Copper-silver alloy wire and method for producing same

Abstract

The purpose of the present invention is to provide a copper-silver alloy wire that can suppress the increase in conductor resistance and that has a good hardness, specific resistance, and linearity. This copper-silver alloy wire comprises: an alloy wire rod containing 0.1-30 mass% Ag, the remainder being Cu and unavoidable impurities; and a first plating layer that covers the alloy wire rod, the first plating layer containing Ag. In a cross-section perpendicular to the longitudinal direction of the copper-silver alloy wire in which the Vickers hardness is 300 HV or more, the specific resistance is 3.0 μΩ·cm or less, and the radius of curvature is 300 mm or more, the ratio of the area of the first plating layer to the total area of the cross-section is less than 5.0%.

Description

Cu-Ag alloy wire and its manufacturing method

[0001] The present invention relates to a Cu—Ag alloy wire and a method for producing the same.

[0002] When testing the electrical characteristics of a test object such as a semiconductor integrated circuit, a probe card with an array of multiple probe pins is generally used, and the tips of the probe pins (probe needles) are brought into contact with the test target locations of the test object to test the electrical characteristics. The probe pins are used by repeatedly contacting the test target locations. Therefore, the probe pins are required to have sufficient "hardness." Furthermore, the probe pins are also required to have high linearity to prevent contact between adjacent probe pins (see, for example, Patent Document 1).

[0003] Patent Document 1 describes a probe needle having a metal substrate and a metal layer covering the metal substrate, in which a matte nickel plating layer, a bright nickel plating layer, and a gold alloy plating layer are arranged in this order from the metal substrate side.

[0004] Japanese Patent Application Laid-Open No. 2005-241420

[0005] In recent years, the frequency of currents passed through probe needles has been increasing. When a current of 1 GHz or higher is passed through a probe needle, the current flows only near the surface, including the plating layer, due to the skin effect. When a current of 1 GHz or higher is passed through the probe needle described in Patent Document 1, the nickel plating layer has a high relative magnetic permeability, which increases the skin effect and increases the conductor resistance.

[0006] Therefore, a main object of the present invention is to provide a Cu—Ag alloy wire that can suppress an increase in conductor resistance and has hardness, resistivity, and linearity, and a method for manufacturing the same.

[0007] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a Cu-Ag alloy wire comprising: an alloy wire containing 0.1 to 30 mass % of Ag, with the balance being Cu and unavoidable impurities; and a first plating layer containing Ag covering the alloy wire, wherein the Cu-Ag alloy wire has a Vickers hardness of 300 HV or more, a resistivity of 3.0 μΩ cm or less, and a radius of curvature of 300 mm or more, and in a cross section perpendicular to the longitudinal direction of the Cu-Ag alloy wire, a ratio of an area of ​​the first plating layer to a total area of ​​the cross section is less than 5.0%.

[0008] According to another aspect of the present invention, there is provided a method for manufacturing a Cu-Ag alloy wire, the method comprising: preparing an alloy wire containing 0.1 to 30 mass% Ag, with the remainder being Cu and unavoidable impurities; forming a first plating layer containing Ag on a surface of the alloy wire; and straightening the alloy wire after the step of forming the first plating layer.

[0009] According to the present invention, it is possible to provide a Cu—Ag alloy wire that can suppress an increase in conductor resistance and has hardness, resistivity, and linearity, and a method for manufacturing the same.

[0010] Fig. 1 is a cross-sectional view of a Cu—Ag alloy wire according to an embodiment of the present invention. Fig. 2 is a flowchart showing a method for manufacturing a Cu—Ag alloy wire according to an embodiment of the present invention. Fig. 3 is a diagram for explaining a straightening processing method. Fig. 4 is a diagram for explaining another straightening processing method. Fig. 5 is a diagram for explaining another straightening processing method.

[0011] A Cu—Ag alloy wire according to one embodiment of the present invention and a method for manufacturing the same will be described below. However, the Cu—Ag alloy wire and the method for manufacturing the same of the present invention are not limited to the embodiment shown below. In this specification, the term "to" indicating a range of values ​​means that the upper and lower limits of the range are included.

[0012] (Configuration of Cu—Ag alloy wire) The Cu—Ag alloy wire of this embodiment can be used, for example, as a conductor for electrical characteristic testing. The Cu—Ag alloy wire is particularly suitable for probe pins used when testing the electrical characteristics of test objects such as semiconductor integrated circuits. However, the uses of the Cu—Ag alloy wire are not limited to this. The Cu—Ag alloy wire can also be used for wiring electronic components, and can be used for any purpose including electrical connection.

[0013] FIG. 1 is a cross-sectional view of a Cu—Ag alloy wire according to one embodiment of the present invention.

[0014] 1 , the Cu—Ag alloy wire 10 has an alloy wire 12 and a first plating layer 14 covering the alloy wire 12. In addition to the above configuration, the Cu—Ag alloy wire 10 may have a second plating layer 16 covering the first plating layer. In this embodiment, the Cu—Ag alloy wire 10 has the alloy wire 12, the first plating layer 14, and the second plating layer 16.

[0015] The Vickers hardness of the Cu—Ag alloy wire 10 measured in accordance with JIS Z 2244-1 (2020) may be 300 HV or more, preferably 300 HV to 450 HV. Furthermore, the resistivity of the Cu—Ag alloy wire 10 measured and calculated by the double bridge method may be 3.0 μΩ·cm or less, preferably 2.0 μΩ·cm to 3.0 μΩ·cm. When the resistivity of the Cu—Ag alloy wire 10 is 3.0 μΩ·cm or less, heat generation due to the test current can be suppressed. Furthermore, the curvature radius of the Cu—Ag alloy wire 10 may be 300 mm or more, more preferably 1,000 mm or more. When the curvature radius of the Cu—Ag alloy wire 10 is 300 mm or more, contact or entanglement of two adjacent probe pins can be suppressed when the Cu—Ag alloy wire 10 is used, for example, as a probe pin of an electrical characteristic testing device. The radius of curvature of the Cu—Ag alloy wire 10 was calculated using a digital microscope VHX-6000 manufactured by Keyence Corporation, by arbitrarily selecting three points on the arc of the sample.

[0016] The alloy wire 12 has a composition containing 0.1 to 30 mass %, preferably 10 to 15 mass %, of Ag, with the remainder consisting of Cu and inevitable impurities. The structure of the alloy wire 12 is not particularly limited as long as it satisfies the above conditions. From the viewpoint of satisfying conditions such as Vickers hardness and resistivity, it is preferable that the structure of the alloy wire 12 has a structure in which a Cu-based solid solution phase, a Cu-Ag eutectic phase, and an Ag precipitate phase are stretched into a fibrous form by cold working.

[0017] On the other hand, the first plating layer 14 may be any layer formed by plating and containing Ag. The first plating layer 14 may contain a metal other than Ag. For example, the first plating layer 14 may be composed of an alloy of Ag and various metals. However, the content of Ag in the first plating layer 14 relative to the total amount of metals constituting the first plating layer 14 is preferably 90 mass% or more, and more preferably 95 mass% or more. The properties of the alloy wire 12 are basically maintained even after the first plating layer 14 and the second plating layer 16 are formed.

[0018] The thickness of the first plating layer 14 is appropriately selected depending on the diameter of the Cu—Ag alloy wire 10. Specifically, the thickness of the first plating layer 14 is adjusted so that the ratio of the area of ​​the first plating layer 14 to the total area of ​​the cross section (the area of ​​the entire Cu—Ag alloy wire 10) perpendicular to the longitudinal direction of the Cu—Ag alloy wire 10 is less than 5.0%. The above area ratio is preferably 0.5% to 4.0%. A thicker Ag-containing plating layer tends to increase costs. Therefore, an optimal thickness is selected by balancing the cost and the thickness that can suppress an increase in conductor resistance even at high frequencies. Note that the area ratio does not change before and after the wiredrawing process described below. Note that the area ratio of the first plating layer 14 in the above cross section may be measured by observing the cross section perpendicular to the longitudinal direction of the Cu—Ag alloy wire 10 using a microscope or the like. Alternatively, it may be calculated from the diameter of the alloy wire 12 and the thickness of the first plating layer 14. Alternatively, the plating thickness may be calculated from the weight per unit length of the wire before plating, the weight per unit length of the wire after plating, and the specific gravity of the plating material. The specific thickness of the first plating layer 14 is not particularly limited as long as the above ratio can be satisfied. The thickness of the first plating layer 14 can be determined by measuring the plating thickness by observing a cross section perpendicular to the longitudinal direction.

[0019] On the other hand, the second plating layer 16 may contain Au and be formed by plating, and is preferably a layer made of Au or an alloy thereof. However, the second plating layer 16 is not essential for the Cu—Ag alloy wire 10 of this embodiment. For example, if the discoloration of the first plating layer 14 does not conform to standards, it is preferable to have the second plating layer 16. The thickness of the second plating layer 16 is also appropriately selected depending on the diameter of the Cu—Ag alloy wire 10. Specifically, the thickness of the second plating layer 16 is preferably adjusted so that the ratio of the area of ​​the second plating layer 16 to the total area of ​​the cross section perpendicular to the longitudinal direction of the Cu—Ag alloy wire 10 (total area of ​​the Cu—Ag alloy wire 10) is less than 1.5%. More preferably, this area ratio is 1.3% or less. In this embodiment, since the second plating layer 16 is made of Au or an alloy thereof, a thicker layer increases conductor resistance compared to the first plating layer alone, which generates heat due to the test current. Furthermore, if the Au-containing plating layer is thick, it can suppress the conductor resistance when a current of 1 GHz or higher is passed through the probe needle, even if the first plating layer is a Ni plating layer, but this tends to increase costs. Therefore, a thickness was selected that can suppress costs while maintaining the effect of suppressing the increase in conductor resistance caused by the Ag-containing first plating layer 14. Note that this area ratio does not change before and after wire drawing. The method for determining the area ratio of the second plating layer 16 in the above cross section is the same as the method for determining the area ratio of the first plating layer 14. Note that the thickness of the second plating layer 16 is not particularly limited as long as the above ratio is satisfied. The thickness of the second plating layer 16 can be determined by measuring the plating thickness by observing a cross section perpendicular to the longitudinal direction.

[0020] The elongation of the Cu—Ag alloy wire 10 is preferably within a range of 1 to 5%. The elongation of the Cu—Ag alloy wire 10 can be determined using a precision universal testing machine (for example, manufactured by Shimadzu Corporation). If the elongation of the Cu—Ag alloy wire 10 is 5% or less, for example, when the Cu—Ag alloy wire 10 is used as a probe pin, the end of the probe pin is less likely to sag even if it repeatedly comes into contact with other members.

[0021] Furthermore, the diameter of the Cu—Ag alloy wire 10 is preferably 10 μm or more and 100 μm or less, more preferably 30 μm or more and 70 μm or less, and particularly preferably 30 μm or more and 50 μm or less. If the diameter of the Cu—Ag alloy wire 10 is within the above range, the Cu—Ag alloy wire 10 can be easily used for various applications, and can particularly be easily used as a conductor for electrical property testing.

[0022] (Method for manufacturing Cu—Ag alloy wire) Fig. 2 is a flowchart of the method for manufacturing Cu—Ag alloy wire according to the present embodiment. Fig. 3 is a diagram for explaining the straightening process. Figs. 4 and 5 are diagrams for explaining other straightening processes.

[0023] The Cu—Ag alloy wire can be manufactured, for example, by the following method. Here, a method for manufacturing a Cu—Ag alloy wire having a second plating layer 16 will be described. The method for manufacturing a Cu—Ag alloy wire is not limited to this method.

[0024] 2, the method for producing a Cu—Ag alloy wire includes the steps of: preparing an alloy wire containing 0.1 to 30 mass % Ag with the remainder being Cu and unavoidable impurities; forming a first plating layer containing Ag on the surface of the alloy wire; and forming a second plating layer containing Au on the first plating layer. In this embodiment, the method for producing a Cu—Ag alloy wire further includes the steps of drawing the plated alloy wire (S4) and straightening the drawn alloy wire (S5).

[0025] In the preparation step S1, an alloy wire containing 0.1 to 30 mass% Ag and the remainder consisting of Cu and inevitable impurities is prepared. A more preferred composition of the alloy wire is the same as that of the alloy wire contained in the Cu-Ag alloy wire described above. The alloy wire may be manufactured by any method. For example, the alloy wire may be manufactured by drawing a wire manufactured with any casting diameter. The diameter of the prepared alloy wire is preferably 1.0 mm or less, and more preferably 0.1 mm to 0.6 mm.

[0026] In step S2 of forming the first plating layer, a first plating layer containing Ag is formed on the surface of the alloy wire. The plating method used in step S2 of forming the first plating layer is not particularly limited, as long as it can form the first plating layer so that the above-mentioned area ratio, i.e., the ratio of the area of ​​the first plating layer to the total area of ​​the cross section of the Cu—Ag alloy wire, is less than 5.0%, preferably 0.5% to 4.0%. However, a method that allows continuous plating of the alloy wire is preferred. Furthermore, the thickness of the resulting first plating layer can be adjusted by, for example, the moving speed of the alloy wire during plating. The plating method may be a wet plating method such as an electroplating method using a known Watts bath, sulfamic acid bath, or citric acid bath, or a known electroless plating method, or a dry plating method using a sputtering method or vapor deposition method.

[0027] In the step S3 of forming the second plating layer, a second plating layer containing Au is formed on the first plating layer. The plating method in the step S3 of forming the second plating layer is not particularly limited as long as it can form the second plating layer so that the above-mentioned area ratio, i.e., the ratio of the area of ​​the second plating layer to the total area of ​​the cross section of the Cu—Ag alloy wire, is less than 1.5%, preferably 1.3% or less. However, a method that allows continuous plating treatment of the alloy wire is preferred. Furthermore, the thickness of the obtained second plating layer can be adjusted by, for example, the moving speed of the alloy wire during the plating treatment. In the step S3 of forming the second plating layer, as in the step S2 of forming the first plating layer, the plating layer may be formed by either a wet plating method or a dry plating method.

[0028] In the wire drawing step S4, the plated alloy wire is drawn to a required wire diameter.

[0029] In the straightening step S5, the plated alloy wire after the wiredrawing step is straightened. The straightening method is not particularly limited as long as it can process the plated alloy wire to satisfy the above-mentioned Vickers hardness, resistivity, and radius of curvature. As shown in FIG. 3 , in the straightening step S5, a bobbin 100 (supply bobbin) is prepared on which a plated alloy wire 10a is wound after the step S3 of forming the second plating layer (if the step S3 of forming the second plating layer is not performed, the step S2 of forming the first plating layer is performed). Then, while rotating the bobbin 100 forward, the plated alloy wire 10a is moved in a predetermined direction, and the plated alloy wire 10a is wound on a recovery bobbin 200 (first step). Then, in the second step, while rotating the recovery bobbin 200 backward, the previously wound twisted alloy wire 10b is moved in a predetermined direction and wound on another recovery bobbin 300. This allows the plated alloy wire 10a to be straightened, the radius of curvature to be increased, and the Vickers hardness to be increased without the need for heat treatment.

[0030] 4 and 5 , in another straightening step S5, the plated alloy wire 10a that has undergone step S3 of forming the second plating layer (or step S2 of forming the first plating layer if step S3 of forming the second plating layer is not performed) is twisted using a processing device 600. In this method, the plated alloy wire 10a is first supported by a first support portion 612a, a second support portion 612b, and a third support portion 612c of the processing device 600. At this time, the heights and positions of the first support portion 612a, the second support portion 612b, and the third support portion 612c are adjusted so that the angle (α and β in FIG. 4 ) between the plated alloy wire 10a pressed by the second support portion 612b and the conveying direction is 10 to 70 degrees. Next, while the plated alloy wire 10a is transported from one bobbin 400 side to the other bobbin 500 side at a predetermined speed, the rotating plates (first rotating plate 611a, second rotating plate 611b) of the processing device 600 are rotated at a predetermined speed in the circumferential direction of the plated alloy wire 10a, and the plated alloy wire 10a is wound around the bobbin 500. Next, as shown in FIG. 5 , the twisted alloy wire 10b wound around the bobbin 500 is moved in a predetermined direction, while the (supply) bobbin 500 is rotated in a direction opposite to the twisting direction in the processing device. Then, the twisted alloy wire 10b is wound around the recovery bobbin 700, and the twisted alloy wire 10b is untwisted. This allows the plated alloy wire 10a to be straightened without heat treatment, and the plated alloy wire 10a can be straightened to increase the radius of curvature and Vickers hardness.

[0031] One method of straightening wires is to apply heat to the wire to improve the radius of curvature (tension annealing). However, tension annealing softens the alloy wire due to the heat, making it impossible to meet the Vickers hardness requirements. Furthermore, the heat generated during tension annealing can cause metal atoms contained in the plating layer and the alloy wire to diffuse into each other, forming a new alloy layer between the plating layer and the alloy wire. In this case, the alloy layer may increase resistivity or reduce the inherent properties of the plating (such as oxidation resistance). Therefore, cold straightening without applying heat is preferred.

[0032] (Effects) As described above, according to the present invention, the Cu—Ag alloy wire has a first plating layer containing Ag and exhibits predetermined physical properties, so that an increase in conductor resistance can be suppressed even when a high-frequency current is passed through it.

[0033] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

[0034] 1. Preparation of Cu—Ag Alloy Wire (1) Preparation of Cu—Ag Alloy Wire 1 An alloy wire containing 10% Ag by mass, the remainder being Cu and unavoidable impurities, and having a diameter of 0.03 mm was prepared. Next, using the processing device 600 shown in FIG. 4, while moving the alloy wire at a constant speed, the twisted alloy wire 10b was pressed 4.0 mm perpendicular to the longitudinal direction and rotated in the circumferential direction of the twisted alloy wire 10b at a speed of 6000 rpm. That is, the angles α and β between the twisted alloy wire 10b pressed by the second support portion 612b and the conveying direction of the alloy wire were set to 30°, and the twisting amount was adjusted to 1 to 15 turns / mm. Then, as shown in FIG. 5, the twisted alloy wire 10b was untwisted and wound on a bobbin 700. The amount of untwisting was adjusted to about 0.7% (0.01 to 0.11 turns / mm) of the amount of twisting, and a Cu—Ag alloy wire 1 was obtained.

[0035] (2) Preparation of Cu—Ag Alloy Wire 2 An alloy wire containing 10% by mass of Ag, the remainder being Cu and unavoidable impurities, and having a diameter of 0.6 mm was prepared. Next, a first plating layer (Ag plating layer) was formed on the surface of the alloy wire by electroplating, and the wire was drawn to a diameter of 0.03 mm, resulting in a thickness of the first plating layer of 0.04 μm. The thickness of the first plating layer was determined by measuring the plating thickness through observation of a cross section perpendicular to the longitudinal direction. For the wire after the first plating layer was formed, the ratio of the area of ​​the first plating layer to the total area was confirmed to be 0.5% through observation of a cross section perpendicular to the longitudinal direction. Next, the wire was drawn and straightened in the same manner as for Cu—Ag alloy wire 1 to prepare Cu—Ag alloy wire 2. Note that the area ratio was the same before and after wiredrawing and straightening.

[0036] (3) Preparation of Cu—Ag Alloy Wire 3 Cu—Ag alloy wire 3 was prepared in the same manner as Cu—Ag alloy wire 2, except that a second plating layer (Au plating layer) was formed on a first plating layer (Ag plating layer) by electroplating, followed by wiredrawing to a diameter of 0.03 mm, resulting in a first plating layer thickness of 0.04 μm and a second plating layer thickness of 0.1 μm. The thickness of the second plating layer was determined by measuring the plating thickness through observation of a cross section perpendicular to the longitudinal direction. For the wire after the first plating layer was formed, the ratio of the area of ​​the second plating layer to the total area of ​​the cross section perpendicular to the longitudinal direction was confirmed to be 1.3% through measurement of the plating thickness through observation of the cross section perpendicular to the longitudinal direction. This area ratio was the same before and after wiredrawing and straightening.

[0037] (4) Preparation of Cu—Ag alloy wire 4 After forming the first plating layer (Ag plating layer), the wire was drawn to a diameter of 0.03 mm, and the thickness of the first plating layer became 0.3 μm. Except for this, the Cu—Ag alloy wire 4 was prepared in the same manner as the preparation of the Cu—Ag alloy wire 2.

[0038] (5) Preparation of Cu—Ag alloy wire 5 A Cu—Ag alloy wire 5 was prepared in the same manner as the preparation of the Cu—Ag alloy wire 3, except that a second plating layer (Au plating layer) was formed on the first plating layer (Ag plating layer), and then the wire was drawn to a diameter of 0.03 mm, so that the thickness of the first plating layer was 0.3 μm and the thickness of the second plating layer was 0.1 μm.

[0039] (6) Preparation of Cu—Ag alloy wire 6 After forming the first plating layer (Ni plating layer), the wire was drawn to a diameter of 0.03 mm, and the thickness of the first plating layer became 0.04 μm. Except for this, the Cu—Ag alloy wire 6 was prepared in the same manner as the preparation of the Cu—Ag alloy wire 2.

[0040] (7) Preparation of Cu—Ag alloy wire 7 A Cu—Ag alloy wire 7 was prepared in the same manner as the preparation of the Cu—Ag alloy wire 6, except that a second plating layer (Au plating layer) was formed on a first plating layer (Ni plating layer) by electrolytic plating, and then the wire was drawn to a diameter of 0.03 mm, so that the thickness of the first plating layer was 0.04 μm and the thickness of the second plating layer was 0.1 μm.

[0041] (8) Preparation of Cu—Ag alloy wire 8 After forming the first plating layer (Ni plating layer), the wire was drawn to a diameter of 0.03 mm, and the thickness of the first plating layer became 0.3 μm. Except for this, the Cu—Ag alloy wire 8 was prepared in the same manner as the preparation of the Cu—Ag alloy wire 6.

[0042] (9) Preparation of Cu—Ag alloy wire 9 A Cu—Ag alloy wire 9 was prepared in the same manner as the preparation of the Cu—Ag alloy wire 8, except that a second plating layer (Au plating layer) was formed on the first plating layer (Ni plating layer), and then the wire was drawn to a diameter of 0.03 mm, so that the thickness of the first plating layer was 0.3 μm and the thickness of the second plating layer was 0.1 μm.

[0043] 2. Evaluation of Samples (1) Measurement of Vickers Hardness The hardness (Vickers hardness) of each sample (Cu-Ag alloy wire) was measured using a Vickers hardness tester in accordance with JIS Z 2244-1 (2020). The measuring device used was a Vickers hardness tester (AMT-X7AFS) manufactured by Matsuzawa Co., Ltd. The measurement conditions were a load of 10 gf and a holding time of 15 seconds.

[0044] (2) Measurement of specific resistance For each sample (Cu-Ag alloy wire), the electrical resistance was measured for five samples using the double bridge method in a room controlled at 20°C (±2°C), and the average value of the specific resistance (μΩ cm) was calculated. The distance between the voltage terminals was 500 mm.

[0045] (3) Measurement of curvature radius To evaluate linearity, the curvature radius of each sample (Cu—Ag alloy wire) was measured. Specifically, using a digital microscope VHX-6000 manufactured by Keyence Corporation, three points were arbitrarily selected from the arc of the sample, and the curvature radius (mm) was calculated.

[0046] Table 1 shows the results of the Vickers hardness measurement, the resistivity measurement, and the radius of curvature measurement.

[0047]

[0048] (4) Simulation The conductor resistance when a current of a predetermined frequency was passed through each sample (Cu-Ag alloy wire) with a length of 5 mm and a diameter of 0.03 mm was simulated under the following conditions. The simulation results of the conductor resistance are shown in Table 2. - Name and version of software used in the simulation: Murata Software Co., Ltd. Femtet Ver. 2023 - Analysis conditions: 2D model magnetic field / harmonic analysis 1 MHz to 100 GHz - Metal physical properties: (Cu-Ag alloy) Conductivity: 65% IACS Relative permeability: 1 (Ag) Conductivity: 106% IACS Relative permeability: 1 (Ni) Conductivity: 25% IACS Relative permeability: 180 (Au) Conductivity: 73% IACS Relative permeability: 1 - Conductor diameter: 30 μm (including plating thickness) - Number of meshes: Approximately 100,000

[0049]

[0050] As shown in Table 2, in the Cu—Ag alloy wires No. 2 to No. 5 of the examples having an Ag plating layer as the first plating layer, an increase in conductor resistance was suppressed even when the frequency increased. On the other hand, in the Cu—Ag alloy wires No. 6 to No. 9 of the examples having a Ni plating layer as the first plating layer, the conductor resistance increased as the frequency increased. In addition, in the Cu—Ag alloy wire No. 1 of the comparative example having no plating layer, the surface was oxidized due to the absence of an Ag plating layer.

[0051] The Cu—Ag alloy wire according to the present invention can be used for various purposes, such as contact probes and lead wires for electrical characteristic testing devices.

[0052] REFERENCE SIGNS LIST 10 Cu—Ag alloy wire 10a Alloy wire after plating 10b Alloy wire after twisting 12 Alloy wire 14 First plating layer 16 Second plating layer 100, 200, 300, 400, 500, 700 Bobbin 600 Processing device 611a First rotating plate 611b Second rotating plate 612a First support portion 612b Second support portion 612c Third support portion

Claims

1. A Cu—Ag alloy wire comprising an alloy wire containing 0.1 to 30% by mass of Ag and the balance being Cu and unavoidable impurities, and a first plating layer containing Ag covering the alloy wire, having a Vickers hardness of 300 HV or more, a specific resistance of 3.0 μΩ·cm or less, and a curvature radius of 300 mm or more, and in a cross section perpendicular to the longitudinal direction of the Cu—Ag alloy wire, the ratio of the area of the first plating layer to the total area of the cross section is less than 5.0%.

2. The Cu—Ag alloy wire according to claim 1, further having a second plating layer containing Au on the first plating layer.

3. The Cu—Ag alloy wire according to claim 2, wherein in a cross section perpendicular to the longitudinal direction of the Cu—Ag alloy wire, the ratio of the area of the second plating layer to the total area of the cross section is less than 1.5%.

4. A method for manufacturing a Cu—Ag alloy wire, comprising the steps of preparing an alloy wire containing 0.1 to 30% by mass of Ag and the balance being Cu and unavoidable impurities, and forming a first plating layer containing Ag on the surface of the alloy wire.

5. The method for manufacturing a Cu—Ag alloy wire according to claim 4, further comprising a step of straightening the alloy wire after the step of forming the first plating layer.

6. The method for manufacturing a Cu—Ag alloy wire according to claim 5, further comprising a step of forming a second plating layer containing Au on the first plating layer before the step of straightening.

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