Cu-Ni-Co-Si-BASED COPPER ALLOY, TERMINAL, AND ELECTRONIC COMPONENT

Abstract

The purpose of the present disclosure is to provide a Cu-Ni-Co-Si-based copper alloy having high strength and improved bending workability. Provided is a Cu-Ni-Co-Si-based copper alloy containing 1.0-4.0 mass% of Ni, 0.1-1.0 mass% of Si, and 0.0-1.5 mass% of Co, the balance being Cu and unavoidable impurities. With regard to KAM values measured by EBSD, the proportion of KAM values ranging from 0° to 1° is 10-50%.

Description

Cu-Ni-Co-Si based copper alloy, terminal, and electronic component

[0001] The present disclosure relates to a Cu—Ni—Co—Si-based copper alloy, a terminal, and an electronic component.

[0002] Solid-solution-strengthened alloys such as brass and phosphor bronze have traditionally been used as materials for terminals and connectors. As electronic devices become more powerful, copper alloys used therein are required to have improved strength and electrical conductivity. Therefore, precipitation-strengthened copper alloys (e.g., Corson alloys) have been used, which have superior strength and electrical conductivity compared to conventional solid-solution-strengthened copper alloys. Precipitation-strengthened copper alloys are formed by aging a solution-treated supersaturated solid solution, resulting in uniform dispersion of fine precipitates, increasing the alloy's strength, and reducing the amount of solute elements in the copper, improving electrical conductivity. Therefore, precipitation-strengthened copper alloys can have excellent mechanical properties and electrical conductivity. Cu—Ni—Si-based copper alloys, a type of Corson alloy, have been developed as precipitation-strengthened copper alloys. Patent Document 1 discloses Cu—Ni—Si-based copper alloy strips used for manufacturing electronic components such as electronic materials, which have high strength and excellent bending workability.

[0003] Japanese Patent Application Laid-Open No. 2006-16629

[0004] However, conventional techniques are required to further improve bending workability. An object of the present disclosure is to provide a Cu-Ni-Co-Si-based copper alloy having high strength and improved bending workability, a terminal including the copper alloy, and an electronic component including the terminal.

[0005] The Cu-Ni-Co-Si-based copper alloy of the present disclosure contains 1.0 to 4.0 mass% Ni, 0.1 to 1.0 mass% Si, and 0.0 to 1.5 mass% Co, with the balance being Cu and unavoidable impurities, and in the KAM value measured by EBSD, the proportion of the KAM value being 0 to 1° is 10% or more and 50% or less.

[0006] A terminal of the present disclosure includes the Cu—Ni—Co—Si-based copper alloy. An electronic component of the present disclosure includes the terminal.

[0007] According to the present disclosure, it is possible to provide a Cu-Ni-Co-Si-based copper alloy having high strength and improved bending workability, a terminal including the copper alloy, and an electronic component including the terminal.

[0008] Hereinafter, a Cu—Ni—Co—Si-based copper alloy according to an embodiment of the present disclosure will be described. In the present disclosure, “A to B” means “A or more and B or less.”

[0009] The present disclosure can be embodied in the following aspects. [1] A Cu-Ni-Co-Si-based copper alloy containing 1.0 to 4.0 mass% Ni, 0.1 to 1.0 mass% Si, and 0.0 to 1.5 mass% Co, with the balance being Cu and unavoidable impurities, wherein, in a KAM value measured by EBSD, a proportion of the KAM value within a range of 0 to 1° is 10% or more and 50% or less. [2] A Cu-Ni-Co-Si-based copper alloy according to [1], having a crystal grain size of 10.0 μm or less. [3] A Cu-Ni-Co-Si-based copper alloy according to [2], having a crystal grain size of 6.00 μm or less. [4] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [3], having a proportion of the KAM value within a range of 0 to 1° is 35% or more and 45% or less. [5] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [4], having a thickness of 0.05 mm or more and 0.40 mm or less. [6] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [5], having a 0.2% proof stress of 900 MPa or more in a direction parallel to the rolling direction measured in accordance with JIS-Z2241. [7] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [6], having a 0.2% proof stress of 900 MPa or more in a direction perpendicular to the rolling direction measured in accordance with JIS-Z2241. [8] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [7], having an electrical conductivity of 35% IACS or more at 25°C measured in accordance with JIS-H0505. [9] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [8], wherein the mass ratio of Ni to Si is 3.5 to 5.0.

[10] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to [9], further containing at least one element selected from the group consisting of Mg, Mn, Sn, Zn, and Cr in a total amount of 0.0050 to 1.0 mass%.

[11] A Cu-Ni-Co-Si-based copper alloy according to any one of [1] to

[10] , further containing at least one element selected from the group consisting of P, B, Ti, Zr, Al, Fe, and Ag in a total amount of 0.0050 to 1.0 mass%.

[12] A terminal comprising the Cu-Ni-Co-Si-based copper alloy according to any one of [1] to

[11] .

[13] An electronic component comprising the terminal according to

[12] .

[0010] The Cu—Ni—Co—Si-based copper alloy of the present disclosure (hereinafter also referred to as the “copper alloy of the present disclosure”) contains 1.0 to 4.0 mass % Ni, 0.1 to 1.0 mass % Si, and 0.0 to 1.5 mass % Co, with the remainder being Cu and unavoidable impurities. In the KAM value measured by EBSD, the proportion of KAM values ​​of 0 to 1° is 10% or more and 50% or less. According to the above configuration, a Cu—Ni—Co—Si-based copper alloy having high strength and improved bending workability can be obtained. In recent years, with the miniaturization and increased current of terminals and the like, there has been a demand for materials having high strength and high conductivity. Furthermore, terminals used in electronic components have seen an increase in the number of leads and a narrower pitch. This has led to demands for strict bending workability for materials used in electronic components. The Cu—Ni—Co—Si-based copper alloy of the present disclosure has not only high strength but also high bending workability.

[0011] (Composition) [Ni and Si] The copper alloy of the present disclosure contains 1.0 to 4.0 mass% Ni and 0.1 to 1.0 mass% Si, based on 100 mass% of the copper alloy. Ni forms an intermetallic compound with Si by appropriate heat treatment. This allows the strength of the copper alloy to be improved without deteriorating its electrical conductivity. If the Ni or Si content is less than the above range, the effect of improving strength cannot be obtained, and if it exceeds the above range, electrical conductivity and hot workability decrease. In the copper alloy of the present disclosure, the mass ratio of Ni to Si (hereinafter referred to as the "Ni / Si ratio") may be 3.5 to 5.0. If the Ni / Si ratio is 3.5 or more and if the Ni / Si ratio is 5.0 or less, the copper alloy can have high electrical conductivity.

[0012] [Co] The copper alloy of the present disclosure contains 0.0 to 1.5 mass % of Co. If the Co content exceeds 1.5 mass %, the Co that is unable to form intermetallic compounds with Ni and Si acts to reduce electrical conductivity, and hot workability is reduced.

[0013] [Other Additional Elements] The copper alloy of the present disclosure may further contain at least one element selected from the group consisting of Mg, Mn, Sn, Zn, and Cr (hereinafter referred to as the "first additional element") in a total amount of 0.0050 to 1.0 mass%. The copper alloy of the present disclosure may preferably contain 0.050 mass% or more and / or 0.50 mass% or less of the first additional element. Mg can improve the strength and stress relaxation resistance of the copper alloy. Mn can improve the strength and hot workability of the copper alloy. Sn can improve the strength of the copper alloy. Zn can improve the heat resistance of solder joints. Like Ni, Cr forms a compound with Si and undergoes precipitation hardening, thereby improving strength without degrading electrical conductivity. If the total amount of the first additional element is less than the above range, the above-mentioned effects are difficult to achieve. Furthermore, if the total amount of the first additional element exceeds the above range, electrical conductivity may be reduced. The copper alloy of the present disclosure may preferably contain 0.010% by mass or more and / or 0.2% by mass or less of the first additional element.

[0014] The copper alloy of the present disclosure may further contain at least one element selected from the group consisting of P, B, Ti, Zr, Al, Fe, and Ag (hereinafter referred to as the "second additional element") in a total amount of 0.0050 to 1.0 mass %. This can improve product properties such as electrical conductivity, strength, stress relaxation properties, and plating ability. If the total amount of the second additional element is less than the above range, the above-mentioned effects cannot be obtained, and if it exceeds the above range, electrical conductivity may be reduced. The copper alloy of the present disclosure may preferably contain 0.010 mass % or more and / or 0.20 mass % or less of the second additional element. The copper alloy of the present disclosure may not contain the second additional element, but may contain the first additional element. Alternatively, the copper alloy of the present disclosure may not contain the first additional element, but may contain the second additional element. The copper alloy of the present disclosure may contain both the first additional element and the second additional element.

[0015] [Balance] The balance of the copper alloy of the present disclosure (i.e., other than the above-mentioned elements) consists of Cu and inevitable impurities. Examples of inevitable impurities include S and O. The content of each element contained as an inevitable impurity is not particularly limited, but is, for example, 100 ppm by mass or less. The lower limit of each element of the inevitable impurities is not particularly limited, but is typically 0 ppm by mass or more.

[0016] The composition of the copper alloy can be measured by X-ray fluorescence analysis. The X-ray fluorescence analyzer used can be a Rigaku Simultix 14 or an equivalent device. The analysis surface can be machined or mechanically polished to a maximum surface roughness Rz (JIS-B0601 (2013)) of 6.3 μm or less. When collecting an analysis sample from the molten metal during melting and casting, the sample can be cast into a shape of approximately 30 to 40 mm diameter and 50 to 80 mm thick, then cut to a thickness of approximately 10 to 20 mm, and the cut surface can be used as the analysis surface. The composition of the copper alloy can also be measured by wet analysis. Ni can be determined using the copper separation dimethylglyoxime gravimetric method (JIS-H1056 (2003)), and Si can be determined using the silicon dioxide gravimetric method (JIS-H1061 (2006)). Other additive elements and impurity elements can be determined using ICP atomic emission spectroscopy. In the case of ICP optical emission spectroscopy, the measurement may be performed using an ICP optical emission spectroscopy analyzer (ICP-OES) SPS3100 manufactured by Hitachi High-Tech Science Corporation or an equivalent device. In the case of ICP optical emission spectroscopy, a copper alloy sample may be dissolved in a mixed acid containing hydrochloric acid, nitric acid, and water in a volume ratio of 2:1:2, and then diluted.

[0017] (Shape) The shape of the copper alloy is not particularly limited, and can be, for example, a copper alloy sheet obtained by a manufacturing method including a rolling process as described below. The copper alloy sheet is not particularly limited as long as it is an object having a three-dimensional shape with a certain thickness, and also includes, for example, strip, plate, and foil as defined in JIS H 0500. A "strip" (strip, ribbon) can mean "a slit coil shape with a substantially uniform thickness and a rectangular cross section." A "sheet" (plate) can mean "a sheared or sawed shape with a substantially uniform thickness and a rectangular cross section," and may also be flat. A plate having a thin thickness (e.g., 0.10 mm or less) can also be called a "foil." The copper alloy of the present disclosure may be in the form of a plate. That is, the copper alloy of the present disclosure may be a copper alloy sheet. The thickness of the copper alloy of the present disclosure can be, for example, 0.04 mm or more and 0.40 mm or less, or 0.05 mm or more and 0.40 mm or less.

[0018] (0.2% Yield Strength) The copper alloy of the present disclosure may have a 0.2% yield strength of 900 MPa or more in the direction parallel to the rolling direction, measured in accordance with JIS-Z2241. In order to respond to further miniaturization and thinning of electrical and electronic components using Cu-Ni-Co-Si-based copper alloys, a strength level of 0.2% yield strength of 900 MPa or more in the direction parallel to the rolling direction (LD) is desired. Therefore, the copper alloy of the present disclosure is suitable for use in small and thin-walled electrical and electronic components.

[0019] In the copper alloy of the present disclosure, the 0.2% proof stress in the direction parallel to the rolling is more preferably 950 MPa or more, and may be, for example, 966 MPa or more. The upper limit of the 0.2% proof stress in the direction parallel to the rolling is not particularly limited, but may typically be 1200 MPa or less. In the copper alloy of the present disclosure, the 0.2% proof stress in the direction perpendicular to the rolling measured in accordance with JIS-Z2241 may be 900 MPa or more. Preferably, the 0.2% proof stress in the direction perpendicular to the rolling may be 915 MPa or more. Specific conditions for the tensile test to measure the 0.2% proof stress may be the conditions described in the Examples section below. As a tensile tester used for the tensile test, an Autocom AC-100KN-C manufactured by TSE Corporation or an equivalent device can be used.

[0020] (Tensile Strength) The copper alloy of the present disclosure may have a tensile strength of 900 MPa or more in the direction parallel to the rolling, measured in accordance with JIS-Z2241. In the copper alloy of the present disclosure, the tensile strength in the direction parallel to the rolling is more preferably 950 MPa or more, and may be, for example, 991 MPa or more. The upper limit of the tensile strength in the direction parallel to the rolling is not particularly limited, but may typically be 1200 MPa or less. In the copper alloy of the present disclosure, the tensile strength in the direction perpendicular to the rolling may be 900 MPa or more. Preferably, the tensile strength in the direction perpendicular to the rolling may be 950 MPa or more, or may be 961 MPa or more. Specific conditions for a tensile test to measure the tensile strength may be the conditions described in the Examples section below. As a tensile tester used for the tensile test, an Autocom AC-100KN-C manufactured by TSE Corporation or an equivalent device can be used.

[0021] (Electrical Conductivity) The copper alloy of the present disclosure may have an electrical conductivity of 35% IACS or more at 25°C measured in accordance with JIS-H0505. In the copper alloy of the present disclosure, the electrical conductivity is more preferably 40% IACS or more, and may be, for example, 40.6% IACS or more. Specific conditions for measuring electrical conductivity may be those described in the Examples section below.

[0022] (Area Fraction of Cube Orientation) In the copper alloy of the present disclosure, the area fraction of the Cube orientation may be greater than 0% and not greater than 10%. Generally, the greater the area fraction of the Cube orientation in a Cu—Ni—Co—Si-based copper alloy, the more improved its bending workability can be. The Cu—Ni—Co—Si-based copper alloy of the present disclosure has a relatively low area fraction of the Cube orientation, but has high bending workability. In the copper alloy of the present disclosure, the area fraction of the Cube orientation may be greater than 0% and not greater than 5%, or may be 2% or greater and not greater than 4%. The Cube orientation is the orientation of crystal grains in which the {001} plane is parallel to the rolled surface and the <100> direction is parallel to the rolling direction (RD), and is represented by the index {001}<100>. The area fraction of the Cube orientation refers to the area fraction of the Cube orientation {001}<100>. The rolling direction means a direction parallel to the direction in which the workpiece passes between a pair of work rolls.

[0023] The area ratio of the Cube orientation is measured by EBSD (Electron Backscatter Diffraction). EBSD is a technique for analyzing crystal orientation using reflected electron Kikuchi line diffraction (Kikuchi pattern) that occurs when a sample is irradiated with an electron beam in a scanning electron microscope (SEM). Electrolytic polishing is performed using the following electrolyte and test conditions to remove a thickness of approximately 1 μm from the sample surface. Next, an observation range of 30 μm × 85 μm, arbitrarily set so that one side of the observation field is parallel to the rolling direction, is scanned with a step size of 0.15 μm to measure the crystal orientation distribution. The measurement position by EBSD is, for example, near the center in the width direction (short side direction) of the copper alloy plate. When measuring the area ratio of the Cube orientation, the measurement location should be set to avoid areas corresponding to abnormalities. Abnormal parts can be identified by observing the sample before electropolishing with an SEM (observation magnification: 100 times), etc. Abnormal parts refer to areas with excessive oil pits, areas with foreign matter or streaks caused by rolling, etc.

[0024] <Electrolyte composition (example)> Distilled water: 250 ml Phosphoric acid: 125 ml Urea: 2.5 g Ethanol grade 1: 125 ml 1-propanol: 25 ml <Electrolytic polishing conditions (example)> Applied voltage: 10 V Current value: 0 to 10 A Electrolysis time: 10 seconds

[0025] <EBSD measurement conditions, etc.> SEM conditions: Equipment: JEOL Ltd. scanning electron microscope (JSM-IT500HR, or equivalent equipment) Beam conditions: Acceleration voltage: 15 kV Working distance: 15 mm Observation magnification: 2500x EBSD equipment conditions: Equipment: JEOL Ltd. crystal orientation analyzer OIM7.1 (MP-Z171591EBS, or equivalent equipment)

[0026] Type of CCD camera: Slow scan CCD camera manufactured by TSL Solutions Co., Ltd. Then, the crystal orientation density function is analyzed, and the area of ​​crystal grains having an orientation within 15° of the Cube orientation is divided by the measured area to obtain the area ratio. The above measurement data is collected using OIM Data Collection manufactured by TSL Solutions Co., Ltd., and the data is analyzed using OIM Analysis V8 manufactured by TSL Solutions Co., Ltd. Note that the information obtained in the orientation analysis by EBSD includes orientation information up to a depth of several tens of nanometers, the depth at which the electron beam penetrates into the sample, but since this is sufficiently small compared to the area being measured, it is reported as an area ratio.

[0027] (KAM Value) In the copper alloy of the present disclosure, the proportion of the KAM value of 0 to 1° is 10% or more and 50% or less. In copper alloys, the size and number of precipitates act as starting points for deformation cracks, affecting bending workability. Materials after solution treatment that have a high proportion of strain with a KAM value of 0 to 1° do not exhibit sufficient age hardening unless they are subjected to a higher temperature heat treatment in the subsequent aging treatment. For this reason, precipitates tend to coarsen during aging treatment, leading to deterioration of bending workability. Note that in the manufacturing method described below, there is a correlation between the KAM value of the material after solution treatment and the KAM value of the material after stress relief annealing (hereinafter also referred to as the product). The KAM value is an index that represents the amount of lattice strain within crystal grains.

[0028] As a result of analyzing the KAM value, five ratios of "0 to 1°", "1 to 2°", "2 to 3°", "3 to 4°", and "4 to 5°" are calculated, but in the present disclosure, attention is focused on "0 to 1°". This is because it is thought that the strain ratio of 0 to 1° is strongly related to the amount of strain and the ratio of precipitation sites on the material surface, and particularly suggests that it influences the size and amount of precipitates during aging treatment.

[0029] If the proportion of the product with a KAM value of 0 to 1° is less than 10%, it suggests that the proportion of the product with a KAM value of 0 to 1° after solution treatment was too low (excessive strain). This is thought to be due to insufficient recrystallization during solution treatment, in which case strength does not increase with aging treatment. If the proportion of the product with a KAM value of 0 to 1° is more than 50%, it suggests that the proportion of the product with a KAM value of 0 to 1° after solution treatment was too high (excessive strain). If strain is low, aging treatment must be performed at a high temperature to achieve the desired age hardening, which results in coarsening of precipitates and deterioration of the product's bending workability. It is preferable that the proportion of the product with a KAM value of 0 to 1° be 35% or more and 45% or less.

[0030] The KAM value is measured by EBSD. Electrolytic polishing is performed under the same conditions as those described for measuring the area ratio of Cube orientation, and a thickness of approximately 1 μm is removed from the sample surface. Next, an arbitrarily set observation range of 30 μm x 85 μm is scanned with a step size of 0.15 μm. Analysis is then performed using the Area Fraction method, and the KAM value is measured when boundaries with a crystal orientation difference of more than 5° are considered to be grain boundaries. The KAM value is calculated as the average value over the entire observation range. Data analysis is performed using OIM Analysis V8 manufactured by TSL Solutions Co., Ltd. The proportion of measurement points with a KAM value of 0 to 1° is automatically calculated by the data analysis software, and the calculated value is read.

[0031] (Grain size) In the copper alloy of the present disclosure, the grain size may be 10.0 μm or less. When the grain size is small, the grain boundary length in the entire material increases, allowing for smoother bending. This improves bending workability. In the copper alloy of the present disclosure, the grain size may preferably be 6.00 μm or less, or may be 5.60 μm or less. Note that the grain size refers to the average grain size.

[0032] The crystal grain size is measured by EBSD. Electrolytic polishing is performed under the same conditions as those described for measuring the area ratio of Cube orientation, and a thickness of approximately 1 μm is removed from the sample surface. Next, an observation range of 30 μm x 85 μm is arbitrarily set and scanned at a step size of 0.15 μm. Analysis is then performed using the Area Fraction method, and the average crystal grain size is measured when boundaries with a crystal orientation difference of more than 5° are considered to be crystal grain boundaries. Data analysis is performed using OIM Analysis V8 manufactured by TSL Solutions Co., Ltd.

[0033] (Manufacturing Method) The copper alloy of the present disclosure can be produced, for example, by the following manufacturing process. Melting and casting, homogenization annealing, hot rolling, facing, cold rolling, solution treatment, aging treatment, finish rolling, and stress relief annealing are performed in this order. Before the solution treatment, recrystallization annealing and cold rolling may be performed as needed. Between the stress relief annealing and degreasing, pickling and polishing may be performed as needed. Between the hot rolling and the solution treatment, heat treatment may be performed as needed.

[0034] In the melting and casting process, a copper alloy ingot is produced. Specifically, electrolytic copper is melted in an atmospheric melting furnace, and a predetermined amount of additive elements is added. The molten metal is stirred and then cooled to obtain a copper alloy ingot. Hot rolling may be performed in several passes. The total reduction rate of the hot rolling can be, for example, 85% or more. The reduction rate (%) is expressed as the reduction rate (%) = [(TB - TA) / TB] × 100, where TB is the thickness of the target to be rolled before rolling and TA is the thickness of the target after rolling.

[0035] The solution treatment conditions are preferably such that the annealing furnace is set to 800 to 1050°C and annealing is performed for 1 to 1000 seconds. This allows the crystal grain size to be small and the proportion of KAM values ​​between 0 and 1° to be kept low. The temperature and time of the solution treatment are determined so that the proportion of KAM values ​​between 0 and 1° in the product is 10% or more and 50% or less. Increasing the temperature or lengthening the time increases the proportion of KAM values ​​between 0 and 1°, while decreasing the temperature or shortening the time decreases the proportion of KAM values ​​between 0 and 1°. Furthermore, during solution treatment, it is preferable to cool at a rate of 10°C / second or more.

[0036] Aging treatment is carried out to improve precipitation hardening and electrical conductivity. The conditions for aging treatment are preferably 350 to 600°C and 8 to 48 hours. If the temperature or time exceeds the upper limit, softening occurs, and if it is below the lower limit, strength or electrical conductivity becomes insufficient.

[0037] Finish rolling is carried out for work hardening. The working ratio is preferably 10 to 95%. If the working ratio is 10% or more, the copper alloy can have sufficient strength. If the working ratio is 95% or less, rolling can be performed without saturating the strength, and an extremely long rolling time can be prevented.

[0038] Stress relief annealing is performed to improve low-temperature annealing hardening and electrical conductivity. The conditions for stress relief annealing are preferably 250 to 900°C and 1 second to 36 hours. If the temperature or time exceeds the upper limit, the copper alloy softens, and if it is below the lower limit, the strength or electrical conductivity of the copper alloy becomes insufficient. Stress relief annealing is performed, for example, at 450°C for 1 to 60 seconds using a continuous annealing furnace. Alternatively, stress relief annealing is performed, for example, at 320°C for 1 to 30 hours using a batch annealing furnace.

[0039] (Electronic Components) Terminals can be manufactured using the Cu—Ni—Co—Si-based copper alloy of the present disclosure. Electronic components can be manufactured using the terminals. Examples of electronic components include CPU sockets, type C connectors, lead frames, and FPC connectors.

[0040] <Preparation of Copper Alloys> (Example 1) A solution-treated copper alloy containing the additive elements shown in Table 1 was obtained according to the procedure of the manufacturing method described above. Next, aging treatment, finish rolling, and stress relief annealing were performed in this order. The solution treatment was performed by heating for 21 seconds in an annealing furnace set at a temperature of 1050°C. The aging treatment was performed at 390 to 470°C for 24 hours. The degree of reduction in the finish rolling was set to 20% to 60%. Strain relief annealing was performed continuously at 450°C for 10 seconds. As a result, the copper alloy of Example 1 having the plate thickness shown in Table 1 was obtained.

[0041] (Comparative Example 1) In Comparative Example 1, the solution treatment was performed by heating for 28 seconds in an annealing furnace set at a temperature of 1050°C. The aging treatment was performed at 480 to 560°C for 24 hours. Stress relief annealing was performed in a batch manner at 320°C for 12 hours. Other than these, the copper alloy of Comparative Example 1 was obtained in the same manner as in Example 1. Note that although the stress relief annealing conditions in the Example and Comparative Example were different, both conditions applied the same amount of heat, and therefore it is believed that there was no effect on properties such as strength, electrical conductivity, and bending workability. The composition of the obtained copper alloy was confirmed by fluorescent X-ray analysis. A Simultix 14 manufactured by Rigaku Corporation was used as the fluorescent X-ray analyzer. The analyzed surface was machined or mechanically polished so that the maximum surface roughness Rz (JIS-B0601 (2013)) was 6.3 μm or less. The copper alloys of Example 1 and Comparative Example 1 contained 0.50 mass % or less in total of Cr, Mg, Zn, Fe, and Mn.

[0042] <Evaluation> The obtained copper alloys of the Examples and Comparative Examples were evaluated for the following items: [Electrical Conductivity] For samples in the direction parallel to the rolling direction, electrical conductivity (% IACS) was calculated from the volume resistivity determined at 25°C by a four-terminal method using a double bridge device in accordance with JIS-H0505.

[0043] [0.2% Proof Stress and Tensile Strength] Two types of JIS No. 13B test pieces were prepared using a press so that the tensile direction was parallel to the rolling direction and perpendicular to the rolling direction. A tensile test was conducted on these test pieces in accordance with JIS-Z2241 to measure the 0.2% proof stress and tensile strength. The tensile tester used was an AC-100KN manufactured by TSE Corporation. The tensile test conditions were as follows: test piece width: 12.5 mm, room temperature: 15 to 35°C, tensile speed: 5 mm / min, load cell rating: 10 kN, load range: 5%, return speed: 500 mm / min, and gauge length L: 50 mm.

[0044] [EBSD Measurement] Electrolytic polishing was performed on the copper alloys of the examples and comparative examples using the method described above. EBSD measurement was performed on the obtained samples using a scanning electron microscope (JSM-IT500HR) manufactured by JEOL Ltd. and a crystal orientation analyzer OIM7.1 (MP-Z171591EBS) manufactured by JEOL Ltd. using the method described above. As a result, the area ratio of Cube orientation, KAM value, and crystal grain size were measured. The measurement results are shown in Table 1.

[0045] [Bending Test] As a bending test, W bending was performed with reference to Section "7.3 Bending Test" in JIS-H3100 (2018) "Copper and Copper Alloy Plates." Two rectangular test pieces with a long side length of 30 mm were prepared using a press so that the short side was parallel to the rolling direction. One had a short side length of 0.2 mm, and the other had a short side length of 10 mm. The bending test was performed so that the bending axis was parallel to the rolling direction. In other words, the bending direction was the bad way. Evaluation was performed using MBR / t, which is the ratio of the minimum bend radius MBR (Minimum Bend Radius) at which cracks do not occur to the plate thickness t.

[0046]

[0047] As is clear from Table 1, in the copper alloy of Example 1, the proportion of KAM values ​​between 0 and 1° was 50% or less. Since the copper alloy of Example 1 had a smaller MBR / t value than the copper alloy of Comparative Example 1, it can be said that the bending workability was improved. The small proportion of KAM values ​​between 0 and 1° allows precipitation hardening by aging at a lower temperature. Therefore, it is thought that the precipitates were less likely to coarsen, improving the bending workability. Furthermore, the copper alloy of Example 1 had a 0.2% proof stress of 900 MPa or more in the direction parallel to and perpendicular to the rolling direction. In other words, it can be said that the copper alloy of Example 1 has high strength. Therefore, the copper alloy of Example 1 had improved bending workability while maintaining high strength.

Claims

1. A Cu-Ni-Co-Si based copper alloy containing 1.0-4.0 mass% Ni, 0.1-1.0 mass% Si, and 0.0-1.5 mass% Co, with the remainder being Cu and unavoidable impurities, in which the proportion of KAM values ​​of 0-1° measured by EBSD is 10% or more and 50% or less.

2. The Cu-Ni-Co-Si based copper alloy according to claim 1, wherein the crystal grain size is 10.0 μm or less.

3. The Cu-Ni-Co-Si based copper alloy according to claim 2, wherein the crystal grain size is 6.00 μm or less.

4. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, wherein the proportion of said KAM value being 0 to 1° is 35% or more and 45% or less.

5. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, having a thickness of 0.05 mm or more and 0.40 mm or less.

6. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, which has a 0.2% yield strength in a direction parallel to the rolling direction measured in accordance with JIS-Z2241 of 900 MPa or more.

7. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, which has a 0.2% yield strength in a direction perpendicular to the rolling direction measured in accordance with JIS-Z2241 of 900 MPa or more.

8. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, which has an electrical conductivity of 35% IACS or more at 25° C. as measured in accordance with JIS-H0505.

9. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, wherein the mass ratio of Ni to Si is 3.5 to 5.

0.

10. A Cu-Ni-Co-Si based copper alloy according to claim 1 or 2, further containing at least one element selected from the group consisting of Mg, Mn, Sn, Zn and Cr in a total amount of 0.0050 to 1.0 mass%.

11. The Cu-Ni-Co-Si system copper alloy according to claim 1 or 2, further containing a total amount of 0.0050 to 1.0 mass % of at least one element selected from the group consisting of P, B, Ti, Zr, Al, Fe and Ag.

12. A terminal comprising the Cu-Ni-Co-Si based copper alloy according to claim 1 or 2.

13. An electronic component comprising the terminal according to claim 12.