KR20120044912A - Rolled copper foil - Google Patents

Abstract

PURPOSE: A rolled copper film is provided to improve the treating efficiency, flexibility, and surface etching property thereof. CONSTITUTION: In a rolled copper film, the ratio between a surface roughness, which is measured at 175μm in a rolled direction, and a thickness is 0.004-0.007. When the rolled copper film is heated for 30 minutes at 200°C, the ratio between a surface strength of the rolled surface obtained by X-ray diffraction and the strength of pulverized copper powder obtained by X-ray diffraction is equal to or greater than 50. On three straight lines that are separated 50μm or more in a vertical direction to the rolled direction, the ratio between the average height of the lines in a thickness direction and the thickness of the copper film is 0.1 or less.

Description

Rolled Copper Foil {ROLLED COPPER FOIL}

The present invention relates to a rolled copper foil which is preferably used for FPC where flexibility is required.

High flexibility is required for copper foil used for bending FPC (flexible printed circuit board). As a method for imparting flexibility to the copper foil, a technique for increasing the degree of orientation of the crystal orientation of the (200) plane of the copper foil (Patent Document 1), a technique for increasing the ratio of crystal grains penetrating in the plate thickness direction of the copper foil (Patent Document 2), The technique (patent document 3) which reduces the surface roughness Ry (maximum height) corresponding to the depth of the oil pit of copper foil to 2.0 micrometers or less is known.

The general FPC manufacturing process is as follows. First, copper foil is bonded with a resin film. There exists a method of imidating by applying heat processing to the varnish apply | coated on copper foil, and the method of laminating | stacking and laminating the resin film with an adhesive agent and copper foil. The copper foil with a resin film bonded by these processes is called CCL (copper laminated board). Copper foil is recrystallized by the heat processing in this CCL manufacturing process.

By the way, when manufacturing FPC using copper foil, when copper surface is etched in order to improve adhesiveness with a coverlay film, the recessed part (dish down) of about 10 micrometers in diameter may arise in the surface, Especially It is easy to occur in high bending copper foil. This cause originates from controlling so that the crystal orientation 200 surface of copper foil may coincide so that the cube structure after recrystallization annealing may develop in order to provide high flexibility. In short, even if such a control is performed, the orientations of all the crystals do not coincide, and it is considered that the grains having different crystal orientations are present locally in a uniform structure. At that time, since the etching rate differs depending on the crystal surface to be etched, the crystal grains are locally etched deeper than the surroundings to become recesses. This dent causes a decrease in the etching property of the circuit, or is judged to be defective in appearance inspection, thereby causing a decrease in yield.

As a method of reducing such a recessed part, the technique (patent document 4) which recrystallizes after performing the mechanical grinding | polishing to the surface of copper foil and adding a deformation | transformation into a process-deterioration layer before rolling or after rolling is reported. According to this technique, non-uniform crystal grains are clustered on the surface after recrystallization by the processing altered layer, so that crystal grains having different crystal orientations do not exist alone.

Japanese Patent Publication No. 3009383 Japanese Unexamined Patent Publication No. 2006-117977 Japanese Unexamined Patent Publication No. 2001-058203 Japanese Unexamined Patent Publication No. 2009-280855

However, in the case of the technique described in Patent Literature 4, there are many non-uniform crystal grains, and since the crystals on the surface of the copper foil are not oriented in the (200) plane, there is a problem that the flexibility is lowered.

On the other hand, the high gloss copper foil of patent document 3 is easy to match crystal orientation, and there is little generation of dish down. However, high-gloss copper foil is not preferred because it is not easy to handle, such as scratches easily on its surface.

Then, this invention was made | formed in order to solve the said subject, Comprising: It aims at providing the rolled copper foil which makes the copper foil surface moderately rough, the handling property is favorable, is excellent in bendability, and is excellent in surface etching characteristic.

As a result of various studies, the present inventors have not roughened the surface of the copper foil immediately in front of the final pass of the final cold rolling, but roughened the surface of the final copper foil by roughening the surface of the copper foil in the final pass of the final cold rolling. The shape and frequency of the oil pit (surface state) are less likely to generate shear bands, and it has been found to be excellent in flexibility and less dish down, and to form and frequency of oil pits that are less likely to generate shear bands (surface). State) can be evaluated macroscopically by the area ratio of the oil pit from the confocal microscope image.

In order to achieve the above object, the rolled copper foil of the present invention has a surface roughness (Ra) measured at a length of 175 µm in the rolling parallel direction on the surface of the copper foil, and a ratio (Ra / t) of the thickness (t) of the copper foil. In the state where it is 0.004 or more and 0.007 or less, and it heats at 200 degreeC for 30 minutes, and is refined to recrystallization structure, the intensity | strength (I) of the (200) plane calculated | required by the X-ray diffraction of the rolled surface is determined by X-ray diffraction of fine powder copper. calculated 200, and the intensity _{(I 0) I / I 0} ≥ 50 on the surface, length 175 ㎛ in the rolling parallel direction on the surface of the copper foil, and also on the three straight lines that are each at least 50 ㎛ separated in the rolling direction perpendicular thereto, oil The average value (d) of the difference between the maximum height and the minimum height in the thickness direction of each straight line corresponding to the maximum depth of the pit, and the ratio (d / t) of the thickness (t) of the copper foil is 0.1 or less, and a confocal microscope The area ratio of the oil pit at the time of a measurement is 6% or more and 15% It is as follows.

In the case where the copper foil surface after heat treatment above 200 ° C. for 30 minutes is observed by EBSD after electropolishing, the area ratio of crystal grains having an angle difference from the [100] orientation of 15 degrees or more is preferably 20% or less.

After the hot rolling of the ingot, cold rolling and annealing are repeated, and finally the final cold rolling is carried out. In the final cold rolling process, it is preferable that Ra / t is 0.002 or more and 0.004 or less in the step before the final pass. .

ADVANTAGE OF THE INVENTION According to this invention, the copper foil surface is moderately roughened, handleability improves, it is excellent in bendability, and the rolled copper foil with favorable surface etching characteristic is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship of the roughness of a copper foil surface, and a shear deformation zone.
2 is a view showing the shape of an oil pit.
3 is a diagram showing a method of measuring an average value d corresponding to the maximum depth of an oil pit.
4 is a view showing an optical microscope image of the surface of Example 1. FIG.
5 is a view showing an optical microscope image of the surface of Comparative Example 1. FIG.
6 is a view showing a confocal microscope image of Example 1. FIG.
7 is a view showing a confocal microscope image of Comparative Example 1. FIG.
It is a figure which shows the method of measuring a bending fatigue life with a bending test apparatus.

Hereinafter, the rolled copper foil which concerns on embodiment of this invention is demonstrated. In addition, in this invention,% shall show the mass% unless there is particular notice.

First, the technical idea of the present invention will be described with reference to FIG. 1. When the roll roughness in the final cold rolling is increased to roughen the surface of the copper foil, the handleability of the copper foil is improved, but dish down is likely to occur (the conventional example 1 in FIG. 1). This is considered as follows.

Although the oil pit is formed in the surface of copper foil by the rough roll in final cold rolling, a shear deformation zone is likely to generate | occur | produce in the front-end | tip of an oil pit as a process progresses. In addition, as the machining continues, the shear deformation zone deeply develops. In this way, the portion of the oil pit in which the deep shear deformation zone is generated is considered to be a crystal grain having a different crystal orientation among other uniform structures at the time of recrystallization and to be the starting point of the dish down during etching.

On the other hand, the method of raising glossiness (surface roughness) is known conventionally, in order to acquire the flexibility of copper foil. This is considered to be because the final cold rolling with a roll having a low roughness suppresses the formation of oil pits, thereby making it difficult to generate the shear deformation zone. However, when the glossiness of copper foil is increased (small surface roughness), since the handleability of copper foil falls (the conventional example 2 of FIG. 1), it is not preferable to the side using copper foil.

In contrast, the present inventors do not roughen the surface of the copper foil just before the final pass of the final cold rolling (for example, by rolling with a low roughness roll), and roughen the surface of the copper foil in the final pass of the final cold rolling. (For example, by rolling with a rough roll), the oil pit is formed and the surface of the final copper foil becomes rough, but the shape and frequency of the oil pit where the shear deformation zone does not develop very much, resulting in crystallization in a uniform structure. It was found that grains with different orientations were reduced, resulting in less dishdown (example of the invention in FIG. 1).

In short, the orientation of copper foil has conventionally been thought to simply depend on the roughness of the surface of copper foil, but in practice, it can be seen that the scale (development degree) of the shear deformation zone inside the material affects the orientation degree (and dish down). there was. And in final cold rolling, if the development of a shear zone can fully be suppressed in the pass before a final pass, even if it finishes roughly a copper foil surface in a final pass, high orientation can be obtained.

The present invention is characterized in that the degree of development of the shear stage described above is evaluated macroscopically based on the area ratio of the oil pit from the confocal microscope image, and the range of the area ratio in which dish down is reduced is characterized.

On the other hand, only the value of the surface roughness conventionally used cannot grasp | ascertain the information of oil pits clearly. In other words, when the surface of the rolled copper foil is observed, the occurrence of oil pits is observed along the rolling right angle direction TD. As shown in FIG. 2, the cross-sectional shape of the oil pits is a triangle having a short length in the TD direction (FIG. In addition to the symbol P1 of 2, it was found that the trapezoidal shape (symbol P2 of FIG. 2) also exists. Moreover, even if the depth of an oil pit is the same, the opening degree of a pit is wide and narrow in the RD direction. It is thought that the difference in the shape of these oil pits cannot be sufficiently reflected by measurement of surface roughness such as general Ra, Ry, Rz, and Sm, which measure the undulation of the copper foil surface.

Therefore, by using a confocal (confocal) microscope, the ratio (area ratio) of the image area corresponding to the oil pit is obtained, thereby reflecting the shape of the oil pit, corresponding to both the dish-down and the bendability of the bend. You can get a difference. In addition, the area ratio of the oil pit binarizes the altitude difference of the Z-axis (height direction) captured by the confocal microscope before and after a predetermined threshold, and extracts a portion deeper than this threshold as the oil pit portion. The area ratio is obtained.

Next, the regulation and composition of the rolled copper foil of this invention are demonstrated.

(1) Area ratio of oil pit

As described above, the shear deformation zone develops while roughening the surface of the final copper foil by roughening the surface of the copper foil in the final pass of the final cold rolling, without roughening the surface of the copper foil just before the final pass of the final cold rolling. The shape of the oil pit which is hard to do is obtained, and dish down is reduced. And the surface of the oil pit which such a shear deformation zone is hard to develop develops that the area ratio of the oil pit measured by a confocal microscope will be 6% or more and 15% or less (Example mentioned later) Turned out.

When the area ratio of the oil pit exceeds 15%, the oil pit in which the shear deformation zone is developed increases. If the shear strain band develops inside the material, crystal grains differ in crystal orientation among other uniform structures during recrystallization, and dish down easily occurs during etching.

On the other hand, when the area ratio of the oil pit is less than 6%, there are two conditions. The first condition uses a low roughness roll for all passes of the final cold rolling. Under these conditions, dish down is reduced because there are few deep oil pits and the shear deformation zone is less likely to develop, but the surface roughness of the copper foil becomes too small (does not satisfy the requirements of Ra / t described later), and therefore the handling of the copper foil product It is not desirable because there is difficulty.

The second condition is to roughen the surface of the copper foil immediately before the final pass of the final cold rolling, and to smooth the surface of the copper foil by using a low roughness roll in the final pass of the final cold rolling. In this condition, by using a roll with a low roughness in the final pass, the portion of the oil pit formed immediately before the final pass is close to the copper foil surface, widens in the final pass and becomes flat, resulting in a small surface roughness. However, the narrow valley inside the oil pit remains. As a result, the opening of the surface portion of the oil pit becomes narrow and the area ratio of the oil pit becomes small, but since the rough roll is used immediately before the final pass, the shear deformation zone is developed in the oil pit, and the shear deformation zone is maintained even after the final pass. Many dish downs occur. And the state in which many dishdowns with a small area ratio of an oil pit generate | occur | produce in this way becomes remarkable when the area ratio of an oil pit is less than 6%.

Moreover, as a method of making the area ratio of an oil pit more than 6%, in the final cold rolling as mentioned above, the oil pit is formed in the oil pit which is shallow in the pass before a last pass, and the shear zone does not develop. In the pass before the final pass of the final cold rolling, the surface is rolled using a relatively small roll (the surface roughness Ra is, for example, 0.05 µm or less), and in the final pass of the final cold rolling, the roughness (surface What is necessary is just to roll using a relatively large roll of roughness Ra (for example, 0.06 micrometer or more), and to roughen the copper foil surface finally obtained. In the pass before the final pass, the oil pit formed is shallow and the shear zone is not developed. Therefore, even if the surface of the copper foil is roughened in the final pass of the final cold rolling, the oil pit in which the shear zone is developed does not increase and the dish down is reduced. . On the other hand, when rolling using a roll having a large roughness (surface roughness Ra exceeds, for example, 0.05 µm) in a pass before the final pass of the final cold rolling, an oil pit which is easy to develop a shearing band is formed, and finally The oil pit develops in the path, the area thereof increases, the area ratio of the oil pit exceeds 15%, the development of the shear stage is remarkable, and dish down is likely to occur.

Here, in the final cold rolling step, the copper foil surface of the final cold rolling becomes relatively smooth by using a roll having a relatively small roughness (surface roughness Ra is 0.05 µm or less) in the pass before the final pass. Specifically, in the step before one pass of the final pass of the final cold rolling step, the ratio Ra / t of the surface roughness Ra and the foil thickness t may be 0.0020 or more and 0.0040 or less. When the final pass is rolled under the surface state in which Ra / t is in this range, even if the surface of the copper foil is roughened in the final pass, the shear zone is not easily introduced into the formed oil pit.

In addition, as mentioned later, (Ra / t) after completion of the last pass of a final cold rolling process shall be 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 (I) of the (200) plane obtained by X-ray diffraction of the rolled surface is obtained in the state of being heated at 200 ° C. for 30 minutes to obtain a recrystallized structure. The intensity (I ₀ ) of the (200) plane determined by X-ray diffraction is defined as I / I ₀ ≥ 50. Thereby, the orientation degree of the (200) surface excellent in bendability becomes high. I / I ₀ < When it reaches 50, flexibility will fall. Annealing for 30 minutes at said 200 degreeC mimics the temperature history provided to copper foil in a CCL manufacturing process.

In addition, I / I ₀ ≥ 50 in order to be, it is preferred that the degree of working of final cold rolling of 98% or more.

(3) Ra / t

In order to reduce dish down without changing surface roughness from the conventional one, Ra (mm) / t (mm) after final cold rolling is prescribed | regulated as 0.004 or more and 0.007 or less. In this way, dish down can be reduced, making surface roughness equivalent to conventional copper foil. Moreover, the roughness of the copper foil surface can be evaluated regardless of the thickness of copper foil by dividing surface roughness by thickness. For example, when the thickness t of copper foil becomes thin, even if it is the same surface roughness, the ratio of the surface unevenness to copper foil thickness will become large, and the copper foil surface by the area ratio of said oil pit may not be fully evaluated.

Here, Ra (center line average roughness) is prescribed | regulated to JIS B 0601, and in this invention, the value measured on the three straight lines which are 175 micrometers in length in the rolling parallel direction in the copper foil surface, and are spaced 50 micrometers or more in the rolling perpendicular direction, respectively. The average value of

(4) d / t

Even if the roughness of the copper foil surface is not so large, and most of the oil pits are considered to have not developed very much the shear deformation zone, there may be some deep oil pits. In deep oil pits, the shear deformation zone is likely to develop, in which case it is a starting point for the occurrence of dish down. Therefore, in the present invention, the average value d of the maximum depth of the oil pits is defined as d / t ≦ 0.1.

By dividing the average value d of the maximum depth of an oil pit by thickness t, the copper foil surface can be evaluated regardless of the thickness of copper foil. That is, even if the maximum depth of oil pits is the same, when the thickness t of copper foil becomes thin, the influence becomes large.

Here, the average value d of the maximum depth of an oil pit is 175 micrometers in length in the rolling parallel direction RD in copper foil surface, and is spaced 50 micrometers or more in the rolling perpendicular direction TD, respectively, as shown in FIG. of a straight line (L _1? L ₃₎ on the oil feet up the height of the thickness direction of each straight line (L _1? L ₃₎ corresponding to the maximum depth (H _M) and the difference between the minimum height (H _S) of (di) Is the average value. Specifically, with contact roughness, L ₁ ? Measuring the profile of the thickness direction on the L ₃ is the average of the di If the maximum height (H _M) and obtaining a minimum height (H _S), each line (L _1? L _3).

Although the thickness of copper foil (or copper alloy foil) is not specifically limited, For example, 5? 50 micrometers can be used preferably.

(5) Defense difference by EBSD

As described above, the dish down is a single crystal grain at the time of etching when there is a large proportion of crystal grains having different crystal orientations alone in the uniform structure recrystallized by heat treatment when the copper foil is bonded to the resin film. It is a recessed part formed by etching deeper than this circumference. Therefore, as said heat treatment, copper foil is heated by heat processing conditions (30 minutes at 200 degreeC) modeled after the temperature history given to copper foil in a CCL manufacturing process, and it refining to a recrystallized structure. And as a crystal orientation of this state, when the copper foil surface is observed by EBSD after electropolishing, it is preferable that the area ratio of the crystal grain whose angle difference from a [100] orientation is 15 degrees or more is 20% or less. Moreover, what is necessary is just to heat for 30 minutes at 200 degreeC also about the copper foil which became CCL which has already received the heat history. Since the thing heat-treated until once recrystallized hardly changes even if it heats further, in observation of observation by EBSD, it heats at 200 degreeC for 30 minutes, without distinguishing between copper foil which received a heat history, and copper foil which does not receive. Shall be.

When observed with EBSD, if the area ratio is less than 20%, the orientation difference between the crystal grains on the surface of the copper foil is small, and the ratio of crystal grains with different crystal orientations alone in a uniform structure becomes smaller, so that the dents formed by etching ( Dish down) is reduced. In addition, in order to make the said area ratio less than 20% when it observes by EBSD, in the final cold rolling as mentioned above, before the final pass of the final cold rolling, in other words, the development of a shear zone is suppressed in the pass before a final pass. What is necessary is just to roll using the roll with a comparatively small roughness (surface roughness Ra is 0.05 micrometer or less) in a pass | pass.

(6) composition

As copper foil, tough pitch copper and oxygen-free copper of 99.9 wt% or more of purity can be used, and a well-known copper alloy can be used according to the requested | required strength and electroconductivity.

Oxygen-free copper is standardized by JIS-H 3510 (alloy number C1011) and JIS-H 3100 (alloy number C1020), and tough pitch copper is standardized by JIS-H 3100 (alloy number C1100).

As a known copper alloy, it is 0.01? 0.3 wt% tin-containing copper alloy (more preferably 0.001-0.02 wt% tin-containing copper alloy); 0.05 wt% of silver-containing copper alloys; 0.02 wt% indium-containing copper alloys; 0.02 wt% chromium-containing copper alloys; copper alloys containing 0.05 wt% or less in total of at least one selected from the group consisting of tin, silver, indium and chromium, among which Cu-0.02 is excellent in conductivity. wt% Ag is commonly used.

Next, an example of the manufacturing method of the rolled copper foil of this invention is demonstrated. First, after the hot rolling of the ingot which consists of copper and the necessary alloy element and also an unavoidable impurity, cold rolling and annealing are repeated, and finally it finishes to predetermined thickness by final cold rolling.

Here, as described above, the surface of the copper foil is roughened immediately in front of the final pass of the final cold rolling, and the surface of the copper foil is roughened by roughening the surface of the copper foil in the final pass of the final cold rolling, but the shear deformation It becomes the surface state which has the oil pit which is hard to develop as soon as possible, and there is little dishdown. And in the surface with few such shear deformation zones, the area ratio of an oil pit will be 6 to 15%.

Therefore, immediately before the final pass of the final cold rolling, the surface of the copper foil is rolled using a roll having a relatively small roughness (surface roughness (Ra), for example, 0.05 µm or less), or used for final cold rolling. What is necessary is just to enlarge the 1-pass workability in rolling. On the other hand, in the final pass of final cold rolling, the roughness (surface roughness Ra is 0.06 micrometer or more) is rolled using a comparatively large roll, or it rolls using the rolling oil with high viscosity, and finally obtains the copper foil surface Roughen

In addition, in order to create a surface state having an oil pit that roughens the surface of the final copper foil but is difficult to develop as a shear strain, in the last two passes or the final pass of the final cold rolling, a coarse roll or a viscosity is used as described above. Although it is necessary to roll using high rolling oil, it is preferable to adjust the rolling conditions in a final pass from the point which is easy to adjust. On the other hand, if the roughness of the roll is roughened from before the last three passes of the final cold rolling, the shear deformation zone is further developed by processing the final pass on the formed oil pit.

Moreover, the average particle diameter of the recrystallized grain obtained by annealing just before final cold rolling is 5? What is necessary is just to adjust under annealing conditions so that it may become 20 micrometers. Moreover, what is necessary is just to make the rolling workability in final cold rolling into 98% or more.

Example

Ingots were cast using tough pitch copper or oxygen-free copper containing the elements of the composition shown in Table 1 as a raw material, and hot rolling was performed to 800 mm or more to a thickness of 10 mm, followed by cold rolling of the surface oxide scale. And annealing were repeated, and finally it finished to the thickness shown in Table 1 by final cold rolling. The rolling workability in final cold rolling was 99.2%.

In addition, "0.02% Ag addition TPC" in the composition column of Table 1 means that 0.02 mass% Ag was added to tough pitch copper (TPC) of JIS-H3100 (alloy number C1100). In addition, "0.01% Ag 0.005% Sn addition OFC" of the composition column of Table 1 is what added 0.01 mass% Ag and 0.005 mass% Sn to oxygen-free copper (OFC) of JIS-H 3100 (alloy number C1020). it means. However, only Example 6 uses oxygen-free copper (OFC) standardized in JIS-H 3510 (alloy number C1011) as oxygen-free copper, and Examples 4, 5, 8, and 9 use JIS-H 3100 (alloy-free) as oxygen-free copper. Oxygen-free copper (OFC), standardized under No. C1020), was used.

In addition, the final cold rolling is 10? It carried out in 15 passes and as shown in Table 1, it rolled by changing the surface roughness of the roll just before a final pass, and the surface roughness of the roll of a final pass. The surface roughness of the rolls from the first pass of the last pass to just before the final pass is all the same. In addition, the workability of final rolling was made into 99% other than the comparative example 5, and the comparative example 5 was 96%.

Thus, various characteristics were evaluated about each copper foil sample obtained.

(1) Surface roughness (Ra): Ra (center line average roughness) is measured according to JIS B 0601, and a sample surface is 175 micrometers in length in a rolling parallel direction using a confocal microscope (manufactured by Leisure Tech, model number: HD100D). It was set as the value measured at.

(2) cube assembly

After heating a sample for 30 minutes at 200 degreeC, the integral value (I) of the (200) surface intensity calculated | required by the X-ray diffraction of the rolled surface was calculated | required. The I / I0 value was calculated by dividing this value by the integral value (I0) of the (200) surface strength of fine powder copper (325 mesh, used after heating at 300 ° C. for 1 hour in a hydrogen stream).

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

Using a confocal microscope (manufactured by Leisure Tech, Model No .: HD100D), as shown in FIG. 3, the copper foil surface was 175 µm in length in the rolling parallel direction RD and 50 µm in the rolling right angle direction TD, respectively. The difference di between the maximum height H _M and the minimum height H _S on the three straight lines L _{1 to} L ₃ separated from each other was determined. By taking the average of the di each straight line (L _1? L ₃₎ was set to d. In addition, it was set as d (mm) / t (mm).

(4) Difference in defense by EBSD

EBSD (backscattered electron beam diffractometer, Nippon Electronics Co., Ltd. JXA8500F, acceleration voltage 20 mA, current 2 e-8 A, measurement range 1000 μm × 1000 μm after electrolytic polishing of sample surface after heating at 200 ° C. for 30 minutes at (2) , Step width 5 µm). The area ratio of the crystal grains whose angle difference from the [100] orientation is 15 degrees or more was determined by image analysis. In addition, the number of things whose grain diameter exceeds 20 micrometers was visually counted within the observation range of 1 mm square of the sample surface. And the sample containing this observation range was etched for 2 minutes at normal temperature using the 20% solution of Adecatek CL-8 (made by Adeka Co., Ltd.), and the image which image | photographed the surface after etching with the optical microscope was taken. Darkness was binarized, and the dark part over 50 micrometers in diameter was counted as a dish down. In addition, the surface of copper foil after etching becomes a shape reflecting a crystal orientation, whereas a structure having a [100] orientation becomes a plane parallel to the surface of the copper foil, whereas other portions having a crystal orientation have irregularities resulting from the crystal orientation. Occurs. Thus, the portion of the dish down appears dark with the optical microscope.

4 shows the optical microscope image of the surface of Example 1, and FIG. 5 shows the surface optical microscope image of Comparative Example 3. FIG.

(4) area ratio of oil pit

The sample surface was measured about 300 x 300 micrometers of the measurement field | area with the confocal microscope (made by Leisuretech, model number: HD100D). The sample was moved in the optical axis (Z axis) direction within the measurement field of view, resulting in an image 10 nm deep from the surface of the copper foil (this is called a FMS (Focus Scan Memory) image). And the part deeper than 10 nm from the copper foil surface was regarded as an oil pit, and binarization process was performed. Examples of the image are FIGS. 6 and 7, and the light colored portion is an oil pit. And the area (bright area) of the oil pit was calculated | required about 300-300 micrometers of measurement visual fields, and the area ratio of the oil pit was calculated using commercially available image processing software.

(5) scratches on the surface

The surface of each sample was visually observed, and the case where there existed 5 or more points | pieces / m <2> or more in the rolling direction with the length of 10 mm or more was made into x.

(6) flexibility

After heating the sample at 200 degreeC for 30 minutes and recrystallizing, the bending fatigue life was measured with the bending test apparatus shown in FIG. This apparatus has a structure in which the vibration transmission member 3 is coupled to the oscillation drive body 4, and the copper foil 1 to be tested has a total of four points of the portion of the screw 2 and the tip of 3 indicated by the arrow. Is fixed to the device. When the vibrator 3 is driven up and down, the intermediate portion of the copper foil 1 is bent in a hairpin shape at a predetermined radius of curvature r. In this test, the number of times to break when bending was repeated under the following conditions was calculated | required.

In addition, when plate | board thickness is 0.012 mm, test conditions are as follows: Test piece width: 12.7 mm, Test piece length: 200 mm, Test piece collection direction: The sampling and curvature radius (r are made so that the longitudinal direction of a test piece may be parallel to a rolling direction. ): 2.5 mm, vibration stroke: 25 mm, vibration speed: 1500 times / minute. In addition, it was judged to have excellent flexibility when the bending fatigue life was 30,000 times or more.

In addition, when the sheet thickness was 0.018 mm and 0.006 mm, respectively, the curvature radius r was changed to 4 mm and 1.3 mm so that the bending test and the bending deformation at the plate thickness of 0.012 mm may be the same, but other tests The conditions were the same.

The obtained results are shown in Table 1.

As is apparent from Table 1, for each example where I / I ₀ ≥ 50, d / t is 0.1 or less, and the oil pit area ratio is 6 or more and 15% or less, the angle difference from the [100] orientation by EBSD is The area ratio of the crystal grains which is 15 degrees or more became less than 20%, the number of dish downs was small, there was no damage to the copper foil surface, and the flexibility was also excellent. Moreover, in the case of each Example, Ra / t of the final product became 0.004 or more and 0.007 or less.

On the other hand, in Comparative Examples 1 and 5 in which the surface roughness of the rolls of all the passes (including the final pass) of the final cold rolling were all Ra = 0.04 µm or less, Ra / t of the final pass was less than 0.004, Since the area ratio was less than 6%, scratches occurred on the copper foil surface, resulting in poor handleability.

In addition, in the case of the comparative example 5, although the surface roughness was small and the area ratio of the oil pit is less than 6%, since the rolling workability in final cold rolling was made low as 96%, I / I0 _. It became <50 and the orientation degree was low, and it became the state which crystal orientation did not correspond. When the crystal orientations do not coincide, it means that there are many crystal grains whose angle difference from the [100] orientation is 15 degrees or more, and since the area ratio of the crystal grains exceeds 20%, many dish downs also occur.

In the final cold rolling, in the case of Comparative Example 2 in which the surface roughness of the roll just before the final pass was roughened to Ra = 0.06 m or more, and the surface roughness of the roll of the final pass to Ra = 0.05 m or less, Ra of the final product Since / t was smaller than 0.004, a scratch was generated on the surface of the copper foil, resulting in poor handleability. In addition, since a rough roll was used immediately before the final pass, the shear deformation zone developed in the oil pit, and even when a small roughness roll was used in the final pass, the shear deformation zone remained, and the area ratio of the oil pit was less than 6%. Therefore, the area ratio of the crystal grain whose angle difference from a [100] orientation is 15 degrees or more exceeded 20%. As a result, many dish downs occurred.

In the final cold rolling, in the case of Comparative Examples 3, 4 and 6 in which both the surface roughness of the roll just before the final pass and the surface roughness of the roll of the last pass were roughened to Ra = 0.06 µm or more, Ra / t became 0.004 or more, and many oil pits in which the shear deformation zone developed before the final pass occurred. For this reason, the oil pit area ratio exceeded 15% after the last pass, and the area ratio of the crystal grain whose angle difference from a [100] orientation is 15 degrees or more exceeded 20%. As a result, many dish downs occurred.

In addition, in Comparative Examples 3 and 4, since the roll surface roughness of all the passes of the final cold rolling was roughened, many oil pits in which the shear deformation zone was remarkably developed occurred in the material. For this reason, not only oil pit area ratio exceeds 15%, but the orientation of the crystal | crystallization of the copper foil surface falls, and I / I0 _. <50. Therefore, the area ratio of the crystal grains whose angle difference from a [100] orientation is 15 degrees or more exceeded 20%. On the other hand, in the case of Comparative Example 6, since the roughness of the roll just before the final pass was made smoother than Comparative Examples 3 and 4, I / I ₀ Became 50 or more, it became a value higher than the comparative examples 3 and 4, and the flexibility was favorable.

Claims (3)

The surface roughness (Ra) and the ratio (Ra / t) of the thickness (t) of the copper foil, measured at a length of 175 μm in the rolling parallel direction on the surface of the copper foil, are 0.004 or more and 0.007 or less, and are heated at 200 ° C. for 30 minutes for recrystallization. In the roughened state, the intensity (I) of the (200) plane determined by the X-ray diffraction of the rolled surface is I / I with respect to the intensity (I ₀ ) of the (200) plane determined by the X-ray diffraction of fine powder copper. I ₀ ≥ 50,
The difference between the maximum height and the minimum height in the thickness direction of each straight line corresponding to the maximum depth of the oil pit on three straight lines that are 175 μm in length in the rolling parallel direction and 50 μm or more apart in the rolling right direction on the copper foil surface. The ratio (d / t) of the average value (d) and the thickness t of the said copper foil is 0.1 or less,
The rolled copper foil whose area ratio of the oil pit when measured with a confocal microscope is 6% or more and 15% or less. The method of claim 1,
The rolled copper foil whose area ratio of the crystal grain whose angle difference from a [100] orientation is 15 degrees or more is observed when the copper foil surface after the said 200 degreeC x 30-minute heat processing is observed by EBSD after electropolishing. The method according to claim 1 or 2,
After the hot rolling of the ingot, cold rolling and annealing are repeated, and finally, the final cold rolling is carried out. In the final cold rolling process, Ra / t is 0.002 or more and 0.004 or less in the stage before the final pass.

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