Conductor with terminal

Abstract

To provide a conductor with a terminal capable of suppressing an increase in an electric resistance value between a conductor and a terminal when the conductor with the terminal is placed in a high-temperature environment.SOLUTION: A conductor with a terminal includes a conductor and a terminal connected to the conductor by caulking. The conductor includes a plurality of Al single wires located at a center part of the conductor, a plurality of Cu single wires located at an outer peripheral part of the conductor, and a first plating layer covering a surface of each Cu single wires. At least an outermost surface of the first plating layer is made of a CuSn alloy.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to terminated conductors. [Background technology]

[0002] Patent Document 1 discloses a conductor with terminal. The conductor with terminal includes a conductor and a terminal. The terminal is connected to the end of the conductor by crimping. The conductor is composed of Al wires and Cu wires. The Al wires are located in the center. The Cu wires are located on the periphery. A tin-plated layer is formed on the surface of the Cu wires. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jikko No. 58-6089 Summary of the Invention [Problem to be solved by the invention]

[0004] When a conventional conductor with terminals is placed in a high-temperature environment, the electrical resistance between the conductor and the terminal increases over time. In one aspect of the present disclosure, it is preferable to provide a conductor with terminals that can suppress an increase in the electrical resistance between the conductor and the terminal when the conductor with terminals is placed in a high-temperature environment. [Means for solving the problem]

[0005] One aspect of the present disclosure is a terminal-attached conductor including a conductor and a terminal connected to the conductor by crimping, the conductor including a plurality of Al wires located in a center portion of the conductor, a plurality of Cu wires located in an outer periphery of the conductor, and a first plating layer covering surfaces of the Cu wires, and at least the outermost surface of the first plating layer is made of a CuSn alloy.

[0006] A terminal-equipped conductor according to one aspect of the present disclosure can suppress an increase in electrical resistance between the conductor and the terminal when placed in a high-temperature environment. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a plan view illustrating a configuration of a terminal-equipped conductor. [Figure 2] FIG. 2 is a side view illustrating the configuration of a terminal-attached conductor. [Figure 3] FIG. 2 is a cross-sectional view taken along the line III-III in FIG. [Figure 4] FIG. 2 is a cross-sectional view showing the configuration of a Cu wire and a plating layer. [Figure 5] FIG. 2 is a cross-sectional view taken along the line VV in FIG. [Figure 6] 1 is a graph showing measured values ​​of the resistance increase rate ΔR in a terminal-attached conductor. [Figure 7] FIG. 1 is an explanatory diagram showing a binarized SEM image. [Figure 8] 1 is a table showing measurement results of crack area ratios. [Figure 9] 1 is a photograph showing a cross section of a Cu wire before being crimped. [Figure 10] This is a photograph showing the interface between the Cu wire and the Al wire in the crimped portion. [Figure 11] 1 shows the results of SEM observation (×2000) of the surfaces of an Al wire and a Cu wire. [Figure 12] FIG. 1 is an explanatory diagram showing a phenomenon that is presumed to occur at the interface between an Al wire and a Cu wire when they are crimped together. DETAILED DESCRIPTION OF THE INVENTION

[0008] Exemplary embodiments of the present disclosure will now be described with reference to the drawings. 1. Configuration of terminal-attached conductor 1 The configuration of the conductor with terminal 1 will be described with reference to Fig. 1 to Fig. 5. As shown in Fig. 1 and Fig. 2, the conductor with terminal 1 includes a conductor 3, a terminal 5, and an insulating layer .

[0009] As shown in Fig. 3, the conductor 3 has a structure in which a plurality of bundles 11 and a plurality of bundles 13 are twisted together. Each of the plurality of bundles 11 is formed by twisting a plurality of Al element wires. Each of the plurality of bundles 13 is formed by twisting a plurality of Cu element wires.

[0010] The number of Al wires included in one bundle 11 is, for example, 1 to 102. The number of Cu wires included in one bundle 13 is, for example, 1 to 102. The number of bundles 11 included in the conductor 3 is, for example, 7 to 37. The number of bundles 13 included in the conductor 3 is, for example, 12 to 24.

[0011] The diameter of the Al wire is, for example, 100 μm or more and 450 μm or less, and the diameter of the Cu wire is, for example, 100 μm or more and 450 μm or less. As shown in FIG. 3 , in the unclamped portion, bundle 11 is located in the center of conductor 3. Bundle 13 is located on the outer periphery of conductor 3. Bundle 13 is located closer to the outer periphery than bundle 11. Therefore, the Al wires are located in the center of conductor 3. In addition, the Cu wires are located on the outer periphery of conductor 3.

[0012] The Al wire is made of pure aluminum or an aluminum alloy (hereinafter referred to as "aluminum material"). Pure aluminum is a material made of Al and inevitable impurities. An example of pure aluminum is electrical pure aluminum (ECAl). An example of an aluminum alloy is Al-Zr, Al-Fe-Zr, etc. Al-Zr is an aluminum alloy having a chemical composition containing 0.03 to 1.5 mass% Zr, 0.1 to 1.0 mass% Fe and Si, and the balance being Al and inevitable impurities. Also, Al-Fe-Zr is an aluminum alloy containing 0.01 to 0.10 mass% Zr, 0.1 mass% or less Si, 0.2 to 1.0 mass% Fe, 0.01 mass% or less Cu, 0.01 mass% or less Mn, 0.01 mass% or less Mg, 0.01 mass% or less Zn, 0.01 mass% or less Ti, and 0.01 mass% or less V, with the remainder being Al and unavoidable impurities. In Al-Zr, "0.1 to 1.0 mass% Fe and Si" has the following meanings: When both Fe and Si are contained, the total concentration of Fe and Si is 0.1 to 1.0 mass%; When Fe is contained but Si is not contained, the Fe concentration is 0.1 to 1.0 mass%; When Si is contained but Fe is not contained, the Si concentration is 0.1 to 1.0 mass%. Here, "not contained" means that the content is below the detection limit in, for example, high-frequency inductively coupled plasma atomic emission spectrometry.

[0013] As shown in FIG. 4, the surface of the Cu wire 21 is covered with a plating layer 23. The Cu wire 21 is made of a copper material. The copper material is a material containing copper as a main component. Examples of copper materials include Tough-Pitch Copper (TPC), oxygen-free copper, and copper alloys. Examples of copper alloys that can be used include copper alloys containing a predetermined amount of one or more metal elements selected from magnesium, tin, indium, silver, nickel, zinc, and the like. In this embodiment, it is preferable to apply a lubricant to the surface of the metal wire to further prevent breakage due to friction between the metal wires. Examples of lubricant include liquid paraffin.

[0014] At least the outermost surface of the plating layer 23 is made of a CuSn alloy. For example, the entire plating layer 23 is made of a CuSn alloy. One method for forming the plating layer 23 is to form a plating layer made of Cu on the surface of the Cu element wire 21 and then heat treat it. When this method is performed, the Cu element wire 21 reacts with Sn to form a CuSn alloy layer. If the layer made of Sn is formed sufficiently thin, the outermost surface of the plating layer 23 will be made of a CuSn alloy. The method for forming the plating layer 23 is not particularly limited. It is preferable to form the plating layer 23 by hot dip plating.

[0015] The thickness of the plating layer 23 is 2 μm or less. By making the thickness of the plating layer 23 2 μm or less, the resistance increase rate ΔR of the terminaled conductor 1 can be suppressed. The resistance increase rate ΔR will be described later. The thickness of the plating layer 23 is measured by forming a cross section of the Cu element wire 21 by cross section polishing after embedding in resin, FIB (Focused Ion Beam) processing, ion milling, or other cross section forming method, measuring the thickness of the plating layer 23 at multiple points in an arbitrary observation area, and calculating the average value of the measured thicknesses. The thickness of the plating layer 23 is preferably 0.05 μm or more.

[0016] The terminals 5 are connected to the ends of the conductor 3. For example, as shown in Figures 1 and 2, one terminal 5 is connected to one end of the conductor 3, and another terminal 5 is connected to the other end of the conductor 3. Alternatively, the terminals 5 may be connected to only one end of the conductor 3.

[0017] The terminal 5 includes, for example, a tubular portion 31 and a flat portion 33. The tubular portion 31 has a hollow cylindrical shape. The flat portion 33 has a plate-like shape. For example, a through hole 35 is formed in the flat portion 33. The through hole 35 penetrates the flat portion 33 in the thickness direction of the flat portion 33. Examples of the material for the terminal 5 include a copper material. For example, the surface of the terminal 5 is covered with a plating layer. Examples of the plating layer covering the surface of the terminal 5 include a hot-dip Sn plating layer and an electrolytic Sn plating layer. In particular, it is preferable that a Sn plating layer having a thickness of 2 μm or more is formed on the inner surface of the tubular portion 31 into which the end of the conductor 3 is inserted. In this case, the outermost surface of the plating layer formed on the inner surface of the tubular portion 31 is made of Sn.

[0018] The conductor 3 and the terminal 5 can be connected, for example, by the following method: The end of the conductor 3 is inserted into the cylindrical portion 31. The cylindrical portion 31 is crimped to connect the conductor 3 and the terminal 5. The crimping can be, for example, compression or crimping. The conductor 3 and the terminal 5 in the crimped portion are compressed or crimped.

[0019] As a crimping method, for example, there is a compression method in which pressure P is applied to only a part of tubular portion 31 from only one direction as shown in Fig. 5. The crimping method may also be a crimping method in which a predetermined pressure P is applied to the entire circumferential direction of tubular portion 31. As shown in Fig. 5, in the crimped portions, tubular portion 31, bundles 11, and bundles 13 are compressed and have a deformed shape.

[0020] 1 and 2, the insulating layer 7 covers the surface of the conductor 3. However, the insulating layer 7 does not cover the end of the conductor 3 that is inserted into the cylindrical portion 31. In the crimped portion, the plating layer 23 may crack, and the surface of the Cu wire 21 may be exposed from the plating layer 23. The ratio of the surface of the Cu wire 21 that is exposed from the plating layer 23 is defined as the crack area ratio X. The crack area ratio X is calculated by the following formula (1). The unit of the crack area ratio X is %.

[0021] Formula (1) X=(S1 / S2)×100 S2 is the area of ​​the field of view when the Cu wire 21 in the crimped portion is observed with a SEM (Scanning Electron Microscope). The field of view is an area of ​​40 μm × 60 μm. S1 is the area of ​​the portion of the surface of the Cu wire 21 within the field of view where the surface is exposed from the plating layer 23. A method for calculating S1 will be described later. When the crack area ratio X is 10% or more and 40% or less, the resistance increase rate ΔR of the terminal-attached conductor 1 can be further suppressed.

[0022] 2. Effects of the terminal-attached conductor 1 (2-1) The conductor with terminal 1 can suppress the rate of increase in resistance ΔR even in a high-temperature environment, for example, an environment where the temperature is 125° C. or higher.

[0023] (2-2) When the crack area ratio X is 10% or more and 40% or less, the conductor with terminal 1 can further suppress the resistance increase rate ΔR. 3. Working Example (3-1) Manufacturing of terminal-attached conductors 1A, 1B, and 1C A conductor with terminal 1A having the configuration shown in Figs. 1 to 5 was manufactured. The conductor 3 had 19 bundles 11. Each bundle 11 had 16 Al wires. The diameter of each Al wire was 0.45 mm. The material of the Al wires was an Al-Fe-Zr alloy. The conductor 3 had 18 bundles 13. Each bundle 13 had 16 Cu strands 21. The diameter of each Cu strand 21 was 0.45 mm. The material of the Cu strands 21 was TPC. A plating layer 23 was formed on the surface of the Cu wire 21 by hot-dip Sn plating. Energy dispersive X-ray spectroscopy (EDX) was performed on the surface of the plating layer 23 (i.e., the outer surface of the conductor 3), and it was confirmed that the entire plating layer 23 was made of a CuSn alloy. That is, the plating layer 23 was a CuSn alloy layer. The thickness of the plating layer 23 was 0.3 μm.

[0024] A terminal-attached conductor 1B was manufactured, which basically had the same configuration as the terminal-attached conductor 1A, except that the plating layer 23 of the terminal-attached conductor 1B was a Ni plating layer. A terminal-attached conductor 1C was manufactured, which basically had the same configuration as the terminal-attached conductor 1A. However, in the terminal-attached conductor 1C, both the bundles 11 and 13 were composed of Al wires. In the terminal-attached conductors 1A to 1C, no plating layer was formed on the surface of the Al wires. Furthermore, the terminals 5 used in the terminal-attached conductors 1A to 1C were crimp terminals made of pure copper. A 4 μm-thick Sn plating layer was formed on the entire surface of the terminal 5. The outermost surface of the plating layer formed on the inner circumferential surface of the tubular portion 31 of the terminal 5 was made of Sn.

[0025] (3-2) Measurement of the resistance increase rate ΔR The resistance increase rate ΔR was measured for each of the terminal-attached conductors 1A, 1B, and 1C. The resistance increase rate ΔR was measured as follows. The terminal-attached conductors 1A, 1B, and 1C were placed in an ambient atmosphere at a temperature of 180°C (hereinafter referred to as a high-temperature environment). The electrical resistance between the conductor 3 and the terminal 5 was measured repeatedly at predetermined intervals using the four-terminal resistance measurement method described in JP 2020-119863 A. The electrical resistance value before placing the terminal-attached conductors 1A, 1B, and 1C in the high-temperature environment was defined as R0. The resistance increase rate ΔR was calculated using the following formula (2). The unit of the resistance increase rate ΔR was %. The electrical resistance measurement was performed after the temperatures of the conductor 3 and the terminal 5 had been naturally cooled to room temperature.

[0026] Equation (2) ΔR={(R(t)−R0) / R0)}×100 R(t) is the electrical resistance value after t hours have passed since the terminal-attached conductors 1A, 1B, and 1C were placed in a high-temperature environment. Figure 6 shows the measurement results of the resistance increase rate ΔR. The terminal-attached conductor 1A had a small resistance increase rate ΔR. Specifically, the resistance increase rate ΔR after 48 hours was 3.7%, the resistance increase rate ΔR after 96 hours was 5.7%, and the resistance increase rate ΔR after 168 hours was 6.0%, all of which were below the target value of 20% for the resistance increase rate ΔR. The terminal-attached conductors 1B and 1C had a larger resistance increase rate ΔR than the terminal-attached conductor 1A, and all exceeded the target value of 20% for the resistance increase rate ΔR after 48 hours.

[0027] (3-3) Calculation of crack area ratio X The Cu wire 21 in the crimped portion of the terminal-attached conductor 1A was observed using an SEM, and SEM images were obtained in fields 1 to 6 on the surface of the Cu wire 21. The magnification of the SEM images was 2,000 times. The size of one field was 40 μm × 60 μm. Next, the brightness of each pixel in the SEM backscattered electron images obtained in fields 1 to 6 was binarized. The threshold value for binarization was set to a value at which areas where the Sn concentration exceeded 20% of the Cu concentration became bright when elemental analysis was performed using EDX. The binarized SEM image is shown in Figure 7. The dark areas in the binarized SEM image are areas where the plating layer 23 is cracked and the Cu wires 21 are exposed from the plating layer 23, and are Cu. The bright areas in the binarized SEM image are areas where the plating layer 23 remains and the Cu wires 21 are not exposed, and are CuSn alloys. The area of ​​the entire binarized SEM image was defined as S2. The area of ​​the dark areas in the entire binarized SEM image was defined as S1. The crack area ratio X was calculated using the above-mentioned formula (1). The measurement results of the crack area ratio X are shown in Figure 8. The "total area" in Figure 8 is S2 in formula (1). The "dark area" in Figure 8 is S1 in formula (1). The "percentage" in Figure 8 is the crack area ratio X. In every field of view, the crack area ratio X was 10% or more and 40% or less.

[0028] (3-4) Observation of plating layer 23 Before crimping, the cross section of the Cu wire 21 of the conductor with terminal 1A was observed with an SEM at a magnification of 10,000 times. The cross section of the Cu wire 21 is shown in Fig. 9. The plating layer 23 covered the entire surface of the Cu wire 21 and was not cracked.

[0029] Next, the interface between the Cu wire 21 and the Al wire in the crimped portion of the terminal-attached conductor 1A was observed using an SEM at a magnification of 10,000 times. The interface between the Cu wire 21 and the Al wire is shown in FIG. 10. As shown in FIG. 10, there was a portion where the plating layer 23 was cracked (i.e., a cracked portion). From the SEM images in FIGS. 9 and 10, it can be inferred that the plating layer 23 was cracked when the wire was crimped, and the surface of the Cu wire 21 was exposed from the plating layer 23.

[0030] (3-5) Observation of the surfaces of Al and Cu wires The surfaces of the Al wires and Cu wires 21 obtained from the front end side 41 of the compressed portion shown in Fig. 1 were observed with an SEM at a magnification of 2,000 times. In addition, the surfaces of the Al wires and Cu wires 21 obtained from the vicinity of the center 43 of the compressed portion shown in Fig. 1 were observed with an SEM at a magnification of 2,000 times. The vicinity of the center 43 of the compressed portion is a part that is more strongly crimped than the front end side 41 of the compressed portion. The SEM observation results (×2000) of each surface are shown in Fig. 11.

[0031] Vertical stripes were observed on the surface of the Al wire obtained from the center 43 of the compressed portion. No vertical stripes were observed on the surface of the Al wire obtained from the tip 41 of the compressed portion. The vertical stripes that make up the vertical stripe pattern extended in a direction parallel to the longitudinal direction of the conductor 3. It is presumed that the vertical stripes were generated as follows.

[0032] 12 shows the interface between the Cu wire 21 and the Al wire 51 before the start of crimping. The surface of the Cu wire 21 is covered with the plating layer 23. There are few cracks in the plating layer 23 at this stage.

[0033] 12 shows the state when the crimping starts. The plating layer 23 cannot keep up with the deformation of the Cu wire 21 caused by the crimping, and cracks. STEP 3 in Figure 12 shows the state when crimping is completed. The Al wire 51 is embedded in the gap created by the crack in the plating layer 23. At high temperatures, the Al wire 51 and the Cu wire 21 are bonded together, which can suppress an increase in resistance during high-temperature testing. In addition, displacement of the contact points between the Al wire 51 and the Cu wire 21 due to deformation caused by the difference in linear expansion between the Al wire 51 and the Cu wire 21 during heat cycles is suppressed. The cracked plating layer 23 is pressed against the surface of the Al wire 51, resulting in a vertical stripe pattern on the surface of the Al wire 51.

[0034] 4. Other Embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0035] (4-1) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0036] (4-2) In addition to the above-described conductor with terminal 1, the present disclosure can also be realized in various forms, such as a product having the conductor with terminal 1 as a component, a method for manufacturing the terminal 5, and a method for manufacturing the conductor with terminal 1. [Explanation of symbols]

[0037] 1, 1A, 1B, 1C...conductor with terminal, 3...conductor, 5...terminal, 7...insulating layer, 11, 13...bundle, 21...Cu wire, 23...plating layer, 31...tubular portion, 33...flat portion, 35...through hole, 41...tip side of compressed portion, 43...near center of compressed portion, 51...Al wire

Claims

1. A terminal-attached conductor comprising a conductor and a terminal connected to the conductor by crimping, The conductor is A plurality of Al wires located at the center of the conductor; a plurality of Cu wires positioned on an outer periphery of the conductor; a first plating layer covering a surface of the Cu wire; Equipped with At least the outermost surface of the first plating layer is made of a CuSn alloy. Conductor with terminal.

2. The terminal-attached conductor according to claim 1, The entire first plating layer is made of a CuSn alloy. Conductor with terminal.

3. The terminal-attached conductor according to claim 1 or 2, 10% to 40% of the surface of the Cu wire in the crimped portion is exposed from the first plating layer. Conductor with terminal.

4. The terminal-attached conductor according to any one of claims 1 to 3, No plating layer is formed on the Al wire. Conductor with terminal.

5. The terminal-attached conductor according to any one of claims 1 to 4, The terminal is made of a copper material. Conductor with terminal.

6. The terminal-attached conductor according to claim 5, The terminal is a cylindrical portion into which an end of the conductor is inserted; a second plating layer covering an inner circumferential surface of the cylindrical portion; Equipped with The outermost surface of the second plating layer is made of Sn. Conductor with terminal.

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