WO2024177092A1

WO2024177092A1 - Copper–silver alloy wire

Info

Publication number: WO2024177092A1
Application number: PCT/JP2024/006161
Authority: WO
Inventors: 達也高橋; 亮佑松尾
Original assignee: 古河電気工業株式会社
Priority date: 2023-02-21
Filing date: 2024-02-21
Publication date: 2024-08-29

Abstract

Provided is a copper–silver alloy wire that has sufficient conductivity and high strength and that can maintain high strength even when used for a long period in a heat-generating state. This copper–silver alloy wire has a composition that contains 1–6% by mass of silver, with the remainder consisting of copper and unavoidable impurities, and is characterized in that: the copper–silver alloy wire has a copper phase that is a parent phase and a plurality of silver phases that are second phases; if the cross-sectional area of a transverse cross-section perpendicular to the longitudinal direction of the copper–silver alloy wire is represented by σ (μm²) and the diameter of a circle with the same area as each of the silver phases present in that transverse cross-section is represented by D (μm), a formula (1) (in formula (1), π represents the circular constant) is satisfied; and the ratio of the number of silver phases with a diameter D that is less than 5 nm to the total number of silver phases is at least 50%.

Description

Cu-Ag alloy wire

The present invention relates to Cu-Ag alloy wire.

Pure copper wire and copper alloy wire are used as wire materials for electrical and electronic equipment. In this application, as technology becomes more advanced, the diameter of the single wire becomes thinner, and the use of alloy wires such as Cu-Sn, Cu-Cr, and Cu-Ag is increasing in place of pure copper wire, which lacks strength. In recent years, as electronic devices have become increasingly dense and compact, there has been a trend for cables for connecting electrical and electronic equipment and electric wires such as speaker coils to become even thinner in diameter. Therefore, among copper alloys, Cu-Ag alloy wire, which has an excellent balance between strength and conductivity, is mainly used.

Patent documents

1 and 2 disclose techniques for improving both the strength and electrical conductivity of Cu-Ag alloy wire by controlling the structure of the eutectic phase of Cu and Ag to extend like a filament. Patent document 1 shows a technique for developing a recrystallized texture by heat treatment during the process, and then increasing the strength by intensive processing. Patent document 2 shows that controlling the cooling rate during alloy casting causes the precipitates to crystallize finely and uniformly, increasing the strength of the alloy wire.

However, in Patent Document 1, appropriate wire drawing process conditions are not adopted before heat treatment, which leads to material embrittlement during heat treatment, making it difficult to produce thin wire and resulting in poor productivity that makes the product less cost-competitive. Furthermore, the cooling rate in the casting process is not sufficiently considered. Furthermore, Patent Document 2 does not consider controlling the distribution of crystal precipitates or promoting precipitation by optimizing intermediate heat treatment, leaving room for further strength improvement. In addition, neither Patent Document 1 nor Patent Document 2 discloses strength characteristics in a state where the cable continues to heat up due to Joule heat or vibration heat generated when current is passed through the cable for connecting electric and electronic devices.

International Publication No. 2007/046378 JP 2017-2337 A

The objective of the present invention is to provide a Cu-Ag alloy wire that has both high strength and high electrical conductivity, and that can maintain its high strength even when used for long periods of time under high-temperature heating due to heat generation.

In order to achieve the above object, the gist of the present invention is as follows.
[1] A Cu-Ag based alloy wire containing 1 mass% or more and 6 mass% or less of Ag, with the remainder being composed of Cu and unavoidable impurities,
The Cu-Ag alloy wire has a metal structure including a Cu phase as a parent phase and a plurality of Ag phases as a second phase,
When the cross-sectional area of the cross section perpendicular to the longitudinal direction of the Cu—Ag based alloy wire is σ and the diameter of a perfect circle having the same area as each of the Ag phases present in the cross section is D, the following formula (1) is satisfied:

(In formula (1), π represents the ratio of the circumference of a circle to its circumference.)
and the number of Ag phases having a diameter D of less than 5 nm accounts for 50% or more of the total number of Ag phases.
[2] In the cross section of the Cu-Ag based alloy wire,
The Cu-Ag based alloy wire according to [1] above, wherein the number of Ag phases present on the crystal grain boundaries of the Cu phase is 15% or more and 35% or less of the total number of Ag phases.
[3] The Cu-Ag-based alloy wire according to the above [1] or [2], wherein the composition further contains at least one additional element selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr and Cr in an amount of 0.05 mass% or more and 0.3 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 wire diameter of 0.01 mm or more and 0.08 mm or less.
[5] The Cu-Ag alloy wire is a ribbon wire having a substantially rectangular cross section with a width of 0.02 mm or more and 0.32 mm or less and a thickness of 0.002 mm or more and 0.04 mm or less. The Cu-Ag alloy wire according to any one of [1] to [3] above.

The present invention makes it possible to provide a Cu-Ag alloy wire that has both high strength and high electrical conductivity, and that can maintain its high strength even when used for long periods of time under high-temperature heating due to heat generation.

1A to 1C are schematic longitudinal sectional views showing metal structures of the Cu—Ag alloy wire of the present invention when cut in its longitudinal direction, and show the metal structures after each manufacturing process. 1A to 1C are schematic longitudinal sectional views showing metal structures of a conventional Cu—Ag alloy wire cut in its longitudinal direction, showing the metal structures after each manufacturing process. 1 shows a scanning transmission electron microscope (STEM) photograph of the distribution state of an Ag phase present in a cross section of a Cu—Ag based alloy wire, and a processed image of the Ag phase. 1 shows a scanning transmission electron microscope (STEM) photograph of the distribution state of Ag phases present on grain boundaries in the cross section of a Cu-Ag based alloy wire, and a processed image of the grain boundaries of the Ag phase.

The present inventors have found that, in a Cu-Ag alloy wire having a predetermined composition and produced by a production process including wire drawing, by optimizing the production method, particularly the heat treatment conditions, it is possible to obtain a Cu-Ag alloy wire having a desired metal structure and excellent strength and heat resistance, and have completed the present invention based on this finding.
Hereinafter, an embodiment of the present invention will be described.

[1] Composition of Cu-Ag alloy wire <Essential components>
The Cu-Ag alloy wire of the present invention contains 1 mass % or more and 6 mass % or less of Ag as an essential component.

[Ag: 1% by mass or more and 6% by mass or less]
In the Cu-Ag alloy wire of the present invention, by setting the Ag content in the range of 1 mass % to 6 mass %, it has sufficient electrical conductivity and high tensile strength, and further has long-term durability under a heated state. If the Ag content is less than 1 mass %, the Ag phase does not precipitate sufficiently, and the desired metal structure cannot be obtained, so that the tensile strength is significantly reduced. On the other hand, when the Ag content exceeds 6 mass %, the electrical conductivity is significantly decreased. Furthermore, even if the Ag content exceeds 6 mass %, no further improvement in tensile strength can be expected. This is because the increased quantity leads to an increase in costs.

In the Cu-Ag alloy wire of the present invention, Ag (silver) exists in a state of solid solution in the Cu phase, which is the parent phase (first phase), or in a state of crystallization as the Ag phase, which is the second phase. The Ag dissolved in the Cu phase exerts a solid solution strengthening effect, and the crystallized Ag phase becomes a fibrous Ag phase having a fibrous shape due to the wire drawing process, exerting a fiber strengthening effect. The Ag phase, which is a crystallized precipitate, precipitates during cooling after casting and aging heat treatment, etc., and in the manufacturing method of the Cu-Ag alloy wire of the present invention described below, it precipitates mainly during the cooling process after casting and the first and second heat treatment processes.

<Optionally Added Ingredients>
The Cu-Ag alloy wire of the present invention may contain the following components as optional additives.

[At least one additional element selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr, and Cr: 0.05% by mass or more and 0.3% by mass or less each]
Furthermore, in the Cu-Ag alloy wire of the present invention, it is preferable to further contain at least one component selected from the group consisting of Sn (tin), Mg (magnesium), Zn (zinc), In (indium), Ni (nickel), Co (cobalt), Zr (zirconium) and Cr (chromium) in a range of 0.05 mass% to 0.3 mass%. These optional components exist in a solid solution state in the parent phase (first phase) Cu, or as single-phase or ternary or more element crystal precipitates, and exert the effect of solid solution strengthening or fiber strengthening. Examples of ternary or more element crystal precipitates include Cu-Ag-Zr. Single-phase or ternary or more element crystal precipitates of the secondary additive elements precipitate during cooling after casting and during aging heat treatment.
The contents of the individual auxiliary elements will be explained below.

(Sn: 0.05% by mass or more and 0.3% by mass or less)
Sn (tin) is an element that improves tensile strength. To achieve this effect, the Sn content is preferably 0.05 mass% or more, and more preferably 0.07 mass% or more. It is preferable that the Sn content is 0.08 mass% or more, more preferably 0.1 mass% or more. On the other hand, if the Sn content is too high, there is a risk of the electrical conductivity being significantly reduced. It is preferably 0.3 mass% or less, more preferably 0.18 mass% or less, further preferably 0.15 mass% or less, and particularly preferably 0.12 mass% or less. .

(Mg: 0.05% by mass or more and 0.3% by mass or less)
Mg (magnesium) is an element that improves tensile strength. To achieve this effect, the Mg content is preferably 0.05% by mass or more, and more preferably 0.07% by mass or more. It is preferable that the Mg content is 0.08 mass% or more, more preferably 0.1 mass% or more. On the other hand, if the Mg content is too high, there is a risk of the electrical conductivity being significantly reduced. It is preferably 0.3 mass% or less, more preferably 0.18 mass% or less, further preferably 0.15 mass% or less, and particularly preferably 0.12 mass% or less. .

(Zn: 0.05% by mass or more and 0.3% by mass or less)
Zn (zinc) is an element that improves tensile strength. To achieve this effect, the Zn content is preferably 0.05% by mass or more, and more preferably 0.07% by mass or more. It is more preferable that the Zn content is 0.08 mass% or more, and even more preferable that the Zn content is 0.1 mass% or more. On the other hand, if the Zn content is too high, the electrical conductivity may be significantly reduced. %, preferably 0.3 mass % or less, more preferably 0.25 mass % or less, even more preferably 0.2 mass % or less, and particularly preferably 0.15 mass % or less. preferable.

(In: 0.05% by mass or more and 0.3% by mass or less)
In (indium) is an element that improves tensile strength. To achieve this effect, the In content is preferably 0.05% by mass or more, and more preferably 0.07% by mass or more. It is more preferable that the In content is 0.08 mass% or more, further more preferable that the In content is 0.1 mass% or more. On the other hand, if the In content is too high, there is a risk of the electrical conductivity being significantly reduced. %, preferably 0.3 mass % or less, more preferably 0.18 mass % or less, even more preferably 0.15 mass % or less, and particularly preferably 0.12 mass % or less. preferable.

(Ni: 0.05% by mass or more and 0.3% by mass or less)
Ni (nickel) is an element that improves tensile strength. To achieve this effect, the Ni content is preferably 0.05% by mass or more, and more preferably 0.07% by mass or more. It is more preferable that the Ni content is 0.08 mass% or more, and even more preferable that the Ni content is 0.1 mass% or more. On the other hand, if the Ni content is too high, the electrical conductivity may be significantly reduced. %, preferably 0.3 mass % or less, more preferably 0.25 mass % or less, even more preferably 0.2 mass % or less, and particularly preferably 0.15 mass % or less. preferable.

(Co: 0.05% by mass or more and 0.3% by mass or less)
Co (cobalt) is an element that improves tensile strength. To achieve this effect, the Co content is preferably 0.05 mass% or more, and more preferably 0.07 mass% or more. It is more preferable that the Co content is 0.08 mass% or more, and even more preferable that the Co content is 0.1 mass% or more. On the other hand, if the Co content is too high, the electrical conductivity may be significantly reduced. %, preferably 0.3 mass % or less, more preferably 0.18 mass % or less, even more preferably 0.15 mass % or less, and particularly preferably 0.12 mass % or less. preferable.

(Zr: 0.05% by mass or more and 0.3% by mass or less)
Zr (zirconium) is an element that improves tensile strength and reduces brittleness. To achieve this effect, the Zr content is preferably 0.05 mass% or more, and more preferably 0.07 mass% or more. It is more preferable that the Zr content is 0.08 mass % or more, further preferably 0.1 mass % or more. On the other hand, if the Zr content is too high, the electrical conductivity is significantly reduced. Therefore, the content is preferably 0.3% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.15% by mass or less, and further preferably 0.12% by mass or less. It is particularly preferred that:

(Cr: 0.05% by mass or more and 0.3% by mass or less)
Cr (chromium) is an element that improves tensile strength. To achieve this effect, the Cr content is preferably 0.05 mass% or more, and more preferably 0.07 mass% or more. It is more preferable that the Cr content is 0.08 mass% or more, and even more preferable that the Cr content is 0.1 mass% or more. On the other hand, if the Cr content is too high, there is a risk of the electrical conductivity being significantly reduced. %, preferably 0.3 mass % or less, more preferably 0.18 mass % or less, even more preferably 0.15 mass % or less, and particularly preferably 0.12 mass % or less. preferable.

[Sn, Mg, Zn, In, Ni, Co, Zr and Cr: 0.05% by mass or more and 1% by mass or less in total]
From the viewpoint of achieving a higher compatibility between tensile strength and electrical conductivity, Sn, Mg, Zn, In, Ni, Co, Zr, and Cr are preferably contained in a total amount of 0.05 mass % or more and 1 mass % or less, and more preferably in a total amount of 0.1 mass % or more and 0.5 mass % or less.

<Balance: Cu and inevitable impurities>
Other than the above-mentioned essential components and optional additional components, the balance is Cu (copper) and inevitable impurities. Cu is the parent phase of the Cu-Ag alloy wire of the present invention, and Ag, which is an essential additional component, is present in a solid solution state or a crystallized state. The inevitable impurities are impurities at a content level that can be unavoidably contained in the manufacturing process of the Cu-Ag alloy wire of the present invention. Examples of inevitable impurities include Pb (lead), S (sulfur), and P (phosphorus).

[2] Metal structure and shape of Cu-Ag alloy wire The Cu-Ag alloy wire of the present invention has a metal structure including a Cu phase as a parent phase and a plurality of Ag phases as a second phase. The Ag phase in the Cu-Ag alloy wire of the present invention is a fibrous Ag phase due to the wire drawing process as described above, and a relatively large coarse fibrous Ag phase (hereinafter also referred to as "fibrous coarse Ag phase") and a fine fibrous Ag phase (hereinafter also referred to as "fibrous fine Ag phase") are present.

The fibrous coarse Ag phase was also present in Cu-Ag alloy wires manufactured in the past, and originates from the coarse Ag phase that crystallized mainly during cooling after casting, as shown in FIG. 2. The fibrous fine Ag phase is an Ag phase characteristic of the present invention, and originates from a large number of fine Ag phases (hereinafter also referred to as "fine Ag phases") that crystallized in the first and second heat treatment steps described below, as shown in FIG. 1. The fine Ag phases that crystallized in the first and second heat treatment steps are usually 1/10,000 or less of the wire diameter when precipitated, so the ratio to the wire diameter is the same for the stretched fibrous fine Ag phase. In other words, the fibrous fine Ag phase refers to a phase in which the diameter D is 1/10,000 or less of the wire diameter and less than 5 nm when observed in cross section of the manufactured Cu-Ag alloy wire. On the other hand, the fibrous coarse Ag phase refers to a phase in which the diameter D exceeds 1/10,000 of the wire diameter or is 5 nm or more when observed in the same manner. The diameter of the fibrous Ag phase refers to the diameter of a perfect circle having the same area as each of the fibrous Ag phases present in the cross section. In the Cu-Ag alloy wire of the present invention, in addition to the fibrous coarse Ag phases 2f, there are many fibrous fine Ag phases 3f, and the tensile strength is significantly improved by the action of fiber reinforcement.

<Number ratio of fibrous fine Ag phase>
In the Cu—Ag alloy wire of the present invention, when the cross-sectional area of a cross section perpendicular to the longitudinal direction of the Cu—Ag alloy wire is σ (μm ² ) and the diameter of a perfect circle having the same area as each Ag phase present in the cross section (hereinafter, also simply referred to as the “diameter of the Ag phase”) is D (μm), the following formula (1) is satisfied:

(In formula (1), π represents the ratio of the circumference of a circle to its circumference.)
and the ratio of the number of Ag phases having a diameter D of less than 5 nm to the total number of Ag phases is 50% or more.

The tensile strength of the Cu-Ag alloy wire can be improved by making the ratio of the diameter of the Ag phase in the cross section of the Cu-Ag alloy wire, i.e., the diameter of the cross section of the fibrous Ag phase, which satisfies the range of the above formula (1) 50% or more of the total number of Ag phases. When the ratio of fine Ag phases that satisfy the above formula (1), i.e., fibrous fine Ag phases, is high, the number of Ag phases contained in the Cu-Ag alloy wire increases, and a Cu-Ag alloy wire having a high density of fibrous fine Ag phases can be obtained. Therefore, the ratio of the number of Ag phases whose diameter D satisfies formula (1) is 50% or more, preferably 60% or more. In this case, the spacing between the fibrous fine Ag phases located perpendicular to the wire drawing direction becomes narrower.

The above formula (1) determines the diameter d (μm) of a perfect circle having a cross-sectional area σ (μm ² ) of the Cu-Ag alloy wire, regardless of the shape of the Cu-Ag alloy wire, and determines the proportion of fibrous micro Ag phases having a diameter D that is 1/10,000 or less of the diameter d. The diameter of the fibrous micro Ag phases is affected by the final wire diameter d after wiredrawing, and is therefore expressed as a function of the cross-sectional area σ calculated from the final wire diameter d.

Furthermore, it is preferable that the average diameter of the fibrous Ag phase is in the range of 0.5 to 10 nm when measured in a cross section perpendicular to the longitudinal direction. In the Cu-Ag alloy wire of the present invention, fibrous Ag phases with a diameter of 0.5 nm or less may be present depending on the final wire diameter, but since it is very difficult with current technology to detect and count fibrous Ag phases with a diameter of 0.5 nm or less in a cross section, the limit is 0.5 nm or more.

Furthermore, among the above-mentioned fibrous Ag phases, the average diameter of the fibrous coarse Ag phase and the average diameter of the fibrous coarse Ag phase when measured in cross section will vary depending on the final wire diameter of the Cu-Ag alloy wire as described above, but the average diameter of the fibrous micro Ag phase is, for example, 0.5 nm or more and less than 5 nm, and preferably 0.5 nm or more and 3 nm or less. On the other hand, the average diameter of the fibrous coarse Ag phase is, for example, more than 5 nm and 20.0 nm or less.

The number ratio of fibrous fine Ag phases can be measured by the following method. First, the sample is thinned by using the focused ion beam method (FIB) on the cross section perpendicular to the longitudinal direction of the Cu-Ag alloy wire. For this processing, for example, a SIINT-3050TB (manufactured by SII Nanotechnology) is used with a Ga ion beam acceleration voltage of 30 kV. After processing, Ar ion milling is performed for 5 minutes with an acceleration voltage of 2 kV, for example, to remove damage to the sample. After processing, the cross section perpendicular to the longitudinal direction of the processed sample is observed with a scanning transmission electron microscope (STEM). For STEM observation, for example, a JEM-ARM200F (manufactured by JEOL Ltd.) is used with an electron beam acceleration voltage of 200 kV, and the observation area is a square with one side of 130 nm or more, and STEM bright field images and STEM dark field images (high angle scattering dark field images) are taken. By observing the cross section, the Ag phase is continuously present in the depth direction of the observation surface, so even fine precipitates less than 5 nm in size can be easily detected. The average diameter and number of Ag phases can be calculated by processing the obtained STEM dark field image with the image processing software "Image J (version v1.53k)", and the number ratio of fibrous fine Ag phases can be calculated. In addition, in areas where contrast that may be Ag phases is confirmed, elemental analysis can be performed using energy dispersive X-ray analysis (EDX: Energy Dispersive X-ray spectroscopy) attached to the STEM to confirm the presence of Ag phases more accurately.

The specific image processing procedure will be described with reference to FIG. 3, which is an actual example. First, an arbitrary range (a to c in FIG. 3, left) from, for example, 400 to 800 nm ² is trimmed from the dark field image (left in FIG. 3), and this image is converted into a grayscale image. Next, in the histogram of the brightness value of this image, the upper 3 to 6% is used as a threshold, and the low brightness side is binarized to white and the high brightness side to black (FIG. 3a-1 to c-1). Furthermore, after removing black parts of 10 pixels or less as noise, the remainder is regarded as Ag phase precipitates (FIG. 3a-2 to c-2). Then, the number of pixels of each precipitate is calculated and converted to an area, and the diameter is calculated from the area assuming that each precipitate is a perfect circle, so that the diameter D of each precipitate, i.e., the Ag phase, can be obtained. The total number of Ag phase precipitates in the measurement range is then counted, the number of those falling within the range of formula (1) is counted, and the result is divided by the total number to calculate the proportion of the number of fibrous fine Ag phase precipitates.

Furthermore, it is preferable that the Ag phase present in the Cu-Ag alloy wire is distributed on the wire in a line connected in the approximately longitudinal direction. In other words, it is preferable that the Ag phase is a fibrous Ag phase (fibrous coarse Ag phase, fibrous fine Ag phase). In the prior art, it has been confirmed by analytical techniques that the crystallized coarse Ag phase is elongated in the longitudinal direction by wire drawing and exists in the Cu-Ag alloy wire as a fibrous coarse Ag phase. Although no analytical results showing that it is fibrous are shown in this specification, it is reasonably understandable that the micro Ag phase crystallized by the aging heat treatment in this invention also elongates in the longitudinal direction, although the size is different, and becomes, for example, a fibrous micro Ag phase with an aspect ratio of 100 or more, and exists in the Cu-Ag alloy wire of the present invention.

<Number ratio of Ag phases on grain boundaries>
In the Cu-Ag alloy wire of the present invention, the number of Ag phases present on the grain boundaries of the Cu phase in the cross section of the Cu-Ag alloy wire is preferably 15% or more and 35% or less in terms of the ratio to the total number of Ag phases (hereinafter also referred to as the "number ratio of Ag phases on grain boundaries"). By making the number ratio of Ag phases on grain boundaries preferably 15% or more, more preferably 20% or more, the pinning effect suppresses softening due to coarsening of crystal grains during heat generation, and as a result, the decrease in tensile strength during heat generation can be suppressed. On the other hand, from the viewpoint of suppressing grain boundary cracking due to excessive uneven distribution of second phase particles to the grain boundaries and the resulting decrease in tensile strength, the number ratio of Ag phases on grain boundaries is preferably 35% or less.

The number ratio of Ag phases on the grain boundaries was measured using the following procedure. The measurement uses the STEM bright-field image and STEM dark-field image acquired during the above measurement of the number ratio of Ag phases, and performs image processing with the image processing software "Image J (version v1.53k)" to measure the number ratio of Ag phases on the grain boundaries.

The specific image processing procedure will be described with reference to FIG. 4, which is an actual measurement example. First, the acquired STEM bright-field image is binarized to determine the position of the grain boundary. An arbitrary range (a to c, left in FIG. 4) of, for example, 400 to ⁸⁰⁰ nm2 is trimmed from the bright-field image (left in FIG. 4), and this image is converted into a grayscale image. Next, in the histogram of the brightness value of this image, the top 10% is used as a threshold value to binarize, and the high brightness side is white and the low brightness side is black. Among the black parts, for example, black parts that continue in the longitudinal direction for 15 nm or more and have a short side length of 5 nm or less are determined to be grain boundaries (FIG. 4a-1 to c-1). In addition, following the procedure shown in the explanation of the measurement of the number ratio of Ag phase, extraction of Ag phase precipitates is performed for the same range (a to c, left in FIG. 4) for the STEM dark-field image. Note that in FIG. 4, the measurement is performed for the same range as the range in which the precipitates were measured in FIG. 3, so FIG. 3 is used to explain the position of the precipitates. For example, an arbitrary range from 400 to ⁸⁰⁰ nm2 (Figure 3, left, a to c) of the STEM dark-field image is trimmed, and this image is converted to grayscale. Next, in the histogram of the brightness values of this image, the top 10% and top 2% brightness values are compared, and if the difference is 25 or more, the top 2% is used as a threshold for binarization (Figures 3a-1 to c-1). At that time, the low brightness side is made white and determined to be the parent phase, and the high brightness side is made black. Furthermore, 10 pixels or less of the binarized black parts are removed as noise, and the remainder is determined to be Ag phase precipitates (Figures 3a-2 to c-2). By comparing the positions of the grain boundaries (Figs. 4a-1 to 4c-1) with the positions of the Ag phase precipitates (Figs. 3a-2 to 3c-2), the Ag phase that overlaps even a part of the line indicating the grain boundary is regarded as a precipitate on the grain boundary, and the Ag phase that does not overlap at all is regarded as a precipitate within the grain, not on the grain boundary, and the number ratio of the Ag phase that is a precipitate on the grain boundary is calculated.

In addition, when measured in a cross section perpendicular to the longitudinal direction, the total number of Ag phases present per unit area of 1 μm ² is, for example, 100 to 15,000. From the viewpoint of improving tensile strength, the total number of Ag phases is preferably 1,000 or more. On the other hand, from the viewpoint of ease of setting manufacturing conditions, the total number of Ag phases is preferably 13,000 or less.

<Shape of Cu—Ag based alloy wire>
The shape of the Cu-Ag alloy wire of the present invention is not particularly limited, but examples thereof include a round wire and a ribbon wire.

The Cu-Ag alloy wire of the present invention is preferably a round wire with a wire diameter of 0.01 mm or more and 0.08 mm or less. There is a demand in the market for ultra-fine wires with high tensile strength and high conductivity of 0.01 mmφ or more and 0.08 mmφ or less as conductors for use in parts. The lower limit of the wire diameter is 0.01 mmφ, reflecting market needs, and if there is a demand for even thinner diameters in the future, this can be met by applying the Cu-Ag alloy wire of the present invention. If the wire diameter exceeds 0.08 mmφ, the dimensions are too large and it will not be able to fulfill its role as an ultra-fine wire.

The Cu-Ag alloy wire of the present invention is preferably a ribbon wire having a substantially rectangular cross-sectional shape with a width of 0.02 mm to 0.32 mm and a thickness of 0.002 mm to 0.04 mm. One manufacturing method is, for example, to roll the above-mentioned round wire that has been drawn into the desired shape. For the same reasons as for the upper and lower limits of the wire diameter, the ribbon-shaped dimensions are preferably a plate width of 0.02 mm to 0.32 mm and a plate thickness of 0.002 mm to 0.04 mm. The plate width is in the width direction of the rolling rolls, and the plate thickness is in the inter-roll direction, and the non-contact portion of the rolling rolls at the end in the plate width direction remains as a circular arc shape while being deformed. Here, the longest value in the cross section of the ribbon wire is the width, and the shortest value is the thickness. The properties of the ribbon wire are not significantly different from those of the circular shape before it is formed into a ribbon shape, in terms of strength and conductivity.

[3] Manufacturing method of Cu-Ag alloy wire The Cu-Ag alloy wire of the present invention can be manufactured by a manufacturing method including, for example, a casting step [step 1], a post-casting cooling step [step 2], a first wiredrawing step [step 3], a first heat treatment step [step 4], a second heat treatment step [step 5], and a second wiredrawing step [step 6], as shown below.

In order to control the proportion of the fibrous fine Ag phase within the range specified in the present invention, it is particularly important to carry out the post-casting cooling process [process 2], the first heat treatment process [process 4], and the second heat treatment process [process 5] under appropriate conditions. In addition, in order to control the proportion of the Ag phase on the grain boundaries within the range specified in the present invention, it is particularly important to carry out the post-casting cooling process [process 2] under appropriate conditions.

(i) Casting process [Process 1]
In the method for producing a Cu-Ag alloy wire of the present invention, first, a casting step is carried out in which raw materials and auxiliary additive elements are added so as to obtain a desired composition, and then the raw materials and the auxiliary additive elements are cast and rolled to obtain a roughly drawn wire. In this type, molten metal is continuously poured into a ring-shaped groove die for casting, and then rolled continuously to obtain rough wire. This type of continuous casting and rolling machine combines a casting wheel and a belt. It is preferable to use the above from the viewpoint of production efficiency.

(ii) Post-casting cooling step [Step 2]
After the rough wire is drawn by the casting step [step 1], a post-casting cooling step [step 2] is performed in which the wire is cooled at a cooling rate of 60 ° C./s or more and 120 ° C./s or less. If the cooling rate is less than 60 ° C./s, the crystallization of the coarse Ag phase becomes too much, and the crystallization of the fine Ag phase in the first and second heat treatment steps [steps 4 and 5] is greatly reduced. On the other hand, if the cooling rate is set to a value higher than 120 ° C./s, the deposition of the solute (Ag) on the grain boundaries is hindered, and the crystallization of the Ag phase on the grain boundaries is reduced. From the above, by performing the post-casting cooling step [step 2] at 60 ° C./s or more, preferably 80 ° C./s or more and 120 ° C./s or less, the solute (Ag) is present in large amounts near the grain boundaries due to insufficient diffusion due to rapid cooling, and the crystallization of the Ag phase on the grain boundaries that acts as pinning particles can be promoted.

(iii) First wire drawing process [Process 3]
Following the post-casting cooling step [step 2], a first wire drawing step [step 3] is performed in which cold wire drawing is performed at a working ratio of 50% to 90%. In the heat treatment, a sufficient amount of fine Ag phase does not crystallize. In addition, if the processing rate is less than 50%, there is a problem that void defects grow. On the other hand, if the processing rate is more than 90%, the second It is difficult to perform wire drawing at a high processing rate after the heat treatment step [step 5]. Therefore, it is necessary to promote the precipitation of a sufficient amount of fine Ag phase, suppress the growth of voids, and further to perform wire drawing in the subsequent step. In order to ensure sufficient margin for this, the first wire drawing process [process 3] is carried out at a working ratio of 50% or more and 90% or less.

Here, the "working rate" is a value obtained by subtracting the cross-sectional area after processing from the cross-sectional area before drawing, dividing the result by the cross-sectional area before processing, and multiplying the result by 100, and expressed as a percentage, and is expressed by the following formula.
[Processing rate] = {([Cross-sectional area before processing] - [Cross-sectional area after processing]) / [Cross-sectional area before processing]} x 100 (%)

The first wire drawing process [Step 3] can be carried out by a known method such as a draw wire drawing process using a die. The first wire drawing process can be carried out in one pass, or in multiple passes until the desired wire diameter is obtained.

(iv) First heat treatment step [Step 4]
Following the first wire drawing step [step 3], the first heat treatment step [step 4] is performed. In the first heat treatment step [step 4], the holding temperature is kept in the range of 300°C to 400°C for 2 hours to 100 hours, and then the cooling is performed to room temperature at a cooling rate of 90°C/sec or more. By holding at the predetermined temperature, the crystallization of the fine Ag phase is promoted. In addition, by rapidly cooling to room temperature, residual stress derived from the difference in thermal expansion coefficient and the cooling rate difference between the Ag phase and the parent phase obtained up to this step is accumulated, and the precipitation of the Ag phase in the subsequent second heat treatment step [step 5] is promoted. If the holding temperature in the first heat treatment step [step 4] is less than 300°C, the generation of the Ag phase, which is a precipitate, does not occur sufficiently. On the other hand, if the holding temperature in the first heat treatment step [step 4] exceeds 400°C, the Ag phase that is crystallized and precipitated becomes coarse, and the number of Ag phases generated also decreases, so that a sufficient amount of fine Ag phase crystallization is not obtained. In addition, if the cooling rate in the first heat treatment step [step 4] is slow, the difference in the amount of shrinkage between the Ag phase and the parent phase becomes small, making it difficult to effectively accumulate strain. By carrying out the first heat treatment step [step 4] at a holding temperature in the range of 300° C. to 400° C. and cooling at a cooling rate of 90° C./sec or more, the proportion of fibrous fine Ag phases produced can be increased.

(v) Second heat treatment step [Step 5]
Following the first heat treatment step [step 4], a second heat treatment step [step 5] is performed at a temperature higher than that of the first heat treatment step. The second heat treatment step [step 5] is performed at a temperature 25°C or higher than the holding temperature of the first heat treatment step [step 4], and is usually performed at a holding temperature in the range of 400 to 600°C for a holding time of 2 hours to 100 hours. In addition, for cooling after holding at a predetermined temperature, natural cooling in a furnace with heating stopped is preferable in order to improve workability in the subsequent wire drawing step. By performing the second heat treatment step [step 5] at a higher temperature after the first heat treatment step [step 4], precipitation and recrystallization of residual solid solution elements are promoted due to the effect of improved diffusivity and accumulated strain during cooling.

The holding time in the first heat treatment step and the second heat treatment step is preferably in the range of 10 hours to 100 hours in total. By carrying out two-step heat treatment, the first heat treatment step [step 4] and the second heat treatment step [step 5], the fine and abundant Ag phase is formed, which forms a high-density fibrous fine Ag phase after wire drawing, resulting in high strength. In addition, by going through the recrystallization step, which is the second heat treatment step [step 5], the workability in the subsequent wire drawing step can be improved and breakage during thinning can be prevented. If the holding temperature and holding time do not meet the above-mentioned specified conditions, precipitation insufficiency occurs due to the delayed diffusion of the solute (Ag), and the crystallization and precipitation of the Ag phase is greatly reduced. In addition, from the viewpoint of preventing deterioration of surface quality due to oxidation, etc. caused by the heat treatment step, a peeling step may be included after the second heat treatment step [step 5].

The above-mentioned first heat treatment step [step 4] and second heat treatment step [step 5] can be carried out using known methods, such as batch heat treatment, high-frequency heating, electric current heating, running heating, and other continuous heat treatments. Cooling after the first heat treatment step [step 4] is preferably carried out by spraying a quenching liquid such as oil or water, immersion in such a liquid, or cooling by a jet of non-oxidizing gas in order to obtain the desired cooling rate.

(vi) Second wire drawing process [Process 6]
After cooling after the second heat treatment step [step 5], a second wire drawing step [step 6] is performed in which cold wire drawing is performed at a working ratio of 99.7% or more and 99.998% or less. If the drawing ratio is less than 99.7%, the strength will not be increased sufficiently. On the other hand, it is difficult to increase the drawing ratio to more than 99.998%. Therefore, the second drawing step [step 6] is performed. is carried out at a processing rate of 99.7% or more and 99.998% or less.

The second wire drawing process can be carried out by a known method such as a draw wire drawing process using a die. The second wire drawing process can be carried out in one pass or multiple passes until the desired wire diameter is obtained.

The above-mentioned manufacturing method is primarily a method for manufacturing circular round wire, but ribbon-shaped ribbon wire can be manufactured by rolling the circular round wire manufactured by the above-mentioned manufacturing method to a specified thickness.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and includes all aspects included in 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.

Next, examples and comparative examples will be described, but the present invention is not limited to these examples.

1. Experiment 1: Production and Evaluation of Cu-Ag Alloy Wire Cu-Ag alloy wires of the examples and comparative examples were produced by the production method described below.

<Production Method>
(Examples 1-1 to 1-11)
A raw material of Cu-1.0 mass% Ag was melted in air, and the ingot was cast into a roughly drawn wire, which was then subjected to a post-casting cooling step and a first wiredrawing step under the conditions shown in Table 1. Next, a first heat treatment step, a second heat treatment step, and natural cooling in the furnace after heating was stopped in the second heat treatment step were performed under the conditions shown in Table 1, followed by a second wiredrawing step, to obtain Cu-Ag alloy wires of Examples 1-1 to 1-11. Note that, with regard to Example 1-9 which is a ribbon wire, it was once manufactured as a round wire and then formed into a ribbon wire having the dimensions shown in Table 5.

(Comparative Examples 1-1 to 1-11)
Among Comparative Examples 1-1 to 1-11, the first heat treatment step and the second heat treatment step were not performed for Comparative Example 1-1 and 1-2, the second heat treatment step was not performed for Comparative Example 1-4, and the first heat treatment was not performed for Comparative Example 1-5. Except for this, the Cu-Ag-based alloy wires of Comparative Examples 1-1 to 1-11 were produced under the conditions shown in Table 1 by the same procedures as those of Examples 1-1 to 1-11.

(Examples 2-1 to 2-11)
A raw material of Cu-2.0 mass% Ag was melted in air, and the ingot was cast into a roughly drawn wire, and then a post-casting cooling step and a first wiredrawing step were carried out under the conditions shown in Table 2. Next, a first heat treatment step, a second heat treatment step, and a second wiredrawing step were carried out under the conditions shown in Table 2, after which the wire was naturally cooled in the furnace after heating was stopped in the second heat treatment step, to obtain Cu-Ag alloy wires of Examples 2-1 to 2-11. Note that, with regard to Example 2-9 which is a ribbon wire, it was once manufactured as a round wire, and then formed into a ribbon wire having the dimensions shown in Table 6.

(Comparative Examples 2-1 to 2-11)
Among the comparative examples 2-1 to 2-11, the first heat treatment step and the second heat treatment step were not performed for the comparative examples 2-1 and 2-2, the second heat treatment step was not performed for the comparative example 2-4, and the first heat treatment was not performed for the comparative example 2-5. Except for this, the Cu-Ag-based alloy wires of the comparative examples 2-1 to 2-11 were produced under the conditions shown in Table 2 by the same procedures as those of the examples 2-1 to 2-11.

(Examples 3-1 to 3-11)
A raw material of Cu-4.0 mass% Ag was melted in air, and the ingot was cast into a roughly drawn wire, and then a post-casting cooling step and a first wiredrawing step were carried out under the conditions shown in Table 3. Next, a first heat treatment step, a second heat treatment step, and a second wiredrawing step were carried out under the conditions shown in Table 3, after which the wire was naturally cooled in the furnace after heating was stopped in the second heat treatment step, to obtain Cu-Ag alloy wires of Examples 3-1 to 3-11. Note that, with regard to Example 3-9 which is a ribbon wire, it was once manufactured as a round wire, and then formed into a ribbon wire having the dimensions shown in Table 7.

(Comparative Examples 3-1 to 3-11)
Among Comparative Examples 3-1 to 3-11, the first heat treatment step and the second heat treatment step were not performed for Comparative Examples 1-1 and 1-2, the second heat treatment step was not performed for Comparative Example 1-4, and the first heat treatment was not performed for Comparative Example 1-5. Except for this, the Cu-Ag-based alloy wires of Comparative Examples 3-1 to 3-11 were produced under the conditions shown in Table 3 by the same procedures as those of Examples 3-1 to 3-11.

(Examples 4-1 to 4-11)
A raw material of Cu-6.0 mass% Ag was melted in air, and the ingot was cast into a roughly drawn wire, and then a post-casting cooling step and a first wiredrawing step were carried out under the conditions shown in Table 4. Next, a first heat treatment step, a second heat treatment step, and a second wiredrawing step were carried out under the conditions shown in Table 4, after which the wire was naturally cooled in the furnace after heating was stopped in the second heat treatment step, to obtain Cu-Ag alloy wires of Examples 4-1 to 4-11. Note that, with regard to Example 4-9 which is a ribbon wire, it was once manufactured as a round wire, and then formed into a ribbon wire having the dimensions shown in Table 8.

(Comparative Examples 4-1 to 4-11)
Among Comparative Examples 4-1 to 4-11, the first heat treatment step and the second heat treatment step were not performed for Comparative Example 4-1 and 4-2, the second heat treatment step was not performed for Comparative Example 4-4, and the first heat treatment was not performed for Comparative Example 4-5. Except for this, the Cu-Ag-based alloy wires of Comparative Examples 4-1 to 4-11 were produced under the conditions shown in Table 4 by the same procedures as those of Examples 4-1 to 4-11.

[Evaluation method]
The Cu-Ag alloy wires of the examples and comparative examples produced above were evaluated by the following evaluation methods.

[1] Tensile test (final product)
A tensile test was carried out on the final Cu-Ag alloy wire. The test specimen shape was the original wire shape, so it did not conform to JIS Z2201, but the test conditions were in accordance with JIS Z2241, and the average value of the measurement results (n=2) was taken as the tensile strength result.

The increase in tensile strength (MPa) was calculated based on the tensile strength of Cu-Ag alloy wires (Comparative Example 1-1, Comparative Example 2-1, Comparative Example 3-1, Comparative Example 4-1) manufactured by a conventional manufacturing method that did not perform the first and second heat treatment steps, and used as the evaluation of the tensile test. The evaluation criteria were that an increase in tensile strength (MPa) of 100 MPa or more was passed (good), and in particular, an increase of 150 MPa or more was passed (excellent).

[2] Tensile test (after reheat treatment)
A tensile test was carried out to measure the tensile strength of the Cu-Ag alloy wire, which is the final product, after heat treatment at 250°C for 30 minutes as the tensile strength after long-term use in a heated state. The tensile test was carried out in the same manner as in the above "[1] Tensile test (final product)". The above heat treatment conditions, when converted to heat treatment at about 80°C, which is the heat generation temperature when current is applied according to the Larson-Miller parameters, result in a treatment time that greatly exceeds the product life, and it can be considered that the Cu-Ag alloy wire after a long period of use in a heated state was measured.

The tensile test evaluation was performed by comparing the tensile strength after reheat treatment with that of a control Cu-Ag alloy wire manufactured by a conventional manufacturing method that does not perform the first and second heat treatment steps. The tensile strength after reheat treatment shown in Tables 5 to 8 was evaluated by subtracting the tensile strength after reheat treatment of the control Cu-Ag alloy wires of the same composition (Comparative Example 1-1, Comparative Example 2-1, Comparative Example 3-1, Comparative Example 4-1) from the measured tensile strength after reheat treatment. The evaluation criteria were as follows: a value 100 MPa or higher higher than the target Cu-Ag alloy wire was considered to be pass (good), and a value 150 MPa or higher was considered to be pass (excellent).

[3] Measurement of Electrical Conductivity The electrical conductivity was measured for two of each test piece in a thermostatic chamber controlled at 20°C (±1°C) using the four-terminal method based on JIS H0505-1975, and the average value (% IACS) was taken as the measured value. The distance between the terminals was 100 mm.

In the evaluation, for Cu-1.0% by mass Ag, a conductivity of 75% IACS or more was considered to be passable, and 80% IACS or more was considered to be excellent. For Cu-2.0% by mass Ag, a conductivity of 70% IACS or more was considered to be passable, and 75% IACS or more was considered to be excellent. For Cu-4.0% by mass Ag, a conductivity of 60% IACS or more was considered to be passable, and 65% IACS or more was considered to be excellent. For Cu-6.0% by mass Ag, a conductivity of 50% IACS or more was considered to be passable, and 55% IACS or more was considered to be excellent.

It has long been known that the tensile strength of Cu-Ag alloy wire can be controlled by increasing or decreasing the Ag content, and since Cu-Ag alloy wires with different strengths for each Ag content are used for different purposes, the above evaluation criteria set different conductivity evaluation criteria for each Ag content.

[4] Structure observation Prior to image analysis of the metal structure, a scanning transmission electron microscope (STEM) was used to obtain a STEM bright-field image and a STEM dark-field image. The measurement sample was obtained by thinning the sample using a focused ion beam method (FIB: Focused Ion Beam method) on a cross section perpendicular to the longitudinal direction of the Cu-Ag alloy wire, and the processing was performed using SIINT-3050TB (manufactured by SII NanoTechnology Co., Ltd.) with an acceleration voltage of 30 kV for the Ga ion beam. After processing, in order to remove damage to the sample, Ar ion milling was performed for 5 minutes with an acceleration voltage of 2 kV. The processed sample was observed in a cross section perpendicular to the longitudinal direction using a STEM (JEM-ARM200F, manufactured by JEOL Ltd.). The condition of the STEM observation was an electron beam acceleration voltage of 200 kV. The observation area was a square with one side of 130 nm or more, and a STEM bright-field image and a STEM dark-field image (high-angle scattering dark-field image) of the area were taken.

[5] Calculation of the number ratio of fibrous fine Ag phase The image processing software "Image J (version v1.53k)" was used for the acquired STEM dark field image to binarize the Ag phase, which is a precipitate, and calculate its average diameter as follows. First, an arbitrary range of 400 to 800 nm ² was trimmed from the dark field image, and this image was grayscaled. Next, in the histogram of the brightness value of this image, the upper 3 to 6% was used as a threshold, and the low brightness side was binarized to white and the high brightness side to black. Furthermore, black parts of 10 pixels or less were removed as noise, and the remainder was considered to be Ag phase precipitates. After calculating the number of pixels of each precipitate and converting it to an area, the diameter D of each precipitate, i.e., the Ag phase, was obtained by assuming each precipitate to be a perfect circle and calculating the diameter from the area. The total number of Ag phases in the measurement range was then counted, and the number within the range of formula (1) was counted and divided by the total number to calculate the proportion of fibrous fine Ag phases.

[6] Calculation of the number ratio of Ag phase on grain boundary The acquired STEM bright field image was subjected to binarization processing using the image processing software "Image J (version v1.53k)" to determine the position of the grain boundary. An arbitrary range of 400 to 800 nm ² was trimmed from the bright field image, and this image was grayscaled. Next, in the histogram of the brightness value of this image, the top 10% was used as a threshold to binarize, and the high brightness side was white and the low brightness side was black. The black part that continued in the longitudinal direction for 15 nm or more and had a short side length of 5 nm or less was determined to be the position of the grain boundary. In addition, the image processing software "Image J" was used to extract Ag phase precipitates from the STEM dark field image in the procedure shown in "[5] Calculation of the number ratio of fibrous fine Ag phase". An arbitrary range of 400 to 800 nm ² of the dark field image was trimmed, and this image was grayscaled. Next, in the histogram of the brightness values of this image, the brightness values of the top 10% and the top 2% were compared, and when the difference was 25 or more, the top 2% was used as a threshold for binarization. At that time, the low brightness side was made white and determined to be the parent phase, and the high brightness side was made black. Furthermore, 10 pixels or less of the binarized black part was removed as noise, and the remaining part was determined to be Ag phase precipitates. By comparing with the position of the determined grain boundary, Ag phases that overlap even a part of the line indicating the grain boundary were regarded as precipitates on the grain boundary, and Ag phases that did not overlap at all were regarded as precipitates within the grains rather than on the grain boundary, and the number of Ag phases on the grain boundary was counted and divided by the number of Ag phases in the entire measurement range to calculate the number ratio of Ag phases on the grain boundary.

As shown in Tables 1 and 5, in the case of a Cu-Ag alloy wire with an Ag content of 1.0 mass%, sufficient electrical conductivity was confirmed in Examples 1-1 to 1-11, where the number ratio of Ag phases in formula (1) was 50% or more, and high tensile strength was confirmed compared to Comparative Example 1-1 (tensile strength: 920 MPa, tensile strength after reheat treatment: 720 MPa), and it was confirmed that the tensile strength was sufficiently high even after reheat treatment.

In addition, in Examples 1-1 and 1-3 to 1-11, in which the proportion of Ag phases on the grain boundaries was 15% or more and 35% or less, the increase in tensile strength after reheat treatment was particularly large, and it was confirmed that the tensile strength was excellent.

As shown in Tables 2 and 6, in the case of a Cu-Ag alloy wire with an Ag content of 2.0 mass%, in Examples 2-1 to 2-11 in which the number ratio of the Ag phase in formula (1) is 50% or more, sufficient electrical conductivity and sufficiently high tensile strength compared to Comparative Example 2-1 (tensile strength: 1020 MPa, tensile strength after reheat treatment: 860 MPa) were confirmed, and it was confirmed that the tensile strength was sufficiently high even after reheat treatment.

In addition, in Examples 2-1 and 2-3 to 2-11, in which the proportion of Ag phases on the grain boundaries was 15% or more and 35% or less, the increase in tensile strength after reheat treatment was particularly large, confirming that the tensile strength was excellent.

As shown in Tables 3 and 7, in the case of a Cu-Ag alloy wire with an Ag content of 4.0 mass%, Examples 3-1 to 3-11, in which the number ratio of the Ag phase in formula (1) is 50% or more, were confirmed to have sufficient electrical conductivity and sufficiently high tensile strength compared to Comparative Example 3-1 (tensile strength: 1235 MPa, tensile strength after reheat treatment: 1060 MPa), and it was confirmed that the tensile strength was sufficiently high even after reheat treatment.

In addition, in Examples 3-1 and 3-3 to 3-11, in which the proportion of Ag phases on the grain boundaries was 15% or more and 35% or less, the increase in tensile strength after reheat treatment was particularly large, confirming that the tensile strength was excellent.

As shown in Tables 4 and 8, in the case of a Cu-Ag alloy wire with an Ag content of 6.0 mass%, in Examples 4-1 to 4-11 in which the number ratio of the Ag phase in formula (1) is 50% or more, sufficient electrical conductivity and sufficiently high tensile strength compared to Comparative Example 4-1 (tensile strength: 1470 MPa, tensile strength after reheat treatment: 1270 MPa) were confirmed, and it was confirmed that the tensile strength was sufficiently high even after reheat treatment.

In addition, in Examples 4-1 and 4-3 to 4-11, in which the proportion of Ag phases on the grain boundaries was 15% or more and 35% or less, the increase in tensile strength after reheat treatment was particularly large, and it was confirmed that the tensile strength was excellent.

2. Experiment 2: Manufacturing and evaluation of Cu-Ag alloy wire containing additive elements Except for adding the predetermined amount of the secondary additive elements shown in Table 9, the Cu-Ag alloy wires of Examples 5-1 to 5-8 and Comparative Example 5-1 were manufactured under the manufacturing conditions shown in Table 9 in the same manner as in Examples 2-1 to 2-11 of Experiment 1, and were evaluated in the same manner as in Experiment 1. Comparative Example 5-1 was used as a control for the tensile test.

As shown in Tables 9 and 10, even in the case of Cu-Ag alloy wires to which the additional element was added in the range of 0.05% by mass to 0.30% by mass, sufficient electrical conductivity was confirmed in Examples 5-1 to 5-8, in which the number ratio of Ag phases in formula (1) was 50% or more, and sufficiently high tensile strength was confirmed compared to Comparative Example 5-1 (tensile strength: 1060 MPa, tensile strength after reheat treatment: 900 MPa), and it was confirmed that the tensile strength was sufficiently high even after reheat treatment.

In addition, in Examples 5-1 to 5-8, in which the proportion of Ag phases on the grain boundaries was 15% or more and 35% or less, the increase in tensile strength after reheat treatment was particularly high, confirming that the tensile strength was excellent.

In addition, as shown in Table 11, compared to Example 2-1, which had the same Ag content of 2.0 mass% and was produced under the same conditions, Examples 5-1 to 5-8, which were produced with the addition of additional additive elements, had higher tensile strength and tensile strength after reheat treatment, confirming that it is possible to increase both the tensile strength and the tensile strength after reheat treatment by adding additional additive elements.

1 Cu phase 2 Coarse Ag phase 2f Fibrous coarse Ag phase 3 Fine Ag phase 3f Fibrous

fine Ag phase

10, 10a, 10b, 10c, 20, 20a, 20b Cu-Ag alloy material

Claims

A Cu-Ag based alloy wire containing 1 mass % or more and 6 mass % or less of Ag, with the remainder being composed of Cu and unavoidable impurities,
The Cu-Ag alloy wire has a metal structure including a Cu phase as a parent phase and a plurality of Ag phases as a second phase,
When the cross-sectional area of the cross section perpendicular to the longitudinal direction of the Cu—Ag based alloy wire is σ (μm 2 ) and the diameter of a perfect circle having the same area as each of the Ag phases present in the cross section is D (μm), the following formula (1) can be obtained:

(In formula (1), π represents the ratio of the circumference of a circle to its circumference.)
and the number of Ag phases having a diameter D of less than 5 nm accounts for 50% or more of the total number of Ag phases.
In the cross section of the Cu-Ag based alloy wire,
2. The Cu-Ag alloy wire according to claim 1, wherein the number of Ag phases present on the crystal grain boundaries of the Cu phase is 15% or more and 35% or less of the total number of Ag phases.
The Cu-Ag alloy wire according to claim 1, wherein the composition further contains at least one additional element selected from the group consisting of Sn, Mg, Zn, In, Ni, Co, Zr and Cr, each in a range of 0.05% by mass to 0.3% by mass.
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 wire diameter of 0.01 mm or more and 0.08 mm or less.
The 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 substantially rectangular cross-sectional shape with a width of 0.02 mm to 0.32 mm and a thickness of 0.002 mm to 0.04 mm.