TWI448337B - Rolled copper foil - Google Patents

Description

Calendered copper foil

The present invention relates to a rolled copper foil which can be preferably used in an FPC requiring flexibility.

Copper foil for FPC (flexible printed circuit board) for bending requires high flexibility. A technique for imparting flexibility to a copper foil is known as a technique for improving the crystal orientation of the (200) plane of the copper foil (Patent Document 1) and a technique for increasing the ratio of crystal grains which are penetrated in the thickness direction of the copper foil. (Patent Document 2) A technique in which the surface roughness Ry (maximum height) corresponding to the depth of the oil pit of the copper foil is reduced to 2.0 μm or less (Patent Document 3).

The usual FPC manufacturing steps are as follows. First, a copper foil is bonded to a resin film. The joining method is a method of imidating ruthenium by applying heat treatment to a varnish applied to a copper foil, or laminating a resin film with an adhesive attached to a copper foil. The copper foil with a resin film joined by these steps is called CCL (Copper Cladding Laminate). The copper foil is recrystallized by the heat treatment in the CCL manufacturing step.

However, when the FPC is produced by using a copper foil, if the surface of the copper foil is etched in order to improve the adhesion to the coating film, there is a problem that a depression having a diameter of about 10 μm (disc sinking) occurs on the surface, and it is particularly likely to occur at a high level. In the curved copper foil. This is because the crystal orientation (200) plane of the copper foil is controlled to be uniform so as to impart high flexibility and to expand the cubic structure after recrystallization annealing. That is, it is considered that even if such control is performed, it is impossible to make all the crystal orientations uniform, and crystal grains having different crystal orientations are locally present in a uniform structure. At this time, since the etching rate differs depending on the crystal surface to be etched, the crystal grains are locally etched to be deeper than the periphery and become depressed. This depression is a cause of a decrease in the etching property of the circuit or a defect in the visual inspection and a decrease in the yield.

In the method of reducing such a depression, there has been reported a technique of mechanically polishing the surface of the copper foil before or after rolling, and imparting deformation to the modified layer after processing, and then performing recrystallization (Patent Document 4). According to this technique, by processing the altered layer, the surface group is unevenly crystallized after recrystallization, so that crystal grains having different crystal orientations are not separately present.

[Patent Document 1] Japanese Patent No. 3009383

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2006-117977

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2001-058203

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2009-280855

However, in the case of the technique described in Patent Document 4, there are many problems in that the crystal grains on the surface of the copper foil are not oriented on the (200) plane because the crystal grains are not uniform, and the bendability is lowered.

On the other hand, in the high-gloss copper foil described in Patent Document 3, the crystal orientation is easily uniform, and the dishing is less likely to occur. However, the high-gloss copper foil is not easy to handle due to the easy scratching of the surface, and is not preferable.

In view of the above, it is an object of the present invention to provide a rolled copper foil which is excellent in workability, excellent in flexibility, and excellent in surface etching property, in a state in which the surface of the copper foil is appropriately roughened.

The inventors of the present invention have conducted various studies and found that the surface of the copper foil is not roughened before the final pass of the final cold rolling, and the surface of the copper foil is roughened in the final pass of the final cold rolling. As a result, the surface of the final copper foil is roughened, and the shape and frequency (surface state) of the oil pit are less likely to cause shear bands, and the bending property is excellent, and the dish type is less depressed. Further, the inventors have found that the form and frequency (surface state) of the oil crater which is less likely to cause the shear band can be macroscopically evaluated by the crater area ratio of the self-conjugated focal microscope image.

In order to achieve the above object, in the rolled copper foil of the present invention, the ratio Ra/t of the surface roughness Ra measured on the surface of the copper foil in the direction parallel to the rolling parallel direction of 175 μm and the thickness t of the copper foil is 0.004 or more and 0.007 or less. The strength of the (200) plane (I) obtained by X-ray diffraction of the calendering surface is obtained by X-ray diffraction of the micropowder copper in a state where the crystal is recrystallized at 200 ° C for 30 minutes. The strength (I ₀ ) of the (200) plane is I/I ₀ ≧ 50, and the length of the copper foil surface is 175 μm in the parallel direction of the rolling, and is three lines which are separated by 50 μm or more in the direction perpendicular to the rolling, which corresponds to the oil pit. The ratio d/t of the average value d of the difference between the maximum height and the minimum height in the thickness direction of each straight line of the maximum depth and the thickness t of the copper foil is 0.1 or less, and the area ratio of the oil pit when measured by a conjugate focal microscope is 6% or more and 15% or less.

After the surface of the copper foil after heat treatment at 200 ° C for 30 minutes is observed by EBSD after electrolytic polishing, it is preferable that the area ratio of crystal grains having an angle difference of 15 degrees or more from [100] orientation is 20% or less. .

After the ingot is subjected to hot rolling, it is repeatedly subjected to cold rolling and annealing, and finally to final cold rolling, and in the final cold rolling step, preferably, in the stage before the final pass, Ra/ t is 0.002 or more and 0.004 or less.

According to the present invention, it is possible to obtain a rolled copper foil which has a surface of a copper foil which is moderately roughened to improve workability, is excellent in flexibility, and has excellent surface etching characteristics.

Hereinafter, the rolled copper foil according to the embodiment of the present invention will be described. In addition, in the present invention, the % is expressed by mass unless otherwise specified.

First, the technical idea of the present invention will be described with reference to Fig. 1 . When the roughness of the roll in the final cold rolling is increased and the surface of the copper foil is roughened, the operability of the copper foil is improved, but the dishing is likely to occur (previous example 1 of Fig. 1). This can be considered as follows.

The oil pit is formed on the surface of the copper foil by the cold rolling of the rough rolling roller. However, as the processing progresses, the shear deformation zone is easily formed at the end of the oil pit, and if the processing is further processed, the shear deformation zone is deeper. Expansion. Therefore, it can be considered that the sump portion which generates the deeper shear deformation band becomes a crystal grain having a different crystal orientation in other uniform tissues at the time of recrystallization, and becomes a starting point of the dish type sag at the time of etching.

On the other hand, a method of improving the gloss (surface roughness) in order to obtain the bendability of the copper foil has been known from the prior art. It is considered that this is to prevent the formation of the oil crater by performing the final cold rolling with a roller having a low roughness, whereby the shear deformation belt is less likely to be generated. However, if the glossiness of the copper foil is increased (the surface roughness is made small), the handleability of the copper foil is lowered (previous example 2 of Fig. 1), so that it is not preferable in terms of copper foil.

In contrast, the inventors have discovered that the surface of the copper foil can be prevented from being roughened by the final pass of the final cold rolling (for example, rolling with a roll having a lower roughness), and finally in the final cold rolling. In the second, the surface of the copper foil is roughened (for example, calendered with a rougher roll), the oil sump is formed to make the surface of the final copper foil rough, and the oil is not fully expanded by the shear deformation zone. The shape and frequency of the pits result in a decrease in crystal grains having different crystal orientations in a uniform structure, and a dish sinking is reduced (the inventive example of Fig. 1).

That is, it has been previously considered that the orientation of the copper foil is purely dependent on the roughness of the surface of the copper foil, but it is actually known that the scale (spreadness) of the shear deformation zone inside the material affects the degree of orientation (and dishing). Moreover, in the final cold rolling, if the expansion of the shear band can be sufficiently suppressed in the pass before the final pass, even if the surface of the copper foil is finished to be rough in the final pass, it can be obtained higher. Orientation.

Further, the present invention is characterized in that the degree of expansion of the above shear band is macroscopically evaluated by the area ratio of the oil pit observed by the conjugate focal microscope image, and the range of the area ratio at which the dish type is reduced is found.

On the other hand, the information of the oil pit cannot be clearly obtained only from the value of the surface roughness used previously. That is, when the surface of the rolled copper foil is observed, it is observed that the oil sump is generated along the right angle direction TD of the rolling, but as shown in FIG. 2, it is understood that in the cross-sectional shape of the oil pit, a triangle having a shorter length in the TD direction is known ( The symbol P1) of Fig. 2 also has a trapezoidal shape (symbol P2 of Fig. 2). Moreover, even if the depth of the oil pit is the same, there is a wide openness and a narrower pit in the RD direction. It is considered that the measurement of the surface roughness of the general so-called Ra, Ry, Rz, and Sm for measuring the surface roughness of the copper foil does not sufficiently reflect the difference in the shape of the oil pits.

Therefore, using a conjugate focal (confocal) microscope, the ratio (area ratio) of the image area corresponding to the oil pit is obtained, whereby the shape of the oil puddle can be reflected, and the dishing or bending property corresponding to the dish can be obtained. The difference between good and bad. Furthermore, the area ratio of the sump is binarized by the height difference of the Z-axis (height direction) taken by the conjugate focal length microscope before and after the specific threshold, and the portion deeper than the threshold is used as the sump portion. To select, to obtain the proportion of its area.

Next, the specification and composition of the rolled copper foil of the present invention will be described.

(1) Area ratio of oil pit

As described above, the surface of the copper foil is not roughened before the final pass of the final cold rolling, and the surface of the copper foil is roughened in the final pass of the final cold rolling, and finally the surface of the copper foil is changed. It is rough, and the shape of the oil pit where the shear deformation band is difficult to expand can be obtained, and the dish type is less depressed. Further, it has been found by the inventors of the present invention (the following examples) that the surface of the oil sump having such a shear deformation band which is not easily spread is 6% or more in the area of the oil pit when measured by a conjugate focal microscope. %the following.

If the area ratio of the oil pit exceeds 15%, the oil pit extending the shear deformation zone increases. If the shear deformation band spreads inside the material, it will become a crystal grain having different crystal orientations in other uniform tissues during recrystallization, and it is easy to cause dishing in the etching.

On the other hand, in the case where the area ratio of the oil pit is less than 6%, there are two conditions. Condition 1 is the use of a lower thickness roll in all passes of the final cold rolling. Under this condition, the deeper oil sump is less, and the shear deformation zone is not easy to expand, so the dish type sinking is reduced, but the surface roughness of the copper foil becomes too small (the following Ra/t requirements are not satisfied) Copper foil products are not easy to handle, so they are not good.

The second condition is that the surface of the copper foil is roughened before the final pass of the final cold rolling, and the surface of the copper foil is smoothed by using a roller having a lower roughness in the final pass of the final cold rolling. Under this condition, the lower roughness of the roller is used in the final pass, so that the portion of the oil pit formed before the final pass is close to the surface of the copper foil and is flattened in the final pass, and the surface roughness is obtained. Become smaller. However, the narrow valley portion inside the oil pit remains. Therefore, although the opening of the surface portion of the oil pit is narrowed and the area ratio of the oil pit itself becomes small, since the rougher roller is used before the final pass, the shear deformation band expands in the oil pit, and the final pass After that, a shear deformation band remains, and a plurality of dish forms are depressed. Further, although the area ratio of the oil pit is small, a state in which a plurality of dish forms are depressed is caused, and when the area ratio of the oil pit is less than 6%, it becomes remarkable.

Furthermore, the method of making the area ratio of the oil pits 6% or more is as long as in the final cold rolling as described above, in the shallower and unexpanded shear sump in the pass before the final pass, Rolling using a roll having a smaller roughness (surface roughness Ra, for example, 0.05 μm or less) in a pass before the final pass of the final cold rolling in the form of a sump, and in the final pass of the final cold rolling Calendering is performed using a roll having a large roughness (surface roughness Ra, for example, 0.06 μm or more), and the surface of the finally obtained copper foil may be roughened. Since the oil pit formed in the pass before the final pass is shallow, the shear band is not expanded, so even if the surface of the copper foil is roughened in the final pass of the final cold rolling, the oil band of the shear band is expanded. It is also impossible to increase, and the dish type is less depressed. On the other hand, if a roll having a large roughness (surface roughness Ra, for example, more than 0.05 μm) is used in the pass before the final pass of the final cold rolling, a crater in which the shear band is easily expanded is formed, and In the final pass, the oil pit expands, and its area increases. The area ratio of the oil pit exceeds 15%, and the expansion of the shear band becomes remarkable, which is easy to cause dish-shaped subsidence.

Here, in the final cold rolling step, the surface of the final cold-rolled copper foil is used in a pass which is smaller than the final pass, such as a roll having a roughness (surface roughness Ra of, for example, 0.05 μm or less). It becomes smoother. Specifically, in the step before the first pass of the final pass of the final cold rolling step, the ratio (Ra/t) of the surface roughness Ra to the foil thickness t is preferably 0.0020 or more and 0.0040 or less. If the final pass is rolled in a surface state such as Ra/t in this range, since the surface of the copper foil becomes rough even in the final pass, it is difficult to introduce the shear band into the formed oil pit. Therefore, it is better.

Further, as described below, (Ra/t) after the end of the final pass of the final cold rolling step is 0.004 or more and 0.007 or less.

(2) I/I ₀

In order to impart high flexibility to the copper foil of the present invention, the strength of the (200) plane obtained by the X-ray diffraction of the calendering surface will be adjusted to a recrystallized structure by heating at 200 ° C for 30 minutes ( I) is defined as I/I ₀ ≧50 with respect to the intensity (I ₀ ) of the (200) plane obtained by X-ray diffraction of fine powder copper. Thereby, the degree of orientation of the (200) plane excellent in flexibility is improved. If I/I ₀ <50 is reached, the bendability is lowered. The above annealing at 200 ° C for 30 minutes mimics the temperature history of the copper foil imparted in the CCL manufacturing step.

Further, in order to make I/I ₀ ≧ 50, it is preferable that the degree of final cold rolling is 98% or more.

(3) Ra/t

In order to reduce the dishing shape without changing the surface roughness as compared with the former, Ra (mm) / t (mm) after the final cold rolling is specified to be 0.004 or more and 0.007 or less. If so, the surface roughness can be made the same as the previous copper foil, and the dishing can be reduced. Further, by dividing the surface roughness by the thickness, the surface roughness of the copper foil can be evaluated without depending on the thickness of the copper foil. For example, if the thickness t of the copper foil is thin, there is a problem in that even if the surface roughness is the same, the ratio of the surface unevenness which occupies the thickness of the copper foil becomes large, and the area ratio of the oil pit according to the above cannot be sufficiently performed. Copper foil surface evaluation.

Here, Ra (center line average roughness) is defined as JIS B0601, and in the present invention, the length of the surface of the copper foil in the parallel direction of the rolling is 175 μm, and the straight lines in the direction perpendicular to the rolling are separated by three lines of 50 μm or more. The average of the measured values.

(4)d/t

That is, it is convenient to consider that the roughness of the surface of the copper foil is not too large, and in the case where the shear deformation zone is not expanded in most of the oil pits, there are also several deep oil pits. The shear deformation zone is more likely to expand in deeper oil pits, and in this case it is the starting point for dishing. Therefore, in the present invention, the average value d of the maximum depth of the oil pit is defined as d/t ≦ 0.1.

By dividing the average value d of the maximum depth of the oil pit by the thickness t, the copper foil surface evaluation can be performed without depending on the thickness of the copper foil. That is, even the maximum depth of the oil pit The degree is the same, but if the thickness t of the copper foil is thin, the influence becomes large.

Here, the average value of the maximum pit depth of an oil-based d: the surface of the copper foil 3 in parallel to the rolling direction RD of 175 m length, and at right angles to the rolling direction TD of more than 50 m 3, respectively straight lines L ₁ ~ L apart ₃ is an average value of the difference di between the maximum height H _M and the minimum height H _S of the respective straight lines L ₁ to L ₃ corresponding to the maximum depth of the oil pit. Specifically, the distribution in the thickness direction on L ₁ to L ₃ is measured by the contact roughness, and the maximum height H _M and the minimum height H _{S are obtained} , and the di of the straight lines L ₁ to L ₃ may be averaged.

The thickness of the copper foil (or copper alloy foil) is not particularly limited, and for example, 5 to 50 μm can be preferably used.

(5) Azimuth difference of EBSD

As described above, the dish type is recessed by heat treatment when the copper foil and the resin film are joined, and when the ratio of the crystal grains having different crystal orientations in the uniform structure of the recrystallization is large, the etching is performed at the time of etching. Individual dies can etch deeper than the surrounding. Therefore, in the above heat treatment, the copper foil is heated to a recrystallized structure by heat treatment conditions (for 30 minutes at 200 ° C) which mimic the temperature history of the copper foil in the CCL manufacturing step. Next, in the case where the surface of the copper foil is subjected to electrolytic polishing on the surface of the copper foil and observed by EBSD, it is preferable that the area ratio of the crystal grains having an angle difference of 15 degrees or more from [100] is 20%. the following. Further, the copper foil which has been subjected to the heat history and becomes CCL can be heated at 200 ° C for 30 minutes. Since it is heat-treated until it is temporarily recrystallized, it does not change almost even if it is heated again. Therefore, when the EBSD is observed, the copper foil which receives the heat history and the unacceptable copper foil are not distinguished, and are heated at 200 ° C for 30 minutes. .

In the case of observation by EBSD, if the area ratio is less than 20%, the difference in orientation between the crystal grains on the surface of the copper foil is small, and the proportion of crystal grains having different crystal orientations in the uniform structure is small, so The depression caused by etching (disc sinking) is reduced. Furthermore, in the case of observation by EBSD, in order to make the above area ratio less than 20%, it is necessary to suppress the expansion of the shear band in the pass before the final pass by the final cold rolling as described above, that is, It is sufficient to use a roll having a relatively small roughness (surface roughness Ra, for example, 0.5 μm or less) in the pass before the final pass of the final cold rolling.

(6) Composition

As the copper foil, fine copper or oxygen-free copper having a purity of 99.9 wt% or more can be used, and a well-known copper alloy can be used depending on the strength or conductivity required.

The specifications of the oxygen-free copper are JIS-H3510 (alloy No. C1011) and JIS-H3100 (alloy No. C1020), and the specifications of the refined copper are JIS-H3100 (alloy No. C1100).

A well-known copper alloy, for example, may be 0.01 to 0.3 wt% of a tin-doped copper alloy (more preferably 0.001 to 0.02 wt% of a tin-doped copper alloy); 0.01 to 0.05 wt% of a silver-doped copper alloy; 0.005 to 0.02 wt% Indium-doped copper alloy; 0.005 to 0.02 wt% of a chromium-doped copper alloy; and a copper alloy containing a total of 0.05 wt% or less selected from the group consisting of tin, silver, indium, and chromium; wherein the conductivity is excellent Cu-0.02 wt% Ag is often used.

Next, an example of a method for producing a rolled copper foil of the present invention will be described. First, an ingot composed of copper and a necessary alloying element and further an unavoidable impurity is hot-rolled, then subjected to cold rolling and annealing, and finally to a specific thickness by final cold rolling.

Here, as described above, the surface of the copper foil is not roughened before the final pass of the final cold rolling, and the surface of the copper foil is roughened in the final pass of the final cold rolling. Even if the surface of the final copper foil is roughened, it becomes a surface state of the oil pit having a shear deformation band which is not easily expanded, and the dish type is reduced. Further, such a surface having a small shear deformation band has an area ratio of 6% to 15% or less.

Therefore, before the final pass of the final cold rolling, in order to make the surface of the copper foil not rough, the roll having a relatively small roughness (surface roughness Ra, for example, 0.05 μm or less) is used, or the final cold rolling is performed. In the first pass, the degree of processing becomes large and the rolling can be performed. On the other hand, in the final pass of the final cold rolling, a roll having a relatively large roughness (surface roughness Ra, for example, 0.06 μm or more) is used, or a rolling oil having a high viscosity is used for rolling, and the final result is obtained. The surface of the copper foil becomes rough.

Furthermore, in order to produce a surface state in which the surface of the final copper foil is rough, but the shear deformation zone is difficult to expand, it is necessary to use the above-mentioned two passes in the final cold pass or the final pass. Calendering is carried out with a coarser roll or with a higher viscosity rolling oil, but in terms of ease of adjustment, it is preferred to adjust the rolling conditions in the final pass. On the other hand, if the roughness of the roll is roughened from the final three passes of the final cold rolling, the shear deformation zone is further expanded by the final pass in the formed oil pit.

Further, the annealing conditions may be adjusted so that the average grain size of the recrystal grains obtained by the annealing before the final cold rolling is 5 to 20 μm. Further, the degree of rolling work in the final cold rolling may be 98% or more.

[Examples]

The ingot is cast by adding copper or oxygen-free copper having the elements shown in Table 1 as a raw material, and hot rolling is performed at 800 ° C or higher until the thickness reaches 10 mm, and the surface scale is subjected to planar cutting, and then the cooling is repeated. Calendering and annealing were finally finished by final cold rolling to the thicknesses shown in Table 1. The degree of calendering in the final cold rolling is 99.2%.

In addition, "TPC to which 0.02% of Ag is added" in the composition column of Table 1 means that 0.02% by mass of Ag is added to the refined copper (TPC) of JIS-H3100 (alloy No. C1100). In addition, "the addition of 0.01% Ag 0.005% Sn of OFC" in the composition column of Table 1 means that 0.01% by mass of Ag and 0.005% by mass are added to the oxygen-free copper (OFC) of JIS-H3100 (alloy No. C1020). Sn. However, oxygen-free copper (OFC) having a specification of JIS-H3510 (alloy No. C1011) was used as the oxygen-free copper only in Example 6, and the specification was JIS-3100 (alloy in Examples 4, 5, 8, and 9). Oxygen-free copper (OFC), number C1020), is used as oxygen-free copper.

Further, the final cold rolling was carried out in 10 to 15 passes, and as shown in Table 1, the surface roughness of the roll before the final pass, and the surface roughness of the final pass roll were rolled. The surface roughness of the rolls from the first pass of the final pass until the final pass is the same. Further, the degree of processing of the final rolling was 99% except for Comparative Example 5, and Comparative Example 5 was 96%.

Each of the copper foil samples obtained in this manner was evaluated for each characteristic.

(1) Surface roughness Ra: Ra (center line average roughness) is measured based on JIS B0601, and a conjugate focal length microscope (manufactured by Lasertec Co., Ltd., model: HD100D) is used on the surface of the sample in the parallel direction of rolling. The value measured was 175 μm in length.

(2) Cube collection organization

After the sample was heated at 200 ° C for 30 minutes, the integral value (I) of the (200) plane intensity obtained by the X-ray diffraction of the rolled surface was obtained. This value was divided by the integral value (I ₀ ) of the (200) plane intensity of the previously measured fine powder copper (used after heating at 300 ° C for 1 hour in a hydrogen stream), and the I/I ₀ value was calculated.

(3) Maximum depth of the oil pit (average d)

Using a conjugate focal length microscope (manufactured by Lasertec Co., Ltd., model: HD100D), as shown in Fig. 3, the length of the copper foil surface in the direction parallel to the rolling direction RD was 175 μm, and the length of the rolling orthogonal direction TD was separated by 50 μm or more. The difference di between the maximum height H _M and the minimum height H _S on the straight lines L ₁ to L ₃ . The di of each of the straight lines L ₁ to L ₃ is averaged as d. Furthermore, it is set to d (mm) / t (mm).

(4) Azimuth difference of EBSD

The surface of the sample after heating at 200 ° C for 30 minutes in (2) was subjected to electrolytic polishing to EBSD (Electronic Backscatter Diffraction Device, JEOL 8500F, Acceleration Voltage 20kV, Current 2 _e -8A, Measurement Range 1000 μm × 1000 μm, step width 5 μm) was observed. The area ratio of the crystal grains having an angular difference of 15 degrees or more from the [100] orientation was obtained by image analysis. Further, the number of crystal grains in the observation range of 1 mm square on the surface of the sample was visually counted to exceed 20 μm. Next, the sample containing the observation range was etched at room temperature for 2 minutes using a 20% solution of ADEKATEC CL-8 (manufactured by Adeka Co., Ltd.), and the image obtained by photographing the surface after etching with an optical microscope was light-dark. In the binarization, the dark portion exceeding the short diameter of 50 μm was counted as a dish type sag. Further, the surface of the copper foil after the etching has a shape reflecting the crystal orientation, and the structure having the [100] orientation is a surface parallel to the surface of the copper foil. On the other hand, the portion having the other crystal orientation may be caused by the crystal orientation. Bump. Therefore, the dished portion is darker in the optical microscope.

4 is an optical microscope image showing the surface of Example 1, and FIG. 5 is a surface optical microscope image of Comparative Example 3.

(4) Area ratio of oil pit

The surface of the sample was measured with a conjugate focal length microscope (manufactured by Lasertec Co., Ltd., model: HD100D) for a measurement field of 300 × 300 μm. The sample was moved in the optical axis (Z-axis) direction in the measurement field of view, and an image having a depth of 10 nm from the surface of the copper foil was obtained (this is called an FMS (Focus Scan Memory) image). Next, a portion having a depth of 10 nm from the surface of the copper foil was treated as a crater and binarized. An example of this image is shown in Figures 6 and 7, and the bright color portion is a sump. Next, with respect to the measurement field of view of 300 × 300 μm, the area of the oil pit (area of bright color) was obtained using a commercially available image processing software, and the area ratio of the oil pit was calculated.

(5) Surface scars

The surface of each sample was visually observed, and the case where the flaw having a length of 10 mm or more in the rolling direction was 5 parts/m ² or more was set as ×.

(6) Flexibility

After the sample was heated at 200 ° C for 30 minutes to recrystallize, the bending fatigue life was measured by the bending test apparatus shown in FIG. 8 . This device has a structure in which the vibration transmitting member 3 is coupled to the oscillation transmitting member 3, and the test copper foil 1 is fixed to the device by a total of four portions of the screw 2 indicated by the arrow and the front end portion of the third portion. When the vibrating portion 3 is driven up and down, the intermediate portion of the copper foil 1 is bent at a specific radius of curvature r into a tubular shape. This test is to determine the number of breaks to the time of repeated bending under the following conditions.

Further, in the case where the sheet thickness is 0.012 mm, the test conditions are as follows: test piece width: 12.7 mm, test piece length: 200 mm, test piece take-up direction: the test piece has a length direction parallel to the rolling direction The method is to collect, the radius of curvature r: 2.5 mm, the vibration stroke: 25 mm, and the vibration speed: 1500 times/min. In addition, when the bending fatigue life was 30,000 or more, it was judged that the bending property was excellent.

Further, when the thicknesses are 0.018 mm and 0.006 mm, respectively, the curvature radius r is changed to 4 mm and 1.3 mm, respectively, so that the bending test is the same as the bending strain when the thickness is 0.012 mm. The test conditions are the same.

The results obtained are shown in Table 1.

As can be seen from Table 1, the angle difference from the [100] orientation of EBSD when I/I ₀ ≧ 50, d/t is 0.1 or less, and the area ratio of the oil pit is 6 or more and 15% or less. The area ratio of the crystal grains of 15 degrees or more is less than 20%, and the number of dish-type sags is small, and the surface of the copper foil is less scarred and excellent in flexibility. Further, in the case of each of the examples, the Ra/t of the final product was 0.004 or more and 0.007 or less.

On the other hand, in the case of Comparative Examples 1 and 5 in which the surface roughness of all the passes of the final cold rolling (including the final pass) was Ra = 0.44 μm or less, the Ra/t of the final pass was not Up to 0.004, the area ratio of the oil pit is less than 6%, so the surface of the copper foil is scratched, and the workability is deteriorated.

Further, in the case of Comparative Example 5, although the surface roughness was small and the area ratio of the oil pit was less than 6%, the calendering degree in the final cold rolling was 96%, which was low, so I/ I ₀ <50, and is a state in which the degree of orientation is low and the crystal orientations are inconsistent. In the case where the crystal orientations are inconsistent, it means that there are many crystal grains having an angular difference of 15 degrees or more from the [100] orientation, and since the area ratio of the crystal grains exceeds 20%, the dish type sinking also occurs.

In the final cold rolling, the surface roughness of the roll before the final pass was roughened to Ra=0.06 μm or more, and the surface roughness of the roll of the final pass was Ra=0.05 μm or less. In the case, the Ra/t of the final product is less than 0.004, so that the surface of the copper foil is scratched and the workability is deteriorated. Moreover, since the rougher roll is used before the final pass, the shear deformation zone is expanded in the oil pit, and even if the roll having a small roughness is used in the final pass, the shear deformation zone remains, and The area ratio of the oil pit is less than 6%, so the area ratio of the crystal grains having an angle difference of 15 degrees or more from the [100] orientation exceeds 20%. As a result, a plurality of dish forms are depressed.

In the case of Comparative Examples 3, 4, and 6 in which the surface roughness of the roll before the final pass and the surface roughness of the final pass are both coarsened to Ra = 0.06 μm or more in the final cold rolling, The Ra/t of the first pass of the final pass is 0.004 or more, and a plurality of oil pits with extended shear deformation zones are generated before the final pass. Therefore, after the final pass, the area ratio of the oil puddle exceeds 15%, and the area ratio of the crystal grains having an angle difference of 15 degrees or more from the [100] direction exceeds 20%. As a result, a plurality of dish forms are depressed.

Further, in the case of Comparative Examples 3 and 4, since the surface roughness of the entire pass of the final cold rolling was made thick, a plurality of oil pits in which the shear deformation zone was remarkably expanded were generated inside the material. Therefore, not only the area ratio of the sump is more than 15%, but also the degree of orientation of the crystal on the surface of the copper foil is lowered to become I/I ₀ <50. Corresponding to this, the area ratio of the crystal grains having an angular difference of 15 degrees or more from the [100] orientation exceeds 20%. On the other hand, in the case of Comparative Example 6, since the roughness of the roll before the final pass was smoother than Comparative Examples 3 and 4, I/I ₀ was 50 or more and higher than the values of Comparative Examples 3 and 4. Good bending.

1. . . Copper foil

2. . . Screw

3. . . Vibration transmitting member

4. . . Oscillating drive

P1. . . Oil pit shape

P2. . . Oil pit shape

RD. . . Calendering parallel direction

TD. . . Calendering right angle

L ₁ to L ₃ . . . straight line

H _M . . . maximum height

H _S . . . Minimum height

Ry, Ra. . . Surface roughness

d. . . average value

Di. . . The difference between the maximum height and the minimum height

I, I ₀ . . . strength

t. . . thickness

r. . . Radius of curvature

Fig. 1 is a view showing the relationship between the roughness of the surface of the copper foil and the shear deformation band.

Fig. 2 is a view showing the shape of a sump.

Fig. 3 is a view showing a measurement method corresponding to the average value d of the maximum depth of the oil pit.

Fig. 4 is a view showing an optical microscope image of Example 1.

Fig. 5 is a view showing an optical microscope image of Comparative Example 1.

Fig. 6 is a view showing a conjugate focal microscope image of Example 1.

Fig. 7 is a view showing a conjugate focal microscope image of Comparative Example 1.

Fig. 8 is a view showing a method of measuring the bending fatigue life by a bending test device.

Claims (3)

A rolled copper foil having a ratio Ra/t of a surface roughness Ra measured on a surface of a copper foil in a direction parallel to a rolling direction of 175 μm and a thickness t of the copper foil of 0.004 or more and 0.007 or less, and is heated at 200 ° C for 30 minutes to adjust the quality to In the state of the recrystallized structure, the intensity of the (200) plane obtained by the X-ray diffraction of the calendering surface is relative to the intensity of the (200) plane obtained by the X-ray diffraction of the fine powder copper ( I ₀ ) is I/I ₀ ≧ 50; the length of the copper foil surface is 175 μm in the parallel direction of the rolling, and is three lines which are separated by 50 μm or more in the direction perpendicular to the rolling direction, which corresponds to the maximum depth of the oil pit. The ratio d/t of the average value d of the difference between the maximum height and the minimum height in the thickness direction of the straight line to the thickness t of the copper foil is 0.1 or less; and the area ratio of the oil pit when measured by a conjugate focal microscope is 6% or more 15% or less. The rolled copper foil according to claim 1, wherein the surface of the copper foil after heat treatment at 200 ° C for 30 minutes is subjected to electrolytic polishing, and then observed by EBSD, the angle difference from the [100] orientation is 15 degrees or more. The area ratio of the crystal grains is 20% or less. The rolled copper foil according to claim 1 or 2, wherein the ingot is subjected to hot rolling, followed by cold rolling and annealing, and finally subjected to final cold rolling to be manufactured. In the final cold rolling step, In the stage before the final pass, Ra/t is 0.002 or more and 0.004 or less.