CN112064071B

CN112064071B - Bending-resistant copper foil, preparation method thereof and FPC (flexible printed circuit) flexible circuit board

Info

Publication number: CN112064071B
Application number: CN202010939817.0A
Authority: CN
Inventors: 刘科海; 张志强; 丁志强; 寇金宗; 何梦林; 王恩哥
Original assignee: Songshan Lake Materials Laboratory
Current assignee: Songshan Lake Materials Laboratory
Priority date: 2020-09-09
Filing date: 2020-09-09
Publication date: 2021-08-03
Anticipated expiration: 2040-09-09
Also published as: CN112064071A

Abstract

The application provides a bending-resistant copper foil, a preparation method thereof and an FPC flexible circuit board, and relates to the field of electronic circuits. The bending-resistant copper foil comprises: a single crystal bending-resistant copper foil or a large domain bending-resistant copper foil. The single crystal bending-resistant copper foil comprises: no grain boundary exists in the range of 200 × 200mm to 250 × 300mm, only a single crystal domain exists, and the size of the crystal domain is not less than 200 × 200 mm. The large-domain bending-resistant copper foil is obtained by carrying out electro-coppering and/or rolling treatment on a large-domain copper foil, wherein the large-domain copper foil is prepared by the following steps: more than one crystal domain or more than one crystal boundary exists in the range of 200-200 mm, and the number of the crystal domains in the range of 200-200 mm is less than 500. The large-domain copper foil and the single-crystal bending-resistant copper foil are obtained by reasonable optical instrument inspection, screening and classification, and meanwhile, the bending resistance of the large-domain copper foil is improved by post-treatment of the large-domain copper foil, so that the requirements of an FPC flexible circuit board are met.

Description

Bending-resistant copper foil, preparation method thereof and FPC (flexible printed circuit) flexible circuit board

Technical Field

The application relates to the field of electronic circuits, in particular to a bending-resistant copper foil, a preparation method thereof and an FPC flexible circuit board.

Background

FPC (Flexible Printed Circuit) flexible circuit board is made by copper-coating insulating films such as polyimide PI, liquid crystal polymer LCP and the like to form a flexible copper-clad plate FCCL, and then forming a circuit by copper etching and other steps to form a Printed circuit board with high reliability and excellent flexing or bending resistance.

The bending resistance refers to the ability of the FPC circuit board to maintain the circuit intact (without fracture or crack) and the resistance performance not to be improved under the environmental stress of winding, bending, folding or repeated movement, and the like, and is also considered to be the ability of the FPC circuit board to resist the mechanical stress and the bending reliability. Different electronic products have different requirements on the bending resistance of the FPC according to different purposes, the bending degree of the use environment and the like. With the development of terminal electronic devices such as smart phones, tablets, wearable devices, medical devices, and robots in recent years, FPC is required to be not only "small and thin" in a narrow space, but also to satisfy the high-strength bending reliability in a static state or a dynamic state in a narrow space (or in a smaller curvature radius).

The high bending resistance of the FPC board is mainly determined by the properties of the conductor material under specific conditions, and particularly under dynamic use conditions, the FPC board is constantly folded, bent, and stretched, which requires a conductor material resistant to bending fatigue with a long life. There are 2 kinds of copper foils, which are conductive materials currently used for FPC, namely electrolytic copper foil (ED copper) and rolled copper foil (RA copper).

The electrolytic copper foil is formed by adopting an electroplating mode, the copper crystal state of the cross section of the electrolytic copper foil is in a vertical column shape, and the fracture failure of the conductor is easily caused by the fact that the cross section grain boundary vertical direction is under the common influence of more grain boundaries existing in fine crystals in the bending stress direction and the crack is easily developed from the grain boundaries. In order to improve the bending resistance of the FPC, a rolled copper foil is generally used in the industry, the cross-section copper crystal of which is horizontal axis and is polycrystalline copper; in order to improve the folding resistance of the rolled copper foil, the prior art generally adopts hot rolling, cold rolling, recrystallization annealing process of the rolled copper foil, addition of trace elements, change of the proportion of a copper lattice structure and specific lattice orientation and other aspects for optimization and improvement, but with the development and application of terminal electronic equipment such as a 5G communication technology, a wearable device, a medical device, a robot, an automobile and the like, after the copper foil is applied to a terminal electronic FPC, macroscopic cracks are easily generated under bending stress after the copper foil is applied to the terminal electronic FPC, and the subsequent macroscopic cracks have higher expansion speed, so that an FPC circuit is broken in advance and the bending resistance requirement of the FPC is difficult to meet.

Disclosure of Invention

An object of the embodiments of the present application is to provide a bending-resistant copper foil, a method for manufacturing the same, and an FPC flexible circuit board, which can improve at least one of the above-mentioned technical problems.

In a first aspect, an embodiment of the present application provides a bending-resistant copper foil, which includes: a single crystal bending-resistant copper foil or a large domain bending-resistant copper foil.

Wherein, the single crystal bending-resistant copper foil is: no grain boundary exists in the range of 200 × 200mm to 250 × 300mm, only a single crystal domain exists, and the size of the crystal domain is not less than 200 × 200 mm.

The large-domain bending-resistant copper foil is obtained by carrying out electro-coppering and/or rolling treatment on the large-domain copper foil.

Wherein, the large-domain copper foil is as follows: more than one crystal domain or more than one crystal boundary exists in the range of 200-200 mm, and the number of the crystal domains in the range of 200-200 mm is less than 500.

In the implementation process, the single crystal bending-resistant copper foil and the large-domain copper foil obtained through reasonable screening have better bending resistance, the requirement of the FPC flexible circuit board is met, and the industrial size (200 x 200mm) of the copper foil of the FPC flexible circuit board is matched and prepared.

In a second aspect, an embodiment of the present application provides a method for preparing a bending-resistant copper foil, which includes:

and carrying out electro-coppering and/or rolling treatment on the large-domain copper foil to obtain the large-domain bending-resistant copper foil.

In the implementation process, the bending resistance of the large-domain bending-resistant copper foil is effectively improved through a reasonable treatment mode and reasonable selection of the large-domain copper foil, the operation is simple and controllable, the cost is low, and the industrial production is facilitated.

In a third aspect, an embodiment of the present application provides an FPC flexible circuit board, which includes the bending-resistant copper foil provided in the first aspect of the present application.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a schematic diagram of domain variation of a large-domain copper foil before and after rolling according to the present application;

FIG. 2 is a schematic view of the structure of a rolled copper foil (polycrystalline copper foil);

fig. 3 is a schematic structural view of a bending-resistant copper foil according to embodiment 2 of the present application;

FIG. 4 is a schematic structural view of a large domain copper foil according to example 3 of the present application;

FIG. 5 is a schematic comparison of a large domain copper foil of example 5 of the present application before and after rolling;

FIG. 6 shows a test example FPC trace setup;

FIG. 7 is a graph showing the statistics of the bending times of the test examples;

FIG. 8 is a comparison of a single crystal flex-resistant copper foil and a rolled copper foil after the same flex-resistant conditions.

Detailed Description

In order that the embodiments of the present application will be described in detail below with reference to examples, it will be understood by those skilled in the art that the following examples are only illustrative of the present application and should not be taken as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The applicant found that the domain of the conventional electrolytic copper foil and rolled copper foil is 100 × 100 μm or less, and the conventional FPC does not have the requirement of bending resistance.

In order to solve the problems, the applicant tries to apply a single crystal copper foil to the FPC instead of the existing rolled copper foil so as to hopefully improve the bending resistance of the FPC, but in the application process, the copper foil and the coil stock with the width of 250mm are found in the required 'makeup size' of the copper clad laminate FCCL for the industrialized large-scale production of the FPC; although related reports disclose a preparation process of a large-size single crystal copper foil at present, the mature, stable and large-scale preparation process of the large-size single crystal copper foil without crystal boundaries still faces a lot of difficulties, the manufacturing cost is high, the large-scale preparation of the single crystal copper foil is difficult to realize under the existing conditions, a small amount of crystal boundaries often occur locally, and the transmission to a certain circuit of an FPC causes the reduction of the bending resistance of the circuit.

Therefore, the method aims at the problems of the large-size single crystal copper foil prepared by the existing high-temperature annealing mode, and classifies and carries out related treatment on the high-temperature annealed copper foil through a specific classification mode, so that the problems are effectively avoided, the requirement of the high-temperature annealed copper foil can be met, and the use utilization rate of the high-temperature annealed copper foil is greatly improved.

Therefore, in the embodiment of the present application, the bending-resistant copper foil includes: a single crystal bending-resistant copper foil or a large domain bending-resistant copper foil.

The large-domain bending-resistant copper foil is obtained by carrying out electro-coppering and/or rolling treatment on the large-domain copper foil; wherein, the large-domain copper foil is as follows: more than one crystal domain or more than one crystal boundary exists in the range of 200-200 mm, and the number of the crystal domains in the range of 200-200 mm is less than 500. That is, the large domain copper foil is a copper foil in which a small number of grain boundaries or domains are present within a range of 200 × 200 mm.

It should be noted that the single crystal bending-resistant copper foil and the large domain copper foil can be prepared according to the relevant high temperature annealing technology, and can also be prepared by self, and the self-preparation method comprises the following steps:

placing rolled copper foil (polycrystalline copper with purity of more than 99.96%) on high temperature resistant substrate, placing into chemical vapor deposition equipment, and introducing inert gas (N)₂Or Ar) and H₂Heating, wherein the inert gas flow rate is 300-₂The flow rate is 20-50 sccm; when the temperature rises to 800-²Gas annealing, at which time H₂The flow rate was 2 to 500sccm, and a "high-temperature annealed" copper foil was obtained as a sample.

According to the prepared copper foil subjected to high-temperature annealing, an optical instrument is utilized to carry out screening classification, screening classification and post-treatment are carried out according to the maximum single crystal domain size and different crystal boundary definitions, so that the single crystal bending-resistant copper foil or the large crystal domain bending-resistant copper foil is obtained, the bending resistance of a circuit is improved as much as possible, the problem that the bending resistance of the circuit is reduced due to a small amount of crystal boundaries existing in the large-size single crystal copper foil prepared by the conventional high-temperature annealing is avoided, and meanwhile, compared with the conventional rolled copper foil, the bending resistance is effectively improved.

Specifically, in one example of the present application, the single-crystal flex-resistant copper foil has no grain boundary in the range of 200 × 200mm to 250 × 300mm, only has a single crystal domain, and the size of the crystal domain is not less than 200 × 200 mm.

The single-crystal bending-resistant copper foil does not need extra treatment and can be directly used for replacing rolled copper foil to be applied to an FPC flexible circuit board.

When the bending-resistant copper foil is applied to the FPC flexible circuit board, the bending resistance of the circuit of the FPC flexible circuit board can be effectively improved, and the service life of the FPC flexible circuit board is prolonged. The FPC flexible circuit board can be applied to narrow spaces of terminal electronic equipment such as smart phones, flat plates, wearable devices, medical devices and robots and is under environmental stress such as winding, bending, folding or repeated movement; for example, a bending-resistant FPC circuit board is required in a panel module, a camera module and an antenna module in the field of smart phones; the COF substrate comprises a COF substrate of a face screen module, an FPC circuit board made of LCP materials of an antenna module and the like.

That is, the bending-resistant FPC board includes a bending-resistant copper foil instead of the rolled copper foil, and the bending-resistant FPC board is mainly applied to COF and used as an antenna conductor of LCP.

The preparation method of the high-bending-resistance FPC circuit board can refer to the related technology and specifically comprises the following steps:

the surface of the bending-resistant copper foil is subjected to roughening and anti-oxidation treatment, and then the insulating film is coated or pressed to prepare the flexible copper clad laminate FCCL. And drilling the FCCL, and sequentially performing hole metallization, pattern transfer and circuit etching to obtain the FCCL.

Wherein the insulating film is PI, PTFE, PPE, LCP or PEEK.

The bending-resistant copper foil may be disposed on a single side or two opposite sides of the insulating film, and the specific number of layers of the bending-resistant copper foil is not limited herein.

In one example of the present application, there is provided a method for preparing a bending-resistant copper foil, including:

and carrying out post-treatment on the large-domain copper foil to obtain the large-domain bending-resistant copper foil. That is, the bending-resistant copper foil is actually a large-domain bending-resistant copper foil, and the bending resistance of the large-domain copper foil is effectively improved through a post-treatment mode.

Wherein the large-domain copper foil has more than one crystal domain or more than one crystal boundary within the range of 200 × 200mm, and the number of the crystal domains within the range of 200 × 200mm is less than 500. In this case, since the size of each domain of the large domain copper foil is much larger than that of the conventional rolled copper foil, the number of grain boundaries per unit area is small, so that the macrocracks and the propagation rate are reduced under bending stress. That is, a large domain copper foil is a copper foil having "a small number of grain boundaries or domains exist within a range of 200 × 200 mm", but is much smaller than a rolled copper foil of polycrystals. The thickness of the large-domain copper foil is 15 to 75 μm.

The post-treatment mode comprises electro-coppering treatment and/or rolling treatment, namely the large-domain bending-resistant copper foil is obtained by carrying out electro-coppering and/or rolling treatment on the large-domain copper foil. The electrolytic copper plating process and the rolling process may be performed independently or together.

In one example of the present application, when the step of performing the electro-coppering and rolling process on the large domain copper foil includes: the large-domain copper foil is firstly rolled, and then the surface of the product obtained after rolling is electroplated with copper.

In one example of the present application, as shown in fig. 1, the step of calendering process comprises: rolling the large-domain copper foil until the thickness of the large-domain copper foil is reduced by 20-50%.

Wherein the roller is pressed at 400-2000Kg/cm²Under the conditions of (1).

The rolling can be independently carried out, the independent implementation is carried out under the condition of room temperature, the rolling is used for flattening the grain boundary on the surface of the copper foil with large crystal domains after being pressed, each crystal domain is lengthened and enlarged, and the bending resistance of the copper foil is improved.

When the rolling is performed independently, the number of the large domain copper foil may be one layer, and when the number of the large domain copper foil is at least two layers, in order to ensure that the at least two layers of the large domain copper foil after the final rolling treatment can become one layer and have better bending resistance, optionally, in one example of the present application, the rolling treatment further comprises: annealing the large-domain copper foil at the temperature of 300-1000 ℃ before rolling; the method is characterized in that at least two layers of large-domain copper foils can be laminated into one layer of large-domain copper foil by utilizing the operations of annealing and rolling, the problem of layering between the copper foils is avoided, the bending resistance of the copper foils is improved, and the rolling frequency is at least one time and at least one time of rolling is carried out at the annealing temperature in the process of laminating at least two layers of large-domain copper foils into one layer of large-domain copper foil by utilizing the operations of annealing and rolling.

Optionally, the number of the large-domain copper foils is 1-5, when the number of the large-domain copper foil layers is at least two, the at least two large-domain copper foil layers are arranged in an overlapping manner and are annealed and rolled, and when the number of the large-domain copper foil layers is one, the rolling can be directly performed, so that the annealing process is saved.

In one example of the present application, the step of electroplating copper comprises: and forming an electroplated copper layer on the surface of the large-domain copper foil in an electroplating mode, wherein the thickness of the electroplated copper layer is 0.1-1 mu m.

The electroplated copper layer can be formed on the single-side surface or the double-side surface of the large-domain copper foil and can be selected according to actual requirements.

The thickness of the bending-resistant copper foil is 6-200 μm.

The large-domain copper foil and the single-crystal bend-resistant copper foil have any one of crystal orientations of Cu (111), Cu (110), Cu (211), Cu (100), Cu (346), Cu (235), Cu (236), Cu (134), Cu (543), Cu (123), and Cu (252).

The bending-resistant copper foil, the preparation method thereof and the FPC flexible circuit board of the present application are further described in detail with reference to the examples below.

In the following examples and test examples, rolled copper foils (polycrystalline copper foils having a purity of > 99.96%) were used2, the crystal domains with the size of 20-100um and the number of the crystal domains within the range of 200 x 200mm is more than 50000, the crystal domains are horizontally arranged on a high-temperature resistant substrate, the substrate is placed into chemical vapor deposition equipment, and inert gas (N) is introduced₂) And H₂Heating with inert gas flow rate of 300-₂The flow rate is 20-50 sccm; temperature rise is controlled by a program, when the temperature rises to 800 ℃, H is introduced₂Gas and H₂The flow is 2-500sccm, annealing is carried out at 1100 ℃, and a large-size single crystal copper foil prepared in a high-temperature annealing mode is obtained as a sample.

According to an optical detection device, a sample is used as a single-crystal bending-resistant copper foil, wherein no crystal boundary exists in the range of 200-200 mm to 250-300 mm, only a single crystal domain exists, and the size of the crystal domain is not less than 200-200 mm; the large domain copper foil was prepared by using a copper foil having one or more crystal domains or one or more grain boundaries within 200 × 200mm and having a number of crystal domains < 500 within 200 × 200mm, wherein the rolled copper foils used in the "high temperature annealing" methods of examples 1 to 4 and comparative example 1 had the same thickness, and the rolled copper foil used in the "high temperature annealing" method of example 5 had a thickness greater than that of examples 1 to 4.

Example 1

A FPC circuit board is obtained by roughening and anti-oxidizing the surface of a bending-resistant copper foil according to related technologies, then pressing the surface to PI to prepare a flexible copper clad laminate FCCL, drilling the FCCL, and then sequentially performing hole metallization, pattern transfer and circuit etching.

The bending-resistant copper foil is a single-crystal bending-resistant copper foil which has no crystal boundary (except for a thermal etching groove) within the range of 200 x 200mm and only has a single crystal domain, and the thickness of the bending-resistant copper foil is 25 mu m.

Example 2

An FPC board which differs from embodiment 1 only in that:

as shown in fig. 3, the bending-resistant copper foil is a single-crystal bending-resistant copper foil having no grain boundary (except for thermal etching grooves) within a range of 200 × 300mm and having only one crystal domain, and the thickness of the bending-resistant copper foil is 25 μm.

Example 3

An FPC board which differs from embodiment 1 only in that:

the bending-resistant copper foil comprises: in the large domain copper foil shown in fig. 4, one or more domains or one or more grain boundaries exist within 200 × 200mm, and the number of domains within 200 × 200mm is less than 500, and after one surface of the large domain copper foil is subjected to copper electroplating treatment, a copper electroplating layer is formed.

Wherein the thickness of the formed electroplated copper layer is 1 μm.

Example 4

An FPC board which differs from embodiment 3 only in that:

the bending-resistant copper foil comprises: overlapping three layers of large-domain copper foils, annealing at 600 ℃, and then performing 1000Kg/cm at the temperature²The copper foil is rolled to form a layer of thick copper foil with the thickness of 50um, and then the thick copper foil is cooled and then is rolled and thinned at room temperature, the thickness is reduced by 50 percent, and the thickness of the obtained bending-resistant copper foil is 25 mu m.

Example 5

The bending-resistant copper foil comprises: a layer of large-domain copper foil is coated at room temperature according to 1000Kg/cm²And (5) rolling and thinning, wherein the thickness is thinned by 30%, and the thickness of the obtained bending-resistant copper foil is 25 μm.

The ratio of the large-domain copper foil before and after rolling is shown in fig. 5, wherein the grain boundary on the surface of the large-domain copper foil after thinning is filled, and each domain is lengthened and enlarged.

Example 6

An FPC board which differs from embodiment 5 only in that:

both surfaces of the bending-resistant copper foil obtained in example 5 were subjected to an electrolytic copper plating treatment to form an electrolytic copper plated layer having a thickness of 0.9 μm.

Test example 1

The control group 1 was set, and the thickness of the sample (sample before classification) prepared by the "high temperature annealing" method in the control group 1 was 25 μm.

In the same manner as the above, the FPC obtained in examples 1 to 6 and control 1 was subjected to the bending resistance test and the test was repeated 6 times, and the results of the average number of bending times obtained are shown in table 1 below, in which the circuit arrangement and specification of the FPC are uniform and the circuit arrangement is shown in fig. 6.

TABLE 1

Class of copper foil	Average number of bends
		Example 1	253
Example 2	254
		Example 3	172
Example 4	194
		Example 5	188
Example 6	190
		Control group 1	152

MIT bending resistance test conditions (refer to industry association standard CPCA/JPCA-BM 03-2005): line width spacing 1/1 mm; bending speed 175rpm, angle 135+/-5 degrees, load 4.9N, chuck curvature radius R0.38 mm, and clamping thickness 0.5 mm; the test results are shown in fig. 7.

According to fig. 7, the MIT bending resistance test is performed on a common polycrystalline rolled copper foil (i.e., rolled copper), a large domain cylinder wall obtained by classification according to the present application, and a single crystal bending resistance copper foil, and it can be seen that 3 types of copper foils with the same other conditions are compared, the smaller the number of grain boundaries is, the higher the bending resistance of the FPC is; compared with the polycrystalline rolled copper foil, the bending resistant times of the large-domain copper foil FPC without post-treatment are increased by more than 30%, and the bending resistant times of the single-crystal bending resistant copper foil FPC are increased by 50% or even more than 100%.

FIG. 8 is a comparison graph of the appearance and the appearance of a single-crystal bending-resistant copper foil and a rolled copper foil after the same bending resistance, wherein according to FIG. 8, it can be seen that the single-crystal bending-resistant copper foil has few grain boundaries, and few surface cracks are caused under the bending condition, and only one of the surface cracks is shown by an arrow; rolled copper foil has many grain boundaries, and many surface cracks are caused.

Meanwhile, as can be seen from the comparison between table 1 and fig. 8, the preparation method provided by the present application can effectively improve the bending resistance of the large domain copper foil.

In summary, the single crystal bending-resistant copper foil and the large-domain copper foil obtained by reasonably screening and classifying the single crystal bending-resistant copper foil and the large-domain copper foil through post-treatment have better bending resistance, meet the requirements of the FPC flexible circuit board, and simultaneously avoid the problem of reduced bending resistance of an FPC circuit caused by a small amount of crystal boundaries in a partial region of the large-size single crystal copper foil prepared by the conventional high-temperature annealing preparation method.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A bending-resistant copper foil is characterized by comprising: a single crystal bending-resistant copper foil or a large crystal domain bending-resistant copper foil;

wherein the single crystal bending-resistant copper foil is: no grain boundary exists in the range of 200 × 200mm or 250 × 300mm, only a single crystal domain exists, and the size of the crystal domain is not less than 200 × 200 mm;

the large-domain bending-resistant copper foil is obtained by carrying out electro-coppering and/or rolling treatment on a large-domain copper foil;

wherein the large-domain copper foil is: more than one crystal domain exists or more than one crystal boundary exists in the range of 200 × 200mm, and the number of the crystal domains in the range of 200 × 200mm is less than 500;

the large-domain copper foil and the single-crystal bending-resistant copper foil are obtained by screening after being prepared by a high-temperature annealing method, wherein the high-temperature annealing method comprises the following steps: placing the rolled copper foil on a high temperature resistant substrate, placing the substrate in a chemical vapor deposition device, and introducing inert gas and H₂Heating, wherein the inert gas flow rate is 300-₂The flow rate is 20-50 sccm; when the temperature rises to 800-²Annealing is carried out, at this time H₂The flow rate is 2-500 sccm.

2. The flex-resistant copper foil according to claim 1, wherein the thickness of the flex-resistant copper foil is 6-200 μm.

3. A method of making a flex-resistant copper foil according to any of claims 1-2 comprising:

and carrying out electro-coppering and/or calendaring treatment on the large-domain copper foil to obtain the large-domain bending-resistant copper foil.

4. The production method according to claim 3, wherein the step of subjecting the large domain copper foil to electrolytic copper plating and rolling treatment comprises:

and firstly carrying out rolling treatment on the large-crystal-domain copper foil, and then carrying out electrolytic copper treatment.

5. The production method according to claim 3 or 4, wherein the thickness of the large domain copper foil is 15 to 75 μm.

6. The production method according to claim 3 or 4, wherein the step of electroplating copper comprises: and forming an electroplated copper layer on the surface of the large-domain copper foil in an electroplating mode, wherein the thickness of the electroplated copper layer is 0.1-1 mu m.

7. The production method according to claim 3 or 4, wherein the step of the calendering process includes: and rolling the large-domain copper foil until the thickness of the large-domain copper foil is reduced by 20-50%.

8. The production method according to claim 7, wherein the step of the calendering process includes: and annealing the large-domain copper foil at the temperature of 300-1000 ℃ before rolling.

9. The method according to claim 8, wherein the number of the large domain copper foils is at least two, and the at least two large domain copper foils are arranged in a stacked manner and annealed and rolled.

10. An FPC flexible circuit board comprising the bending-resistant copper foil according to any one of claims 1 to 2.