JP7614824B2 - Cu-Ni-Si copper alloy sheet material, its manufacturing method, and current-carrying component - Google Patents

Description

The present invention relates to a Cu-Ni-Si copper alloy sheet material with improved etching properties, a manufacturing method thereof, and an electrically conductive part using the Cu-Ni-Si copper alloy sheet material.

Cu-Ni-Si copper alloys have a relatively good balance of strength and conductivity among copper alloys, and are useful for current-carrying parts such as connectors and lead frames, and for heat-dissipating parts in electronic devices. Traditionally, current-carrying parts and heat-dissipating parts were often made by press-punching sheet material. In recent years, as parts have become smaller and their shapes have become more complex, there has been an increasing need to create products using etching processes. To meet this demand, it is necessary to form parts with high shape accuracy using precision etching, and materials are required that can produce etched surfaces with as few surface irregularities as possible (good surface smoothness).

In Cu-Ni-Si copper alloys, several techniques have been proposed to improve the etching properties (for example, Patent Documents 1 to 3 described later). However, in recent years, semiconductor packages have become more multi-pin and narrower in pitch, and materials for lead frames are required to have etching properties that can handle pin intervals of about 300 μm or less. When the slit portion of the resist film is etched, etching proceeds not only in the depth direction but also in the width direction of the slit (the direction toward the bottom of the resist film), so the interval between the pins formed after etching is generally larger than the slit width of the resist film. When the pin width is large, the adverse effect on dimensional accuracy caused by the progression of etching in the slit width direction could be avoided by optimizing the size of the slit. However, in order to handle narrower pitches with pin intervals of about 300 μm, it is desirable to apply a copper alloy sheet material that has the property of being "easily etched in the depth direction and difficult to etch in the width direction of the slit". In this specification, the above characteristics are evaluated by introducing an index called "etching factor" as described later. The larger the etching factor, the better the above characteristics are evaluated to be. An example of calculating the etching factor based on the same etching conditions will be described later.

Patent Document 1 discloses a technique for manufacturing a plate material having a structure with a high KAM value and improving the smoothness of an etched surface by carrying out a process of solution treatment, intermediate cold rolling, aging treatment, finish cold rolling, shape correction by a tension leveler, and low-temperature annealing in a Cu-Ni-Si-based copper alloy. However, the elongation imparted by the tension leveler is lower than that of the method of the present invention described below, and the atmosphere for low-temperature annealing is not disclosed.
Patent Document 2 discloses a technique for producing a sheet material having a structure with a high concentration of brass orientation by carrying out a special solution treatment, which also serves as a precursor treatment for aging, an aging treatment, finish cold rolling, and low-temperature annealing in a Cu-Ni-Si-based copper alloy sheet material containing Co, and improving the smoothness of the etched surface. No process using a tension leveler is disclosed.
Patent Document 3 discloses a technique for improving surface irregularities and dimensional accuracy after etching by subjecting a Cu-Ni-Si based copper alloy to a crystal orientation with a bending density of 12 or less in all Euler angles through the steps of solution treatment, aging treatment, diffusion treatment at 220 to 280°C, cold rolling, and stress relief annealing. The technique does not disclose a step of using a tension leveller.

The techniques of Patent Documents 1 to 3 are effective in improving the smoothness of the etched surface, which is thought to improve the dimensional accuracy after etching. However, these techniques are unable to fully improve the above-mentioned etching factor. In other words, they are not fully satisfactory in terms of improving etching accuracy in light of the recent trend towards narrower pitches.

On the other hand, in order to improve the strength, electrical conductivity, bending workability, stress relaxation resistance, etc. of Cu-Ni-Si based copper alloys in a well-balanced manner, various techniques for controlling the texture of sheet materials have been investigated.
For example, Patent Document 4 discloses a technique for obtaining a structure state in which the average area ratio of Cube orientation is high and the KAM value is high by using a process of performing two solution treatments with cold rolling in between, but does not disclose a process using a tension leveler.
Patent Document 5 discloses a technique for adjusting a texture to have an average area ratio of Cube orientation {001}<100> of 20% or more and an average total area ratio of three orientations, Brass orientation {011}<211>, S orientation {123}<634>, and Copper orientation {112}<111> of 40% or less, by utilizing a process of performing a two-stage solution treatment. The technique does not disclose a process using a tension leveler.
Patent Document 6 discloses a technique for adjusting the texture to have a ratio of Cube orientation of 50% or more by performing two finish cold rolling processes with a final solution treatment in between. It does not disclose a process using a tension leveler.
The textures shown in these Patent Documents 4 to 6 cannot sufficiently improve the above etching factor.

JP2018-35437A JP 2018-62694 A JP 2018-168438 A JP 2012-177153 A JP 2011-52316 A JP 2006-152392 A

As mentioned above, various methods have been studied for controlling the texture of Cu-Ni-Si copper alloy sheet materials, and it has been proposed to improve the etching properties by doing so. However, with the recent trend toward narrower pitches in semiconductor packages, there are an increasing number of applications in which it is difficult to ensure sufficient etching accuracy with conventional Cu-Ni-Si copper alloy sheet materials.

The objective of the present invention is to provide a Cu-Ni-Si copper alloy sheet material that is excellent in the property of being easily etched in the depth direction and being difficult to etch in the width direction of the slit (i.e., having a large etching factor), which is advantageous in obtaining high dimensional accuracy even when etching with a very narrow pitch.

According to the inventors' investigations, the following was found.
(i) In order to identify a texture that can stably obtain a high etching factor, it is necessary to focus on the crystal orientation “inside” the sheet, not on the sheet surface (rolled surface), but on a cross section including the sheet thickness direction.
(ii) Regarding the crystal orientation inside the crystal grains, when the area of a region that satisfies at least one of the conditions that the crystal orientation difference from the S1 orientation {241}<112> is within 10° and the crystal orientation difference from the S2 orientation {231}<124> is within 10° is defined as S _S , and the area of a region that has a crystal orientation difference from the Brass orientation {011}<211> within 10° is defined as S _B , it is extremely effective to control the crystal orientation to one in which the area ratio S _B /S _S is 0.40 or more.
(iii) In order to obtain a more stable and high etching factor, it is effective to have a moderately high crystal lattice distortion with excellent uniformity. Specifically, it is preferable that the KAM value measured by EBSD under the condition of a minute step size of 0.05 μm is 2.00° or more.
(iv) In order to manufacture a plate material exhibiting the above-mentioned high etching factor, it is extremely effective to impart a deformation having an elongation rate of more than 1.5% and not more than 3.7% using a tension leveler after the final finish cold rolling, and to use a mixed gas atmosphere of hydrogen gas and an inert gas having a hydrogen concentration of 3 to 13 volume % for the low-temperature annealing.
The present invention was completed based on these findings.

This specification discloses the following inventions.
[1] In mass%, Ni: 1.00 to 4.50%, Si: 0.10 to 1.40%, Co: 0 to 2.00%, Mg: 0 to 0.50%, Cr: 0 to 0.50%, P: 0 to 0.20%, B: 0 to 0.20%, M n: 0-1.00%, Sn: 0-1.00%, Ti: 0-0.50%, Zr: 0-0.30%, Al: 0-1.00%, Fe: 0-1.00%, Zn: 0-1.00%, Ag: 0-0.30%, Be: 0 The copper alloy sheet has a chemical composition consisting of Cu 0.15% or less, the balance being Cu and unavoidable impurities, and in an EBSD (electron backscatter diffraction) measurement of a measurement region provided within a range from the 1/4 position to the 3/4 position of the sheet thickness on a cross section perpendicular to the rolling direction, the area ratio S B /S S is 0.40 or more, where S _S is the area of a region that satisfies at least one of the conditions that the crystal orientation difference from the S1 orientation {241}<112> is within 10° and the crystal orientation difference from the S2 orientation {231}<124> is within 10°, and S _B is the area of a region that has a crystal orientation difference from the _{Brass orientation} {011}<211> within 10°.
[2] The copper alloy sheet material according to the above [1], in which in the EBSD measurement, a KAM value measured with a step size of 0.05 μm within a crystal grain when a boundary having a crystal orientation difference of 15° or more is regarded as a crystal grain boundary is 2.00° or more.
[3] The copper alloy sheet material according to the above [1] or [2], wherein in the EBSD measurement, an average crystal grain size determined by an Area Fraction method in the case where a boundary having a crystal orientation difference of 15° or more is regarded as a crystal grain boundary is 2.00 μm or less.
[4] The copper alloy sheet material according to any one of the above [1] to [3], wherein the number density of fine second phase particles having a particle size of 20 to 30 nm present in the matrix (metal base) is 1.0 × ¹⁰⁷ particles/mm2 ^or more, and the number density of coarse second phase particles having a particle size of 0.5 μm or more is 5.0 × ¹⁰⁵ particles/mm2 or ^less .
[5] The copper alloy sheet material according to any one of [1] to [4] above, having a tensile strength of 600 MPa or more in a direction parallel to the rolling direction.
[6] The copper alloy sheet material according to any one of the above [1] to [5], wherein the Co content in the chemical composition is 0.50 to 2.00 mass%.
[7] The copper alloy sheet material according to any one of the above [1] to [6], having a sheet thickness of 0.04 to 0.30 mm.
[8] In a manufacturing process in which an intermediate product sheet material is subjected to solution treatment, intermediate cold rolling, aging treatment, finish cold rolling, tension leveler passing, and low-temperature annealing in the above order,
Solution treatment is performed at 780 to 1,060°C for 10 to 80 seconds.
When the reduction ratio of the intermediate cold rolling is R ₁ (%), the reduction ratio of the finish cold rolling is R ₂ (%), and the total reduction ratio of the intermediate cold rolling and the finish cold rolling is R _T (%), the intermediate cold rolling and the finish cold rolling are performed under conditions that satisfy at least one of the following cold rolling conditions A and B:
Aging treatment is performed before finish cold rolling under conditions that do not cause recrystallization.
The strip is passed through a tension leveller under the condition that the elongation rate is more than 1.5% and less than 3.7%.
Low-temperature annealing is performed in a mixed gas atmosphere of hydrogen gas and inert gas having a hydrogen concentration of 3 to 13 volume % at 380 to 550°C for 10 to 620 seconds.
The method for producing a copper alloy sheet material according to any one of [1] to [7] above.
(Cold rolling condition A) R ₁ ≧50%, R ₂ ≧25%, and R _T ≧75%
(Cold rolling condition B) R ₁ ≧60%, R ₂ ≧18%, and R _T ≧90%
[9] The method for producing a copper alloy sheet according to the above [8], wherein the intermediate product sheet is a sheet that has been subjected to hot rolling and then cold rolling.
[10] An electrical component using the copper alloy sheet material according to any one of [1] to [7] above.

This specification also discloses the following invention [1]', which further limits the chemical composition of the above [1]. The above inventions [2] to [10] may refer to the following [1]' instead of the above [1].
[1]'In mass%, Ni: 1.00 to 4.50%, Si: 0.10 to 1.20%, Co: 0 to 2.00%, Mg: 0 to 0.30%, Cr: 0 to 0.20%, P: 0 to 0.10%, B: 0 to 0.05 %, Mn: 0-0.20%, Sn: 0-1.00%, Ti: 0-0.50%, Zr: 0-0.20%, Al: 0-0.20%, Fe: 0-0.30%, Zn: 0-1.00%, Ag: 0-0.20 %, the balance Cu and unavoidable impurities, and in an EBSD (electron backscatter diffraction) measurement of a measurement region provided within a range from 1/4 to 3/4 of the sheet thickness position on a cross section perpendicular to the rolling direction, an area ratio S B /S S is 0.40 or more, where S _S is the area of a region that satisfies at least one of the conditions that the crystal orientation difference from the S1 orientation {241}<112> is within 10° and the crystal orientation difference from the S2 orientation {231}<124> is within 10°, and S _B is the area of a region that has a crystal orientation difference from _{the Brass} orientation {011}<211> within 10°.

In this specification, "plate material" refers to a sheet-like metal material. Thin sheet-like metal materials are sometimes called "foils," and such "foils" are also included in the "plate material" referred to here. Long sheet-like metal materials wound into a coil are also included in the "plate material." In addition, in this specification, the thickness of a sheet-like metal material is referred to as the "plate thickness."

Among the above alloy elements, Co, Mg, Cr, P, B, Mn, Sn, Ti, Zr, Al, Fe, Zn and Ag are optional elements. "1/4 sheet thickness position" means a position in the sheet thickness direction that is t/4 (mm) away from one rolling surface, where t is the sheet thickness (mm). Similarly, "3/4 sheet thickness position" means a position in the sheet thickness direction that is 3t/4 (mm) away from the above rolling surface.
The S _B , S _S , and KAM (Kernel Average Misorientation) values obtained by EBSD (Electron Backscatter Diffraction) can be determined as follows.

[How to calculate S _S and S _B using EBSD]
A cross section perpendicular to the rolling direction of the sheet material (referred to as the "LD surface") is observed by a FE-SEM (field emission scanning electron microscope), and the crystal orientation is measured by an EBSD (electron backscatter diffraction) method at a step size (measurement pitch) of 0.05 μm for a rectangular measurement area of 24 μm in the sheet width direction and 18 μm in the sheet thickness direction, which is provided within the range from the 1/4 position to the 3/4 position of the sheet thickness. Using EBSD data analysis software, a region in which the crystal orientation difference from the S1 orientation {241}<112> is within 10° (referred to as the "S1 region"), a region in which the crystal orientation difference from the S2 orientation {231}<124> is within 10° (referred to as the "S2 region"), and a region in which the crystal orientation difference from the Brass orientation {011}<211> is within 10° (referred to as the "Brass region") are respectively mapped within the measurement area.
The sum of the areas of the S1 and S2 regions minus the area of the overlapping portion of the S1 and S2 regions is defined as S _S. This S _S corresponds to "the area of a region that satisfies at least one of the conditions that the crystal orientation difference from the S1 orientation {241}<112> is within 10° and the crystal orientation difference from the S2 orientation {231}<124> is within 10°."
The area of the Brass region is designated as S _B.

[How to calculate KAM value]
From the above EBSD measurement data measured on the LD surface with a step size (measurement pitch) of 0.05 μm, the KAM value in the crystal grain is calculated when the boundary with an orientation difference of 15° or more is regarded as the crystal grain boundary. This KAM value corresponds to the average value of the crystal orientation difference between adjacent spots (hereinafter referred to as "adjacent spot orientation difference") measured for the electron beam irradiation spots arranged at a pitch of 0.05 μm, only the measurement values of the adjacent spot orientation difference that is less than 15° are extracted. In other words, the KAM value is an index representing the amount of lattice distortion in the crystal grain, and the larger this value, the larger the distortion of the crystal lattice is evaluated as the material. Here, the step size is as small as 0.05 μm, so that the distribution of the dislocation density can be grasped precisely.

[How to determine the average crystal grain size]
From the EBSD measurement data measured on the LD plane at a step size (measurement pitch) of 0.05 μm, boundaries (including twin boundaries) with an orientation difference of 15° or more are regarded as grain boundaries, and the grain sizes of all grains in the measurement region are obtained using a diameter chart, and the average value of the grain sizes is calculated by the area fraction method, and this value is regarded as the average grain size (μm). For grains partly protruding from the boundary of the measurement region, the area of the part existing within the measurement region is used as it is to calculate the average grain size.

[Method of determining the number density of fine second phase particles]
A sample taken from the plate material to be measured is observed with a TEM (transmission electron microscope), and the number of second phase particles with a particle diameter of 20 to 30 nm that can be confirmed in the observation field is counted. The observation fields are randomly selected, with no overlapping fields. The particle diameter is the diameter of the smallest circle that surrounds the particle. The total number of second phase particles with a particle diameter of 20 to 30 nm counted divided by the total area of the observation region (pieces/ ^mm2 ) is the number density of fine second phase particles.

[Method of determining the number density of coarse second phase particles]
The plate surface (rolled surface) is electrolytically polished to dissolve only the Cu base to prepare an observation surface exposing second phase particles, and the observation surface is observed by SEM. The total number of second phase particles with a major axis of 2.0 μm or more observed in the SEM image is divided by the total observation area ( ^mm2 ) to obtain the coarse second phase particle number density (particles/ ^mm2 ). However, the total observation area must be 0.01 mm2 ^{or more} in total for multiple randomly set non-overlapping observation fields. Second phase particles that extend outside the observation field are counted if the major axis of the portion appearing within the observation field is 2.0 μm or more.

The rolling ratio from a certain plate thickness t ₀ (mm) to a certain plate thickness t ₁ (mm) is determined by the following formula (1).
Rolling ratio (%) = (t ₀ - _{t 1} )/t ₀ ×100...(1)

According to the present invention, it is now possible to provide a thin sheet material of Cu-Ni-Si copper alloy that has excellent properties of being easily etched in the depth direction, but not easily etched in the width direction of the slit. This makes it possible to realize current-carrying components with high etching accuracy for application to semiconductor packages with very narrow pitches, using Cu-Ni-Si copper alloy, which has a good balance of properties such as strength, conductivity, and bending workability.

FIG. 2 is a schematic diagram showing a cross section of a copper alloy sheet and a resist film formed on the rolled surface thereof at a stage prior to an etching experiment. FIG. 2 is a schematic diagram showing a cross section of a copper alloy sheet material and a resist film formed on the rolled surface thereof at a stage after an etching experiment. FIG. 3 is a schematic diagram showing a cross section of a copper alloy sheet and a resist film formed on its rolled surface at a stage after an etching experiment for a copper alloy sheet having an improved etching factor compared to that in FIG. 2 . An example of an optical microscope photograph of a cross section observed after an etching experiment.

[Etching factor]
In this specification, the "etching factor" is introduced as an index for evaluating the "characteristic of being easily etched in the depth direction and being difficult to etch in the width direction of the slit". The etching factor of a copper alloy sheet material can be obtained by forming a slit pattern of a predetermined shape with a photoresist film on one rolled surface of the copper alloy sheet material and performing an experiment in which etching is performed under predetermined conditions from the surface on which the slit pattern is formed. The concept of the etching factor is explained using Figures 1 to 3.

Figure 1 shows a schematic cross-section of a copper alloy sheet and a resist film formed on its rolled surface prior to an etching experiment. A portion of the rolled surface 10 of the copper alloy sheet 1 is masked by a resist film 2, and a slit 3 is formed in the exposed portion of the rolled surface 10. This figure corresponds to a cross-section perpendicular to the length of the slit. The thickness of the resist film is exaggerated. W1 is the resist film opening width equivalent to the slit width. In the examples described below, a slit pattern with a length of 70 mm and a width W1 of 280 μm was formed so that the length of the slit was in the rolling direction.

FIG. 2 is a schematic diagram showing a cross section of a copper alloy sheet material and a resist film formed on the rolled surface thereof at a stage after an etching experiment. Etching is terminated before the etching erosion penetrates the sheet thickness. d is the etching depth. The etching experiment is performed by adjusting the etching time under the same etching conditions so that a groove of a predetermined etching depth is formed. In the examples described later, the etching experiment was performed under conditions in which the etching depth d is 60 μm. Etching proceeds from the portion of the slit 3 that is not masked by the resist film 2, and the etching is terminated in a state in which the etching depth d is reached in the sheet thickness direction. However, as the etching proceeds, erosion also occurs in the width direction of the slit, and as a result, the groove width after etching is larger than the resist film opening width W1. Usually, in the groove obtained in this etching experiment, the wall-to-wall distance of the groove measured in the width direction of the slit is longest at or near the opening directly under the resist film. The groove width after etching represented by this longest wall-to-wall distance is called the "etching width" and is indicated by the symbol W2 in the figure. The amount of erosion in the slit width direction is called the "side etch length" and is represented by the symbol L. The side etch length L is defined by the following formula (2).
L=(W2-W1)/2...(2)
Where:
L: Side etch length (μm)
W1: Resist film opening width (μm)
W2: Etching width (μm)
Normally, the amount of erosion in the slit width direction on both sides of the groove is almost uniform, so the side etch length L can be regarded as the amount of erosion in the slit width direction per one edge of the groove. In the figure, the amount of erosion in the slit width direction on both sides of the slit 3 is indicated as L.

Since the side etch length L increases with the etching time, an index that expresses the relationship between the etching depth d and the side etch length L is required to evaluate the "characteristic of the material being easily etched in the depth direction and not easily etched in the width direction of the slit." This is the etching factor. In this specification, the etching factor Ef is defined by the following formula (3).
Ef=d/L...(3)
Where:
Ef: Etching factor d: Etching depth (μm)
L: Side etch length (μm)

Figure 3 is a schematic diagram showing the cross section of a copper alloy sheet material and a resist film formed on its rolled surface at the stage after the etching experiment for a copper alloy sheet material with an improved etching factor compared to the case of Figure 2. Compared to Figure 2, the etching depth d is the same, but the side etch length L is shorter. Therefore, the etching factor Ef determined by formula (3) is larger. In this case, when etching is advanced until the plate thickness is penetrated to form the pin, excessive erosion in the width direction of the pin is suppressed, and etching processing that is more faithful to the masking pattern by the photoresist film is possible. In particular, when performing precision etching with a small pin width, applying a material with a large etching factor Ef is extremely effective in achieving high dimensional accuracy after etching. According to the present invention, the effect of improving the etching factor Ef can be obtained.

[Chemical composition]
In the present invention, a Cu-Ni-Si based copper alloy is used. Hereinafter, "%" regarding the alloy components means "mass %" unless otherwise specified.

Ni forms Ni-Si precipitates. When Co is contained as an additive element, Ni-Co-Si precipitates are formed. These precipitates improve the strength and electrical conductivity of the copper alloy sheet. Ni-Si precipitates are considered to be compounds mainly composed of Ni ₂ Si, and Ni-Co-Si precipitates are considered to be compounds mainly composed of (Ni,Co) ₂ Si. These compounds correspond to the "second phase" as referred to in this specification. In order to sufficiently disperse fine precipitate particles that are effective in improving strength, the Ni content must be 1.0% or more, and is more preferably 1.5% or more. On the other hand, if Ni is excessive, coarse precipitates are likely to be formed and the sheet is likely to crack during hot rolling. The Ni content is limited to 4.5% or less. It may be controlled to less than 4.0%.

Si forms Ni-Si precipitates. When Co is added, Ni-Co-Si precipitates are formed. In order to sufficiently disperse fine precipitate particles, which are effective in improving strength, the Si content must be 0.1% or more, and 0.4% or more is more preferable. On the other hand, excessive Si tends to form coarse precipitates, making the material prone to cracking during hot rolling. The Si content is limited to 1.4% or less, and may be controlled to 1.2% or less, or even less than 1.0%.

Co forms Ni-Co-Si precipitates and improves the strength and electrical conductivity of copper alloy sheets, so it can be added as needed. In order to thoroughly disperse fine precipitates, which are effective in improving strength, it is more effective to have a Co content of 0.5% or more. However, since a high Co content tends to produce coarse precipitates, if Co is added, it should be kept to a range of 2.0% or less. It may also be controlled to less than 1.5%.

Other elements such as Mg, Cr, P, B, Mn, Sn, Ti, Zr, Al, Fe, Zn, Ag, and Be may be contained as necessary. The content ranges of these elements are preferably as follows: Mg: 0-0.50%, Cr: 0-0.50%, P: 0-0.20%, B: 0-0.20%, Mn: 0-1.00%, Sn: 0-1.00%, Ti: 0-0.50%, Zr: 0-0.30%, Al: 0-1.00%, Fe: 0-1.00%, Zn: 0-1.00%, Ag: 0-0.30%, and Be: 0-0.15%.
In particular, the content ranges of Mg, Cr, P, B, Mn, Zr, Al, and Fe may be limited to the following, respectively: Mg: 0-0.30%, Cr: 0-0.20%, P: 0-0.10%, B: 0-0.05%, Mn: 0-0.20%, Zr: 0-0.20%, Al: 0-0.20%, Fe: 0-0.30%, and Ag: 0-0.20%.

Cr, P, B, Mn, Ti, Zr, and Al have the effect of further increasing the alloy strength and reducing stress relaxation. Sn, Mg, and Ag are effective in improving stress relaxation resistance. Zn improves the solderability and castability of copper alloy sheet materials. Fe, Cr, Zr, Ti, and Mn are likely to form high-melting point compounds with S and Pb, which are present as unavoidable impurities, and B, P, Zr, and Ti have the effect of refining the cast structure, which can contribute to improving hot workability.

When adding one or more of Mg, Cr, P, B, Mn, Sn, Ti, Zr, Al, Fe, Zn, and Ag, it is more effective to set the total content to 0.01% or more. However, adding a large amount will adversely affect hot or cold workability and will be disadvantageous in terms of cost. It is more preferable to keep the total amount of these optional added elements to 1.0% or less, and even more preferable to keep it to 0.5% or less.

[Crystalline Orientation]
In the present invention, a crystal orientation that acts to improve the above-mentioned etching factor is specified. The etching factor is a parameter that reflects the anisotropy of erosion inside the plate. Therefore, the distribution of crystal orientations in a cross section parallel to the plate thickness direction is important for improving the etching factor. The inventors investigated the distribution of crystal orientations in a cross section parallel to the plate thickness direction and studied in detail the relationship with the etching factor. As a result, it was found that it is extremely effective to determine a crystal orientation such that the area ratio S B /S _S is 0.40 or more when the area of the region that satisfies at least one of the conditions that the crystal orientation difference from the S1 orientation {241}<112> is within 10° and the crystal orientation difference from the S2 orientation {231}<124> is within 10° in EBSD (electron backscatter diffraction) measurement of a measurement region provided within the range from the _1/4 position to the 3/4 position of the sheet thickness is S _S , and the area of the region that has a crystal orientation difference from the Brass orientation {011}<211> is S _B . S _B and S _S can be determined according to the above-mentioned "Method of determining S _S and S _B by EBSD".

In the thin plate material of Cu-Ni-Si copper alloy, the crystal orientation in which the Brass orientation is predominant is said to be advantageous in improving the press punching property and the smoothness of the etched surface. However, this alone does not provide a means for improving the etching factor. By making the above-mentioned area ratio S _B /S _S on the LD surface including the plate thickness direction 0.40 or more, the etching factor can be improved. The area ratio S _B /S _S is more preferably 0.50 or more, more preferably 0.65 or more, or even more preferably 0.70 or more. There is no particular upper limit for _{S B} /S _S , but it is sufficient to adjust it to a range of, for example, 0.95 or less.

[KAM value]
It was found that in order to obtain a high etching factor, it is also advantageous to have a large KAM value based on fine EBSD measurement data with a small step size of 0.05 μm. Specifically, it is effective that the KAM value measured with a step size of 0.05 μm in the crystal grain is 2.00° or more when the boundary with a crystal orientation difference of 15° or more is regarded as the crystal grain boundary. The KAM value is a parameter that correlates with the dislocation density in the crystal grain. When the KAM value is large, it is considered that the average dislocation density in the crystal grain is high. Regarding etching, it is generally considered that the area with high dislocation density is preferentially etched (corroded). When the KAM value is large with a small step size of 0.05 μm, it is considered that the structure state has very few areas with low dislocation density locally. It is speculated that this is the cause of the high etching factor. The KAM value with a step size of 0.05 μm can be obtained according to the above-mentioned "How to obtain the KAM value". It is more preferable that this KAM value is 2.20° or more, and even more preferable that it is 2.40° or more. Although the upper limit of the KAM value is not particularly specified, it is sufficient to adjust it within a range of, for example, 3.00° or less. Note that, with conventional general EBSD measurement data in which the step size is large, for example, 0.2 μm or more, it has not been possible to fully grasp the effect of the KAM value on the etching factor.

[Average crystal grain size]
A small average crystal grain size is also advantageous in obtaining a high etching factor. Here, the average crystal grain size by the Area Fraction method can be adopted in the EBSD measurement of the LD surface, where the boundary (including the twin boundary) with a crystal orientation difference of 15° or more is regarded as the crystal grain boundary. For example, the data of the EBSD measurement according to the above-mentioned "Method of Determining S _S and S _B by EBSD" can be used. In that case, for crystal grains whose part protrudes from the boundary of the measurement area, the area of the part existing within the measurement area can be used as it is to calculate the average crystal grain size. The average crystal grain size by the Area Fraction method is preferably 2.00 μm or less, more preferably 1.80 μm or less, and further preferably 1.50 μm or less. The lower limit of the average crystal grain size is not particularly specified, but it is sufficient to adjust it to a range of, for example, 0.60 μm or more.

[Fine second phase particles]
In copper alloys, fine precipitates with a particle size of about 2 to 30 nm are generally considered to contribute to improving the strength. According to the research of the inventors, in the case of the Cu-Ni-Si-based copper alloy targeted in the present invention, it was found that among the fine precipitates as described above, securing a sufficient amount of those with a particle size in the range of 20 to 30 nm is also effective in improving the etching factor. As a result of various studies, in order to stably obtain a particularly excellent etching factor, it is advantageous to set the number density of fine second phase particles with a particle size of 20 to 30 nm to 1.0×10 ⁷ particles/mm ² or more, and it may be 3.0×10 ⁷ particles/mm ² or more. The upper limit of the number density of fine second phase particles is limited by the content of Ni, Si, and Co as described above, so there is no need to specify it in particular, but it is usually in the range of 10.0×10 ⁷ particles/mm ² or less.

[Coarse second phase particles]
Coarse second-phase particles do not contribute to strengthening. In addition, they can be a cause of reduced bending workability and smut generation. As a result of various investigations, when emphasis is placed on bending workability and suppression of smut generation, it is advantageous to have a structure in which the number density of coarse second-phase particles having a particle size of 0.5 μm or more is 5.0 × ¹⁰⁵ particles/mm2 or ^less .

[Tensile strength/conductivity]
It is desirable for a material for current-carrying parts manufactured by precision etching of a thin plate material to have a strength level of 600 MPa or more in the rolling direction and a conductivity of 28% IACS or more. If the above-mentioned chemical composition is satisfied, a plate material having a tensile strength of 600 MPa or more and a conductivity of 28% IACS or more can be obtained by the manufacturing method described below. The tensile strength can be adjusted to a strength level of 750 MPa or more, 800 MPa or more, 900 MPa or more, or even 1000 MPa or more. The conductivity can be adjusted to 30% IACS or more, 35% IACS or more, 40% IACS or more, or even 50% IACS or more.

[Production method]
The copper alloy sheet material described above can be produced, for example, by the following manufacturing process.
Melting/casting → hot rolling → cold rolling → (intermediate annealing → cold rolling) → solution treatment → intermediate cold rolling → aging treatment → finish cold rolling → passing through a tension leveler → low-temperature annealing Although not mentioned in the above steps, facing is performed as necessary after hot rolling, and pickling, polishing, or further degreasing is performed as necessary after each heat treatment. Each step will be explained below.

[Melting and Casting]
The cast pieces may be produced by continuous casting, semi-continuous casting, etc. To prevent oxidation of silicon and the like, it is preferable to carry out the casting in an inert gas atmosphere or in a vacuum melting furnace.

[Hot rolling]
Hot rolling may be performed according to a conventional method. The slab may be heated to 900 to 1000°C before hot rolling, for example, and held for 1 to 5 hours. The total hot rolling reduction may be, for example, 70 to 97%. The rolling temperature of the final pass is preferably 700°C or higher. After completion of hot rolling, it is preferable to rapidly cool the slab by water cooling or the like.

[Cold rolling]
The steel sheet is cold-rolled in a conventional manner to obtain an intermediate product sheet material for the next step of solution treatment. If necessary, intermediate annealing and cold rolling may be performed once or more to adjust the thickness of the steel sheet material.

[Solution treatment]
The solution treatment is preferably performed under conditions of holding at 780 to 1060°C for 10 to 80 seconds. If the heating temperature is too low or the holding time is too short, the solution treatment is insufficient and ultimately a satisfactory high strength cannot be obtained. If the heating temperature is too high or the holding time is too long, the area ratio of the Brass orientation is likely to ultimately be low, making it difficult to adjust the above-mentioned area ratio S _B /S _S to a predetermined value or higher. The cooling rate may be as rapid as can be realized in a general continuous annealing line. For example, it is desirable to set the average cooling rate from 530°C to 300°C to 100°C/s or more.

[Intermediate cold rolling]
Cold rolling before aging treatment is intended to reduce the plate thickness and introduce strain energy (dislocations). Cold rolling at this stage is referred to as "intermediate cold rolling" in this specification. Applying aging treatment to the plate material in which strain energy has been introduced is effective in improving the etching factor of the final product. In order to fully exert this effect, it is preferable to set the rolling ratio in the intermediate cold rolling to 50% or more, and it may be controlled to 60% or more. However, if the plate thickness is reduced excessively at this stage, it may be difficult to ensure the rolling ratio required in the finish cold rolling described below. Therefore, it is preferable to set the rolling ratio in the intermediate cold rolling to, for example, 95% or less depending on the final plate thickness.

[Aging treatment]
Next, aging treatment is performed to precipitate fine second phase particles that contribute to strength and are effective in improving the etching factor. The aging treatment conditions may be set according to the required properties within the condition range of an aging temperature of 430 to 550°C and a holding time in that temperature range of 3 to 10 hours. However, if recrystallization occurs, it becomes difficult to obtain the above-mentioned crystal orientation with a high S _B /S _S ratio, so it is necessary to perform the aging treatment under conditions that do not cause recrystallization within the above-mentioned temperature range and holding time range.

[Finish cold rolling]
The final cold rolling performed after the aging treatment is referred to as "finish cold rolling" in this specification. In order to obtain a crystal orientation with a high S _B /S _S ratio as described above, it is important to ensure a sufficient total cold rolling reduction ratio applied after the final process in which recrystallization occurs. In the manufacturing direction disclosed in this specification, the final heat treatment performed under conditions in which recrystallization occurs is the above-mentioned solution treatment. Therefore, the final required cold rolling reduction ratio is obtained by intermediate cold rolling and finish cold rolling. The inventors have investigated the relationship between the individual rolling reduction ratios of intermediate cold rolling and finish cold rolling, the total cold rolling reduction ratio of both, and the final crystal orientation obtained through numerous laboratory experiments. As a result, it was found that when the rolling reduction ratio in intermediate cold rolling is 60% or more and the rolling reduction ratio in finish cold rolling performed after aging treatment is 18% or more, it is possible to finally obtain a desired crystal orientation by setting the total cold rolling reduction ratio of both to 90% or more. In addition, it was found that if the reduction ratio in the intermediate cold rolling is 50% or more and the reduction ratio in the finish cold rolling performed after the aging treatment is 25% or more, the lower limit of the total cold rolling reduction ratio required for both is relaxed to 75%. The reason for this is unclear, but it is thought that the contribution of the cold rolling strain introduction on the texture is slightly different before and after the aging treatment. If the reduction ratio in the finish cold rolling is too high, the strength is likely to decrease during low-temperature annealing, so it is preferable to set the reduction ratio of the finish cold rolling to 85% or less. The final plate thickness may be set in the range of 0.04 to 0.30 mm, for example. It may also be controlled in the range of 0.06 to 0.30 mm.

In summary, the finish cold rolling may be performed under conditions that satisfy at least one of the following cold rolling conditions A and B.
(Cold rolling condition A) R ₁ ≧50%, R ₂ ≧25%, and R _T ≧75%
(Cold rolling condition B) R ₁ ≧60%, R ₂ ≧18%, and R _T ≧90%
Here, R ₁ is the rolling ratio (%) of intermediate cold rolling, R ₂ is the rolling ratio (%) of finish cold rolling, and R _T is the total rolling ratio (%) of intermediate cold rolling and finish cold rolling.
The rolling ratio is determined by the above formula (1).
For example, when the sheet thickness after solution treatment is 0.45 mm, the sheet thickness after intermediate rolling is 0.15 mm, and the sheet thickness after finish cold rolling is 0.08 mm,
Reduction ratio of intermediate cold rolling R ₁ =(0.45-0.15)/0.45×100≒66.7%,
Reduction ratio of finish cold rolling _R2 = (0.15 - 0.08) / 0.15 x 100 ≒ 46.7%,
Total rolling ratio R _T =(0.45-0.08)/0.45×100≒82.2%,
Thus, the cold rolling condition A is satisfied.

[Tension leveler threading]
The inventors have found that, in order to obtain a crystal orientation with a high S _B /S _S ratio, it is extremely effective to apply a relatively large deformation to a sheet material that has been subjected to finish cold rolling using a tension leveler before the final low-temperature annealing. A tension leveler is a device that bends and stretches a sheet material using multiple rolls while applying tension in the rolling direction. It is usually used for the purpose of correcting defective shapes of sheets caused by cold rolling or the like, and the amount of deformation applied at that time is often in the range of 0.1 to 1.5% in terms of elongation. In the case of thin sheets of Cu-Ni-Si-based copper alloys, if the sheet is passed through a tension leveler at an elongation rate of more than 1.5%, the effect of shape correction may not be stable, so shape correction at an elongation rate higher than that is usually not performed. However, it has been found that if a deformation with an elongation rate of more than 1.5% is applied by a tension leveler before the low-temperature annealing, a crystal orientation with a high S _B /S _S ratio can be obtained. In addition, since the shape (particularly flatness) of the final sheet material depends on the combination of the finish cold rolling conditions, the tension leveller passing conditions, and the low-temperature annealing conditions, it has been confirmed that it is fully possible to obtain a good sheet shape even when the sheet is passed through the tension leveller at a large elongation rate of more than 1.5%. As for the elongation rate imparted by the tension leveller, experiments have been repeated up to about 3.7% at present, and good effects have been obtained. Therefore, in the present invention, the elongation rate of the sheet passed through the tension leveller is specified to be in the range of more than 1.5% to 3.7%.

[Low temperature annealing]
Cold-rolled Cu-Ni-Si-based copper alloys that have been subjected to finish cold rolling are usually subjected to low-temperature annealing for the purpose of reducing residual stress, improving bending workability, and improving stress relaxation resistance by reducing voids and dislocations on slip planes. Generally, low-temperature annealing of copper alloys is performed in a mixed atmosphere of hydrogen and inert gas with a hydrogen concentration of 15% by volume or more to prevent oxidation. Low-temperature annealing is also performed in the present invention. However, it has been found that the low-temperature annealing atmosphere needs to have a low hydrogen concentration in order to stably obtain the above-mentioned crystal orientation with a high S _{B /} S S ratio. The reason for this has not been elucidated. Specifically, good results can be obtained by performing low-temperature annealing in a mixed gas atmosphere of hydrogen gas and inert gas with a hydrogen concentration of 3 to 13% by volume at 380 to 550° C. for 10 to 620 seconds.

Copper alloys with the chemical composition shown in Table 1 were melted and cast using a vertical semi-continuous casting machine. The resulting cast pieces were heated at 1000°C for 3 hours, extracted, hot rolled to a thickness of 14 mm, and water-cooled. The total hot rolling reduction was 90-95%. After hot rolling, the surface oxide layer was removed by mechanical polishing (face milling), and cold rolling was performed to obtain intermediate product sheets for solution treatment. Each intermediate product sheet was subjected to solution treatment, intermediate cold rolling, aging treatment, finish cold rolling, tension leveler passing, and low-temperature annealing under the conditions shown in Table 2 to obtain sheet products (test materials) with a thickness of 0.08 mm. In some comparative examples (No. 31), the sheets that were face milled after hot rolling were cold rolled to 90% and then subjected to solution treatment as intermediate product sheets, and intermediate cold rolling was omitted. Low-temperature annealing was performed in a continuous annealing furnace that can control the atmosphere inside the furnace. The atmospheric gas for low-temperature annealing was a mixture of hydrogen and nitrogen. Table 2 shows the hydrogen concentration (volume percent) in the low-temperature annealing atmosphere, with the remaining component being nitrogen.

The following investigations were carried out on each test material:

[S _B /S _S ratio based on crystal orientation data]
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 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 5000 times, and the crystal orientation was measured at a step size of 0.05 μm by the EBSD (electron backscatter diffraction) method using an EBSD device (Symmetry manufactured by Oxford Instruments) installed in the FE-SEM according to the above-mentioned "Method of determining S _S and S _B by EBSD". Based on the crystal orientation data, the area S _S of the region satisfying at least one of the conditions that the crystal orientation difference from the S1 orientation {241} <112> is within 10° and the crystal orientation difference from the S2 orientation {231} <124> is within 10°, and the area S _B of the region in which the crystal orientation difference from the Brass orientation {011} <211> is within 10° were obtained. Three LD plane observation samples were prepared for one test material, and the above S _S and S _B were measured for the visual field randomly selected within the range from the 1/4 position to the 3/4 position of the sheet thickness of the LD plane, to calculate the area ratio S _B /S _S , and the average value of the S _B /S _S values of the three samples was adopted as the S _B /S _S ratio of the test material. As the EBSD data analysis software, OIM-Analysis 7.3.1 manufactured by TSL Solutions Co., Ltd. was used.

[KAM value]
Based on the crystal orientation data of the EBSD measurement of the LD plane (measured with a step size of 0.05 μm), the KAM value was calculated according to the above-mentioned "How to calculate the KAM value". The average value of the KAM values of the three samples was adopted as the KAM value of the test material.

[Average crystal grain size]
Based on the crystal orientation data of the EBSD measurement of the LD plane (measured with a step size of 0.05 μm), the average crystal grain size was calculated according to the above-mentioned "Method of calculating average crystal grain size". The arithmetic mean value of the average crystal grain size values of the three samples was adopted as the average crystal grain size of the test material.
The cleanup process was performed only once with a grain dilation angle of 5° and a minimum crystal grain size of 2 pixels.

[Number density of fine second phase particles]
The number density of the fine second phase particles was determined according to the above-mentioned "Method of determining the number density of fine second phase particles". Specifically, a disk having a diameter of 3 mm was punched out from the test material, a TEM observation sample was prepared by a twin jet polishing method, and photographs were taken of 10 randomly selected fields of view at a magnification of 100,000 times with an acceleration voltage of 200 kV using a TEM (EM-2010 manufactured by JEOL Ltd.), and the number of fine second phase particles having a particle diameter of 20 to 30 nm was counted on the photographs. Here, the size of one field of view was set to 770 nm x 550 nm. The particle diameter was taken as the diameter of the smallest circle surrounding the particle.

[Number density of coarse second phase particles]
The number density of the second phase particles was determined according to the above-mentioned "Method for determining the number density of coarse second phase particles". A solution in which distilled water, phosphoric acid, ethanol, and 2-propanol were mixed in a ratio of 2:1:1:1 was used as the electropolishing solution for preparing the observation surface. The electropolishing was performed using an electropolishing device (ELECTROPOLISHER POWER SUPPLUY, ELECTROPOLISHER CELL MODULE) manufactured by BUEHLER under the conditions of a voltage of 15 V and a time of 20 seconds.

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

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

[Etching factor]
A slit (part not masked by the resist film) of 70 mm in the rolling direction and 280 μm in the direction perpendicular to the rolling direction was formed on the rolled surface of a plate sample taken from a test material with a plate thickness of 0.08 mm (80 μm) by a photoresist method. An aqueous solution of ferric chloride 42 Baume was prepared as an etching solution. The copper alloy plate was etched from the slit portion by a method in which the etching solution at 50° C. was evenly sprayed on the slit, and a groove was formed so that the etching depth d (see FIG. 2) was about 60 to 70 μm. The etching time was about 150 seconds. The sample after etching was embedded in resin to prepare a cross section perpendicular to the length direction of the slit, and the etching depth d and etching width W2 (see FIG. 2) were measured using a laser microscope (Olympus, OLS-4000). Using these values, the side etch length L was calculated by the following formula (2), and the etching factor Ef was obtained by the following formula (3).
L=(W2-W1)/2...(2)
Ef=d/L...(3)
Here, W1 is the resist film opening width, and a value of 280 μm is substituted therefor.
The cross-sections were observed in 10 visual fields, and the arithmetic mean of the etching factor Ef values obtained in each visual field, excluding the maximum and minimum values, was calculated and used as the etching factor value of the test material.
For reference, Fig. 4 shows an optical microscope photograph (taken by the above-mentioned laser microscope) of the observed cross section after the etching experiment. This is an example of No. 3. The part indicated by reference numeral 101 is the plate material sample (specimen). In this example, the etching depth d is 67.8 µm, the etching width W2 is 290.1 µm, and the etching factor Ef is 13.4.

Under these experimental conditions, it is judged that an etching factor value of 10.0 or more is an improved effect in etching factor compared to conventional Cu-Ni-Si based copper alloy sheet materials. Therefore, the etching factor value of 10.0 or more was further classified into ranks, and the etching factor was evaluated according to the following 5 levels.
××: Less than 10.0 (conventional level)
x: 10.0 or more and less than 11.0 △: 11.0 or more and less than 12.0 ○: 12.0 or more and less than 13.0 ◎: 13.0 or more Materials with a high improvement effect compared to conventional materials and above were judged to be acceptable. The order of evaluation is x<△<○<◎, with increasing "characteristics of being easily etched in the depth direction and being difficult to etch in the width direction of the slit".
The results are shown in Table 3.

All of the inventive examples, in which the chemical composition and manufacturing conditions were strictly controlled in accordance with the above-mentioned regulations, had a crystal orientation with a high S _B /S _S ratio, and an excellent improvement effect in the etching factor was observed. In particular, those (Nos. 1 to 4, 6 to 13) in which the KAM value of the LD surface measured at a step size of 0.05 μm was 2.00° or more, the average crystal grain size measured by the above-mentioned Area Fraction method was 2.00 μm or less, and the number density of fine second phase particles with a grain size of 20 to 30 nm was 1.0 × 10 ⁷ pieces/mm ² or more were evaluated as having an excellent etching factor of ○ or more. It can also be seen that by increasing the above-mentioned KAM value to 2.20° or more, a more stable and excellent improvement effect in the etching factor can be obtained.

In contrast, all of the comparative examples had a low S _B /S _S ratio, and no improvement in the etching factor was observed. The causes of this include omission of intermediate cold rolling in No. 31, too low a finish cold rolling reduction in No. 32 and 43, too high a solution treatment temperature in No. 33, too long a solution treatment time in No. 34, recrystallization due to high temperature and long aging treatment conditions in No. 35, too low an elongation rate of the tension leveler in No. 36 and 37, too high a low-temperature annealing temperature in No. 38, too long a low-temperature annealing time in No. 39, too high a hydrogen concentration in the low-temperature annealing atmosphere gas in No. 40, too low a content of Ni and Si in the alloy composition in No. 41, and too high a content of Ni in the alloy composition in No. 42. The etching factors of these comparative examples were all rated as XX, and none of them were rated as x.

REFERENCE SIGNS LIST 1 Copper alloy sheet material 2 Resist film 3 Slit 10 Rolled surface 101 Sheet material sample (specimen)

Claims (10)

In mass%, Ni: 1.00 to 4.50%, Si: 0.10 to 1.40%, Co: 0 to 2.00%, Mg: 0 to 0.50%, Cr: 0 to 0. 50%, P: 0-0.20%, B: 0-0.20%, Mn: 0-1.00%, Sn: 0-1.00%, Ti: 0-0.50%, Zr: 0-0.30%, Al: 0-1.00%, Fe: 0-1.00 %, Zn: 0-1.00%, Ag: 0-0.30%, Be: 0- The EBSD analysis was performed on a measurement area in the range from 1/4 to 3/4 of the sheet thickness on a cross section perpendicular to the rolling direction. In the electron backscatter diffraction method, at least one of the following is found: the crystal orientation difference from the S1 orientation {241}<112> is within 10°; and the crystal orientation difference from the S2 orientation {231}<124> is within 10°. If the area of the region satisfying the conditions is S _S , and the area of the region whose crystal orientation deviation from the Brass orientation {011}<211> is within 10° is S _B , the area ratio S _B /S _S is 0.40. The copper alloy sheet material is as described above. The copper alloy sheet material according to claim 1, in which the KAM value measured in the EBSD measurement with a step size of 0.05 μm within the grains when a boundary with a crystal orientation difference of 15° or more is regarded as a grain boundary is 2.00° or more. The copper alloy sheet material according to claim 1 or 2, in which the average grain size determined by the Area Fraction method when the boundaries with a crystal orientation difference of 15° or more are regarded as grain boundaries in the EBSD measurement is 2.00 μm or less. The copper alloy sheet material according to any one of claims 1 to 3, wherein the number density of fine second phase particles having a particle size of 20 to 30 nm present in a matrix (metal base) is 1.0 x ¹⁰⁷ particles/mm2 ^or more, and the number density of coarse second phase particles having a particle size of 0.5 µm or more is 5.0 x ¹⁰⁵ particles/mm2 ^or less. The copper alloy sheet material according to any one of claims 1 to 4, having a tensile strength in the direction parallel to the rolling of 600 MPa or more. The copper alloy sheet material according to any one of claims 1 to 5, wherein the Co content in the chemical composition is 0.50 to 2.00 mass%. The copper alloy sheet material according to any one of claims 1 to 6, having a sheet thickness of 0.04 to 0.30 mm. In the manufacturing process, intermediate product sheet material is subjected to solution treatment, intermediate cold rolling, aging treatment, finish cold rolling, tension leveler passing, and low-temperature annealing in the above order.
Solution treatment is performed at 780 to 1,060°C for 10 to 80 seconds.
When the reduction ratio of the intermediate cold rolling is R ₁ (%), the reduction ratio of the finish cold rolling is R ₂ (%), and the total reduction ratio of the intermediate cold rolling and the finish cold rolling is R _T (%), the intermediate cold rolling and the finish cold rolling are performed under conditions that satisfy at least one of the following cold rolling conditions A and B:
Aging treatment is performed before finish cold rolling under conditions that do not cause recrystallization.
The strip is passed through a tension leveler under the condition that the elongation rate is more than 1.5% and less than 3.7%.
Low-temperature annealing is performed in a mixed gas atmosphere of hydrogen gas and inert gas having a hydrogen concentration of 3 to 13 volume % at 380 to 550°C for 10 to 620 seconds.
The method for producing the copper alloy sheet material according to any one of claims 1 to 7.
(Cold rolling condition A) R ₁ ≧50%, R ₂ ≧25%, and R _T ≧75%
(Cold rolling condition B) R ₁ ≧60%, R ₂ ≧18%, and R _T ≧90% The method for manufacturing a copper alloy sheet material according to claim 8, wherein the intermediate product sheet material is a sheet material that has been subjected to cold rolling after hot rolling. An electric current-carrying part using the copper alloy sheet material according to any one of claims 1 to 7.

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