JP5127082B2 - Rolled copper foil - Google Patents

Description

  The present invention relates to a rolled copper foil that is suitably used for an FPC that requires flexibility.

  High flexibility is required for the copper foil used in the FPC (flexible printed circuit board) for bending. 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), and increasing the proportion of crystal grains penetrating in the thickness direction of the copper foil (Patent Document 2), and a technology (Patent Document 3) for reducing the surface roughness Ry (maximum height) corresponding to the depth of the oil pit of the copper foil to 2.0 μm or less is known.

A general FPC manufacturing process is as follows. First, the copper foil is bonded to the resin film. For joining, there are a method of imidizing by applying heat treatment to a varnish applied on a copper foil, and a method of laminating a resin film with an adhesive and a copper foil. The copper foil with a resin film joined by these steps is referred to as CCL (copper-clad laminate). The copper foil is recrystallized by the heat treatment in the CCL manufacturing process.
By the way, when manufacturing the FPC using the copper foil, if the copper foil surface is etched in order to improve the adhesion to the coverlay film, a dent (dish down) having a diameter of about several tens of μm may occur on the surface. . This is because, when the crystal orientation is controlled to the (200) plane so that a cubic structure develops after recrystallization annealing, the entire surface has a uniform etching rate, whereas crystal grains having locally different crystal grain orientations. It is considered that when this is present, only that portion has an etching rate different from that of the surrounding area, resulting in a locally deep recess. This dent causes the circuit etchability to deteriorate, or causes the appearance to be judged to be defective in the appearance inspection.

As a method for reducing such dents, a technique (Patent Document 4) for recrystallization after mechanically polishing the surface of the copper foil before or after rolling to give strain that becomes a work-affected layer is reported. . According to this technique, non-uniform crystal grains are clustered on the surface after recrystallization by the work-affected layer, so that crystal grains having different crystal orientations do not exist alone.
On the other hand, the present applicant appropriately smoothes the surface of the copper foil to reduce the above-described dents, while smoothing the surface of the copper foil to prevent side slipping during foil passing, etc. A technique for making the surface roughness Ras rougher than the surface roughness Rap in the rolling parallel direction has been reported (Patent Document 5).

Japanese Patent No. 3009383 JP 2006-117777 A JP 2001-058203 A JP 2009-280855 A JP 2010-227971 A

However, in the case of the technique described in Patent Document 4, there are many non-uniform crystal grains, and crystals on the surface of the copper foil are not oriented in the (200) plane.
On the other hand, in order to ensure adhesion with the roll during the manufacture of copper foil and to facilitate the handling of copper foil products, the roll roughness in the final cold rolling can be increased to roughen the copper foil surface. However, if the surface of the copper foil is roughened, the degree of crystal orientation on the surface of the copper foil is lowered, resulting in poor flexibility and dishdown. Therefore, in the above-mentioned Patent Document 5, the surface roughness Raroll of the rolling roll in the final cold rolling is set to 0.05 to 0.15 μm and the oil film equivalent is less than 30000 in order to make the copper foil surface moderately smooth. (Paragraph 0014 of Patent Document 5). However, it has been found that when a copper foil is produced by this production method, the surface is likely to be scratched during handling (see “Reference Examples” in Examples described later).
That is, the present invention has been made to solve the above problems, and even if the surface of the copper foil is appropriately roughened in order to improve the handleability, the flexibility is not deteriorated and the surface is scratched. An object of the present invention is to provide a rolled copper foil that is difficult and has good surface etching characteristics.

As a result of various investigations, the present inventors have found that the surface of the copper foil is not so rough (for example, rolled with a roll having a low roughness) before the final cold rolling pass, and the final cold rolling is performed in the final pass. By roughening the surface of the copper foil (for example, rolling with a rough roll, that is, the final pass of the final cold rolling and changing the roughness of the rolling roll before that), the surface of the final copper foil is roughened However, the present inventors have found that the shear band does not reach deep in the thickness direction of the copper foil, the dishdown is reduced without deteriorating the flexibility, and the surface is hardly damaged when the copper foil is handled.
In order to achieve the above object, the rolled copper foil of the present invention has a ratio Ra / t between the surface roughness Ra measured at a length of 175 μm in the rolling parallel direction on the copper foil surface and the thickness t of the copper foil. A cross section having a length of 0.004 or more and 0.007 or less and a thickness t of the copper foil of 50 μm or less and a length of 25 μm along the parallel direction of rolling of the copper foil is produced using a focused ion beam. When the scanning ion microscope image is observed, the average value Lsa of Ls of the reach depth of the shear band in the thickness direction of the copper foil is 0.01 ≦ Lsa / t ≦ 0 with respect to the thickness t of the copper foil. Satisfies the relationship of .4.

The strength (I) of the (200) plane determined by X-ray diffraction of the rolled surface was determined by X-ray diffraction of finely powdered copper (200) in a state where the recrystallized structure was tempered by heating at 200 ° C. for 30 minutes (200 ) With respect to the surface strength (I ₀ ), I / I ₀ ≧ 50, and on the three straight lines that are 175 μm in length in the rolling parallel direction on the surface of the copper foil and 50 μm or more apart from each other in the direction perpendicular to the rolling direction. The ratio d / t between 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 oil pit and the thickness t of the copper foil is 0.1 or less. Is preferred.

  Furthermore, when the copper foil surface 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 the [100] orientation is 20% or less. . The “further heat treatment at 200 ° C. for 30 minutes” referred to here refers to heat treatment again when the heat history of heating at 200 ° C. for 30 minutes has already been received.

In the final cold rolling step after cold rolling and annealing are repeated at least once after the ingot is hot-rolled, the surface roughness of the rolling roll before the final pass is determined as the surface roughness of the rolling roll in the final pass. It is preferable to make it smoother. Here, the surface roughness of the rolling roll is the centerline average roughness defined in JIS B0601.
In the final cold rolling step after cold rolling and annealing are repeated at least once after the ingot is hot rolled, Ra / t is 0.002 or more and 0.004 or less before the final pass. It is preferable.

  According to the present invention, the surface of the copper foil is appropriately roughened to improve the handleability, and further excellent in flexibility, the surface of the copper foil is hardly scratched during handling of the copper foil, and the rolled copper foil has good surface etching characteristics. Is obtained.

It is a figure which shows the relationship between the roughness of a copper foil surface, and a shear band. It is a schematic diagram of the structure of the cross section along the rolling parallel direction of copper foil. It is a figure which shows the measuring method of the average value d equivalent to the maximum depth of an oil pit. FIG. 3 is a diagram showing an optical microscope image of Example 1. 10 is a diagram showing an optical microscope image of Comparative Example 3. FIG. It is a figure which shows the EBSD measurement result of Example 1. It is a figure which shows the EBSD measurement result of the comparative example 3. It is a figure which shows the cross-sectional SIM image of the copper foil sample of Example 2. FIG. It is a figure which shows the cross-sectional SIM image of the copper foil sample of the comparative example 3. FIG. It is a figure which shows the cross-sectional SIM image of the copper foil sample of the comparative example 6. It is a figure which shows a bending test method.

  Hereinafter, the rolled copper foil which concerns on embodiment of this invention is demonstrated. In the present invention, “%” means “% by mass” unless otherwise specified.

First, the technical idea of the present invention will be described with reference to FIG. When the roll roughness in the final cold rolling is increased to roughen the copper foil surface, the handleability of the copper foil is improved, but dishdown is likely to occur (conventional example 1 in FIG. 1).
It was found that the occurrence of dishdown was caused by cold rolling with a rough roll to introduce irregularities on the surface of the copper foil and further develop a deep shear band in the thickness direction. That is, when the crystal orientation is controlled so that a cubic structure is developed by recrystallization annealing, the developed shear band becomes the starting point of crystal grains having crystal grain orientations that are locally different from the surroundings. Since the crystal grains have an etching rate different from that of other crystal grains, the etching results in a deep recess locally compared to the surrounding area.

The mechanism by which the developed shear band generates crystal grains having grain orientations that are locally different from the surroundings is as follows.
First, a material that has been subjected to a shearing force during the rolling process of the material is deformed by the slip deformation of the crystal. However, if the strain increases as the rolling process proceeds, the material cannot be deformed only by the slip deformation, and the material is deformed by the shear deformation. I will go. Since this shear (deformation) band shears the crystal grains, the crystal grains are divided by the shear band. Furthermore, since the shear band is a structure in which strain is accumulated due to deformation, the driving force for generating new crystal grains during recrystallization annealing is high. Therefore, even if the (200) plane develops in the crystal grains around the shear band during annealing, it is considered that crystal grains having random orientations are generated in the shear band. A structure in which strains are accumulated as compared to the surrounding structure such as a shear band is not preferable because the degree of orientation of the entire material (200) plane is lowered.

  The shear band is a structure that shears crystal grains, and when observed from a cross section along the rolling parallel direction, the crystal grains are continuously divided at a predetermined depth in the thickness direction. Remains without being divided in the thickness direction. In the present invention, as will be described in detail later, the cross section is prepared using FIB (focused ion beam), and a shear band is determined by observing a SIM (scanning ion microscope) image of the cross section.

Here, the shear band is mainly formed by unevenness (indentations, oil pits, etc.) on the surface of the copper foil, and when the copper foil receives a shearing force, the unevenness becomes a bottleneck for material deformation. Deformation occurs as a starting point, and shear deformation tends to occur. Therefore, even in a relatively early stage of rolling, a shear band may develop in the depth direction immediately below such irregularities.
For this reason, a technique for reducing the surface roughness in order to obtain the flexibility of the copper foil is conventionally known. This is considered to be because the final cold rolling is performed with a roll having low roughness, thereby reducing the unevenness of the surface that is the starting point of the shear band, making it difficult for the shear band to occur in the thickness direction of the copper foil. However, when the surface roughness of the copper foil is reduced, the handleability of the copper foil is lowered (conventional example 2 in FIG. 1).

From the above, the present inventors change the surface roughness of the rolling roll before the final pass of the final cold rolling, that is, before the final pass of the final cold rolling, the surface of the copper foil is not so rough. (For example, rolling with a low-roughness roll) and roughening the surface of the copper foil in the final pass of the final cold rolling (for example, rolling with a rough roll), the final copper foil surface is roughened However, it has been found that the generation and development of shear bands can be suppressed, dishdown is reduced, and scratches are hardly generated on the surface when the copper foil is handled (example of the present invention in FIG. 1).
In other words, conventionally, the orientation of the copper foil has been thought to depend solely on the roughness of the copper foil surface, but in reality it does not only affect the roughness of the surface, but rather the size of the shear band inside the material. It was found that (development) affects the orientation (and dishdown). In the final cold rolling, if the material surface roughness can be suppressed sufficiently smoothly in the pass before the final pass, high orientation can be obtained even if the copper foil surface is finished rough in the final pass.

Here, the number of dishdowns does not necessarily correlate with the surface roughness. This is because a shear band does not necessarily exist immediately below the irregularities on the surface of the copper foil (see FIG. 8). Therefore, the depth of the unevenness on the surface of the copper foil itself does not determine the degree of development of the shear band. However, as described above, when the final cold rolling is performed with a roll having low roughness and the surface roughness of the copper foil is reduced, the degree of development of the shear band is suppressed, so the surface roughness and the number of dishdowns Is somewhat correlated.
However, in the present invention, since the surface of the copper foil is appropriately roughened, it is necessary to control (specify) the shear band itself, not the surface roughness of the copper foil.

Therefore, the present inventor directly specifies the degree of development of the shear band by the following index, thereby improving the flexibility of the copper foil having a moderately rough surface, suppressing the occurrence of dishdown, and copper. Succeeded in suppressing scratches on the surface when handling the foil.
(1) Degree of development of shear band As an indicator of the degree of development of the shear band, the average value Lsa of the reach depth Ls of the shear band in the thickness direction of the copper foil as shown in FIG. On the other hand, the relationship of 0.01 ≦ Lsa / t ≦ 0.4 is satisfied. Note that Lsa (mm) / t (mm).
FIG. 2 is a schematic diagram of the structure of a cross section along the rolling parallel direction and having a length of 25 μm in the rolling parallel direction RD of the copper foil. Three irregularities 4 are formed on the copper foil surface 2 a, and a shear band 10 extends in the thickness direction directly below the outer two irregularities of the irregularities 4. Here, the symbol G represents a crystal grain, and the crystal grain G is a region surrounded by a grain boundary GB. The shear band 10 divides the crystal grains continuously in the thickness direction, but the grain boundary of the crystal grains not divided is the end of the shear band, and the depth in the plate thickness direction from the copper foil surface 2a to the end. Is defined as the reaching depth Ls of the shear band.
Incidentally, P _1, the crystal grains are separated by a shear band 10, showing a portion shifted the grain boundary GB. Further, P _2, the crystal grains are not divided by the shear bands 10, shows a portion not shifted grain boundary GB, the position of the end of the shear zone. In this manner, Lsa is obtained by averaging Ls of each shear band observed in one visual field shown in FIG. 2, and similarly, the average value of Lsa obtained by observing the cross section of three visual fields is defined as Lsa. adopt.

In addition, 1) The shear band is directly under the unevenness, 2) The shear band is almost straight, and it does not break or bend in the middle, and does not appear again after being interrupted. 3) The surface where the contrast of crystal grains is different is interfaced. In this case, both the shear band and the crystal grain boundary are visible at the interface in the metal structure observation.
The difference between the shear band and the crystal grain boundary is that the grain boundary of the rolled material exists so as to surround one crystal grain, whereas the shear band is a straight line that continuously divides a plurality of crystal grains, and It exists in a certain angle with respect to a rolling parallel direction. In addition, when it is difficult to distinguish the end of a straight line extending from the projections and depressions, the end can be a point at which the crystal grains are interrupted, that is, a point that abuts on a crystal grain having a single contrast.

  Further, as a method satisfying the relationship of 0.01 ≦ Lsa / t ≦ 0.4, the surface of the copper foil is not made very rough before the final pass of the final cold rolling (for example, the surface roughness Ra is 0, for example). And rolling the surface of the copper foil in the final pass of the final cold rolling (for example, rolling with a rough roll having a surface roughness Ra of, for example, 0.06 μm or more). Is mentioned.

During recrystallization annealing, it is difficult to align the crystal orientation of the (200) plane around the shear band, and it is easy to generate crystal grains having an orientation different from the orientation of the (200) plane. It is related to the reaching depth Ls. Therefore, by controlling so as to satisfy the relationship of 0.01 ≦ Lsa / t ≦ 0.4, the depth of the shear band becomes entirely shallow, and crystal grains having an orientation different from the orientation of the (200) plane Is suppressed and dishdown is reduced. On the other hand, in the case of Lsa / t> 0.4, the shear band is deep, many crystal grains having an orientation different from the orientation of the (200) plane are generated, and many dishdowns are generated.
The reason why the ratio of Lsa / t to the plate thickness t is because the influence of the depth of the shear band differs depending on the plate thickness. Further, Lsa / t is preferably as small as possible, but the lower limit of Lsa / t is set to 0.01 from the viewpoint of practical production conditions of the copper foil.

In the present invention, a cross-section of the copper foil is prepared using a focused ion beam, and a scanning ion microscope image of the cross-section is observed to determine the reaching depth Ls of the shear band.
FIB (focused ion beam) can be finely processed, and a flat cross section can be obtained. A SIM (scanning ion microscope) image is a secondary electron emitted when a sample is scanned with a focused ion beam. Since the contrast of the composition and crystal orientation is stronger than that of an SEM image, the crystal is divided by a shear band. Grains can be distinguished with high accuracy. As FIB for producing a cross section, a Ga + ion beam can be used.
Further, in the present invention, two adjacent regions having a difference in contrast due to the SIM image are regarded as different crystal grains, and these boundaries are regarded as grain boundaries. And the part which the grain boundary just under the unevenness | corrugation 4 of the copper foil surface 2a has shifted | deviated to RD direction is considered as the shear band 10, and this shift | offset | difference is connected in the thickness direction of copper foil. The position where the grain boundaries of RD direction deviation is no longer seen as a terminating P ₂ of shear bands, the distance in the thickness direction of the copper foil surface 2a to P ₂ and Ls.

FIGS. 8-10 shows the cross-section SIM image of the copper foil sample of the Example and comparative example which are mentioned later. In FIG. 8, it can be seen that among the four irregularities 4, there are those in which the shear band 10 extends immediately below the irregularities and those in which no shear band occurs immediately below the irregularities. Further, it is possible to discriminate a portion (shear band) where the grain boundary just below the unevenness 4 is shifted in the RD direction from the contrast difference of the cross-section SIM image.
In the cross-sectional image of FIG. 8 described above, a tangent line L is drawn to two protrusions surrounding the depression A recessed from the copper foil surface 2a from the left and right, and the distance in the thickness direction between L and A is 0.1 μm or more. Concave and convex 4

Next, other rules and compositions of the rolled copper foil of the present invention will be described.
(2) Ra / t
Ra / t which is the ratio of the surface roughness Ra (mm) after the final cold rolling and the thickness t (mm) of the copper foil in order to reduce dishdown while moderately roughening the copper foil surface. Is defined as 0.004 or more and 0.007 or less. If it does in this way, dishdown can be reduced, making surface roughness equivalent to the conventional copper foil. In addition, by dividing the surface roughness by the thickness, the roughness of the copper foil surface can be evaluated regardless of the thickness of the copper foil. On the other hand, when Ra / t is less than 0.004, the surface of the copper foil becomes too smooth, and the surface is easily scratched when the copper foil is handled. When Ra / t exceeds 0.007, the surface of the copper foil becomes too rough, the degree of crystal orientation on the surface of the copper foil is lowered, the flexibility is inferior, and dishdown is likely to occur.
Here, the surface roughness Ra (centerline average roughness) is defined in JIS B0601, and in the present invention, the copper foil surface has a length of 175 μm in the rolling parallel direction and is separated by 50 μm or more in the direction perpendicular to the rolling. The average value of the values measured on the straight line. In the present invention, the surface roughness can be measured using a contact surface roughness meter (SE-3400, manufactured by Kosaka Laboratory). In addition, all the copper foil surfaces and the surface roughness of a rolling roll shall be the said centerline average roughness.

(3) d / t
Even when the roughness of the copper foil surface is not so great and many of the oil pits are considered to have less developed shear bands, there may be some deep oil pits. In the deep oil pit, there is a high possibility that a shear band has developed, and in this case, it becomes the starting point of the occurrence of dishdown. Therefore, in the present invention, the average value d (mm) of the maximum depth of the oil pit is defined as d / t ≦ 0.1.
By dividing the average value d (mm) of the maximum depth of the oil pit by the thickness t (mm), the copper foil surface can be evaluated regardless of the thickness of the copper foil. That is, even if the maximum depth of the oil pit is the same, the influence becomes large as the thickness t (mm) of the copper foil is reduced.
Here, the average value d (mm) of the maximum depth of the oil pits is three as shown in FIG. 3 which is 175 μm long in the rolling parallel direction RD and 50 μm or more apart in the rolling perpendicular direction TD on the copper foil surface. on the straight line _L 1 ~L _3, the average value of the difference di (mm) of the maximum height _{H M} and a minimum height _{H S} in the thickness direction of the straight line _L 1 ~L ₃ corresponding to the maximum depth of the oil pit It is. Specifically, the profile in the thickness direction on L _{1 to} L ₃ is measured by contact-type roughness to obtain the maximum height H _M (mm) and the minimum height H _S (mm), and each straight line L ₁ the di of ~L ₃ should be average.
In addition, as in Comparative Example 2 to be described later, dishdown may occur even when d / t ≦ 0.1.
Although the thickness in particular of copper foil (or copper alloy foil) is not restrict | limited, For example, the thing of 5-50 micrometers can be used conveniently.

(4) I / I ₀
In order to impart high flexibility to the copper foil of the present invention, the strength of the (200) plane (I) determined by X-ray diffraction of the rolled surface in a state of heating to 200 ° C. for 30 minutes and tempering the recrystallized structure. ) Is defined as I / I ₀ ≧ 50 with respect to the strength (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 increased. When I / I ₀ <50, the flexibility decreases. The annealing at 200 ° C. for 30 minutes imitates the temperature history given to the copper foil in the CCL manufacturing process. The value of I / I ₀ can be measured with a general X-ray diffraction measuring device. For example, it can measure using RINT2500 (made by Rigaku Corporation). In addition, a generally used element (for example, Cu, Co, etc.) may be used for the X-ray source.
In order to satisfy I / I ₀ ≧ 50, the workability of the final cold rolling is preferably 90% or more, and more preferably 95% or more. Further, it is further desirable that the workability of the final cold rolling is 98% or more.

(5) Orientation difference due to EBSD When the copper foil surface is observed by EBSD after electrolytic polishing in a state where it is heated at 200 ° C. for 30 minutes to be recrystallized, the angle difference from the [100] orientation is 15 degrees. The area ratio of the crystal grains is preferably 20% or less. The annealing at 200 ° C. for 30 minutes imitates the temperature history given to the copper foil in the CCL manufacturing process. In addition, you may heat for 30 minutes at 200 degreeC also about the copper foil which became CCL which has already received thermal history. The one that has been heat-treated until it is recrystallized does not change substantially even if it is heated further. Therefore, in observation observation with EBSD, the copper foil that has undergone the thermal history and the copper foil that has not received the heat are not distinguished. It was decided to heat for 30 minutes.
When the area ratio is less than 20% when observed by EBSD, the orientation difference between the crystal grains on the copper foil surface is small, and the proportion of crystal grains having different crystal orientations in a uniform structure is small. As a result, dents (dish down) due to etching are reduced, and scratches are unlikely to occur on the surface of the copper foil during handling. In order to reduce the area ratio to less than 20% when observed by EBSD, as described above, in the final cold rolling, the material surface roughness is sufficiently smoothed in the pass before the final pass, that is, the final cool What is necessary is just to roll using a roll with comparatively small roughness (surface roughness Ra is 0.05 micrometer or less) by the pass before the last pass of a hot rolling.

(6) Composition As the copper foil, tough pitch copper or oxygen-free copper having a purity of 99.9% or more can be used, and as the copper alloy foil, a known copper alloy can be used depending on the required strength and conductivity. Can be used. Known copper alloys include, for example, 0.004 to 0.3% tin-containing copper alloy, 0.004 to 0.05% silver-containing copper alloy, In, Zn, Zr, Ti, Fe, P, Ni , Si, Sn, Ag, Te, Cr, Nb, and a copper alloy containing 0.004 to 0.5% in total of one or more elements of V, etc. are mentioned. 02% silver-added copper is often used.
Thus, the rolled copper foil of this invention contains the alloy of the said composition other than pure copper type like tough pitch copper and oxygen-free copper.

Next, an example of the manufacturing method of the rolled copper foil of this invention is demonstrated. First, an ingot made of copper, necessary alloy elements, and inevitable impurities is hot-rolled, and then cold-rolling and annealing are repeated, and finally, it is finished to a predetermined 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 final copper is roughened by roughening the surface of the copper foil in the final pass of the final cold rolling. Although the surface of the foil is rough, it becomes a surface state having oil pits which are difficult to develop in the shear band, and dishdown is reduced. And the surface ratio with such few shear bands has an oil pit area ratio of 6 to 15%.

Therefore, before the final pass of the final cold rolling, the surface of the copper foil is rolled by using a roll having a relatively small roughness (surface roughness Ra is, for example, 0.05 μm or less) What is necessary is just to roll by increasing the 1 pass processing degree in cold rolling. On the other hand, in the final pass of the final cold rolling, rolling is performed using a roll having a relatively large roughness (surface roughness Ra is, for example, 0.06 μm or more), or rolling is performed using a rolling oil having a high viscosity. The surface of the copper foil obtained is roughened.
In addition, in order to create a surface state having oil pits that are rough on the surface of the final copper foil but are difficult to develop in the shear band, as described above, in the final two passes of the final cold rolling, or the final pass Although it is necessary to use a rough roll or a rolling oil with high viscosity, it is preferable to adjust the rolling conditions in the final pass because it is easy to adjust. On the other hand, when the roughness of the roll is made rough before the final three passes of the final cold rolling, a shear band is further developed in the formed oil pit by the processing of the final pass.

  In addition, it is good to adjust annealing conditions so that the average particle diameter of the recrystallized grain obtained by annealing immediately before final cold rolling may be 5-20 micrometers. Further, the rolling degree in the final cold rolling is preferably 90% or more.

After casting an ingot using copper or a copper alloy having the composition shown in Table 1 as a raw material, hot rolling up to a thickness of 10 mm at 800 ° C. or higher, and chamfering the oxide scale on the surface, cold rolling and annealing are performed. Repeatedly, finally, it was finished to a thickness of 0.009 to 0.018 mm by final cold rolling. The rolling degree in final cold rolling was set to 95 to 99.8%. In Table 1, tough pitch copper is described as TPC and oxygen-free copper as OFC. Oxygen-free copper is standardized by JIS-H0500 (C1011), and tough pitch copper is standardized by JIS-H0500 (C1100).
The final cold rolling was performed in 10 to 15 passes, and as shown in Table 1, rolling was performed while changing the surface roughness of the roll before the final pass and the surface roughness of the roll in the final pass. The surface roughness of the roll from the first pass of the final rolling to the front of the final pass is all the same.
In addition, as “Reference Examples 6 to 9”, according to the manufacturing method of Patent Document 5, copper foil samples were manufactured with the same surface roughness of the rolling roll before and after the final pass of the final cold rolling step. . Reference Examples 6 to 9 correspond to Examples 4, 1, 3, and 6 of Patent Document 5, respectively (see Table 1 of Patent Document 5).

Various characteristics of each copper foil sample thus obtained were evaluated.
(1) Shear band Using a focused ion beam (FIB), as shown in FIG. 2, a cross section having a length of 100 μm along the rolling parallel direction RD of the copper foil was prepared, and a scanning ion microscope image of the cross section was observed. Among the cross sections, four visual fields were observed with a length of 25 μm along the RD as one visual field. The method for discriminating the shear band is as described in FIG. The product name “N Vision 40” manufactured by SII Nano Technology Co., Ltd. was used as the FIB apparatus.
(2) Cube texture After heating the sample at 200 ° C. for 30 minutes, the integral value (I) of (200) plane strength obtained by X-ray diffraction of the rolled surface was obtained. This value is divided by the integrated value (I ₀ ) of the (200) plane strength of finely powdered copper (325 mesh, used after heating at 300 ° C. for 1 hour in a hydrogen stream) to obtain I / I ₀ The value was calculated.

(3) Maximum oil pit depth (average value d)
Using a confocal microscope (made by Lasertec, model number: HD100D), as shown in FIG. 3, three pieces having a length of 175 μm in the rolling parallel direction RD and 50 μm or more in the rolling perpendicular direction TD on the copper foil surface, respectively. The difference di between the maximum height H _M and the minimum height H _S on the straight lines L _{1 to} L ₃ was determined. The di of each of the straight lines L _{1 to} L ₃ was averaged to be d. In addition, it was set as d (mm) / t (mm).
(4) Orientation difference by EBSD EBSD (backscattered electron diffraction device, JEOL Ltd. JXA8500F, acceleration voltage 20 kV, current 2 × 10 ⁻⁸ A, measurement after electrolytic polishing of sample surface after heating in (2) The range was 1000 μm × 1000 μm and the step width was 5 μm). The area ratio of crystal grains having an angle difference of 15 degrees or more from the [100] orientation was determined by image analysis. And about the sample containing this observation range, etching was performed for 2 minutes at room temperature using a ADEKA TECH CL-8 (manufactured by ADEKA Corporation) 20% solution, and the image obtained by photographing the etched surface with an optical microscope was binarized. The dark part exceeding 50 μm in the minor axis was counted as a dishdown. The surface of the copper foil after etching has a shape reflecting the crystal orientation, and the structure having the [100] orientation is a plane parallel to the copper foil surface, while the portion having the other crystal orientation is the crystal orientation. Unevenness caused by Therefore, the dishdown portion looks dark with an optical microscope.
4 shows an optical microscope image of Example 1, and FIG. 5 shows an optical microscope image of Comparative Example 3. 6 shows the EBSD measurement result of Example 1, and FIG. 7 shows the EBSD measurement result of Comparative Example 3. 6 and 7, gray and black regions indicate crystal grains having an angle difference of 15 degrees or more from the [100] orientation.

(5) Scratches on the surface The surface of each sample was visually observed, and a case where there were 5 or more scratches / m ² having a length of 10 mm or more in the rolling direction was evaluated as x.
(6) Flexibility After the sample was recrystallized by heating at 200 ° C. for 30 minutes, the flex fatigue life was measured by a flex test apparatus shown in FIG. This apparatus has a structure in which a vibration transmitting member 3 is coupled to an oscillation driver 4, and a copper foil 1 to be tested is fixed to the apparatus at a total of four points including a screw 2 part indicated by an arrow and a tip part of 3. Is done. When the vibration part 3 is driven up and down, the intermediate part of the copper foil 1 is bent into a hairpin shape with a predetermined radius of curvature r. In this test, the number of times until breakage when bending was repeated under the following conditions was determined.
The test conditions are as follows: Specimen width: 12.7 mm, Specimen length: 200 mm, Specimen sampling direction: Collected so that the length direction of the specimen is parallel to the rolling direction, curvature radius r : 1.0 mm (when copper foil thickness t is 0.009 mm), radius of curvature r: 1.5 mm (when copper foil thickness t is 0.012 mm), radius of curvature r: 2.5 mm (of copper foil) (When thickness t is 0.018 mm), vibration stroke: 25 mm, vibration speed: 1500 times / minute.
In addition, when the bending fatigue life is 20,000 times or more, it has excellent bendability, the bending fatigue life is evaluated as 50,000 times or more, and the bending fatigue life is 20,000 times or more and less than 50,000 times. Evaluation was set as (circle), and bending fatigue life was made into evaluation x with less than 20,000 times.

(7) Surface roughness of the copper foil surface after etching (Ry)
In Comparative Examples 2 and 6 described later, the surface roughness (Ry) of the copper foil surface after etching was measured by the following method in order to clarify the effect of the present invention.
A sodium persulfate aqueous solution having a temperature of 50 ° C. and a concentration of 100 g / L was sprayed onto the sample surface at a pressure of 2 kg / cm 2, and etching was performed by reducing the thickness by about 9 μm in the depth direction. Then, according to JIS B0601, the maximum height (Ry) of the surface was calculated | required using the contact roughness meter. The reference length was 0.8 mm, and the measurement was performed in a direction parallel to the rolling direction. Ry was measured five times at different locations, and the maximum of the five measured values was determined.

  The obtained results are shown in Tables 1 and 2.

  As is clear from Table 1 and Table 2, in each example where Ra / t of the final product is 0.004 or more and 0.007 or less and Lsa / t ≦ 0.4, the number of dishdowns is small, Furthermore, the copper foil surface was not damaged and was excellent in flexibility. In each example, the area ratio of crystal grains having an angle difference from the [100] orientation by EBSD of 15 degrees or more was less than 20%.

  On the other hand, in the case of Comparative Example 1 where the surface roughness of the rolls in all the passes of the final cold rolling (including the final pass) is Ra = 0.04 μm or less, Ra / t of the final pass is less than 0.004. As a result, the surface of the copper foil was scratched and the handleability was poor.

In the case of Comparative Example 2 where the surface roughness of the roll before the final pass is roughened to Ra = 0.06 μm or more in the final cold rolling, and the surface roughness of the roll in the final pass is Ra = 0.05 μm or less. Since Ra / t of the final product was smaller than 0.004, the copper foil surface was scratched and the handling property was inferior. Further, since a rough roll was used before the final pass, the surface of the copper foil before the final pass became rough, and a shear band was formed even when a roll with a small roughness was used in the final pass. Therefore, although d / t was 0.1 or less, the value of Lsa / t exceeded 0.4. As a result, the area ratio of crystal grains having an angle difference of 15 degrees or more from the [100] orientation exceeded 20%, and many dishdowns occurred.
Moreover, in the case of the comparative example 2, the surface roughness (Ry) of the copper foil surface after an etching was 1.51 micrometer. From this, it was found that dishdown may occur frequently even if the value of Ry is small.

In the case of Comparative Examples 3, 4 and 5 in which the surface roughness of the roll before the final pass and the surface roughness of the roll in the final pass were both roughened to Ra = 0.06 μm or more in the final cold rolling, The Ra / t before one pass was 0.004 or more and the copper foil surface became rough, and a shear band developed after the final pass. Therefore, Lsa / t exceeded 0.4, and many dishdowns occurred. In addition, the area ratio of crystal grains having an angle difference from the [100] orientation of 15 degrees or more exceeded 20%.
In the case of Comparative Examples 3 and 4, since the roll surface roughness of all passes of the final cold rolling was increased, many oil pits in which a shear band was remarkably developed inside the material were generated. For this reason, not only Lsa / t exceeded 0.4, but also the degree of crystal orientation on the surface of the copper foil was reduced to I / I ₀ <50. Correspondingly, the area ratio of crystal grains having an angle difference of 15 degrees or more from the [100] orientation exceeded 20%. On the other hand, in the case of Comparative Example 5, since the roll roughness before the final pass was made smoother than Comparative Examples 3 and 4, I / I ₀ was 50 or more, which was higher than Comparative Examples 3 and 4. The flexibility was good.
Moreover, the surface roughness (Ry) of the copper foil surface after the etching of Comparative Example 5 was 2.49 μm.

8 to 10 show cross-sectional SIM images of the copper foil samples of Example 2, Comparative Example 3, and Comparative Example 6, respectively. It can be seen that the shear band 10 extends just below the irregularities 4. It can also be seen from the contrast difference in the cross-section SIM image that the portion (shear band) where the grain boundary just below the irregularities 4 is displaced in the RD direction can be determined. Furthermore, compared with Example 2 (FIG. 8), the comparative examples 3 and 4 have many deep shear bands 10, and the value of Lsa / t also becomes large.
8A to 10B, the reference symbol (a) indicates the cross-sectional SIM image itself, and the reference symbol (b) indicates that the determined shear band 10 is displayed on the cross-sectional SIM image.

Moreover, in the case of Reference Examples 6 to 9 in which the surface roughness of the rolling roll was the same before and after the final pass of the final cold rolling process, many dishdowns occurred in each case, and there were scratches on the surface. Conspicuous and poor handling.
In the case of Reference Example 6, since the surface roughness of the rolling roll is smooth (Ra = 0.05 μm) before and after the final pass of the final cold rolling step, Lsa / t is 0. Although Ra / t was less than 0.004, scratches on the surface were conspicuous.
On the other hand, in the case of Reference Examples 7 to 9, since the surface roughness of the rolling roll is rough before the final pass of the final cold rolling step and the final pass (Ra exceeds 0.05 μm), Lsa / t Was over 0.4, and scratches on the surface were conspicuous.

Claims (5)

The ratio Ra / t between the surface roughness Ra measured at a length of 175 μm in the rolling parallel direction on the copper foil surface and the thickness t of the copper foil is 0.004 or more and 0.007 or less, and the thickness of the copper foil t is 50 μm or less,
Using a focused ion beam, a cross section of 25 μm in length along the rolling parallel direction of the copper foil was prepared, and when a scanning ion microscope image of the cross section was observed, the depth reached by the shear band in the thickness direction of the copper foil The rolled copper foil in which the average value Lsa of Ls satisfies the relationship of 0.01 ≦ Lsa / t ≦ 0.4 with respect to the thickness t of the copper foil. The strength (I) of the (200) plane determined by X-ray diffraction of the rolled surface was determined by X-ray diffraction of finely powdered copper (200) in a state where the recrystallized structure was tempered by heating at 200 ° C. for 30 minutes ) For the surface strength (I ₀ ), I / I ₀ ≧ 50,
The maximum height and minimum height in the thickness direction of each straight line corresponding to the maximum depth of oil pits on three straight lines having a length of 175 μm in the rolling parallel direction on the copper foil surface and spaced apart by 50 μm or more in the direction perpendicular to the rolling direction. The rolled copper foil according to claim 1, wherein a ratio d / t between an average value d of height differences and a thickness t of the copper foil is 0.1 or less.   Furthermore, when the copper foil surface after heat treatment at 200 ° C. for 30 minutes is observed by EBSD after electrolytic polishing, the area ratio of crystal grains having an angle difference of 15 degrees or more from the [100] orientation is 20% or less. The rolled copper foil according to 1 or 2.   In the final cold rolling step after cold rolling and annealing are repeated at least once after the ingot is hot-rolled, the surface roughness of the rolling roll before the final pass is determined as the surface roughness of the rolling roll in the final pass. The rolled copper foil in any one of Claims 1-3 made smoother.   In the final cold rolling step after cold rolling and annealing are repeated at least once after the ingot is hot rolled, Ra / t is 0.002 or more and 0.004 or less before the final pass. The rolled copper foil in any one of Claims 1-3.