Short-process preparation method of rolled copper foil base material
By employing a short-process preparation method and using precisely controlled melting and multiple annealing processes, the problems of long preparation process and unstable microstructure of rolled copper foil masterbatch have been solved, achieving high-quality production of rolled copper foil masterbatch that meets the performance requirements of flexible circuit boards.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-24
AI Technical Summary
The existing process for preparing rolled copper foil substrate is too long, resulting in a long production cycle and unstable internal structure of the substrate, which easily leads to defects such as pores and bubbles, and cannot meet the quality requirements of flexible circuit boards.
A short-process preparation method is adopted, including precise smelting of pure cathode copper, hot rolling, cold rolling and gas cushion furnace annealing, etc., to control oxygen content and impurities. Through hot rolling, cold rolling and multiple annealing treatments, the grains are refined and the mechanical properties and surface quality of the material are improved.
The processing flow is shortened, the internal structure uniformity and surface quality of the rolled copper foil substrate are improved, the strength, plasticity and conductivity of the material are enhanced, the probability of surface defects is reduced, and the requirements for flexible circuit boards are met.
Smart Images
Figure CN121715438A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of rolled copper foil processing technology, and relates to a short-process preparation method for rolled copper foil master material. Background Technology
[0002] With the rapid development of the electronic communications, artificial intelligence, and humanoid robot industries, the demand for flexible printed circuit boards (FPCs) is increasing day by day, which places higher and higher requirements on the quality and performance of the rolled copper foil used in FPCs.
[0003] Currently, the main methods for preparing rolled copper foil masterbatch include smelting, refining, casting, hot rolling, milling, cold rolling, annealing, cleaning, cold rolling, precision rolling, annealing, cleaning and passivation, etc. This process is too lengthy, resulting in a long production cycle. Furthermore, the preparation process for rolled copper foil masterbatch does not specify requirements for the oxygen content of the masterbatch ingot, making the internal structure of the masterbatch prone to instability. This leads to defects such as porosity and bubbles during the processing to form rolled copper foil, affecting product quality and failing to meet the requirements for FPC applications. Summary of the Invention
[0004] The purpose of this invention is to provide a short-process preparation method for rolled copper foil masterbatch, so as to solve the problem of a long preparation process for rolled copper foil masterbatch.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: This application provides a short-process method for preparing rolled copper foil masterbatch, the method comprising: Pure cathode copper is smelted and cast, then hot-rolled and milled at ≥800℃ to obtain a hot-rolled billet; The hot-rolled billet is subjected to cold rolling, first air cushion furnace annealing, fine rolling, second air cushion furnace annealing, surface treatment, and trimming to obtain rolled copper foil master material.
[0006] The present invention has the following beneficial effects: (1) This application uses purification technology to precisely control the oxygen content and impurities in the melting and casting process, and produces ingots with dense structure and qualified composition.
[0007] (2) After the ingot is hot rolled and milled to remove the surface oxide scale, the processing flow is shortened by cold deformation and large processing rate. The mechanical properties and grain size of the strip are controlled by the processing rate and annealing temperature in the air cushion furnace annealing. At the same time, with the reduction of hot rolling, cold rolling and finishing rolling passes, the grains in the ingot are continuously broken, elongated and recrystallized and refined, resulting in a better refinement effect. The microstructure of the prepared rolled copper foil base material is more uniform and dense, which is conducive to improving the mechanical properties of the material such as strength, plasticity and hardness. It also has a positive impact on the subsequent processing and forming properties of the foil (such as stamping, bending and flexural properties), and reduces the probability of surface defects such as scratches and abrasions.
[0008] (3) The treatment method of cold rolling, first air cushion furnace annealing, fine rolling and second air cushion furnace annealing can improve the residual stress distribution of the material, effectively control the processing pattern, shorten the process route of the processing, reduce the formation of surface quality defects, and improve the overall quality of rolled copper foil master material.
[0009] (4) The rolled copper foil substrate prepared in this application has the characteristics of good conductivity, uniform internal structure, good surface quality, high dimensional accuracy, bending resistance and fatigue resistance, which is beneficial to improving the flexural performance of copper foil and has good promotion and application value. Attached Figure Description
[0010] Figure 1 This is a cross-sectional microstructure analysis image of the ingot in Example 1 of this application; Figure 2 This is a slice microstructure analysis image of the hot-rolled billet in Example 1 of this application; Figure 3 This is a section image of the microstructure of the thin strip after the first annealing in Example 1 of this application; Figure 4 This is a section image of the microstructure of the thin strip after the second annealing. Figure 5 This is a distribution trend diagram of oxygen content in the ingot in Example 1 of this application. Detailed Implementation
[0011] This application provides a short-process method for preparing rolled copper foil masterbatch, the method comprising: S01: Pure cathode copper is smelted and cast, then hot-rolled and milled at ≥800℃ to obtain a hot-rolled billet.
[0012] Pure cathode copper with a copper content ≥99.999% was used as the raw material for preparing rolled copper foil. After removing the oxide scale and foreign matter from the pure cathode copper and drying it, the pure cathode copper was placed into a smelting furnace for melting. During the melting process, the slag covering layer in the furnace was skimmed off to expose the molten copper and allow for a certain period of aeration to increase the oxygen content of the molten copper. After skimming, charcoal was placed on the surface of the molten copper in the furnace. During the melting stage, the reaction between oxygen and hydrogen was used to control the hydrogen content in the molten copper solution. At the same time, metallic impurities in the molten copper were slagred and floated to the surface in the form of oxides, thus purifying the molten copper and ensuring that the oxygen content of the ingots formed after casting was ≥300ppm.
[0013] Keep the casting pipe submerged below the liquid level in the crystallizer. Place a high-temperature resistant filter element in the casting pipe, seal the crystallizer opening with a high-temperature resistant sealing cover, and add an oxygen absorption device. The molten copper is then cast at a casting temperature of 1130-1180℃ and a casting speed of 150mm / min to obtain an ingot with a smooth surface, no cracks, no cold shuts, no slag inclusions, a thickness of 280-300mm, and an oxygen content ≥300ppm.
[0014] The strip with a thickness of 15-18 mm is formed by rolling in a walking beam furnace at a heating temperature ≥800℃ for 9 passes. The hot rolling in this application involves three rolling stages: start, intermediate, and finish. These three stages are closely related. If the reduction in the start stage is small, it will inevitably increase the burden on the subsequent passes, leading to an increase in the number of passes in the later stages of hot rolling. If the finishing rolling temperature is too low, it will affect the performance and quality of the hot-rolled billet.
[0015] The specific rolling process is as follows: (1) Hot rolling start stage When ingot rolling begins, the primary requirement is to ensure smooth bite-in. Currently, the most commonly used bite angle for hot rolling is 20-25°. If bite-in is difficult during production, the rolling process can be facilitated by increasing the ingot's thrust or raising the workpiece's bite speed. To transform the non-uniform columnar and equiaxed crystal structure from the as-cast state into a more ductile processing structure, the pass rate and rolling speed in the initial hot rolling stage should not be too high.
[0016] (2) Intermediate stage of hot rolling During hot rolling, most of the deformation of the ingot occurs in the intermediate stage. At this time, the as-cast structure gradually transforms into a machined structure, the temperature of the rolled piece decreases, the plasticity is good but the deformation resistance is not high. At this time, the high-temperature plasticity of the rolled piece should be fully utilized by using a large reduction and increasing the rolling speed.
[0017] (3) Hot rolling final stage When hot rolling enters the last few passes, the rolled piece becomes thin and long. At this point, the rolling temperature decreases and the temperature difference between the beginning and end is large. To obtain a straight billet with small dimensional deviations, a smaller pass rate is generally used, and the roll properties are adjusted appropriately. For easily cracked low-plasticity alloys, in addition to using a small pass rate, rolling should be as fast as possible to ensure that the final rolling temperature is not too low.
[0018] After hot rolling, the oxide scale on the strip surface is removed by milling. In this application, the milling amount is 0.5-1.5 mm per side, the milling cutter speed is 8 m / min, and the milling fluid concentration is 0.2-0.5%. After milling, a hot-rolled billet with a smooth surface and no indentation is obtained. In this application, the milling fluid used is a commonly used milling fluid in the art.
[0019] S02: The hot-rolled billet is subjected to cold rolling, first air cushion furnace annealing, fine rolling, second air cushion furnace annealing, surface treatment, and trimming to obtain rolled copper foil master material.
[0020] The hot-rolled billet after milling is subjected to nine cold rolling passes to change the thickness of the strip through cold working deformation, resulting in a thin strip with a thickness of 0.8±0.01mm. To ensure edge quality, the cold-rolled thin strip is trimmed using a thin strip shear, with a trimming allowance of ±7.5mm on both sides.
[0021] After trimming, the thin strip is placed in a continuous air-cushion furnace under pure nitrogen protection for a first annealing treatment at 680℃ and a strip running speed of 80m / min. Then, it undergoes eight passes of finish rolling to reduce the strip thickness from 0.8±0.01mm to 0.05-0.1mm. The 0.05-0.1mm thick strip is then subjected to a second annealing treatment in a continuous air-cushion furnace at 450℃ and a strip running speed of 70m / min to homogenize the internal grain structure and control the surface roughness of the thin strip within the range of 0.15-0.35μm.
[0022] The thin strip after secondary annealing is surface passivated using a low-concentration passivation solution to prevent oxidation and discoloration, and the surface dyne value is ≥40. The low-concentration passivation solution used in this application is a commonly used passivation solution in the art, and the composition of the passivation solution is not specifically limited in this application.
[0023] After surface passivation, the thin strip is trimmed by using appropriate isolation rings and adjusting the gap between the male and female parts to obtain a rolled copper foil base material without burrs, curling edges, or protrusions.
[0024] The technical solution of the present invention will be further explained and described below through specific embodiments.
[0025] Example 1 This application provides a short-process method for preparing rolled copper foil masterbatch, the method comprising: S101: Pure cathode copper with a copper content ≥99.999% is removed from its oxide scale and foreign matter, dried, and then smelted in a melting furnace. The molten copper is then cast at a casting temperature of 1150℃ and a casting speed of 150mm / min to obtain an ingot with a smooth surface, no cracks, no cold shuts, no slag inclusions, a thickness of 280mm, and an oxygen content ≥300ppm. This ingot is then rolled in a walking beam furnace at a heating temperature of 1000℃ in 9 passes to form a strip with a thickness of 18mm. This strip is then milled under conditions of a single-sided milling margin of 1.0mm, a milling cutter speed of 8m / min, and a milling fluid concentration of 0.4% to obtain a hot-rolled billet with a smooth surface and no indentation.
[0026] S102: After 9 passes of cold rolling, a thin strip with a thickness of 0.8±0.01mm is formed. This thin strip is then trimmed on both sides with an edge trimming of ±7.5mm, and subjected to a first annealing treatment in a continuous gas furnace under pure nitrogen protection at a temperature of 680℃ and a strip running speed of 80m / min. The annealed thin strip undergoes 8 passes of finish rolling to reduce its thickness from 0.8±0.01mm to 0.08mm. The 0.08mm thick strip is then subjected to a second annealing treatment in a continuous gas furnace at 450℃ and a strip running speed of 70m / min, resulting in a thin strip with a surface roughness of 0.15μm. This thin strip is then passivated with a low-concentration passivation solution until the surface dyne value is ≥40, and after trimming, it yields the rolled copper foil base material.
[0027] Example 2 This application provides a short-process method for preparing rolled copper foil masterbatch, the method comprising: S201: Pure cathode copper with a copper content ≥99.999% is removed from its oxide scale and foreign matter, dried, and then smelted in a melting furnace. The molten copper is then cast at a casting temperature of 1130℃ and a casting speed of 150mm / min to obtain an ingot with a smooth surface, no cracks, no cold shuts, no slag inclusions, a thickness of 300mm, and an oxygen content ≥300ppm. This ingot is then rolled in a walking beam furnace at a heating temperature ≥800℃ for 9 passes to form a strip with a thickness of 15mm. This strip is then milled under conditions of a single-sided milling margin of 0.5mm, a milling cutter speed of 8m / min, and a milling fluid concentration of 0.2% to obtain a hot-rolled billet with a smooth surface and no indentation.
[0028] S202: After 9 passes of cold rolling, a thin strip with a thickness of 0.8±0.01mm is formed. This thin strip is then trimmed on both sides with an edge trimming of ±7.5mm, and subjected to a first annealing treatment in a continuous gas furnace under pure nitrogen protection at a temperature of 680℃ and a strip running speed of 80m / min. The annealed thin strip undergoes 8 passes of finish rolling to reduce its thickness from 0.8±0.01mm to 0.05mm. The 0.05mm thick strip is then subjected to a second annealing treatment in a continuous gas furnace at 450℃ and a strip running speed of 70m / min, resulting in a thin strip with a surface roughness of 0.2μm. This thin strip is then passivated with a low-concentration passivation solution until the surface dyne value is ≥40, and after trimming, it yields the rolled copper foil base material.
[0029] Example 3 This application provides a short-process method for preparing rolled copper foil masterbatch, the method comprising: S301: Pure cathode copper with a copper content ≥99.999% is removed from its oxide scale and foreign matter, dried, and then smelted in a melting furnace. The molten copper is then cast at a casting temperature of 1180℃ and a casting speed of 150mm / min to obtain an ingot with a smooth surface, no cracks, no cold shuts, no slag inclusions, a thickness of 290mm, and an oxygen content ≥300ppm. This ingot is then rolled in a walking beam furnace at a heating temperature ≥800℃ for 9 passes to form a strip with a thickness of 16mm. This strip is then milled under conditions of a single-sided milling margin of 1.5mm, a milling cutter speed of 8m / min, and a milling fluid concentration of 0.5% to obtain a hot-rolled billet with a smooth surface and no indentation.
[0030] S302: After 9 passes of cold rolling, a thin strip with a thickness of 0.8±0.01mm is formed. This thin strip is then trimmed on both sides with an edge trimming of ±7.5mm, and subjected to a first annealing treatment in a continuous gas furnace under pure nitrogen protection at a temperature of 680℃ and a strip running speed of 80m / min. The annealed thin strip undergoes 8 passes of finish rolling to reduce its thickness from 0.8±0.01mm to 0.1mm. The 0.1mm thick strip is then subjected to a second annealing treatment in a continuous gas furnace at 450℃ and a strip running speed of 70m / min, resulting in a thin strip with a surface roughness of 0.15μm. This thin strip is then passivated with a low-concentration passivation solution until the surface dyne value is ≥40, and after trimming, it yields the rolled copper foil base material.
[0031] In this application embodiment, the ingot, hot-rolled billet, thin strip after the first annealing, and thin strip after the second annealing in Example 1 were subjected to cross-sectional microstructure analysis, and the results were obtained. Figure 1-4 .
[0032] From the appendix Figure 1 As can be seen, the ingot microstructure exhibits a uniform columnar crystal + equiaxed crystal morphology, with a straight centerline, symmetrical and uniform triangular regions on both sides, no excessive coarsening, weak solute segregation between dendrites (good compositional uniformity), and no casting defects such as porosity or shrinkage cavities. After hot rolling deformation, some of the coarse grains in the original as-cast state were elongated along the rolling direction, forming a fibrous / banded deformed microstructure; at the same time, under the high temperature conditions of hot rolling, dynamic recrystallization occurred, generating some fine equiaxed crystals.
[0033] From the appendix Figure 2It is evident that the microstructure of the hot-rolled billet slices exhibits no obvious fibrous, severely deformed regions. The dynamically recrystallized equiaxed grains are small and uniformly distributed, with clear, continuous grain boundaries free of pores, inclusions, and other defects. Sufficient dynamic recrystallization eliminates most of the deformation distortion, and the fine, uniform grains provide a good microstructure foundation for subsequent cold rolling and annealing processes, improving the uniformity of the final product's performance. The hot-rolled microstructure, after cold rolling, forms a fibrous deformed structure. Through a single annealing process, the fibrous deformed structure stretched along the rolling direction after cold rolling is transformed into a uniform equiaxed grain structure through static recovery → static recrystallization → grain growth.
[0034] From the appendix Figure 3 It is evident that the microstructure of the thin strip after the first annealing exhibits a uniform equiaxed crystal morphology, with uniform and refined grain size, achieving a dual optimization of microstructure refinement and defect elimination.
[0035] From the appendix Figure 4 It is evident that the microstructure of the thin strip after the second annealing exhibits a uniform equiaxed crystal structure after complete recrystallization, with no residual deformed structure, no obvious grain boundary distortion, and no coarse abnormally large grains. It is a typical fine-grained uniform structure, which can significantly improve the strength and plasticity matching of the material.
[0036] As can be seen from the above, the new processing technology for high-oxygen copper foil base material, through the rational matching of casting, hot rolling, cold working, and heat treatment processes, achieves the desired internal microstructure. The mechanical properties of rolled copper foil are closely related to the processing rate and annealing temperature, while the grain size before processing also influences mechanical properties to a certain extent. To ensure the final performance of the copper foil, the mechanical properties and grain size of the copper foil base material are strictly controlled, guaranteeing the high flexibility and bending resistance of the rolled copper foil.
[0037] In addition, this application embodiment also uses the short-process preparation method in Example 1, as shown in Tables 1-3, to prepare 10 batches of rolled copper foil masterbatch with the parameters of 9-pass hot rolling, 9-pass cold rolling, and 8-pass finishing rolling, and records the ingot oxygen content of each batch of samples, resulting in Table 4. Figure 5 Meanwhile, the tensile strength, elongation and other properties of 10 batches of rolled copper foil base materials were tested, and the results are shown in Table 5.
[0038] Table 1: Process parameters for 9-pass hot rolling Table 2: Process parameters for 9-pass cold rolling Table 3: Process parameters for 8-pass finishing rolling Table 4: Oxygen content of ingots during the preparation of 10 batches of rolled copper foil base material From Table 4 and Appendix Figure 5 It is evident that the oxygen content of the ingots in the preparation process of all 10 batches of rolled copper foil masterbatch was greater than 300 ppm, with some batches even reaching 416 ppm. This indicates that the embodiments of this application, through the reaction between oxygen and hydrogen during the smelting stage, control the hydrogen in the furnace solution, seal the crystallizer opening with a high-temperature resistant material, and add an oxygen absorption device, can achieve the purpose of purifying the copper liquid, ensuring that the oxygen content of the ingots can be stably controlled above 300 ppm. Consequently, the rolled copper foil produced is less prone to porosity and bubbles, meeting the requirements of FPC for rolled copper foil.
[0039] Table 5: Performance parameters of 10 batches of rolled copper foil base material As shown in Table 5, the 10 batches of copper foil master materials prepared using the short-process preparation method in Example 1 of this application have a hardness Hv0.1≤60°, elongation≥40%, and conductivity>100%, all of which meet the performance requirements of copper foil master materials.
[0040] In addition, this application also cuts 50mm diameter pieces from 10 batches of copper foil masterbatch. For a 150mm shaped specimen, after adjusting and locking the support roller spacing, place the specimen between the support rollers. The lower edge of the specimen in contact with the indenter should be free of burrs. Perform a 180° bending test to determine the minimum bending radius r. min Table 6 shows the number of bends at the maximum bending angle of less than 180°.
[0041] Table 6: Bending Test Results As shown in Table 6, all 10 batches of copper foil preforms underwent more than 8 bends, and no cracks or significant dents were found. This indicates that the copper foil preforms prepared by the short-process preparation method provided in this application have good bending performance and fatigue strength, laying the foundation for improving the flexural properties of copper foil.
[0042] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A short-process preparation method for rolled copper foil masterbatch, characterized in that, include: Pure cathode copper is smelted and cast, then hot-rolled and milled at ≥800℃ to obtain a hot-rolled billet; The hot-rolled billet is subjected to cold rolling, first air cushion furnace annealing, fine rolling, second air cushion furnace annealing, surface treatment, and trimming to obtain rolled copper foil master material.
2. The short-process preparation method of rolled copper foil masterbatch according to claim 1, characterized in that, The casting temperature is 1130-1180℃, the casting speed is 150mm / min, the oxygen content of the ingot is ≥300ppm, and the thickness of the ingot is 280-300mm.
3. The short-process preparation method of rolled copper foil masterbatch according to claim 1, characterized in that, The hot rolling process consists of 9 passes, and the thickness of the hot-rolled strip is 15-18 mm; the milling amount is 0.5-1.5 mm per side.
4. The short-process preparation method of rolled copper foil masterbatch according to claim 1, characterized in that, The cold rolling process consists of 9 passes, and the thickness of the strip after cold rolling is 0.8±0.01mm.
5. The short-process preparation method of rolled copper foil masterbatch according to claim 1, characterized in that, The first air cushion furnace annealing temperature is 680℃ and the strip running speed is 80m / min; the second air cushion furnace annealing temperature is 450℃ and the strip running speed is 70m / min.
6. The short-process preparation method of rolled copper foil masterbatch according to claim 1, characterized in that, The surface treatment involves passivation with a passivation solution until the surface dyne value is ≥40.
7. The short-process preparation method of rolled copper foil masterbatch according to claim 1, characterized in that, The surface roughness of the rolled copper foil substrate is 0.15-0.35 μm.