A high-flexibility rolled copper foil with high {100} texture content and its preparation method

Abstract

This invention discloses a high-flexibility rolled copper foil with high {100} texture content and its preparation method. Pure tin and pure silver are added to molten copper to obtain a copper alloy melt. The copper alloy melt is then semi-continuously cast to obtain an oxygen-containing copper ingot. The ingot is hot-rolled and water-quenched after hot rolling to obtain a hot-rolled billet. The hot-rolled billet is milled and then subjected to rough rolling, annealing, finish rolling, and two-stage annealing to obtain the high-flexibility rolled copper foil provided by this invention. After grain reconstruction through rolling and annealing processes, the orientation of adjacent grains tends to be consistent. During copper foil deformation, dislocations can easily cross-move to adjacent grains, preventing dislocation accumulation at grain boundaries. Simultaneously, grain growth further improves the consistency of orientation between adjacent grains, thereby significantly enhancing flexibility.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing, and in particular to a high-flexibility rolled copper foil with high {100} texture content and its preparation method. Background Technology

[0002] Industrial copper foil can be divided into two categories based on its manufacturing process: rolled copper foil and electrolytic copper foil. The former is mainly used for flexible circuit boards and high-frequency circuit boards, while the latter is mainly used for circuit boards with lower flexibility requirements. Rolled copper foil (RA copper foil) is an extremely thin copper material made from thin strips of copper, pure copper, oxygen-toughened copper, or copper alloys through a cyclic process of rolling-annealing-rolling-annealing. Its thickness ranges from 6-40 micrometers, and its width from 100-750 millimeters. Rolled copper foil exhibits significantly superior ductility, bending resistance, conductivity, and low surface roughness and profile compared to electrolytic copper foil. The production process involves semi-continuous casting, hot rolling, cold roughing rolling, annealing, multi-roll cold finishing rolling, foil rolling, and annealing. Multi-roll cold finishing mills are mainly 20-roll, 18-roll, or 14-roll mills, with the X-6 roll mill being the most commonly used. Key technologies include thickness control, rolling tension, and surface treatment. Applications cover flexible copper clad laminates, smart wearables, 5G / 6G communications, electromagnetic shielding, lithium battery anode materials, flexible electronics, and smart cars. Domestic production of rolled copper foil started relatively late, with annual output ranging from 20,000 to 30,000 tons.

[0003] Currently, smart wearables, 5G / 6G communications, electromagnetic shielding, flexible electronics, and smart cars have created a high-quality, high-volume demand for highly flexible rolled copper foil. By changing the rolling process conditions, the recrystallized structure of the rolled copper foil exhibits a well-developed cubic texture, with small inclination angles at the grain boundaries and coarse grains. This type of rolled copper foil exhibits significantly improved flexibility, with a bending frequency four times higher than that of ordinary rolled copper foil. The {100} texture can regulate the initiation and coordinated deformation capabilities of the slip system, thereby significantly improving the flexibility. This is because, in face-centered cubic copper, plastic deformation mainly occurs through atoms along the closest packing direction on the closest-packed plane {111}. <110> This is achieved through slip. Copper has a total of 12 potential slip systems (4 {111} planes × 3 on each plane). <110> (Direction). However, whether a slip system is activated under external stress depends on its Schmidt factor. The rolling direction (RD) and transverse direction (TD) of the copper foil are in the bending plane, while the normal direction (ND) is subjected to tensile-compressive stress cycles. For {100} <001> The textured grains, with their {100} planes parallel to the rolling plane (i.e., the foil surface), exhibit highly favorable angle relationships between the four {111} slip planes and the stress axis when the bending stress is perpendicular to the surface (i.e., along the ND direction). <100> In the ND direction, eight slip systems of the grain have the same and relatively high Schmidt factor (approximately 0.41). Under bending stress, the {100} grain has multiple equivalent, easily activated slip systems that can be simultaneously engaged. This contrasts with other common rolling textures, such as those found in copper molds {112}. <111> Brass {110} <112> Typically, only 2-4 slip systems are dominant, while the Schmitt factors of other systems are very small. The simultaneous operation of multiple slip systems avoids excessive strain in localized areas. Increasing the proportion of {100} texture in rolled copper foil essentially optimizes the deformation mechanism of its micrograins under bending stress. {100} oriented grains possess numerous slip systems with high Schmitt factors and near-equivalent properties under bending stress perpendicular to the foil surface. This multi-slip mechanism results in more uniform and coordinated plastic deformation. It significantly reduces localized stress concentration during deformation, effectively suppressing the initiation and propagation of fatigue cracks. The flexural properties of the copper foil, i.e., its bending fatigue life, are significantly improved, enabling the production of high-performance rolled copper foil specifically for high-reliability flexible circuit applications.

[0004] Currently, my country's high-flexibility rolled copper foil preparation technology is immature, and high-flexibility rolled copper foil can only rely on imports. How to prepare copper foil with high {100} texture through synergistic optimization and innovation of the process is the key to improving the high-flexibility performance of copper foil. Summary of the Invention

[0005] The first objective of this invention is to provide a method for preparing high-flexibility rolled copper foil with high {100} texture content.

[0006] The second objective of this invention is to provide a high-flexibility rolled copper foil with high {100} texture content prepared by the above-described preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention discloses a method for preparing high-flexibility rolled copper foil with high {100} texture content. Pure tin and pure silver are added to molten copper and smelted to obtain a copper alloy melt. The copper alloy melt is cast to obtain an oxygen-containing copper base material ingot that meets the required indicators. The oxygen-containing copper base material ingot is hot-rolled and then water-quenched to obtain a hot-rolled billet. The hot-rolled billet is milled and then subjected to rough rolling, annealing, fine rolling, and double-stage annealing to obtain the final product.

[0009] During the finishing rolling process, the deformation per pass is controlled at 5-10%, and the total deformation is 80-99%.

[0010] The two-stage annealing process involves first heating to 160-200℃ and holding for 15-90 minutes, then heating to 260-320℃ and holding for 30-90 minutes.

[0011] The method for preparing high-flexibility rolled copper foil with high {100} texture content provided by this invention employs a small-pass deformation combined with a large total cold rolling deformation during fine rolling, which increases the number of S-texture and copper deformation texture in the processed copper. Subsequently, during the finished product annealing process, a two-stage annealing process is used. First, annealing is carried out at a moderate temperature to promote the formation of a large number of cube-oriented nuclei, forming fine and uniform recrystallized grains. Then, a final annealing is carried out at a higher temperature and a longer holding time to promote the selective and rapid growth of fine cube grains while inhibiting the growth of grains with other orientations, ultimately obtaining more {100} texture. After grain reconstruction, the orientation of adjacent grains tends to be consistent, and dislocations can easily cross-move to adjacent grains during copper foil deformation, preventing dislocations from accumulating at grain boundaries. At the same time, grain growth further improves the consistency of orientation of adjacent grains, thereby significantly improving the flexibility performance.

[0012] In a preferred embodiment, the high-flexibility rolled copper foil has the following composition by mass percentage: Ag 0.005-0.015%, Sn 0.002-0.005%, O 0.015-0.025%, with the balance being Cu and unavoidable impurities.

[0013] Experiments revealed that adding trace amounts of Ag and Sn, while controlling the O mass fraction within the range specified in this invention, resulted in the highest final {100} texture content. If the Ag and Sn contents were too low, it would be difficult to effectively regulate the recrystallization behavior, grain boundary migration, grain growth, and texture evolution of the copper matrix, thus hindering the nucleation and preferential growth of Cube / {100} oriented grains during subsequent annealing. Conversely, excessively high contents would increase the alloying degree of the copper matrix, increase rolling deformation resistance, and potentially reduce the conductivity and plasticity of the copper foil, making it difficult to achieve a balance between high {100} texture proportion, large grain structure, and high flexural performance. Therefore, this invention limits the Ag content to 0.005-0.015% and the Sn content to 0.002-0.005% to achieve a better balance between texture control, grain growth, conductivity, plasticity, and cost.

[0014] The preferred method involves using cathode copper as raw material, calcining it under charcoal cover, holding it at 1180-1220℃ for 20-40 minutes to obtain copper liquid, adding pure tin and pure silver to the copper liquid, removing the calcined charcoal, and smelting it under atmospheric conditions for 10-40 minutes to obtain copper alloy melt.

[0015] In this invention, through the above-mentioned smelting process, the proportion of O in the copper alloy melt is controlled to be 0.015-0.025%, and the contents of Fe, P, and S are less than 3 ppm.

[0016] In a preferred embodiment, the casting method is semi-continuous casting, wherein the semi-continuous casting temperature is 1180℃-1200℃ and the casting speed is 7-9m / h. Through semi-continuous casting, oxygen-containing copper base material ingots meeting the required specifications are obtained.

[0017] In a preferred embodiment, the initial rolling temperature of the hot rolling is 800-850℃, and the final rolling temperature is 600℃ or higher. Experiments have shown that by using higher initial and final rolling temperatures during hot rolling, and by water quenching after hot rolling, the grain size of the hot-rolled strip can be appropriately increased, the number of grain boundaries can be reduced, and the grain structure can be made more uniform.

[0018] In a preferred embodiment, the total shaping amount of the rough rolling is 50-70%.

[0019] In a preferred embodiment, the annealing temperature is 500-550℃, and the annealing time is 8-10 hours. Experiments have shown that controlling the annealing temperature and time within this range yields a uniform recrystallized structure and provides a good microstructure foundation for the subsequent formation of a high proportion of cube{100} texture, maximizing the final proportion of the cube{100} texture. If the annealing temperature is too low, the recrystallization of the deformed structure is insufficient, residual work hardening is severe, and uneven deformation occurs during subsequent cold rolling. During final annealing, cube-oriented grains struggle to fully nucleate and selectively grow, thus reducing the proportion of the {100} texture. If the annealing temperature is too high, the intermediate grains grow excessively, leading to uneven energy storage distribution during subsequent cold rolling and potentially weakening the accumulation of S-texture and Copper texture, which are conducive to cube texture formation. During final annealing, non-cube-oriented grains compete for growth, further reducing the proportion of the {100} texture.

[0020] In a preferred embodiment, the deformation per pass of the finishing rolling is 5-7%, and the total deformation is 93-96%.

[0021] In a preferred embodiment, the two-stage annealing process involves first heating to 180-200℃ and holding for 15-90 minutes, and then heating to 280-300℃ and holding for 30-90 minutes.

[0022] After two-stage annealing, the average grain size of the rolled copper foil is 47-56μm, with the highest {100} content reaching over 94%.

[0023] The present invention also provides a high-flexibility rolled copper foil with high {100} texture content prepared by the above preparation method.

[0024] In a preferred embodiment, the proportion of {100} texture in the high-flexibility rolled copper foil is 50-95%, preferably 80-95%.

[0025] Principles and advantages

[0026] The method for preparing high-flexibility rolled copper foil with high {100} texture content provided by this invention involves obtaining an ingot through smelting and semi-continuous casting, followed by hot rolling. The grain size of the hot-rolled strip is appropriately increased, and water quenching is used to reduce the number of grain boundaries and achieve uniform grain structure. The hot rolling temperature of the copper ingot is increased to approximately 850°C, resulting in a large grain size after final rolling. Because the original microstructure already has relatively coarse grains, they tend to grow even larger under the same annealing process. During finishing rolling, a small number of passes combined with a large total cold rolling deformation promotes an increase in the number of S-texture and copper deformation textures in the processed copper. Subsequently, a two-stage annealing process is used in the finished product annealing process. First, annealing is performed at a moderate temperature to promote the formation of a large number of cube-oriented nuclei, resulting in fine and uniform recrystallized grains. Then, final annealing is performed at a higher temperature and a longer holding time to promote the selective and rapid growth of fine cube grains while inhibiting the growth of grains with other orientations, ultimately obtaining more {100} texture. After grain reconstruction, the orientation of adjacent grains tends to be consistent, and dislocations can easily cross-move to adjacent grains when the copper foil is deformed, preventing dislocations from accumulating at grain boundaries. At the same time, grain growth further improves the consistency of orientation of adjacent grains, thereby significantly improving the flexural performance. Attached Figure Description

[0027] Figure 1 The foil rolled to a thickness of 18 μm at a processing rate of 5% in Example 1 corresponds to a total processing rate of 95%, and the {100} texture ratio diagram is shown for heat treatment at 200℃ / 60min + 300℃ / 90min.

[0028] Figure 2 The foil rolled to a thickness of 18 μm at a processing rate of 5% in Example 3 corresponds to a total processing rate of 95%, and the {100} texture ratio diagram is shown for heat treatment at 180℃ / 30min + 280℃ / 60min.

[0029] Figure 3 The image shows the texture percentage of the foil rolled to 18 μm thickness at a processing rate of 5% in Example 4, with a total processing rate of 95%, and the heat treatment process at 160℃ / 30min + 260℃ / 60min. Detailed Implementation

[0030] Example 1

[0031] Using cathode copper as raw material, smelting is carried out under the condition of calcined charcoal covering. After melting, it is held at 1200℃ for 20 minutes, Ag and Sn are added, the calcined charcoal is removed, and it is held at atmospheric temperature for 30 minutes. The Ag is adjusted to 0.01%, Sn to 0.005%, and O to 0.020%, while controlling the content of Fe, P, and S to be below 3ppm. Semi-continuous casting is then performed. The second semi-continuous casting is carried out at a casting temperature of 1200℃ and a casting speed of 9m / h to obtain oxygen-containing copper base material ingots that meet the required indicators.

[0032] Third: hot rolling, the copper ingot is hot rolled at 850℃, the final rolling temperature is 650℃, water quenching, and milling.

[0033] Fourth: Rough rolling + annealing. Rough rolling, total deformation 60% → 500℃ / annealing for 9 hours.

[0034] Fifth: The finishing rolling process is carried out at pass rates of 5%, 7%, 8.5% and 10% respectively to roll foil to a thickness of 18μm, with a corresponding total processing rate of 95%.

[0035] Sixth: Two-stage annealing, heat treatment at 200℃ / 60min + 300℃ / 90min, with a pass deformation rate of 5%. The minimum grain size of the sample was 3.1μm, the maximum grain size was 530μm, and the average grain size was 56μm. The {100} texture ratio is shown in Table 1.

[0036] Table 1

[0037]

[0038] Example 2

[0039] Using cathode copper as raw material, smelting was carried out under calcined charcoal covering. After melting, the temperature was held at 1200℃ for 20 min, Ag and Sn were added, the calcined charcoal was removed, and the temperature was held at atmospheric conditions for 30 min. The Ag content was adjusted to 0.015%, Sn to 0.005%, and O to 0.025%, while controlling the Fe, P, and S contents to be below 3 ppm. Semi-continuous casting was then performed.

[0040] Second: Semi-continuous casting, casting temperature 1200℃, casting speed 9m / h, to obtain oxygen-containing copper base material ingots that meet the required specifications.

[0041] Third: hot rolling, the copper ingot is hot rolled at 830℃, the final rolling temperature is 620℃, water quenching, and milling.

[0042] Fourth: Rolling + Annealing, rough rolling, deformation 60% → 500℃ / annealing for 9 hours.

[0043] Fifth: Finish rolling, rolling to 18μm thick foil at pass rates of 5%, 7%, 8.5% and 10% respectively, with a total processing rate of 95%.

[0044] Sixth: Two-stage annealing, 180℃ / 60min + 280℃ / 90min heat treatment, with a pass rate of 5%, resulted in a minimum grain size of 2.8μm and a maximum grain size of 520μm. The average grain size was 52μm, as shown in Table 2.

[0045] Table 2

[0046]

[0047] Example 3

[0048] Using cathode copper as raw material, smelting was carried out under calcined charcoal covering. After melting, the temperature was held at 1200℃ for 20 min, Ag and Sn were added, the calcined charcoal was removed, and the temperature was held at atmospheric conditions for 30 min. The Ag, Sn, and O values ​​were adjusted to 0.015%, 0.005%, and 0.025%, while controlling the Fe, P, and S contents to be below 3 ppm. Semi-continuous casting was then performed.

[0049] Second: Semi-continuous casting, casting temperature 1220℃, casting speed 7m / h, to obtain oxygen-containing copper base material ingots that meet the required specifications.

[0050] Third: hot rolling, the copper ingot is hot rolled at 830℃, the final rolling temperature is 600℃, water quenching, and milling.

[0051] Fourth: Rolling + Annealing, rough rolling, deformation 60% → 500℃ / annealing for 9 hours.

[0052] Fifth: Finish rolling, rolling to 18μm thick foil at pass rates of 5%, 7%, 8.5% and 10% respectively, with a total processing rate of 95%.

[0053] Sixth: Two-stage annealing, 180℃ / 30min + 280℃ / 60min heat treatment, with a pass rate of 5%. The minimum grain size of the sample was 2.6μm, and the maximum grain size was 520μm. The average grain size was 50μm, as shown in Table 3.

[0054] Table 3

[0055]

[0056] Example 4

[0057] Using cathode copper as raw material, smelting was carried out under calcined charcoal covering. After melting, the temperature was held at 1200℃ for 20 min, Ag and Sn were added, the calcined charcoal was removed, and the temperature was held at atmospheric conditions for 30 min. The Ag, Sn, and O values ​​were adjusted to 0.015%, 0.005%, and 0.025%, while controlling the Fe, P, and S contents to be below 3 ppm. Semi-continuous casting was then performed.

[0058] Second: Semi-continuous casting, casting temperature 1180℃, casting speed 9m / h, to obtain oxygen-containing copper base material ingots that meet the required specifications.

[0059] Third: hot rolling, the copper ingot is hot rolled at 800℃, the final rolling temperature is above 600℃, water quenching, and milling.

[0060] Fourth: Rolling + Annealing, rough rolling deformation 60% → 500℃ / annealing for 9h.

[0061] Fifth: Finish rolling, rolling to 18μm thick foil at pass rates of 5%, 7%, 8.5% and 10% respectively, with a total processing rate of 95%.

[0062] Sixth: Two-stage annealing, 160℃ / 30min + 260℃ / 60min heat treatment, with a pass rate of 5%, resulted in a minimum grain size of 2.5μm and a maximum grain size of 520μm. The average grain size was 47μm, as shown in Table 4.

[0063] Table 4

[0064]

Claims

1. A method of producing a high flexure rolling copper foil having a high {100} texture content, characterized by: Pure tin and pure silver are added to molten copper to obtain a copper alloy melt. The copper alloy melt is cast to obtain an oxygen-containing copper base material ingot. The oxygen-containing copper base material ingot is hot-rolled and then water-quenched to obtain a hot-rolled billet. The hot-rolled billet is then subjected to rough rolling, annealing, and finish rolling, followed by double-stage annealing to obtain the final product. During the finishing rolling process, the deformation per pass is controlled at 5-10%, and the total deformation is 80-99%. The two-stage annealing process involves first heating to 160-200℃ and holding for 15-90 minutes, then heating to 260-320℃ and holding for 30-90 minutes.

2. The method for preparing a high-flexibility rolled copper foil with high {100} texture content according to claim 1, characterized in that: The high-flexibility rolled copper foil has the following composition by mass percentage: Ag 0.005-0.015%, Sn 0.002-0.005%, O 0.015-0.025%, with the balance being Cu and unavoidable impurities.

3. The method of claim 1, wherein the high {100} texture content high ductility rolled copper foil is prepared by the steps of: Using cathode copper as raw material, copper liquid is obtained by holding it at 1180-1220℃ for 20-40 minutes under the condition of calcined charcoal covering. Pure tin and pure silver are added to the copper liquid, and the calcined charcoal is removed. The copper alloy melt is obtained by holding it at atmospheric temperature for 10-40 minutes. ​ 4. The method of claim 1, wherein the high {100} texture content high ductility rolled copper foil is prepared by the steps of: The casting method is semi-continuous casting, and the temperature of the semi-continuous casting is 1180℃-1200℃, and the casting speed is 7-9m / h. ​ 5. The method of claim 1, wherein the high {100} texture content high ductility rolled copper foil is prepared by the steps of: The initial rolling temperature of the hot rolling is 800-850℃, and the final rolling temperature is 600℃ or above. ​ 6. The method for preparing a high-flexibility rolled copper foil with high {100} texture content according to claim 1, characterized in that: The total shaping weight of the rough rolling is 50-70%.

7. The method of claim 1, wherein the high {100} texture content high ductility rolled copper foil is prepared by the steps of: The annealing temperature is 500-550℃, and the annealing time is 8-10 hours. ​ 8. The method of claim 1, wherein the high {100} texture content high ductility rolled copper foil is prepared by the steps of: The deformation per pass in the finishing mill is 5-7%, and the total deformation is 93-96%. ​ 9. The method for preparing a high-flexibility rolled copper foil with high {100} texture content according to claim 1, characterized in that: The two-stage annealing process involves first heating to 180-200℃ and holding for 15-90 minutes, then heating to 280-300℃ and holding for 30-90 minutes.

10. A high-flexibility rolled copper foil with high {100} texture content prepared by the preparation method according to any one of claims 1-9, characterized in that: In the high-flexibility rolled copper foil, the {100} texture accounts for 50-95%.

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