Copper alloy and electronic component

Abstract

Provided is a copper alloy having improved bending formability. A copper alloy according to the present disclosure contains 0.50-3.0 mass% of Co and 0.10-1.0 mass% of Si, with the remainder comprising Cu and unavoidable impurities. The copper alloy has an elongation at break of 5% or above and a work hardening coefficient of 0.0175 or above.

Description

Copper alloy and electronic component

[0001] The present invention relates to a copper alloy and an electronic component including the same.

[0002] In recent years, with the miniaturization of electronic devices, the requirements for materials used in electronic components such as lead frames, terminals, and connectors have been increasing. As materials used for such electronic components, for example, a Cu—Co—Si-based alloy, which is a precipitation hardening type copper alloy, may be used because it has high conductivity, strength, and workability (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2017-179569

[0004] In order to effectively ensure the high strength of a Cu—Co—Si-based copper alloy, it is necessary to increase the degree of rolling in a finishing rolling process performed after an aging treatment process in which intermetallic compounds such as Co—Si-based compounds are precipitated as fine particles in a manufacturing process. However, there is a concern that a high degree of rolling in the finishing rolling process may reduce the elongation of the copper alloy. When the elongation of the copper alloy decreases, for example, during bending forming, necking, which is a phenomenon in which the cross-sectional area of the bent portion locally decreases, is likely to occur. When such necking occurs in a copper alloy, it may lead to a decrease in the yield of electronic components including the same.

[0005] Therefore, an object of the present disclosure is to provide a copper alloy with improved bending formability and an electronic component including the same.

[0006] The copper alloys of this disclosure include the following embodiments: [Embodiment 1] A copper alloy containing 0.50 to 3.0 mass% Co, 0.10 to 1.0 mass% Si, with the remainder being Cu and unavoidable impurities, having a fracture elongation of 5% or more as measured by the method below, and a work hardening coefficient of 0.0175 or more as calculated by the method below. Fracture elongation: A tensile test is performed using a JIS-13B test specimen at a tensile speed of 5 mm / min. Work hardening coefficient: A tensile test is performed in accordance with JIS-Z2253 (2011), and when the initial strain (ε0) is defined as a strain 0.005 less than the nominal strain (ε) at maximum stress, the slope of the logarithmic true stress-logarithmic true strain curve in the range of ε0 to ε is defined as the work hardening coefficient. [Embodiment 2] The copper alloy according to Embodiment 1, wherein the 0.2% yield strength is 500 MPa or more. [Aspect 3] The copper alloy according to Aspect 1 or 2, wherein the conductivity is 30% IACS or higher. [Aspect 4] The copper alloy according to any one of Aspects 1 to 3, wherein the grain size is 10 μm or less. [Aspect 5] The copper alloy according to any one of Aspects 1 to 4, wherein the elongation at break is 10% or less. [Aspect 6] The copper alloy according to Aspect 5, wherein the elongation at break is 5.6% or more and 9.6% or less. [Aspect 7] The copper alloy according to any one of Aspects 1 to 6, wherein the work hardening coefficient is 0.1000 or less. [Aspect 8] The copper alloy according to Aspect 7, wherein the work hardening coefficient is 0.0639 or less. [Aspect 9] The copper alloy according to any one of Aspects 1 to 8, wherein the thickness is 0.020 mm or more and 0.400 mm or less. [Aspect 10] The copper alloy according to any one of aspects 1 to 9, further containing a total of 0.005 to 0.80 mass% of at least one element selected from the group consisting of Mg, Fe, P, Mn, Zn, Ni, and Cr. [Aspect 11] The copper alloy according to any one of aspects 1 to 10, wherein the arithmetic mean roughness Ra is 0.245 μm or less. [Aspect 12] The copper alloy according to aspect 11, wherein the arithmetic mean roughness Ra is 0.200 μm or more.

[0007] The electronic components of this disclosure are electronic components comprising the copper alloy of this disclosure as described above.

[0008] According to this disclosure, it is possible to provide a copper alloy with improved bendability and an electronic component containing the same.

[0009] This figure shows the results of the evaluation of neck formation in the copper alloy plates of Example 5 and Comparative Example 2.

[0010] The following describes copper alloys according to embodiments of this disclosure (hereinafter also referred to as "these embodiments"), but the present invention is not limited to the embodiments described below. In this disclosure, "A to B" means "greater than or equal to A and less than or equal to B". A and B represent numerical values.

[0011] The copper alloy of this embodiment contains 0.50 to 3.0 mass% Co, 0.10 to 1.0 mass% Si, with the remainder being Cu and unavoidable impurities. Furthermore, the copper alloy of this embodiment has a fracture elongation of 5% or more as measured by the following method, and a work hardening coefficient of 0.0175 or more as calculated by the following method. Fracture elongation: A tensile test is performed using a JIS-13B test specimen at a tensile speed of 5 mm / min. Work hardening coefficient: A tensile test is performed in accordance with JIS-Z2253 (2011), and when the initial strain (ε0) is defined as a strain that is 0.005 less than the nominal strain (ε) at the maximum stress, the slope of the logarithmic true stress-logarithmic true strain curve in the range of ε0 to ε is defined as the work hardening coefficient. With the above configuration, the bendability of the copper alloy can be improved.

[0012] As mentioned above, increasing the degree of finishing roll is necessary to ensure the strength of the copper alloy, but this raises concerns about a decrease in elongation. A decrease in the elongation of the copper alloy makes it easier for necking to occur during bending, a phenomenon in which the cross-sectional area of ​​the bent part decreases locally. If such necking occurs in the bent part of a copper alloy that has been bent, it can lead to a decrease in the yield of electronic components containing it. Specifically, when insert molding is performed using a copper alloy that has been bent, a gap may occur between the copper alloy (especially the bent part) and the mold. Resin may leak from this gap (resin overflow), potentially leading to a decrease in yield. As a result of various studies conducted by the inventors to address these issues, they have found that in a Co-Si Corson alloy, increasing the strength during finishing roll and then performing annealing (softening) after finishing roll to restore elongation suppresses necking during bending and improves bendability while maintaining high strength.

[0013] The copper alloy of this embodiment may also have high strength and high conductivity. High strength means, for example, a 0.2% yield strength of 500 MPa or more. High conductivity means, for example, an conductivity of 67% IACS or more.

[0014] <Composition> The copper alloy of this embodiment contains 0.50 to 3.0 mass% of Co and 0.10 to 1.0 mass% of Si. By aging treatment, Co and Si form fine precipitated particles of intermetallic compounds mainly composed of Co2Si, thereby improving the strength of the copper alloy. Furthermore, the conductivity of the copper alloy is improved with the precipitation of Co2Si. If the concentration of Co is less than 0.50 mass%, or if the concentration of Si is less than 0.10 mass%, the desired strength cannot be obtained even if the other component is added in sufficient quantities. Also, if the concentration of Co exceeds 3.0 mass%, or if the concentration of Si exceeds 1.0 mass%, although sufficient strength can be obtained, the conductivity becomes low, and coarse Co-Si particles that do not contribute to the improvement of strength are generated in the matrix, leading to a decrease in bendability. Therefore, the Co content is set to 0.50 to 3.0 mass%, and the Si content to 0.10 to 1.0 mass%.

[0015] In this embodiment, the concentration of Co is preferably 1.0 to 2.5% by mass, and more preferably 1.8 to 2.0% by mass. The concentration of Si is preferably 0.20 to 0.80% by mass, and more preferably 0.38 to 0.47% by mass.

[0016] The copper alloy of this embodiment may further contain, in addition to the elements mentioned above, at least one element selected from the group consisting of Mg, Fe, P, Mn, Zn, Ni, and Cr (hereinafter also referred to as "additive element") in a total amount of 0.005 to 0.80 mass%. This can improve strength, heat resistance, stress relaxation resistance, etc. The total concentration of the additive element can be 0.005 to 0.15 mass%. If the total amount of the additive element is 0.005 mass% or more, the above effects are more likely to occur. If the total amount of the additive element is 0.80 mass% or less, the above effects tend to be obtained without reducing conductivity and bendability.

[0017] The copper alloy of this embodiment may contain at least one element selected from the group consisting of Mg, Fe, P, Mn, Zn, Ni, and Cr in a total amount of 0.20% by mass or less, or 0.10% by mass or less.

[0018] The remainder of the copper alloy in this embodiment (i.e., elements other than those mentioned above) consists of Cu and unavoidable impurities. Unavoidable impurities refer to impurity elements that are inevitably mixed into the material during the manufacturing process, such as S and O. The content of each element included as an unavoidable impurity is not particularly limited, but is, for example, 0.001% by mass or less.

[0019] The composition of copper alloys can be determined by ICP emission spectroscopy (internal standard method). Measurements are performed using an ICP emission spectrometer (ICP-OES, inductively coupled plasma emission spectrometer) such as the Hitachi High-Tech Science SPS3100 or an equivalent instrument. For ICP emission spectroscopy (internal standard method), the copper alloy sample is dissolved in a mixed acid containing hydrochloric acid and nitric acid (hydrochloric acid, nitric acid, and water in a volume ratio of 2:1:2), and the resulting solution is diluted before use. Yttrium (Y) is used as the internal standard element.

[0020] <Elongation at Break> The copper alloy of this embodiment has an elongation at break of 5% or more, as measured by the following method. An elongation at break of 5% or more reduces or suppresses the occurrence of necking and bending wrinkles during bending. An elongation at break of 5.6% or more is preferable. There is no particular upper limit to the elongation at break, but it can be, for example, 10% or less, or 9.6% or less. The elongation at break is calculated by performing a tensile test at a tensile speed of 5 mm / min using a JIS-13B test specimen. More specifically, the elongation at break is calculated by performing a tensile test in accordance with JIS-Z2241 under the following conditions, using the above test specimen, with the tensile direction perpendicular to the rolling direction. The conditions for the tensile test are: specimen width: 12.7 mm, room temperature: 15 to 35°C, tensile speed: 5 mm / min, gauge length: 50 mm.

[0021] <0.2% Yield Strength> The 0.2% yield strength of the copper alloy in this embodiment may be 500 MPa or more, preferably 550 MPa or more. When the 0.2% yield strength is 500 MPa or more, parts obtained from the copper alloy can be more suitably used for various applications, such as electronic components. In particular, when the copper alloy is used as a plug for a connector as an electronic component (for example, a part that slides against other electronic components), it can prevent abrasion when mating with other parts. The upper limit of the 0.2% yield strength of the copper alloy in this embodiment is not particularly limited, but the 0.2% yield strength may be, for example, 800 MPa or less, or 700 MPa or less. The 0.2% yield strength is calculated by performing a tensile test in accordance with JIS-Z2241 using a JIS-13B test piece, with the tensile direction perpendicular to the rolling direction. The conditions for the tensile test are the same as those for the tensile test for elongation at break described above.

[0022] <Conductivity> The conductivity of the copper alloy of this embodiment may be 30% IACS or higher. The conductivity of the copper alloy of this embodiment may be 50% IACS or higher, preferably 67% IACS or higher, and more preferably 69% IACS or higher. When the conductivity is 30% IACS or higher, it can be used more effectively for electronic components. There is no particular upper limit to the conductivity of the copper alloy of this embodiment, but the conductivity may be, for example, 90% IACS or lower, or 80% IACS or lower. The conductivity can be measured by the four-terminal method in accordance with JIS-H0505. A double bridge is used for measurement, and the resistance can be measured based on the average cross-sectional area method. The conductivity can be measured at room temperature (25°C) in a direction parallel to the rolling direction. The gauge length (distance between electrical resistance measurements) is 50 mm.

[0023] <Grain Size> The copper alloy of this embodiment can be manufactured by solution treatment as described later, but the grain size after the final solution treatment is preferably 10 μm or less. A grain size of 10 μm or less can suppress dimensional errors during press working. A grain size of 8.0 μm or less is more preferable. The grain size may also be 2.0 μm or more. The grain size is measured by the following method. First, the rolled parallel cross section of the copper alloy sheet is mirror polished, and then the metal structure is revealed using a solution consisting of ferric chloride (10 g), hydrochloric acid (3 mL, concentration: 35-37%) and distilled water (120 mL). Next, it is calculated by the cutting method in accordance with JIS-H0501.

[0024] <Work Hardening Coefficient (n-value)> In the copper alloy of this embodiment, the work hardening coefficient (hereinafter also referred to as "n-value") calculated by the following method is 0.0175 or higher. When the n-value is 0.0175 or higher, the workability (mainly stretch formability) is good and the bend formability is improved. It is preferable that the n-value is 0.0340 or higher. The n-value may also be 0.1000 or lower, or 0.0639 or lower.

[0025] [Measurement Method] Tensile tests are performed in accordance with JIS-Z2253 (2011). When the initial strain (ε0) is defined as a strain 0.005 less than the nominal strain (ε) at maximum stress, the slope of the logarithmic true stress-logarithmic true strain curve in the range of ε0 to ε is defined as the work hardening coefficient. More specifically, the tensile test is performed in accordance with JIS-Z2241 using copper alloy plates with a thickness of 0.03 mm to 0.1 mm to obtain JIS-13B test specimens, with the tensile direction perpendicular to the rolling direction. The difference between the gauge length L at the time of fracture and the gauge length L0 before the test is determined as a percentage. The conditions for the tensile test to calculate the n-value are the same as the measurement conditions for the fracture elongation described above. The n-value is calculated in the region from when the straight line in the stress-strain curve begins to curve until necking occurs. On the other hand, the elongation at break is calculated including the region from the onset of necking to the point of fracture.

[0026] <Arithmetic Mean Roughness Ra> The copper alloy of this embodiment may have an arithmetic mean roughness Ra (hereinafter also referred to as "Ra") of 0.245 μm or less, as measured by the following method. When the Ra measured by the following measurement method is 0.245 μm or less, the parts obtained from the copper alloy can be more suitably used for various applications, such as electronic components. Ra may also be 0.220 μm or less. Ra may be 0.200 μm or more. The lower limit of Ra is not limited, but for example, Ra may be 0.200 μm or more.

[0027] [Measurement Method] A W-bend test is performed in accordance with JBMA T307:1999, with an inner radius r of 0 mm and a sample width of 10 mm. An AutoCom C-type universal tester (AC-100KN-C) is used as the testing machine. The bending direction is perpendicular to the rolling direction. The test load is 50 kN and the test speed is 5 m / min. A CES M0002-B type mold is used. Ra is measured on the surface of the bent portion of the sample using a laser microscope (Keyence, VK-X) or an equivalent device. The observation magnification is 500x, the measurement point is the center of the plate width, the correction is approximated to the horizontal surface by quadratic surface correction after setting the reference plane to the bending apex, and the measurement range is ±60 μm in the long side direction from the bending apex. Ra is measured in accordance with JIS-B0601:2001 using multiple line roughness levels (number of lines: 10, spacing: 15 μm). The measurement environment temperature is 20-25°C. The main settings for the laser microscope and analysis software are as follows.

[0028] [Measurement Settings] Measurement Mode: Basic setting Scan Mode: Laser confocal Measurement Size: Standard (1024 x 768) Measurement Quality: High precision Measurement Pitch: 0.13 μm RPD: ON Brightness 1: Approximately 6500-7500 (Varies depending on fine focus adjustment) Brightness 2: Auto (9500) Illumination Filter 1: Approximately 10-30% (Varies depending on fine focus adjustment) Illumination Filter 2: Auto (Approximately 10-30% (Varies depending on fine focus adjustment)) Double Scan: OFF Averaging Count: 1 Do not acquire color image: OFF Fine Mode: ON Enable processing of noise areas: OFF [Illumination] Coaxial Incident Light: 100 Ring Illumination: OFF [Z-axis] Z-axis Mode: Recommended setting Upper Measurement Limit: Approximately 9900-10100 μm (Varies depending on fine focus adjustment) Lower Measurement Limit: Approximately 10000-10100 μm (Varies depending on fine focus adjustment) Fixed Z measurement distance: ON Z measurement distance: Approximately 20 μm (varies with fine focus adjustment) Automatic upper and lower limits / automatic brightness: OFF [Head] Head: R Objective lens name: Plan (CF IC EPI Plan 50X) Objective lens magnification: 50X Lens NA: 0.800 WD: 0.54 mm Field curvature correction: ON Light intensity eccentricity correction: ON Ring illumination correction: ON XY calibration: 268.846 nm / pixel Z calibration: 1.000 (0.100 nm / digit) [Camera settings] Brightness mode: Auto Brightness (auto): Approximately 27 (varies with fine focus adjustment) Brightness (manual): 1 Edge enhancement: 5 [Laser settings] γ coefficient (γ correction value): 0.45 γ offset: 0% Black and white inversion: OFF Edge enhancement type: None Edge enhancement direction: Vertical Edge enhancement strength: Weak [Other conditions shown in the worksheet] Measurement mode: Surface shape Optical zoom magnification: 1.0x Filter: OFF Camera gain: 0dB Shutter speed: Auto White balance mode: Manual White balance R: 0 White balance B: 0 Light received light amount correction mode: Gamma correction Head type: VK-X105 Vividness: 5 Contrast: 5 Brightness: 0 AI noise reduction: OFF Slope noise filter: OFF [Analysis conditions] Image processing: Surface shape correction performed (cutoff wavelength 0.08 mm)Surface Roughness Settings (Filter Settings) Filter Type: Gaussian S-Filter (Low-Pass Filter): None F-Operation (Shape Correction): None L-Filter (High-Pass Filter): None End Effect Correction: ON

[0029] <Shape> The shape of the copper alloy in this embodiment is not particularly limited as long as it is an object having a three-dimensional shape with a certain thickness, but it may be in the form of a plate. That is, the copper alloy in this embodiment may be a copper alloy plate.

[0030] In this disclosure, "plate" means a shape having a certain thickness and a substantially rectangular cross-section, and may also have a curved surface. Furthermore, "plate" may also mean a flat shape having substantially uniform thickness and a substantially rectangular cross-section. A plate with a thin thickness (e.g., less than 0.1 mm) may be referred to as "foil."

[0031] The thickness of the copper alloy in this embodiment is, for example, 0.020 mm or more and 0.400 mm or less. The lower limit of the thickness of the copper alloy may be, for example, 0.030 mm or more and 0.059 mm or more. The upper limit of the thickness of the copper alloy may be, for example, 0.100 mm or less and 0.079 mm or less.

[0032] In this disclosure, "plate thickness" may also be referred to as "plate thickness." The plate thickness of copper alloys is measured using a micrometer in accordance with JIS-B7502. A BMS-25MX manufactured by Mitutoyo Corporation or an equivalent device is used as the micrometer.

[0033] <Method for Manufacturing Copper Alloy> The copper alloy of this embodiment can be manufactured by the following method. Typically, after hot rolling an ingot, the resulting intermediate is repeatedly annealed and rolled to adjust it to the desired plate thickness. Then, the intermediate with the adjusted plate thickness is subjected to solution treatment, aging treatment, finish rolling, and stress-relieving annealing in this order. The copper alloy of this embodiment can be manufactured by the above method.

[0034] Between each of the above steps, grinding, polishing, shot blasting, pickling, etc., can be performed as appropriate to remove oxide scale from the surface of the intermediate. Annealing may also be added between each of the above steps as needed.

[0035] In the solution treatment, a silicide such as a Co-Si compound is dissolved in the intermediate Cu matrix, while simultaneously recrystallizing the Cu matrix. The solution treatment can be carried out under general conditions. The conditions for the solution treatment are not particularly limited, but for example, the material temperature is 900°C or higher and the time is 1 second to 10 minutes.

[0036] In the aging treatment, the silicide dissolved in the intermediate Cu matrix during the solution treatment is precipitated as fine particles of an intermetallic compound mainly composed of Co2Si. This increases the strength and conductivity. The conditions for the aging treatment are not particularly limited, but for example, they can be 375 to 625°C and 0.5 to 50 hours, or 400 to 550°C.

[0037] Finish rolling is a process that increases strength by generating Orowan loops around the fine particles precipitated in the intermediate Cu matrix. The degree of rolling (%) is determined by the thickness of the intermediate before rolling. 0、 When T1 is the thickness of the intermediate after rolling, it is calculated as (T0 - T1) / T0 × 100. The degree of processing in finish rolling is, for example, 10 to 50%. Lowering the degree of processing in finish rolling can suppress the decrease in the n value. Increasing the degree of processing in finish rolling can improve the yield strength by 0.2%. Also, increasing the degree of processing in finish rolling tends to decrease the conductivity. The degree of processing can also be 10 to 40%.

[0038] Stress relief annealing can be carried out continuously, for example, by passing a copper strip as an intermediate through a furnace at a line speed of 10 m / min or more. The temperature for stress relief annealing is, for example, 400 to 600°C. The duration for stress relief annealing is, for example, 3 to 30 seconds.

[0039] The conditions for stress relief annealing need to be adjusted according to the degree of processing in the finish rolling. For example, if the degree of processing in the finish rolling is high, it is necessary to adjust by increasing the processing temperature or increasing the processing time. Increasing the processing temperature or increasing the processing time in stress relief annealing can increase the n-value and the elongation at break. Also, adjusting either or both of the processing temperature and processing time in stress relief annealing tends to increase conductivity but decrease the 0.2% yield strength.

[0040] <Electronic Components> The electronic components of this embodiment include the copper alloy of this embodiment. More specifically, the electronic components of this embodiment have a copper alloy component obtained by processing the copper alloy of this embodiment inside the electronic component.

[0041] With the above configuration, the copper alloy of this embodiment has excellent bendability, so in this embodiment, it is possible to manufacture electronic components with improved yield by suppressing the occurrence of, for example, necking. Furthermore, in addition to its excellent bendability, the copper alloy of this embodiment may have high strength and high conductivity, so in this embodiment, electronic components can be miniaturized and space saved. Examples of electronic components include terminals and connectors. Terminals are, for example, power terminals. Connectors are, for example, board-to-board connectors. Such electronic components such as terminals and connectors can be manufactured by a manufacturing method that includes the steps of bending a copper alloy, placing the copper alloy component in a mold, and insert molding it with a predetermined resin composition.

[0042] Although embodiments of the present disclosure have been described above, the copper alloys and electronic components of the present disclosure are not limited to the examples described above and can be modified as appropriate.

[0043] The copper alloys of each example and each comparative example were produced as follows. In Example 1, electrolytic copper was used as a raw material, and a copper alloy having the composition shown in Table 1 was melted using an air melting furnace and cast into an ingot. Hot rolling was performed on this ingot. After hot rolling, heat treatment and rolling for the purpose of softening the intermediate were repeated, and after solution treatment, aging treatment, and finish rolling, stress relief annealing was performed under the conditions shown in Table 1. In finish rolling, Examples 1 and 2 were finish rolled in the range of 10 to 50%. Here, Example 1 had a higher degree of working than Example 2. In Examples 5 to 7 and Comparative Example 2, the degree of working in finish rolling was the same as that in Example 1. In Examples 3 to 4 and Comparative Example 1, the degree of working in finish rolling was the same as that in Example 2. Also, the copper alloys of Examples 2 to 7 and Comparative Examples 1 and 2 were produced by the same method as the production method of the copper alloy of Example 1, except for the degree of working in finish rolling and the conditions of stress relief annealing. As described above, copper alloy plates of the examples and comparative examples having the plate thickness shown in Table 1 were obtained.

[0044]

[0045] For each physical property of the obtained copper alloys of Example 1 and Comparative Example 1 and their intermediates, the following method was used for measurement. The measurement results are shown in Table 1. <Plate Thickness> The plate thickness of the copper alloy was measured using a BMS-25MX manufactured by Mitutoyo Corporation.

[0046] <Composition> The composition of the obtained copper alloy was confirmed by ICP emission spectrometry (internal standard method). As an ICP emission spectrometry apparatus, an SPS3100 (34HV) manufactured by Hitachi High-Technologies Corporation was used. A sample of the copper alloy dissolved in a mixed acid containing hydrochloric acid and nitric acid (hydrochloric acid, nitric acid, and water in a volume ratio of 2:1:2) was diluted and used as a measurement sample. Y (yttrium) was used as an internal standard element.

[0047] In the copper alloys of the examples and comparative examples, Mg, Fe, P, Mn, Zn, Ni, and Cr were contained in a total amount of 0.15 mass% or less.

[0048] <Elongation at Break, 0.2% Yield Strength> Elongation at break and 0.2% yield strength were calculated by using JIS-13B test specimens obtained from each copper alloy sheet, with the tensile direction perpendicular to the rolling direction, and measurements were performed in accordance with JIS-Z2241. The tensile test conditions were: specimen width: 12.7 mm, room temperature: 15-35°C, tensile speed: 5 mm / min, gauge length: 50 mm.

[0049] <Work Hardening Coefficient (n-value)> To determine the n-value, JIS-13B test specimens were obtained using each copper alloy plate, and then tensile tests were performed in accordance with JIS-Z2241, with the tensile direction perpendicular to the rolling direction. The tensile test conditions were: specimen width: 12.7 mm, room temperature: 15-35°C, tensile speed: 5 mm / min, gauge length: 50 mm. The difference between the gauge length L at the time of fracture and the gauge length L0 before the test was calculated as a percentage.

[0050] When the initial strain (ε0) was defined as a strain 0.005 less than the nominal strain (ε) at maximum stress, the slope of the logarithmic true stress-logarithmic true strain curve in the range of ε0 to ε was defined as the work hardening coefficient.

[0051] <Grain Size> The grain size was measured by the following method. First, the rolled parallel cross-section of each copper alloy sheet was mirror-polished, and then the metallic structure was revealed using a solution consisting of ferric chloride (10 g), hydrochloric acid (3 mL, concentration: 35-37%), and distilled water (120 mL). Next, it was calculated by the cutting method in accordance with JIS-H0501. The measurement was performed under the conditions described above. The grain size of the copper alloys in Examples 1-7 and Comparative Examples 1-2 was 5.5 μm in all cases.

[0052] <Conductivity> Conductivity was measured using the four-terminal method in accordance with JIS-H0505. A double bridge was used for measurement, and resistance was measured based on the average cross-sectional area method. Conductivity was measured at room temperature (25°C) in a direction parallel to the rolling direction. The gauge length (distance between electrical resistance measurements) was set to 50 mm.

[0053] <Arithmetic Mean Roughness Ra> By measuring the arithmetic mean roughness (hereinafter also referred to as "Ra") after the bending test, the ease of forming bend wrinkles and, consequently, necks, and the bend formability can be evaluated. Specifically, Ra measurement was performed using a W bending test in accordance with JBMA T307:1999, with an inner radius r of 0 mm and a sample width of 10 mm. An AutoCom C-type universal testing machine (AC-100KN-C) was used as the testing machine. The bending direction was perpendicular to the rolling direction. The test load was 50 kN and the test speed was 5 m / min. A CES M0002-B type mold was used.

[0054] Ra was measured on the bent surface of the sample using a laser microscope (Keyence, VK-X). The observation magnification was 500x, the measurement point was the center of the plate width, the correction was approximated to the horizontal surface by quadratic surface correction after setting the reference plane to the bend apex, and the measurement range was ±60 μm in the direction of the long side from the bend apex. Ra was measured in accordance with JIS-B0601:2001 using multiple line roughness values ​​(number of lines: 10, spacing: 15 μm). The measurement ambient temperature was 20 to 25°C. The main settings conditions for the laser microscope and analysis software were as follows.

[0055] [Measurement Settings] Measurement Mode: Basic setting Scan Mode: Laser confocal Measurement Size: Standard (1024 x 768) Measurement Quality: High precision Measurement Pitch: 0.13 μm RPD: ON Brightness 1: Approximately 6500-7500 (Varies depending on fine focus adjustment) Brightness 2: Auto (9500) Illumination Filter 1: Approximately 10-30% (Varies depending on fine focus adjustment) Illumination Filter 2: Auto (Approximately 10-30% (Varies depending on fine focus adjustment)) Double Scan: OFF Averaging Count: 1 Do not acquire color image: OFF Fine Mode: ON Enable processing of noise areas: OFF [Illumination] Coaxial Incident Light: 100 Ring Illumination: OFF [Z-axis] Z-axis Mode: Recommended setting Upper Measurement Limit: Approximately 9900-10100 μm (Varies depending on fine focus adjustment) Lower Measurement Limit: Approximately 10000-10100 μm (Varies depending on fine focus adjustment) Fixed Z measurement distance: ON Z measurement distance: Approximately 20 μm (varies with fine focus adjustment) Automatic upper and lower limits / automatic brightness: OFF [Head] Head: R Objective lens name: Plan (CF IC EPI Plan 50X) Objective lens magnification: 50X Lens NA: 0.800 WD: 0.54 mm Field curvature correction: ON Light intensity eccentricity correction: ON Ring illumination correction: ON XY calibration: 268.846 nm / pixel Z calibration: 1.000 (0.100 nm / digit) [Camera settings] Brightness mode: Auto Brightness (auto): Approximately 27 (varies with fine focus adjustment) Brightness (manual): 1 Edge enhancement: 5 [Laser settings] γ coefficient (γ correction value): 0.45 γ offset: 0% Black and white inversion: OFF Edge enhancement type: None Edge enhancement direction: Vertical Edge enhancement strength: Weak [Other conditions shown in the worksheet] Measurement mode: Surface shape Optical zoom magnification: 1.0x Filter: OFF Camera gain: 0dB Shutter speed: Auto White balance mode: Manual White balance R: 0 White balance B: 0 Light received light amount correction mode: Gamma correction Head type: VK-X105 Vividness: 5 Contrast: 5 Brightness: 0 AI noise reduction: OFF Slope noise filter: OFF [Analysis conditions] Image processing: Surface shape correction performed (cutoff wavelength 0.08 mm)Surface Roughness Settings (Filter Settings) Filter Type: Gaussian S-Filter (Low-Pass Filter): None F-Operation (Shape Correction): None L-Filter (High-Pass Filter): None End Effect Correction: ON

[0056] <Evaluation of Narrowing Occurrence> Using the test pieces of Example 5 and Comparative Example 2 after the measurement of the "arithmetic mean roughness Ra" described above, we evaluated whether necking occurred due to bending (Figure 1). Specifically, the cross section parallel to the rolling direction of the bent test piece (side surface of the test piece) was observed at 500x magnification using a digital microscope (Keyence, VHX-6000) and photographs were taken. Using the photographs taken, we checked whether the outline of the outer part of the bent portion of the test piece was arc-shaped, and it was determined that necking had occurred if the outline of the test piece was significantly indented towards the center of the arc relative to the arc.

[0057] As is clear from Table 1, in each example where stress relief annealing was performed after finish rolling, the elongation at break was 5% or more, and the n value was 0.0175 or more. On the other hand, in Comparative Examples 1 and 2, where stress relief annealing was not performed after finish rolling, the elongation at break was less than 5%, and the n value was less than 0.0175. The copper alloys of the examples with these characteristics had lower Ra values ​​than the copper alloys of the comparative examples, and the bent surface (the surface of the bent part of the sample) was smoother. In addition, in the evaluation of necking occurrence, no necking was observed in the copper alloy of Example 5, but necking was observed in the copper alloy of Comparative Example 2. In other words, the copper alloys of the examples can be said to have good bend formability. Furthermore, the copper alloys of each example had a 0.2% yield strength of 500 MPa or more and an electrical conductivity of 67% IACS or more. Therefore, the copper alloys of each example had good bend formability while maintaining high strength and high electrical conductivity.

[0058] According to this disclosure, it is possible to provide a copper alloy with improved bendability and an electronic component containing the same.

Claims

1. A copper alloy containing 0.50 to 3.0 mass% Co, 0.10 to 1.0 mass% Si, with the remainder being Cu and unavoidable impurities, having a fracture elongation of 5% or more as measured by the method described below, and a work hardening coefficient of 0.0175 or more as calculated by the method described below. Rupture Elongation: Tensile tests are performed using JIS-13B specimens at a tensile speed of 5 mm / min. Work hardening coefficient: Tensile tests are performed in accordance with JIS-Z2253 (2011), and the initial strain (ε0) is defined as a strain that is 0.005 less than the nominal strain (ε) at the maximum stress. The slope of the logarithmic true stress-logarithmic true strain curve in the range of ε0 to ε is defined as the work hardening coefficient.

2. The copper alloy according to claim 1, wherein the 0.2% yield strength is 500 MPa or more.

3. The copper alloy according to claim 1 or 2, wherein the conductivity is 30% IACS or higher.

4. The copper alloy according to claim 1 or 2, wherein the crystal grain size is 10 μm or less.

5. The copper alloy according to claim 1 or 2, wherein the elongation at break is 10% or less.

6. The copper alloy according to claim 5, wherein the elongation at break is 5.6% or more and 9.6% or less.

7. The copper alloy according to claim 1 or 2, wherein the work hardening coefficient is 0.1000 or less.

8. The copper alloy according to claim 7, wherein the work hardening coefficient is 0.0639 or less.

9. The copper alloy according to claim 1 or 2, wherein the thickness is 0.020 mm or more and 0.400 mm or less.

10. The copper alloy according to claim 1 or 2, further containing a total of 0.005 to 0.80 mass% of at least one element selected from the group consisting of Mg, Fe, P, Mn, Zn, Ni, and Cr.

11. The copper alloy according to claim 1 or 2, wherein the arithmetic mean roughness Ra is 0.245 μm or less.

12. The copper alloy according to claim 11, wherein the arithmetic mean roughness Ra is 0.200 μm or more.

13. An electronic component comprising the copper alloy described in claim 1 or 2.

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