Conductive member and production method thereof

Abstract

To provide a production method for obtaining a conductive member coated with a copper plating layer having high conductivity or high purity while using various core materials and soluble copper base materials as raw materials, and the conductive member obtained by the method.SOLUTION: The present invention is a conductive member having a core material, and a copper plating layer covering an outer peripheral surface of the core material. The core material has, for example, a conductivity of 90% IACS or less. The copper plating layer has, for example, a conductivity of 95% IACS or more. The copper plating layer has, for example, a copper purity of 99.9 mass% or more relative to the entire layer. The core material is made of, for example, an aluminum base material, an iron base material, or a copper base material. A soluble copper base material serving as an anode used in a plating process may be, for example, a scrap material or a recycled material having a copper purity of about 40 to 85 mass%.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a conductive member and the like.

Background Art

[0002] Conductors that make up wiring wires, coil winding wires, etc. usually consist entirely of pure copper (oxygen-free copper, tough pitch copper, phosphorus-deoxidized copper, etc.). However, a coated wire in which the outer peripheral surface of a core wire made of a certain metal is coated with another metal has also been proposed, and related descriptions can be found in the following patent documents.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Documents 1 and 2 propose copper-coated aluminum wires that can achieve weight reduction of the conductor. The copper-coated aluminum wire is produced by a raw material by a tape cladding method in which the longitudinal ends of a copper tape covering an aluminum wire are welded, or a pipe cladding method in which an aluminum wire is inserted into a copper pipe. The coated wire is obtained by further drawing and heat-treating the raw material to bring the aluminum wire as the core material into close contact with the coated copper on its outer peripheral surface. The coated wire premised on drawing and the like has poor freedom in form and is difficult to adjust the thickness of the coated copper, so its applications are limited. In addition, there is also a possibility that an intermetallic compound that can reduce the conductivity may be formed between the aluminum wire and the coated copper during the processing or heat treatment. Furthermore, since the copper tape and the copper pipe are obtained by processing high-purity copper itself, copper resources such as low-purity copper cannot be effectively utilized in the above-described cladding method.

[0005] Patent Document 3 proposes a wire having a sheath layer in which the outer peripheral surface of a circular wire (core) made of copper or the like is coated with a noble metal other than copper. The sheath layer is merely a thin film (with a film thickness of about 20 nm) provided to ensure corrosion resistance and the like, and the core (copper wire) inside it is responsible for conducting electricity.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a conductive member or the like that can ensure sufficient conductivity while ensuring freedom in terms of material and form.

Means for Solving the Problems

[0007] As a result of intensive research by the present inventor, it was conceived that by plating the outer peripheral surfaces of various core materials with copper, it becomes possible to provide conductive members suitable for various specifications, and this was embodied. By developing this result, the present invention described below has been completed.

[0008] 《Conductive Member》 (1) The present invention is a conductive member having a core material and a copper plating layer covering the outer peripheral surface of the core material, wherein the core material has a conductivity of 90% IACS or less, and the copper plating layer has a conductivity of 95% IACS or more.

[0009] In the conductive member of the present invention, since the copper plating layer having a high conductivity is responsible for conducting electricity, the core material does not necessarily have to be high-purity copper, and it is sufficient if it is in a form that can be plated. For this reason, various metal materials can be used for the core material, and its cross-section does not have to be constant. Therefore, according to the present invention, it is possible to achieve diversification of conductive members (expansion of freedom in terms of material and form) according to specifications, manufacturing costs, the environment, etc. Further, when energization (power supply, communication, etc.) at a high frequency (for example, 50 Hz or more, 100 Hz or more, 500 Hz or more, and further 1 kHz or more) is performed, due to the skin effect, a conductive member having a high conductivity copper plating layer can exhibit sufficient performance.

[0010] 《Manufacturing Method of Conductive Member》 The present invention can also be understood as a method for manufacturing a conductive member. For example, the present invention may be a manufacturing method including a plating step of energizing with a core material immersed in a plating bath containing copper ions as a cathode, and obtaining the above-described conductive member.

[0011] 《Others》 (1) The copper plating layer only needs to entirely cover the outer peripheral surface of the extending core material, and does not necessarily need to cover its end face. In addition to the copper plating layer being directly in close contact with the surface (interface) of the core material (base material), another layer (underlayer, barrier layer, etc.) for improving adhesion or suppressing element diffusion may be interposed at the interface between the core material (base material) and the copper plating layer.

[0012] (2) In this specification, the degree of conductivity is appropriately indicated by "%IACS". "%IACS" is the ratio of electrical conductivity (or electrical resistance) to internationally adopted annealed standard soft copper (IACS: international annealed copper standard). Note that the volume resistivity of annealed standard soft copper with a conductivity (electrical conductivity) of 100%IACS is 1.7241×10 -2 μΩm.

[0013] (3) As used in this specification, "x to y" includes the lower limit value x and the upper limit value y unless otherwise specified. An arbitrary numerical value included in various numerical values or numerical ranges described in this specification can be used as a new lower limit value or upper limit value to newly set a range such as "a to b". In addition, "x to y mm" as used in this specification means x mm to y mm. The same applies to other unit systems.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0015] One or more components arbitrarily selected from this specification may be added to the components of the present invention described above. The content described in this specification can be either a methodological component or a component related to an object.

[0016] 《Core Material》 The material, properties, form, etc. of the core material may be suitable for the required specifications of the conductive member. For example, the core material does not have to be made of copper, and furthermore, it does not have to be a conductive material. When the core material is made of a conductive material (including semiconductors, etc.), its conductivity may be, for example, 0.1 to 90% IACS, 1 to 80% IACS, 10 to 70% IACS, or 50 to 65% IACS.

[0017] The core material may be made of a metal substrate such as an aluminum substrate, an iron substrate, a copper substrate, a titanium substrate, or a magnesium substrate. As used in this specification, "X substrate" may be any of a pure metal, an alloy, or a compound, etc., as long as X is the main component (for example, the content of the X element in the whole is more than 50% by mass, and furthermore, 60% by mass or more), and its structure, etc. is not limited. For example, the iron substrate may be stainless steel, not limited to steel materials but also casting materials, and furthermore, not limited to melted materials but also sintered materials.

[0018] The core material may be, for example, linear or rod-shaped with a constant cross-section (circular, elliptical, square, irregular, etc.), or may be bent or curved. It is preferable that the corners of the core material are moderately rounded.

[0019] 《Copper Plating Layer》 The copper plating layer covers at least the outer peripheral surface along the longitudinal direction of the core material. Its thickness is not limited, but for example, it is 0.05 to 5 mm, 0.1 to 1 mm, or 0.3 to 0.8 mm. If the core material is a wire (rod) with a circular cross-section, the ratio (t / r) of the thickness (t) of the copper plating layer to the radius (r) of the core material may be, for example, 0.01 to 0.8, 0.1 to 0.7, or 0.2 to 0.6. t or t / r may be determined according to the current value and frequency applied to the conductive member.

[0020] The copper plating layer may have a high conductivity, for example, 95% IACS or more, 97% IACS or more, 98% IACS or more, 99% IACS or more, or even 100% IACS or more.

[0021] The high-conductivity copper plating layer is usually made of high-purity Cu. The purity of copper in the copper plating layer may be 99.9 mass% or more, 99.93 mass% or more, 99.95 mass% or more, or 99.97 mass% or more based on the whole.

[0022] The copper plating layer may be formed by electroless plating in addition to electroplating. However, according to electroplating (electrolytic plating), a copper plating layer with a desired thickness can be efficiently formed. Also, if the copper plating layer is formed by electroplating, various soluble copper base materials can be used as the copper supply source, which can also contribute to recycling and the like.

[0023] 《Conductive Member》 The overall conductivity (referred to as "average conductivity") of the conductive member, which combines the core material and the copper plating layer, may be, for example, 40 - 98% IACS, 50 - 95% IACS, 60 - 90% IACS, or 70 - 85% IACS. The average conductivity is usually determined along the longitudinal direction of the conductive member.

[0024] Regardless of the specific form and application, etc., the conductive member is, for example, a linear or rod-shaped wire, wiring (harness), coil, segment coil (SC) that constitutes the winding wire of an armature, etc.

[0025] 《Plating Process》 When forming the copper plating layer by electroplating (electrolysis), for example, an electric current may be passed through the core material immersed in the plating bath. The energization is preferably performed with the core material as the cathode (cathodic electroplating method). At this time, a soluble copper base material is preferably used as the anode as a stable supply source of copper ions.

[0026] The soluble copper substrate may be pure copper (oxygen-free copper, tough pitch copper, phosphor-deoxidized copper, etc.), or low-purity copper with a purity of about 20 to 95% by mass or 40 to 85% by mass. Even if the low-purity copper is used as the soluble electrode, a high-purity copper plating layer is formed on the outer peripheral surface of the core material by electroplating.

[0027] If, for example, scrap materials or recycled materials are used as the soluble copper substrate, valuable copper resources can be efficiently utilized, contributing to the achievement of SDGs (Sustainable Development Goals) and circular economy.

[0028] The plating bath may be an electrolyte containing copper ions (Cu 2+ , Cu + ). The specific composition of the plating bath is not limited, but for example, a copper sulfate plating bath, a copper cyanide plating bath, a copper pyrophosphate plating bath, etc. may be used. A copper sulfate plating bath with an aqueous copper sulfate solution as the main electrolyte is inexpensive and has excellent handleability, and levels the plating surface (leveling effect). Note that the plating bath may appropriately contain various additives.

[0029] The plating conditions may be appropriately determined in consideration of the material of the core material, the thickness and formation rate of the copper plating layer, etc. For example, the copper ion concentration in the plating bath is, for example, 0.01 to 2.5 mol / L or 0.1 to 1.5 mol / L. The temperature of the plating bath is, for example, 5 to 60°C or 10 to 40°C. The film formation rate is, for example, 0.1 to 50 μm / min or 1 to 20 μm / min.

[0030] Electrification is carried out, for example, with a current density of 0.2 to 80 A / dm 2 or 2 to 30 A / dm 2 . Depending on the desired thickness of the copper plating layer, the plating time (electrification time) is, for example, 0.5 to 20 hours or 1 to 10 hours.

[0031] Note that the core material after the plating process may be appropriately washed, surface-treated, heat-treated, painted, etc.

Examples

[0032] Samples (composite conductors / conductive members) with copper plating on the outer surface of the core material were fabricated and evaluated. Based on such specific examples, the present invention will be described in more detail.

[0033] 《Fabrication of Samples》 (1) Core Material The core materials shown in Table 1 were prepared. All of the core materials were obtained by wire drawing the raw materials into a linear or rod shape (length 300 mm).

[0034] For low-purity Cu, chromium copper (JIS Z3234) was used (the same applies to other low-purity Cu). For pure Al, A1N90 (purity 99.90% or higher) was used. Note that the purity or component composition referred to in this specification is the mass ratio with respect to the entire object and is simply expressed as “%”. The measurement method will be described later.

[0035] (2) Soluble Copper Substrate As the anode material, the soluble copper substrates shown in Table 1 were used. All of them were processed into a linear or rod shape (length 350 mm) and used in the same manner as the core material. For tough pitch copper, a commercially available material of C1100 (JIS / purity 99.90%) was used.

[0036] (3) Plating Process (Electrolysis Process) As shown in FIG. 1, with the above-described core material at the center, a plurality of soluble copper substrates were respectively arranged so as to surround the outer peripheral side thereof. These were immersed in a plating bath containing an aqueous copper sulfate solution, and direct current was applied with the core material as the cathode and each soluble copper substrate as the anode.

[0037] The concentration of the aqueous copper sulfate (CuSO4) solution was set to 1.3 mol / L, and the temperature of the plating bath was maintained at 25 to 30°C. The direct current application was performed by controlling the current (density). The current density and the energization time (plating time) for each sample are shown together in Table 1.

[0038] After the plating was completed, each sample was thoroughly washed with water. Before plating, the low-purity Cu core material and the SUS304 core material were degreased in acetone for 1 minute in advance and then subjected to the above-described plating process. The pure Al core material was subjected to a zincate treatment before plating, and then a Cu film (thickness of about 1 μm) was plated in a pyrophosphate copper bath in advance, and then subjected to the above-described plating process.

[0039] 《Observation》 The cross-sections of the composite conductors of Sample 1 and Sample 2 were magnified and observed with an optical microscope. The results are shown together with Fig. 2.

[0040] 《Measurement and Analysis》 (1) Plating Thickness The thickness of the copper plating layer was measured with a micrometer from the change in diameter before and after plating. For all samples, the diameter increased by about 1 mm due to plating, and the thickness was about 0.5 mm.

[0041] (2) Purity The purity was measured by dynamic secondary ion mass spectrometry (D-SIMS).

[0042] (3) Conductivity The conductivity of the core material and the average conductivity of the composite conductor (sample) were measured by the method specified in JIS H0505-1975. The conductivity of the copper plating layer was calculated from the conductivity of the core material and the average conductivity of the composite conductor on the assumption that the copper plating layer was uniformly formed (with a constant thickness) on the outer surface of the core material.

[0043] 《Evaluation》 As is clear from Fig. 2, it was confirmed that a composite conductor (conductive member) in which the outer peripheral surface of the core material was uniformly covered with a copper plating layer was obtained. Also, the outer peripheral surface of the copper plating layer was very smooth.

[0044] As is clear from Table 1, even when the core material and the soluble copper base material were different, all the copper plating layers had a high purity of 99.9% or more and a high conductivity of 98% IACS or more. In other words, it was found that a copper plating layer with high purity and high conductivity could be formed even by using low-purity copper materials such as scrap materials and recycled materials, without the need to use high-purity copper materials for the soluble copper base material.

[0045] Although the conductivity of the core material affected the average conductivity of the entire sample (composite conductor / conductive member), it was also found that the purity and conductivity of the copper plating layer itself, which is important due to the skin effect, were not substantially affected by the core material (material).

[0046] From the above, it was confirmed that according to the present invention, a conductive member coated with a copper plating layer having a high conductivity (or high purity), regardless of the purity of the soluble copper base material on the anode side, can be obtained.

[0047]

Table 1

Claims

1. A conductive member having a core material and a copper plating layer covering the outer peripheral surface of the core material, wherein the core material has a conductivity of 90% IACS or less, and the copper plating layer has a conductivity of 95% IACS or more.

2. The conductive member according to claim 1, wherein the copper plating layer has a copper purity of 99.9 mass% or more with respect to the whole.

3. The conductive member according to claim 1, wherein the core material is made of an aluminum base material, an iron base material or a copper base material.

4. The conductive member according to claim 1, having an average conductivity of 40% IACS or more over the entire longitudinal direction.

5. The conductive member according to claim 1, wherein the copper plating layer has a thickness of 0.05 to 5 mm.

6. A plating process comprising energizing with a core material immersed in a plating bath containing copper ions as a cathode, whereby the conductive member according to any one of claims 1 to 5 is obtained.

7. The method for manufacturing a conductive member according to claim 6, wherein the plating process is performed using a soluble copper base material having a copper purity of 20 to 95 mass% as an anode.

8. The method for manufacturing a conductive member according to claim 7, wherein the soluble copper base material is made of a scrap material or a recycled material.

9. The method for manufacturing a conductive member according to claim 6, wherein the plating bath is composed of an aqueous copper sulfate solution.

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