Cu-Ag ALLOY WIRE MATERIAL

Abstract

This Cu-Ag alloy wire material has an alloy composition containing 1.00 mass% to 6.00 mass% Ag, with the remainder being Cu and unavoidable impurities, and has a metal structure including a Cu alloy phase as the parent phase and a second phase precipitate containing an Ag phase. The tensile strength of the Cu-Ag alloy is 950 MPa or higher when the Ag content is at least 1.00 mass% but less than 1.50 mass%, is 1050 MPa or higher when the Ag content is at least 1.50 mass% but less than 3.00 mass%, is 1200 MPa or higher when the Ag content is at least 3.00 mass% but less than 5.00 mass%, and is 1450 MPa or higher when the Ag content is at least 5.00 mass% but no more than 6.00 mass%. When, in a transverse section, the linear distance from the surface to the center is noted as L, the value (c1-c2) obtained by subtracting the average Ag concentration c2 in a central region ranging from the center toward the surface, covering a length 99L / 100, from the average Ag concentration c1 in a surface annular region ranging from the surface toward the center, covering a length L / 100, is at least 1.00 mass% but no more than 3.00 mass%.

Description

Cu-Ag alloy wire

[0001] The present disclosure relates to a Cu—Ag-based alloy wire.

[0002] The diameter of wires used in electrical and electronic equipment is becoming thinner and thinner, and instead of pure copper wires, which lack strength, copper alloy wires such as Cu-Sn, Cu-Cr, and Cu-Ag are being used.

[0003] As electronic devices become increasingly dense and compact, there is a trend toward thinner wires for connecting electrical and electronic devices, speaker coils, etc. Among copper alloys, Cu-Ag alloys have excellent strength and conductivity, and a good balance of these properties.

[0004] For example, in the Cu-Ag alloy wire of Patent Document 1, the eutectic phase of Cu and Ag is stretched into a filament shape, achieving high strength and high conductivity. In particular, Patent Document 1 discloses a technique for developing a recrystallized texture through heat treatment during the process and then increasing strength through subsequent intensive processing. However, Patent Document 1 does not perform an appropriate wiredrawing process before heat treatment, which leads to material embrittlement during heat treatment, making wire thinning difficult and resulting in poor productivity, making it difficult to produce a cost-competitive product. In addition, no consideration has been given to improving the resistance to fatigue fracture (flexural fatigue resistance) of thinner Cu-Ag alloy wires under repeated bending conditions.

[0005] Patent No. 5051647

[0006] An object of the present disclosure is to provide a Cu—Ag alloy wire that has high tensile strength and high electrical conductivity, and also has excellent resistance to bending fatigue.

[0007] [1] An alloy having an alloy composition containing 1.00 mass% or more and 6.00 mass% or less of Ag, with the balance being Cu and inevitable impurities, and having a metal structure including a Cu alloy phase as a parent phase and a second phase precipitate including an Ag phase, wherein the tensile strength is 950 MPa or more when the Ag content is 1.00 mass% or more and less than 1.50 mass%, 1050 MPa or more when the Ag content is 1.50 mass% or more and less than 3.00 mass%, and 1200 MPa or more when the Ag content is 3.00 mass% or more and less than 5.00 mass%, [2] A Cu-Ag alloy wire rod having a compressive strength of 1,450 MPa or more when it contains 5.00% by mass or more and 6.00% by mass or less of Ag, and wherein, in a cross section, where L is the linear distance from the surface to the center, the difference (c1-c2) between the average Ag concentration c1 in a surface annular region extending from the surface to the center over a length L / 100, and the average Ag concentration c2 in a central region extending from the center to the surface over a length of 99L / 100, is 1.00% by mass or more and 3.00% by mass or less. [2] A STEM dark-field image of the cross section is grayscaled, and the low-brightness side is binarized to white and the high-brightness side is binarized to black, and the average number density n2 (numbers / μm ２ ) to the average number density n1 (number / μm ２ ) is 2.0 or more and 6.0 or less. [3] The Cu—Ag alloy wire according to the above [1] or [2], wherein the alloy composition further contains one or more elements selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr, and Cr in a total amount of 0.05 mass% or more and 0.30 mass% or less. [4] The Cu—Ag alloy wire according to any one of the above [1] to [3], wherein the Cu—Ag alloy wire is a round wire having a diameter of 0.01 mm or more and 0.08 mm or less. [5] The Cu—Ag-based alloy wire according to any one of [1] to [3] above, wherein the Cu—Ag-based alloy wire is a ribbon wire having a width of 0.020 mm or more and 0.320 mm or less and a thickness of 0.002 mm or more and 0.040 mm or less.

[0008] According to the present disclosure, it is possible to provide a Cu—Ag alloy wire that has high tensile strength and high electrical conductivity, and also has excellent resistance to bending fatigue.

[0009] Fig. 1 is a schematic diagram illustrating a surface annular region and a central region in a cross section of a Cu—Ag alloy wire (round wire) according to an embodiment. Fig. 2 is a schematic diagram illustrating a surface annular region and a central region in a cross section of a Cu—Ag alloy wire (ribbon wire) according to an embodiment. Fig. 3 is a diagram illustrating the counting of the number of black portions in a binarized image obtained from an STEM dark-field image of the Cu—Ag alloy wire according to Example 1.

[0010] The embodiments will be described in detail below.

[0011] As a result of extensive research, the inventors have found that a Cu—Ag alloy wire rod has high tensile strength and high electrical conductivity, and also has excellent bending fatigue resistance, by having a predetermined alloy composition and controlling the relationship between the average Ag concentration c1 in the surface annular region of the cross section and the average Ag concentration c2 in the central region, and by controlling the tensile strength within a predetermined range for a predetermined alloy composition, and the relationship between the average Ag concentration c1 in the surface annular region of the cross section and the average Ag concentration c2 in the central region, and the tensile strength within a predetermined range for a predetermined alloy composition, and have completed the present disclosure based on this finding.

[0012] The Cu-Ag alloy wire rod of the embodiment has an alloy composition containing 1.00 mass% or more and 6.00 mass% or less of Ag, with the balance being Cu and unavoidable impurities, and has a metal structure including a Cu alloy phase as a matrix and second-phase precipitates including an Ag phase. The tensile strength is 950 MPa or more when the alloy wire rod contains 1.00 mass% or more and less than 1.50 mass% of Ag, and 1050 MPa or more when the alloy wire rod contains 1.50 mass% or more and less than 3.00 mass% of Ag, and 1050 MPa or more when the alloy wire rod contains 3.00 mass% or more and less than 5.00 mass% of Ag. and 1450 MPa or more when the Ag content is 5.00% by mass or more and 6.00% by mass or less. In a cross section, when the linear distance from the surface to the center is L, the difference (c1-c2) between the average Ag concentration c1 in a surface annular region extending from the surface to the center by a length of L / 100, and the average Ag concentration c2 in a central region extending from the center to the surface by a length of 99L / 100, is 1.00% by mass or more and 3.00% by mass or less.

[0013] First, the alloy composition of the Cu--Ag alloy wire will be described.

[0014] The Cu—Ag alloy wire rod of the above embodiment has an alloy composition containing 1.00 mass % to 6.00 mass % of Ag, with the balance being Cu and unavoidable impurities.

[0015] <Ag: 1.00% by mass or more and 6.00% by mass or less> Ag (silver) is an element necessary for increasing the tensile strength of Cu—Ag-based alloy wire, and the Ag content is 1.00% by mass or more and 6.00% by mass or less. When the Ag content is 1.00% by mass or more, the tensile strength of the Cu—Ag-based alloy wire can be increased due to solid solution and precipitation of Ag. Furthermore, when the Ag content is 6.00% by mass or less, a decrease in the electrical conductivity of the Cu—Ag-based alloy wire can be suppressed, and the high electrical conductivity of the Cu—Ag-based alloy wire can be maintained. Furthermore, when the Ag content exceeds 6.00% by mass, it is not possible to expect an increase in strength that is commensurate with the increase in material costs due to the increased amount of Ag used, making it difficult to contribute to adding value to customers' products. In order to achieve a balance between improving the tensile strength and improving the electrical conductivity of the Cu—Ag-based alloy wire, the Ag content is 1.00 mass% or more, preferably 1.50 mass% or more, and on the other hand, 6.00 mass% or less, preferably 4.00 mass% or less.

[0016] <Auxiliary Components of Cu—Ag-Based Alloy Wire: 0.05% by Mass or More and 0.30% by Mass or Less> The alloy composition of the Cu—Ag-based alloy wire may further contain one or more elements selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr, and Cr in a total amount of 0.05% by mass or more and 0.30% by mass or less. That is, the Cu—Ag-based alloy wire may contain, in addition to Ag, an essential basic component, one or more optional auxiliary components selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr, and Cr in a total amount of 0.05% by mass or more and 0.30% by mass or less. When the auxiliary component content is 0.05% by mass or more, the tensile strength properties of the Cu—Ag-based alloy wire are improved, and some elements have the effect of reducing the brittleness of the Cu—Ag-based alloy wire. Furthermore, when the content of the auxiliary component is 0.30 mass% or less, the electrical conductivity of the Cu—Ag-based alloy wire is not significantly impaired. Therefore, the content of the auxiliary component is preferably 0.05 mass% or more, more preferably 0.08 mass% or more, and even more preferably 0.10 mass% or more, while being preferably 0.30 mass% or less, more preferably 0.25 mass% or less, and even more preferably 0.20 mass% or less.

[0017] <Sn: 0.05% by mass or more and 0.20% by mass or less> A Sn (tin) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag-based alloy wire, and a Sn content of 0.20% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag-based alloy wire. Therefore, the Sn content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.20% by mass or less, more preferably 0.18% by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12% by mass or less.

[0018] <Mg: 0.05% by mass or more and 0.20% by mass or less> A magnesium (Mg) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag alloy wire and has the effect of mitigating the brittleness of the Cu—Ag alloy wire. A magnesium content of 0.20% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag alloy wire or its manufacturability during casting. Therefore, the magnesium content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.20% by mass or less, more preferably 0.18% by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12% by mass or less.

[0019] <Zn: 0.05% by mass or more and 0.30% by mass or less> A Zn (zinc) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag alloy wire and has the effect of mitigating the brittleness of the Cu—Ag alloy wire. A Zn content of 0.30% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag alloy wire. Therefore, the Zn content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.30% by mass or less, more preferably 0.25% by mass or less, even more preferably 0.20% by mass or less, and particularly preferably 0.15% by mass or less.

[0020] <In: 0.05% by mass or more and 0.20% by mass or less> An In (indium) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag-based alloy wire, and an In content of 0.20% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag-based alloy wire. Therefore, the In content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.20% by mass or less, more preferably 0.18% by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12% by mass or less.

[0021] <Ni: 0.05% by mass or more and 0.30% by mass or less> A Ni (nickel) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag alloy wire. A Ni content of 0.30% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag alloy wire. Therefore, the Ni content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.30% by mass or less, more preferably 0.25% by mass or less, even more preferably 0.20% by mass or less, and particularly preferably 0.15% by mass or less.

[0022] <Co: 0.05% by mass or more and 0.20% by mass or less> A Co (cobalt) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag alloy wire, and a Co content of 0.20% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag alloy wire. Therefore, the Co content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.20% by mass or less, more preferably 0.18% by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12% by mass or less.

[0023] <Zr: 0.05% by mass or more and 0.20% by mass or less> A Zr (zirconium) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag alloy wire and has the effect of mitigating the brittleness of the Cu—Ag alloy wire. A Zr content of 0.20% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag alloy wire or its manufacturability during casting. Therefore, the Zr content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while preferably 0.20% by mass or less, more preferably 0.18% by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12% by mass or less.

[0024] <Cr: 0.05% by mass or more and 0.20% by mass or less> A Cr (chromium) content of 0.05% by mass or more contributes to improving the tensile strength of the Cu—Ag-based alloy wire, and a Cr content of 0.20% by mass or less does not significantly impair the electrical conductivity of the Cu—Ag-based alloy wire. Therefore, the Cr content is preferably 0.05% by mass or more, more preferably 0.07% by mass or more, even more preferably 0.08% by mass or more, and particularly preferably 0.10% by mass or more, while being preferably 0.20% by mass or less, more preferably 0.18% by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12% by mass or less.

[0025] <Balance: Cu and Inevitable Impurities> The balance other than the above-mentioned components is Cu (copper) and inevitable impurities. Inevitable impurities are inevitably mixed in during the manufacturing process, and depending on the content, they may cause a decrease in one or more of the tensile strength, electrical conductivity, and flexural fatigue resistance of the Cu—Ag-based alloy wire, affect the environment, and cause material embrittlement. Therefore, the lower the content of inevitable impurities, the better. Examples of inevitable impurities include elements such as S, Pb, Sb, and Bi. The upper limit of the content of the inevitable impurities is preferably less than 0.0001% by mass for each element, and preferably less than 0.0005% by mass for the total of the elements.

[0026] The Cu-Ag alloy wire is a copper alloy wire having a metal structure including a Cu alloy phase as a parent phase and second-phase precipitates including an Ag phase. The second-phase precipitates are precipitated in the Cu alloy phase as a parent phase and are composed of an Ag phase (single Ag phase) and the like.

[0027] FIG. 1 is a schematic diagram illustrating a surface annular region and a central region in a cross section of a Cu—Ag alloy wire (round wire) according to an embodiment. FIG. 2 is a schematic diagram illustrating a surface annular region and a central region in a cross section of a Cu—Ag alloy wire (ribbon wire) according to an embodiment. As shown in FIGS. 1 and 2 , in a cross section of the Cu—Ag alloy wire 1, which is a cross section perpendicular to the longitudinal direction of the Cu—Ag alloy wire 1, when the linear distance from the surface 1a of the Cu—Ag alloy wire 1 to the center 1b of the Cu—Ag alloy wire 1 is L, the region from the surface 1a toward the center 1b for a length L / 100 is defined as the surface annular region R1, and the region from the center 1b toward the surface 1a for a length 99L / 100 is defined as the central region R2. The difference (c1−c2) between the average Ag concentration c1 in the surface annular region R1 and the average Ag concentration c2 in the central region R2 is 1.00% by mass or more and 3.00% by mass or less.

[0028] When the cross section of the Cu—Ag alloy wire 1 is a perfect circle, the linear distance L from the surface 1a to the center 1b is constant, the surface annular region R1 is annular, and the center region R2 is a perfect circle. When the cross section of the Cu—Ag alloy wire 1 is not a perfect circle, the linear distance L from the surface 1a to the center 1b is not constant. For example, when the cross section of the Cu—Ag alloy wire 1 is rectangular as shown in FIG. 2, the linear distance L is not constant, the surface annular region R1 is rectangular annular, and the center region R2 is rectangular.

[0029] When the value (c1-c2) is within the above range, the tensile strength and bending fatigue resistance of the Cu-Ag alloy wire can be improved. In particular, when the Cu-Ag alloy wire is bent, stronger stress is applied to the surface of the Cu-Ag alloy wire than to the center of the Cu-Ag alloy wire. Therefore, when the value (c1-c2) is 1.00 mass% or more, the amount of Ag solid solution in the surface annular region R1 is increased, thereby improving the tensile strength of the Cu-Ag alloy wire. Furthermore, when the value (c1-c2) is 3.00 mass% or less, a decrease in the tensile strength of the Cu-Ag alloy wire due to a lack of Ag solid solution in the center region R2 can be suppressed, and breakage of the Cu-Ag alloy wire can be suppressed.

[0030] Furthermore, when the alloy composition contains 1.00 mass% or more but less than 1.50 mass% Ag, the tensile strength of the Cu—Ag alloy wire is 950 MPa or more, preferably 1050 MPa or more. When the alloy composition contains 1.50 mass% or more but less than 3.00 mass% Ag, the tensile strength of the Cu—Ag alloy wire is 1050 MPa or more, preferably 1150 MPa or more. When the alloy composition contains 3.00 mass% or more but less than 5.00 mass% Ag, the tensile strength of the Cu—Ag alloy wire is 1200 MPa or more, preferably 1300 MPa or more. When the alloy composition contains 5.00 mass% or more but less than 6.00 mass% Ag, the tensile strength of the Cu—Ag alloy wire is 1450 MPa or more, preferably 1550 MPa or more.

[0031] When the tensile strength of the Cu—Ag alloy wire is within the above range, even if the Cu—Ag alloy wire is an ultra-fine wire having a diameter even smaller than that of conventional wires, the tensile strength, electrical conductivity, and bending fatigue resistance can all be achieved in a well-balanced manner at a high level.

[0032] In addition, in the binarized image in which the STEM dark field image of the cross section of the Cu—Ag alloy wire 1 shown in FIGS. 1 and 2 is grayscaled and the low brightness side is binarized to white and the high brightness side to black, the average number density n2 (number / μm ２ ) the average number density n1 (number / μm ２ ) is preferably 2.0 or more and 6.0 or less.

[0033] During wire drawing in the manufacturing method of Cu—Ag alloy wire, black areas in the binarized image (hereinafter simply referred to as black areas) are formed as high-density fibrous precipitates, thereby further improving tensile strength. When the ratio (n1 / n2) is within the above range, the tensile strength and bending fatigue resistance of the Cu—Ag alloy wire can be further improved. In particular, when a Cu—Ag alloy wire is bent, stronger stress is applied to the surface of the Cu—Ag alloy wire than to the center of the Cu—Ag alloy wire. Therefore, when the ratio (n1 / n2) is 2.0 or more, the tensile strength of the Cu—Ag alloy wire can be further improved by increasing the number of black areas in the surface annular region R1, and the bending fatigue resistance can be further improved by increasing the strength of the Cu—Ag alloy wire surface. Furthermore, when the ratio (n1 / n2) is 6.0 or less, a decrease in the tensile strength of the Cu—Ag alloy wire due to a lack of black areas in the center region R2 can be suppressed.

[0034] The Cu—Ag alloy wire is preferably a round wire having a diameter of 0.01 mm or more and 0.08 mm or less. In this case, the cross section of the Cu—Ag alloy wire is circular and has a diameter of 0.01 mm or more and 0.08 mm or less. Even if the Cu—Ag alloy wire is a round wire having a wire diameter within the above range, i.e., an ultrafine round wire, it has high tensile strength and high electrical conductivity and also has excellent bending fatigue resistance.

[0035] The Cu—Ag alloy wire may also be a ribbon wire having a width of 0.020 mm to 0.320 mm and a thickness of 0.002 mm to 0.040 mm. In this case, the cross section of the Cu—Ag alloy wire is ribbon-shaped (rectangular) with long sides of 0.020 mm to 0.320 mm and short sides of 0.002 mm to 0.040 mm. Even if the Cu—Ag alloy wire is a ribbon wire having a size within the above range, i.e., an ultra-fine ribbon wire, it has high tensile strength and high electrical conductivity, and also has excellent bending fatigue resistance.

[0036] The tensile strength, electrical conductivity, and bending fatigue resistance of the Cu—Ag alloy wire in ribbon wire form are not significantly different from the tensile strength, electrical conductivity, and bending fatigue resistance of the Cu—Ag alloy wire in round wire form before being formed into a ribbon. In other words, if the tensile strength, electrical conductivity, and bending fatigue resistance of the Cu—Ag alloy wire in ribbon wire form are equal to or greater than predetermined values, the tensile strength, electrical conductivity, and bending fatigue resistance of the Cu—Ag alloy wire in ribbon wire form are equal to or greater than predetermined values.

[0037] Thus, Cu-Ag alloy wire rods have high tensile strength and high electrical conductivity, and also have excellent resistance to bending fatigue, making them suitable for use in connection cables for electrical and electronic devices. This makes it easier to miniaturize electrical and electronic devices, reduce the space required for installing electric wires, and increase the number of signal wiring lines, which have not been easy to achieve until now, and contributes to adding high value to the miniaturization of electrical and electronic products.

[0038] Next, a method for producing a Cu--Ag alloy wire will be described.

[0039] In the manufacturing method of Cu—Ag alloy wire, a casting process is first carried out in which raw materials are melted, cast, and rolled to obtain a wire rod having a predetermined alloy composition. The cooling rate during casting and solidification in the casting process is 10°C / s or more and 100°C / s or less. If the cooling rate exceeds 100°C / s, the flow of unsolidified molten metal into gaps in the surface layer that has solidified first does not proceed effectively, and the value (c1-c2) of the finally obtained Cu—Ag alloy wire becomes less than 1.00 mass%, and even if the heat treatment process described below is performed, the ratio (n1 / n2) becomes less than 2.00 mass%. On the other hand, if the cooling rate is less than 10°C / s, the value (c1-c2) of the Cu—Ag alloy wire becomes more than 3.00 mass%, which is undesirable from the viewpoints of productivity and quality maintenance.

[0040] After the casting step, a first wiredrawing step is carried out, in which cold wiredrawing is carried out at a processing rate of 50% or more and 90% or less. If the processing rate is less than 50%, a sufficient amount of fine black portions will not crystallize in the heat treatment step described below. Furthermore, if the processing rate is less than 50%, there is also the problem of void defects growing. On the other hand, if the processing rate is more than 90%, it is difficult to perform wiredrawing at a high processing rate in the second wiredrawing step described below. Therefore, from the viewpoints of promoting the crystallization of a sufficient amount of fine black portions, suppressing void growth, and further ensuring sufficient room for wiredrawing in the subsequent second wiredrawing step, the first wiredrawing step is carried out at a processing rate of 50% or more and 90% or less.

[0041] Here, the working ratio is a value obtained by subtracting the cross-sectional area of ​​the sample after wiredrawing from the cross-sectional area of ​​the sample before wiredrawing, dividing the result by the cross-sectional area of ​​the sample before wiredrawing, and multiplying the result by 100, expressed as a percentage, and is expressed by the following formula.

[0042] [Working rate] = {([Cross-sectional area of ​​sample before wiredrawing] - [Cross-sectional area of ​​sample after wiredrawing]) / [Cross-sectional area of ​​sample before wiredrawing]} x 100 (%)

[0043] The first wiredrawing step can be performed by a known method such as a wiredrawing process using a die. The first wiredrawing process may be performed in one pass, or may be performed in multiple passes until the desired wire diameter is obtained.

[0044] After the first wiredrawing step, a heat treatment step, generally called aging heat treatment, is performed for the purpose of crystallizing the black portion. The heat treatment step is performed at a holding temperature of 300°C to 400°C for a holding time of 10 seconds to 30 minutes, preferably 5 minutes to 30 minutes. If the holding temperature is less than 300°C or the holding time is less than 10 seconds, the generation of the black portion does not occur sufficiently. On the other hand, if the holding temperature exceeds 400°C, diffusion is promoted, and the value (c1 - c2) becomes less than 1.00 mass%. In addition, a longer holding time in the heat treatment step also promotes solute precipitation and diffusion. If the holding time is 10 seconds to 5 minutes, significant precipitation progresses in the wire surface layer, and the ratio (n1 / n2) becomes 2.0 or more. If the holding time is 5 minutes to 30 minutes, the ratio (n1 / n2) becomes 2.0 or more and precipitation becomes active throughout the wire, thereby increasing the tensile strength. If the retention time exceeds 30 minutes, diffusion proceeds, and the value (c1-c2) becomes less than 1.00 mass %.

[0045] The heat treatment step can be carried out by using a known method, such as batch heat treatment, high frequency heating, resistance heating, or continuous heat treatment such as running heating.

[0046] In addition, when a heat treatment or aging heat treatment is performed at a temperature higher than the above-mentioned holding temperature, a solution treatment (generally 700 to 900°C, 10 minutes to 5 hours) that is generally performed thereafter is not preferable because it makes it difficult to obtain a metal structure that satisfies the requirements of the Cu—Ag-based alloy wire rod of the embodiment. In addition, such a treatment is not preferable because it may release segregation and promote the growth of void defects.

[0047] Following the heat treatment step, the wire is cooled and then subjected to a second wiredrawing step in which cold drawing is performed at a processing ratio of 99.700% or more and 99.998% or less. If the processing ratio is less than 99.700%, the tensile strength does not increase sufficiently. On the other hand, it is technically difficult to achieve a processing ratio of more than 99.998%. Therefore, the second wiredrawing step is performed at a processing ratio of 99.700% or more and 99.998% or less.

[0048] The second wiredrawing step can be performed by a known method such as a drawing process using a die. The second wiredrawing process can be performed in one pass, or multiple passes until the desired wire diameter is obtained. In this way, a round Cu—Ag alloy wire can be produced.

[0049] Furthermore, although the above-described manufacturing method is primarily a method for manufacturing round wire, a Cu—Ag-based alloy wire rod in the form of a ribbon wire can be manufactured by rolling the round wire manufactured by the above-described manufacturing method to a specified thickness.

[0050] According to the embodiment described above, by controlling the relationship between the average Ag concentration c1 in the surface annular region of the cross section and the average Ag concentration c2 in the central region and the tensile strength within a predetermined range within a predetermined alloy composition, a Cu-Ag alloy wire having high tensile strength and high electrical conductivity as well as excellent bending fatigue resistance can be obtained.

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

[0052] Next, examples and comparative examples will be described, but the present disclosure is not limited to these examples.

[0053] (Examples 1-1 to 1-11, 2-1 to 2-11, 3-1 to 3-11, 4-1 to 4-11, 5-1 to 5-8 and Comparative Examples 1-1 to 1-6, 2-1 to 2-6, 3-1 to 3-6, 4-1 to 4-6, 5-1) A casting process was performed in which raw materials were melted in the air, cast, and rolled to obtain rough wires having diameters of 6 to 39 mm so as to obtain the alloy compositions shown in Tables 1 to 5. In the casting process, the cooling rate during casting and solidification was controlled to the value shown in Tables 1 to 5. Next, this rough wire was cold drawn at the working ratios shown in Tables 1 to 5 to obtain wire diameters of 4 to 9 mm. Next, heat treatment was performed at the holding temperatures and holding times shown in Tables 1 to 5. Note that Comparative Examples 1-2, 2-2, 3-2, 4-2, and 5-1 were not subjected to heat treatment. After cooling, the wires were cold drawn at the working ratios shown in Tables 1 to 5 to obtain round Cu-Ag alloy wires having diameters shown in Tables 6 to 10.

[0054] (Examples 1-12, 2-12, 3-12, 4-12) A casting process was performed in which raw materials were melted in the air, cast, and rolled to obtain rough-drawn wires having diameters of 6 to 39 mm so as to obtain the alloy compositions shown in Tables 1 to 4. In the casting process, the cooling rate during casting solidification was controlled to the value shown in Tables 1 to 4. Next, this rough-drawn wire was cold drawn at the working ratios shown in Tables 1 to 4 to obtain wire diameters of 4 to 9 mm. Next, heat treatment was performed at the holding temperatures and holding times shown in Tables 1 to 4. After cooling, cold drawing was performed at the working ratios shown in Tables 1 to 4 to obtain round Cu—Ag alloy wires. Next, the round Cu—Ag alloy wires were rolled to obtain ribbon Cu—Ag alloy wires having thicknesses and widths shown in Tables 6 to 9.

[0055] In the tables below, the data on which the comparative examples are based are underlined and italicized.

[0056]

[0057]

[0058]

[0059]

[0060]

[0061] [Evaluation] The Cu—Ag alloy wires obtained in the above examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Tables 6 to 10.

[0062] [1] Tensile strength Using the Cu—Ag-based alloy wires (two wires, n=2) obtained in the above examples and comparative examples, a tensile test was performed in accordance with JIS Z 2241:2011, and the tensile strength was calculated by averaging the two measured values.

[0063] [2] Flexural Fatigue Resistance Using the Cu—Ag alloy wires obtained in the above Examples and Comparative Examples, a repeated bending test was carried out in accordance with JIS H 0500 No. 4100. Specifically, since fatigue properties depend on the wire diameter, for Cu—Ag alloy wires with a wire diameter of less than 0.03 mm, Cu—Ag alloy wires with a wire diameter of more than 0.03 mm, and Cu—Ag alloy wires in ribbon wire form, the wire diameters of Cu—Ag alloy wires in the middle of processing were standardized to 0.03 mm, so that the wire diameters of the Cu—Ag alloy wires used in the repeated bending test were standardized to 0.03 mm.

[0064] A round Cu—Ag alloy wire having a wire diameter of 0.03 mm was used as the test subject. The radius R of the jig at the bending fulcrum when bending the Cu—Ag alloy wire was 6 mm. One end of the Cu—Ag alloy wire was fixed to a grip, and a 30 g weight was hung from the other end of the Cu—Ag alloy wire to prevent it from bending. The number of times until the Cu—Ag alloy wire broke was measured, and the average value (average flex life, n=5) was evaluated based on whether or not it satisfied the relationships of the following formulas 1 to 3.

[0065] If the average flex life value satisfies the following formula 1, the flex fatigue resistance is deemed to be very excellent and is rated as "Excellent." If formula 1 is not satisfied but formula 2 is satisfied, the flex fatigue resistance is deemed to be excellent and is rated as "Excellent." If formulas 1 and 2 are not satisfied but formula 3 is satisfied, the flex fatigue resistance is deemed to be good and is rated as "Good." If none of formulas 1 to 3 are satisfied, the flex fatigue resistance is deemed to be poor and is rated as "Fail."

[0066] Formula 1: Average flex life ≥ 5900 × (Ag concentration in alloy composition) + 40000 Formula 2: Average flex life ≥ 5900 × (Ag concentration in alloy composition) + 20000 Formula 3: Average flex life ≥ 5900 × (Ag concentration in alloy composition) + 5000

[0067] [3] Electrical conductivity Using the Cu—Ag-based alloy wires (n=2) obtained in the above examples and comparative examples, measurements were carried out based on JIS H0505:1975, and the electrical conductivity was calculated by averaging the two measured values.

[0068] [4] Average Ag concentration The Cu—Ag alloy wires obtained in the above examples and comparative examples were thinned by a focused ion beam (FIB) method on a cross section perpendicular to the longitudinal direction of the sample. A SIINT-3050TB (manufactured by SII NanoTechnology Inc.) was used for the processing, and the acceleration voltage of the Ga ion beam was set to 30 kV. After processing, Ar ion milling was performed on the sample surface at an acceleration voltage of 2 kV for 5 minutes to remove damage to the sample. Thus, a sample for observation was obtained.

[0069] Using an atomic resolution analytical electron microscope (JEOL ARM: JEM-ARM200F) with aberration correction, the surface annular region and the central region of the sample were observed with an electron beam acceleration voltage of 200 kV and an observation area of ​​a square with sides of 130 nm. High-angle annular dark field scanning TEM (HAADF-STEM) images (STEM dark-field images) of the surface annular region and the central region were obtained. Three locations were randomly selected on the surface of the sample for observation as the observation areas for the surface annular region and the central region. Energy dispersive X-ray spectroscopy (EDX) attached to the STEM was then performed on each STEM dark-field image to measure the Ag concentration in the surface annular region and the Ag concentration in the central region. The three measurements were averaged to calculate the average Ag concentration c1 in the surface annular region and the average Ag concentration c2 in the central region, respectively.

[0070] [5] Average number density of black portions Using the image processing software "Image J (version v1.53k)," the following processing was performed on each of the STEM dark-field images obtained above to calculate the average number density of black portions. First, a 400 nm ２ ~800nm ２An arbitrary range of the image was trimmed, and the trimmed image (trimmed image) was converted to grayscale. Next, in the histogram of brightness values ​​of the grayscaled image, the upper 0.5 to 2.0% was used as a threshold, and the low-brightness side was binarized as white and the high-brightness side as black. Furthermore, black areas of 1 pixel or less were removed as noise, and the remaining black areas were counted, with each area with a continuous outline considered to be a single black area. The number density of black areas was calculated by dividing the counted number of black areas by the area of ​​the trimmed image. The three measured values ​​were then averaged to obtain the average number density n1 of black areas in the surface annular region and the average number density n2 of black areas in the central region.

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] An STEM dark-field image of the Cu—Ag alloy wire obtained in Example 1 is shown in Figure 3. As shown in Tables 1 to 10 and Figure 3, the Cu—Ag alloy wires of the above examples had alloy compositions within the specified ranges, the relationship between the average Ag concentration c1 in the surface annular region and the average Ag concentration c2 in the central region was within the specified range, and the tensile strength within the specified range of alloy composition was also within the specified range. Therefore, both the tensile strength and electrical conductivity were high and the bending fatigue resistance was excellent. On the other hand, the Cu—Ag alloy wires of the above comparative examples had poor tensile strength, electrical conductivity, and bending fatigue resistance because at least one of the alloy composition, the relationship between the average Ag concentration c1 and the average Ag concentration c2, and the tensile strength within the specified range of alloy composition was outside the specified range.

[0077] 1 Cu-Ag alloy wire 1a Surface of Cu-Ag alloy wire 1b Center of Cu-Ag alloy wire L Distance from the surface of Cu-Ag alloy wire to the center of Cu-Ag alloy wire R1 Surface annular region R2 Center region

Claims

1. An alloy composition containing 1.00 mass% or more and 6.00 mass% or less of Ag, with the balance being Cu and unavoidable impurities, and having a metal structure containing a Cu alloy phase as a parent phase and a second phase precipitate containing an Ag phase, the tensile strength being 950 MPa or more when the Ag content is 1.00 mass% or more and less than 1.50 mass%, 1050 MPa or more when the Ag content is 1.50 mass% or more and less than 3.00 mass%, 1200 MPa or more when the Ag content is 3.00 mass% or more and less than 5.00 mass%, and 1450 MPa or more when the Ag content is 5.00 mass% or more and 6.00 mass% or less, A Cu-Ag based alloy wire in which, in a cross section, when a linear distance from a surface to a center is L, a value (c1-c2) obtained by subtracting an average Ag concentration c1 in a surface annular region extending from the surface toward the center by a length of L / 100 from the surface toward the center from an average Ag concentration c2 in a central region extending from the center toward the surface by a length of 99L / 100 is 1.00 mass% or more and 3.00 mass% or less.

2. The STEM dark-field image of the cross section is grayscaled, and the low-brightness side is binarized to white and the high-brightness side is binarized to black. In the binarized image, the average number density n2 (pieces / μm ２ ) to the average number density n1 (pieces / μm ２ 2. The Cu-Ag alloy wire according to claim 1, wherein the ratio (n1 / n2) of n1 to n2 is 2.0 or more and 6.0 or less.

3. The Cu-Ag alloy wire according to claim 1, wherein the alloy composition further contains one or more elements selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr, and Cr in a total amount of 0.05 mass% or more and 0.30 mass% or less.

4. The Cu-Ag alloy wire according to any one of claims 1 to 3, wherein the Cu-Ag alloy wire is a round wire having a diameter of 0.01 mm or more and 0.08 mm or less.

5. A Cu-Ag alloy wire according to any one of claims 1 to 3, wherein the Cu-Ag alloy wire is a ribbon wire having a width of 0.020 mm or more and 0.320 mm or less and a thickness of 0.002 mm or more and 0.040 mm or less.

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