Copper-based conductor, twisted conductor and electric wire

Abstract

To provide a copper-based conductor capable of promoting bonding with a terminal when the terminal is bonded to the copper-based conductor to form an electric wire with the terminal, and capable of enhancing tensile durability of the electric wire with the terminal.SOLUTION: In crystal orientation analysis performed by an electronic backscatter diffraction method on a cross-section perpendicular to a drawing direction, a copper-based conductor has a total accumulation rate of 40% or more, where the total accumulation rate is the ratio of the average value of a first total area and a second total area to the total area of the crystalline grains contained within a first measurement region, wherein the first total area is obtained by summing the areas of crystal grains containing a <011> orientation group which is crystal orientations within ±8° of the <011> orientation, a <012> orientation group which is crystal orientations within ±8°of the <012> orientation and a <123> orientation group which is crystal orientations within ±8° of the <123> orientation within the selected first measurement region in the cross section, with respect to a first direction and the second total area is obtained by summing the areas of crystal grains containing a <011> orientation group, a <012> orientation group and a <123> orientation group with respect to a second direction perpendicular to the first direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a copper-based conductor, a stranded conductor, and an electric wire. [Background technology]

[0002] Electric wires used in electrical appliances, automotive components, etc. are made of copper-based conductors with high conductivity, and terminals are provided on both ends. In particular, when ultrasonic waves are applied to join the copper-based conductor at the end of the electric wire to the terminals, copper-based conductors are used because they are soft and easily deformed by the ultrasonic output.

[0003] As such a copper-based conductor, for example, Patent Document 1 describes a copper alloy conductor having 50 to 250 crystal grains per cross-sectional area, the maximum grain size of which is 1 / 3 or less of the diameter of the bonding wire, and <100> The document describes a copper alloy bonding wire characterized by being non-oriented, with all specific orientations such as those mentioned above being 40% or less, and claims that this has the effect of preventing the tip of the bonding wire from bending into a J shape and providing a copper alloy bonding wire whose cut end does not protrude from the cross-sectional area of ​​the bonding wire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-045924 Summary of the Invention [Problem to be solved by the invention]

[0005] When ultrasonic waves are applied to join a copper-based conductor at the end of an electric wire to a terminal, if the copper-based conductor lacks softness, a gap is formed, particularly between the copper-based conductor and the terminal, which reduces the bonding strength between the terminal and the electric wire and further reduces the tensile durability of the resulting electric wire with terminal. Therefore, there has been a demand for a copper-based conductor that has high tensile durability when a terminal is joined to the copper-based conductor to form an electric wire with terminal.

[0006] In this regard, the bonding wire described in Patent Document 1 relates to a copper alloy bonding wire having a wire diameter of 15 μm or more and 20 μm or less, and does not focus on copper-based conductors with a larger diameter than this. There was room for improvement in that the bonding wire should be made more susceptible to deformation by the application of ultrasonic waves during ultrasonic bonding, thereby promoting bonding between the copper-based conductor and the terminal, and increasing the tensile durability of the terminal-attached electric wire when the terminal is bonded to the copper-based conductor.

[0007] Therefore, the present invention has been made in consideration of the above problems, and has an object to provide a copper-based conductor that can promote bonding between the copper-based conductor and a terminal when the terminal is joined to the copper-based conductor to form an electric wire with terminal, and can increase the tensile durability of the electric wire with terminal, and a stranded conductor and an electric wire using the same. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that the area of ​​the crystal grains in the measurement region in the cross section is <011> direction, <012> Orientation or <123> The inventors discovered that by increasing the proportion of oriented crystal grains, when a copper-based conductor or a stranded conductor is joined to a terminal by ultrasonic bonding to form an electric wire with terminal, the copper-based conductor can be easily deformed by applying ultrasonic waves to the copper-based conductor, thereby reducing voids that were present at the joint between the copper-based conductor and the terminal and voids that were present inside the stranded conductor, thereby promoting bonding between the copper-based conductor and the terminal and increasing the tensile durability of the electric wire with terminal, and thus completed the present invention.

[0009] In order to achieve the above object, the gist of the present invention is as follows. (1) A copper-based conductor, wherein in a crystal orientation analysis performed on a cross section perpendicular to the extension direction of the conductor by an electron backscatter diffraction (EBSD) method, an xy Cartesian coordinate system is defined within the cross section, and a first direction is assumed to be a direction on the x-axis, and a second direction is assumed to be a direction on the y-axis, <011> Crystal orientation within ±8° <011> The orientation group is <012> Crystal orientation within ±8° <012> A directional group, and <123> Crystal orientation within ±8° <123> When the orientation group is a group of orientations, in a first measurement area selected in the transverse section, <011> Orientation group, said <012> Orientation groups and the above <123> a first total area obtained by adding up the areas of crystal grains having the orientation group, and <011> Orientation group, said <012> Orientation groups and the above <123> A copper-based conductor in which the total concentration rate, which is the ratio of the average value of the area of ​​crystal grains having an orientation group and a second total area obtained by adding up the areas of crystal grains having an orientation group to the total area of ​​crystal grains included in the first measurement region, is 40% or more. (2) When the cross section is divided into a central portion and an outer ring portion surrounding the central portion, in a second measurement region selected in the central portion of the cross section, <011> Orientation group, said <012> Orientation groups and the above <123> a first total area obtained by adding up the areas of crystal grains having the orientation group, and <011> Orientation group, said <012> Orientation groups and the above <123> The copper-based conductor described in (1) above, wherein the total concentration rate, which is the ratio of the average value of the second total area obtained by adding up the areas of crystal grains having an orientation group to the total area of ​​crystal grains included in the second measurement region, is 50% or more. (3) The copper-based conductor according to (1) or (2) above, wherein the average crystal grain size of the crystal grains present in the cross section is less than 20.0 μm. (4) A stranded conductor formed by twisting together a plurality of copper-based wires made of the copper-based conductor according to any one of (1) to (3) above. (5) An electric wire in which at least an insulating coating layer is formed on the surface of the copper-based conductor according to (1), (2), or (3) above, or the stranded conductor according to (4) above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a copper-based conductor that can promote bonding between the copper-based conductor and a terminal when the terminal is joined to the copper-based conductor to form an electric wire with terminal, and can increase the tensile durability of the electric wire with terminal, as well as a stranded conductor and an electric wire using the same. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view schematically showing the height of a joint in an electric wire with a terminal in which a stranded conductor formed by twisting together a plurality of copper-based conductors of the present invention is joined to a flat portion of a terminal. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the copper-based conductor of the present invention will be described in detail below. In the component composition of the copper-based conductor of the present invention, "mass %" may be simply represented as "%".

[0013] In the crystal orientation analysis of the copper-based conductor according to the present invention, which is performed on a cross section perpendicular to the extension direction of the conductor using electron backscatter diffraction, an xy Cartesian coordinate system is defined within the cross section, and a first direction is assumed to be a direction on the x-axis, and a second direction is assumed to be a direction on the y-axis, <011> Crystal orientation within ±8° <011> The orientation group is <012> Crystal orientation within ±8° <012> A directional group, and <123> Crystal orientation within ±8° <123> When the orientation group is set, in a first measurement area selected in the cross section, with respect to a first direction, <011> orientation group, <012> Orientation groups and <123> A first total area is calculated by adding up the areas of the crystal grains having the orientation group, and a second direction is calculated by adding up the areas of the crystal grains having the orientation group. <011> orientation group, <012> Orientation groups and <123> The average value of the second total area obtained by adding up the areas of the crystal grains having the orientation group is the ratio of the total area of ​​the crystal grains contained in the first measurement region to the total area of ​​the crystal grains contained in the first measurement region (hereinafter referred to as "the ratio of the total area of ​​the crystal grains contained in the first measurement region to the total area of ​​the crystal grains contained in the first measurement region"). <011> orientation group, <012> Orientation groups and <123> The total concentration of crystal grains with a group of orientations (sometimes referred to as the "total concentration of crystal grains with a group of orientations") is 40% or more.

[0014] In the copper-based conductor of the present invention, in particular, the ratio of the area of ​​the crystal grains included in the first measurement region in the cross section to the total area of ​​the crystal grains is <011> orientation group, <012> Orientation groups and <123> By making the total concentration rate of crystal grains having an orientation group 40% or more, the crystal orientation of the crystal grains appearing in the cross section is controlled, and as a result, among the crystal grains appearing in the first measurement area of ​​the cross section, those that can be deformed with a smaller force when ultrasonic waves are applied. <011> orientation group, <012> Orientation groups and <123> Therefore, when a terminal is joined to a copper-based conductor by ultrasonic bonding to form an electric wire with terminal, the copper-based conductor is made more deformable, which reduces voids that existed at the joint between the copper-based conductor and the terminal and voids that existed inside the stranded conductor.As a result, bonding between the copper-based conductor and the terminal is promoted, and the tensile durability of the electric wire with terminal can be improved.

[0015] The copper-based conductor according to the present invention can provide a copper-based conductor that has high tensile durability when a terminal is joined to the copper-based conductor to form a terminal-attached electric wire, as well as a stranded conductor and electric wire using the same. This makes it possible to easily deform the copper-based conductor and promote bonding with the terminal when producing a terminal-attached electric wire for use in electrical appliances or automobiles by ultrasonic bonding, thereby stably bonding the copper-based conductor and the terminal and thereby achieving a high-quality electric wire connection. Furthermore, because the copper-based conductor according to the present invention can be easily deformed by applying ultrasonic waves, it can also be suitably used as a bonding wire in which the wire is deformed and bonded to a semiconductor chip.

[0016] [1] Metal structure of copper-based conductors The copper-based conductor according to the present invention has a crystal grain area of ​​1000 μm, which is approximately 100 μm in the total area of ​​the crystal grains included in the first measurement region. <011> orientation group, <012> Orientation groups and <123> The total concentration of crystal grains having the orientation group is 40% or more. Here, in order to make the copper-based conductor easily deformable by applying ultrasonic waves, it is important to control the crystal orientation of the crystal grains in the direction in which the copper-based conductor deforms. In this regard, the inventors have determined that the crystal orientation of the crystal grains is controlled to be in the direction in which the copper-based conductor deforms. <011> orientation group, <012> Orientation groups and <123> It was found that by increasing the number of crystal grains with orientation groups, the copper-based conductor can be easily deformed with a weak force. <011> orientation group, <012> Orientation groups and <123> If the total concentration of crystal grains having the orientation group is less than 40%, the concentration of crystal grains having other orientations will be relatively high, and a larger force will be required in the direction of deformation. <011> orientation group, <012> Orientation groups and <123> The total accumulation rate of the crystal grains having the orientation group is preferably 60% or more, more preferably 80% or more. On the other hand, the ratio of the total area of ​​the crystal grains included in the first measurement region to the total area of ​​the crystal grains is <011> orientation group, <012> Orientation groups and <123> The upper limit of the ratio of the total accumulation rate of crystal grains having an orientation group is not particularly limited, but may be, for example, 100%.

[0017] The proportion of the total area of ​​the crystal grains included in the first measurement region in the cross section, <011> orientation group, <012> Orientation groups and <123> The total accumulation ratio of crystal grains having a group of orientations can be obtained, for example, by continuously measuring crystal orientation data using an EBSD detector (OIM5.0 HIKARI, manufactured by TSL) attached to a high-resolution scanning analytical electron microscope (JSM-7001FA, manufactured by JEOL Ltd.), and then calculating (processing) the measured crystal orientation data using analysis software (OIM Analysis, manufactured by TSL Solutions). "EBSD" stands for Electron Backscatter Diffraction, a crystal orientation analysis technique that utilizes backscattered electron Kikuchi diffraction generated when an electron beam is irradiated on a copper-based conductor sample in a scanning electron microscope (SEM). The measurement object is a mirror-finished surface of a cross section of a copper-based conductor perpendicular to the extension direction. The measurement area is a first measurement area selected within the cross section, but it can also be the entire cross section. When a portion of the cross section is used as the first measurement area, the measurement area can be, for example, 200 μm to 500 μm square. The cross section can be polished by a Cross Section Polisher (registered trademark) device, or by wet polishing, or by a means capable of mirror finishing such as FIB or microtome, and the specific means are not limited. For the obtained crystal orientation data, two directions that are 90° apart perpendicular to the longitudinal direction of the wire are selected on the IPFmap to define an xy Cartesian coordinate system, and then a first direction on the x-axis and a second direction on the y-axis are defined. From the chart-crystal direction obtained using analysis software, boundaries where the orientation difference between adjacent measurement points is 15° or more are defined as crystal grain interfaces (grain boundaries). A set of consecutive measurement points within the range surrounded by the grain boundaries is defined as a crystal grain. <011> Crystal orientation within ±8° <011> The orientation group is <012> Crystal orientation within ±8° <012> A directional group, and <123> Crystal orientation within ±8° <123> It can be a group of directions.At this time, the ratio of the total area of ​​the crystal grains included in the first measurement region in the first and second directions is: <011> orientation group, <012> Orientation groups and <123> The area ratio of each crystal grain having an orientation group is measured, and typically this measurement is performed three times (n=3) at different locations within the first measurement region, and the average of the area ratios of the crystal grains having each orientation group obtained from the three measurements is calculated. Then, the total accumulation rate of the crystal grains having each orientation group is calculated from the average of the area ratios of the crystal grains having each orientation group for the first and second directions, and by calculating the average of the first and second directions, the ratio of the area ratio of the crystal grains to the total area of ​​the crystal grains included in the first measurement region is calculated. <011> orientation group, <012> Orientation groups and <123> A measure of the percentage of the total accumulation of grains with an orientation group can be obtained.

[0018] Furthermore, when the cross section of the copper-based conductor according to the present invention is divided into a central portion and an outer ring portion surrounding the central portion, in a second measurement region selected within the central portion of the cross section, the following is true with respect to the first direction: <011> orientation group, <012> Orientation groups and <123> A first total area is calculated by adding up the areas of the crystal grains having the orientation group, and a second direction is calculated by adding up the areas of the crystal grains having the orientation group. <011> orientation group, <012> Orientation groups and <123> The average value of the second total area obtained by adding up the areas of the crystal grains having the orientation group is the ratio of the total area of ​​the crystal grains included in the second measurement region to the total area of ​​the crystal grains included in the second measurement region (hereinafter referred to as "total area of ​​the crystal grains included in the second measurement region"). <011> orientation group, <012> Orientation groups and <123> It is preferable that the total concentration rate of crystal grains having a group of orientations is 50% or more. When a copper-based conductor is deformed by applying ultrasonic waves, the copper-based conductor is often deformed in a direction that compresses the conductor. Therefore, the ratio of the total area of ​​crystal grains included in the second measurement region selected in the center of the cross section to the total area of ​​crystal grains included in the second measurement region selected in the center of the cross section is <011> orientation group, <012> Orientation groups and <123> By making the total concentration rate of the crystal grains having the orientation group 50% or more, the copper-based conductor becomes more easily deformed from the center, and therefore the copper-based conductor can be deformed with a smaller force. <011> orientation group, <012> Orientation groups and <123> The total concentration of crystal grains having an orientation group is more preferably 60% or more, and even more preferably 80% or more.

[0019] Here, the "center of the cross section" in this specification refers to a region having the same center of gravity as the center of gravity of the cross section when observing a cross section perpendicular to the extension direction of the copper-based conductor, having an area of ​​1 / 9 of the cross section from this center of gravity, and having a similar shape to the cross section. For example, if the copper-based conductor is a round wire, the center (center of gravity) can be taken as the same center (center of gravity) as the center (center of gravity) of the circular cross section when observing a cross section perpendicular to the extension direction of the copper-based conductor, and the region can be a region within a concentric circle from this center (center of gravity) whose diameter is 1 / 3 of the cross section.

[0020] The proportion of the total area of ​​the crystal grains included in the second measurement region in the cross section, <011> orientation group, <012> Orientation groups and <123> The total accumulation rate of the crystal grains having the orientation group can be determined, for example, by measuring the second measurement area, which is the center of the cross section, in the same manner as in the case of measuring the first measurement area. That is, the ratio of the area of ​​the crystal grains in the first and second directions to the total area of ​​the crystal grains included in the second measurement area is calculated. <011> orientation group, <012> Orientation groups and <123> The area ratio of each crystal grain having an orientation group is measured, and typically this measurement is performed three times (n=3) at different locations within the second measurement region, and the average of the area ratios of the crystal grains having each orientation group obtained from the three measurements is calculated. Then, the total accumulation rate of the crystal grains having each orientation group is calculated from the average of the area ratios of the crystal grains having each orientation group for the first and second directions, and by calculating the average of the first and second directions, the ratio of the area ratio of the crystal grains to the total area of ​​the crystal grains included in the second measurement region is calculated. <011> orientation group, <012> Orientation groups and <123> A measure of the percentage of the total area of ​​grains having the orientation group can be obtained, where the percentage of the total area of ​​grains in the second measurement region is: <011> orientation group, <012> Orientation groups and <123> The crystal orientation data used to calculate the total concentration rate of crystal grains having an orientation group may be data extracted from the crystal orientation data obtained by electron backscatter diffraction (EBSD) performed on the second measurement area.

[0021] In the copper-based conductor according to the present invention, the average crystal grain size in the cross section is preferably less than 20.0 μm. This reduces the variation in the bonding when the copper-based conductor or a stranded conductor formed by twisting multiple copper-based conductors together is ultrasonically bonded to a terminal, thereby enabling more stable bonding. Therefore, the average crystal grain size in the cross section is more preferably 15.0 μm or less, and even more preferably 10.0 μm or less. On the other hand, the lower limit of the crystal grain size is not particularly limited, but may be set to 1.0 μm, for example, from the viewpoint of making the copper-based conductor easily deformable.

[0022] Here, the average grain size of the crystal grains of the copper-based conductor can be determined by analyzing the crystal orientation data of the electron backscatter diffraction (EBSD) method described above, selecting the chart-grain size (diameter) of the analysis software with the entire cross section as the analysis target, and calculating the average grain size using the area method. More specifically, when the boundary where the orientation difference with adjacent measurement points is 15° or more is defined as the interface (grain boundary) of the crystal grain, the average diameter of the crystal grains can be determined as the circle-equivalent average diameter of the crystal grains when the cross-sectional area of ​​the crystal grains is calculated using the number of consecutive measurement points in the area surrounded by the grain boundary and the step size during measurement.

[0023] [2] Copper-based conductor material The copper-based conductor is made of copper or a copper alloy. Here, the copper-based conductor may be a copper alloy containing small amounts of elements such as silver (Ag), chromium (Cr), zirconium (Zr), or tin (Sn). However, to make the copper-based conductor easier to bend, it is preferably copper (Cu), more specifically, 99.00% by mass or more of pure copper. Among them, the higher the copper content, the higher the electrical conductivity. Therefore, tough pitch copper containing 99.90% by mass or more of copper (Cu) and unavoidable impurities is preferred, and oxygen-free copper containing 99.96% by mass or more of Cu and 10 ppm or less of oxygen and unavoidable impurities is even more preferred.

[0024] The copper alloy constituting the copper-based conductor preferably has an alloy composition containing at least one element of 0.1% by mass to 1.0% by mass of Ag, 0.1% by mass to 1.0% by mass of Cr, 0.1% by mass to 1.0% by mass of Zr, and 0.1% by mass to 1.0% by mass of Sn, with the remainder being Cu and unavoidable impurities.

[0025] When at least one of the contents of Ag, Cr, Zr, and Sn is 0.1% by mass or more, the tensile durability of the copper-based conductor can be improved. Therefore, even if the cross-sectional area of ​​the connection deformed by ultrasonic bonding is small, the electric wire can withstand the tensile load when handled without breaking. On the other hand, when at least one of the contents of Ag, Cr, Zr, and Sn exceeds 1.0% by mass, this can cause a decrease in the electrical conductivity of the copper-based conductor. Therefore, when using a copper-based conductor as an electric wire, it is preferable to add the above elements at low concentrations. From this perspective, when the copper alloy contains Ag, the upper limit of the Ag content is more preferably 0.7% by mass or less, and even more preferably 0.4% by mass or less. When the copper alloy contains Cr, the upper limit of the Cr content is more preferably 0.7% by mass or less, and even more preferably 0.4% by mass or less. When the copper alloy contains Zr, the upper limit of the Zr content is more preferably 0.7% by mass or less, and even more preferably 0.4% by mass or less. When the copper alloy contains Sn, the upper limit of the Sn content is more preferably 0.7 mass % or less, and even more preferably 0.4 mass % or less.

[0026] The remainder other than the above elements are unavoidable impurities. The unavoidable impurities refer to impurities at a level that is inevitably mixed in during the manufacturing process. Depending on the content of the unavoidable impurities, they may be a factor in reducing the conductivity of the copper-based conductor, so it is preferable that the content of the unavoidable impurities is small.

[0027] Examples of unavoidable impurities contained in copper-based conductors include elements such as aluminum (Al), beryllium (Be), cadmium (Cd), iron (Fe), magnesium (Mg), nickel (Ni), phosphorus (P), lead (Pd), silicon (Si), and titanium (Ti). Other examples of unavoidable impurities include small amounts of silver (Ag), chromium (Cr), zirconium (Zr), and tin (Sn) that do not satisfy the required contents of silver (Ag), chromium (Cr), zirconium (Zr), and tin (Sn) in the alloy composition of the copper alloy. The upper limit of the unavoidable impurity content is preferably 30 ppm or less in total of the above elements.

[0028] [3] Shape and uses of copper-based conductors The shape of the copper-based conductor is such that the cross-sectional shape perpendicular to the extension direction of the copper-based conductor is circular or approximately circular, and its size can be selected appropriately depending on the amount of current and installation space required in the electrical appliance or automobile to be installed.

[0029] When the copper-based conductor is made of a copper-based wire having a round wire shape, it is preferable that the diameter of the copper-based wire (round wire) is 0.13 mm or more, since a relatively high current can be passed through the copper-based wire. Also, it is preferable that the diameter of the copper-based wire (round wire) is 0.54 mm or less, since the copper-based conductor is easily deformed when ultrasonic waves are applied.

[0030] Furthermore, a stranded conductor can be formed by twisting together multiple copper-based wires made of the above-mentioned copper-based conductor, which can be easily bent, easily deformed when ultrasonic waves are applied, and has high bonding strength to a terminal. Here, the number of strands in the stranded conductor and the total cross-sectional area of ​​the stranded wire are not limited, but by twisting together copper-based conductors having the above-mentioned wire diameters in a number ranging from 7 to 171, it is possible to easily join terminals, etc. by ultrasonic bonding and to form a small-diameter stranded conductor that requires little installation space.

[0031] Furthermore, the copper-based conductor of the present invention is preferably used for an electric wire. More specifically, an electric wire can be formed by forming at least an insulating coating layer on the surface of the above-mentioned copper-based conductor or stranded conductor.

[0032] Here, the insulating coating layer is preferably a coating layer made of, for example, polyvinyl chloride, and the coating layer can be formed, for example, by extruding molten resin onto the surface of the copper-based conductor or the stranded conductor.

[0033] Furthermore, when the copper-based conductor according to the present invention is ultrasonically bonded to a terminal to obtain an electric wire with terminal, the height h of the joint is preferably in the range of 1 / 3 to 2 / 3, where the outer diameter (stranded outer diameter) of the stranded conductor before bonding is taken as 1. If the height h of the joint exceeds 2 / 3 of the stranded outer diameter, many voids that were present at the joint between the copper-based conductor and the terminal and inside the stranded conductor remain, reducing the tensile durability of the electric wire with terminal. Therefore, the height h of the joint is preferably 0.55 or less, and more preferably 0.45 or less, where the outer diameter (stranded outer diameter) of the stranded conductor before bonding is taken as 1. On the other hand, if the height h of the joint is less than 1 / 3 of the stranded outer diameter, the cross-sectional area of ​​the stranded conductor becomes small, making it difficult to pass a predetermined current through the electric wire with terminal. In this case, the reduced cross-sectional area of ​​the joint also tends to result in insufficient tensile durability. Therefore, when the outer diameter of the stranded conductor before joining (stranded outer diameter) is taken as 1, the height h of the joint is preferably 0.34 or more, and more preferably 0.38 or more.

[0034] Here, the height h of the joint can be defined as the maximum height of the stranded conductor 1 from the surface 2a of the flat portion 2 of the copper terminal when observing a vertical cross section perpendicular to the longitudinal direction of the stranded conductor 1 of the electric wire with terminal (the extension direction of the copper-based conductor 10), as shown in Fig. 1. In the stranded conductor 1 shown in Fig. 1, a plurality of copper-based conductors 10 are twisted together in a spiral shape to form multiple layers around a central conductor wire 11 made of a single copper-based conductor 10, and therefore the cross section of the copper-based conductor 10 in the spirally twisted portion is substantially elliptical.

[0035] Furthermore, when a copper-based conductor according to the present invention is ultrasonically bonded to a terminal so that the terminal extends on one side of the joint and the stranded conductor extends on the other side of the joint, and a tensile test is performed by grasping the terminal on one side and the stranded conductor on the other side according to JIS Z2241, the conductor does not break at the joint and preferably has a measured tensile strength of 70 MPa or more. Because the copper-based conductor and the terminal are strongly bonded in this type of electric wire with terminal, the electric wire with terminal can have high tensile durability. Therefore, the tensile strength of the electric wire with terminal is preferably 100 MPa or more, and more preferably 150 MPa or more.

[0036] The material of the terminal to be joined to the copper-based conductor according to the present invention is preferably copper or a copper alloy. Here, from the viewpoint of use in applications involving the flow of large currents, it is more preferable to use pure copper, which has high conductivity, as the material of the terminal. Furthermore, from the viewpoint of using the terminal as a fitting portion by utilizing the springiness of the terminal material, it is more preferable to use a copper alloy, which has high strength, as the material of the terminal. Here, the material of the terminal may be the same as the material of the copper-based conductor described above, or may be the same material as the copper-based conductor.

[0037] [4] An example of a manufacturing method for copper-based conductors Next, a method for manufacturing a copper-based conductor according to an embodiment will be described. In the method for manufacturing a copper-based conductor according to an embodiment, the copper-based conductor is isotropically processed in the radial direction, particularly in the wiredrawing process, and then a specific crystal orientation when viewed from a direction perpendicular to the longitudinal direction of the wire is controlled by two-stage current annealing in the subsequent first and second heat treatment processes, thereby making it possible to increase the total density, which is the ratio of the average value of the first and second total areas to the total area of ​​the crystal grains included in the first measurement region.

[0038] In the method for producing a copper-based conductor according to the embodiment, first, a casting step is performed in which electrolytic copper is melted in a reducing atmosphere to obtain a cylindrical ingot called a billet.

[0039] After the casting process, an extrusion process is carried out in which the billet is processed into a round bar by hot extrusion.

[0040] The extrusion process is followed by a wiredrawing process, in which the round bar or wire rod obtained in the above process is drawn to a predetermined wire diameter. Preferably, the wiredrawing process includes a peeling process to remove surface defects that have occurred up to the above process. If necessary, the wire may be subjected to one or more heat treatment processes before the wiredrawing process in order to remove processing strain and to facilitate wiredrawing.

[0041] When a stranded conductor is formed after the wire drawing process, a stranding process may be performed in which a plurality of drawn copper-based conductors are twisted together to form a stranded conductor. At this time, the conductor may be compressed using a compression die, or the copper-based conductors may be twisted together without being compressed using a compression die.

[0042] The copper-based conductor or the stranded conductor is then subjected to a heat treatment process. Here, the heat treatment process performed on the copper-based conductor or the stranded conductor includes a first heat treatment process and a second heat treatment process. This allows the total concentration ratio, which is the ratio of the average value of the first total area and the second total area to the total area of ​​the crystal grains included in the first measurement region, to be 40% or more.

[0043] In the first and second heat treatment steps, current annealing is performed, in which a current is passed through the wire passing through multiple pulleys that act as electrodes. By performing current annealing in the first and second heat treatment steps, the temperature of the copper-based conductor or the stranded conductor can be raised in a short time. Therefore, after a large number of small crystal grains are simultaneously generated by recrystallization in the first heat treatment step, these crystal grains can be grown in the second heat treatment step. Therefore, the ratio of the area of ​​the crystal grains to the total area of ​​the crystal grains included in the first measurement region is 1 / 2. <011> orientation group, <012> Orientation groups and <123> The proportion of the area of ​​crystal grains having the orientation group can be increased.

[0044] In the first heat treatment step and the second heat treatment step, the temperature and time for heating the copper-based conductor or the stranded conductor are set as desired. <011> orientation group, <012> Orientation groups and <123> It can be adjusted appropriately depending on characteristics such as the proportion of the area of ​​crystal grains having the orientation group.

[0045] For example, if the temperature at which the copper-based conductor or the stranded conductor is heated in the first heat treatment step is too high, the generation of crystal grains by recrystallization and the growth of the crystal grains occur simultaneously, resulting in a decrease in the proportion of the total area of ​​the crystal grains exposed in the cross section of the copper-based conductor. <011> orientation group, <012> Orientation groups and <123> The proportion of the area of ​​crystal grains having orientation groups is difficult to increase. Also, if the heating temperature in the first heat treatment step is too high, the crystal grains are likely to become larger than necessary. On the other hand, if the temperature at which the copper-based conductor or the stranded conductor is heated in the first heat treatment step is too low, atomic rearrangement due to heating and the generation of crystal grains by recrystallization are difficult to occur, so the proportion of the area of ​​the crystal grains that appear in the cross section of the copper-based conductor is <011> orientation group, <012> Orientation groups and <123> The proportion of the area of ​​crystal grains having orientation groups is less likely to increase. Here, by increasing the current flowing through the copper-based conductor or the stranded conductor in the first heat treatment step, the temperature to which the copper-based conductor or the stranded conductor is heated can be increased, and by decreasing the current flowing through the copper-based conductor or the stranded conductor in the first heat treatment step, the temperature to which the copper-based conductor or the stranded conductor is heated can be decreased.

[0046] Furthermore, if the copper-based conductor or the stranded conductor is heated for too long in the first heat treatment step, the crystal grains generated by recrystallization are likely to grow, and the proportion of the crystal grains in the total area exposed in the cross section of the copper-based conductor will be <011> orientation group, <012> Orientation groups and <123> In other words, by shortening the time for heating the copper-based conductor or the stranded conductor in the first heat treatment step, excessive growth of crystal grains can be suppressed, and therefore the proportion of the area of ​​the crystal grains that have orientation groups in the total area of ​​the crystal grains that appear in the cross section of the copper-based conductor is reduced. <011> orientation group, <012> Orientation groups and <123> The proportion of the area of ​​crystal grains having the orientation group can be increased.

[0047] In the subsequent second heat treatment process, if the temperature at which the copper-based conductor or the stranded conductor is heated is too low, the growth of the crystal grains generated by recrystallization will be difficult, and the proportion of the crystal grains in the total area of ​​the crystal grains exposed in the cross section of the copper-based conductor will be <011> orientation group, <012> Orientation groups and <123> It becomes difficult to increase the proportion of the area of ​​crystal grains having orientation groups. On the other hand, if the temperature at which the copper-based conductor or the stranded conductor is heated in the second heat treatment process is too high, excessive crystal grain growth will reduce deformation resistance, increasing the risk of wire breakage, which is undesirable. Here, by increasing the current flowing through the copper-based conductor or the stranded conductor in the second heat treatment process, the temperature at which the copper-based conductor or the stranded conductor is heated can be increased, and by decreasing the current flowing through the copper-based conductor or the stranded conductor in the second heat treatment process, the temperature at which the copper-based conductor or the stranded conductor is heated can be lowered.

[0048] In addition, by shortening the heating time of the copper-based conductor and the stranded conductor in the second heat treatment process, excessive growth of crystal grains can be suppressed, so that the proportion of the total area of ​​the crystal grains exposed in the cross section of the copper-based conductor is <011> orientation group, <012> Orientation groups and <123> On the other hand, by increasing the heating time of the copper-based conductor or the stranded conductor in the second heat treatment step, the crystal grains grow, and the proportion of the crystal grains in the total area of ​​the crystal grains exposed in the cross section of the copper-based conductor decreases. <011> orientation group, <012> Orientation groups and <123> The proportion of the area of ​​crystal grains having an orientation group is less likely to increase.

[0049] When current annealing is performed in the first and second heat treatment steps, the temperature of the copper-based conductor or stranded conductor may rise instantaneously, making it difficult to accurately grasp the temperature because the thermocouple's response speed cannot keep up. Therefore, when setting the heat treatment conditions for current annealing, a copper-based conductor with the desired total integration rate can be obtained by adjusting conditions such as voltage, current value, wire speed, and electrode distance based on the total integration rate of the actual copper-based conductor after the heat treatment step and the above description.

[0050] It is preferable to form an insulating coating layer on the surface of the stranded conductor thus obtained by extruding a molten resin, thereby producing an electric wire.

[0051] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention. [Example]

[0052] Next, in order to further clarify the effects of the present invention, examples of the present invention and comparative examples will be described, but the present invention is not limited to these examples of the present invention.

[0053] (Preparation of copper-based conductors A to H) A copper-based material composed of the components shown in Table 1 was subjected to casting, extrusion, and wiredrawing processes to form a roughly drawn wire with a wire diameter of 8 mm. This was then further subjected to wiredrawing to form a round wire with the wire diameter shown in Table 1. Subsequently, a first heat treatment process was performed under the conditions shown in Table 1. For copper-based conductor H, for which the type of heat treatment is "batch annealing," the heat treatment temperature was 500°C, and the holding time at the heat treatment temperature was 2 hours. For copper-based conductors A to F, for which the presence or absence of a second heat treatment process is marked "yes" in Table 1, the second heat treatment process was performed under the conditions shown in Table 1 to obtain copper-based conductors. For copper-based conductors G and H, for which the presence or absence of a second heat treatment process is marked "no," only the first heat treatment process was performed without the second heat treatment process to obtain copper-based conductors.

[0054] (Invention Examples 1 to 18 and Comparative Examples 1 to 6) A stranded conductor was obtained by a stranding step in which stranded wires made of copper-based conductors of the types shown in Tables 3, 4, and 5 among the copper-based conductors A to H obtained above were stranded together to form a stranded conductor. Then, an insulating coating layer made of polyvinyl chloride was formed on the surface of the obtained stranded conductor by extruding a molten resin made of polyvinyl chloride, thereby obtaining an electric wire.

[0055] [Various measurement and evaluation methods] The copper-based conductors and stranded conductors according to the present invention and comparative examples were used to evaluate the following characteristics. The evaluation conditions for each characteristic were as follows:

[0056] [1] Component analysis The rough wire obtained in the wire drawing process in the manufacturing stage described above was pressed into a flat plate, and the samples were measured and analyzed using an optical emission spectrometer (manufactured by Shimadzu Corporation). Measurements were performed three times, and the average values ​​were calculated and shown in Table 1. Elements that were intentionally added are listed in their respective columns, and if they were not intentionally added, these elements were included in the total of unavoidable impurities. Note that if the detected amount of a component was less than 0.001% by mass, the component was considered not to be contained, and this was indicated by "-" in the table.

[0057] [2] The proportion of the total area of ​​the crystal grains contained in the first measurement area, <011> orientation group, <012> Orientation groups and <123> Measurement of the total accumulation ratio of grains with orientation groups The proportion of the total area of ​​the crystal grains included in the first measurement region, <011> orientation group, <012> Orientation groups and <123> To measure the total accumulation ratio of the orientation groups, an EBSD detector (TSL, OIM5.0 HIKARI) attached to a high-resolution scanning analytical electron microscope (JEOL, JSM-7001FA) was used to continuously measure and collect EBSD patterns. The crystal orientation data obtained from the EBSD patterns was then analyzed using analysis software (TSL, OIM Analysis) to obtain crystal orientation analysis data. The measurement target was a mirror-finished cross section of a copper-based conductor (or a single copper-based conductor in the case of a stranded conductor) perpendicular to the longitudinal direction. The entire cross section was designated as the first measurement area. Measurements were performed with a step size of 0.5 μm. Next, two directions perpendicular to the longitudinal direction of the wire were selected on the IPF map to define an x-y Cartesian coordinate system. The first direction was defined as the x-axis direction, and the second direction was defined as the y-axis direction. In addition, from the chart-crystal direction obtained using analysis software, when the boundary where the difference in orientation between adjacent measurement points is 15° or more is defined as the interface (grain boundary) of the crystal grain, the set of consecutive measurement points in the range surrounded by the grain boundary is defined as a crystal grain, <011> Crystal orientation within ±8° <011> The orientation group is <012> Crystal orientation within ±8° <012> A directional group, and <123> Crystal orientation within ±8° <123> The orientation group was set as follows. At this time, for each of the first and second directions, the ratio of the area of ​​the crystal grains included in the first measurement region to the total area of ​​the crystal grains was <011> orientation group, <012> Orientation groups and <123> The area ratios (A1 to A3, A5 to A7) of the crystal grains having the orientation group are measured, and this measurement is performed three times at different locations within the first measurement area, and the average of the three measurements is calculated. <011> orientation group, <012> Orientation groups and <123> The total area ratio of the crystal grains having the orientation group was calculated as the total accumulation ratio (A4, A8). Then, the average of the total accumulation ratios for the first and second directions ((A4 + A8) / 2) was calculated from the measured values ​​of the total accumulation ratios (A4, A8) calculated for the first and second directions, and is shown in Table 2.

[0058] [3] The proportion of the total area of ​​the grains contained in the second measurement area, <011> orientation group, <012> Orientation groups and <123> Measurement of the total accumulation ratio of grains with orientation groups The proportion of the total area of ​​the crystal grains included in the second measurement area <011> orientation group, <012> Orientation groups and <123> The total concentration ratio of crystal grains having an orientation group is determined by taking the center of a circular cross section of a copper-based conductor when viewed in a transverse cross section, defining a concentric region with a diameter 1 / 3 of that of the first measurement region as the second measurement region, extracting data for the second measurement region from the crystal orientation data obtained by the electron backscatter diffraction (EBSD) method described above, and calculating the ratio of the area of ​​the crystal grains in the second measurement region to the total area of ​​the crystal grains in the first and second directions in the same manner as for the first measurement region. <011> orientation group, <012> Orientation groups and <123> The area ratio of crystal grains having the orientation group (B1 to B3, B5 to B7) is measured, and this measurement is performed three times at different locations within the first measurement area, and the average of the three measurements is calculated. <011> orientation group, <012> Orientation groups and <123> The total area ratio of the crystal grains having the orientation group was calculated as the total accumulation ratio (B4, B8). Then, the average of the total accumulation ratios for the first and second directions ((B4 + B8) / 2) was calculated from the measured values ​​of the total accumulation ratios (B4, B8) calculated for the first and second directions, and is shown in Table 2.

[0059] [4] Measurement of the average grain size of grains The average grain size of the crystal grains present in the cross section of the copper-based conductor was determined by analyzing the crystal orientation data using the electron backscatter diffraction (EBSD) method described above, selecting the chart-grain size (diameter) option in the analysis software with the entire cross section as the analysis target, and calculating the average grain size using the area method. The results are shown in Table 2.

[0060] [5] Evaluation of the joint height when ultrasonically joining a stranded conductor to a terminal For the electric wire with the twisted conductor obtained above, 40 mm of the coating material was stripped off from the twisted conductor, and a flat terminal with a width of 10 mm, a depth of 40 mm, and a thickness of 2 mm was prepared. The twisted conductor and the flat part of the copper terminal were brought into contact and ultrasonically bonded to obtain an electric wire with a terminal. The ultrasonic bonding was performed using ultrasonic waves with a frequency of 20 kHz for a bonding time of 0.4 seconds. At this time, the input energy of the ultrasonic waves was 3 sq (approximately 3.30 mm 2 ) is used, the value is 600J, and the cross-sectional area is 5 sq (approximately 5.23 mm 2 ) is used, the value is 1000J, and the cross-sectional area is 15sq (approximately 13.75mm 2 When a 3 sq electric wire is used, the value is 3000 J. Here, the unit sq means the area of ​​the conductor and is a unit used to express electric wires (for example, the cross-sectional area of ​​the stranded conductor in a 3 sq electric wire is approximately 3 mm 2 (It is).

[0061] Two such electric wires with terminals were produced, and parallel longitudinal cross sections along the longitudinal direction of the stranded conductor (extension direction of the copper-based conductor) were observed. The maximum height of the stranded conductor 1 from the surface 2a of the flat portion 2 of the copper terminal shown in Figure 1 was determined and taken as the height h of the joint. The average value of the height h of the joint of the two electric wires with terminals was taken as the measured value of the height h of the joint [mm].

[0062] When the measured value of the joint height h was between 1 / 3 and 2 / 3 of the outer diameter (stranded outer diameter) of the stranded conductor before splicing, the voids at the joint between the copper-based conductor and the terminal and inside the stranded conductor were small, and the copper-based conductor and terminal were well joined. This was evaluated as "Good (○)." On the other hand, when the measured value of the joint height h was more than 2 / 3 of the outer diameter (stranded outer diameter) of the stranded conductor before splicing, many voids at the joint between the copper-based conductor and the terminal and inside the stranded conductor remained, and the copper-based conductor and terminal were not well joined. This meant that the wire with terminal was poor. This was evaluated as "Poor (×)." Furthermore, when the measured height h of the joint was less than 1 / 3 of the outer diameter (stranded outer diameter) of the stranded conductor before joining, the cross-sectional area of ​​the stranded conductor was reduced, making it difficult to pass a predetermined current through the electric wire with terminal. Therefore, the electric wire with terminal was deemed unsuitable and evaluated as "× (poor)." In the examples of the present invention and the comparative examples, "◯" was evaluated as a pass level. The results are shown in Tables 3, 4, and 5.

[0063] [6] Tensile test and evaluation of terminal-attached wires The tensile strength of the electric wire with terminal was measured by preparing two test pieces of electric wire with terminal, which had a 10mm long joint where the terminal and the stranded conductor overlapped, with the terminal extending 40mm on one side of the joint and the stranded conductor extending 140mm on the other side of the joint. A tensile test was carried out on these test pieces by grasping the terminal on one side and the stranded conductor on the other side, with reference to JIS Z2241. The location where the electric wire with terminal broke was identified, and the tensile strength R m Calculate the tensile strength R of the two terminal-attached wires. m The average values ​​of these were taken as the measured tensile strength values ​​[MPa]. The tensile strength of the electric wire with terminal was calculated by dividing the force at which the electric wire with terminal broke in a tensile test by the cross-sectional area of ​​the stranded conductor before joining.

[0064] Regarding the results of the tensile test, if neither of the two electric wires with terminal broke at the joint and the measured tensile strength was 70 MPa or more, the copper-based conductor and the terminal were strongly joined, and the electric wire with terminal had high tensile durability. The test was evaluated as "Good (◯)." On the other hand, if at least one electric wire with terminal broke at the joint or the average tensile strength was less than 70 MPa, the test was evaluated as "Poor (×)." The test was evaluated as "Poor (×)." In the examples of the present invention and the comparative examples, "Good" was used as a passing grade. The results are shown in Tables 3, 4, and 5.

[0065] [7] Overall rating Of the two evaluation results, the height of the connection when the stranded conductor is ultrasonically bonded to the terminal and the results of the tensile test of the terminal-attached electric wire were evaluated as "Good," and the overall evaluation was evaluated as "Good," indicating that both the height of the connection with the terminal and the results of the tensile test of the terminal-attached electric wire were excellent. On the other hand, if at least one of the evaluation results, the height of the connection with the terminal and the results of the tensile test of the terminal-attached electric wire, was evaluated as "Poor," indicating that at least one of these two characteristics was insufficient, and the overall evaluation was evaluated as "Poor." The results are shown in Tables 3, 4, and 5.

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] [Table 4]

[0070] [Table 5]

[0071] As shown in Tables 1 to 5, in Examples 1 to 18 of the present invention, the percentage of the total area of ​​the crystal grains included in the first measurement region was <011> orientation group, <012> Orientation groups and <123> Because the area ratio of the crystal grains having the orientation group was controlled within a predetermined range, when the stranded conductor and the terminal were joined by ultrasonic bonding to form an electric wire with terminal, both the height of the connection with the terminal and the results of the tensile test of the electric wire with terminal were excellent. From this, in Examples 1 to 18 of the present invention, the copper-based conductor was easily deformed by applying ultrasonic waves to the copper-based conductor, reducing voids that were present at the joint between the copper-based conductor and the terminal and voids that were present inside the stranded conductor, thereby promoting the joining between the copper-based conductor and the terminal and further improving the tensile durability of the electric wire with terminal.

[0072] On the other hand, in Comparative Examples 1 to 6 and Inventive Examples 1 to 18, the proportion of the total area of ​​the crystal grains included in the first measurement region was <011> orientation group, <012> Orientation groups and <123> The area ratio of the crystal grains having the orientation group was not controlled within a predetermined range. Therefore, in Comparative Examples 1 to 6, when the electric wire with terminal was constructed by joining the stranded conductor and the terminal by ultrasonic bonding, at least one of the height of the connection part with the terminal and the results of the tensile test of the electric wire with terminal was poor. Therefore, the tensile durability of the electric wire with terminal was also poor in Comparative Examples 1 to 6. [Explanation of symbols]

[0073] 1 Stranded conductor 10 Copper-based conductors 11 Center conductor wire 2 Flat part of terminal 2a Surface of the flat plate h Height of the joint

Claims

1. A copper-based conductor, In a crystal orientation analysis performed by an electron backscatter diffraction (EBSD) method on a cross section perpendicular to the extension direction of the conductor, An x-y orthogonal coordinate system is defined within the transverse plane, and a first direction is assumed to be a direction on the x-axis, and a second direction is assumed to be a direction on the y-axis; When the crystal orientations within ±8° of the <011> orientation are defined as the <011> orientation group, the crystal orientations within ±8° of the <012> orientation are defined as the <012> orientation group, and the crystal orientations within ±8° of the <123> orientation are defined as the <123> orientation group, At a first measurement area selected within the cross-section, a first total area obtained by adding together the areas of crystal grains having the <011> orientation group, the <012> orientation group, and the <123> orientation group with respect to the first direction; and a second total area obtained by adding together the areas of crystal grains having the <011> orientation group, the <012> orientation group, and the <123> orientation group with respect to the second direction; a total integration rate, which is the ratio of the average value of the above to the total area of ​​crystal grains included in the first measurement region, is 40% or more.

2. When the cross section is divided into a central portion and an outer annular portion surrounding the central portion, At a second measurement area selected within the central portion of the cross-section, a first total area obtained by adding together the areas of crystal grains having the <011> orientation group, the <012> orientation group, and the <123> orientation group with respect to the first direction; and a second total area obtained by adding together the areas of crystal grains having the <011> orientation group, the <012> orientation group, and the <123> orientation group with respect to the second direction; 2. The copper-based conductor according to claim 1, wherein a total concentration ratio, which is a ratio of the average value of (a) to the total area of ​​crystal grains included in the second measurement region, is 50% or more.

3. The copper-based conductor according to claim 1 , wherein the average grain size of the grains present in the cross section is less than 20.0 μm.

4. A stranded conductor formed by twisting together a plurality of copper-based element wires made of the copper-based conductor according to claim 1.

5. An electric wire comprising the copper-based conductor according to claim 1, 2 or 3, or the stranded conductor according to claim 4, and at least an insulating coating layer formed on the surface thereof.

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