Copper alloy sheet, energizing component, heat radiation component, and inter-substrate connector

Abstract

To provide a copper alloy sheet having excellent hardness which is equipped with properties that a deviation of the actual profile is suppressed small for the profile of an ideal smooth curved surface of an outer peripheral surface of a bending processing part when severe bending processing is applied.SOLUTION: A copper alloy sheet has a chemical composition that contains Ni:0.1 to 5.0%, Sn:0.1 to 5.0%, P:0.01 to 0.5% in mass%, may contain a predetermined arbitrary element, and has the balance of Cu and inevitable impurities, where, in measurement by a step size 0.1 μm by EBSD, an average crystal grain diameter by Area Fraction method where a boundary having the crystal orientation difference of 5° or more is regarded as a crystal grain boundary is 1 to 4 μm, and GROD average value is 1 to 5°.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a copper alloy sheet material, a current-carrying component, a heat-dissipating component, and a board-to-board connector. [Background technology]

[0002] Advances in electronics have led to increasingly complex and highly integrated electrical wiring in various machines, necessitating the need for smaller, lighter, more reliable, and less expensive electrical and electronic components such as connectors. Furthermore, copper alloy materials used in electrical and electronic components such as connectors must be thin-walled and pressed into complex shapes, so they must have good strength, elasticity, conductivity, heat dissipation, and press formability. Cu-Ni-Sn-P-based copper alloys, which offer excellent tensile strength, conductivity, heat dissipation, stress relaxation resistance, and bending workability, are used as copper alloy materials with these properties.

[0003] In recent years, there has been an increasing demand for thinner, narrower widths, and narrower pitches in connectors and heat dissipation components, making it more important than ever for copper alloy sheets, which are the raw materials, to have both strength and bendability. Various studies have been conducted to date on methods for improving the strength and bendability of Cu-Ni-Sn-P based copper alloys (for example, Patent Documents 1 to 3).

[0004] Patent Document 1 discloses a Cu-Ni-Sn-P-based copper alloy sheet in which the structure of the copper alloy sheet is formed into a texture in which the orientation distribution density of the B orientation and the sum of the orientation distribution densities of the B orientation, S orientation, and Cu orientation are within a specific range, and which satisfies the required properties of terminals and connectors, such as stress relaxation resistance and bending workability. Patent Document 1 also discloses a manufacturing process for producing such a copper alloy sheet, which includes casting, hot rolling, cold rolling, finish annealing (in the example, at 600°C for 60 seconds), cold rolling, and stress relief annealing.

[0005] Patent Document 2 discloses a copper-based alloy strip for terminals, which is a Cu-Ni-Sn-P-based copper alloy having a tensile strength of 550 MPa or more, a spring limit value of 450 MPa or more, an electrical conductivity of 40% IACS or more, a minimum bending radius ratio of 1 or less, and a stress relaxation rate of 10% or less. To produce such a copper alloy strip, a manufacturing process is disclosed in which hot rolling is omitted and continuous casting, homogenization annealing, cold rolling, intermediate annealing (in the example, the strip was run at 8 m / min in a continuous annealing furnace maintained at 600°C), finish cold rolling, and low-temperature annealing are carried out.

[0006] Patent Document 3 discloses an invention of a Cu-Ni-Sn-P-based copper alloy strip for terminals that is excellent in strength, electrical conductivity, bending workability, and stress relaxation resistance. To produce such a copper alloy strip, the patent document discloses a manufacturing process that includes melting, hot rolling, cold rolling, intermediate annealing (600°C in the example, time not specified), finish cold rolling, and low-temperature annealing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-062592 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-262297 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-256814 Summary of the Invention [Problem to be solved by the invention]

[0008] When copper alloy sheet is bent at a very severe 90° angle (BW) with a bending radius R and thickness t ratio of approximately 0.25, microscopic wrinkles form on the outer surface of the bent part. As long as the wrinkles do not lead to cracks within the wall, they are generally considered to pose no problem from a strength perspective. For example, the Japan Copper and Brass Association (JCBA) Technical Standard T307 also uses a visual inspection method for wrinkles to evaluate bending workability. However, the magnitude of the surface irregularities caused by wrinkles (e.g., the arithmetic mean roughness Ra based on a roughness curve) does not accurately capture the surface morphology of the bent part. Because the material is stretched near the outer surface of the bent part, the actual surface profile deviates from the profile of an ideal smooth curve. When this deviation is significant, the surface morphology can be considered to have a "large depression" near the top of the outer surface of the bent part, which is generally depressed from the ideal smooth curve. In the 90° W bending test, BW stands for "Bad Way" and means that the bending axis is parallel to the rolling direction.

[0009] In current-carrying components formed by integrating resin materials, such as board-to-board connectors (also known as B2B connectors), a problem known as "resin fogging" can occur during the resin molding process, where resin seeps into recesses on the outer surface of the bent portion. As electronic devices have become more sophisticated in recent years, there has been a growing need for smaller, more compact current-carrying and heat-dissipating components, such as connectors, and narrower pitches. Thin-walled components and connectors with narrow pitches are susceptible to the effects of resin fogging, and even conventional Cu-Ni-Sn-P-based copper alloy materials, which are intended to improve bendability, have difficulty resolving the resin fogging problem. To solve this problem, it is important not only to reduce the surface roughness of the bent portion, but also to achieve a surface morphology that minimizes deviation from the ideal smooth curved surface profile.

[0010] An object of the present invention is to provide a copper alloy sheet material which, when subjected to severe bending, has a property that minimizes deviation of the actual profile from the profile of an ideal smooth curved surface on the outer peripheral surface of the bent portion, and which also has excellent strength. [Means for solving the problem]

[0011] In order to achieve the above object, the present specification discloses the following invention.

[0012] [1] In mass%, Ni (nickel): 0.1 to 5.0%, Sn (tin): 0.1 to 5.0%, P (phosphorus): 0.01 to 0.5%, Si (silicon): 0 to 0.5%, Ag (silver): 0 to 0.3%, Al (aluminum): 0 to 1.0%, B (boron): 0 to 0.2%, Be (beryllium): 0 to 0.15%, Co (cobalt): 0 to 1.0%, Cr (chromium): 0 to 0.5%, Fe (iron): 0 to 1.0%, Mg (magnesium): 0 to 0.5%, Mn( The chemical composition is: manganese: 0-1.0%, sulfur (S): 0-0.2%, titanium (Ti): 0-0.5%, zinc (Zn): 0-1.0%, zirconium (Zr): 0-0.3%, with the remainder being copper (Cu) and unavoidable impurities. When the measurement area on a cross section perpendicular to the rolling direction is measured using the electron backscatter diffraction (EBSD) method with a step size of 0.1 μm, the area is considered to be a grain boundary when the boundary with a crystal orientation difference of 5° or more is considered to be a grain boundary. A copper alloy sheet material having an average grain size of 1 to 4 μm by the fraction method, and an average value of GROD (Grain Reference Orientation Deviation - Angle) calculated by finding the average difference between the orientation of each measurement spot and the reference orientation of the crystal grain to which it belongs for all measurement spots in the measurement area, when a boundary with a crystal orientation difference of 5° or more is considered to be a grain boundary and the average orientation of measurement spots within the same crystal grain is taken as the reference orientation of that crystal grain, of 1 to 5°, and a tensile strength of 400 MPa or more.

[0013] [2] The copper alloy sheet material according to the above [1], wherein, in the measurement by the EBSD method with a step size of 0.1 μm, when a boundary having a crystal orientation difference of 5° or more is regarded as a crystal grain boundary, the average of the GOS (Grain Orientation Spread) value by the Area Fraction method is 5.0° or less.

[0014] [3] The copper alloy sheet material according to the above [1] or [2], wherein the ratio MBR / t of the minimum bending radius MBR at which cracks do not occur to the sheet thickness t in a 90°W bending test at BW in accordance with the Japan Copper and Brass Association technical standard JCBA T307:2007 is 0.5 or less.

[0015] [4] The copper alloy sheet material according to any one of the above [1] to [3], which has an electrical conductivity of 30% IACS or more.

[0016] [5] An electrical component using the copper alloy sheet material according to any one of [1] to [4] above as its material.

[0017] [6] A heat dissipation component using the copper alloy sheet material according to any one of [1] to [4] above as its material.

[0018] [7] A board-to-board connector using the copper alloy sheet material according to any one of [1] to [4] above as a material. [Effects of the Invention]

[0019] According to the present invention, a copper alloy sheet material has excellent strength, and when subjected to severe bending, it is possible to obtain a surface configuration that has little deviation from the profile of an ideal smooth curved surface on the outer peripheral surface of the bent portion. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a photograph showing an example of the outer peripheral surface appearance of the bent material of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a height profile measured on the outer peripheral surface of the bent material of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, an embodiment of the copper alloy sheet according to the present invention will be described. In this specification, the notation "n1~n2" indicating a numerical range means "n1 or more and n2 or less". Here, n1 and n2 are numerical values satisfying n1 < n2.

[0022] (1) Copper alloy sheet The copper alloy sheet of this embodiment is a sheet made of a copper alloy having a chemical composition of the Cu-Ni-Sn-P system (hereinafter also referred to as a Cu-Ni-Sn-P system copper alloy). Here, the "sheet" means a sheet-like metal material. A thin sheet-like metal material may also be called a "foil", and such a "foil" is also included in the "sheet" referred to here. A long sheet-like metal material wound in a coil shape is also included in the "sheet". In this specification, the thickness of the sheet-like metal material is referred to as the "sheet thickness".

[0023] In addition, the copper alloy sheet is configured such that when measured under predetermined conditions by the EBSD method (Electron Backscatter Diffraction), the average crystal grain size and the average value of GROD are within a predetermined range. Hereinafter, the chemical composition and each parameter will be specifically described.

[0024] [Chemical composition] The copper alloy sheet of this embodiment contains at least Ni, Sn, and P, and optionally contains optional elements (including the case where the total is 0% by mass), and the balance consists of Cu and unavoidable impurities. Hereinafter, "%" regarding alloy components means "% by mass" unless otherwise specified.

[0025] Ni dissolves in the Cu matrix and contributes to improving the strength, elasticity, and heat resistance of the base material. It also forms a compound with P, contributing to improving electrical conductivity and stress relaxation resistance. If the Ni content is less than 0.1%, it is difficult to effectively achieve the above effects. On the other hand, if the Ni content is excessive, electrical conductivity tends to decrease. For this reason, the Ni content must be 5% or less, more preferably 3% or less, and even more preferably 2% or less. A particularly preferred Ni content range is 0.5 to 1.5%.

[0026] Sn has a significant solid solution strengthening effect, and this effect is further enhanced when added in combination with Ni. Sn also improves stress relaxation resistance. To fully exert these effects, an Sn content of 0.1% or more is preferred. However, if the Sn content exceeds 5%, electrical conductivity drops significantly. Furthermore, since Sn is an element that easily segregates, cracks are likely to occur during hot rolling. For this reason, the Sn content must be 5% or less, preferably 3% or less, and more preferably 2% or less. In particular, it is even more preferable to adjust the Sn content to the range of 0.5 to 2%.

[0027] P contributes to improving strength, electrical conductivity, and stress relaxation resistance by forming precipitates with Ni. P also acts as a deoxidizer during melting and casting, reducing the oxygen concentration in the molten metal. To fully utilize these effects, it is preferable to ensure a P content of 0.01% or more. However, if the P content exceeds 0.5%, the formation of coarse Ni-P precipitates and the increase in hydrogen concentration due to excessive deoxidation can lead to casting defects and cracks during hot rolling. Furthermore, electrical conductivity and bending workability are also reduced. For this reason, the P content must be 0.5% or less. A particularly preferable P content range is 0.03 to 0.2%, with 0.04 to 0.15% being even more preferable.

[0028] The elements Si, Ag, Al, B, Be, Co, Cr, Fe, Mg, Mn, S, Ti, Zn, and Zr are optional elements, and one or more of these may be contained as needed.

[0029] Fe forms precipitates with P and, in some cases, also forms ternary compounds containing Ni. Furthermore, adding trace amounts of Fe disperses the nucleation sites of Ni-P compounds or Ni-Fe-P compounds, making it easier to obtain fine precipitates. However, since excessive Fe content can lead to aggregation and coarsening of precipitates, if Fe is added, the content must be kept to 1% or less. A content of 0.5% or less is more preferable, and a content of 0.3% or less is particularly preferable.

[0030] Zn improves solderability and strength, as well as castability. Another advantage of adding Zn is that it allows the use of inexpensive brass scrap. However, Zn content exceeding 1% tends to reduce electrical conductivity. Therefore, if Zn is added, it must be kept below 1%, preferably below 0.5%, more preferably below 0.3%, and most preferably below 0.2%.

[0031] Mg has the effect of improving stress relaxation resistance and desulfurizing. However, Mg is an element that is easily oxidized, and if its content exceeds 0.5%, castability will decrease. Therefore, if Mg is to be contained, it should be in the range of 0.5% or less, more preferably 0.3% or less, and particularly preferably 0.2% or less.

[0032] Co is an element that can form precipitates with P and also precipitate by itself, and the inclusion of Co is effective in simultaneously improving strength and electrical conductivity. However, Co is an expensive element, and if it exceeds 1%, it is disadvantageous in terms of cost. Therefore, if Co is to be included, it is limited to a range of 1% or less, preferably 0.5% or less, and more preferably 0.3% or less.

[0033] B, Cr, Mn, Ti, and Zr further increase alloy strength and reduce stress relaxation. Furthermore, B, Ti, and Zr have the effect of refining the cast structure, which can contribute to improving hot workability. Therefore, the B content should be 0-0.20%, Cr 0-0.50%, Mn 0-1.00%, Ti 0-0.50%, and Zr 0-0.30%. It is particularly desirable to include B in the ranges of 0-0.03%, Cr 0-0.30%, Mn 0-0.20%, Ti 0-0.15%, and Zr 0-0.15%. When one or more of B, Cr, Mn, Ti, and Zr are added, it is desirable that the total content of these elements be 0.01% or more to fully obtain the effects of each element. However, adding a large amount will adversely affect hot or cold workability and will be disadvantageous in terms of cost. Therefore, the total content of these elements is desirably 1.5% or less, more desirably 1% or less, and even more desirably 0.5% or less.

[0034] Be, Si, Ag, Al, and S have the effect of increasing strength, and when these elements are added, the contents are preferably in the ranges of Be: 0-0.15%, Si: 0-0.5%, Ag: 0-0.3%, Al: 0-1.0%, and S: 0-0.2%, and more preferably in the ranges of Be: 0-0.10%, Si: 0-0.2%, Ag: 0-0.05%, Al: 0-0.4%, and S: 0-0.015%. Therefore, the total content of these elements is preferably 1.5% or less, more preferably 1% or less, and even more preferably 0.5% or less.

[0035] The total amount of the optional added elements Si, Ag, Al, B, Be, Co, Cr, Fe, Mg, Mn, S, Ti, Zn, and Zr is preferably in the range of 1.5% or less, more preferably in the range of 1% or less, and even more preferably in the range of 0.5% or less.

[0036] [Average grain size] In the copper alloy sheet material of this embodiment, when a measurement area provided on a cross section perpendicular to the rolling direction (hereinafter also referred to as the LD plane) is measured by the EBSD method with a step size of 0.1 μm, and when boundaries with a crystal orientation difference of 5° or more are considered to be grain boundaries, the average crystal grain size measured by the Area Fraction method is 1 to 4 μm. If the average crystal grain size is outside the above range, it becomes difficult to stably obtain an appropriate surface morphology during severe bending in BW. The above average crystal grain size is more preferably 3.5 μm or less, even more preferably 3.0 μm or less, and can also be adjusted to 2.5 μm or less. The lower limit of the average crystal grain size is more preferably 1.2 μm or more.

[0037] [How to determine the average grain size] Here, a specific method for measuring the average crystal grain size will be described. A cross section perpendicular to the rolling direction of the sheet material (hereinafter referred to as the "LD plane") is observed using a field emission scanning electron microscope (FE-SEM). A rectangular measurement area measuring 48 μm in the width direction and 36 μm in the thickness direction, located between the 1 / 4 and 3 / 4 positions of the sheet thickness, is measured for crystal orientation using electron backscatter diffraction (EBSD) with a step size (measurement pitch) of 0.1 μm. If the sheet thickness is thin and a 36 μm field of view cannot be secured in the thickness direction, a rectangular measurement area measuring 48 μm in the width direction and extending from the 1 / 4 to 3 / 4 positions of the sheet thickness is measured. Using EBSD data analysis software, boundaries with a crystal orientation difference of 5° or more are considered grain boundaries. The grain size of all grains within the measurement area is determined using a diameter chart, and the average grain size is calculated using the area fraction method. For grains that extend beyond the boundary of the measurement area, the area of ​​the portion within the measurement area is used to calculate the average grain size. This procedure is performed on five randomly selected non-overlapping measurement areas, and the arithmetic mean of the average grain size values ​​obtained from the five fields is taken as the average grain size (μm). Twin boundaries are also considered as grain boundaries when calculating the average grain size. Here, "plate thickness 1 / 4 position" means a position in the plate thickness direction that is t / 4 (mm) away from one rolling surface, where t (mm) is the plate thickness. Similarly, "plate thickness 3 / 4 position" means a position in the plate thickness direction that is 3t / 4 (mm) away from the rolling surface.

[0038] [GROD average value] In the copper alloy sheet material of this embodiment, the average GROD value is 1 to 5° when a boundary (including twin boundaries) with a crystal orientation difference of 5° or more is considered to be a grain boundary in the above-mentioned EBSD measurement. The average GROD value is an index showing the magnitude of the residual stress accumulated inside each crystal grain in the sheet material as a whole. The average GROD value corresponds to the average value calculated by determining the orientation differences between all measurement spots in the measurement area and the reference orientation of the crystal grain to which each measurement spot belongs. Here, the average orientation of measurement spots within the same crystal grain is used as the reference orientation of each crystal grain. Research by the inventors has found that this average GROD value has a significant effect on the morphology of the outer peripheral surface of the bent portion. In order to stably obtain an appropriate surface morphology during severe bending at BW, it is extremely effective for the average GROD value to be 5° or less. A value of 4.5° or less is more preferable, and a value of 4.0° or less is even more preferable. Regarding the lower limit of the GROD average value, since excessive reduction of the residual stress leads to an increase in the process load in manufacturing the copper alloy sheet material, the lower limit is set to a range of 1.0° or more, more preferably 1.5° or more, further preferably 2.0° or more, and particularly preferably 2.5° or more.

[0039] [How to calculate the average GROD value] Based on the above EBSD measurement data measured on the LD surface with a step size (measurement pitch) of 0.1 μm, EBSD data analysis software was used to consider boundaries with an orientation difference of 5° or more as grain boundaries (including twin boundaries), and the average orientation of the measurement spots within the same grain was taken as the reference orientation of that grain.The values ​​(°) of the orientation difference GROD (Grain Reference Orientation Deviation - Angle) between the reference orientation of the grain to which the spot belongs was calculated for all measurement spots in the measurement area, and the average of these was taken as the average GROD (°).

[0040] [Average GOS value] In the copper alloy sheet material of the present embodiment, when subjected to severe bending, it is preferable that the average value of the GOS value falls within a predetermined range, from the viewpoint of further suppressing the deviation of the actual profile from the profile of an ideal smooth curved surface on the outer peripheral surface of the bent portion.

[0041] The average GOS value is an index that provides clues to the misorientation and deformation of a given crystal grain as a whole. To obtain an appropriate surface morphology during severe bending in BW, the average GOS value is preferably 5.0° or less when boundaries (including twin boundaries) with a crystal misorientation of 5° or more are considered as grain boundaries in the above-mentioned EBSD measurement, with the measurement step size set to a minute size of 0.1 μm. It is more preferable that it is 4.5° or less, and even more preferable that it is 4.0° or less. However, even if the average GOS value meets this requirement, if the average GOS value is not controlled within the above-mentioned specified range, it is not possible to consistently achieve an appropriate surface morphology during severe bending in BW. There is no particular lower limit for the average GOS value, but it is usually sufficient to control it to a range of 2.0° or more.

[0042] [How to calculate the average GOS value] Based on the above EBSD measurement data measured on the LD plane with a step size (measurement pitch) of 0.1 μm, the average value of the GOS (Grain Orientation Spread) value (°) is calculated using the Area Fraction method with EBSD data analysis software. For crystal grains where part of the grain protrudes beyond the boundary of the measurement area, the part that exists within the measurement area is used as is to calculate the GOS value.

[0043] [Maximum deviation from the ideal smooth curved surface of the outer periphery of the bent part] The copper alloy sheet of this embodiment has a predetermined chemical composition, and the average grain size and average GROD values ​​are within predetermined ranges, so that when subjected to severe bending, the deviation of the actual profile from the ideal smooth curved surface profile of the outer peripheral surface of the bent portion is small. Specifically, when the copper alloy sheet is evaluated in a 90°W bending test at BW (described later) with a width of 0.4 mm and an R / t of 0.25, the maximum deviation of the outer peripheral surface of the bent portion from the ideal smooth curved surface is preferably 7.0 μm or less. It is also possible to obtain sheet materials with this maximum deviation of 6.0 μm or less, or even 5.0 μm or less, or 4.0 μm or less. Note that it is difficult to completely eliminate this maximum deviation, and it is usually 0.1 μm or more, or 1.0 μm or more. Details of how to determine the maximum deviation will be explained in the examples.

[0044] [MBR / t by 90°W bending test] In the copper alloy sheet material of this embodiment, the ratio MBR / t of the minimum bending radius MBR at which cracks do not occur to the sheet thickness t, measured in a 90°W bending test at BW in accordance with the Japan Copper and Brass Association technical standard JCBA T307:2007, is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. It is also possible to obtain a sheet material with an MBR / t of 0. Note that the MBR / t in this test is a conventional general index for evaluating bending workability that indicates how severe the bending can be before cracks occur. In a Cu-Ni-Sn-P-based copper alloy sheet material whose chemical composition, average grain size, and average GROD value are not controlled within the above-mentioned appropriate ranges, even if the bending workability measured by MBR / t is good, it is difficult to stably achieve a surface morphology with little deviation from an ideal smooth curved surface in severe bending at BW.

[0045] JCBA T307:2007 states, "This standard applies to the evaluation of the bending workability of copper and copper alloy thin strips with a thickness of 0.1 mm or more and 0.8 mm or less." The inventors' investigations confirmed that the W-bend test conforming to this standard can also be used to evaluate the bending workability of Cu-Ni-Sn-P-based copper alloy sheets with a thickness of less than 0.1 mm. Therefore, in this embodiment, the BW W-bend test method specified in JCBA T307:2007 is extended and applied as is to sheets with a thickness of less than 0.1 mm (e.g., 0.02 mm or more and less than 0.1 mm). The width of the test piece may be, for example, 10 mm.

[0046] [Tensile strength] The copper alloy sheet material of this embodiment has a tensile strength in the direction parallel to the rolling direction (LD) of 400 MPa or more. The tensile strength is preferably 450 MPa or more. The tensile strength in the rolling direction can be adjusted to a strength level of 470 MPa or more, or even 500 MPa or more. The upper limit of the tensile strength is not particularly limited, but it may be adjusted to, for example, a range of 700 MPa or less, or may be adjusted to a range of 650 MPa or less.

[0047] [conductivity] In the use of the copper alloy sheet material of this embodiment, it is preferable that the conductivity is 30% IACS or more, more preferably 33% IACS or more, and even more preferably 35% IACS or more. The upper limit of the conductivity of the copper alloy sheet material is not particularly limited, but for example, the conductivity is 60% or less.

[0048] (2) Manufacturing method of copper alloy sheet material The copper alloy sheet material described above can be manufactured, for example, by the following manufacturing process. Specifically, the manufacturing method of the copper alloy sheet material includes a melting and casting process, a slab heating process, a hot rolling process, a rough cold rolling process, an intermediate annealing process, an intermediate cold rolling process, a recrystallization annealing process, a finish cold rolling process, and a low-temperature annealing process. After hot rolling, facing is performed as needed, and after each heat treatment, pickling, polishing, or further degreasing is performed as needed. Each of the above processes will be described below.

[0049] [Melting and casting process] A typical copper alloy melting method can be followed. A cast piece having a predetermined chemical composition can be produced by continuous casting, semi-continuous casting, etc. For continuous casting, it is desirable to use a vertical or horizontal casting furnace.

[0050] [Slab heating process] The slab can be heated before hot rolling by, for example, holding it at 700 to 950°C for 0.5 to 5 hours.

[0051] [Hot rolling process] In the case of hot rolling, the first rolling pass is performed at 700°C or higher, where recrystallization is likely to occur, to destroy the cast structure and achieve homogenization of the components and structure. However, rolling at temperatures above 950°C is undesirable because it may cause cracks in areas with lower melting points, such as areas where alloy components segregate. To ensure complete recrystallization during the hot rolling process, it is effective to perform rolling at a temperature of 60% or more in the 950-700°C temperature range. This further promotes homogenization of the structure. However, since a large rolling load is required to achieve a reduction of 60% or more in one pass, it is preferable to perform multiple passes to ensure a total reduction of 60% or more. The total reduction in hot rolling is preferably 60-99%, with approximately 70-95% being sufficient. After hot working, rapid cooling by water cooling or other methods is preferable. If continuous casting is performed, hot rolling may be omitted.

[0052] The reduction rate (%) in the rolling pass is determined by the following formula (1). Rolling reduction rate (%)=100×(t0-t1) / t0…(1) t0: Plate thickness before the rolling pass (mm) t1: Plate thickness at the end of the rolling pass (mm) The total rolling ratio (%) in a rolling process is determined by the following formula (2). Total rolling ratio (%) = 100 × (h0-h1) / h0…(2) h0: Plate thickness before the first pass of the rolling process (mm) h1: Plate thickness at the end of the final rolling pass of the rolling process (mm)

[0053] [Rough cold rolling process] Next, cold rolling is performed. The cold rolling at this stage is referred to as "rough cold rolling" in this specification. The rolling reduction ratio in rough cold rolling can be, for example, 50 to 99%, preferably 60% or more, and more preferably 70% or more. In this way, an intermediate product sheet material to be subjected to intermediate annealing can be obtained.

[0054] [Intermediate annealing process] The intermediate product sheet material is subjected to intermediate annealing. In this intermediate annealing, recrystallization is performed using the strain introduced by rough cold rolling as the driving force. Either a continuous annealing furnace or a batch annealing furnace may be used for intermediate annealing. In the case of a continuous annealing furnace, the heating temperature is set in the temperature range of 550 to 750°C. If the heating temperature is higher than 750°C, the crystal grains may become too large. The holding time in the heating temperature range may be set, for example, in the range of 10 to 600 seconds. In the case of a batch annealing furnace, the heating temperature is set in the temperature range of 400 to 600°C. If the heating temperature is higher than 600°C, the crystal grains may become too large. The holding time in the heating temperature range may be set, for example, in the range of 1 to 60 hours.

[0055] [Intermediate cold rolling process] Cold rolling performed on material that has undergone intermediate annealing is called intermediate cold rolling. The purpose of intermediate cold rolling is to reduce the plate thickness as well as to introduce strain. If the introduction of strain is insufficient, sufficient recrystallization nucleation sites cannot be secured in the subsequent recrystallization annealing, making it difficult to refine the crystal grains. In intermediate cold rolling, the total rolling reduction is set to 50% or more. A total rolling reduction of 80% or more is more effective, and 85% or more is even more effective. There is no particular upper limit to the total rolling reduction, but it is usually set to a range of 99% or less depending on the capacity of the cold rolling mill.

[0056] [Recrystallization annealing process] In the material that has undergone intermediate cold rolling, strain is introduced into the crystals of the matrix (metallic base material). Sheet material in this structural state is subjected to recrystallization annealing. In this recrystallization annealing, in order to realize excellent bending workability and bent skin (proper surface morphology) in the copper alloy sheet material as a product, the heat treatment conditions are controlled so that the total value of the movement distance of copper during heat treatment is 10 to 150 nm, more preferably 20 to 100 nm, and even more preferably 25 to 60 nm.

[0057] The distance traveled by copper during heat treatment is calculated by measuring the material temperature every second, calculating the diffusion coefficient of copper in copper at each temperature every second, and then calculating the distance traveled by copper every second using equation (3). These values ​​are then added together. TIFF2025159709000002.tif11170Here, x is the distance traveled by copper during heat treatment, and D is the diffusion coefficient. The diffusion coefficient is taken from the value listed in the Metal Data Book, Revised 3rd Edition (edited by the Japan Institute of Metals, Maruzen (1993) p. 21.), and the diffusion coefficient D of copper in copper at each temperature is calculated using the following formula (4). D = D0 exp(-Q / RT)…(4) where D0 is 7.8 × 10 -5 [m 2 / s], Q was 211 [kJ / mol], and R (gas constant) was 8.314 [J / (mol K)]. The diffusion coefficient D at each temperature was used to calculate the distance traveled by copper per second at each temperature, and these were integrated to determine the distance traveled by copper during heat treatment (nm). The distance traveled by copper during heat treatment is calculated by adding up the distance traveled by copper from the point when the material temperature reaches 100°C until it is further heated to its maximum temperature, and after heating is completed (and held at the maximum temperature if necessary), until it is cooled down to 100°C.

[0058] In this way, the strain introduced by the intermediate cold rolling is utilized to cause new recrystallization from many locations, and the average crystal grain size is controlled to 1 to 4 μm.

[0059] The recrystallization annealing can be carried out under conditions set such that the copper migration distance during heat treatment is 10 to 150 nm, for example, at a furnace temperature of 550 to 750° C. and a holding time of 10 to 1000 seconds.

[0060] [Finishing cold rolling process] The cold rolling performed on material that has undergone recrystallization annealing is called "finish cold rolling." In finish cold rolling, the plate thickness is reduced and the microscopic crystal grain size determined by the EBSD measurement mentioned above is refined, and it is necessary to control it so that it reaches the specified GROD value. In finish cold rolling, it is important to reduce the plate thickness while taking care not to impart too much strain to the crystals, and careful control is required. Specifically, the total rolling reduction must be between 40% and 80%, the number of rolling passes with a reduction of 20% or more must be between 0 and 3, and the average unit tension (average value of each pass) must be 250 N / mm 2 The conditions are as follows: The unit tension is calculated by multiplying the tension (N) by the cross-sectional area of ​​the plate (plate width x plate thickness) (mm 2 ) In order to achieve good bending workability, it is desirable that the total rolling reduction be 40% or more and 65% or less.

[0061] [Low temperature annealing process] In this embodiment, low-temperature annealing is finally performed to reduce distortion. For the low-temperature annealing, conditions such as holding at 350 to 450° C. for 10 to 600 seconds can be adopted.

[0062] As a result, the copper alloy sheet material of this embodiment is obtained. When the copper alloy sheet material is subjected to severe bending, it is possible to realize a surface configuration with little deviation from the profile of an ideal smooth curved surface on the outer peripheral surface of the bent portion. The final sheet thickness can be, for example, in the range of 0.05 to 0.50 mm.

[0063] (3) Current-carrying components, heat-dissipating components, and board-to-board connectors The current-carrying components, heat-dissipating components, and board-to-board connectors are formed by a process including bending using the above-mentioned copper alloy sheet material. The current-carrying components, heat-dissipating components, and board-to-board connectors have high reliability in terms of durability of the bent portion. For example, copper alloy sheets for board-to-board connectors are required to have a good bent surface when formed to a sheet width of 0.5 mm or less, and the copper alloy sheet material of this embodiment has properties that satisfy this requirement. [Example]

[0064] (1) Manufacturing of copper alloy sheets In this example, first, a copper alloy sheet material was produced.

[0065] Example 1 Copper alloys having the chemical compositions shown in Table 1 were melted and cast. The resulting slabs (thickness: 180 mm) were heated at 920°C for 60 minutes, then hot rolled to the thicknesses shown in Table 2, and water-cooled. After hot rolling, the surface oxide layer was removed (face-ground) by mechanical polishing, and each hot-rolled material was cold-rolled to the thicknesses shown in the "Rough cold rolling" column in Table 4, to obtain intermediate product sheets.

[0066] The intermediate product sheets were subjected to intermediate annealing (carried out in a batch annealing furnace), intermediate cold rolling, recrystallization annealing, finish cold rolling, and low-temperature annealing in the order shown in Table 4 to obtain test materials for the various evaluations described below. The thicknesses of the test materials are shown in the "Final thickness" column in Table 2. The following investigations were carried out for each test material.

[0067] In the recrystallization annealing of Example 1, the material that had undergone intermediate cold rolling was placed in a continuous annealing furnace set at 700°C, held there for 30 seconds, and then rapidly cooled by being placed in a cooling chamber set at room temperature. The copper migration distance during the heat treatment of recrystallization annealing was calculated using the method described above, measuring the copper migration distance (diffusion distance) from when the material was heated from 100°C to the maximum temperature (average heating rate of 23°C / sec) and then cooled to 100°C (average cooling rate of 17°C / sec). The resulting copper migration distance was 35 nm.

[0068] (Examples 2 to 18, Comparative Examples 1 to 5) In Examples 2 to 18 and Comparative Examples 1 to 5, copper alloy sheets were produced in the same manner as in Example 1, except that the chemical compositions were changed as shown in Tables 1 to 3 and the production conditions were appropriately changed as shown in Tables 4 to 6. In the recrystallization annealing, the movement distance of copper during heat treatment was adjusted by changing the setting of the maximum temperature and / or the setting of the holding time at the maximum temperature.

[0069] (2) Evaluation method for copper alloy sheet materials The obtained copper alloy sheets were evaluated by the following methods.

[0070] (Average grain size) The cross section (LD plane) perpendicular to the rolling direction of the sample was polished with a cross-section polisher (JEOL Ltd., IB-19530CP) at an accelerating voltage of 4 kV to prepare the specimen surface for EBSD (electron backscatter diffraction) measurement. The specimen surface was observed with a field emission scanning electron microscope (FE-SEM) (JEOL Ltd., JSM-7200F) at an accelerating voltage of 15 kV and a magnification of 2500x. Crystal orientation data were collected using the EBSD method with a step size of 0.1 μm for a rectangular measurement area measuring 48 μm in the width direction and 36 μm in the thickness direction, located between the 1 / 4 and 3 / 4 positions of the plate. The average grain size was calculated using the area fraction method based on the crystal orientation data measured for five non-overlapping measurement areas, as described above under "Method for determining average grain size." The EBSD data analysis software used was OIM-Analysis 7.3.1 manufactured by TSL Solutions Co., Ltd. (the same applies to the calculation of the average GROD value and GOS value described below).

[0071] (GROD average value) Based on the crystal orientation data collected by the EBSD method, the average GROD value was calculated according to the above-mentioned "Method for calculating the average GROD value."

[0072] (Average GOS value) Based on the crystal orientation data collected by the EBSD method, the average GOS value was calculated according to the above-mentioned "Method for calculating the average GOS value."

[0073] (Maximum deviation from the ideal smooth curved surface of the outer periphery of the bent part) Test specimens measuring 30 mm in length and 0.4 mm in width were cut from the test material so that the longitudinal direction of the specimen coincided with the direction perpendicular to the rolling direction on the surface of the test material. A 90°W bending test was performed in accordance with the Japan Copper and Brass Association Technical Standard JCBA T307:2007, with a BW of 0.25 (R / t, where R (mm) is the ratio of the bending radius to the plate thickness) of 0.25. The outer peripheral surface of the bent portion of the test specimen was observed using a laser microscope (Keyence VK-X3000), and the height profile of the outer peripheral surface of the bent portion was measured when scanning in a direction perpendicular to the width direction of the test specimen. A 50x objective lens was used for observation. The height direction of the profile corresponded to the direction of travel of the jig during bending. The specific measurement method is explained using Figures 1 and 2 as examples.

[0074] 1 shows an example of an appearance photograph of the bent outer peripheral surface of the copper alloy sheet material of the present invention (Example 1) viewed in a direction corresponding to the direction of travel of the jig during bending. The horizontal direction of the photograph is the width direction of the test piece (i.e., the direction parallel to the bending axis), and the straight line shown in the photograph, parallel to the vertical direction of the photograph, is the profile measurement line.

[0075] Figure 2 shows an example of a height profile measured for the surface shown in Figure 1. The measured profile (solid line) exhibits many irregularities at depths of approximately 8 μm from the apex (highest point). Therefore, a polynomial approximation curve (quadratic function) was created using the data from the measured profile curve within a depth range of 8–20 μm from the apex. Measurement position data (the horizontal axis in Figure 2) were acquired in increments of approximately 0.25 μm, and the polynomial approximation curve was created using the least-squares method. The polynomial approximation curve thus obtained was designated the "ideal profile" and was considered to represent the cross-sectional curve of the ideal, smooth curved surface of the outer periphery of the bent part. The ideal profile is shown by a dashed line in Figure 2. It can be seen that the actual outer periphery of the bent part exhibits a surface morphology that is slightly depressed near the apex. The maximum height distance (μm) between the ideal profile (dashed line) and the measured profile (solid line) at the same scanning direction position is defined as the "maximum deviation." In the example shown in this figure, the maximum deviation was 6 μm.

[0076] This maximum deviation measurement was performed on five randomly set measurement lines for one test piece, and the maximum of the five maximum deviation values ​​was taken as the maximum deviation of that test piece. The maximum deviation was determined for three test pieces (n=3), and the average of the maximum deviation measurements for the three test pieces was used as the maximum deviation performance value for that test material.

[0077] The maximum deviation was measured for the bending test pieces of each test material by the above method. A Cu-Ni-Sn-P based copper alloy sheet material having a maximum deviation of 7.0 μm or less, preferably 6.5 μm or less, according to this test method is evaluated as having a property in which the surface morphology of the bent portion is significantly improved compared to conventional ones.

[0078] (MBR / t by 90°W bending test) In addition to the evaluation of the maximum deviation, bending workability was evaluated as follows using a standard bending test. In accordance with the Japan Copper and Brass Association technical standard JCBA T307:2007, a W-bend test was performed on the blank width to determine the ratio (MBR / t) of the minimum bending radius (MBR) at which cracks did not occur to the sheet thickness (t). The test specimen size was 30 mm in the direction perpendicular to the rolling direction on the surface of the test material and 10 mm in the rolling direction (width). The presence or absence of cracks on the bent surface was determined according to JCBA T307:2007. For samples judged to have "large wrinkles" in the appearance observation of the bent surface, a specimen was cut perpendicular to the bending axis at the deepest wrinkle, and the polished cross section was observed under an optical microscope to check for the presence of cracks extending into the sheet thickness. If no cracks were found, the specimen was judged to have "no cracks observed." Considering the intended use of the material of the present invention, an MBR / t of 0.5 or less in this test is considered to have good bending workability.

[0079] (tensile strength) Tensile test pieces (JIS No. 5) were taken from each test material in the direction parallel to the rolling direction, and tensile tests were conducted in accordance with JIS Z2241 with the number of tests (n = 3) to measure the tensile strength. The average value of n = 3 was used as the performance value for the test material.

[0080] (conductivity) The electrical conductivity of each test material was measured by the double bridge average cross-sectional area method in accordance with JIS H0505.

[0081] (3) Evaluation results The evaluation results are shown in Tables 7 to 9.

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3]

[0085] [Table 4]

[0086] [Table 5]

[0087] [Table 6]

[0088] [Table 7]

[0089] [Table 8]

[0090] [Table 9]

[0091] The copper alloy sheets of Examples 1 to 18, in which the chemical composition and sheet manufacturing conditions were strictly controlled within the above-mentioned appropriate ranges, all exhibited a microstructure in which the average crystal grain size and average GROD value were within the ranges specified in the present invention, and the maximum deviation from an ideal smooth curved surface of the bent outer periphery (hereinafter simply referred to as "maximum deviation") was 7.0 μm or less, and some were even 5.0 μm or less. Furthermore, these sheets also had good bending workability as evaluated by a conventional method, with strengths of 400 MPa or more and electrical conductivity of 30% IACS or more.

[0092] In contrast, in the copper alloy sheet material of Comparative Example 1, the copper movement distance during the heat treatment in the recrystallization annealing was 176 nm, which was too large, and the crystal grain size was 5.8 μm, exceeding 4 μm. As a result, the maximum deviation was large. The copper alloy sheet material of Comparative Example 2 had a large number of rolling passes with a reduction of 20% or more in finish rolling, so the average GROD was 5.4°, which was higher than 5°, and as a result, the maximum deviation was large. In the copper alloy sheet material of Comparative Example 3, the average unit tension in the finish rolling was too large, so the average GROD value was 5.4°, which was higher than 5°, and as a result, the maximum deviation was large. In the copper alloy sheet material of Comparative Example 4, the movement distance of copper during heat treatment in recrystallization annealing was 3 nm, which was too small, so the crystal grain size was 0.9 μm, less than 1 μm. The average GROD was also large, at 6.3°, exceeding 5°. As a result, cracks occurred in the bending evaluation, and the maximum deviation could not be measured. In the copper alloy sheet material of Comparative Example 5, the total rolling reduction ratio in the finish rolling was too small, so the tensile strength was less than 400 MPa, and the improvement in strength was insufficient.

Claims

1. a chemical composition, in mass %, of Ni (nickel): 0.1 to 5.0%, Sn (tin): 0.1 to 5.0%, P (phosphorus): 0.01 to 0.5%, Si (silicon): 0 to 0.5%, Ag (silver): 0 to 0.3%, Al (aluminum): 0 to 1.0%, B (boron): 0 to 0.2%, Be (beryllium): 0 to 0.15%, Co (cobalt): 0 to 1.0%, Cr (chromium): 0 to 0.5%, Fe (iron): 0 to 1.0%, Mg (magnesium): 0 to 0.5%, Mn (manganese): 0 to 1.0%, S (sulfur): 0 to 0.2%, Ti (titanium): 0 to 0.5%, Zn (zinc): 0 to 1.0%, Zr (zirconium): 0 to 0.3%, with the balance being Cu (copper) and unavoidable impurities; In measurements of a measurement area provided on a cross section perpendicular to the rolling direction by the EBSD method (electron backscatter diffraction method) with a step size of 0.1 μm, If a boundary with a crystal orientation difference of 5° or more is considered a grain boundary, The average crystal grain size measured by the Area Fraction method is 1 to 4 μm, If a boundary with a crystal orientation difference of 5° or more is considered a grain boundary, When the average orientation of the measurement spots within the same crystal grain is taken as the reference orientation of the crystal grain, the average value of the GROD (Grain Reference Orientation Deviation - Angle) obtained by calculating the average value of the orientation difference between each measurement spot and the reference orientation of the crystal grain to which it belongs for all measurement spots in the measurement area is 1 to 5°, A copper alloy sheet material having a tensile strength of 400 MPa or more.

2. In the measurement using the EBSD method with a step size of 0.1 μm, 2. The copper alloy sheet according to claim 1, wherein, when a boundary having a crystal orientation difference of 5° or more is considered to be a grain boundary, an average GOS (Grain Orientation Spread) value measured by the Area Fraction method is 5.0° or less.

3. 3. The copper alloy sheet material according to claim 1, wherein a ratio MBR / t of a minimum bending radius MBR at which cracking does not occur to a sheet thickness t in a 90° W bending test at B.W. in accordance with Japan Copper and Brass Association Technical Standard JCBA T307:2007 is 0.5 or less.

4. The copper alloy sheet material according to claim 1 or claim 2, wherein the electrical conductivity is 30% IACS or more.

5. A current-carrying part using the copper alloy sheet material according to claim 1 or 2 as a material.

6. A heat dissipation part using the copper alloy sheet material according to claim 1 or 2 as a material.

7. A board-to-board connector using the copper alloy sheet material according to claim 1 or 2 as a material.

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