Copper alloys and electronic components

Abstract

To provide a copper alloy with improved bendability. [Solution] The copper alloy of this disclosure contains 0.50 to 3.0 mass% of Co and 0.10 to 1.0 mass% of Si, with the remainder being Cu and unavoidable impurities, having a fracture elongation of 5% or more and a work hardening coefficient of 0.0175 or more.

Description

Technical Field

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

Background Art

[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 become more sophisticated. As materials used for such electronic components, a Cu-Co-Si 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).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

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

Means for Solving the Problems

[0006] The copper alloys of this disclosure include the following embodiments: [Aspect 1] It contains 0.50-3.0% by mass of Co, 0.10-1.0% by mass of Si, with the remainder being Cu and unavoidable impurities. The elongation at break measured by the following method is 5% or more. A copper alloy having a work hardening coefficient of 0.0175 or higher, calculated using the method described below. Elongation at break: A tensile test is performed using a JIS-13B test specimen at a tensile speed of 5 mm / min. Work hardening coefficient: Tensile tests are performed in accordance with JIS-Z2253 (2011). 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. [Aspect 2] The copper alloy according to embodiment 1, wherein the 0.2% yield strength is 500 MPa or more. [Aspect 3] A copper alloy according to embodiment 1 or 2, wherein the conductivity is 30% IACS or higher. [Aspect 4] A copper alloy according to any one of embodiments 1 to 3, wherein the crystal grain size is 10 μm or less. [Aspect 5] The copper alloy according to any one of embodiments 1 to 4, wherein the elongation at break is 10% or less. [Aspect 6] The copper alloy according to embodiment 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 embodiments 1 to 6, wherein the work hardening coefficient is 0.1000 or less. [Aspect 8] The copper alloy according to embodiment 7, wherein the work hardening coefficient is 0.0639 or less. [Aspect 9] A copper alloy according to any one of embodiments 1 to 8, wherein the thickness is 0.020 mm or more and 0.400 mm or less. [Aspect 10] A copper alloy according to any one of embodiments 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] A copper alloy according to any one of embodiments 1 to 10, wherein the arithmetic mean roughness Ra is 0.245 μm or less. [Aspect 12] The copper alloy according to embodiment 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. [Effects of the Invention]

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

[0009] [Figure 1] This figure shows the results of the evaluation of necking occurrence in the copper alloy plates of Example 5 and Comparative Example 2. [Modes for carrying out the invention]

[0010] The following describes copper alloys according to embodiments of the present 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, and the remainder consists of Cu and unavoidable impurities. Furthermore, the copper alloy of this embodiment has 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. Elongation at break: 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 conducted in accordance with JIS-Z2253 (2011). When the initial strain (ε0) is set to 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. According to the above configuration, the bending formability of the copper alloy can be improved.

[0012] As described above, in order to ensure the strength of the copper alloy, it is necessary to increase the degree of finish rolling. However, there is a concern that the elongation will decrease. When the elongation of the copper alloy decreases, necking, which is a phenomenon where the cross-sectional area of the bent part locally decreases during bending, is likely to occur. When such necking occurs in the bent part of the copper alloy after bending, it may lead to a decrease in the yield of electronic components including the same. Specifically, when insert molding is performed using the copper alloy after bending, a gap may occur between the copper alloy (especially the bent part) and the mold. Resin may leak from the gap (resin covering), leading to a decrease in the yield. As a result of various studies by the inventors to address such problems, in the Co - Si - based Colson alloy, by increasing the strength through finish rolling and annealing (softening) for the purpose of restoring elongation after finish rolling, it has been found that necking during bending can be suppressed and the bending formability can be improved while maintaining high strength.

[0013] The copper alloy of this embodiment can also have high strength and high conductivity. High strength means, for example, that the 0.2% proof stress is 500 MPa or more. High conductivity means, for example, that the conductivity is 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 performing aging treatment on Co and Si, Co and Si form fine precipitated particles of an intermetallic compound mainly composed of Co2Si, improving the strength of the copper alloy. Also, with the precipitation of Co2Si, the conductivity of the copper alloy is improved. If the Co concentration is less than 0.50 mass%, or the Si concentration is less than 0.10 mass%, the desired strength cannot be obtained even if the other component is added in sufficient quantities. Furthermore, if the Co concentration exceeds 3.0 mass%, or the Si concentration exceeds 1.0 mass%, although sufficient strength can be obtained, the conductivity will be low, and coarse Co-Si particles that do not contribute to strength improvement will be formed in the matrix, leading to a decrease in bendability. Therefore, the Co content should be set to 0.50-3.0 mass%, and the Si content to 0.10-1.0 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 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%. The above effects are more likely to occur if the total amount of additive elements is 0.005% by mass or more. If the total amount of additive elements is 0.80% by mass or less, the above effects tend to be obtainable 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 introduced into the material during the manufacturing process, such as sulfur (S) and oxygen (O). The content of each element included as an unavoidable impurity is not particularly limited, but for example, it is 0.001% by mass or less.

[0019] The composition of copper alloys can be determined by ICP emission spectrometry (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 spectrometry (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 a fracture elongation of 5% or more, as measured by the following method. A fracture elongation of 5% or more reduces or suppresses the occurrence of necking and bending wrinkles during bending. A fracture elongation of 5.6% or more is preferable. The upper limit of the fracture elongation is not particularly limited, but can be, for example, 10% or less, or 9.6% or less. The elongation at break is calculated by performing a tensile test using a JIS-13B test specimen at a tensile speed of 5 mm / min. More specifically, the elongation at break is calculated by performing a tensile test using the above test specimen, with the tensile direction perpendicular to the rolling direction, under the following conditions in accordance with JIS-Z2241. The conditions for the tensile test are as follows: specimen width: 12.7 mm, room temperature: 15-35°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 higher, and preferably 550 MPa or higher. When the 0.2% yield strength is 500 MPa or higher, the 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 is possible to prevent abrasion when mating with other parts. The upper limit of the 0.2% proof stress of the copper alloy in this embodiment is not particularly limited, but the 0.2% proof stress 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 specimen, 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 in this embodiment may be 30% IACS or higher. The conductivity of the copper alloy in this embodiment may be 50% IACS or higher, preferably 67% IACS or higher, and more preferably 69% IACS or higher. A conductivity of 30% IACS or higher allows for more effective use in electronic components. The upper limit of the conductivity of the copper alloy in this embodiment is not particularly limited, but the conductivity may be, for example, 90% IACS or less, or 80% IACS or less. Conductivity can be measured using the four-terminal method in accordance with JIS-H0505. A double bridge is used for measurement, and resistance can be measured based on the average cross-sectional area method. 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] <Crystal grain size> The copper alloy of this embodiment can be manufactured through 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 helps to suppress dimensional errors during press working. A grain size of 8.0 μm or less is more preferable. A grain size of 2.0 μm or more is also acceptable. 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, the grain size 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 the "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 conducted 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 thicknesses 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 fracture and the gauge length L0 before the test is calculated as a percentage. The conditions for the tensile test used to calculate the n-value are the same as those for measuring the elongation at break 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 when necking occurs until fracture occurs.

[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 also be 0.200 μm or more. The lower limit of Ra is not limited, but for example, Ra may be 0.200 μm or greater.

[0027] [Measurement method] A W-bend test will be performed in accordance with JBMA T307:1999, with an inner radius r of 0 mm and a sample width of 10 mm. An AutoCom Type C universal testing machine (AC-100KN-C) will be used as the testing machine. The bending direction will be perpendicular to the rolling direction. The test load will be 50 kN and the test speed will be 5 m / min. A CES M0002-B type mold will be used. Ra is measured on the bent surface 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 bend apex, and the measurement range is ±60 μm in the long side direction from the bend apex. Ra is measured in accordance with JIS-B0601:2001 using multiple line roughness values ​​(number of lines: 10, spacing: 15 μm). The measurement environment temperature is 20~25°C. The main settings conditions for the laser microscope and analysis software are as follows.

[0028] [Measurement settings] Measurement mode: Basic settings 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) Lighting filter 1: Approximately 10-30% (varies depending on fine focus adjustment) Lighting filter 2: Automatic (approximately 10-30% (varies depending on focus fine-tuning)) Double scan: OFF Average number of times: 1 Do not retrieve color images: OFF Fine Mode: ON Enable noise processing: OFF 〔illumination〕 Coaxial epi-ray: 100 Ring light: OFF [Z-axis] Z-axis mode: Recommended setting Measurement limit: Approximately 9900-10100 μm (may vary depending on fine focus adjustment) Measurement lower limit: Approximately 10,000 to 10,100 μm (varies depending on fine focus adjustment) Fixed Z measurement distance: ON Z measurement distance: Approximately 20 μm (may vary depending on fine focus adjustment) Automatic upper / lower limits and automatic brightness: OFF 〔head〕 Head: R Objective lens name: Plan (CF IC EPI Plan 50X) Objective lens magnification: 50X Lens NA: 0.800 WD: 0.54mm Image field curvature correction: ON Light intensity eccentricity correction: ON Ring lighting correction: ON XY calibration: 268.846nm / pixel Z calibration: 1.000 (0.100 nm / digit) [Camera settings] Brightness mode: Auto Brightness (Auto): Approximately 27 (may vary depending on focus fine-tuning) Brightness (Manual): 1 Edge enhancement: 5 [Laser settings] γ coefficient (γ correction value): 0.45 γ offset: 0% Invert Black and White: OFF Edge enhancement type: None Edge enhancement direction: Vertical Edge emphasis 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 reception intensity correction mode: γ correction Head type: VK-X105 Vibrancy: 5 Contrast: 5 Brightness: 0 AI noise removal: OFF Slope noise filter: OFF [Analysis conditions] Image processing: Surface shape correction performed (cutoff wavelength 0.08 mm) Surface roughness setting (filter setting) 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 also be in the form of a plate. In other words, 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. As the micrometer, a BMS-25MX manufactured by Mitutoyo Corporation or an equivalent device is used.

[0033] <Method for manufacturing copper alloys> The copper alloy of this embodiment can be manufactured by the following method. In this embodiment, the copper alloy is typically produced by hot-rolling an ingot, then repeatedly annealing and rolling the resulting intermediate to adjust it to the desired plate thickness. Subsequently, the intermediate with the adjusted plate thickness is subjected to solution treatment, aging treatment, finish rolling, and stress-relieving annealing in that order. Through this process, the copper alloy of this embodiment can be manufactured.

[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 solution treatment, silicides such as Co-Si compounds are dissolved in the intermediate Cu matrix, while simultaneously recrystallizing the Cu matrix. Solution treatment can be carried out under general conditions. The conditions for 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, 10-50%. 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 10-40%.

[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 component of this embodiment includes the copper alloy of this embodiment. More specifically, the electronic component of this embodiment has 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 include, for example, power terminals. Connectors include, for example, board-to-board connectors. Such electronic components, such as terminals and connectors, can be manufactured, for example, 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. [Examples]

[0043] The copper alloys for each example and each comparative example were prepared as follows. In Example 1, electrolytic copper was used as the raw material, and a copper alloy with the composition shown in Table 1 was melted using an atmospheric melting furnace and cast into an ingot. This ingot was then hot-rolled. After hot rolling, heat treatment and rolling were repeated to soften the intermediate, followed by solution treatment, aging treatment, and finish rolling, and then stress-relieving annealing was performed under the conditions in Table 1. In the finish rolling, Examples 1 and 2 were finished to a range of 10-50%. Here, Example 1 had a higher degree of processing than Example 2. Examples 5-7 and Comparative Example 2 had the same degree of processing as Example 1 for finish rolling. Examples 3-4 and Comparative Example 1 had the same degree of processing as Example 2 for finish rolling. Furthermore, the copper alloys of Examples 2-7 and Comparative Examples 1 and 2 were manufactured using the same method as the copper alloy of Example 1, except for the degree of processing in finish rolling and the conditions for stress-relieving annealing. Based on the above, copper alloy plates of the examples and comparative examples having the plate thicknesses shown in Table 1 were obtained.

[0044] [Table 1]

[0045] The physical properties of the copper alloys and intermediates obtained in Example 1 and Comparative Example 1 were measured by the following method. The measurement results are shown in Table 1. <plate thickness> The thickness of the copper alloy sheet 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). A Hitachi High-Tech Science SPS3100 (34HV) ICP emission spectrometer was used. The copper alloy sample was 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 diluted sample was used for measurement. Yttrium (Y) was used as the internal standard element.

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

[0048] <Elongation at break, 0.2% proof stress> The elongation at break and 0.2% proof stress were calculated by using JIS-13B test specimens obtained from each copper alloy sheet, with the tensile direction perpendicular to the rolling direction, and by measuring in accordance with JIS-Z2241. The tensile test conditions were as follows: 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)> The n-value was determined by obtaining JIS-13B test specimens from each copper alloy plate, and then conducting tensile tests 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 ε0 to ε was defined as the work hardening coefficient.

[0051] <Crystal 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 metall 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, the grain size was calculated by the cutting method in accordance with JIS-H0501. The measurements were taken 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 a bending test, the likelihood of bending wrinkles and subsequent necking, as well as the bendability, 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 (number of lines: 10, spacing: 15 μm). The measurement ambient temperature was 20~25°C. The main settings conditions for the laser microscope and analysis software were as follows.

[0055] [Measurement settings] Measurement mode: Basic settings 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) Lighting filter 1: Approximately 10-30% (varies depending on fine focus adjustment) Lighting filter 2: Automatic (approximately 10-30% (varies depending on focus fine-tuning)) Double scan: OFF Average number of times: 1 Do not retrieve color images: OFF Fine Mode: ON Enable noise processing: OFF 〔illumination〕 Coaxial epi-ray: 100 Ring light: OFF [Z-axis] Z-axis mode: Recommended setting Measurement limit: Approximately 9900-10100 μm (may vary depending on fine focus adjustment) Measurement lower limit: Approximately 10,000 to 10,100 μm (varies depending on fine focus adjustment) Fixed Z measurement distance: ON Z measurement distance: Approximately 20 μm (may vary depending on fine focus adjustment) Automatic upper / lower limits and automatic brightness: OFF 〔head〕 Head: R Objective lens name: Plan (CF IC EPI Plan 50X) Objective lens magnification: 50X Lens NA: 0.800 WD: 0.54mm Image field curvature correction: ON Light intensity eccentricity correction: ON Ring lighting correction: ON XY calibration: 268.846nm / pixel Z calibration: 1.000 (0.100 nm / digit) [Camera settings] Brightness mode: Auto Brightness (Auto): Approximately 27 (may vary depending on focus fine-tuning) Brightness (Manual): 1 Edge enhancement: 5 [Laser settings] γ coefficient (γ correction value): 0.45 γ offset: 0% Invert Black and White: OFF Edge enhancement type: None Edge enhancement direction: Vertical Edge emphasis 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 reception intensity correction mode: γ correction Head type: VK-X105 Vibrancy: 5 Contrast: 5 Brightness: 0 AI noise removal: OFF Slope noise filter: OFF [Analysis conditions] Image processing: Surface shape correction performed (cutoff wavelength 0.08 mm) Surface roughness setting (filter setting) 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 waistline formation> Using the specimens from 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 specimen (side surface of the specimen) was observed at 500x magnification using a digital microscope (Keyence, VHX-6000) and photographs were taken. Using the photographs, we checked whether the outline of the outer part of the bent portion of the specimen was arc-shaped, and we determined that necking had occurred if the outline of the specimen 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-relieving 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-relieving 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. Furthermore, 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 in each example had a 0.2% yield strength of 500 MPa or higher and an electrical conductivity of 67% IACS or higher. Therefore, the copper alloys in each embodiment exhibited good bendability while maintaining high strength and high conductivity. [Industrial applicability]

[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. It contains 0.50 to 3.0 mass% Co, 0.10 to 1.0 mass% Si, and the remainder consists of Cu and unavoidable impurities. The elongation at break measured by the following method is 5% or more. A copper alloy having a work hardening coefficient of 0.0175 or higher, calculated using the method described below. Elongation at break: A tensile test is performed using a JIS-13B test specimen at a tensile speed of 5 mm / min. Work hardening coefficient: Tensile tests are performed in accordance with JIS-Z2253 (2011). When the initial strain (ε0) is set to 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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