JP2007234574A - Shielded cable and end processing method thereof - Google Patents

Abstract

To provide a shielded cable capable of maintaining insulation characteristics even when an outer conductor is directly melted and cut by a laser, and a method of processing a terminal thereof.
In a shielded cable 1 having one or more core wires 4 having an insulator 3 formed on the outer periphery of an inner conductor 2 and having an outer conductor 5 and an outer skin 6 sequentially formed on the outer periphery of the core wire 4, The insulator 3 is a shielded cable in which a metal component is added to a fluororesin and a color pigment is kneaded.
[Selection] Figure 1

Description

  The present invention relates to a shielded cable having one or two or more core wires each having an insulator formed on the outer periphery of an inner conductor, and an outer conductor and an outer shell being sequentially formed on the outer periphery of the core wires, and a method for processing the end thereof.

  In recent years, with the spread of notebook computers, mobile phones, small video cameras, etc., there is a demand for higher quality as well as smaller information communication devices. These devices use thin electric wires (cables) in which an inner insulator, an outer conductor, and an outer skin are sequentially formed on the outer periphery of the inner conductor.

  Since these cables have a very thin outer diameter of 1 mm or less, a method using laser processing (for example, Patent Document 1) is known for terminal processing. As shown in the cross-sectional view of FIG. 5, the shielded cable 51 of Patent Document 1 sequentially forms an inner insulator 53, a coating layer 54 with excellent heat resistance, an outer conductor 55, and an outer shell 56 on the outer periphery of the inner conductor 52. It is what.

In the terminal processing method of the shielded cable 51, first, the outer skin 56 is cut using a CO ₂ laser and peeled off from the external conductor 55. Thereafter, when the outer conductor 55 is cut with a laser, the irradiation time and the like are controlled so that the laser beam does not reach the inner coating layer 54, and the thermal energy of the laser is applied to the inner insulator 53 by the coating layer 54 having excellent heat resistance. This is a method for avoiding the occurrence of an electrical short circuit by suppressing the noise from spreading to the outside.

Further, as a method for cutting the outer conductor 55, a method using a YAG laser instead of a CO ₂ laser is also performed.

Japanese Patent Laid-Open No. 11-144533 JP-A-11-121501 JP 2004-192815 A JP 2002-25357 A JP 2005-251522 A

  However, in the shielded cable 51 of Patent Document 1, since the cable structure is multi-layered because of the covering layer 54, the shielded cable 51 itself is expensive, and the terminal processing method is also expensive.

  Further, the method of cutting the outer conductor 55 with the YAG laser without disposing the covering layer 54 also affects the inner insulator 53 of the inner conductor 52 due to the heat of the YAG laser, resulting in a decrease in insulation reliability. There was a risk of it. Normally, the internal insulator 53 contains pigments of each color and is colored for identification. However, in any insulator color, damage to the insulator due to the YAG laser during terminal processing is unavoidable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a shielded cable that can maintain insulation characteristics even when an outer conductor is melted and cut directly by a laser, and a method for processing a terminal thereof.

  The present invention has been devised to achieve the above object, and the invention of claim 1 has one or more core wires in which an insulator is formed on the outer periphery of the inner conductor, and the outer periphery of the core wires. In a shielded cable in which an outer conductor and an outer skin are sequentially formed, the inner insulator is a shielded cable in which a metal component is added to a fluororesin and a color pigment is kneaded.

The invention according to claim 2 is the shielded cable according to claim 1, wherein the metal component is TiO ₂ and 0.01 to 5.0 wt% of TiO ₂ is added.

  According to a third aspect of the present invention, the fluororesin is a tetrafluoroethylene / perfluoropropyl vinyl ether copolymer, a tetrafluoroethylene / hexafluoropropylene copolymer, or an ethylene / tetrafluoroethylene copolymer. A shielded cable according to claim 1 or 2.

  A fourth aspect of the present invention is the shielded cable according to any one of the first to third aspects, wherein a coating thickness of the insulator is 60 μm or less.

  The invention according to claim 5 is the shielded cable according to any one of claims 1 to 4, wherein the insulator has a transmittance of 5 to 60% at a YAG laser beam wavelength (1064 nm).

  A sixth aspect of the present invention is the shielded cable according to any one of the first to fourth aspects, wherein the insulator has a transmittance of 8 to 40% at a YAG laser beam wavelength (1064 nm).

  The invention according to claim 7 is the shielded cable according to any one of claims 1 to 6, wherein the insulator has an absorptance of 15% or less at a YAG laser beam wavelength (1064 nm).

  The invention of claim 8 is a shielded cable in which a plurality of shielded cables according to any one of claims 1 to 7 are arranged in a flat shape at a predetermined pitch.

  According to a ninth aspect of the present invention, the outer conductor is exposed by peeling off a predetermined length of the outer cover of the shielded cable according to any one of the first to eighth aspects, and the exposed outer conductor is cut with a YAG laser. Then, the outer conductor is peeled off to expose the insulator, and the exposed insulator is peeled off to expose the inner conductor.

  According to the present invention, regardless of which insulator color is selected, cable end processing is possible using a YAG laser, and insulation damage at that time is greatly reduced compared to the case where a conventional pigment is used. it can. Further, the inner conductor is not affected at all by the heat of the YAG laser. Therefore, highly reliable terminal processing is possible.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a shielded cable showing a preferred first embodiment of the present invention.

  As shown in FIG. 1, the shielded cable 1 according to the first embodiment has one core wire 4 in which an inner insulator 3 is formed on the outer periphery of the inner conductor 2, and the outer conductor 5 on the outer periphery of the core wire 4. The outer skin 6 is formed sequentially and has the same structure as a coaxial cable.

  The inner conductor 2 is formed by twisting a plurality of strands (six in FIG. 1). The outer conductor 5 is configured by horizontally winding a plurality of wires around the outer periphery of the inner insulator 3.

  Now, the pigment kneaded in the internal insulator 3 must have a property that does not allow the internal conductor 2 to transmit laser light. For this reason, the internal insulator 3 needs to absorb laser light or reflect and scatter it. . Here, carbon black is one option because it has excellent absorption characteristics. However, if the absorption in the internal insulator 3 is large, the optical power of the laser light changes to thermal energy, leading to damage to the internal insulator 3.

  Regarding the relationship between the light absorption characteristics of the internal insulator 3 having a thickness of 50 μm and the damage of the internal insulator 3 itself, it is generally about 20% when the internal insulator 3 is irradiated with laser light, and about 10% in some cases. It has been found that significant damage occurs to the internal insulator 3 due to light absorption. For this reason, other pigment systems should avoid compositions that increase light absorption.

On the other hand, TiO ₂ is a pigment having the property of scattering light. When the pigment is kneaded in an appropriate amount, both the inner insulator 3 and the inner conductor 2 can be less damaged.

In consideration of the above points, in the present embodiment, as the internal insulator 3, TiO ₂ as a metal component is added to the fluororesin in an amount of 0.01 to 5.0 wt%, preferably 0.05 to 5.0 wt%. Preferably, 0.01 to 1.0 wt% is added and a color pigment is kneaded.

TiO ₂ is a white fine powder, and is used as a white pigment because it is chemically and physically stable and harmless. This TiO ₂ has a large refractive index, and has a property of well scattering (reflecting) laser light having a visible light or YAG laser wavelength of 1064 nm.

The reason why 0.01 to 5.0 wt% of TiO ₂ is contained as the pigment of the internal insulator 3 is that the reflection scattering of the laser light at the internal insulator 3 is increased and the amount of laser light reaching the internal conductor 2 is reduced. There is to do. Thereby, as will be described later, damage to the internal insulator 3 and the internal conductor 2 is greatly suppressed.

  The internal insulator 3 is color-coded in several colors for each core wire (signal line) 4 so that the core wire 4 can be identified visually. Therefore, the color pigment is not particularly limited in color, and color pigments of each color such as blue, green, red, yellow, brown, orange, purple, and gray are used.

  As the fluororesin, tetrafluoroethylene / perfluoropropyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer, or ethylene / tetrafluoroethylene copolymer is used. The reason for using PFA for the internal insulator 3 is to place importance on heat resistance and to suppress the possibility of the internal insulator 3 being heated and damaged by the laser beam.

  The coating thickness of the internal insulator 3 is preferably 60 μm or less. The reason for setting the thickness of the internal insulator 3 to 60 μm or less is to suppress the absorption of the laser beam by the internal insulator 3 and thereby suppress the insulator damage.

Further, the internal insulator 3 may have a transmittance at a YAG laser beam wavelength (1064 nm) of 5 to 60%, preferably 8 to 50%, more preferably 8 to 40%, and further preferably 10 to 30%. The reason for the laser light transmittance within the insulator 3 5 to 60 percent, when the inner insulator 3 so transmittance is less than 5% resulting in a number of TiO ₂ containing, containing TiO ₂ It is because there is too much quantity and the moldability of a cable deteriorates. Also, when the inner insulator 3 as the transmittance is more than 60% resulting in less TiO ₂ containing a laser beam transmittance becomes larger content of TiO ₂ is too small, damage to the inner conductor 3 This is because it occurs.

  The internal insulator 3 may have an absorptivity at a YAG laser beam wavelength (1064 nm) of 15% or less, preferably 10% or less. The reason why the laser light absorption rate in the internal insulator 3 is set to 15% or less is to suppress laser light energy absorption in the internal insulator 3 and thereby suppress damage to the insulator.

  Among these, the internal insulator 3 is preferably configured such that the transmittance at a YAG laser beam wavelength (1064 nm) is 10 to 50% and the absorptance is 10% or less.

  The transmittance and the absorptivity for the internal insulator 3 according to the present invention can be obtained by the following measuring method. The internal insulator 3 is irradiated with a YAG laser beam wavelength (1064 nm), and the amount of light reflected at that time and the amount of light transmitted through the sample to be measured are measured by a spectrometer. Further, since light scattering occurs at that time, a hemispherical sensor (integrator) is used so that the scattered light can be measured. The transmittance and the absorptivity are measured by the light quantity obtained by the above method and the following formulas (1) and (2).

(Transmittance) = (Transmitted light amount) / (Irradiated light amount) × 100 (%) (1)
(Absorptance) = [(irradiation light amount) − {(transmitted light amount) + (reflected light amount)}] / (irradiation light amount) × 100 (%) (2)
Next, the terminal processing method of the shielded cable 1 will be described.

  First, a shielded cable 1 is prepared (FIG. 2 (a)). The outer skin 6 of the end portion of the shielded cable is peeled off by a predetermined length to expose the outer conductor 5 (FIG. 2B). The exposed external conductor 5 is irradiated with a YAG laser to make a cut (one-dot chain line in FIG. 2C) (FIG. 2C). The tip of the cut outer conductor 5 is peeled off to expose the internal insulator 3 (FIG. 2D). A notch is cut into the exposed tip of the internal insulator 3 with a tool or the like, and the internal insulator 3 is peeled off to expose the internal conductor 3 (FIG. 2 (e)). Further, the inner conductor 2 is connected to the connection terminal on the other side to be connected, and the outer conductor 5 is connected to the ground to finish the terminal processing.

  The operation of the first embodiment will be described.

In the shielded cable 1, 0.01 to 5.0 wt%, preferably 0.05 to 5.0 wt%, more preferably 0.01 to 1.0 wt% of TiO ₂ is added to the fluororesin as the internal insulator 3. And a color pigment is kneaded. That is, TiO ₂ is kneaded with a color pigment for coloring the internal insulator 3.

For this reason, even if the external conductor 5 is directly irradiated with a laser during terminal processing to melt and cut the external conductor 5, the laser light is reflected and scattered by the surface of the internal insulator 3 due to TiO ₂ contained in the internal insulator 3. Therefore, insulation characteristics can be maintained and the reliability of the shielded cable 1 is high.

  In addition, the shielded cable 1 can be processed at the end of the shielded cable 1 using a YAG laser, regardless of which insulator color is selected as the internal insulator 3, and the insulation damage at that time can be reduced by the conventional ordinary method. This can be greatly reduced as compared with the case of using a pigment. Further, the inner conductor 2 is not affected at all by the heat of the YAG laser. Therefore, if the shielded cable 1 is used, highly reliable terminal processing is possible.

  Unlike the conventional shielded cable 51 of FIG. 5, the shielded cable 1 does not require the coating layer 54 having excellent heat resistance, so the cable itself is lower in cost than the shielded cable 51, and the terminal processing is also performed at a lower cost. it can.

Here, in the case where the thickness of the internal insulator 3 is 50 μm, a laser irradiation experiment is performed on each shielded cable 1 in which the internal insulator 3 is colored in blue, green, red, yellow, brown, orange, purple, and gray. Went. As a result, for any color system, TiO ₂ was added to the internal insulator 3 in an amount of 0.01 to 5.0 wt%, preferably 0.05 to 5.0 wt%, more preferably 0.01 to 1.0 wt%. It was confirmed that the damage to the internal insulator 3 was very small, and the internal conductor 2 was not damaged at all.

In the first embodiment, the addition of TiO ₂ in the fluorine resin, have been described in the example which contains TiO ₂ as the metal component within the insulator 3, as a metal component to be contained in the inner insulator 3, In addition, there are Au, Ag, Cu and the like. This is because the reflectance of light is as high as 90% for Cu and 97% for Au or Ag. In this case, although expensive, a laser beam reflecting effect can be obtained that is equivalent to that of TiO ₂ .

  Further, not only the single-core shielded cable 1 but also a multi-core cable such as the shielded cable 31 according to the second embodiment shown in FIG. 3 is possible. The shielded cable 31 is formed by twisting a plurality of core wires 4 (four in FIG. 3) and forming an outer conductor 5 and an outer skin 6 in order on the outer periphery of the plurality of core wires 4. Also with this shielded cable 31, a highly reliable terminal connection is possible as in the case of the single-core shielded cable 1 within a range where colors can be identified.

  Further, like the shielded cable 41 of the third embodiment shown in FIG. 4, a plurality of shielded cables 1 are arranged in parallel in a flat shape at a predetermined pitch, and both surfaces of the plurality of shielded cables 1 arranged in parallel are insulated. What was pinched | interposed with the films 42 and 42 may be used.

(Examples 1-4)
On the outer periphery of the inner conductor 2, TiO ₂ as a metal component was added to the fluororesin in various amounts within a range of 0.05 to 5.0 wt%, and an inner insulator 3 was formed by kneading a color pigment. The shielded cable 1 shown in FIG. 1 was prepared by sequentially forming the outer conductor 5 and the outer skin 6 on the outer periphery of the core wire 4, and Examples 1 to 4 were obtained.
(Comparative Examples 1-3)
In the same manner as in Examples 1 to 4, 0.005, 6.0, 7.0 wt% of TiO ₂ as a metal component is added to the fluororesin on the outer periphery of the inner conductor 2, and a color pigment is kneaded. One core wire having an internal insulator was formed, and the outer conductor 5 and the outer skin 6 were sequentially formed on the outer periphery of the core wire to produce a shielded cable.

  Table 1 shows the results obtained by various evaluations and studies on the shielded cable 1 of Examples 1 to 4 and the shielded cables of Comparative Examples 1 to 3. The transmittance (%) is a value at the YAG laser beam wavelength (1064 nm), and the absorptance (%) was obtained by the formulas (1) and (2).

  The judgment items and criteria in Table 1 are as follows. Insulator damage depends on the result of dielectric breakdown test. A predetermined voltage was applied between the inner conductor and the outer conductor of each shielded cable. Conductor damage is observed by magnifying the inner conductor at a magnification of about 200 times, ○ if there is no flaw, △ if there is a change in hue but not flaw, × if there is an obvious flaw like scratch It was. Formability was evaluated as “◯” when the outer shell was processed without any problem, “Δ” when the thickness was uneven in the circumferential direction, and “X” when the thickness was uneven in the longitudinal direction.

As shown in Table 1, in Examples 1 to 4, since the content of TiO _{2 in} the internal insulator 3 is in the range of 0.05 to 5.0 wt%, the transmittance is 10 to 60%, and the insulation Both body damage and conductor damage are acceptable and formability is good.

On the other hand, in Comparative Example 1, the content of TiO _{2 in} the internal insulator is as low as 0.005 wt%, so that the conductor is damaged. In Comparative Examples 2 and 3, the content of TiO _{2 in} the internal insulator is 6.0. , 7.0 wt%, so the moldability is poor.

It is a cross-sectional view of a shielded cable showing a preferred embodiment of the present invention. 2 (a) to 2 (e) are schematic views for explaining a method of processing the end of the shielded cable shown in FIG. It is a cross-sectional view of a shielded cable showing a second embodiment of the present invention. It is a cross-sectional view of the flat shield cable which shows the 3rd Embodiment of this invention. It is a cross-sectional view of a conventional shielded cable.

Explanation of symbols

1 Shielded cable 2 Inner conductor 3 Inner insulator 4 Core wire 5 Outer conductor 6 Outer sheath

Claims (9)

  In a shielded cable that has one or more core wires with an insulator formed on the outer periphery of the inner conductor, and the outer conductor and outer sheath are formed on the outer periphery of the core wire in sequence, the inner insulator adds a metal component to the fluororesin. Shielded cable characterized by kneading color pigments. The shielded cable according to claim 1, wherein the metal component is TiO ₂ and 0.01 to 5.0 wt% of TiO ₂ is added.   3. The fluororesin is a tetrafluoroethylene / perfluoropropyl vinyl ether copolymer, a tetrafluoroethylene / hexafluoropropylene copolymer, or an ethylene / tetrafluoroethylene copolymer. Shielded cable.   The shield cable according to any one of claims 1 to 3, wherein a coating thickness of the insulator is 60 µm or less.   The shield cable according to any one of claims 1 to 4, wherein the insulator has a transmittance of 5 to 60% at a YAG laser beam wavelength (1064 nm).   The shield cable according to any one of claims 1 to 4, wherein the insulator has a transmittance of 8 to 40% at a YAG laser beam wavelength (1064 nm).   The shield cable according to claim 1, wherein the insulator has an absorptance of 15% or less at a YAG laser beam wavelength (1064 nm).   A shielded cable comprising a plurality of shielded cables according to any one of claims 1 to 7 arranged in a flat shape at a predetermined pitch. An outer skin of the end portion of the shielded cable according to any one of claims 1 to 8 is peeled off to a predetermined length to expose the outer conductor, and the exposed outer conductor is cut with a YAG laser to peel off the outer conductor. A method for processing a terminal of a shielded cable, wherein the insulator is exposed, and the exposed insulator is peeled off to expose the inner conductor.

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