Stretched copper foil, method for producing the same, and use thereof

Abstract

This invention provides a rolled copper foil, its preparation method, and its application. The rolled copper foil comprises the following elements: 50-400 ppm Ag; 20-100 ppm P; 20-100 ppm La; 3-10 ppm O; unavoidable impurities totaling ≤100 ppm; and the remainder being Cu; the total mass content of P and La is <100 ppm; the heat resistance temperature of the rolled copper foil is 180-200℃; and the Cube{001} in the rolled copper foil... <100> The texture accounts for >80% of the volume, and the average grain size of the rolled copper foil is >200μm. The rolled copper foil of this invention has both good heat resistance and excellent flexibility, making it suitable for applications with stringent requirements for thermal stability and dynamic bending performance.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing technology, and more specifically, to a rolled copper foil, its preparation method, and its application. Background Technology

[0002] Rolled copper foil possesses advantages such as excellent tensile strength and elongation, low surface roughness, and stable thermal and electrical conductivity. It also exhibits excellent flexibility, making it widely used in flexible electronics and communications. Specific products include foldable phones, wearable FPCs, 5G base station RF components, and signal receivers. With the development of communication technology and the increasing thinness and performance of electronic devices, copper foil is required to withstand flexural cycles of over 100,000 times. New flexible circuit board manufacturing processes demand that copper foil possess both moderate heat resistance and excellent flexibility.

[0003] Currently, it is difficult to simultaneously improve the flexibility and heat resistance of copper foil. Therefore, in order to meet the ever-growing higher requirements of the electronic information field, it is urgent to prepare rolled copper foil with moderate heat resistance and excellent flexibility. Summary of the Invention

[0004] The main objective of this invention is to provide a rolled copper foil, its preparation method, and its application, so as to solve the problem that it is difficult to simultaneously improve the flexural performance and heat resistance of rolled copper foil in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a rolled copper foil is provided, comprising the following elements: 50-400 ppm Ag; 20-100 ppm P; 20-100 ppm La; 3-10 ppm O; the total content of unavoidable impurities ≤100 ppm; and the remainder being Cu; the total mass content of P and La is <100 ppm; the heat resistance temperature of the rolled copper foil is 180-200°C; and the Cube{001} in the rolled copper foil... <100> The volume fraction of the texture is >80%, and the average grain size of the rolled copper foil is >200μm.

[0006] Furthermore, the rolled copper foil includes the following elements: 100~350ppm Ag; 22~80ppm P; 30~90ppm La; 4~10ppm O; the total content of unavoidable impurities is ≤100ppm, and the remainder is Cu; the total mass content of P and La is <100ppm; the heat resistance temperature of the rolled copper foil is 185~200℃, and the Cube{001} in the rolled copper foil... <100> The volume fraction of the texture is 81-95%, and the average grain size of the rolled copper foil is 210-480 μm.

[0007] Furthermore, the mass ratio of La to P is (1~3):1; and / or, the surface roughness Rz of the rolled copper foil is <1.5μm; and / or, the thickness of the rolled copper foil is 9~50μm.

[0008] According to another aspect of the present invention, a method for preparing the above-mentioned rolled copper foil is provided, the method comprising: step S1, melting and casting the raw material corresponding to the rolled copper foil to obtain an ingot; the average grain size of the ingot is ≤800μm; step S2, sequentially subjecting the ingot to gradient hot rolling, rough rolling, gradient annealing, finish rolling, foil rolling, surface treatment and softening annealing to obtain rolled copper foil; wherein, the gradient hot rolling process includes performing a first hot rolling at 800~850℃ and a second hot rolling at 500~550℃; the gradient annealing process includes: holding at 180~220℃, raising the temperature to 280~320℃ for a first annealing, and continuing to raise the temperature to 360~400℃ for a second annealing.

[0009] Furthermore, in step S1 above, the oxygen content of the copper melt in the casting is 3~10ppm; and / or, the casting method is electromagnetic assisted continuous casting; and / or, the average grain size of the ingot is 500~800μm.

[0010] Furthermore, in step S2 above, the first hot rolling has 5 to 7 passes, the total deformation of the first hot rolling is 75 to 85%, and the deformation per pass of the first hot rolling is 30 to 40%; the second hot rolling has 2 to 4 passes, the total deformation of the second hot rolling is 40 to 60%, and the deformation per pass of the second hot rolling is 10 to 20%; the average grain size of the strip after gradient hot rolling is <40μm.

[0011] Furthermore, in step S2 above, the gradient annealing process includes: holding at 180~220℃ for 1~3h, raising the temperature to 280~320℃ for a first annealing for 1~3h, and continuing to raise the temperature to 360~400℃ for a second annealing for 1~3h; the average grain size of the strip blank after gradient annealing is <20μm.

[0012] Further, in step S2 above, the deformation amount of rough rolling is 60~90%; and / or, the deformation amount of finish rolling is 85~95%; and / or, the foil rolling method is multi-pass cold rolling, the total reduction rate of foil rolling is ≥92%, and the single-pass reduction rate of foil rolling is 5~15%; the surface roughness Ra of the work rolls in foil rolling is <0.05μm; the surface roughness Ra of the foil material after foil rolling is <0.1μm; the average grain size of the foil material after foil rolling is <15μm; and / or, the S{123} of the foil material after foil rolling... <634> Texture, R{124} <211> Texture and Copper{112} <111> The total volume percentage of the texture is >50%, preferably 60-80%; S{123} in the foil material after foil rolling <634> The volume percentage of the texture is >30%, preferably 35~45%.

[0013] Furthermore, in step S2 above, the surface treatment process includes sequentially performing degreasing and cleaning, reddening treatment or blackening treatment; and / or, the softening annealing temperature is 180~200℃, and the softening annealing time is 0.5~2h.

[0014] According to another aspect of the present invention, an application of rolled copper foil in flexible circuit boards is provided, wherein the rolled copper foil is the rolled copper foil described above.

[0015] By applying the technical solution of this invention, this application can improve the heat resistance of rolled copper foil by controlling the elemental composition and content within the above-mentioned range, while simultaneously reducing the Cube{001} content in the rolled copper foil (after softening annealing). <100> The texture (cube texture) and average grain size reach the above-mentioned range, thus preventing wrinkles caused by rapid softening in subsequent applications of rolled copper foil, and giving the copper foil good flexibility and bending properties. Specifically, the addition of Ag element enables it to form a solid solution with Cu, thereby significantly improving the conductivity and ductility of rolled copper foil, while increasing the deformation texture retention rate, which is beneficial to S{123} <634> The formation of S-texture improves the heat resistance of rolled copper foil. If the Ag element content is below 50 ppm, the improvement is not significant; if the Ag element content is above 400 ppm, it leads to a significant increase in the cost of the copper foil and excessively high heat resistance temperature. Therefore, this application controls the Ag element content within the above range to balance cost, conductivity, and heat resistance. Phosphorus (P) is a good deoxidizer and can synergistically work with La to achieve joint deoxidation while also promoting the transformation of S-texture during deformation and cubic texture during recrystallization annealing. Trace amounts of P can improve the heat resistance of rolled copper foil and purify grain boundaries, thereby improving deformation uniformity and enhancing S-texture. If the P element content is below 10 ppm, the deoxidation effect is insufficient, and the improvement in heat resistance is limited; if the P element content is above 100 ppm, it inhibits recrystallization and reduces the average grain size of the rolled copper foil. Therefore, controlling the phosphorus (P) content within the aforementioned range can improve the heat resistance of rolled copper foil and ensure its average grain size reaches the above range. La (La) can synergistically deoxidize with P, simultaneously refining grains, purifying grain boundaries, and reducing impurity segregation, thereby improving the oxidation resistance and corrosion resistance of rolled copper foil, as well as enhancing the sulfur texture. If the La addition is below 20 ppm, the effect of refining ingot grains and purifying grain boundaries is insufficient; if the La addition is above 100 ppm, rare earth compound inclusions will form, thus inhibiting recrystallization. Therefore, controlling the La addition within the aforementioned range can improve the oxidation performance and corrosion resistance of rolled copper foil. Further controlling the total mass content of P and La, as well as the total content of other impurity elements, within the aforementioned range can avoid the risk of excessive alloying elements hindering grain growth during recrystallization. Adding the aforementioned amount of oxygen (O) can form trace oxides with P and La, playing a role in refining grains and improving deformation uniformity. In summary, the rolled copper foil of this application has both good heat resistance and excellent flexibility, making it suitable for applications with stringent requirements for thermal stability and dynamic bending performance, such as high-reliability flexible circuits, automotive electronics, and 5G communications. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0017] As analyzed in the background section of this application, existing rolled copper foils have the problem of difficulty in simultaneously improving both flexural performance and heat resistance. In order to solve the above problems, this application provides a rolled copper foil, its preparation method, and its application.

[0018] In a typical embodiment of this application, a rolled copper foil is provided, comprising the following elements: 50-400 ppm Ag, 20-100 ppm P, 20-100 ppm La, 3-10 ppm O, with the total content of unavoidable impurities ≤100 ppm, and the remainder being Cu; the total mass content of P and La is <100 ppm; the heat resistance temperature of the rolled copper foil is 180-200℃, and the Cube{001} in the rolled copper foil... <100> The volume fraction of the texture is >80%, and the average grain size of the rolled copper foil is >200μm.

[0019] This application, by controlling the elemental composition and content of rolled copper foil within the aforementioned range, can improve its heat resistance while simultaneously reducing the Cube{001} content in the rolled copper foil (after softening and annealing). <100> The texture (cube texture) and average grain size reach the above-mentioned range, thus preventing wrinkles caused by rapid softening in subsequent applications of rolled copper foil, and giving the copper foil good flexibility and bending properties. Specifically, the addition of Ag element enables it to form a solid solution with Cu, thereby significantly improving the conductivity and ductility of rolled copper foil, while increasing the deformation texture retention rate, which is beneficial to S{123} <634> The formation of S-texture improves the heat resistance of rolled copper foil. If the Ag element content is below 50 ppm, the improvement is not significant; if the Ag element content is above 400 ppm, it leads to a significant increase in the cost of the copper foil and excessively high heat resistance temperature. Therefore, this application controls the Ag element content within the above range to balance cost, conductivity, and heat resistance. Phosphorus (P) is a good deoxidizer and can synergistically work with La to achieve joint deoxidation while also promoting the transformation of S-texture during deformation and cubic texture during recrystallization annealing. Trace amounts of P can improve the heat resistance of rolled copper foil and purify grain boundaries, thereby improving deformation uniformity and enhancing S-texture. If the P element content is below 10 ppm, the deoxidation effect is insufficient, and the improvement in heat resistance is limited; if the P element content is above 100 ppm, it inhibits recrystallization and reduces the average grain size of the rolled copper foil. Therefore, controlling the phosphorus (P) content within the aforementioned range can improve the heat resistance of rolled copper foil and ensure its average grain size reaches the above range. La (La) can synergistically deoxidize with P, simultaneously refining grains, purifying grain boundaries, and reducing impurity segregation, thereby improving the oxidation resistance and corrosion resistance of rolled copper foil, as well as enhancing the sulfur texture. If the La addition is below 20 ppm, the effect of refining ingot grains and purifying grain boundaries is insufficient; if the La addition is above 100 ppm, rare earth compound inclusions will form, thus inhibiting recrystallization. Therefore, controlling the La addition within the aforementioned range can improve the oxidation performance and corrosion resistance of rolled copper foil. Further controlling the total mass content of P and La, as well as the total content of other impurity elements, within the aforementioned range can avoid the risk of excessive alloying elements hindering grain growth during recrystallization. Adding the aforementioned amount of oxygen (O) can form trace oxides with P and La, playing a role in refining grains and improving deformation uniformity. In summary, the rolled copper foil of this application has both good heat resistance and excellent flexibility, making it suitable for applications with stringent requirements for thermal stability and dynamic bending performance, such as high-reliability flexible circuits, automotive electronics, and 5G communications.

[0020] To further improve the flexibility and heat resistance of rolled copper foil, in one embodiment of this application, the rolled copper foil comprises the following elements: 100~350ppm Ag, 22~80ppm P, 30~90ppm La, 4~10ppm O, with the total content of unavoidable impurities ≤100ppm, and the remainder being Cu; the total mass content of P and La is <100ppm; the heat resistance temperature of the rolled copper foil is 185~200℃, and the Cube{001} in the rolled copper foil... <100> The volume fraction of the texture is 81-95%, and the average grain size of the rolled copper foil is 210-480 μm.

[0021] In one embodiment of this application, the mass ratio of La to P is (1~3):1; and / or, the surface roughness Rz of the rolled copper foil is <1.5μm; and / or, the thickness of the rolled copper foil is 9~50μm.

[0022] Preferring a mass ratio of La to P within the aforementioned range helps to enhance their synergistic effect. This not only improves the plasticity uniformity and strain coordination of rolled copper foil during bending deformation, thereby further enhancing its flexural properties, but also helps to strengthen the S-texture, thus simultaneously improving the heat resistance of rolled copper foil.

[0023] Preferably, the surface roughness Rz of the rolled copper foil is within the above-mentioned range, which helps to reduce the stress concentration effect at the interface between the copper foil and the copper-clad substrate, thereby improving the reliability and durability of the interface bonding. Preferably, the thickness of the rolled copper foil is within the above-mentioned range, which helps it maintain excellent mechanical support while meeting the requirements for thinness and lightness.

[0024] In another typical embodiment of this application, a method for preparing the above-mentioned rolled copper foil is provided. The method includes: step S1, melting and casting the raw material corresponding to the rolled copper foil to obtain an ingot; the average grain size of the ingot is ≤800μm; step S2, sequentially subjecting the ingot to gradient hot rolling, rough rolling, gradient annealing, fine rolling, foil rolling, surface treatment, and softening annealing to obtain rolled copper foil; wherein, the gradient hot rolling process includes performing a first hot rolling at 800~850℃ and a second hot rolling at 500~550℃; the gradient annealing process includes: holding at 180~220℃, raising the temperature to 280~320℃ for a first annealing, and continuing to raise the temperature to 360~400℃ for a second annealing.

[0025] The preparation method of this application employs gradient hot rolling and gradient annealing processes, which enables the copper foil strip to obtain a fine-grained recrystallized structure during the preparation process, promoting S{123} <634> Texture (S texture), R{124} <211> Texture (R texture) and Copper{112} <111> The formation of texture (Copper texture) simultaneously promotes the formation of Cube{001} during the copper foil softening annealing process. <100> The formation of texture results in rolled copper foil with moderate heat resistance and excellent flexibility. Specifically, in step S1, the casting process combined with deoxidation by P and La elements, along with the synergistic effect of microalloying by Ag, P, and La elements, purifies grain boundaries and reduces oxide inclusions, thereby refining the original ingot grain size to the aforementioned range. This ensures uniform grain deformation during subsequent cold rolling, providing favorable conditions for the formation of the S-texture. Step S2 involves gradient hot rolling, first at 800-850℃ with large deformation to fully break down the original microstructure and promote uniform solid solution, followed by small deformation hot rolling within the aforementioned temperature range to prevent overheating and grain growth, ultimately obtaining a homogeneous hot-rolled billet with refined grain size. The rough rolling introduces high-density dislocations and strong deformation texture, providing sufficient energy for recrystallization. Gradient annealing eliminates internal stress by holding at a low temperature of 200-250℃, followed by medium-temperature annealing at 300-350℃ to initiate recrystallization nuclei. Finally, grain refinement and stabilization of the S-texture, R-texture, and Copper texture are achieved at 380-400℃, ensuring the microstructure is in optimal orientation before cold rolling. Finish rolling enhances the preferential growth of the texture, thereby improving deformation uniformity. Foil rolling employs a high total reduction rate and multiple passes with low reduction rates in cold rolling, promoting the synergistic growth of the S-texture, R-texture, and Copper texture during deformation, providing an efficient nucleation template for subsequent low-temperature recrystallization. Surface treatment creates a controllable rough interface, improving adhesion to the substrate without damaging the internal structure. Finally, softening annealing promotes efficient nucleation and growth of the Cube texture to an average grain size within the aforementioned range, achieving grain coarsening independent of high temperatures, thus simultaneously improving thermal stability and high flexural performance.

[0026] In one embodiment of this application, in step S1 above, the oxygen content of the copper melt in the casting is 3~10ppm; and / or, the casting method is electromagnetic assisted continuous casting; and / or, the average grain size of the ingot is 500~800μm.

[0027] By controlling the oxygen content of the molten copper within the above-mentioned range during the casting process, and by using electromagnetically assisted continuous casting, it is helpful to purify the grain boundaries and reduce oxide inclusions. At the same time, the stirring effect of the electromagnetic field helps to refine and homogenize the internal grain structure of the ingot, so that the average grain size of the ingot is maintained within the above-mentioned range. This is conducive to uniform grain deformation during subsequent cold rolling, providing favorable conditions for the formation of S-texture.

[0028] In one embodiment of this application, in step S2 above, the first hot rolling has 5 to 7 passes, the total deformation of the first hot rolling is 75 to 85%, and the deformation per pass of the first hot rolling is 30 to 40%; the second hot rolling has 2 to 4 passes, the total deformation of the second hot rolling is 40 to 60%, and the deformation per pass of the second hot rolling is 10 to 20%; the average grain size of the strip after gradient hot rolling is <40 μm, preferably 20 to 30 μm.

[0029] Preferably controlling the number of passes, single-pass deformation, and total deformation in the first and second hot rolling processes within the aforementioned ranges helps the ingot achieve sufficient grain fragmentation and recrystallization suppression during the first hot rolling process, and complete uniform refinement and texture directional evolution during the second hot rolling process. This controls the average grain size of the strip after gradient hot rolling within the aforementioned range, which in turn improves the deformation uniformity and texture consistency during subsequent cold rolling, reduces local stress concentration and foil thickness fluctuations caused by coarse or uneven grain distribution, and ultimately achieves excellent flexural fatigue life for rolled copper foil while maintaining moderate heat resistance. Preferably, maintaining the single-pass deformation within the aforementioned range for 5 and 6 passes helps improve the grain refinement effect.

[0030] The preferred temperature of the first hot rolling is 250-300°C higher than that of the second hot rolling, which helps to improve the synergistic effect of the two, thereby achieving the dual goals of "high-temperature coarsening and crushing" and "low-temperature fine grain stabilization", and further improving the heat resistance and flexural properties of the rolled copper foil.

[0031] In one embodiment of this application, the gradient annealing process in step S2 includes: holding at 180~220℃ for 1~3h, raising the temperature to 280~320℃ for a first annealing for 1~3h, and continuing to raise the temperature to 360~400℃ for a second annealing for 1~3h; the average grain size of the strip after gradient annealing is <20μm, preferably 10~15μm.

[0032] The above-mentioned three-stage gradient annealing process helps to control the kinetic energy release and grain growth rate during recrystallization, thereby alleviating abnormal grain coarsening and ensuring that the average grain size of the strip after gradient annealing is stably within the above range. This improves the uniformity and fineness of the recrystallized structure, thus providing a good grain foundation for the foil rolling process. It is also conducive to promoting the efficient formation and stable retention of S-texture, R-texture and Copper texture, and ultimately achieving synergistic optimization between high flexibility and excellent heat resistance of copper foil.

[0033] In the preferred gradient annealing process, the temperature difference between each heating stage is 80-120℃, and the selection of each annealing point is specifically optimized. The low temperature (180-220℃) is at the initial recrystallization stage, where recrystallization nucleation occurs but grain growth does not occur due to the low temperature. At the medium temperature (280-320℃), grain size grows and becomes homogenized. At the high temperature (360-400℃), the strip completes sufficient recrystallization. This gradient annealing process helps refine and homogenize the grain size of the strip, reducing grain coarsening or abnormal grain growth. This provides a good microstructure for subsequent foil rolling, enabling control over the grain size and texture of the foil, and ultimately improving the flexibility and bending performance of the rolled copper foil.

[0034] In one embodiment of this application, in step S2 above, the deformation amount of rough rolling is 60~90%; and / or, the deformation amount of finish rolling is 85~95%; and / or, the foil rolling method is multi-pass cold rolling, the total reduction rate of foil rolling is ≥92%, preferably 95~99%, and the single-pass reduction rate of foil rolling is 5~15%; the surface roughness Ra of the work rolls in foil rolling is <0.05μm; the surface roughness Ra of the foil material after foil rolling is <0.1μm; the average grain size of the foil material after foil rolling is <15μm, preferably 5~10μm; and / or, the S{123} in the foil material after foil rolling <634> Texture, R{124} <211> Texture and Copper{112} <111> The total volume percentage of the texture is >50%, preferably 60-80%; S{123} in the foil material after foil rolling <634> The volume percentage of the texture is >30%, preferably 35~45%.

[0035] Preferably, the deformation amount in rough rolling is within the aforementioned range, which helps to establish a high-density dislocation and strong deformation texture foundation in the strip, providing sufficient recrystallization nucleation driving force for subsequent gradient annealing, thereby obtaining a uniform fine-grained structure. Preferably, the deformation amount in finish rolling is within the aforementioned range, which helps to further optimize the texture orientation distribution and provide structural stability for the high total reduction rate deformation in the foil rolling stage. Preferably, rough rolling and finish rolling are each independently cold rolling. Using multi-pass cold rolling in the foil rolling stage and controlling the total reduction rate and single-pass reduction rate within the aforementioned range helps to alleviate abnormal grain growth and surface defect accumulation caused by local strain concentration under high deformation. At the same time, in conjunction with the surface roughness Ra of the work rolls within the aforementioned range, it helps to reduce surface scratches and micro-stress concentration of the foil, thereby enabling the foil to maintain a uniform microstructure even under high cumulative deformation.

[0036] Preferred control of S{123} in the foil material after foil rolling <634> Texture, R{124} <211> Texture and Copper{112} <111> The total volume ratio of texture and S{123} <634> The volumetric proportion of the texture helps to soften and further enhance the flexibility of the rolled copper foil.

[0037] In one embodiment of this application, in step S2 above, the surface treatment process includes sequentially performing degreasing and cleaning, reddening treatment or blackening treatment; and / or, the softening annealing temperature is 180~200℃, and the softening annealing time is 0.5~2h.

[0038] The above surface treatments effectively remove oil and impurities from the copper foil surface and form a uniform and stable oxide layer structure. This provides a clean surface environment with controllable interfacial energy for subsequent softening annealing, reducing the interference of surface contamination on grain boundary migration during recrystallization. Specifically, the red coating treatment involves electroplating a pure copper layer, a Zn layer, and a Cr layer onto the material surface. This reddish film enhances adhesion to the substrate, oxidation resistance, and etching controllability, thereby improving the bond strength between the copper foil and the insulating substrate without affecting conductivity. The black coating treatment involves electroplating a nickel / cobalt / zinc-based black alloy layer (forming a nano-column / dendritic "light trap" structure) onto the material surface, achieving high blackness, matte finish, heat resistance, corrosion resistance, and high adhesion. This film has higher surface roughness and stronger chemical anchoring, making it suitable for flexible circuits in high-flexibility and high-thermal-cycle environments, thus enhancing the interfacial adhesion between the copper foil and the substrate and its heat-resistant peeling performance.

[0039] Preferably controlling the softening annealing temperature and time within the above range helps to further promote the formation of the cube texture of the copper foil without destroying the original S texture, R texture and Copper texture, thereby achieving an optimized balance between heat resistance and flexibility without pinning grain boundaries.

[0040] In another typical embodiment of this application, an application of rolled copper foil in a flexible circuit board is provided, wherein the rolled copper foil is the rolled copper foil described above.

[0041] The rolled copper foil of this application has moderate heat resistance and excellent flexibility, thus better meeting the long-term service requirements of flexible circuits under repeated bending conditions.

[0042] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0043] Example 1

[0044] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0045] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 4ppm.

[0046] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 800℃, with a total deformation of 80%, of which the deformation of each pass in the 5th and 6th passes is 36%. Then, it is hot rolled for 4 passes at 500℃, with a total deformation of 50% and a deformation of 15% per pass, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0047] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0048] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0049] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0050] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 99.4%, the single reduction rate is 10%, and the surface roughness Ra of the work roll is 0.02μm, resulting in foil material with a surface roughness Ra of 0.6μm.

[0051] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and reddened, and then softened and annealed at 185°C for 1 hour to obtain rolled copper foil.

[0052] Example 2

[0053] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0054] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 4ppm.

[0055] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 850℃, with a total deformation of 80%, of which the deformation per pass in passes 5 and 6 is 36%. Then, it is hot rolled for 3 passes at 500℃, with a total deformation of 50% and a deformation per pass of 15%, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0056] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0057] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0058] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0059] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 98.8%, the single-pass reduction rate is 10%, and the surface roughness Ra of the work roll is 0.03μm, resulting in foil material with a surface roughness Ra of 0.65μm.

[0060] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 185°C for 1 hour to obtain rolled copper foil.

[0061] Example 3

[0062] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0063] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 5ppm.

[0064] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 850℃, with a total deformation of 80%, of which the deformation per pass in passes 5 and 6 is 36%. Then, it is hot rolled for 3 passes at 500℃, with a total deformation of 50% and a deformation per pass of 15%, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0065] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0066] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0067] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0068] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 98.5%, the single reduction rate is 10%, and the surface roughness Ra of the work roll is 0.05μm, resulting in foil material with a surface roughness Ra of 0.8μm.

[0069] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 190°C for 1 hour to obtain rolled copper foil.

[0070] Example 4

[0071] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0072] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 6 ppm.

[0073] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 850℃, with a total deformation of 80%, of which the deformation per pass in passes 5 and 6 is 38%. Then, it is hot rolled for 3 passes at 550℃, with a total deformation of 50% and a deformation per pass of 15%, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0074] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0075] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0076] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0077] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 98.2%, the single reduction rate is 10%, and the surface roughness Ra of the work roll is 0.05μm, resulting in foil material with a surface roughness Ra of 0.9μm.

[0078] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 190°C for 1 hour to obtain rolled copper foil.

[0079] Example 5

[0080] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0081] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 7ppm.

[0082] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 850℃, with a total deformation of 80%, of which the deformation per pass in passes 5 and 6 is 36%. Then, it is hot rolled for 3 passes at 550℃, with a total deformation of 50% and a deformation per pass of 15%, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0083] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0084] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0085] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0086] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 97.5%, the single reduction rate is 10%, and the surface roughness Ra of the work roll is 0.05μm, resulting in foil material with a surface roughness Ra of 1.1μm.

[0087] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 195°C for 1 hour to obtain rolled copper foil.

[0088] Example 6

[0089] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0090] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 8 ppm.

[0091] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 850℃, with a total deformation of 80%, of which the deformation per pass in passes 5 and 6 is 36%. Then, it is hot rolled for 3 passes at 550℃, with a total deformation of 50% and a deformation per pass of 15%, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0092] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0093] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0094] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0095] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 96.5%, the single reduction rate is 10%, and the surface roughness Ra of the work roll is 0.05μm, resulting in foil material with a surface roughness Ra of 1.2μm.

[0096] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and reddened, and then softened and annealed at 195°C for 1 hour to obtain rolled copper foil.

[0097] Example 7

[0098] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0099] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 10ppm.

[0100] (2) Gradient hot rolling: The ingot is hot rolled for 6 passes at 850℃, with a total deformation of 80%, of which the deformation per pass in passes 5 and 6 is 36%. Then, it is hot rolled for 3 passes at 550℃, with a total deformation of 50% and a deformation per pass of 15%, to obtain a gradient hot-rolled strip with a thickness of 18mm.

[0101] (3) Rough rolling: The strip blank with a thickness of 16.5 mm after milling is rough rolled (cold rolled) to 1.0 mm with a deformation of 94%, and the strip blank is obtained after rough rolling.

[0102] (4) Gradient annealing: The strip after rough rolling is heated from room temperature to 200℃ and held for 2 hours, then heated to 300℃ for the first annealing for 2 hours, and then heated to 380℃ for the second annealing for 2 hours to obtain the strip after gradient annealing.

[0103] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0104] (6) Foil rolling: The finished strip is rolled into foil. A cold rolling method with high total reduction rate and multiple small reduction rates is adopted. The total reduction rate is 95%, the single reduction rate is 10%, and the surface roughness Ra of the work roll is 0.05μm, resulting in foil material with a surface roughness Ra of 1.15μm.

[0105] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 200°C for 1 hour to obtain rolled copper foil.

[0106] Example 8

[0107] The difference from Example 1 is that the total content of La and P elements is 88 ppm, the mass ratio of La to P elements is 3:1, and finally rolled copper foil is obtained.

[0108] Example 9

[0109] The difference from Example 1 is that the total content of La and P elements is 88 ppm, the mass ratio of La to P elements is 1:3, and finally rolled copper foil is obtained.

[0110] Example 10

[0111] The difference from Example 1 is that gradient hot rolling: the ingot is hot rolled in 7 passes at 850°C, with a total deformation of 85%, of which the deformation per pass in passes 5 and 6 is 35%, and then hot rolled in 3 passes at 550°C, with a total deformation of 40% and a deformation per pass of 10%, to obtain a gradient hot-rolled strip, and finally rolled copper foil.

[0112] Example 11

[0113] The difference from Example 1 is that gradient hot rolling: the ingot is hot rolled in four passes at 850°C, with a total deformation of 70%, of which the deformation per pass in the fourth pass is 25%. Then, it is hot rolled in five passes at 500°C, with a total deformation of 65% and a deformation per pass of 25%, to obtain a gradient hot-rolled strip, which is finally rolled copper foil.

[0114] Example 12

[0115] The difference from Example 1 is that gradient annealing: the rough-rolled strip is heated from room temperature to 220°C and held for 2 hours, then heated to 320°C for the first annealing for 2 hours, and then heated to 400°C for the second annealing for 2 hours to obtain the gradient annealed strip, and finally rolled copper foil.

[0116] Example 13

[0117] The difference from Example 1 is that gradient annealing: the rough-rolled strip is heated from room temperature to 180°C and held for 2 hours, then heated to 320°C for the first annealing for 2 hours, and then heated to 360°C for the second annealing for 1 hour to obtain the gradient annealed strip, and finally rolled copper foil.

[0118] Example 14

[0119] The difference from Example 1 is that the foil rolling process involves foil rolling of the finished strip blank using a cold rolling method with a high total reduction rate and multiple passes with low reduction rates. The total reduction rate is 92%, the single pass reduction rate is 5%, and the surface roughness Ra of the work roll is 0.05 μm. This process yields foil material after foil rolling, and finally, rolled copper foil.

[0120] Example 15

[0121] The difference from Example 1 is that the foil rolling process involves foil rolling of the finished strip blank using a cold rolling method with a high total reduction rate and multiple passes with low reduction rates. The total reduction rate is 90%, the single pass reduction rate is 20%, and the surface roughness Ra of the work roll is 0.08 μm. This process yields foil material after foil rolling, and finally, rolled copper foil.

[0122] Comparative Example 1

[0123] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0124] (1) Melting and casting: Electromagnetic-assisted continuous casting is used to melt and cast the raw material of rolled copper foil to obtain ingots, wherein the oxygen content of the copper liquid is 3ppm.

[0125] (2) Hot rolling: The ingot is hot rolled at 850°C to obtain a hot-rolled strip with a thickness of 16 mm.

[0126] (3) Rough rolling: The hot-rolled strip with a thickness of 14.5 mm after milling is rough rolled (cold rolled) with a deformation of 83.3% to obtain the rough-rolled strip.

[0127] (4) Annealing: The strip after rough rolling is heated from room temperature to 400℃ and held for 6 hours to obtain the annealed strip.

[0128] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.1 mm to obtain the finished strip.

[0129] (6) Foil rolling: The strip after precision rolling is rolled into foil material with a thickness of 12μm.

[0130] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 165°C for 1 hour to obtain rolled copper foil.

[0131] Comparative Example 2

[0132] The elemental composition and content of the rolled copper foil are shown in Table 1. Its preparation process is as follows:

[0133] (1) Melting and casting: The raw material of rolled copper foil is melted and cast by continuous casting to obtain ingots, wherein the oxygen content of the copper liquid is 168ppm.

[0134] (2) Hot rolling: The ingot is hot rolled at 850°C to obtain a hot-rolled strip with a thickness of 16 mm.

[0135] (3) Rough rolling: The hot-rolled strip with a thickness of 14.5 mm after milling is rough rolled (cold rolled) with a deformation of 91.7% to obtain the rough-rolled strip.

[0136] (4) Annealing: The strip after rough rolling is heated from room temperature to 400℃ and held for 6 hours to obtain the annealed strip.

[0137] (5) Finish rolling: The strip after gradient annealing is finished (cold rolled) to 0.2 mm to obtain the finished strip.

[0138] (6) Foil rolling: The strip after precision rolling is rolled into foil material with a thickness of 35μm.

[0139] (7) Surface treatment: After the foil is rolled, it is degreased, cleaned and blackened, and then softened and annealed at 260°C for 1 hour to obtain rolled copper foil.

[0140] Comparative Example 3

[0141] The difference from Example 1 is that the elemental composition and content of the rolled copper foil are different, as shown in Table 1, and the rolled copper foil is finally obtained.

[0142] Comparative Example 4

[0143] The difference from Example 1 is that gradient hot rolling: the ingot is subjected to 6 passes of first hot rolling at 750°C, and then 3 passes of second hot rolling at 600°C to obtain gradient hot-rolled strip, and finally rolled copper foil.

[0144] Comparative Example 5

[0145] The difference from Example 1 is that gradient annealing: the rough-rolled strip is heated from room temperature to 250°C and held for 2 hours, then heated to 350°C for the first annealing for 2 hours, and then heated to 450°C for the second annealing for 2 hours to obtain the gradient annealed strip, and finally rolled copper foil.

[0146] Test method:

[0147] Grain orientation determination method: According to the test requirements, longitudinal section samples in cast solid solution state and finished state are selected for EBSD (electron backscatter diffraction) measurement. Using EBSD data analysis software, the proportion of each crystal orientation is statistically analyzed within the measurement area, provided that the tolerance angle of each crystal orientation is within 15°.

[0148] Method for determining average grain size: Select longitudinal cross-section samples in cast, solution, and finished states according to testing requirements and perform EBSD (electron backscatter diffraction) measurement. Select appropriate test area and step size for each state, and regard the boundary with an orientation tolerance of 5° as the grain boundary to statistically measure the average grain size.

[0149] Heat resistance temperature test: The copper foil is kept at a set temperature for 1 hour, and after cooling, the hardness value of the copper foil is tested. The heat resistance performance is determined by comparing the hardness values ​​before and after the treatment. The treatment temperature when the hardness value after the treatment is 80% of that before the treatment is the heat resistance temperature.

[0150] Flexural performance test: The flexural performance test is carried out on a flexural life testing machine. A sample with a width of 25mm is cut along the MD direction, the flexural radius r is 2.5mm, the stroke is 40mm, and the frequency is 180 times / minute.

[0151] The test results are shown in Tables 2 and 3.

[0152] Table 1

[0153]

[0154] Table 2

[0155]

[0156] Table 3

[0157]

[0158] As can be seen from the above, compared with Comparative Examples 1 and 2, the embodiments of this application can simultaneously improve the heat resistance and flexibility of rolled copper foil by controlling the content of elements and the preparation method. The element content of Comparative Example 3 is not within the range of this application, and there are grain coarsening and abnormal growth phenomena. The gradient hot rolling temperature of Comparative Example 4 is not within the range of this application, and there is a problem of large grain size in the hot-rolled strip. The gradient annealing temperature of Comparative Example 5 is not within the range of this application, and there is a problem of grain size coarsening in both the strip and the foil.

[0159] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0160] This application, by controlling the elemental composition and content of rolled copper foil within the aforementioned range, can improve its heat resistance while simultaneously reducing the Cube{001} content in the rolled copper foil (after softening and annealing). <100> The texture (cube texture) and average grain size reach the above-mentioned range, thus preventing wrinkles caused by rapid softening in subsequent applications of rolled copper foil, and giving the copper foil good flexibility and bending properties. Specifically, the addition of Ag element enables it to form a solid solution with Cu, thereby significantly improving the conductivity and ductility of rolled copper foil, while increasing the deformation texture retention rate, which is beneficial to S{123} <634> The formation of S-texture improves the heat resistance of rolled copper foil. If the Ag element content is below 50 ppm, the improvement is not significant; if the Ag element content is above 400 ppm, it leads to a significant increase in the cost of the copper foil and excessively high heat resistance temperature. Therefore, this application controls the Ag element content within the above range to balance cost, conductivity, and heat resistance. Phosphorus (P) is a good deoxidizer and can synergistically work with La to achieve joint deoxidation while also promoting the transformation of S-texture during deformation and cubic texture during recrystallization annealing. Trace amounts of P can improve the heat resistance of rolled copper foil and purify grain boundaries, thereby improving deformation uniformity and enhancing S-texture. If the P element content is below 10 ppm, the deoxidation effect is insufficient, and the improvement in heat resistance is limited; if the P element content is above 100 ppm, it inhibits recrystallization and reduces the average grain size of the rolled copper foil. Therefore, controlling the phosphorus (P) content within the aforementioned range can improve the heat resistance of rolled copper foil and ensure its average grain size reaches the above range. La (La) can synergistically deoxidize with P, simultaneously refining grains, purifying grain boundaries, and reducing impurity segregation, thereby improving the oxidation resistance and corrosion resistance of rolled copper foil, as well as enhancing the sulfur texture. If the La addition is below 20 ppm, the effect of refining ingot grains and purifying grain boundaries is insufficient; if the La addition is above 100 ppm, rare earth compound inclusions will form, thus inhibiting recrystallization. Therefore, controlling the La addition within the aforementioned range can improve the oxidation performance and corrosion resistance of rolled copper foil. Further controlling the total mass content of P and La, as well as the total content of other impurity elements, within the aforementioned range can avoid the risk of excessive alloying elements hindering grain growth during recrystallization. Adding the aforementioned amount of oxygen (O) can form trace oxides with P and La, playing a role in refining grains and improving deformation uniformity. In summary, the rolled copper foil of this application has both good heat resistance and excellent flexibility, making it suitable for applications with stringent requirements for thermal stability and dynamic bending performance, such as high-reliability flexible circuits, automotive electronics, and 5G communications.

[0161] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rolled copper foil, characterized by, The rolled copper foil comprises the following elements: 50~400ppm Ag; 20~100ppm P; 20~100ppm La; 3~10ppm O, with the total content of unavoidable impurities ≤100ppm, and the remainder being Cu; the total mass content of the P and La elements is <100ppm. The heat resistance temperature of the rolled copper foil is 180~200℃, and the Cube{001} in the rolled copper foil <100> The volume fraction of the texture is >80%, and the average grain size of the rolled copper foil is >200μm.

2. The rolled copper foil according to claim 1, characterized by The rolled copper foil comprises the following elements: 100~350ppm of Ag; 22~80ppm of P; 30~90ppm of La; 4~10ppm of O; the total content of unavoidable impurities is ≤100ppm; and the remainder is Cu; the total mass content of P and La is <100ppm. The heat resistance temperature of the rolled copper foil is 185~200℃, and the Cube{001} in the rolled copper foil... <100> The volume fraction of the texture is 81-95%, and the average grain size of the rolled copper foil is 210-480 μm.

3. The rolled copper foil according to claim 1 or 2, characterized in that, The mass ratio of the La element to the P element is (1~3):1; And / or, the surface roughness Rz of the rolled copper foil is <1.5μm; and / or, the thickness of the rolled copper foil is 9~50μm.

4. A method of producing the rolled copper foil according to any one of claims 1 to 3, characterized by, The preparation method includes: Step S1: Melt and cast the raw material corresponding to the rolled copper foil to obtain an ingot; the average grain size of the ingot is ≤800μm; Step S2: The ingot is subjected to gradient hot rolling, rough rolling, gradient annealing, fine rolling, foil rolling, surface treatment and softening annealing in sequence to obtain the rolled copper foil; The gradient hot rolling process includes performing a first hot rolling at 800~850℃ and a second hot rolling at 500~550℃. The gradient annealing process includes: holding at 180~220℃, raising the temperature to 280~320℃ for the first annealing, and continuing to raise the temperature to 360~400℃ for the second annealing.

5. The preparation method according to claim 4, characterized in that, In step S1, the oxygen content of the copper melt in the casting is 3~10ppm; and / or, the casting method is electromagnetic assisted continuous casting; and / or, the average grain size of the ingot is 500~800μm.

6. The preparation method according to claim 4, characterized in that, In step S2, the first hot rolling has 5 to 7 passes, the total deformation of the first hot rolling is 75 to 85%, and the deformation per pass of the first hot rolling is 30 to 40%; the second hot rolling has 2 to 4 passes, the total deformation of the second hot rolling is 40 to 60%, and the deformation per pass of the second hot rolling is 10 to 20%; the average grain size of the strip after gradient hot rolling is <40 μm.

7. The preparation method according to any one of claims 4 to 6, characterized in that, In step S2, the gradient annealing process includes: holding at 180~220℃ for 1~3h, raising the temperature to 280~320℃ for the first annealing for 1~3h, and continuing to raise the temperature to 360~400℃ for the second annealing for 1~3h; the average grain size of the strip after gradient annealing is <20μm.

8. The production method according to any one of claims 4 to 6, characterized by, In step S2, the deformation amount of the rough rolling is 60-90%; And / or, the deformation amount of the finishing roll is 85-95%; And / or, the foil rolling method is multi-pass cold rolling, the total reduction rate of the foil rolling is ≥92%, the single-pass reduction rate of the foil rolling is 5~15%; the surface roughness Ra of the work rolls in the foil rolling is <0.05μm; the surface roughness Ra of the foil material after foil rolling is <0.1μm; the average grain size of the foil material after foil rolling is <15μm; And / or, S{123} in the foil material after foil rolling <634> Texture, R{124} <211> Texture and Copper{112} <111> The total volume percentage of the texture is >50%, preferably 60-80%; the S{123} in the foil material after foil rolling <634> The volume percentage of the texture is >30%, preferably 35~45%.

9. The production method according to any one of claims 4 to 6, characterized by, In step S2, the surface treatment process includes sequentially performing degreasing cleaning, reddening treatment, or blackening treatment. And / or, the softening annealing temperature is 180~200℃, and the softening annealing time is 0.5~2h.

10. An application of rolled copper foil in flexible circuit boards, characterized in that, The rolled copper foil is the rolled copper foil according to any one of claims 1 to 3.

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