Copper foil preparation system with double electrolytic cells, electrolytic copper foil and preparation method

Abstract

The present invention discloses a copper foil preparation system with dual electrolytic cells, comprising a first electrolytic cell and a second electrolytic cell; the first electrolytic cell comprises a first fixed anode plate and a rotating cathode roller, which are separately arranged; the second electrolytic cell comprises a second fixed anode plate and an electroplating roller, which are separately arranged; a roll-to-roll transmission structure is adopted between the first electrolytic cell and the second electrolytic cell; the system also comprises a PLC control system and a real-time sensor, which are electrically connected to the first electrolytic cell and the second electrolytic cell, respectively. The present invention also discloses a method for preparing electrolytic copper foil using the above-mentioned copper foil preparation system and the copper foil prepared. The copper foil preparation system with dual electrolytic cells provided by the present invention adopts a dual electrolytic cell structure to clearly distinguish the plating layer into a base layer and a surface layer, thereby solving the problem that the traditional single electrolytic cell method is difficult to achieve independent control of the layered physical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic copper foil, relates to a copper foil preparation system with double electrolytic cells, also relates to a method for preparing electrolytic copper foil using the copper foil preparation system, and also relates to the electrolytic copper foil prepared using the preparation method. Background Art

[0002] Electrolytic copper foil is a metal film made by depositing metal ions on the surface of the cathode body through an electrochemical reaction in an electrolyte containing metal ions. As a core material, it is widely used in high-functionality electronic components such as flexible printed circuit boards (FPCBs), lithium-ion battery current collectors, high-frequency circuit boards, semiconductor packaging, electromagnetic shielding materials and other fields. The manufacture of electrolytic copper foil is usually based on a system consisting of a rotating cathode roller, an electrolytic cell containing electrolyte and an anode plate. When the lower part of the cathode roller is immersed in the electrolyte at a certain depth and rotates, an electric current is applied between the anode plate and the cathode roller, and the copper ions (Cu 2+ ) will undergo reduction deposition on the cathode roller surface, forming a copper foil film. When the plated copper layer reaches a certain thickness, it is peeled off and continuously recovered. By adjusting parameters such as current density, electrolyte composition, temperature, and additive concentration and type, the copper foil's physical properties, including thickness, surface roughness, grain structure, hardness, and mechanical strength, can be controlled. Because the electrolytic copper foil manufacturing industry has long focused on simplified equipment and high-speed / high-volume production, traditional electrolytic copper foil manufacturing technology has traditionally relied on a single process to form the entire coating layer in a single step, often using a single electrolytic cell, single electrolyte, and single current conditions. For applications requiring less precise properties, such as lithium-ion battery current collectors or general-purpose FPCB copper foil, this approach is sufficient to meet quality requirements. Furthermore, in an industry where production efficiency is paramount, attempts to functionalize and layer the coating are relatively inactive. The industry generally believes that complex processes will negatively impact equipment maintenance, operational stability, and additive management. Therefore, in traditional technologies, structural designs that employ differentiated electroplating conditions for the base and surface layers have not actually been attempted or introduced into industrial production. However, with the rapid development of high-value-added applications such as high-frequency circuit boards, AI / 6G communication components, and high-density semiconductor packaging, market requirements for the quality of electrolytic copper foil are evolving towards precision and composite materials, while also increasing the demand for greater freedom in controlling physical properties. Against this backdrop, the limitations of traditional technologies are becoming increasingly prominent in the following areas.

[0003] First, the coating of electrolytic copper foil needs to be divided into a base layer and a surface layer for design according to different functions. The base layer is mainly responsible for ensuring the overall thickness, mechanical stability and electrical conductivity of the copper foil, and is usually suitable for rapid deposition under high current density and high copper ion concentration conditions. Although this condition can effectively improve production efficiency and ensure the thickness of the base layer, it is limited in achieving precise surface quality because high-speed deposition can easily lead to grain coarsening or increased surface roughness. On the other hand, the surface layer, as the outer functional area of ​​the electroplating layer, requires precise control of key parameters such as circuit signal transmission characteristics, adhesion, surface roughness, hardness and crystal orientation. To achieve these characteristics, a low current density electroplating process is usually required to optimize performance by adjusting the deposition rate and ensuring the stabilization of the additives. However, in the traditional single electrolytic cell process, due to the inability to apply these conflicting conditions in layers, the performance of at least one of the base layer and the surface layer will inevitably be impaired, ultimately forming a technical limitation that cannot simultaneously achieve optimal quality on a double-layer structure. Second, when functional additives act on the entire electrolyte, additives that should only affect the surface layer will penetrate into the base layer, potentially leading to quality defects such as reduced grain uniformity, interlayer stress imbalance, curling, and microcracks. Third, there are technical difficulties in precisely controlling the interlayer structure. Although methods have been tried to adjust the current conditions or additive composition over time in a single electrolytic cell, due to factors such as delayed electrolyte reactions, the formation of ion concentration gradients, and the influence of residual additives, this method is difficult to ensure the uniformity of interface quality and may lead to reduced process stability during repeated production. Fourth, processes that rely on functional additives are difficult to maintain stability during long-term operation. Changes in the electrolyte reaction characteristics caused by the decomposition, accumulation, and interaction of additives can cause differences in the quality of the initial and later coatings, leading to problems such as reduced yield and quality consistency. Fifth, with the increasing demand for high-performance products, the functional requirements of copper foil are becoming increasingly diversified, but a single electrolytic cell structure makes it difficult to achieve the process flexibility and condition independence required for customized process design. In particular, for a diverse product line including highly flexible soft copper foil, high-hardness copper foil for communication substrates, and low-loss conductors, a process structure with the ability to independently control each layer is urgently needed, which is exactly what existing technologies cannot meet. Summary of the Invention

[0004] The first object of the present invention is to provide a copper foil preparation system with a dual electrolytic cell. The dual electrolytic cell structure is used to clearly divide the coating into a base layer and a surface layer, so that each layer can apply the most optimized electrolytic conditions, thereby solving the problem that the traditional single electrolytic cell method is difficult to achieve independent control of the layered physical properties.

[0005] A second object of the present invention is to provide a method for preparing electrolytic copper foil using the above copper foil preparation system.

[0006] The third object of the present invention is to provide an electrolytic copper foil prepared by the above preparation method.

[0007] The first technical solution adopted by the present invention is a copper foil preparation system with dual electrolytic cells, including a first electrolytic cell and a second electrolytic cell, each of which includes a dissolution tank, a dirty liquid tank, a clean liquid tank, an electrolyte supply system, a temperature control system, a current supply system, and an additive injection system;

[0008] The first electrolytic cell includes a first fixed anode plate and a rotating cathode roller, and the first fixed anode plate and the rotating cathode roller are separately arranged; the second electrolytic cell includes a second fixed anode plate and an electroplating roller, and the second fixed anode plate and the electroplating roller are separately arranged;

[0009] A roll-to-roll transmission structure is used between the first electrolytic cell and the second electrolytic cell, and a cleaning roller and a hot air dryer are provided between the first electrolytic cell and the second electrolytic cell;

[0010] It also includes a PLC control system and a real-time sensor, which are electrically connected to the first electrolytic cell and the second electrolytic cell respectively.

[0011] The present invention is also characterized in that:

[0012] The diameter of the rotating cathode roller in the first electrolytic cell is 2500~3000mm, and the diameter of the electroplating roller in the second electrolytic cell is 1500~1700mm.

[0013] The second technical solution adopted by the present invention is a method for preparing electrolytic copper foil based on a dual electrolytic cell, using the above-mentioned copper foil preparation system with a dual electrolytic cell, specifically as follows:

[0014] Step 1: adding a first electrolyte to a first electrolytic tank and adding a second electrolyte to a second electrolytic tank;

[0015] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell to form a base layer on the surface of the rotating cathode roller; then, the base layer is moved to the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller to form a surface layer, thereby obtaining a double-layer electrolytic copper foil;

[0016] Step 3. The double-layer electroplated copper foil is further transferred to a Cr anti-rust solution for anti-rust treatment through a roll-to-roll process. The treated copper foil is then rolled and heat-treated at 65°C for 24 hours to obtain an electrolytic copper foil based on a double electrolytic cell.

[0017] The present invention is also characterized in that:

[0018] The first electrolyte includes copper ions, sulfate ions, and a first additive, wherein the copper ion concentration in the first electrolyte is 80-90 g / L and the sulfate ion concentration is 100-110 g / L;

[0019] The second electrolyte comprises copper ions, sulfate ions, and a second additive, wherein the copper ion concentration in the second electrolyte is 40-45 g / L and the sulfate ion concentration is 75-80 g / L;

[0020] The temperature of the first electrolyte is 50-55°C, and the pH value of the first electrolyte is below 1.0;

[0021] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0022] The first additive includes a stress reliever, a conductive additive and a grain growth regulator;

[0023] The stress reliever is N, N-dimethylthiourea, with a concentration of 0.05~0.5g / L;

[0024] The conductive additive is sodium chloride with a concentration of 10.0~20.0g / L;

[0025] The grain growth regulator is 2-butyne-1,4-diol with a concentration of 0.01~0.2g / L.

[0026] The second additive includes a leveling agent, a corrosion inhibitor, a brightener and a surfactant;

[0027] The leveling agent is sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, with a concentration of 0.1~1.0g / L;

[0028] The corrosion inhibitor is polyethylene glycol with a concentration of 0.5~3.0g / L;

[0029] The brightener is 3-mercapto-1-propanesulfonic acid, with a concentration of 0.01~0.05g / L;

[0030] The surfactant is sodium lauryl sulfate with a concentration of 0.01~0.1g / L.

[0031] The current density of the first current in step 2 is 30~50A / dm 2 ; The current density of the second current is 17.6A / dm 2 .

[0032] In step 3, the Cr rust preventive solution includes chromium ions and glucose, the chromium ion concentration is 0.45-0.60 mg / L, the glucose concentration is 7.0 g / L, the rust preventive solution temperature is 18-22° C., and the pH is below 3.5.

[0033] The third technical solution adopted by the present invention is an electrolytic copper foil prepared by a preparation method of electrolytic copper foil based on a double electrolytic cell. The electrolytic copper foil includes a base layer and a surface layer. The surface layer is plated on the outside of the base layer. The thickness of the electrolytic copper foil is 3.5~6μm, the thickness of the base layer is 3~5μm, and the thickness of the surface layer is less than or equal to 1μm.

[0034] The beneficial effects of the present invention are:

[0035] (1) The present invention has a copper foil preparation system with dual electrolytic cells. A rotating cathode roller with a larger diameter is arranged in the first electrolytic cell, and a plating roller with a smaller diameter is arranged in the second electrolytic cell. Through this structural design, even under the same conveying speed conditions, the retention time and current conditions of each layer can be optimized, thereby obtaining significant structural flexibility. The base layer and the surface layer are formed in independent electrolytic cells by electrolytic plating, thereby achieving independent control of the physical properties of each layer and precise plating quality. The core function of the base layer is to ensure the thickness and mechanical support of the copper foil, while the surface layer focuses on reducing roughness and improving adhesion. This functional division realizes precise control of high-performance plating.

[0036] (2) The copper foil preparation system of the present invention has a dual electrolytic cell. By minimizing the air exposure interval between the first electrolytic cell and the second electrolytic cell and configuring a cleaning roller and a hot air dryer, it can prevent interface contamination and maintain high reproducibility in repeated processes.

[0037] (3) The copper foil preparation method with dual electrolytic cells of the present invention completely isolates the electrolyte components used in each electrolytic cell from the additives, thereby fundamentally avoiding problems such as reaction imbalance, excessive accumulation or decomposition that may be caused by the interaction of additives. Therefore, by adding stress relievers, conductive additives and grain growth regulators in the base layer, thickness uniformity and structural stability are ensured; while in the surface layer, leveling agents, corrosion inhibitors, brighteners and surfactants are used to achieve roughness control and improve adhesion performance;

[0038] (4) The present invention has a method for preparing copper foil with a double electrolytic cell. After plating, a heat treatment process is performed at 65°C for 24 hours, which can effectively relieve the internal stress of the plating layer and achieve interlayer stress balance, thereby simultaneously suppressing curling deformation and improving the interface bonding strength. The electrolytic copper foil prepared by the method of the present invention can obtain excellent physical properties such as a thickness of 3.5~6μm, an S-side surface roughness (Ra) of 0.08~0.12, an M-side surface roughness (Rz) of 0.55~0.65, a room temperature tensile strength of 380~420MPa after heat treatment, an elongation of 5.0~7.0% at room temperature after heat treatment, and a curling degree of less than 5mm. In addition, this technology can realize an integrated metal layer structure without an additional bonding process, and effectively relieves internal stress and suppresses curling deformation by heat treatment after plating, thereby stabilizing material properties. This can minimize quality deviations in subsequent processing steps such as lamination, cutting, and lamination, thereby improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the structure of the copper foil preparation system with double electrolytic cells of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] The present application has a copper foil preparation system with dual electrolytic cells, such as Figure 1 As shown, it includes a first electrolytic cell and a second electrolytic cell, and the first electrolytic cell and the second electrolytic cell each include a dissolving tank, a dirty liquid tank, a clean liquid tank, an electrolyte supply system, a temperature control system, a current supply system and an additive injection system;

[0042] The first electrolytic cell includes a first fixed anode plate and a rotating cathode roller, and the first fixed anode plate and the rotating cathode roller are separately arranged; the second electrolytic cell includes a second fixed anode plate and an electroplating roller, and the second fixed anode plate and the electroplating roller are separately arranged;

[0043] The diameter of the rotating cathode roller in the first electrolytic cell ranges from 2500 to 3000 mm. A large-diameter rotating cathode roller is used to ensure stable formation of the base layer thickness. The diameter of the plating roller in the second electrolytic cell ranges from 1500 to 1700 mm. The use of a smaller-diameter plating roller enables precise formation of thin coatings in a shorter residence time at the same conveyor speed. This differentiated structural design significantly improves the accuracy of layered coating control and effectively achieves an optimal deposition environment that matches the physical properties of each layer with process requirements.

[0044] A roll-to-roll transmission structure is used between the first electrolytic cell and the second electrolytic cell, and a cleaning roller and a hot air dryer are provided between the first electrolytic cell and the second electrolytic cell;

[0045] It also includes a PLC control system and a real-time sensor, which are electrically connected to the first electrolytic cell and the second electrolytic cell respectively.

[0046] The above structural design is based on the following process requirements: the electrolysis conditions and additive compositions required for the base layer and surface layer must be strictly separated, and mutual interference must be completely eliminated. Since the separation of electrolyte components starting from the pretreatment stage has a decisive impact on the overall coating quality, the use of a completely independent system configuration is crucial. The structural design of this invention aims to reflect the differentiated configuration of electrolysis conditions in each layer through the system architecture.

[0047] A transmission structure that minimizes air exposure is adopted between the first electrolytic cell and the second electrolytic cell, and devices such as cleaning rollers and hot air dryers are configured to effectively prevent the electrolytes of different electrolytic cells from mixing with each other and contaminating the surface of the copper foil. This structure plays a key role in ensuring the interface stability and consistency of the additive reaction during the formation of the surface layer, and can maintain high reproducibility in repeated processes. In addition, the electroplating conditions of each electrolytic cell are integratedly managed and controlled by a PLC control system and a real-time sensor monitoring device, thereby ensuring that the uniformity of the electroplating quality and process stability can be guaranteed even in a long-term continuous production environment. Ultimately, the dual electrolytic system of the present invention not only provides a structure that can independently achieve the required properties of the base layer and the surface layer, but also combines the layers electrochemically uniformly, combining quality reliability and design flexibility that are difficult to achieve with the traditional single electrolytic cell method, and is a core process technology. In particular, in the fields of high-value-added electronic materials such as high-frequency communications, semiconductor packaging, and precision circuit boards, it can accurately realize the industrial application of high-performance electrolytic copper foil and has significant market competitiveness.

[0048] The present invention is based on a method for preparing electrolytic copper foil using a dual electrolytic cell, using the copper foil preparation system having the dual electrolytic cell, as follows:

[0049] Step 1: adding a first electrolyte to a first electrolytic tank and adding a second electrolyte to a second electrolytic tank;

[0050] Among them, the first electrolyte includes copper ions, sulfate ions and a first additive. The copper ion concentration in the first electrolyte is 80~90g / L, the sulfate ion concentration is 100~110g / L, the first electrolyte temperature is 50~55℃, and the pH value of the first electrolyte is below 1.0.

[0051] The first electrolytic cell, the process for forming the base layer, is crucial for ensuring the thickness and structural stability required for the electrolytic copper foil's mechanical support and conductivity. Therefore, a combination of additives is required to promote the dense and stable growth of the base layer. Specifically, the first additives include stress relievers, conductive additives, and grain growth regulators.

[0052] Specifically, the stress reliever is N,N-dimethylthiourea (N,N-Dimethylthiourea), with a concentration of 0.05-0.5g / L. Under high-speed electrodeposition conditions, the stress reliever effectively prevents uneven grain growth or excessive stress accumulation, while ensuring surface smoothness and grain density in the deposited layer. When the stress reliever concentration is below 0.05g / L, the ability to regulate grain growth is weakened, potentially leading to increased surface roughness and microcracks. When the stress reliever concentration exceeds 0.5g / L, it over-inhibits the metal ion reduction reaction, causing a decrease in plating rate and current efficiency.

[0053] The conductive additive is sodium chloride (Sodium Chloride), with a concentration of 10.0-20.0g / L. Its function is to increase the overall conductivity of the ions in the electrolyte, thereby ensuring uniform current distribution. The conductive additive can effectively prevent local overplating and improve the uniformity of the overall plating thickness. If the sodium chloride concentration is lower than 10.0g / L, the current may be concentrated in certain areas, exacerbating plating deviations. If the sodium chloride concentration exceeds 20.0g / L, the interaction between ions in the electrolyte may cause the viscosity to increase, causing plating marks or blockages.

[0054] The grain growth regulator is 2-butyne-1,4-diol (2-Butyne-1,4-diol), with a concentration of 0.01-0.2 g / L. During the electrolytic plating process, the grain growth regulator precisely controls the boundaries of the precipitated metal crystal particles and inhibits the adhesion of bubbles to the cathode surface, thereby preventing the formation of fine pinholes. This is especially true under high current density conditions, which can lead to abnormal growth of crystal grains or surface porosity. It also contributes to the densification of metal crystals within the base layer and improved durability of the coating. If the grain growth regulator concentration is less than 0.01 g / L, insufficient bubble removal will lead to increased porosity within the coating and exacerbate local deviations in the electroplating thickness. Conversely, if the grain growth regulator concentration exceeds 0.2 g / L, the gas removal reaction at the cathode interface is overly suppressed, potentially causing surface problems due to hydrogen generation, and stress concentration within the coating metal structure.

[0055] The second electrolyte includes copper ions, sulfate ions and a second additive. The copper ion concentration in the second electrolyte is 40~45g / L, the sulfate ion concentration is 75~80g / L, the second electrolyte temperature is 45°C, and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0056] The second electrolytic cell is the process for forming the surface layer. This requires precise control of the roughness, crystal size, directionality, and adhesion of the final surface layer formed on the base layer. Therefore, reaction uniformity under low current density conditions and the sustainability of the additive reaction are key. Secondary additives include leveling agents, corrosion inhibitors, brighteners, surfactants, and other additives used to enhance surface properties.

[0057] The leveler is sodium 3-(5-mercapto-1-tetrazolyl)benzene sulfonate (MBT-S), with a concentration of 0.1-1.0 g / L. MBT-S controls the crystal growth process on the surface of the coating, inhibiting the formation of localized surface protrusions or sharp crystals, thereby maintaining the uniformity of the electroplated layer's microstructure. MBT-S, in particular, induces a uniform current distribution, effectively reducing surface roughness (Rz). Concentrations exceeding 1.0 g / L can reduce plating speeds due to excessive suppression of surface reactions, and may also cause microcrystal aggregation in the coating.

[0058] The corrosion inhibitor is polyethylene glycol (PEG), with a concentration of 0.5-3.0 g / L. PEG's effect on the coating varies depending on its molecular weight, but it generally slows down the electroplating speed and maintains uniform precipitation of metal ions, thereby reducing coating thickness deviations. PEG regulates the reaction rate on the cathode surface, achieving dense grain formation while also relieving internal stress and preventing microcracks. If the PEG concentration is lower than 0.5 g / L, the precipitation regulation effect is weak, potentially leading to uneven coating. When the PEG concentration exceeds 3.0 g / L, the electroplating speed is excessively reduced, leading to decreased production efficiency and an increased risk of hydrogen retention or internal pores in the coating.

[0059] The brightener is 3-mercapto-1-propanesulfonic acid (MPS), with a concentration of 0.01-0.05 g / L. MPS is a sulfur-containing organic compound that effectively fine-tunes grain size, resulting in a smooth, bright surface. While similar in function to SPS, its reaction rate is slower, enabling stable brightening and a uniform metallic structure even at low current densities. This imparts uniform reflectivity and high-frequency signal transmission efficiency to the surface layer, while also minimizing physical property variations within the coating. If the 3-mercapto-1-propanesulfonic acid concentration is below 0.01 g / L, the grain-refining effect is significantly reduced. If the 3-mercapto-1-propanesulfonic acid concentration exceeds 0.05 g / L, excessive reaction inhibition may lead to a reduced deposition rate and uneven gloss.

[0060] The surfactant is sodium dodecyl sulfate (SDS), with a concentration of 0.01-0.1 g / L. This surfactant quickly removes bubbles generated during the electroplating process and improves the wettability of the cathode surface, thereby preventing coating defects. The surface layer is particularly thinner than the base layer and requires meticulous crystallization control. If microbubbles remain on the surface, defects such as pinholes and black spots can easily occur. This surfactant can eliminate these problems at the root and help the metal ions in the electrolyte evenly cover the entire cathode surface. If the SDS concentration is lower than 0.01 g / L, the interfacial tension reduction effect is insufficient. If the SDS concentration exceeds 0.1 g / L, excessive foaming and electrolyte turbidity may adversely affect subsequent cleaning processes.

[0061] All of the above additives must be dissolved in ultrapure water and stirred before being added. Their composition and concentration conditions are strictly set to ensure that they remain stable in the electrolyte.

[0062] The preparation process of the first and second electrolytes in the present invention is as follows: pure copper wire with a purity of at least 99.9% and sulfuric acid are added to the solution tank of the first electrolytic cell, where they are stirred and dissolved to prepare the first electrolyte. This electrolyte is then circulated through the wastewater tank of the first electrolytic cell to maintain stable copper and sulfate ion concentrations. Similarly, after the copper wire and sulfuric acid are dissolved in the dissolution tank of the second electrolytic cell, the second electrolyte is circulated through the wastewater tank of the second electrolytic cell to maintain the optimal composition of the cell. During the circulation process, each electrolyte passes through a separate heat exchanger to prevent crystallization caused by heat loss. The refined electrolytes are then filtered through diatomaceous earth to remove impurities and then transferred to their respective clean solution tanks. By arranging the dissolution tank, wastewater tank, and clean solution tank independently in each electrolytic cell, the electrolysis conditions (e.g., copper and sulfate ion concentrations, temperature, flow rate, and other parameters) for the base layer and surface layer can be precisely controlled without interfering with each other. To ensure stable production of electrolytic copper foil and achieve the desired physical properties for each layer, functional additives are placed in separate additive tanks along with ultrapure water. After dissolution and stirring, the electrolytes are then poured into two separate clean liquid tanks. Each electrolyte solution, containing additives, is then finely filtered through a fine filter before being supplied to the first and second electrolytic tanks, respectively.

[0063] This additive separation scheme fundamentally eliminates the problems caused by the common interactions of additives in single electrolytic cell processes - including reaction imbalance, decreased electroplating efficiency, excessive accumulation or decomposition, etc., thereby achieving precise control of each coating layer and significantly improving quality stability. In addition, since the electroplating reaction of each electrolytic cell is electrochemically continuous, the bonding between the base layer and the surface layer does not require an additional bonding process, and natural fusion can be achieved only through the precipitation reaction triggered by electron migration. In summary, according to the electrolytic copper foil layered structure of the present invention, even if the coating consists of a double layer, it is not a physically heterogeneous laminated structure, but a combination formed like a metal crystal. Therefore, there are almost no boundary defects such as interface peeling, stress concentration or cracks. In fact, in a dual electrolytic cell system, there is no need for additional heat treatment or pressing process after electroplating, and its interface strength and physical property uniformity can achieve performance comparable to or even better than that of a single-layer electroplating process.

[0064] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell, with the first current density being 30-50 A / dm 2 , forming a base layer on the surface of the rotating cathode roller; then the base layer is moved to the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller to form a surface layer. The second current density is 17.6A / dm 2 , and finally a double-layer electroplated electrolytic copper foil is obtained;

[0065] Step 3. The double-layer electroplated copper foil is further transferred to a Cr anti-rust solution for anti-rust treatment through a roll-to-roll process. The treated copper foil is then rolled and heat-treated at 65°C for 24 hours to obtain an electrolytic copper foil based on a double electrolytic cell.

[0066] Among them, the Cr rust preventive liquid includes chromium ions and glucose, the chromium ion concentration is 0.45~0.60 mg / L, the glucose concentration is 7.0 g / L, the rust preventive liquid temperature is 18~22℃, and the pH is below 3.5.

[0067] The preparation method of the Cr anti-rust liquid is as follows: chromium trioxide and glucose are added to ultrapure water respectively, and then filtered through a fine filter and injected into the anti-rust tank in the electrolytic cell.

[0068] To prevent oxidation on the surface of the electrolytic copper foil, chromium trioxide is dissolved in ultrapure water and stirred. After filtering through a fine filter, it is transferred to a Cr anti-rust tank for rust prevention. However, due to its high toxicity and environmental hazards, glucose is also added as a reducing agent. This anti-rust solution is immediately applied to the copper foil surface in the second electrolytic tank to effectively prevent oxidation and ensure surface stability.

[0069] The dual electrolytic system of the present invention fundamentally solves the structural and physical limitations of the traditional single electrolytic cell preparation method and has composite technical advantages. In particular, by distinguishing the base layer and the surface layer on a per-electrolytic cell basis, it is possible to apply optimized electroplating conditions according to their respective physical property targets, thus having significant advantages in ensuring the functionality and quality consistency of the entire coating. Specifically, in the first electrolytic cell, by setting up a high current density environment, the base layer of the electrolytic copper foil can be rapidly grown. This process not only provides sufficient thickness and a solid structural foundation for the inner layer responsible for the overall mechanical support and conductivity of the copper foil, but also ensures that the grain density and flatness are maintained above the standard level even under high-speed electroplating conditions. On the other hand, the second electrolytic cell is set to a low current density environment, allowing the functional additives to fully exert their effect. Under these conditions, precise physical property control such as grain refinement, reduced surface roughness, improved adhesion to semiconductor packaging substrates and high-frequency communication circuit boards, and grain orientation regulation can be achieved. In particular, the surface layer, a key area in direct contact with external circuits or the substrate, requires high functionality, including resistance to electromagnetic wave loss, oxidation stability, surface flatness, and signal transmission efficiency. Therefore, precise electroplating conditions are essential. This structural separation design, which forms the base layer under high current conditions and then sequentially forms the surface layer under low current conditions, effectively achieves differentiated control of physical properties.

[0070] In the present invention, the reason for setting the second electrolyte temperature and current density as fixed conditions is that the surface layer, as a functional area in direct contact with the external circuit in the entire electroplating layer, needs to have high-precision characteristics such as reduced high-frequency loss, improved surface flatness, and guaranteed bonding reliability. In particular, the surface layer is the most difficult to control in a single electrolytic cell method. It is extremely sensitive to current density changes or temperature deviations, which can easily lead to quality problems such as uneven grains, increased roughness, pinholes, and interface defects. Therefore, the surface layer electroplating conditions must adopt stable current density and temperature parameters to ensure that high reproducibility and consistency can be maintained in repeated processes. In addition, since the same linear speed must be maintained continuously through the two electrolytic cells in a roll-to-roll manner in the dual electrolytic system, the structure of each electrolytic cell has also been specially designed for its electroplating purpose. Specifically, the first electrolytic cell is dedicated to base layer forming, and its design focuses on ensuring thickness and mechanical support through long-term electrodeposition under high current density. For this reason, a large-diameter rotating cathode roller is used to fully extend the residence time of the copper foil in the electrolyte, thereby achieving uniform forming of the thick base layer. The second electrolytic cell is dedicated to forming the surface layer, requiring thin, precise electroplating. The sensitivity of the additives and their ability to control grain size must be carefully considered. Therefore, a small-diameter electroplating roller is used. Even with a short dwell time, this significantly improves roughness, enhances gloss, and optimizes adhesion at a current density of 17.6 A / dm². This residence time separation design, based on the difference in diameter between the cathode and plating rollers, enables optimized control of the properties of each layer, based on the electrodeposition time and control environment of each electrolytic cell, at the same line speed. This ensures independent control of the layered properties and high-precision electroplating quality. Furthermore, this differentiated electrolytic condition setting enables precise realization of the required physical properties for each layer, such as ensuring mechanical support and conductivity in the base layer, improving roughness and enhancing adhesion in the surface layer. This plays a key role in controlling stress distribution and grain microstructure within the coating. In this dual-electrolytic cell structure, the additives used for each coating layer are differentiated and dosed independently according to their functional purpose.

[0071] The electrolytic copper foil produced by the present invention, based on a method for preparing electrolytic copper foil using a dual electrolytic cell, comprises a base layer and a surface layer, with the surface layer plated on the outside of the base layer. The thickness of the electrolytic copper foil ranges from 3.5 to 6 μm, the base layer from 3 to 5 μm, and the surface layer less than or equal to 1 μm. The electrolytic copper foil structure of the present invention can form an integrated metal layer without interlayer cracks or delamination. Through independent control of the layered electrolysis environment and the optimal combination of functional additives, the present invention technically demonstrates the precision manufacturing of high-quality electrolytic copper foil. This technology can be applied as a core process technology to the future electronic materials industry, demonstrating its broad application potential and industrial value.

[0072] Example 1

[0073] The preparation method of electrolytic copper foil based on double electrolytic cells is as follows:

[0074] Step 1: Add a first electrolyte to a first electrolytic cell, wherein the copper ion concentration of the first electrolyte is 80 g / L and the sulfate ion concentration is 100 g / L;

[0075] Stress reliever (additive A): N,N-dimethylthiourea, concentration 0.05g / L;

[0076] Conductive additive (additive B): sodium chloride, concentration 10.0 g / L;

[0077] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.01 g / L;

[0078] The temperature of the first electrolyte is 50° C., and the pH value of the first electrolyte is below 1.0;

[0079] A second electrolyte was added to the second electrolytic tank; the copper ion concentration in the second electrolyte was 40 g / L and the sulfate ion concentration was 75 g / L.

[0080] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.1 g / L;

[0081] Corrosion inhibitor (additive E): polyethylene glycol, concentration 0.5 g / L;

[0082] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.01 g / L;

[0083] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.01 g / L;

[0084] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0085] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell, with a first current density of 30 A / dm 2 , forming a base layer on the surface of the rotating cathode roller; then the base layer is moved to the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller. The second current density is 17.6A / dm 2 , forming a surface layer to obtain a double-layer electroplated electrolytic copper foil;

[0086] Step 3. The double-layer electroplated electrolytic copper foil is further transferred to a Cr rust-proof solution through a roll-to-roll process for rust-proof treatment. The chromium concentration is strictly controlled at 0.55 mg / L, the temperature of the rust-proof solution is 21°C, and the pH is below 3.5. The treated copper foil is then coiled and heat-treated at 65°C for 24 hours to obtain an electrolytic copper foil based on a double electrolytic cell.

[0087] The thickness of the electrolytic copper foil prepared in this embodiment is 4 μm, wherein the thickness of the base layer is 3 μm and the thickness of the surface layer is 1 μm.

[0088] Example 2

[0089] The preparation method of electrolytic copper foil based on double electrolytic cells is as follows:

[0090] Step 1: Adding a first electrolyte to a first electrolytic tank, wherein the copper ion concentration of the first electrolyte is 85 g / L and the sulfate ion concentration is 105 g / L;

[0091] Stress reliever (additive A): N, N-dimethylthiourea, concentration 0.5 g / L;

[0092] Conductive additive (Additive B): Sodium chloride, concentration 15.0 g / L;

[0093] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.1 g / L;

[0094] The temperature of the first electrolyte is 53° C., and the pH value of the first electrolyte is below 1.0;

[0095] A second electrolyte was added to the second electrolytic tank; the copper ion concentration in the second electrolyte was 42 g / L and the sulfate ion concentration was 77 g / L.

[0096] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.5 g / L;

[0097] Corrosion inhibitor (additive E): polyethylene glycol, concentration 1.5 g / L;

[0098] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.02 g / L;

[0099] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.1 g / L;

[0100] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0101] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell, with a current density of 40A / dm2 , forming a base layer on the surface of the rotating cathode roller; then the base layer is moved to the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller. The second current density is 17.6A / dm 2 , forming a surface layer to obtain a double-layer electroplated electrolytic copper foil;

[0102] Step 3. The double-layer electroplated copper foil is transferred to a Cr anti-rust solution through a roll-to-roll process for anti-rust treatment. The chromium concentration is strictly controlled at 0.45 mg / L, the temperature of the anti-rust solution is 22°C, and the pH is below 3.5. The treated copper foil is then coiled and heat-treated at 65°C for 24 hours to obtain an electrolytic copper foil based on a double electrolytic cell.

[0103] The thickness of the electrolytic copper foil prepared in this embodiment is 5 μm, wherein the thickness of the base layer is 4 μm and the thickness of the surface layer is 1 μm.

[0104] Example 3

[0105] The preparation method of electrolytic copper foil based on double electrolytic cells is as follows:

[0106] Step 1: Adding a first electrolyte to a first electrolytic tank, wherein the copper ion concentration of the first electrolyte is 90 g / L and the sulfate ion concentration is 110 g / L;

[0107] Stress reliever (additive A): N, N-dimethylthiourea, concentration 0.2 g / L;

[0108] Conductive additive (additive B): sodium chloride, concentration is 20.0g / L;

[0109] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.2 g / L;

[0110] The temperature of the first electrolyte is 55° C., and the pH value of the first electrolyte is below 1.0;

[0111] A second electrolyte was added to the second electrolytic tank; the copper ion concentration in the second electrolyte was 45 g / L and the sulfate ion concentration was 80 g / L.

[0112] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 1.0g / L

[0113] Corrosion inhibitor (additive E): polyethylene glycol, concentration is 3.0g / L,

[0114] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.05 g / L;

[0115] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.05 g / L;

[0116] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0117] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell, with a first current density of 50 A / dm 2 , forming a base layer on the surface of the rotating cathode roller; then the base layer is moved to the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller. The second current density is 17.6A / dm 2 , forming a surface layer to obtain a double-layer electroplated electrolytic copper foil;

[0118] Step 3. The double-layer electroplated copper foil is transferred to a Cr anti-rust solution through a roll-to-roll process for anti-rust treatment. The chromium concentration is strictly controlled at 0.6 mg / L, the temperature of the anti-rust solution is 18°C, and the pH is below 3.5. The treated copper foil is then rolled and heat-treated at 65°C for 24 hours to obtain an electrolytic copper foil based on a double electrolytic cell.

[0119] The thickness of the electrolytic copper foil prepared in this embodiment is 6 μm, wherein the thickness of the base layer is 5 μm and the thickness of the surface layer is 1 μm.

[0120] Example 4

[0121] The preparation method of electrolytic copper foil based on double electrolytic cells is as follows:

[0122] Step 1: Adding a first electrolyte to a first electrolytic tank, wherein the copper ion concentration of the first electrolyte is 85 g / L and the sulfate ion concentration is 105 g / L;

[0123] Stress reliever (additive A): N, N-dimethylthiourea, concentration 0.3 g / L;

[0124] Conductive additive (Additive B): Sodium chloride, concentration 15.0 g / L;

[0125] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.15 g / L;

[0126] The temperature of the first electrolyte is 52° C., and the pH value of the first electrolyte is below 1.0;

[0127] A second electrolyte was added to the second electrolytic tank; the copper ion concentration in the second electrolyte was 44 g / L and the sulfate ion concentration was 75 g / L.

[0128] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.3 g / L;

[0129] Corrosion inhibitor (additive E): polyethylene glycol, concentration 1.0 g / L;

[0130] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.015 g / L;

[0131] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.05 g / L;

[0132] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0133] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell, with a first current density of 35 A / dm 2 , forming a base layer on the surface of the rotating cathode roller; then the base layer is moved to the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller. The second current density is 17.6A / dm 2 , forming a surface layer to obtain a double-layer electroplated electrolytic copper foil;

[0134] Step 3. The specific process and method are the same as in Example 1.

[0135] The thickness of the electrolytic copper foil prepared in this embodiment is 5 μm, wherein the thickness of the base layer is 4 μm and the thickness of the surface layer is 1 μm.

[0136] Example 5

[0137] The preparation method of electrolytic copper foil based on double electrolytic cells is as follows:

[0138] Step 1: Adding a first electrolyte to a first electrolytic tank, wherein the copper ion concentration in the first electrolyte is 82 g / L and the sulfate ion concentration is 102 g / L;

[0139] Stress reliever (additive A): N,N-dimethylthiourea, concentration 0.4g / L;

[0140] Conductive additive (Additive B): Sodium chloride, concentration 11.0 g / L;

[0141] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.15 g / L;

[0142] The temperature of the first electrolyte is 51° C., and the pH value of the first electrolyte is below 1.0;

[0143] A second electrolyte was added to the second electrolytic tank; the copper ion concentration in the second electrolyte was 41 g / L and the sulfate ion concentration was 76 g / L.

[0144] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.2g / L

[0145] Corrosion inhibitor (additive E): polyethylene glycol, concentration is 0.8g / L,

[0146] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.012 g / L;

[0147] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.01 g / L;

[0148] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0149] Step 2: The specific process and method are the same as in Example 1;

[0150] Step 3. The specific process and method are the same as in Example 1.

[0151] The thickness of the electrolytic copper foil prepared in this embodiment is 4 μm, wherein the thickness of the base layer is 3 μm and the thickness of the surface layer is 1 μm.

[0152] Example 6

[0153] The preparation method of electrolytic copper foil based on double electrolytic cells is as follows:

[0154] Step 1: Adding a first electrolyte to a first electrolytic tank, wherein the copper ion concentration of the first electrolyte is 86 g / L and the sulfate ion concentration is 110 g / L;

[0155] Stress reliever (additive A): N, N-dimethylthiourea, concentration 0.5 g / L;

[0156] Conductive additive (additive B): sodium chloride, concentration 10.0 g / L;

[0157] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.01 g / L;

[0158] The temperature of the first electrolyte is 52° C., and the pH value of the first electrolyte is below 1.0;

[0159] A second electrolyte was added to the second electrolytic tank; the copper ion concentration in the second electrolyte was 43 g / L and the sulfate ion concentration was 76 g / L.

[0160] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.7 g / L;

[0161] Corrosion inhibitor (additive E): polyethylene glycol, concentration 2.5 g / L;

[0162] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.04 g / L;

[0163] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.06 g / L;

[0164] The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

[0165] Step 2: The specific process and method are the same as in Example 1;

[0166] Step 3. The specific process and method are the same as in Example 1.

[0167] The thickness of the electrolytic copper foil prepared in this embodiment is 4 μm, wherein the thickness of the base layer is 3 μm and the thickness of the surface layer is 1 μm.

[0168] Comparative Example 1

[0169] The preparation method of the electrolytic copper foil of this comparative example is the same as that of Example 1. The difference from Example 1 is that the base layer and the surface layer are not separated in this comparative example. The electrolytic copper foil with a total thickness of 4㎛ is deposited in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. Although the electrolyte and additive composition are the same as those of Example 1, the current density is increased to achieve the total thickness requirement of 4㎛. The specific process parameters of the electrolyte are: copper ion concentration 80g / L, sulfate ion concentration 100g / L, electrolyte temperature 50℃, current density 40A / dm 2 .

[0170] The additives in the electrolyte are as follows:

[0171] Stress reliever (additive A): N,N-dimethylthiourea, concentration 0.05g / L;

[0172] Conductive additive (additive B): sodium chloride, concentration 10.0 g / L;

[0173] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.01 g / L;

[0174] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.1g / L

[0175] Corrosion inhibitor (additive E): polyethylene glycol, concentration is 0.5g / L,

[0176] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.01 g / L;

[0177] Surfactant (Additive G): Sodium lauryl sulfate, concentration is 0.01g / L.

[0178] The rust prevention treatment process and heat treatment process are the same as those in Example 1.

[0179] Comparative Example 2

[0180] The preparation method of the electrolytic copper foil of this comparative example is the same as that of Example 2. The difference from Example 2 is that: in this comparative example, the base layer and the surface layer are not separated, and the electrolytic copper foil with a total thickness of 5㎛ is deposited in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. Although the electrolyte and additive composition are the same as those of Example 1, the current density is increased to achieve the requirement of a total thickness of 5㎛. The specific process parameters of the electrolyte are: copper ion concentration 85g / L, sulfate ion concentration 105g / L, electrolyte temperature 53°C, current density 50A / dm 2 .

[0181] The additives in the electrolyte are as follows:

[0182] Stress reliever (additive A): N, N-dimethylthiourea, concentration 0.5 g / L;

[0183] Conductive additive (Additive B): Sodium chloride, concentration 15.0 g / L;

[0184] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.1 g / L;

[0185] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.5 g / L;

[0186] Corrosion inhibitor (additive E): polyethylene glycol, concentration 1.5 g / L;

[0187] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.02 g / L;

[0188] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.1 g / L;

[0189] The rust prevention treatment process and heat treatment process are the same as those in Example 2.

[0190] Comparative Example 3

[0191] The preparation method of the electrolytic copper foil of this comparative example is the same as that of Example 3. The difference from Example 3 is that the base layer and the surface layer are not separated in this comparative example. The electrolytic copper foil with a total thickness of 6㎛ is deposited in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. Although the electrolyte and additive composition are the same as those of Example 1, the current density is increased to achieve the total thickness requirement of 6㎛. The specific process parameters of the electrolyte are: copper ion concentration 90g / L, sulfate ion concentration 110g / L, electrolyte temperature 55°C, current density 60A / dm 2 .

[0192] The additives in the electrolyte are as follows:

[0193] Stress reliever (additive A): N, N-dimethylthiourea, concentration 0.2 g / L;

[0194] Conductive additive (additive B): sodium chloride, concentration is 20.0g / L;

[0195] Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.2 g / L;

[0196] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 1.0g / L

[0197] Corrosion inhibitor (additive E): polyethylene glycol, concentration is 3.0g / L,

[0198] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.05 g / L;

[0199] Surfactant (Additive G): sodium lauryl sulfate, concentration 0.05 g / L;

[0200] The rust prevention treatment process and heat treatment process are the same as those in Example 3.

[0201] Comparative Example 4

[0202] The preparation method of the electrolytic copper foil of this comparative example is the same as that of Example 4. In this comparative example, the base layer and the surface layer are not separated. The electrolytic copper foil with a total thickness of 5㎛ is deposited in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. To achieve the required total thickness of 5㎛, the current density is increased. The specific process parameters of the electrolyte are: copper ion concentration 85g / L, sulfate ion concentration 105g / L, electrolyte temperature 52°C, current density 50A / dm 2 .

[0203] The additives in the electrolyte are as follows:

[0204] Conductive additive (Additive B): Sodium chloride, concentration 15.0 g / L;

[0205] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.3 g / L;

[0206] Corrosion inhibitor (additive E): polyethylene glycol, concentration 1.0 g / L;

[0207] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.015 g / L;

[0208] The rust prevention treatment process and heat treatment process are the same as those in Example 4.

[0209] Comparative Example 5

[0210] The preparation method of the electrolytic copper foil of this comparative example is the same as that of Example 5. The difference from Example 5 is that the base layer and the surface layer are not separated in this comparative example. The electrolytic copper foil with a total thickness of 4㎛ is deposited in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. In order to achieve the required total thickness of 4㎛, the current density is increased. The specific process parameters of the electrolyte are: copper ion concentration 82g / L, sulfate ion concentration 102g / L, electrolyte temperature 51°C, current density 40A / dm 2 .

[0211] The additives in the electrolyte are as follows:

[0212] Conductive additive (Additive B): Sodium chloride, concentration 11.0 g / L;

[0213] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.2g / L

[0214] Corrosion inhibitor (additive E): polyethylene glycol, concentration is 0.8g / L,

[0215] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.012 g / L;

[0216] The rust prevention treatment process and heat treatment process are the same as those in Example 2.

[0217] Comparative Example 6

[0218] The preparation method of the electrolytic copper foil of this comparative example is the same as that of Example 6. The difference from Example 6 is that the base layer and the surface layer are not separated in this comparative example. The electrolytic copper foil with a total thickness of 4㎛ is deposited in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. To achieve the required total thickness of 4㎛, the current density is increased. The specific process parameters of the electrolyte are: copper ion concentration 86g / L, sulfate ion concentration 110g / L, electrolyte temperature 52°C, current density 40A / dm 2 .

[0219] The additives in the electrolyte are as follows:

[0220] Conductive additive (additive B): sodium chloride, concentration 10.0 g / L;

[0221] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.7 g / L;

[0222] Corrosion inhibitor (additive E): polyethylene glycol, concentration 2.5 g / L;

[0223] Brightener (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.04 g / L;

[0224] The rust prevention treatment process and heat treatment process are the same as those in Example 6.

[0225] The concentrations of the additives used in Examples 1 to 6 of the present invention and Comparative Examples 1 to 6 are shown in Table 1.

[0226] Table 1 Concentration of additives used in Examples 1 to 6 and Comparative Examples 1 to 6

[0227]

[0228] The performance indicators of the electrolytic copper foils prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested respectively, and the results are shown in Table 2.

[0229] Table 2 Performance indicators of the electrolytic copper foils prepared in Examples 1 to 6 and Comparative Examples 1 to 6

[0230]

[0231] The data in Tables 1 and 2 show that in the production of electrolytic copper foil, by constructing the electrolytic system into a dual-electrolytic cell structure and applying optimized electrolytic conditions and additive compositions to the base layer and surface layer, it is confirmed that the quality and uniformity of the coating are significantly improved compared to the existing single-electrolytic cell method. In Examples 1 to 6, a dual-electrolytic cell system with a separate base layer (3-5μm) and surface layer (1μm) was used. This achieved excellent physical properties of the surface layer, including an S-surface roughness (Ra) of 0.08-0.12μm, an M-surface roughness (Rz) of 0.55-0.65μm, a tensile strength of 380-420MPa, an elongation of 5.0-7.0%, and a curl of less than 5mm. In particular, the base layer ensures structural support and thickness uniformity by adding stress relievers, conductive additives and grain growth regulators at optimal concentrations under high current density and high concentration electrolyte conditions; while the surface layer forms a stable layer with ultra-low roughness and high tensile strength characteristics through low current density and precisely controlled additive composition. In contrast, Comparative Examples 1 to 6 were manufactured using a single electrolytic cell method and electroplated as a whole under the same conditions, failing to achieve functional separation of the base layer and the surface layer. As a result, composite factors such as mutual interference of additives, uneven current distribution, and abnormal deposition reactions caused the quality of the coating to decline, with the overall performance being increased roughness, reduced tensile strength, and increased curling. This clearly shows that the single electrolytic cell system has structural limitations in ensuring the quality of the coating due to the inability to achieve precise layer control.

[0232] In summary, this invention utilizes a dual electrolytic cell system to clearly separate the desired properties of each layer, and applies optimized electrolytic conditions and additive combinations for each layer. This technology has been proven to outperform existing technologies in terms of coating accuracy, structural stability, surface characteristics, and mechanical properties. In particular, this technological structure can meet the requirements of high-end electrolytic copper foil, including roughness and curl control, high-speed signal transmission stability, and compatibility with high-precision circuits. It can serve as a core process that provides decisive technological competitiveness in high-value-added electronic materials such as next-generation AI computing technology, semiconductor packaging, 6G communications, and high-frequency circuit substrates.

Claims

1. A method for preparing electrolytic copper foil based on a double electrolytic cell, characterized in that: The details are as follows: Step 1: adding a first electrolyte to a first electrolytic tank and adding a second electrolyte to a second electrolytic tank; Step 2: applying a first current between the first fixed anode plate and the rotating cathode roller of the first electrolytic cell to form a base layer on the surface of the rotating cathode roller; The base layer is then moved into a second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the electroplating roller to form a surface layer, thereby obtaining a double-layer electrolytic copper foil. Step 3. The double-layer electroplated copper foil is then transferred to a Cr anti-rust solution for anti-rust treatment via a roll-to-roll process. The treated copper foil is then rolled and heat-treated at 65°C for 24 hours to obtain an electrolytic copper foil based on a double electrolytic cell. The first electrolyte comprises copper ions, sulfate ions and a first additive, wherein the copper ion concentration in the first electrolyte is 80-90 g / L and the sulfate ion concentration is 100-110 g / L; The second electrolyte comprises copper ions, sulfate ions and a second additive, wherein the copper ion concentration in the second electrolyte is 40-45 g / L and the sulfate ion concentration is 75-80 g / L; The first additive includes a stress reliever, a conductive additive and a grain growth regulator; The stress reliever is N, N-dimethylthiourea with a concentration of 0.05-0.5 g / L; The conductive additive is sodium chloride with a concentration of 10.0-20.0 g / L; The grain growth regulator is 2-butyne-1,4-diol, with a concentration of 0.01-0.2 g / L; The second additive includes a leveling agent, a corrosion inhibitor, a brightener and a surfactant; The leveling agent is sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, with a concentration of 0.1-1.0 g / L; The corrosion inhibitor is polyethylene glycol with a concentration of 0.5-3.0 g / L; The brightener is 3-mercapto-1-propanesulfonic acid with a concentration of 0.01-0.05 g / L; The surfactant is sodium lauryl sulfate with a concentration of 0.01-0.1 g / L.

2. The method for preparing electrolytic copper foil based on a double electrolytic cell according to claim 1, characterized in that: The temperature of the first electrolyte is 50-55° C., and the pH value of the first electrolyte is below 1.0; The temperature of the second electrolyte is 45° C., and the pH value of the second electrolyte is the same as that of the first electrolyte.

3. The method for preparing electrolytic copper foil based on a double electrolytic cell according to claim 1, characterized in that: The current density of the first current in step 2 is 30-50A / dm 2 ; The current density of the second current is 17.6A / dm 2 .

4. The method for preparing electrolytic copper foil based on a double electrolytic cell according to claim 1, characterized in that: In step 3, the Cr rust preventive solution comprises chromium ions and glucose, wherein the chromium ion concentration is 0.45-0.60 mg / L, the glucose concentration is 7.0 g / L, the rust preventive solution temperature is 18-22° C., and the pH is below 3.

5.

5. An electrolytic copper foil produced according to the method for producing an electrolytic copper foil using a dual electrolytic cell according to any one of claims 1 to 4, the electrolytic copper foil comprising a base layer and a surface layer, the surface layer being plated on the outside of the base layer, the electrolytic copper foil having an S-side surface roughness of 0.08-0.12, an M-side surface roughness of 0.55-0.65, a room-temperature tensile strength after heat treatment of 380-420 MPa, an room-temperature elongation after heat treatment of 5.0-7.0%, and a curl of less than 5 mm.

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