JP4704474B2 - Rolled copper foil with excellent bending resistance - Google Patents

Description

 The present invention relates to a rolled copper foil excellent in bending resistance that can be used particularly for a flexible printed wiring board (FPC).

A printed wiring board is manufactured by etching a copper foil of a substrate to form various wiring patterns, and connecting and mounting electronic components with solder. Copper foils are classified into electrolytic copper foils and rolled copper foils because of their production methods, and rolled copper foils having excellent bending resistance have been used favorably as copper foils for flexible substrates.
A flexible printed wiring board (hereinafter referred to as FPC) is used as a wiring material for electronic devices because it is thin and has excellent bendability. In addition, the FPC market continues to expand and grow in response to the downsizing, miniaturization and high functionality of electronic devices. FPC applications are expanding rapidly from conventional HDDs and digital cameras in recent years to LCDs and mobile phones, and are also being developed for automotive applications. Thus, there is a demand for the development of a rolled copper foil having further excellent bending resistance.

Looking at the advanced technology of FPC, first of all, there is a demand for products that narrow the bending diameter. In other words, the bending diameter has been rapidly reduced due to the reduction in size, height, and functionality of electronic devices. For example, as shown in Fig. 1, in mobile phones, not only the conventional α type hinges but also new foldings such as cranks and slide types have appeared, and FPCs require stricter bending and bending reliability than ever before. Has been.
FPC is required to be soft. Improvements in workability and space saving can be expected due to easy folding. Also, with FPC inside HDD, the softer the FPC driving force, the easier it is to reduce. As a result, power consumption can be reduced, which leads to power saving of HDD. Furthermore, in LCD applications, it can be expected to reduce failures due to springback when folded slightly. As the bending diameter becomes narrower in this way, the demand for soft FPC is increasing.

The finer FPC wiring density is advancing rapidly as electronic devices become more functional, multifunctional, and mobile. It is expected that the latest 30μm pitch will continue to be refined toward a further 20μm pitch. In the further refinement of FPC wiring, not only the development of polyimide and adhesives, but also the development of copper foil including surface treatment becomes important.
Due to the downsizing of electronic equipment and the influence of lead-free solder, the heat resistance requirements of FPC are further increasing. Looking ahead to the future in-vehicle FPC, it is expected that the required level of heat resistance will continue to rise.
The above is an outline of the future required characteristics of the rolled copper foil from the market perspective. In particular, due to the above-mentioned FPC technology trend, the reliability of bending of the rolled copper foil is a problem.

The following introduces the prior art. For example, when producing a rolled copper foil of tough pitch copper or oxygen-free copper, the average grain size was set to 30 μm or less in recrystallization annealing immediately before the final rolling, and then rolled and measured by X-ray diffraction of the rolled surface (200) , (220), (311), (111) plane diffraction intensity is 3 ≦ I ₍₂₀₀₎ / I _{0 (200)} ≦ 10, I ₍₂₂₀₎ / I _{0 (220)} ≦ 1, I ₍₃₁₁₎ / I _{0 (311)} ≦ 1, I ₍₁₁₁₎ / I _{0 (111)} ≦ 1 (I _(hkl) : X-ray diffraction integrated intensity of (hkl) plane measured on the rolling surface, I _{0 (hkl)} : Fine powder There is a proposal for a rolled copper foil which has been developed under the condition that satisfies the relationship of the X-ray diffraction integral intensity of the (hkl) plane measured with copper, and then has developed a cubic texture rolled at a final rolling degree of 93% or more (for example, patents) Although this itself has the aim of improving the flexibility, the effect is not necessarily expected, and there is a problem that the number of bending is not sufficient.

Moreover, in the rolled copper foil for flexible printed circuit boards, the strength I of the (200) plane determined by X-ray diffraction of the rolled surface is compared with the strength I ₀ of the (200) plane determined by X-ray diffraction of the fine powder. A technique for making a cubic texture with I / I ₀ > 20 is disclosed (see Patent Documents 2 and 3). These techniques have improved the flexing life, but since there is no focus on slip bands, it has been found that this alone does not always provide the desired high flexibility.
Each of the above techniques is intended to improve the flexibility, but there is a problem that a great improvement in flexibility cannot be expected because there is no attention to a slip band described later.
JP 2001-323354 A JP 2000-212661 A Japanese Patent No. 3009383

 This invention is made | formed in view of the above problems, The place made into the objective is providing the rolled copper foil excellent in the bending resistance which can respond to a flexible printed wiring board (FPC) especially. It is in.

As described above, the present application provides the following inventions.
1) Provided is a rolled copper foil having excellent bending resistance, characterized in that a slip band after bending the rolled copper foil has a structure in which 50% or more is formed on the surface of the rolled copper foil. 2) This slip band must have a structure that forms 80% or more on the surface of the rolled copper foil, and 3) it must have a structure that forms 90% or more of the slip band on the surface of the rolled copper foil. Is desirable. Moreover, it is preferable that the slip band structure formed at the time of bending is uniformly distributed over the entire surface of the copper foil. This invention exists in the point which discovered that a slip band was a parameter | index which shows the high flexibility of rolled copper foil directly. As a result, the number of flexures can be greatly increased as will be described later.

4) The integrated intensity (I ₍₂₀₀₎ ) of (200) plane obtained by X-ray diffraction on the surface of rolled copper foil after recrystallization annealing is the integrated intensity of (200) plane obtained by X-ray diffraction of fine powder copper. (I _{o (200)} ), I ₍₂₀₀₎ / I _{o (200)} > 40, and a rolled copper foil having excellent bending resistance that has a structure with an average crystal grain size exceeding 20 μm It is an effective organization to obtain. Thus, when the crystal grain size is large and the (200) plane is highly oriented, a slip band appears remarkably. In particular, 5) I ₍₂₀₀₎ / _{Io (200)} > 65 is desirable. Further, 6) It is more effective to have a structure with an average crystal grain size of 30 μm or more. This is because the larger the crystal grains, the more the crystal grain boundaries are reduced and the crystal orientation mismatch can be reduced.

When copper that has been rolled at a high workability is recrystallized and annealed, a cubic orientation develops as the recrystallized texture. The cube orientation is an orientation in which the <002> direction of the crystal is parallel to the rolling direction, the normal direction of the rolling surface, and the width direction. In this case, the {200} plane is present on the rolling surface (thinned surface). Orient. As the cube orientation develops, the existence ratio of the crystal grains having the cube orientation increases, and when the cube orientation is extremely developed, most crystal grains show the cube orientation.
In this case, since the crystal grains are oriented in the same direction, the structure is as if it were a single crystal, and the number of grain boundaries is reduced. Therefore, in the copper foil in which the cubic texture is developed, it is possible to obtain a suitable condition that the crystal grain size becomes large and the number of grain boundaries can be reduced.

The rolled copper foil of the present invention having the above structure and excellent in bending resistance is capable of achieving a bending frequency of 70000 or more in the IPC sliding bending test (bending radius: 1.5 mm) in the rolled copper foil 18 μm foil. it can. The present invention includes all of these.
As described above, when a copper foil for a flexible substrate having a developed cubic texture is used, the slip band formed on the surface of the copper foil is also an index of bending resistance. There is no prior art that the rolled copper foil in which such a slip band is formed can greatly improve the bending resistance.

 According to the present invention, it is possible to obtain an excellent effect that a rolled copper foil having excellent bending resistance that can be applied to a flexible printed wiring board (FPC) can be realized within a range of industrially acceptable manufacturing costs.

It is a figure which shows diversification of the hinge part of a mobile telephone. It is a figure which shows the IPC sliding bending test result at the time of changing a bending radius. It is a figure (SEM image) which shows the observation result of the copper foil surface slip band after bending. It is a figure which shows the IPC sliding bending test result of a 2 layer copper clad laminated board. It is a figure which shows the MIT refraction-resistant test result of a 2 layer copper clad laminated board. It is a figure which shows the IPC sliding bending test result of a copper clad laminated board at the time of changing a circuit width. It is a figure which shows distribution of the frequency | count of bending in the case of changing the kind of copper foil. It is a figure which shows the MIT refraction test result which investigated the influence of the rolling direction of copper foil. It is a figure which shows the IPC sliding bending test result of the copper foil in high temperature. It is a figure which shows the test result of the loop stiffness of copper foil.

The rolled copper foil currently produced is a wiring material for FPC having a certain degree of bending reliability, but a wiring material having higher bending properties is required.
Regarding the relationship between the bending radius and the number of sliding bends in the copper foil, if the bend radius is decreased, the strain applied to the copper foil is increased, so that the flexibility is lowered. Therefore, for example, the electrolytic copper foil has the lowest bendability, so that it is difficult to adapt to a product having a small bending radius. Even in the conventional (current) rolled copper foil having high bendability, if the bend radius is reduced, the number of bends is drastically reduced and it becomes very severe.
In FIG. 2, the test result of the bending frequency of the rolled copper foil of this invention (this invention rolled foil), an electrolytic copper foil, and the conventional (current) rolled copper foil is shown. As shown in FIG. 2, it can be seen that the number of bendings of the rolled copper foil of the present invention (the rolled foil of the present invention) is greatly improved as compared with the electrolytic copper foil and the conventional rolled copper foil. The slip band is an index that directly indicates the high flexibility of the rolled copper foil.

When producing a rolled copper foil having excellent bending resistance according to the present invention, the integral strength (I ₍₂₀₀₎ ) of the (200) plane obtained by X-ray diffraction on the surface of the rolled copper foil after recrystallization annealing is very small. The integrated intensity (I _{o (200)} ) of (200) plane determined by X-ray diffraction of powder copper is I ₍₂₀₀₎ / I _{o (200)} > 40, and the average crystal grain size exceeds 20 μm It is effective to form a slip band after bending the rolled copper foil. When the X-ray diffraction intensity (I) of the (200) plane parallel to the rolling surface and the X-ray diffraction intensity (Io) of the (200) plane of powdered copper (random orientation) are measured under the same conditions, the development of the cube texture Can be evaluated by the ratio I / Io of these X-ray diffraction intensities.

The development of the cube texture depends not only on the final cold rolling rate but also on the processing and heat treatment steps leading to the final cold rolling, the final annealing temperature, the chemical composition of copper, the impurity content, and the like. Therefore, in order to obtain the target I / Io value, it is necessary to determine the optimum final cold rolling ratio and the like in accordance with the raw material copper to be used and the processing process.
As the rolled copper foil, copper whose recrystallized aggregate structure has a cubic orientation can be used. Typical examples of this material include tough pitch copper and oxygen-free copper.
In general, copper added with alloying elements is not suitable because it inhibits the development of the cubic orientation. However, the addition of a small amount of an alloy element of about 0.1 wt%, such as tough pitch copper whose softening temperature is adjusted by adding Ag or the like, has no particular problem in use because it does not inhibit the development of the cube orientation.

(High flexibility mechanism of rolled copper foil)
The present inventor researched and developed various types of rolled copper foils in order to provide flex resistance that can be applied to flexible printed wiring boards (FPC). I found out there was a phenomenon. That is, a large amount of a bent slip band is generated on the surface of the rolled copper foil.
After bending the FPC of the rolled copper foil of the present invention (the present invention rolled foil), the result of observing the S-plane side of the copper foil circuit with an SEM image is shown in FIG. The upper structure (SEM image) in FIG. 3 is a case where the (200) orientation of the surface is 99% and I ₍₂₀₀₎ / I _{o (200)} = 75. A fine streak pattern was observed on the surface as compared with the portion other than the bent portion. The streak pattern shown in this figure is a so-called “slip band”. This is a phenomenon peculiar to a highly crystalline (single crystal) metal. In this case, slip bands occurred at 90% of the surface.

When a single crystal metal is repeatedly stressed, a slip band is generated on the metal surface in an attempt to alleviate the strain (dislocations) accumulated at the grain boundaries. The middle structure (SEM image) in FIG. 3 shows a case where the (200) orientation of the surface is 90% and I ₍₂₀₀₎ / I _{o (200)} = 10. In the middle diagram of FIG. 3, it can be observed that a slip band is partially generated. In this case, a slip band occurred at 35% of the surface. In this case, since a slip band is generated, slightly good bending resistance is shown, but it is not sufficient.
On the other hand, the lower structure (SEM image) in FIG. 3 is the case where the (200) orientation of the surface is 20% and I ₍₂₀₀₎ / I _{o (200)} <3. This is the case of the electrolytic copper foil, but the electrolytic copper foil hardly generates slip bands on the surface. As a result, it can be seen that even when repeated stress is applied in the same manner as the rolled copper foil, even cracks are generated.

Thus, the slip band occurs in the rolled copper foil because the rolled copper foil has high crystallinity like a single crystal and is highly oriented in the (200) plane. A slip band is produced later.
This is a phenomenon that alleviates fatigue accumulation inside the rolled copper foil during bending, and as a result, the rolled copper foil can have high flexibility. That is, if the slip band can be generated uniformly and in large quantities after the copper foil is bent, the bending resistance of the rolled copper foil can be greatly improved.
It is desirable that the slip band after repeated bending has a structure in which 50% or more is formed. Further, it is preferable to have a structure in which 80% or more, more preferably 90% or more is formed. And it is desirable that the slip band structure formed at the time of bending is uniformly distributed over the entire surface of the copper foil.

(Highly flexible mechanism of the rolled copper foil of the present invention (rolled foil of the present invention))
The reason why the rolled copper foil of the present invention (rolled foil of the present invention) has high flexibility is mainly considered to be the following three points.
(1) High orientation of crystal (200) plane The rolled copper foil of the present invention (rolled foil of the present invention) has a higher (200) plane orientation after recrystallization than the conventional rolled copper foil, almost 100%. The orientation is close to. I ₍₂₀₀₎ / _{Io (200)} > 40, preferably I ₍₂₀₀₎ / _{Io (200)} > 65. As a result, the orientation mismatch at the grain boundary becomes extremely small. For example, in an electrolytic copper foil in which crystals are randomly oriented, the crystal grain boundary orientation mismatch is large. This mismatch in crystal orientation affects the accumulation of fatigue (dislocations) at the grain boundaries. Therefore, it is considered that in the rolled foil of the present invention having a small mismatch, the accumulation of dislocations at the grain boundaries is also reduced, resulting in high flexibility. In the case of having such a structure, it is effective for the slip band after bending to form 50% or more on the surface of the rolled copper foil.

(2) Size of crystal grains Since the rolled copper foil of the present invention (rolled foil of the present invention) has a recrystallized crystal grain size that is significantly larger than that of a conventional rolled copper foil, the overall grain boundary is also reduced. . On the contrary, the electrolytic copper foil made of fine crystals has remarkably many crystal grain boundaries. In addition, when crack generation / progress in bending is along the crystal grain boundary, the rolled foil of the present invention having few crystal grain boundaries is less likely to generate cracks, and as a result, is considered to have high flexibility. This case is also effective for forming a slip band after bending.
(3) Ease of occurrence of slip band In the rolled foil of the present invention, slip band is easily generated by rolling, annealing, and crystal grain size. In repeated bending, the formation of this slip band is important. As described above, it is considered that the bending fatigue is relieved by the formation of the slip band, resulting in high flexibility.

For the production of the rolled copper foil, particularly if it is a condition that a uniform slip band is formed after repeated bending, that is, a condition that the slip band after bending the rolled copper foil is formed on the surface of the rolled copper foil by 50% or more. Although there is no limitation, for example, copper whose recrystallized aggregate structure of tough pitch copper and oxygen-free copper has a cubic orientation can be used. This copper ingot is melted, this ingot is hot-rolled from 900 ° C, then cold rolling and annealing are repeated, and finally a predetermined thickness (for example, 18 μm thickness, 12 μm thickness, 9 μm thickness) Roll to copper foil.
After the final cold rolling, the crystal grain size is adjusted to exceed 20 μm by annealing, and further adjusted to exceed 30 μm. The larger the crystal grain size is, the more preferable, and it is possible to make the crystal grain size exceeding 50 μm, further 100 μm and 200 μm.
In the final cold rolling, the degree of cube texture is adjusted by variously changing the rolling degree (R). For example, the adjustment is performed in the range of R = 90 to 100% (less than). Then, recrystallization annealing is performed at a temperature 50 ° C. higher than the semi-softening temperature to obtain I ₍₂₀₀₎ / I _{o (200)} > 40, preferably I ₍₂₀₀₎ / I _{o (200)} > 65. The I / Io value was measured by the X-ray diffraction (diffractometer) method (hereinafter the same).
R is defined by the following equation.
R = (t _o −t) / t _o (t _o : thickness before rolling, t: thickness after rolling)

 Hereinafter, the present invention will be described by way of examples. In addition, a present Example shows a suitable example, This invention is not limited to these Examples. Accordingly, all modifications and other examples or aspects included in the technical idea of the present invention are included in the present invention. For comparison with the present invention, comparative examples will be described as necessary.

A tough pitch copper ingot containing 200 ppm of Ag was melted, and the ingot was hot-rolled from 900 ° C. to obtain a 10 mm thick plate. Thereafter, cold rolling and annealing were repeated, and finally, cold rolling was performed to a copper foil having a thickness of 9 to 18 μm. The crystal grain size was adjusted to the range of 20-100 μm by annealing before the final cold rolling, and in the final cold rolling, the rolling degree (R) was variously changed and the strength of the cube texture was changed.
In the following examples, R = 98.2%, recrystallization annealing was performed at a temperature 50 ° C. higher than the semi-softening temperature, and I / Io = 40-80. The I / Io value was measured by the X-ray diffraction (diffractometer) method as described above.
Similar results were obtained when oxygen-free copper (HO material) was used as the rolled copper foil material. In an Example, it is not necessary to limit especially selection of the raw material for rolled copper foil, rolling, or heat processing conditions, and if it is the range described in this-application specification, it can select arbitrarily. Therefore, in the following description, details of the rolling process and the heat treatment process are omitted.
Hereinafter, the present invention will be described more specifically by various tests.

(Slip band evaluation method)
A slip band evaluation method will be described in advance.
[Preparation of test sample]
(1) Using copper foil (18μm thickness, 12μm thickness) and a polyimide sheet with adhesive, a copper clad laminate (CCL) with 3 layers is produced by thermocompression bonding
Thermocompression bonding conditions: 180 ° C, 60 minutes
(2) Forming a JIS C5016 folding test pattern on a 3-layer copper clad laminate by etching [Bend test]
Conducted IPC sliding bend test 30000 times with test sample Bending test condition: Bending radius: 2.0 mm, bending speed 1000 times / min, stroke 20 mm, copper foil side set inside [Slip band observation]
Check the area ratio of the slip band formation part on the surface of the test sample on the 60μm × 60μm screen of SEM (× 1500)

(Flexibility comparison test)
The copper foil used in the above test was used. For the examples of the present application, those having a slip band formation ratio of 64-98% were used, and for the comparative examples, those having a slip band formation ratio of 25-35% were used. Comparative evaluation of flexibility was performed between the rolled copper foil of the present invention (in FIG. 4 and FIG. 5, expressed as “rolled foil of the present invention”, the same applies hereinafter) and the conventional rolled foil (comparative example). FIG. 4 shows the IPC sliding bending test result at a bending radius of 1.5 mm.
As shown in FIG. 4, in the copper clad laminate of rolled foil having a thickness of 18 μm, the rolled foil of the present invention showed twice or more high flexibility than the conventional rolled copper foil. Furthermore, the rolled copper foil of the present invention having a thickness of 12 μm (rolled foil of the present invention) exhibited the highest flexibility, and had an excellent flexibility of about 3 times or more compared to the conventional rolled copper foil of 18 μm. . Further, FIG. 5 shows the results of the MIT folding resistance test at a bending radius of 0.8 mm. Similar to the IPC test results, the 12 μm invention invention rolled foil showed the highest flexibility.
As described above, the rolled copper foil of the present invention (rolled foil of the present invention) has a high bending property that is several times higher than that of the conventional rolled copper foil in the IPC sliding bending test and the MIT folding resistance test, which are general bending evaluation methods. Is shown. The latest model mobile phone hinge part is required to have a very high bendability, so this 12 μm invention invention rolled foil is optimal.

(Comparison test of flexibility with different circuit widths)
FIG. 6 shows the results of a sliding bending test in which the flexibility of the rolled copper foil of the present invention (rolled foil of the present invention) and the conventional rolled copper foil was changed by changing the copper foil circuit width. From FIG. 6, it can be seen that the flexibility decreases when the circuit width is reduced from 1 mm to 0.5 mm. This is because when the circuit width is narrowed, the life from crack to disconnection is shortened.
From FIG. 6, compared with the conventional copper clad laminate of rolled copper foil (circuit width 1 mm, right end), the rolled copper foil of the present invention (rolled foil of the present invention) copper clad laminate (circuit width 0.5 mm, left end) It can be seen that almost the same flexibility is obtained. That is, even if the circuit width is narrowed by making the circuit on the printed wiring board finer, the rolled foil of the present invention can maintain higher flexibility than the conventional rolled copper foil. In the above description, a 12 μm foil was used, but a 9 μm foil can similarly improve the bending resistance.

(About variation in flexibility)
FPC market demands require higher standards than ever for flex reliability as well as high flexibility. Therefore, the bending reliability of the rolled copper foil of the present invention (the present invention rolled foil), the conventional rolled copper foil, and the electrolytic copper foil (A, B) was evaluated. For evaluation, 100 pieces of copper foil single sample after heat treatment at 180 ° C. for 1 hour was subjected to a sliding bending test at a bending radius of 1.5 mm. FIG. 7 shows a frequency distribution of the number of bendings of 100 samples.
From FIG. 7, the conventional rolled copper foil shows the high flexibility stably. On the other hand, the special electrolytic copper foil has a variation in the number of bending until the copper foil breaks, and is inferior to the conventional rolled copper foil in stable bendability. From this, it can be seen that the conventional rolled copper foil is superior in severe bending conditions as compared with the conventional electrolytic copper foil.
However, in the case of the rolled copper foil of the present invention (the rolled foil of the present invention), it can be seen that a more excellent number of bendings can be obtained and the bending reliability is guaranteed as compared with the conventional rolled copper foil.

(Bend direction reliability)
Since the rolled copper foil is rolled in the MD (Machine Direction) direction in the manufacturing process, it is sometimes said that the flexibility of the copper foil differs between the MD direction and the TD (Traversal Direction) direction. Therefore, the MIT folding resistance test in the MD / TD direction was performed on the copper clad laminate using the rolled copper foil of the present invention. The result is shown in FIG.
From FIG. 8, there is no difference in flexibility between MD and TD in the conventional copper-clad laminate of rolled copper foil and the copper-clad laminate of the rolled copper foil of the present invention (rolled foil of the present invention). Indicated. This shows that the rolled copper foil of the present invention has high bending reliability not only in the MD direction but also in the TD direction.

(About high temperature flexibility)
The heat load on the FPC is also increasing due to the light, thin and small technology of electronic equipment. Therefore, bending evaluation in a high-temperature atmosphere was performed on copper foil, which is an FPC wiring material. The sliding bending test results at 25 ° C. and 80 ° C. are shown in FIG.
From FIG. 9, the conventional rolled copper foil is about 20,000 times at 80 ° C., and has a bendability that is twice or more compared to about 10,000 times of the electrolytic copper foil. However, the rolled foil of the present invention has dramatically improved bendability compared to the conventional rolled copper foil, and the number of bending exceeds 25,000 at 25 ° C and 80 ° C, with 80,000 bending. It is close to the number of times. This is about 4 times the conventional rolled copper foil. Thus, it can be seen that there is a marked improvement over the conventional rolled copper foil, and that high flexibility can be maintained not only at 25 ° C. (room temperature) but also at a high temperature of 80 ° C.

(About flexibility)
FPC manufacturers are developing polyimides and adhesives for softer FPC market requirements. Naturally, softness is also required for copper foil as a wiring material. Then, the result of having evaluated the softness of the rolled copper foil by the loop stiffness test is shown in FIG.
From FIG. 10, since the rolled copper foil of the present invention (the present invention rolled foil) has a loop stiffness of about 35% lower than that of the conventional rolled copper foil, the rolled copper foil of the present invention (the present invention rolled foil) is a conventional one. It can be said that it is softer than rolled copper foil. Therefore, if the rolled foil of the present invention of the present invention is used, it becomes possible to produce an FPC that is softer than the conventional rolled copper foil, so that it is possible to expect power saving due to the ease of folding and the reduction of the driving force of the FPC. Actually, there is a significant advantage in application to the rolled copper foil of the present invention (rolled foil of the present invention) in HDDs and optical pickups.

 According to the present invention, an excellent effect that a rolled copper foil having excellent bending resistance can be realized within the range of industrially acceptable production costs, particularly in the production of flexible printed wiring boards (FPC), industrially. Very useful.

Claims (6)

Integration of the (200) plane obtained by X-ray diffraction of the surface of the rolled copper foil after recrystallization annealing, which has a structure in which a slip band after bending the rolled copper foil is formed on the surface of the rolled copper foil by 50% or more. The intensity (I ₍₂₀₀₎ ) is I ₍₂₀₀₎ / I _{0 (200)} > 40 with respect to the integrated intensity (I _{0 (200)} ) of the (200) plane obtained by X-ray diffraction of fine powder copper. A rolled copper foil having excellent bending resistance, characterized in that it has a structure with an average crystal grain size exceeding 20 μm.   The rolled copper foil having excellent bending resistance according to claim 1, wherein the rolled band has a structure in which a slip band is formed on the surface of the rolled copper foil by 80% or more.   2. The rolled copper foil having excellent bending resistance according to claim 1, wherein a slip band has a structure in which 90% or more of the slip band is formed on the surface of the rolled copper foil. The rolled copper foil having excellent bending resistance according to any one of claims 1 to 3, wherein I ₍₂₀₀₎ / I _{0 (200)} > 65. The rolled copper foil having excellent bending resistance according to any one of claims 1 to 4 , which has a structure having an average crystal grain size of 30 µm or more. The bending resistance according to any one of claims 1 to 5 , further comprising a structure in which the number of bendings in an IPC sliding bending test (bending radius: 1.5 mm) in a rolled copper foil of 18 µm reaches 50,000 times or more. Rolled copper foil with excellent properties.

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