Copper alloy sheet material, current-carrying component, heat dissipation component, and board-to-board connector

Abstract

Provided is a copper alloy sheet material having a chemical composition of, in mass%, Ni: 0.1-5.0%, Sn: 0.1-5.0%, and P: 0.01-0.5%, which may contain certain optional elements, with the balance being Cu and unavoidable impurities. In measurement at a step size of 0.1 μm by EBSD, the average crystal grain size by the area fraction method, taking a boundary having a crystal orientation difference of 5° or more as a crystal grain boundary, is 1-4 μｍ, and the GROD average value is 1-5°.

Description

Copper alloy sheets, current-carrying components, heat-dissipating components, and board-to-board connectors

[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.

[0002] With the development of electronics, the electrical wiring of various machines has become increasingly complex and highly integrated, which has led to demands for smaller, lighter, more reliable, and less expensive electrical and electronic components such as connectors. Furthermore, copper alloy materials used as materials for 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 have excellent tensile strength, conductivity, heat dissipation, stress relaxation resistance, bending workability, and other properties, 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 bending workability. Various studies have been conducted to date on methods for improving the strength and bending workability 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 having 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 the copper alloy sheet 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 - low-temperature annealing is 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.

[0007] JP 2009-062592 A JP 2001-262297 A JP 2000-256814 A

[0008] When copper alloy sheet material is subjected to a severe 90° bending process at a bending radius R / thickness t ratio of approximately 0.25 (B.W.), microscopic wrinkles form on the outer surface of the bent portion. As long as the wrinkles are not "cracks" that lead to cracks within the wall, they are generally considered to pose no problem from a strength perspective. For example, the bending workability evaluation specified in the Japan Copper and Brass Association Technical Standard JCBA T307 also employs an evaluation method based on visual inspection of wrinkles. However, the surface morphology of the bent portion cannot be accurately determined by the magnitude of the surface irregularities formed by the wrinkles (e.g., the arithmetic mean roughness Ra based on a roughness curve). Because the material is stretched near the outer surface of the bent portion, the actual surface profile deviates from the profile of an ideal smooth curved surface. When this deviation is significant, the surface morphology can be considered to have a "large recess" near the apex of the outer surface of the bent portion, which is generally depressed from the ideal smooth curved surface. It should be noted that B.W. in the 90° W bending test is an abbreviation 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 (so-called B2B connectors), a problem known as "resin fogging" can occur during the resin molding process, whereby resin seeps into recesses on the outer surface of the bent portion. Recently, as electronic devices have become more sophisticated, there has been a growing need for smaller, narrower pitch current-carrying and heat-dissipating components, such as connectors. 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 designed to improve bending workability 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 deviates little from the profile of an ideal smooth curved surface.

[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.

[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 steel has a chemical composition consisting of: manganese: 0 to 1.0%, sulfur (S): 0 to 0.2%, titanium (Ti): 0 to 0.5%, zinc (Zn): 0 to 1.0%, zirconium (Zr): 0 to 0.3%, the balance being copper (Cu) and unavoidable impurities, and in a measurement area provided on a cross section perpendicular to the rolling direction using an electron backscatter diffraction (EBSD) method with a step size of 0.1 μm, when boundaries with a crystal orientation difference of 5° or more are considered to be crystal grain boundaries, the Area A copper alloy sheet material having an average crystal grain size of 1 to 4 μm by the fraction method, and when a boundary with a crystal orientation difference of 5° or more is considered to be a crystal grain boundary, and the average orientation of measurement spots within the same crystal grain is taken as the reference orientation of that crystal grain, the average value of the GROD (Grain Reference Orientation Deviation - Angle) obtained by calculating 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 region is 1 to 5°, and having a tensile strength of 400 MPa or more.

[0013] [2] 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 grain boundary, an average GOS (Grain Orientation Spread) value by the Area Fraction method is 5.0° or less. The copper alloy sheet material according to [1] above.

[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 cracking does not occur to the 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.

[0015] [4] The copper alloy sheet material according to any one of [1] to [3] above, having a 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 a material.

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

[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.

[0020] Fig. 1 is a photograph illustrating the appearance of the outer peripheral surface of a bent material of the present invention. Fig. 2 is a diagram illustrating the height profile measured on the outer peripheral surface of a bent material of the present invention.

[0021] An embodiment of the copper alloy sheet material according to the present invention will be described below. In this specification, the notation "n1 to n2" indicating a numerical range means "not less than n1 and not more than n2." Here, n1 and n2 are numerical values ​​that satisfy n1<n2.

[0022] (1) Copper Alloy Sheet Material The copper alloy sheet material of this embodiment is a sheet material made of a copper alloy having a Cu-Ni-Sn-P chemical composition (hereinafter also referred to as a Cu-Ni-Sn-P copper alloy). Here, "sheet material" refers to a sheet-shaped metal material. Thin sheet-shaped metal materials are sometimes called "foils," and such "foils" are also included in the "sheet material" referred to here. Long sheet-shaped metal materials wound into a coil are also included in the "sheet material." In addition, in this specification, the thickness of a sheet-shaped metal material is referred to as "sheet thickness."

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

[0024] [Chemical composition] The copper alloy sheet material of this embodiment contains at least Ni, Sn, and P, and optionally contains optional elements (including cases where the total is 0 mass%), with the balance being Cu and unavoidable impurities. Hereinafter, "%" regarding alloy components means "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 compounds 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. Therefore, 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 by its combined addition with Ni. Sn also has the effect of improving stress relaxation resistance. To fully exert these effects, a Sn content of 0.1% or more is preferable. However, if the Sn content exceeds 5%, the electrical conductivity decreases 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 it 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 necessary.

[0029] Fe forms precipitates with P and, in some cases, also forms ternary compounds including Ni. Furthermore, adding a small amount 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 leads to aggregation and coarsening of precipitates, if Fe is added, the content must be 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. Furthermore, the addition of Zn has the advantage of allowing the use of inexpensive brass scrap. However, a Zn content of more than 1% tends to reduce electrical conductivity. Therefore, if Zn is included, it must be kept at 1% or less, preferably 0.5% or less, more preferably 0.3% or less, and particularly preferably 0.2% or less.

[0031] Mg has the effect of improving stress relaxation resistance and desulfurization. However, Mg is an element that is easily oxidized, and if its content exceeds 0.5%, castability will decrease. Therefore, if Mg is 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 can 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, when Co is included, it is contained in 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 and can contribute to improving hot workability. Therefore, it is desirable to include B in the ranges of 0-0.20%, Cr in the ranges of 0-0.50%, Mn in the ranges of 0-1.00%, Ti in the ranges of 0-0.50%, and Zr in the ranges of 0-0.30%. It is particularly desirable to include B in the ranges of 0-0.03%, Cr in the ranges of 0-0.30%, Mn in the ranges of 0-0.20%, Ti in the ranges of 0-0.15%, and Zr in the ranges of 0-0.15%. When one or more of B, Cr, Mn, Ti, and Zr are included, it is desirable to include them in such a way that the total amount is 0.01% or more to fully utilize the effects of each element. However, if they are contained in large amounts, it will have a negative effect on hot or cold workability and will also be disadvantageous in terms of cost, so the total content of these elements is preferably in the range of 1.5% or less, more preferably 1% or less, and even more preferably 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 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 optionally 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 region provided on a cross section perpendicular to the rolling direction (hereinafter also referred to as the LD surface) 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 grain size measured by the Area Fraction method is 1 to 4 μm. If the average grain size is outside the above range, it becomes difficult to stably obtain an appropriate surface morphology during severe bending at B.W. The above average 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 grain size is more preferably 1.2 μm or more.

[0037] [Method of Determining Average Grain Size] Here, a specific method for measuring the average grain size will be described. A cross section of the sheet material perpendicular to the rolling direction (hereinafter sometimes referred to as the "LD surface") is observed using an FE-SEM (field emission scanning electron microscope), and the crystal orientation is measured using an EBSD (electron backscatter diffraction) method with a step size (measurement pitch) of 0.1 μm for a rectangular measurement area of ​​48 μm in the sheet width direction and 36 μm in the sheet thickness direction, which is set within the range from the 1 / 4 position to the 3 / 4 position of the sheet thickness. If the sheet thickness is thin and a 36 μm field of view in the sheet thickness direction cannot be secured, a rectangular measurement area of ​​48 μm in the sheet width direction and from the 1 / 4 position to the 3 / 4 position of the sheet thickness is measured. Using EBSD data analysis software, boundaries with a crystal orientation difference of 5° or more are considered to be grain boundaries, and the grain sizes of all grains within the measurement area are determined using a diameter chart, and the average grain size is calculated using the area fraction method. For crystal grains whose portions extend beyond the boundaries of the measurement area, the area of ​​the portion present within the measurement area is used as is to calculate the average crystal grain size. This operation is performed on five randomly selected, non-overlapping measurement areas, and the arithmetic mean of the average crystal grain sizes obtained in the five fields is taken as the average crystal grain size (μm). Note that twin boundaries are also considered as crystal grain boundaries, and the average crystal grain size is calculated. Here, "sheet thickness 1 / 4 position" refers to a position in the sheet thickness direction that is t / 4 (mm) away from one of the rolling surfaces, where t (mm) is the sheet thickness. Similarly, "sheet thickness 3 / 4 position" refers to a position in the sheet thickness direction that is 3t / 4 (mm) away from the above-mentioned rolling surface.

[0038] [Average GROD Value] In the above-mentioned EBSD measurement, the copper alloy sheet material of this embodiment has an average GROD value of 1 to 5°, assuming that boundaries (including twin boundaries) with a crystal orientation difference of 5° or more are considered to be grain boundaries. 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 shown that this average GROD value has a significant effect on the morphology of the outer peripheral surface of a bent portion. In order to stably obtain an appropriate surface morphology during severe bending at B.W., an average GROD value of 5° or less is extremely effective. 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 average GROD 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] [Method of determining the average GROD value] Based on the above EBSD measurement data measured on the LD plane with a step size (measurement pitch) of 0.1 μm, using EBSD data analysis software, boundaries with an orientation difference of 5° or more are considered to be grain boundaries (including twin boundaries), and the average orientation of the measurement spots within the same grain is taken as the reference orientation of that grain. The values ​​(°) of the orientation difference GROD (Grain Reference Orientation Deviation - Angle) between the spot and the reference orientation of the grain to which it belongs are calculated for all measurement spots in the measurement area, and the average of these values ​​is taken as the average GROD value (°).

[0040] [Average value of 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 be within a predetermined range, from the viewpoint of minimizing 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 a clue to determining the misorientation and deformation of a given crystal grain as a whole. To obtain an appropriate surface morphology during severe bending at 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 satisfies this requirement, if the average GROD value is not controlled within the above-mentioned specified range, an appropriate surface morphology cannot be stably achieved during severe bending at 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] [Method of determining the average GOS value] Based on the above EBSD measurement data measured on the LD plane at a step size (measurement pitch) of 0.1 μm, the average GOS (Grain Orientation Spread) value (°) is calculated by the Area Fraction method using EBSD data analysis software. For crystal grains whose parts extend beyond the boundary of the measurement region, the parts that exist within the measurement region are used as they are to calculate the GOS value.

[0043] [Maximum Deviation from an Ideal Smooth Curved Surface on the Outer Surface of the Bent Section] The copper alloy sheet material 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 profile of the ideal smooth curved surface on the outer surface of the bent section is small. Specifically, when the copper alloy sheet material is evaluated in a 90°W bending test at B.W. (described later) with a specimen width of 0.4 mm and an R / t of 0.25, the maximum deviation from the ideal smooth curved surface on the outer surface of the bent section 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 in 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, as 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 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 BW bending.

[0045] JCBA T307:2007 states, "This standard applies to the evaluation of the bending workability of copper and copper alloy thin sheet strips having a thickness of 0.1 mm or more and 0.8 mm or less." According to the inventors' investigations, it has been confirmed that the bending workability of Cu-Ni-Sn-P-based copper alloy sheets having a thickness of less than 0.1 mm can also be evaluated by a W-bend test conforming to this standard. Therefore, in this embodiment, the B.W. W-bend test method shown in JCBA T307:2007 is extended and applied as is to sheets having 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 tensile strength of the copper alloy sheet material of this embodiment in the direction parallel to the rolling direction (LD) is 400 MPa or more. The tensile strength is preferably 450 MPa or more. It is also possible to adjust the tensile strength in the rolling direction 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 The copper alloy sheet described above can be manufactured, for example, by the following manufacturing process. Specifically, the manufacturing method of the copper alloy sheet includes a melting / 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] The melting and casting process can be carried out according to a general copper alloy melting method. A cast piece having a predetermined chemical composition can be produced by continuous casting, semi-continuous casting, etc. For continuous casting, it is preferable to use a vertical or horizontal casting furnace.

[0050] [Cast Heating Step] The cast 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 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, because a large rolling load is required to achieve a reduction of 60% or more in a single 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): Reduction rate (%) = 100 × (t ０ -t １ ) / t ０ ... (1) t ０ t: Plate thickness before the rolling pass (mm) １ : Plate thickness (mm) at the end of the rolling pass The total rolling reduction (%) in a rolling process is determined by the following formula (2): Total rolling reduction (%) = 100 × (h ０ -h １ ) / h ０ …(2) h ０ h: Plate thickness (mm) before the first pass of the rolling process １ : Plate thickness (mm) at the end of the final rolling pass of the rolling process

[0053] [Rough Cold Rolling Step] 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 for intermediate annealing can be obtained.

[0054] [Intermediate annealing process] The intermediate product sheet material is subjected to intermediate annealing. In this intermediate annealing, recrystallization occurs using the strain introduced by rough cold rolling as a 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] The cold rolling performed on the material after 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 a total rolling reduction of 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). The 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) of 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) and integrating these values. Here, x is the distance traveled by copper during heat treatment, and D is the diffusion coefficient. The diffusion coefficient is 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 = D ０ exp(-Q / RT)...(4) where D ０ is 7.8 x 10 －５ [m ２ / s], Q was 211 [kJ / mol], and R (gas constant) was 8.314 [J / (mol·K)]. From the diffusion coefficient D obtained for each temperature, the copper movement distance per second at each temperature was calculated, and these were integrated to determine the copper movement distance (nm) during heat treatment. The copper movement distance during heat treatment is calculated by integrating the copper movement distance from the point when the material temperature reaches 100°C, until it is further heated to the maximum temperature, and after heating is completed (and held at the maximum temperature if necessary), until it is cooled and its temperature drops 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 conditions for recrystallization annealing are, for example, a furnace temperature of 550 to 750°C and a holding time of 10 to 1000 seconds, and the conditions can be set so that the copper movement distance during heat treatment is 10 to 150 nm.

[0060] [Finish cold rolling process] The cold rolling performed on the material after 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 above-mentioned EBSD measurement is refined, and it is necessary to control it so that it has a predetermined 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 ratio is set to 40% or more and 80% or less, the number of rolling passes with a reduction ratio of 20% or more is set to 0 or more and 3 or less, and the average unit tension (average value of each pass) is set to 250 N / mm ２ The unit tension is the tension (N) multiplied by the cross-sectional area of ​​the plate (plate width x plate thickness) (mm ２ From the viewpoint of achieving good bending workability, it is desirable that the total rolling ratio be 40% or more and 65% or less.

[0061] [Low-Temperature Annealing Step] In this embodiment, low-temperature annealing is finally performed to reduce distortion. The low-temperature annealing can be performed under conditions of, for example, holding at 350 to 450° C. for 10 to 600 seconds.

[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 that has 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 Current-carrying components, heat-dissipating components, and board-to-board connectors are formed by processes 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 meet this requirement.

[0064] (1) Manufacturing of Copper Alloy Sheet Material In this example, first, a copper alloy sheet material was manufactured.

[0065] (Example 1) Copper alloys having the chemical compositions shown in Table 1 were melted and cast. The resulting cast pieces (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 oxide layer on the surface was removed by mechanical polishing (surface grinding), 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 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). As a result, the 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 of Copper Alloy Sheet Materials Each of the obtained copper alloy sheets was evaluated by the following method.

[0070] (Average grain size) A cross section (LD surface) perpendicular to the rolling direction of a sample taken from the test material was processed with a cross-section polisher (IB-19530CP manufactured by JEOL Ltd.) at an acceleration voltage of 4 kV to prepare a sample surface for EBSD (electron backscatter diffraction) measurement. The sample surface was observed with an FE-SEM (JSM-7200F manufactured by JEOL Ltd.) at an acceleration voltage of 15 kV and a magnification of 2500 times. Crystal orientation data was collected at a step size of 0.1 μm by the EBSD method using an EBSD device (Symmetry manufactured by Oxford Instruments) installed in the FE-SEM for a rectangular measurement area of ​​48 μm in the plate width direction × 36 μm in the plate thickness direction, which was set within the range from the 1 / 4 position to the 3 / 4 position of the plate thickness. Based on the crystal orientation data measured in the measurement regions of five non-overlapping fields, the average grain size was calculated by the Area Fraction method according to the "Method for calculating average grain size" described above. 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 and GOS values ​​described below).

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

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

[0073] (Maximum deviation from an ideal smooth curved surface on the outer periphery of the bent portion) Test pieces measuring 30 mm in length and 0.4 mm in width were cut from the test material so that the longitudinal direction of the test piece coincided with the direction perpendicular to the rolling direction on the surface of the test material. A 90° W bending test was performed at B.W. with a ratio R / t of 0.25 (between the bend radius R (mm) and the plate thickness t (mm)) according to the method stipulated in the Japan Copper and Brass Association Technical Standard JCBA T307:2007. The outer peripheral surface of the bent portion formed on the test piece was observed using a laser microscope (Keyence Corporation, 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 piece. 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. A specific measurement method will be described 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, which is 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 irregular irregularities at depths of approximately 8 μm from the apex (highest point). Therefore, a polynomial approximation curve (quadratic function) was created using data from the measured profile curve within a depth range of 8 to 20 μm from the apex. Measurement position data (the horizontal axis in Figure 2) was 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 an ideal, smooth curved surface on the outer periphery of the bent section. The ideal profile is shown by a dashed line in Figure 2. It can be seen that the actual bent outer surface exhibits a surface morphology with a slight depression 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 measurement lines set at random 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 deviations of three test pieces were determined for the number of tests n = 3, and the average of the measured maximum deviation values ​​of the three test pieces was used as the performance value of the maximum deviation of the test material.

[0077] The maximum deviation was measured for the bending test piece 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-bend test) In addition to the evaluation of the maximum deviation, bending workability was evaluated as follows by a standard bending test. In accordance with the Japan Copper and Brass Association technical standard JCBA T307:2007, the ratio MBR / t of the minimum bending radius MBR at which cracks did not occur to the sheet thickness t was determined by a W-bend test at BW. 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 (the width of the test specimen). The presence or absence of cracks on the bent surface was determined in accordance with JCBA T307:2007. For samples judged to have "large wrinkles" in the appearance observation of the bent surface, a specimen was prepared by cutting the deepest wrinkle perpendicular to the bending axis direction, and the polished cross section was observed with an optical microscope to check for the presence of cracks propagating into the sheet thickness. If no such cracks were found, the specimen was judged to have "no cracks observed." Considering the applications of the material of the present invention, if the MBR / t obtained by this test is 0.5 or less, it is evaluated as having 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 strength was measured by conducting a tensile test in accordance with JIS Z2241 with the number of tests n = 3. The average value of n = 3 was used as the performance value of the test material.

[0080] (Electrical 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 above evaluation results are shown in Tables 7 to 9.

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[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 microstructural state in which the average crystal grain size and GROD average value were within the ranges specified in the present invention, and had the property that the maximum deviation from an ideal smooth curved surface of the outer periphery of the bent part (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, which were also good.

[0092] In contrast, in the copper alloy sheet of Comparative Example 1, the copper movement distance during heat treatment in recrystallization annealing was 176 nm, which was too large, so the crystal grain size was 5.8 μm, which exceeded 4 μm. As a result, the maximum deviation was large. In the copper alloy sheet of Comparative Example 2, the number of rolling passes with a reduction rate of 20% or more in finish rolling was large, so the average GROD value was 5.4°, which exceeded 5°, and as a result, the maximum deviation was large. In the copper alloy sheet of Comparative Example 3, the average unit tension in finish rolling was too large, so the average GROD value was 5.4°, which exceeded 5°, and as a result, the maximum deviation was large. In the copper alloy sheet of Comparative Example 4, the copper movement distance during heat treatment in recrystallization annealing was 3 nm, which was too small, so the crystal grain size was 0.9 μm, which was less than 1 μm. The average GROD value also increased to 6.3°, which exceeded 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, by 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 remainder being Cu (copper) and unavoidable impurities; A copper alloy sheet material having a tensile strength of 400 MPa or more, wherein, in a measurement of a measurement region provided on a cross section perpendicular to the rolling direction by an EBSD (electron backscatter diffraction) method with a step size of 0.1 μm, when a boundary with a crystal orientation difference of 5° or more is considered to be a crystal grain boundary, the average crystal grain size is 1 to 4 μm by the Area Fraction method, and when a boundary with a crystal orientation difference of 5° or more is considered to be a crystal grain boundary, when the average orientation of measurement spots within the same crystal grain is taken as the reference orientation of that crystal grain, the average value of GROD (Grain Reference Orientation Deviation - Angle) is calculated by finding the orientation difference between each measurement spot and the reference orientation of the crystal grain to which each measurement spot belongs for all measurement spots in the measurement region and calculating the average value, and wherein the tensile strength is 400 MPa or more.

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

3. The copper alloy sheet material according to claim 1 or 2, wherein the ratio MBR / t of the minimum bending radius MBR at which cracking does not occur to the 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 2, having an electrical conductivity of 30% IACS or more.

5. An electric component using the copper alloy sheet material according to claim 1 or 2 as its material.

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

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

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