JP2016100048A - Braided wire and shielded electric wire - Google Patents

Abstract

A braided wire having excellent shielding performance and corrosion resistance and a shielded electric wire using the same are provided.
A braided wire is formed by knitting a plurality of strands 10 into a cylindrical shape. The element wire 10 includes an aluminum wire 101, a first Ni plating film 102, a second Ni plating film 103, and a Sn plating film 104. The first Ni plating film 102 is formed on the surface of the aluminum wire 101. The second Ni plating film 103 contains S and is formed on the first Ni plating film 102. The Sn plating film 104 is formed on the second Ni plating film 103.
[Selection] Figure 2

Description

  The present invention relates to a braided wire and a shielded electric wire using the same.

  For example, shielded wires are used in places where countermeasures against electromagnetic noise are required in automobiles and electrical equipment. The shielded electric wire has a core part that transmits electrical signals and the like, and a shield layer that covers the outer periphery of the core part. Intrusion of electromagnetic noise from the outside to the core part, and electromagnetic noise from the core part to the outside The radiation can be suppressed by the shield layer. The core part has one or two or more covered electric wires. As the shield layer, for example, a braided wire formed by braiding metal strands is often used.

  As a metal wire used for the braided wire, an Sn-plated copper wire in which an Sn (tin) plating film is provided on the surface of the copper wire is frequently used from the viewpoint of conductivity and workability (for example, Patent Document 1). ). In recent years, it has been proposed to use aluminum wires made of Al (aluminum) and Al alloys, which are lighter and cheaper than Cu (copper) and Cu alloys, as metal wires in order to reduce the overall weight and cost of shielded wires. (For example, Patent Document 2).

JP 2006-164754 A Japanese Patent Laid-Open No. 2004-60007

When an aluminum wire is used as a metal strand, a non-conductor Al ₂ O ₃ film is inevitably formed on the surface of the aluminum wire. Due to the presence of the Al ₂ O ₃ film, the aluminum wire has an increased AC resistance in a high frequency region where the influence of the skin effect becomes significant. Therefore, the braided wire using the aluminum wire as the metal strand has a problem that the shielding performance against electromagnetic noise in the high frequency region is lowered.

  The above problem can be suppressed, for example, by providing a highly conductive Sn (tin) plating film on the surface of the aluminum wire. Further, by providing a Ni (nickel) plating film between the aluminum wire and the Sn plating film, the adhesion of the Sn plating film can be improved, compared with the case where the Sn plating film is provided directly on the surface of the aluminum wire. Thus, peeling of the Sn plating film and the like can be suppressed.

  However, the metal element wire in which the Ni plating film and the Sn plating film are sequentially laminated on the surface of the aluminum wire as described above has the following problems. That is, when the Sn plating film is damaged for some reason, the Ni plating film may be exposed on the surface of the metal strand. In this state, when moisture or the like enters from the damaged portion of the Sn plating film, the Sn plating film and the Ni plating film form a local battery, and different metal contact corrosion occurs. As a result, electrochemically base Ni is preferentially corroded compared to Sn, and corrosion holes may be formed in the Ni plating film. Moreover, when corrosion progresses, depending on the case, the corrosion hole may reach the surface of the aluminum wire, and the aluminum wire may be corroded.

  As described above, the metal wire in which the Ni plating film and the Sn plating film are sequentially laminated on the surface of the aluminum wire may have a reduced corrosion resistance when the Sn plating film is damaged. Therefore, in order to use the aluminum wire for the braided wire, it is necessary to improve the corrosion resistance while ensuring the shielding performance equivalent to or higher than that of the conventional Sn-plated copper wire.

  This invention is made | formed in view of this background, and intends to provide the braided wire which has the outstanding shielding performance and corrosion resistance, and a shielded electric wire using the same.

One aspect of the present invention is a braided wire in which a plurality of strands are knitted into a cylindrical shape,
The strand is an aluminum wire,
A first Ni plating film formed on the surface of the aluminum wire;
A second Ni plating film formed on the first Ni plating film and containing S;
The braided wire has an Sn plating film formed on the second Ni plating film.

Another aspect of the present invention is a braided wire of the above aspect,
A shielded electric wire having a covered electric wire arranged in a tube of the braided wire.

  The braided wire is composed of the strands having a multilayer structure in which the first Ni plating film, the second Ni plating film, and the Sn plating film are sequentially laminated on the surface of an aluminum wire. Since the Sn plating film having high conductivity exists on the surface of the element wire, the AC resistance in the high frequency band can be reduced. Therefore, the braided wire has improved shielding performance against high-frequency noise, and can easily ensure shielding performance equivalent to or higher than that of a conventional Sn-plated copper wire.

  Further, the second Ni plating film contains S (sulfur), and therefore becomes electrochemically lower than the first Ni plating film. Therefore, the second Ni plating film has the property of being most easily corroded among the plating films formed on the surface of the aluminum wire. By providing the second Ni plating film between the first Ni plating film and the Sn plating film, the element wire can function as the sacrificial anticorrosive material.

  That is, for example, when the Sn plating film is damaged and the second Ni plating film is exposed, the second Ni plating film is preferentially corroded by dissimilar metal contact corrosion. Therefore, when corrosion progresses, corrosion holes are formed in the second Ni plating film. Even when the corrosion further proceeds and the corrosion holes reach the first Ni plating film, the second Ni plating film is preferentially corroded over the first Ni plating film, so that the inside of the strand Can slow the progress of corrosion.

  Thus, the said strand can make the said 2Ni plating film function as a sacrificial anti-corrosion material by having the said specific multilayer structure, and can improve corrosion resistance. Therefore, the braided wire has excellent corrosion resistance.

  As described above, the braided wire has excellent shielding performance and corrosion resistance. Further, the shielded wire using the braided wire has shield performance and corrosion resistance equal to or higher than those of the conventional one, and can be easily reduced in weight and cost as compared with the conventional one.

Sectional drawing of the shield electric wire in an Example. Sectional drawing of the strand which comprises the braided wire in an Example. The partial cross section figure of the strand which gave the surface damage | wound for the corrosion test in an Example. Explanatory drawing of the noise measuring apparatus in an Example. Sectional drawing of the strand which comprises the braided wire in a comparative example.

  In the braided wire, as the aluminum wire, a wire made of pure Al or a conventionally known Al alloy can be used. The material of the said aluminum wire can be suitably selected according to the intensity | strength characteristic etc. which are requested | required.

  The first Ni plating film is a plating film made of Ni and inevitable impurities. The first Ni plating film preferably has a thickness of 0.1 to 1.0 μm. If the film thickness of the first Ni plating film is excessively thin, it is conceivable that the scratches easily reach the aluminum wires when the strands are scratched for some reason. On the other hand, if the thickness of the first Ni plating film becomes excessively thick, the manufacturing cost increases. Therefore, it is preferable that the film thickness of the first Ni plating film is within the specific range from the viewpoint of achieving both durability against scratches and manufacturing costs.

  The second Ni plating film is a plating film containing S, with the balance being Ni and inevitable impurities. The second Ni plating film preferably contains 0.05 to 0.5 mass% of S. In this case, since the second Ni plating film effectively functions as a sacrificial anticorrosive material, the corrosion resistance of the braided wire can be further improved.

  When the content of S in the second Ni plating film is less than 0.05% by mass, the effect of S becomes insufficient, and the sacrificial anticorrosive effect of the second Ni plating film may be reduced. Therefore, there is a possibility that the effect of delaying the progress of corrosion inside the strands may be insufficient. On the other hand, if the content of S in the second Ni plating film exceeds 0.5% by mass, the conductivity of the second Ni plating film may be reduced, and consequently the shielding performance of the braided wire may be reduced. is there.

  The second Ni plating film preferably has a thickness of 0.1 to 1 μm. In this case, similarly to the case of the first Ni plating film described above, both the durability against scratches and the manufacturing cost can be achieved.

  The Sn plating film is a plating film made of Sn and inevitable impurities. Although the thickness of Sn plating film is not specifically limited, Usually, it is about 0.1-1 micrometer. In this case, the braided wire has excellent shielding performance and durability. Therefore, the braided wire can suppress wear of the Sn plating film and maintain excellent shielding performance over a long period of time even in applications used under severe usage environments such as automotive wire harnesses. it can.

  The shielded wire using the braided wire may be configured as a power line that transmits a relatively large current such as operating power, or may be configured as a signal line that transmits a relatively small current such as a control signal. May be. Moreover, the said shielded electric wire may be comprised as a single core shielded electric wire which has one said covered electric wire, and may be comprised as a multi-core shielded electric wire which has two or more said covered electric wires.

  The said covered electric wire has a conductor and the insulating material which coat | covers the circumference | surroundings of a conductor. As a conductor used for a covered electric wire, for example, a metal wire having excellent electrical conductivity such as a copper wire, a copper alloy wire, a Sn-plated copper wire, an aluminum wire, and an aluminum alloy wire can be used. The conductor may be composed of a single metal wire, or may be composed of a stranded wire in which a large number of metal wires are twisted together.

  Moreover, as an insulating material used for the said covered electric wire, a conventionally well-known material can be used as an insulating material for electric wires. From the viewpoints of insulation and manufacturability, a crosslinked polyethylene resin or a crosslinked polyvinyl chloride resin is often used as the insulating material.

(Example)
Examples of the braided wire and a shielded wire using the braided wire will be described with reference to the drawings. As shown in FIG. 1, the shielded electric wire 2 has a braided wire 1 in which a plurality of strands 10 are knitted into a cylindrical shape, and a covered electric wire 21 inserted into the cylinder of the braided wire 1.

  The strand 10 which comprises the braided wire 1 has the aluminum wire 101, the 1st Ni plating film 102, the 2nd Ni plating film 103, and the Sn plating film 104, as shown in FIG. The first Ni plating film 102 is formed on the surface of the aluminum wire 101. The second Ni plating film 103 contains S and is formed on the first Ni plating film 102. The Sn plating film 104 is formed on the second Ni plating film 103. The details will be described below.

  As shown in FIG. 1, the braided wire 1 of the present example is formed with a strand bundle 11 formed by arranging three strands 10 to each other, and has 24 strand bundles 11. Although not shown in the drawing, each strand bundle 11 is knitted while being wound around the outer periphery 22 of the covered electric wire 21 in a spiral shape. In this example, the twisting pitch of the wire bundle 11, that is, the distance that the wire bundle 11 travels in the longitudinal direction of the covered wire 21 when the wire bundle 11 makes a spiral turn around the outer periphery 22 of the covered wire 21 is 20 mm.

  As shown in FIG. 2, the strand 10 constituting the braided wire 1 has a three-layer structure in which a first Ni plating film 102, a second Ni plating film 103, and an Sn plating film 104 are sequentially laminated on the surface of an aluminum wire 101. Have.

  The diameter of the aluminum wire 101 is 0.23 mm. The first Ni plating film 102 is made of Ni and inevitable impurities and has a thickness of 1 μm. The second Ni plating film 103 contains 0.5 mass% of S, and the remainder has chemical components composed of Ni and inevitable impurities. The film thickness of the second Ni plating film 103 is 1 μm. The Sn plating film 104 is composed of Sn and inevitable impurities and has a thickness of 1 μm. Although not shown in the drawing, a natural oxide film of Sn exists on the surface of the Sn plating film 104.

As shown in FIG. 1, the covered electric wire 21 inserted into the tube of the braided wire 1 has a conductor 211 and an insulating material 212 covered around the conductor 211. The conductor 211 in this example is a copper stranded wire having a cross-sectional area of 3 mm ² .

  In this example, the shielded wire 2 configured as described above was used, and the corrosion resistance was evaluated by the following method.

<Corrosion test>
First, a knife was brought into contact with the outer peripheral surface 20 (see FIG. 1) of the shielded electric wire 2, and the knife was rotated once along the circumferential direction. As a result, as shown in FIG. 3, scratches 105 having a depth that reaches at least the second Ni plating film 103 and does not reach the aluminum wire 101 are made on the surface of the element wire 10. Next, the shielded electric wire 2 was immersed in 10% salt water for 72 hours. After 72 hours, the shielded electric wire 2 was taken out from the salt water and washed and dried. After drying, the damaged part was visually observed.

  As a result of performing the corrosion test by the above method, it was confirmed that the appearance of changes such as discoloration was not observed in the damaged part and its vicinity compared to before the corrosion test.

<Shield performance evaluation>
A shielded electric wire 2 having a length of 1000 mm was prepared, and a corrosion test was performed according to the above procedure. After the shielded electric wire 2 was dried, the shielding performance was measured by the absorption clamp method. As shown in FIG. 4, the measuring device 3 used in the absorption clamp method includes a spectrum analyzer 31, a tracking generator 32, a pair of shield boxes 33 (33 a and 33 b), an absorption clamp 34, and a termination resistor 35. Each shield box 33 is connected to ground. The absorption clamp 34 is disposed between the pair of shield boxes 33. The termination resistor 35 is provided in one shield box 33a of the pair of shield boxes 33, and is grounded through the one shield box 33a. The spectrum analyzer 31 is connected to an absorption clamp 34, and is configured so that a signal received by the absorption clamp 34 can be measured. The absorption clamp 34 in this example is “KT-10” manufactured by Kyoritsu Electronics Co., Ltd., and the spectrum analyzer 31 is “E4402B” manufactured by Agilent.

  The shielded electric wire 2 was attached according to the following procedure. First, the shielded electric wire 2 was passed inside the absorption clamp 34 and both ends were fixed in the shield box 33. Next, both ends of the braided wire 1 were connected to each shield box 33, and the braided wire 1 was grounded via the shield box 33. Next, the conductor 211 of the shielded electric wire 2 inserted into one shield box 33 a was connected to the termination resistor 35 and grounded via the termination resistor 35. Thereafter, the conductor 211 of the shielded electric wire 2 inserted into the other shield box 33 b was connected to the tracking generator 32.

  As shown in FIG. 3, after the shielded electric wire 2 was attached to the measuring device 3, a high frequency signal of 10 MHz generated from the tracking generator 32 was input to the conductor 211. Then, the high frequency signal leaked to the outside of the shielded electric wire 2 was received by the absorption clamp 34, and the magnitude of the high frequency signal leaked by the spectrum analyzer 31 was measured. Thereafter, the ratio of the leaked high-frequency signal to the magnitude of the input high-frequency signal was calculated, and this was used as the induction noise amount (dB).

  In this example, three shielded electric wires 2 subjected to a corrosion test were prepared, and the shielding performance was evaluated for each. As a result, the amount of induced noise was 56 dB. The amount of induction noise is equivalent to that of a conventional Sn-plated copper wire. From the above results, it can be understood that the braided wire 1 of this example has excellent shielding performance.

(Comparative example)
This example is an example of a shielded electric wire using a strand 40 that does not have the second Ni plating film 103. As shown in FIG. 5, the strand 40 used for the braided wire of this example is obtained by sequentially laminating a Ni plating film 402 made of Ni and inevitable impurities and a Sn plating film 403 on the surface of an aluminum wire 401. It has a layer structure. Although not shown in the drawing, the shielded electric wire of this example has the same configuration as that of Example 1 except that the above-described elemental wire 40 is used instead of the elemental wire 10 of the example. Of the reference numerals used in FIG. 5, the same reference numerals as those used in the embodiment denote the same components as in the embodiment unless otherwise specified.

  When the corrosion test was performed by the same method as the Example using the shielded electric wire of this example, it was confirmed that the damaged part and its vicinity were discolored compared to before the corrosion test.

  Moreover, shield performance evaluation was performed by the same method as an Example using the shielded electric wire of this example. As a result, the induction noise amount of the shielded electric wire was 50 dB at the maximum and 56 dB at the minimum.

  From the results of the examples and comparative examples, the braided wire 1 composed of the strand 10 having a three-layer structure in which the first Ni plating film 102, the second Ni plating film 103, and the Sn plating film 104 are sequentially laminated on the aluminum wire 101 is Even when the Sn plating film 104 is scratched, it can be understood that discoloration and shield performance are not easily caused by the corrosion test and have excellent corrosion resistance.

DESCRIPTION OF SYMBOLS 1 Braided wire 10 Strand 101 Aluminum wire 102 1st Ni plating film 103 2nd Ni plating film 104 Sn plating film

Claims (5)

A braided wire formed by knitting a plurality of strands into a cylindrical shape,
The strand is an aluminum wire,
A first Ni plating film formed on the surface of the aluminum wire;
A second Ni plating film formed on the first Ni plating film and containing S;
A braided wire having an Sn plating film formed on the second Ni plating film.   The braided wire according to claim 1, wherein the second Ni plating film contains 0.05 to 0.5 mass% of S.   The braided wire according to claim 1 or 2, wherein the second Ni plating film has a thickness of 0.1 to 1.0 µm.   The braided wire according to any one of claims 1 to 3, wherein the first Ni plating film has a thickness of 0.1 to 1.0 µm. The braided wire according to any one of claims 1 to 4,
A shielded electric wire having a covered electric wire inserted into a tube of the braided wire.

Images