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

Abstract

The invention discloses a copper foil preparation system with double electrolytic baths. The copper foil preparation system comprises a first electrolytic bath and a second electrolytic bath, the first electrolytic tank comprises a first fixed anode plate and a rotating cathode roller which are separately arranged, the second electrolytic tank comprises a second fixed anode plate and an electroplating roller which are separately arranged, and a roll-to-roll conveying structure is adopted between the first electrolytic tank and the second electrolytic tank; the device further comprises a PLC control system and a real-time sensor, and the PLC control system and the real-time sensor are electrically connected with the first electrolytic bath and the second electrolytic bath respectively. The invention further discloses a method for preparing the electrolytic copper foil by using the copper foil preparation system and the prepared copper foil. According to the copper foil preparation system with the double electrolytic baths, a double-electrolytic-bath structure is adopted, a plating layer is clearly divided into a base layer and a surface layer, and therefore the problem that independent control over layered physical properties is difficult to achieve in a traditional single electrolytic bath mode is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic copper foils, and relates to a copper foil preparation system with a dual electrolytic cell, and also relates to a method for preparing an electrolytic copper foil using the above copper foil preparation system, and further relates to an electrolytic copper foil prepared by using the above preparation method. Background Art

[0002] An electrolytic copper foil is a metal thin film formed by the electrochemical reaction of metal ions in an electrolyte solution, so that the metal ions are deposited on the surface of a cathode body. It is widely used as a core material in high-functional electronic components, such as flexible printed circuit boards (FPCBs), current collectors for lithium-ion batteries, high-frequency circuit boards, semiconductor packages, electromagnetic shielding materials, and other fields. The manufacture of electrolytic copper foils is generally based on a system composed of a rotary cathode roller, an electrolytic cell for containing the electrolyte, and an anode plate. When the lower part of the cathode roller is immersed in the electrolyte at a certain depth and rotates, a current is applied between the anode plate and the cathode roller, and copper ions (Cu 2+ ) in the electrolyte will undergo reduction deposition on the surface of the cathode roller, thereby forming a copper foil film. When the copper plating layer reaches a certain thickness, it will be peeled off and continuously recovered. By adjusting parameters such as current density, electrolyte composition, temperature, additive concentration and type, the physical properties of the copper foil, such as thickness, surface roughness, grain structure, hardness and mechanical strength, can be controlled. Since the electrolytic copper foil manufacturing industry has long been centered on equipment simplification and high-speed / high-volume production, the traditional electrolytic copper foil manufacturing technology has always adopted the process of forming all the plating layers at one time in a single process, and in most cases, only a single electrolytic cell, a single electrolyte and a single current condition are used for production. For application fields with low requirements for precision characteristics, such as current collectors for lithium-ion batteries or copper foils for general-purpose FPCBs, this method is sufficient to meet the quality requirements. In addition, in an industrial environment where production efficiency is prioritized, attempts to perform functional stratification treatment on the plating layer itself are not active. The industry generally believes that if the process is complicated, it will bring adverse effects in many aspects such as equipment maintenance, operation stability, and additive management. Therefore, in traditional technologies, the structural design of using different electroplating conditions for the base layer and the surface layer has not actually been substantially attempted or introduced into industrial production. However, with the rapid development of high-value-added application fields such as high-frequency circuit boards, AI / 6G communication components, and high-density semiconductor packages, the market's quality requirements for electrolytic copper foils are evolving towards precision and compounding, and at the same time, the demand for the degree of freedom in physical property control is also increasing. In this context, the limitations of traditional technologies are becoming increasingly prominent in the following aspects.

[0003] First, the plating layer of the electrolytic copper foil needs to be designed by dividing it into a base layer and a surface layer 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 conditions of high current density and high concentration of copper ions. Although these conditions can effectively improve production efficiency and ensure the thickness of the base layer, due to the easy occurrence of grain coarsening growth or an increase in surface roughness during high-speed deposition, there are limitations in achieving precise surface quality. On the other hand, as the outer functional area of the electroplated layer, the surface 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 adopted, and the performance is optimized by adjusting the deposition rate and ensuring the stable action of additives. However, in the traditional single electrolytic cell process, since these mutually contradictory conditions cannot be applied in layers, the performance of at least one of the base layer and the surface layer will inevitably be damaged, ultimately forming a technical limitation that the optimal quality cannot be obtained simultaneously on the double-layer structure. Second, when functional additives act on the entire electrolyte, the additives that should only affect the surface layer will penetrate into the base layer, which may lead to quality defects such as a decrease in grain uniformity, interlayer stress imbalance, curling phenomenon, and microcracks. Third, there are technical difficulties in the precise control of the interlayer structure. Although methods of adjusting current conditions or additive components over time have been attempted in a single electrolytic cell, due to factors such as electrolyte reaction delay, formation of ion concentration gradients, and the influence of residual additives, it is difficult to ensure the uniformity of the interface quality, and the process stability may decrease during repeated production. Fourth, the process relying on functional additives is difficult to maintain stability during long-term operation. The change in the reaction characteristics of the electrolyte caused by the decomposition, accumulation, and interaction of additives will result in differences in the plating quality between the initial stage and the later stage, thereby causing problems such as a decrease in the yield and quality consistency. Fifth, with the expansion of the demand for high-performance products, the functional requirements of copper foils are becoming increasingly diversified, but the single electrolytic cell structure is difficult to achieve the process flexibility and condition independence required for customized process design. Especially for diverse product series such as high-flexibility soft copper foils, high-hardness copper foils for communication substrates, and low-loss conductors, a process structure with hierarchical independent control capabilities is urgently needed, which is exactly what the existing technology 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. By adopting a dual electrolytic cell structure, the plating layer is clearly divided into a base layer and a surface layer, enabling each layer to apply optimized electrolysis conditions, thereby solving the problem that it is difficult to achieve independent control of the physical properties of each layer in the traditional single electrolytic cell method.

[0005] The 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 using the above preparation method.

[0007] The first technical solution adopted by the present invention is a copper foil preparation system with a double electrolytic cell, including a first electrolytic cell and a second electrolytic cell. Both the first electrolytic cell and the second electrolytic cell include a dissolution tank, a waste liquid tank, a purified liquid tank, an electrolyte supply system, a temperature control system, a current supply system, and an additive injection system. 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 a plating roller, and the second fixed anode plate and the plating roller are separately arranged. A roll-to-roll transfer structure is adopted between the first electrolytic cell and the second electrolytic cell, and a cleaning roller and a hot air dryer are arranged between the first electrolytic cell and the second electrolytic cell. It also includes a PLC control system and a real-time sensor, and the PLC control system and the real-time sensor are electrically connected to the first electrolytic cell and the second electrolytic cell respectively.

[0008] The characteristics of the present invention also lie in: The diameter of the rotating cathode roller in the first electrolytic cell is 2500 - 3000 mm, and the diameter of the plating roller in the second electrolytic cell is 1500 - 1700 mm.

[0009] The second technical solution adopted by the present invention is a preparation method of an electrolytic copper foil based on a double electrolytic cell, using the above copper foil preparation system with a double electrolytic cell, specifically as follows: Step 1: Add a first electrolyte to the first electrolytic cell and add a second electrolyte to the second electrolytic cell. Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller in the first electrolytic cell to form a base layer on the surface of the rotating cathode roller; then this base layer is moved into the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the plating roller to form a surface layer, obtaining a double-layer electroplated electrolytic copper foil. Step 3: Move the double-layer electroplated electrolytic copper foil through a roll-to-roll process to continue into the Cr rust inhibitor for rust prevention treatment, then curl the treated copper foil, and then heat-treat it at 65 °C for 24 h to obtain an electrolytic copper foil based on a double electrolytic cell.

[0010] The characteristics of the present invention also lie in: The first electrolyte includes copper ions, sulfate ions, and a first additive. 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 includes copper ions, sulfate ions, and a second additive. The copper ion concentration in the second electrolyte is 40 - 45 g / L, and the sulfate ion concentration is 75 - 80 g / L. 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.

[0011] The first additive includes a stress reliever, a conductive aid, and a grain growth regulator; The stress reliever is N,N - dimethylthiourea, and its concentration is 0.05 - 0.5 g / L; The conductive aid is sodium chloride, and its concentration is 10.0 - 20.0 g / L; The grain growth regulator is 2 - butyne - 1,4 - diol, and its concentration is 0.01 - 0.2 g / L.

[0012] The second additive includes a leveling agent, a corrosion inhibitor, a brightening agent, and a surfactant; The leveling agent is sodium 3 - (5 - mercapto - 1 - tetrazolyl)benzenesulfonate, and its concentration is 0.1 - 1.0 g / L; The corrosion inhibitor is polyethylene glycol, and its concentration is 0.5 - 3.0 g / L; The brightening agent is 3 - mercapto - 1 - propanesulfonic acid, and its concentration is 0.01 - 0.05 g / L; The surfactant is sodium dodecyl sulfate, and its concentration is 0.01 - 0.1 g / L.

[0013] In step 2, the current density of the first current is 30 - 50 A / dm 2 ; the current density of the second current is 17.6 A / dm 2 .

[0014] In step 3, the Cr antirust solution includes chromium ions and glucose. The concentration of chromium ions is 0.45 - 0.60 mg / L, the concentration of glucose is 7.0 g / L, the temperature of the antirust solution is 18 - 22°C, and the pH is below 3.5.

[0015] The third technical solution adopted in the present invention is that the electrolytic copper foil prepared by the method for preparing electrolytic copper foil based on a dual electrolytic cell 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 - 6 μm, the thickness of the base layer is 3 - 5 μm, and the thickness of the surface layer is less than or equal to 1 μm.

[0016] The beneficial effects of the present invention are: (1)The copper foil preparation system of the present invention with a dual electrolytic cell configures a rotary cathode roller with a larger diameter in the first electrolytic cell and a plating roller with a smaller diameter in the second electrolytic cell. Through this structural design, even under the condition of the same conveying speed, the residence time and current conditions of each layer can be optimized, thereby obtaining significant structural flexibility. The base layer and the surface layer are respectively formed in independent electrolytic cells by electrolytic plating, so as to realize the independent control of the physical properties of each layer and precise plating quality. The core function of the base layer is to ensure the copper foil thickness and mechanical support, while the surface layer focuses on reducing roughness and improving adhesion. This functional division realizes the precise control of high-performance plating; (2)The copper foil preparation system of the present invention with a dual electrolytic cell can prevent interface pollution and maintain high reproducibility in repeated processes 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; (3)The copper foil preparation method of the present invention with a dual electrolytic cell completely isolates the electrolyte components and additives used in each electrolytic cell, fundamentally avoiding problems such as reaction imbalance, excessive accumulation or decomposition that may be caused by the interaction of additives. Thus, in the base layer, by adding stress relievers, conductive aids, grain growth regulators, etc., thickness uniformity and structural stability are ensured; while in the surface layer, leveling agents, corrosion inhibitors, brighteners, surfactants, etc. are used to achieve roughness control and improvement of adhesion performance; (4)The copper foil preparation method of the present invention with a dual electrolytic cell can effectively relieve the internal stress of the plating layer and achieve interlayer stress balance through a heat treatment process at 65°C for 24 hours after plating, thereby synchronously suppressing curl deformation and improving the interfacial bonding strength. The electrolytic copper foil prepared by the method of the present invention can obtain excellent physical properties with a thickness of 3.5 - 6 μm, S surface roughness (Ra) of 0.08 - 0.12, M surface roughness (Rz) of 0.55 - 0.65, room temperature tensile strength of 380 - 420 MPa after heat treatment, room temperature elongation of 5.0 - 7.0% after heat treatment, and curl within 5 mm. In addition, this technology can achieve an integrated metal layer structure without additional bonding processes, and effectively relieve internal stress and suppress curl deformation through heat treatment after plating, thereby stabilizing the material properties, which can minimize quality deviation and improve product quality in subsequent processing operations such as lamination, cutting, and lamination. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the copper foil preparation system of the present invention with a dual electrolytic cell. Detailed Embodiments

[0018] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0019] The copper foil preparation system of the present application has a dual electrolytic cell, as Figure 1 shown, including a first electrolytic cell and a second electrolytic cell. Both the first electrolytic cell and the second electrolytic cell include a dissolution tank, a waste liquid tank, a purified liquid tank, an electrolyte supply system, a temperature control system, a current supply system, and an additive injection system; The first electrolytic cell includes a first fixed anode plate and a rotating cathode roll, and the first fixed anode plate and the rotating cathode roll are separately arranged. The second electrolytic cell includes a second fixed anode plate and a plating roll, and the second fixed anode plate and the plating roll are separately arranged; Among them, the diameter of the rotating cathode roll in the first electrolytic cell is 2500 - 3000 mm. A large-diameter rotating cathode roll is used to ensure the stable formation of the thickness of the base layer. The diameter of the plating roll in the second electrolytic cell is 1500 - 1700 mm. A plating roll with a smaller diameter is used so that under the condition of the same conveying speed, precise formation of a thin coating layer can still be achieved within a shorter residence time. This structural differential design significantly improves the accuracy of layered coating control and can effectively achieve the best deposition environment where the physical properties of each layer match the process requirements.

[0020] A roll-to-roll conveying structure is adopted between the first electrolytic cell and the second electrolytic cell, and a cleaning roll and a hot air dryer are provided between the first electrolytic cell and the second electrolytic cell; It further includes a PLC control system and a real-time sensor, and the PLC control system and the real-time sensor are electrically connected to the first electrolytic cell and the second electrolytic cell respectively.

[0021] The above structural design is based on the following technological characteristic requirements: The electrolysis conditions and additive components required for the base layer and the surface layer must be strictly distinguished, and mutual interference must be completely eliminated. Since the separation of the electrolyte components starting from the pretreatment stage will have a decisive impact on the overall coating quality, it is of crucial significance to adopt a completely independent system configuration. The structural design of the present invention aims to reflect the differential configuration of layered electrolysis conditions from the system architecture.

[0022] A transfer structure with minimized air exposure is adopted between the first electrolytic cell and the second electrolytic cell, and devices such as a cleaning roller and a hot air dryer are configured to effectively prevent the mutual mixing of the electrolytes of different electrolytic cells and the surface contamination of the copper foil. This structure plays a key role in ensuring the interfacial stability and the consistency of additive reactions during the formation of the surface layer, and can maintain high reproducibility in the repeated process. In addition, the electroplating conditions of each electrolytic cell are integrally managed and controlled through a PLC control system and a real-time sensor monitoring device, so as to ensure the uniformity of electroplating quality and the process stability even in a long-term continuous production environment. Finally, the dual electrolysis system of the present invention not only provides a structure that can independently achieve the required characteristics of the base layer and the surface layer respectively, but also combines the quality reliability and design flexibility that are difficult to achieve by the traditional single electrolytic cell method through the electrochemically uniform bonding of each layer, which is a core process technology. Especially in high-value-added electronic material fields such as high-frequency communication, semiconductor packaging, and precision circuit boards, the industrial application of high-performance electrolytic copper foil can be accurately realized, with significant market competitiveness.

[0023] The preparation method of the electrolytic copper foil based on a dual electrolytic cell of the present invention uses the above copper foil preparation system with a dual electrolytic cell, specifically as follows: Step 1: Add a first electrolyte to the first electrolytic cell and a second electrolyte to the second electrolytic cell; Among them, the first electrolyte includes copper ions, sulfate ions and a first additive. The copper ion concentration in the first electrolyte is 80-90 g / L, the sulfate ion concentration is 100-110 g / L, the temperature of the first electrolyte is 50-55 °C, and the pH value of the first electrolyte is below 1.0.

[0024] As the process of forming the base layer, the most critical element of the first electrolytic cell is to ensure the thickness guarantee and structural stability required for the mechanical support and conductivity of the electrolytic copper foil. Therefore, an additive combination that can promote the dense and stable growth of the base layer needs to be adopted. The first additive specifically includes a stress reliever, a conductivity aid and a grain growth regulator.

[0025] Specifically, the stress reliever is N,N-dimethylthiourea, and the concentration is 0.05-0.5 g / L; the stress reliever can effectively prevent the uneven growth of grains or the accumulation of excessive stress in a high-speed electroplating environment, and at the same time can ensure the surface flatness and grain density of the deposited layer. When the concentration of the stress reliever is lower than 0.05 g / L, the ability to regulate grain growth weakens, which may lead to an increase in surface roughness and the generation of microcracks; when the stress reliever exceeds 0.5 g / L, the reduction reaction of metal ions will be overly inhibited, resulting in a decrease in electroplating rate and a decrease in current efficiency, etc.

[0026] The conductive additive is sodium chloride, with a concentration of 10.0 - 20.0 g / L. Its function is to increase the total conductivity of ions in the electrolyte, thereby ensuring the uniformity of 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 10.0 g / L, it may cause the current to concentrate in some areas, exacerbating the plating deviation. When the sodium chloride exceeds 20.0 g / L, the viscosity may increase due to the interaction between ions in the electrolyte, resulting in phenomena such as plating scars or blockages. The grain growth regulator is 2-butyne-1,4-diol, with a concentration of 0.01 - 0.2 g / L. The grain growth regulator finely controls the boundaries of the deposited metal crystal particles during the electroplating process and inhibits the attachment of bubbles on the cathode surface, thereby preventing the generation of fine pinholes, especially problems such as abnormal growth of crystal grains or surface pores that may occur under high current density conditions, and contributing to the densification of the metal crystals in the base layer and the improvement of the durability of the coating. If the concentration of the grain growth regulator is lower than 0.01 g / L, the insufficient bubble removal function will lead to an increase in pores in the coating, and the local deviation of the electroplating thickness may be exacerbated. On the contrary, when the concentration of the grain growth regulator exceeds 0.2 g / L, the gas removal reaction at the cathode interface is overly inhibited, which may cause surface problems due to hydrogen generation, and there may also be a phenomenon of stress concentration in the metal structure of the coating.

[0027] The second electrolyte includes copper ions, sulfate ions, and a second additive. In the second electrolyte, the copper ion concentration is 40 - 45 g / L, the sulfate ion concentration is 75 - 80 g / L, 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.

[0028] The second electrolytic cell is a process for forming the surface layer, which requires precise control of the roughness, crystal size, directionality, adhesion, etc. of the final surface layer formed on the base layer. Therefore, the reaction uniformity under low current density conditions and the reaction persistence of the additive are crucial. The second additive includes additives such as a leveling agent, a corrosion inhibitor, a brightening agent, and a surfactant for enhancing surface properties. Among them, the leveling agent is Sodium 3-(5-mercapto-1-tetrazolyl)benzene sulfonate (MBT-S), with a concentration of 0.1~1.0 g / L. This substance controls the crystal growth process on the coating surface, inhibits the formation of local surface protrusions or sharp crystals, and maintains the uniformity of the microstructure of the electroplated layer. In particular, MBT-S can induce uniform current distribution and effectively reduce the surface roughness (Rz). When the concentration exceeds 1.0 g / L, the electroplating speed will decrease due to excessive inhibition of surface reactions, and crystal aggregation of the coating may occur; The corrosion inhibitor is Polyethylene Glycol (PEG), with a concentration of 0.5~3.0 g / L. The influence of PEG on the coating varies according to its molecular weight, but it generally has the effects of slowing down the electroplating speed, maintaining uniform precipitation of metal ions to reduce the coating thickness deviation. By adjusting the reaction speed on the cathode surface, PEG can achieve dense crystal formation, and at the same time has the effects of relieving internal stress and preventing microcracks. If the concentration of polyethylene glycol is lower than 0.5 g / L, the precipitation regulation effect is weak, which may cause uneven coating; when the concentration of polyethylene glycol exceeds 3.0 g / L, the electroplating speed will be excessively reduced, resulting in a decrease in production efficiency and an increased risk of hydrogen retention or internal pores in the coating; The brightening agent 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 can effectively fine-tune the crystal grain size and form a smooth and bright surface. Although it has a similar function to SPS, its reaction speed is relatively mild. Even under low current density conditions, it can achieve stable brightening effects and uniform metal crystal structure. Therefore, it can endow the surface layer with uniform reflection characteristics and high-frequency signal conduction efficiency, and at the same time is conducive to minimizing the physical property deviation in the coating. If the concentration of 3-mercapto-1-propanesulfonic acid is lower than 0.01 g / L, the crystal grain refinement effect will decrease significantly. If the concentration of 3-mercapto-1-propanesulfonic acid exceeds 0.05 g / L, the deposition rate may decrease and the gloss may be uneven due to excessive inhibition of the reaction.

[0029] The surfactant is Sodium Dodecyl Sulfate, and its concentration is 0.01 - 0.1 g / L. This surfactant can quickly remove the bubbles generated during the electroplating process and improve the wettability of the cathode surface, thus preventing coating defects. Especially, the surface layer is thinner than the base layer and requires fine crystal control. If microbubbles remain on the surface, it is extremely easy to cause defects such as pinholes and black spots. This surfactant can block these problems at the root and help the metal ions in the electrolyte cover the entire cathode surface evenly. If the concentration of Sodium Dodecyl Sulfate is lower than 0.01 g / L, the effect of reducing the interfacial tension is insufficient. If the concentration of Sodium Dodecyl Sulfate exceeds 0.1 g / L, it may cause adverse effects on the subsequent cleaning process due to excessive foaming and turbid electrolyte.

[0030] The above additives need to be dissolved in ultrapure water, stirred and then added. Their composition and concentration conditions are strictly set to ensure stability in the electrolyte.

[0031] The preparation processes of the first electrolyte and the second electrolyte in the present invention are as follows: Put pure copper wires with a purity of more than 99.9% and sulfuric acid into the solution tank of the first electrolytic cell, and prepare the first electrolyte through stirring and dissolution. This electrolyte maintains a flowing cycle through the waste liquid tank in the first electrolytic cell, so as to maintain stable copper ion and sulfate ion concentrations. Similarly, after the copper wires and sulfuric acid are dissolved in the dissolution tank in the second electrolytic cell for the second electrolyte, it realizes a circulating flow through the waste liquid tank in the second electrolytic cell, so as to maintain the optimal composition required for this electrolytic cell; during the circulation process, the possible crystallization problems caused by heat loss are prevented through their respective heat exchangers; after the refined electrolytes are separately passed through diatomaceous earth filters to remove impurities, they are separately transferred to their respective clean liquid tanks. By configuring the dissolution tank, waste liquid tank, and clean liquid tank completely independently in each electrolytic cell in this way, the electrolysis conditions applicable to the base layer and the surface layer (such as parameters like copper ion and sulfate ion concentrations, temperature, flow rate, etc.) can be precisely controlled without interference. Thereafter, to stably manufacture electrolytic copper foil and achieve the required physical properties of each layer, functional additives need to be put into each additive storage tank together with ultrapure water, dissolved and stirred, and then separately injected into the two clean liquid tanks. Each electrolyte added with additives is precisely filtered through a fine filter and then supplied to the first electrolytic cell and the second electrolytic cell respectively.

[0032] This additive separation solution fundamentally eliminates the problems caused by the interaction of additives commonly found in single electrolytic cell processes - including reaction imbalance, decreased electroplating efficiency, excessive accumulation or decomposition, etc., thus enabling precise control for each coating layer and significantly improving quality stability. In addition, since the electroplating reactions in each electrolytic cell are 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 induced by electron migration. In summary, according to the electrolytic copper foil laminated structure of the present invention, even if the coating layer is composed of two layers, it is not a physically heterogeneous laminated structure, but a combination formed like a metal crystal. Therefore, boundary defects such as interface peeling, stress concentration, or cracks hardly occur. In fact, in the dual electrolytic cell system, without additional heat treatment or lamination process after electroplating, the interface strength and physical property uniformity can reach performance equivalent to or even better than that of a single-layer electroplating process.

[0033] Step 2. Apply a first current between the first fixed anode plate and the rotating cathode roll in the first electrolytic cell, and the first current density is 30 - 50 A / dm 2 , to form a base layer on the surface of the rotating cathode roll; subsequently, this base layer is moved into 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 roll to form a surface layer, and the second current density is 17.6 A / dm 2 , and finally a double-layer electroplated electrolytic copper foil is obtained; Step 3. Move the double-layer electroplated electrolytic copper foil through a roll-to-roll process to the Cr rust inhibitor solution for rust prevention treatment, then curl the treated copper foil, and then heat-treat it at 65 °C for 24 h to obtain an electrolytic copper foil based on a dual electrolytic cell.

[0034] Among them, the Cr rust inhibitor solution includes chromium ions and glucose, the concentration of chromium ions is 0.45 - 0.60 mg / L, the concentration of glucose is 7.0 g / L, the temperature of the rust inhibitor solution is 18 - 22 °C, and the pH is below 3.5.

[0035] The preparation method of the Cr rust inhibitor solution is: add chromium trioxide and glucose to ultrapure water respectively, and then filter it through a fine filter and inject it into the rust prevention tank in the electrolytic cell.

[0036] To prevent the oxidation of the surface of the electrolytic copper foil, chromium trioxide needs to be dissolved in ultrapure water and stirred, and then filtered through a fine filter and transferred to the Cr rust prevention tank for rust prevention treatment; but due to its strong toxicity and harm to the environment, glucose is added as a reducing agent at the same time. This rust inhibitor solution is immediately coated on the surface of the copper foil in the second electrolytic cell, which can effectively prevent oxidation and ensure surface stability.

[0037] The dual electrolysis system of the present invention fundamentally solves the structural and physical limitations existing in the traditional single electrolytic cell preparation method and has composite technical advantages. In particular, by distinguishing the base layer and the surface layer in units of electrolytic cells, the optimized electroplating conditions can be applied respectively according to their physical property targets, so it has significant advantages in ensuring the functionality and quality consistency of the entire coating. Specifically, in the first electrolytic cell, by setting a high current density environment, the base layer of the electrolytic copper foil can be rapidly grown. This process can not only provide 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 ensure that the grain density and flatness can be 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, enabling the functional additives to play their roles fully. Under this condition, precise physical property control such as grain refinement, reduction of surface roughness, improvement of adhesion characteristics with semiconductor packaging substrates and high-frequency communication circuit boards, and control of grain orientation can be achieved. In particular, as the key part directly contacting the external circuit or substrate, the surface layer needs to have high functionality such as anti-electromagnetic wave loss, antioxidant stability, surface flatness, and signal transmission efficiency, so precise electroplating conditions must be adopted. This structural separation design of forming the base layer under high current conditions and then sequentially forming the surface layer under low current conditions can effectively achieve differential control of physical properties.

[0038] In the present invention, the reasons for setting the second electrolyte temperature and current density as fixed conditions are as follows: As the functional area in the entire electroplated layer that directly contacts the external circuit, the surface layer needs to possess 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 the single electrolytic cell method. It is extremely sensitive to changes in current density or temperature deviation, easily leading to quality problems such as uneven crystal grains, increased roughness, pinholes, and interface defects. Therefore, stable current density and temperature parameters must be adopted for the electroplating conditions of the surface layer to ensure high reproducibility and consistency during repeated processes. In addition, since it is necessary to continuously pass through two electrolytic cells at the same linear speed in a roll-to-roll manner in the dual electrolysis system, the structure of each electrolytic cell is specifically designed for its electroplating purpose. Specifically, the first electrolytic cell is dedicated to the formation of the base layer, and its design focus is to ensure thickness and mechanical support through long-time electrodeposition at a high current density. For this purpose, a large-diameter rotating cathode roller is used to fully extend the residence time of the copper foil in the electrolyte, thereby achieving uniform formation of a thick base layer. The second electrolytic cell is dedicated to the formation of the surface layer, and it is necessary to achieve thin-layer precision electroplating. Moreover, the reaction sensitivity of additives and the grain control function need to be considered. Therefore, a small-diameter electroplating roller is used. Even within a short residence time, it can significantly improve roughness, enhance gloss, and optimize bonding characteristics under the current density condition of 17.6 A / dm². This design of separating the residence time based on the difference in the diameters of the cathode roller and the electroplating roller can achieve optimized control for the characteristics of each layer according to the electrodeposition time and control environment of each electrolytic cell under the same linear speed condition, thereby ensuring independent control of the physical properties of each layer and high-precision electroplating quality. In addition, this differential setting of electrolysis conditions can accurately achieve the physical properties required for each layer, such as ensuring the mechanical support and conductivity of the base layer, improving the roughness and enhancing the bonding characteristics of the surface layer. In particular, it plays a key role in controlling the internal stress distribution and grain microstructure of the coating. In this dual electrolytic cell structure, the additives used for each coating are also differentiated and independently added according to their functional purposes.

[0039] The electrolytic copper foil prepared by the method for preparing electrolytic copper foil based on a dual electrolytic cell in the present invention, 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 - 6 μm, the thickness of the base layer is 3 - 5 μm, and the thickness of the surface layer is less than or equal to 1 μm. The structure of the electrolytic copper foil of the present invention can form an integrated metal layer without interlayer cracks or peeling. Through the independent control of the layered electrolysis environment and the optimal combination of functional additives, the present invention technically proves that high-quality electrolytic copper foil can be precisely manufactured and can be applied as a core process technology in the future electronic materials industry, having broad application possibilities and industrial value.

[0040] Example 1 Preparation method of electrolytic copper foil based on double electrolytic cells, specifically as follows: Step 1: Add the first electrolyte into the first electrolytic cell. The concentration of copper ions in the first electrolyte is 80 g / L, and the concentration of sulfate ions is 100 g / L; Stress reliever (additive A): N, N-dimethylthiourea, concentration is 0.05 g / L; Conductive aid (additive B): Sodium chloride, concentration is 10.0 g / L; Grain growth regulator (additive C): 2-butyne-1,4-diol, concentration is 0.01 g / L; The temperature of the first electrolyte is 50 °C, and the pH value of the first electrolyte is below 1.0; Add the second electrolyte into the second electrolytic cell; the concentration of copper ions in the second electrolyte is 40 g / L, and the concentration of sulfate ions is 75 g / L.

[0041] Leveling agent (additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration is 0.1 g / L; Corrosion inhibitor (additive E): Polyethylene glycol, concentration is 0.5 g / L; Brightening agent (additive F): 3-mercapto-1-propanesulfonic acid, concentration is 0.01 g / L; Surfactant (additive G): Sodium dodecyl sulfate, concentration is 0.01 g / L; 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.

[0042] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller in the first electrolytic cell. The first current density is 30 A / dm 2 , to form a base layer on the surface of the rotating cathode roller; subsequently, the base layer is moved into the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the plating roller. The second current density is 17.6 A / dm 2 , to form a surface layer, and a double-layer electroplated electrolytic copper foil is obtained; Step 3. Move the double-layer electroplated electrolytic copper foil through the roll-to-roll process to the Cr antirust solution for antirust treatment. Among them, the chromium concentration is strictly controlled at 0.55 mg / L, the temperature of the antirust solution is 21 °C, and the pH is below 3.5. Subsequently, the treated copper foil is curled and then heat-treated at 65 °C for 24 h to obtain the electrolytic copper foil based on the double electrolytic cell.

[0043] The thickness of the electrolytic copper foil prepared in this example is 4 μm, where the thickness of the base layer is 3 μm and the thickness of the surface layer is 1 μm.

[0044] Example 2 Preparation method of electrolytic copper foil based on double electrolytic cells, specifically as follows: Step 1: Add the first electrolyte into the first electrolytic cell. The copper ion concentration in the first electrolyte is 85 g / L, and the sulfate ion concentration is 105 g / L; Stress reliever (additive A): N, N-dimethylthiourea, concentration is 0.5 g / L; Conductive aid (additive B): sodium chloride, concentration is 15.0 g / L; Grain growth regulator (additive C): 2-butyne-1,4-diol, concentration is 0.1 g / L; The temperature of the first electrolyte is 53 °C, and the pH value of the first electrolyte is below 1.0; Add the second electrolyte into the second electrolytic cell; the copper ion concentration in the second electrolyte is 42 g / L, and the sulfate ion concentration is 77 g / L.

[0045] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration is 0.5 g / L; Corrosion inhibitor (additive E): polyethylene glycol, concentration is 1.5 g / L; Brightening agent (additive F): 3-mercapto-1-propanesulfonic acid, concentration is 0.02 g / L; Surfactant (additive G): sodium dodecyl sulfate, concentration is 0.1 g / L; 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.

[0046] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller in the first electrolytic cell, with a current density of 40 A / dm 2 , to form a base layer on the surface of the rotating cathode roller; subsequently, the base layer is moved into 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, with a second current density of 17.6 A / dm 2 , to form a surface layer, and a double-layer electroplated electrolytic copper foil is obtained; Step 3. Move the double-layer electroplated electrolytic copper foil through a roll-to-roll process to the Cr rust inhibitor solution for rust prevention treatment. Among them, the chromium concentration is strictly controlled at 0.45 mg / L, the temperature of the rust inhibitor solution is 22 °C, and the pH is below 3.5. Subsequently, the treated copper foil is curled and then heat-treated at 65 °C for 24 h to obtain the electrolytic copper foil based on the double electrolytic cell.

[0047] The thickness of the electrolytic copper foil prepared in this example is 5 μm, among which the thickness of the base layer is 4 μm and the thickness of the surface layer is 1 μm.

[0048] Example 3 Preparation method of electrolytic copper foil based on double electrolytic cells is as follows: Step 1. Add the first electrolyte into the first electrolytic cell. The concentration of copper ions in the first electrolyte is 90 g / L, and the concentration of sulfate ions is 110 g / L. Stress reliever (additive A): N, N-dimethylthiourea, with a concentration of 0.2 g / L; Conductive aid (additive B): sodium chloride, with a concentration of 20.0 g / L; Grain growth regulator (additive C): 2-butyne-1,4-diol, with a concentration of 0.2 g / L; The temperature of the first electrolyte is 55 °C, and the pH value of the first electrolyte is below 1.0; Add the second electrolyte into the second electrolytic cell; the concentration of copper ions in the second electrolyte is 45 g / L, and the concentration of sulfate ions is 80 g / L.

[0049] Leveling agent (additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, with a concentration of 1.0 g / L Corrosion inhibitor (additive E): polyethylene glycol, with a concentration of 3.0 g / L, Brightening agent (additive F): 3-mercapto-1-propanesulfonic acid, with a concentration of 0.05 g / L; Surfactant (additive G): sodium dodecyl sulfate, with a concentration of 0.05 g / L; 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.

[0050] Step 2. Apply a first current between the first fixed anode plate and the rotating cathode roller in the first electrolytic cell. The first current density is 50 A / dm 2 , to form a base layer on the surface of the rotating cathode roller; then the base layer is moved into the second electrolytic cell through a roll-to-roll process, and a second current is applied between the second fixed anode plate and the plating roller. The second current density is 17.6 A / dm 2 , to form a surface layer and obtain a double-layer electroplated electrolytic copper foil; Step 3. Move the double-layer electroplated electrolytic copper foil through the roll-to-roll process to the Cr antirust solution for antirust treatment. Among them, the chromium concentration is strictly controlled at 0.6 mg / L, the temperature of the antirust solution is 18 °C, and the pH is below 3.5. Then, the treated copper foil is curled and heat-treated at 65 °C for 24 h to obtain the electrolytic copper foil based on the double electrolytic cell.

[0051] The thickness of the electrolytic copper foil prepared in this example is 6 μm, where the thickness of the base layer is 5 μm and the thickness of the surface layer is 1 μm.

[0052] Example 4 Preparation method of electrolytic copper foil based on double electrolytic cells, which is specifically as follows: Step 1: Add the first electrolyte into the first electrolytic cell. The concentration of copper ions in the first electrolyte is 85 g / L, and the concentration of sulfate ions is 105 g / L; Stress reliever (additive A): N,N-dimethylthiourea, with a concentration of 0.3 g / L; Conductive aid (additive B): Sodium chloride, with a concentration of 15.0 g / L; Grain growth regulator (additive C): 2-butyne-1,4-diol, with a concentration of 0.15 g / L; The temperature of the first electrolyte is 52 °C, and the pH value of the first electrolyte is below 1.0; Add the second electrolyte into the second electrolytic cell; the concentration of copper ions in the second electrolyte is 44 g / L, and the concentration of sulfate ions is 75 g / L.

[0053] Leveling agent (additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, with a concentration of 0.3 g / L; Corrosion inhibitor (additive E): Polyethylene glycol, with a concentration of 1.0 g / L; Brightening agent (additive F): 3-mercapto-1-propanesulfonic acid, with a concentration of 0.015 g / L; Surfactant (additive G): Sodium dodecyl sulfate, with a concentration of 0.05 g / L; 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.

[0054] Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller in the first electrolytic cell. The first current density is 35 A / dm 2 , and a base layer is formed on the surface of the rotating cathode roller; subsequently, the base layer is moved into 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 17.6 A / dm 2 , and a surface layer is formed to obtain a double-layer electroplated electrolytic copper foil; Step 3. The specific process and method are the same as those in Example 1.

[0055] The thickness of the electrolytic copper foil prepared in this example is 5 μm, where the thickness of the base layer is 4 μm and the thickness of the surface layer is 1 μm.

[0056] Example 5 Preparation method of electrolytic copper foil based on double electrolytic cells, which is specifically as follows: Step 1: Add the first electrolyte into the first electrolytic cell. The concentration of copper ions in the first electrolyte is 82 g / L, and the concentration of sulfate ions is 102 g / L; Stress reliever (Additive A): N,N-dimethylthiourea, concentration 0.4 g / L; Conductive aid (Additive B): Sodium chloride, concentration 11.0 g / L; Grain growth regulator (Additive C): 2-Butyne-1,4-diol, concentration 0.15 g / L; The temperature of the first electrolyte is 51 °C, and the pH value of the first electrolyte is below 1.0; Add the second electrolyte to the second electrolytic cell; the concentration of copper ions in the second electrolyte is 41 g / L and the concentration of sulfate ions is 76 g / L.

[0057] Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.2 g / L Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 0.8 g / L, Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.012 g / L; Surfactant (Additive G): Sodium dodecyl sulfate, concentration 0.01 g / L; 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.

[0058] Step 2. The specific process and method are the same as those in Example 1; Step 3. The specific process and method are the same as those in Example 1.

[0059] The electrolytic copper foil prepared in this example has a thickness of 4 μm, where the thickness of the base layer is 3 μm and the thickness of the surface layer is 1 μm.

[0060] Example 6 A method for preparing an electrolytic copper foil based on a dual electrolytic cell is as follows: Step 1. Add the first electrolyte to the first electrolytic cell, where the concentration of copper ions in the first electrolyte is 86 g / L and the concentration of sulfate ions is 110 g / L; Stress reliever (Additive A): N,N-dimethylthiourea, concentration 0.5 g / L; Conductive aid (Additive B): Sodium chloride, concentration 10.0 g / L; Grain growth regulator (Additive C): 2-Butyne-1,4-diol, concentration 0.01 g / L; The temperature of the first electrolyte is 52 °C, and the pH value of the first electrolyte is below 1.0; Add the second electrolyte to the second electrolytic cell; the concentration of copper ions in the second electrolyte is 43 g / L and the concentration of sulfate ions is 76 g / L.

[0061] Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.7 g / L; Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 2.5 g / L; Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.04 g / L; Surfactant (Additive G): Sodium dodecyl sulfate, concentration 0.06 g / L; 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.

[0062] Step 2. The specific process and method are the same as those in Example 1; Step 3. The specific process and method are the same as those in Example 1.

[0063] The electrolytic copper foil prepared in this example has a thickness of 4 μm, of which the thickness of the base layer is 3 μm and the thickness of the surface layer is 1 μm.

[0064] Comparative Example 1 The preparation method of the electrolytic copper foil in this comparative example is the same as that in Example 1. The difference from Example 1 is that in this comparative example, the base layer and the surface layer are not separated, and an electrolytic copper foil with a total thickness of 4 μm is deposited and prepared in a single electrolytic cell. This electrolytic cell consists of a cathode roller and a fixed anode plate. Although the electrolyte and additive composition are kept the same as those in Example 1, the current density is increased to meet the requirement of a total thickness of 4 μm. The specific process parameters of the electrolyte are: copper ion concentration 80 g / L, sulfate ion concentration 100 g / L, electrolyte temperature 50°C, current density 40 A / dm 2 .

[0065] The additives in the electrolyte are specifically as follows: Stress reliever (Additive A): N,N-Dimethylthiourea, concentration 0.05 g / L; Conductive aid (Additive B): Sodium chloride, concentration 10.0 g / L; Grain growth regulator (Additive C): 2-Butyne-1,4-diol, concentration 0.01 g / L; Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.1 g / L Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 0.5 g / L, Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.01 g / L; Surfactant (Additive G): Sodium dodecyl sulfate, concentration 0.01 g / L.

[0066] The rust prevention treatment process and the heat treatment process are both the same as those in Example 1.

[0067] Comparative Example 2 The preparation method of the electrolytic copper foil in this comparative example is the same as that in Example 2. The difference from Example 2 is that in this comparative example, the base layer and the surface layer were not separated, and an electrolytic copper foil with a total thickness of 5 μm was deposited and prepared in a single electrolytic cell. The electrolytic cell consists of a cathode roll and a fixed anode plate. Although the electrolyte and additive composition were kept the same as in Example 1, the current density was increased to meet the requirement of a total thickness of 5 μm. The specific process parameters of the electrolyte were: copper ion concentration 85 g / L, sulfate ion concentration 105 g / L, electrolyte temperature 53 °C, and current density 50 A / dm 2 .

[0068] The specific additives in the electrolyte are as follows: Stress reliever (Additive A): N,N-dimethylthiourea, concentration 0.5 g / L; Conductive aid (Additive B): sodium chloride, concentration 15.0 g / L; Grain growth regulator (Additive C): 2-butyne-1,4-diol, concentration 0.1 g / L; Leveling agent (Additive D): sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.5 g / L; Corrosion inhibitor (Additive E): polyethylene glycol, concentration 1.5 g / L; Brightening agent (Additive F): 3-mercapto-1-propanesulfonic acid, concentration 0.02 g / L; Surfactant (Additive G): sodium dodecyl sulfate, concentration 0.1 g / L; The rust prevention treatment process and the heat treatment process are both the same as in Example 2.

[0069] Comparative Example 3 The preparation method of the electrolytic copper foil in this comparative example is the same as that in Example 3. The difference from Example 3 is that in this comparative example, the base layer and the surface layer were not separated, and an electrolytic copper foil with a total thickness of 6 μm was deposited and prepared in a single electrolytic cell. The electrolytic cell consists of a cathode roll and a fixed anode plate. Although the electrolyte and additive composition were kept the same as in Example 1, the current density was increased to meet the requirement of a total thickness of 6 μm. The specific process parameters of the electrolyte were: copper ion concentration 90 g / L, sulfate ion concentration 110 g / L, electrolyte temperature 55 °C, and current density 60 A / dm 2 .

[0070] The specific additives in the electrolyte are as follows: Stress reliever (Additive A): N,N-dimethylthiourea, concentration 0.2 g / L; Conductive aid (Additive B): sodium chloride, concentration 20.0 g / L; Grain growth regulator (Additive C): 2-Butyne-1,4-diol, concentration 0.2 g / L; Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 1.0 g / L Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 3.0 g / L, Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.05 g / L; Surfactant (Additive G): Sodium dodecyl sulfate, concentration 0.05 g / L; The rust prevention treatment process and the heat treatment process are the same as those in Example 3.

[0071] Comparative Example 4 The preparation method of the electrolytic copper foil in this comparative example is the same as that in Example 4. In this comparative example, the base layer and the surface layer were not separated, and an electrolytic copper foil with a total thickness of 5 μm was deposited and prepared in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. To meet the requirement of a total thickness of 5 μm, the current density was increased. The specific process parameters of the electrolyte are: copper ion concentration 85 g / L, sulfate ion concentration 105 g / L, electrolyte temperature 52 °C, current density 50 A / dm 2 。

[0072] The additives in the electrolyte are specifically as follows: Conductive aid (Additive B): Sodium chloride, concentration 15.0 g / L; Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.3 g / L; Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 1.0 g / L; Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.015 g / L; The rust prevention treatment process and the heat treatment process are the same as those in Example 4.

[0073] Comparative Example 5 The preparation method of the electrolytic copper foil in this comparative example is the same as that in Example 5. The difference from Example 5 is that: in this comparative example, the base layer and the surface layer were not separated, and an electrolytic copper foil with a total thickness of 4 μm was deposited and prepared in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. To meet the requirement of a total thickness of 4 μm, the current density was increased. The specific process parameters of the electrolyte are: copper ion concentration 82 g / L, sulfate ion concentration 102 g / L, electrolyte temperature 51 °C, current density 40 A / dm 2 。

[0074] The additives in the electrolyte are specifically as follows: Conductive aid (Additive B): Sodium chloride, concentration 11.0 g / L; Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.2 g / L Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 0.8 g / L, Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.012 g / L; The rust prevention treatment process and the heat treatment process are the same as those in Example 2.

[0075] Comparative Example 6 The preparation method of the electrolytic copper foil in this comparative example is the same as that in Example 6. The difference from Example 6 is that in this comparative example, the base layer and the surface layer were not separated, and an electrolytic copper foil with a total thickness of 4 μm was deposited and prepared in a single electrolytic cell. The electrolytic cell consists of a cathode roller and a fixed anode plate. To meet the requirement of a total thickness of 4 μm, the current density was increased. The specific process parameters of the electrolyte are: copper ion concentration 86 g / L, sulfate ion concentration 110 g / L, electrolyte temperature 52 °C, current density 40 A / dm 2 .

[0076] The additives in the electrolyte are specifically as follows: Conductive aid (Additive B): Sodium chloride, concentration 10.0 g / L; Leveling agent (Additive D): Sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, concentration 0.7 g / L; Corrosion inhibitor (Additive E): Polyethylene glycol, concentration 2.5 g / L; Brightening agent (Additive F): 3-Mercapto-1-propanesulfonic acid, concentration 0.04 g / L; The rust prevention treatment process and the heat treatment process are the same as those in Example 6.

[0077] The concentrations of the additives used in Examples 1-6 and Comparative Examples 1-6 of the present invention are shown in Table 1.

[0078] Table 1 Concentrations of additives used in Examples 1-6 and Comparative Examples 1-6

[0079] The performance indexes of the electrolytic copper foils prepared in Examples 1-6 and Comparative Examples 1-6 were tested respectively, and the results are shown in Table 2.

[0080] Table 2 Performance indexes of the electrolytic copper foils prepared in Examples 1-6 and Comparative Examples 1-6

[0081] As can be seen from the data in Table 1 and Table 2: In the manufacture of electrolytic copper foil, by constructing the electrolysis system into a double electrolytic cell structure and independently applying optimized electrolysis conditions and additive compositions for the base layer and the surface layer respectively, it is confirmed that the quality and uniformity of the coating are significantly improved compared with the existing single electrolytic cell method. In Examples 1 to 6, a double electrolytic cell system with separation of the base layer (3 - 5 μm) and the surface layer (1 μm) was used, thereby achieving excellent physical properties of the surface layer with S surface roughness (Ra) of 0.08 - 0.12 μm, M surface roughness (Rz) of 0.55 - 0.65 μm, tensile strength of 380 - 420 MPa, elongation of 5.0 - 7.0%, and curl of 5 mm or less. In particular, for the base layer, by adding a stress reliever, a conductive aid, and a grain growth regulator at the optimal concentration under high current density and high-concentration electrolyte conditions, the structural support force and thickness uniformity are ensured; while for the surface layer, a stable layer with ultra-low roughness and high tensile strength characteristics is formed through low current density and precisely controlled additive composition. In contrast, Comparative Examples 1 to 6 were manufactured using the single electrolytic cell method, and overall electroplating was carried out under the same conditions, failing to achieve the functional separation of the base layer and the surface layer. This led to a decline in coating quality due to complex factors such as interference between additives, uneven current distribution, and abnormal deposition reactions, manifested as an increase in roughness, a decrease in tensile strength, and an increase in curl. This clearly shows that the single electrolytic cell system has structural limitations in ensuring coating quality due to its inability to achieve precise hierarchical control.

[0082] In summary, the present invention clearly separates the required characteristics of each layer through the double electrolytic cell system and applies the optimized electrolysis conditions and additive combinations for each layer, and has been proven to have more excellent performance than the prior art in all aspects such as coating accuracy, structural stability, surface characteristics, and mechanical properties. In particular, this technical configuration can meet the following demand conditions for high-end electrolytic copper foil: roughness and curl control, high-speed signal transmission stability, high-precision circuit adaptability, etc., and can provide a core process with decisive technical competitiveness in high-value-added electronic material fields such as the new generation of AI computing technology, semiconductor packaging, 6G communication, and high-frequency circuit substrates.

Claims

1. A copper foil preparation system with a dual electrolytic cell, characterized in that, It includes a first electrolytic cell and a second electrolytic cell. Both the first electrolytic cell and the second electrolytic cell include a dissolution tank, a waste liquid tank, a purified liquid tank, an electrolyte supply system, a temperature control system, a current supply system, and an additive injection system; The first electrolytic cell includes a first fixed anode plate and a rotating cathode roller. 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. The second fixed anode plate and the electroplating roller are separately arranged; A roll-to-roll transfer structure is adopted between the first electrolytic cell and the second electrolytic cell. A cleaning roller and a hot air dryer are arranged between the first electrolytic cell and the second electrolytic cell; It also includes a PLC control system and a real-time sensor. The PLC control system and the real-time sensor are electrically connected to the first electrolytic cell and the second electrolytic cell respectively.

2. The copper foil preparation system with a dual electrolytic cell according to claim 1, wherein, The diameter of the rotating cathode roller in the first electrolytic cell is 2500 - 3000 mm, and the diameter of the electroplating roller in the second electrolytic cell is 1500 - 1700 mm.

3. Preparation method of electrolytic copper foil based on a dual electrolytic cell, characterized in that, The copper foil preparation system with a dual electrolytic cell as described in any one of claims 1 - 2 is used as follows: Step 1: Add a first electrolyte to the first electrolytic cell and add a second electrolyte to the second electrolytic cell; Step 2: Apply a first current between the first fixed anode plate and the rotating cathode roller in the first electrolytic cell to form a base layer on the surface of the rotating cathode roller; Subsequently, this base layer is moved into 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, obtaining a double-layer electroplated electrolytic copper foil; Step 3. Move the double-layer electroplated electrolytic copper foil through a roll-to-roll process to a Cr rust inhibitor solution for rust prevention treatment, then curl the treated copper foil, and then heat-treat it at 65 °C for 24 h to obtain an electrolytic copper foil based on a dual electrolytic cell.

4. The method for preparing electrolytic copper foil based on a dual electrolytic cell according to claim 3, characterized in that, The first electrolyte includes copper ions, sulfate ions, and a first additive. 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 includes copper ions, sulfate ions, and a second additive. The copper ion concentration in the second electrolyte is 40 - 45 g / L, and the sulfate ion concentration is 75 - 80 g / L; 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.

5. The preparation method of the electrolytic copper foil based on a dual electrolytic cell according to claim 4, wherein, The first additive includes a stress reliever, a conductivity promoter, and a grain growth regulator; The stress reliever is N,N-dimethylthiourea, and its concentration is 0.05 - 0.5 g / L; The conductivity promoter is sodium chloride, and its concentration is 10.0 - 20.0 g / L; The grain growth regulator is 2-butyne-1,4-diol, and its concentration is 0.01 - 0.2 g / L.

6. The method for preparing electrolytic copper foil based on a dual electrolytic cell according to claim 4, wherein, The second additive includes a leveling agent, a corrosion inhibitor, a brightening agent, and a surfactant; The leveling agent is sodium 3-(5-mercapto-1-tetrazolyl)benzenesulfonate, and its concentration is 0.1 - 1.0 g / L; The corrosion inhibitor is polyethylene glycol, and its concentration is 0.5 - 3.0 g / L; The brightening agent is 3-mercapto-1-propanesulfonic acid with a concentration of 0.01 - 0.05 g / L; The surfactant is sodium dodecyl sulfate with a concentration of 0.01 - 0.1 g / L.

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

8. The preparation method of electrolytic copper foil based on a dual electrolytic cell according to claim 3, characterized in that, In step 3, the Cr antirust solution includes chromium ions and glucose. The concentration of the chromium ions is 0.45 - 0.60 mg / L, the concentration of the glucose is 7.0 g / L, the temperature of the antirust solution is 18 - 22 °C, and the pH is below 3.

5.

9. The electrolytic copper foil prepared by the method for preparing an electrolytic copper foil based on a dual electrolytic cell according to claim 3, wherein 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 - 6 μm, the thickness of the base layer is 3 - 5 μm, and the thickness of the surface layer is less than or equal to 1 μm.

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