape, the outer cover of the metal foil tape is covered with an outer cover, and ionizing radiation is irradiated from the outer side of the outer cover to crosslink the outer cover and the insulator. Manufacturing method of shielded flat cable.

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