Method for improving the adhesion of electrolytic copper foil to a substrate at low roughness

Abstract

This invention discloses a method for improving the adhesion between electrolytic copper foil and substrate under low roughness, and the electrolytic copper foil itself, comprising: 1) acid washing of a 9-35μm raw foil with a smooth surface; 2) selectively ablation of the protrusions >100nm on the surface of the acid-washed raw foil with a picosecond laser, so that Ra≤0.1μm; 3) depositing a dense copper layer of 0.1-0.4μm to fill the micro-pits; 4) roughening in a roughening solution containing copper ions, sulfuric acid, sodium tungstate and sodium molybdate; 5) curing in a curing solution containing copper ions, sulfuric acid, MPS, HEC, PEG and hydrolyzed collagen; 6) sequential heat resistance treatment and passivation treatment; 7) spraying an organosilane coupling agent; 8) drying at 130-140℃ for 5-10s and then winding at 4-6m / min. This invention avoids the formation of high-roughness structures through laser planarization, strengthens the substrate with a dense copper layer to improve the uniformity of copper nodules, and the final product has a bonding surface Rz≤1.5μm, Ra≤0.2μm, peel strength≥0.7N / mm, and no copper powder falls off during bonding, making it suitable for high-precision copper foil preparation.

Description

Technical Field

[0001] This invention belongs to the field of copper foil technology, specifically relating to a method for improving the bonding force between electrolytic copper foil and substrate under low roughness. Background Technology

[0002] Electrolytic copper foil, as the core conductive material of copper clad laminate (CCL) and printed circuit board (PCB), directly undertakes the key functions of signal transmission and power delivery in electronic devices. In high-frequency and high-speed signal transmission scenarios, there is a significant "skin effect" in signal transmission. In order to avoid attenuation and distortion during signal transmission, electrolytic copper foil for high-frequency and high-speed applications needs to have extremely low surface roughness. Currently, the market demand for electrolytic copper foil with a roughness Rz of less than 1.5μm is particularly prominent.

[0003] However, the bonding performance between electrolytic copper foil and the resin substrate used in copper-clad laminates depends on the microstructure of the copper foil surface. In traditional techniques, forming copper nodules (such as micron-sized protrusions like nodules or dendrites) on the copper foil surface and utilizing the mechanical anchoring effect between the nodules and the resin can effectively improve the bonding strength. The more numerous and larger the nodules, the stronger the mechanical anchoring effect generally is. Therefore, high-frequency, high-speed electrolytic copper foil faces a core technical contradiction between "low roughness" and "high peel strength." To reconcile the aforementioned contradictions, existing technologies generally employ a two-step preparation process. This process modifies the surface of electrolytic copper foil (green foil) to achieve high peel strength while maintaining low roughness. The core steps of this process include: first, removing the oxide layer from the surface of the green foil through acid pickling; then, roughening treatment is performed, forming regular, dense, uniform, and firmly bonded micron-sized copper nodules on the surface of the green foil through electrolytic deposition. These nodules increase the specific surface area, thereby enhancing the mechanical bonding with the resin; the roughened copper foil is then cured to strengthen the bond between the nodules and the substrate; subsequently, functionalized anti-oxidation layers are prepared to improve corrosion resistance; finally, silane treatment is performed, forming -Si-O- chemical bonds on the surface of the copper foil through silane molecules, further enhancing the chemical bonding with the resin substrate. Although the existing two-step process alleviates the contradiction between low roughness and high peel strength to some extent, there are still key technical defects in practical applications. Specifically, the problem lies in the insufficient synergy between the two key steps of pickling and roughening: On the one hand, during the pickling process, the surface of the green foil inevitably has micro-pits, and the pickling treatment will cause these micro-pits to expand significantly, directly increasing the surface roughness Rz of the green foil and destroying the initial substrate conditions of low roughness; on the other hand, in the subsequent roughening electrolytic deposition process, due to the significant tip effect at the edge of the micro-pit, copper ions will preferentially deposit at the edge of the micro-pit to form copper buds, resulting in abnormal growth of the protruding structure at the edge of the micro-pit, further aggravating the surface roughness of the copper foil, making it difficult to control the roughness of the final product to meet the high-frequency application requirements of less than 1.5μm, and seriously deteriorating its high-frequency signal transmission performance. Meanwhile, due to poor deposition conditions at the bottom of the micro-pits, the bonding force between the copper nodules formed and the green foil substrate is weak. During the copper clad laminate lamination process, these poorly bonded copper nodules are prone to detachment, which not only reduces the actual bonding strength between the copper foil and the resin, but the detached copper nodule particles may also cause quality hazards such as short circuits, greatly affecting the product reliability of high-frequency CCL / PCB. Summary of the Invention To address the shortcomings of existing technologies, this invention proposes a method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions. By optimizing the surface pretreatment and roughening process, a high peel strength of ≥0.7N / mm is achieved under the premise of strictly controlling the surface roughness of the copper foil (Rz≤1.5μm, Ra≤0.2μm), and the risk of copper nodules falling off is completely eliminated, meeting the requirements of high-frequency and high-speed electronic circuits.

[0004] In a first aspect, the present invention proposes a method for improving the adhesion between electrolytic copper foil and a substrate under low roughness conditions, comprising: Step 1, pickling of raw foil: Select raw foil with a thickness of 9-35μm, and use the smooth side of the raw foil as the surface for rough curing treatment, and pickle it; Step 2, Laser leveling pretreatment: Selectively ablate the raised areas on the surface of the raw foil after acid pickling, wherein the raised areas are areas with a raised height > 100 nm, so that the surface roughness Ra ≤ 0.1 μm; Step 3: Deposit a dense copper layer on the smooth surface of the laser-ablated copper foil to fill the micro-pits on the smooth surface of the raw foil after acid washing, homogenize the smooth surface of the raw foil and form a dense copper layer. Step 4: Roughen in a roughening tank containing a roughening solution; the roughening solution contains 10-13 g / L copper ions, 110-130 g / L sulfuric acid, 10-20 mg / L sodium tungstate, and 10-20 mg / L sodium molybdate. Step 5: Curing is carried out in a curing tank containing a curing solution; the curing solution contains 45-50 g / L copper ions, 90-100 g / L sulfuric acid, 4.0-9.0 mg / L sodium 3-mercapto-1-propanesulfonate (MPS), 4.0-9.0 mg / L hydroxyethyl cellulose (HEC), 4.0-9.0 mg / L polyethylene glycol (PEG), and 3.0-7.0 mg / L hydrolyzed collagen. Step 6, Anti-oxidation treatment: This includes heat resistance treatment and passivation treatment, which are carried out in treatment tanks containing heat resistance treatment solution and passivation treatment solution, respectively. Step 7, Silanization treatment: Spraying organosilane coupling agent; Step 8: Drying and winding to obtain electrolytic copper foil; the thickness of the electrolytic copper foil is 9-35μm, the surface roughness of the pressed surface after smoothing is Rz≤1.5μm, Ra≤0.2μm, the peel strength is ≥0.7N / mm, and no copper powder falls off after pressing; wherein, the drying temperature is 130-140℃, the time is 5-10s, and the winding speed is 4-6m / min.

[0005] This application utilizes laser removal to remove high points caused by acid pickling, reducing the formation of high-roughness copper nodules due to the tip effect during roughening and preventing the formation of high-roughness copper lumps during curing. Furthermore, the pre-plating layer fills micro-pits and strengthens the substrate, improving the uniformity of copper nodules generated by coarse curing and providing a uniform and strong substrate for fine copper nodules, thus reducing the risk of copper nodule detachment.

[0006] Preferably, the pickling solution in step 1 is a sulfuric acid aqueous solution of 140-150 g / L, and the pickling temperature is 34-40℃.

[0007] Preferably, the laser smoothing pretreatment in step 2 is performed using a picosecond laser with the following parameters: laser wavelength 532nm, pulse energy 0.5-5mJ, and scanning speed 1-10m / s.

[0008] Preferably, the deposition solution for depositing the dense copper layer in step 3 contains 48-52 g / L of copper ions, 90-100 g / L of sulfuric acid, and 24-48 mg / L of deposition additives. The deposition additives include 8.0-16.0 mg / L of sodium 3-mercapto-1-propanesulfonate (MPS), 10.0-20.0 mg / L of polyethylene glycol (PEG), and 6.0-12.0 mg / L of polyethyleneimine. The molecular weight of the polyethylene glycol is 2000-3000 Da, and the molecular weight of the polyethyleneimine is 1000-2000 Da.

[0009] Preferably, in step 3, the deposition of the dense copper layer is carried out at a deposition temperature of 40-42℃ and a current density of 8-12A / dm2; a dense copper layer with a thickness of 0.1-0.4μm is deposited.

[0010] Preferably, the roughening conditions in step 4 are: temperature 20-30℃, current density 12-15A / dm². 2 .

[0011] Preferably, the curing conditions in step 5 are: temperature 40-42℃, current density 8-12A / dm³. 2 .

[0012] Preferably, the heat-resistant treatment solution in step 6 contains 1.1-2.6 g / L of zinc ions, 2.3-5.4 g / L of nickel ions, and... 70-80 g / L, the pH of the heat-resistant treatment solution is 10-12; The conditions for heat resistance treatment are: temperature 25-35℃, current density 2.5-3.5A / dm³. 2 ; The passivation solution in step 6 contains 2.0-2.5 g / L and K4P2O7 90-100 g / L, wherein the pH of the passivation treatment solution is 11-12; The passivation conditions are: temperature 30-40℃, current density 2.4-2.8 A / dm³. 2 .

[0013] Preferably, the organosilicon coupling agent sprayed in step 7 is at least one of KH550, KH560 and KH570, the concentration of the organosilicon coupling agent is 1.0-1.5 g / L, the pH is 9-12, and the spraying temperature is 25-35℃.

[0014] Secondly, this application also proposes an electrolytic copper foil, which is prepared by a method for improving the adhesion between the electrolytic copper foil and the substrate under low roughness as described in the first aspect.

[0015] This application innovatively designs a process route of "raw foil pickling → laser leveling pretreatment → deposition of dense copper layer → roughening → curing → anti-oxidation treatment → silane treatment". Relying on two core technologies, laser leveling and pre-plating filling, it specifically solves key problems in traditional processes such as uncontrolled roughness after pickling and weak copper nodule bonding that is easy to fall off. Significant breakthroughs have been achieved in optimizing the performance of electrolytic copper foil, improving production stability and expanding application adaptability.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This application utilizes laser planarization pretreatment to precisely remove surface high points generated after acid pickling, breaking the formation chain of "high point - tip effect - high roughness copper nodule" at its source and avoiding uncontrolled roughness caused by abnormal growth of local protruding structures. In practical applications, the laser pretreatment can achieve micron-level precision in removing high points, improving the uniformity of the microstructure of the copper foil surface after acid pickling by more than 40%, and significantly reducing intra-batch and inter-batch variability in roughness.

[0017] By combining the elimination of high points through laser leveling with the filling effect of a dense copper layer on micro-pits, a high-quality substrate with "low undulation and high flatness" is formed on the copper foil surface before roughening. Subsequent roughening stages allow for the uniform growth of fine copper nodules, avoiding the uneven distribution and localized overgrowth problems caused by uneven substrates in traditional processes. Testing shows that the electrolytic copper foil prepared using this process can have a surface roughness Rz stably controlled below 1.5 μm, Ra ≤ 0.2 μm, and a roughness variation coefficient reduced to less than 5%, far superior to the 10%-15% variation level of traditional processes. This fully meets the stringent low-roughness requirements for signal transmission in 5G high-frequency, high-speed scenarios.

[0018] Furthermore, this application utilizes a dense copper layer (pre-plating layer) to precisely fill the low points of micro-pits expanded by acid pickling, forming a continuous and dense metal bonding interface on the copper foil substrate surface. This effectively strengthens the metallurgical bond between the substrate and the subsequently coarsened copper nodules. The bonding strength between the pre-plating layer and the substrate can reach over 150 MPa, providing a uniform and robust adhesion carrier for the growth of fine copper nodules.

[0019] In summary, the electrolytic copper foil prepared by this invention not only meets the requirements of high-frequency CCL / PCB in high-frequency communication equipment such as 5G base stations and millimeter-wave radar, but is also suitable for high-end applications with extremely high reliability requirements, such as vehicle-mounted radar in new energy vehicles and precision electronics in aerospace. Compared with traditional products, the electrolytic copper foil of this application has significant improvements in signal transmission attenuation rate (attenuation rate reduced by 15%-20% at 10GHz) and environmental reliability, providing key material support for the performance upgrade of high-end electronic circuits and effectively expanding the application boundaries of electrolytic copper foil. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating a method for improving the adhesion between electrolytic copper foil and substrate under low roughness, as shown in an embodiment of the present invention.

[0021] Figure 2 This is a structural diagram of the processing procedure shown in an embodiment of the present invention.

[0022] Figure 3 This is a SEM image of the glossy surface of a foil in existing technology.

[0023] Figure 4This is a SEM image of the glossy surface of the green foil shown in an embodiment of the present invention.

[0024] Figure 5 This is a SEM image of the foil after surface treatment in the existing technology.

[0025] Figure 6 This is a SEM image of the raw foil after surface treatment, as shown in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1: As Figure 1-2 As shown, this application proposes a method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions, comprising: Step 1: Pickling of raw foil; It should be noted that in this embodiment, a green foil with a thickness of 9-35 μm is selected, with a purity of 99.99%, an initial surface roughness Ra of 0.15 μm, and a Rz of 1.5 μm.

[0028] The surface of the raw foil is smooth with low roughness, therefore it requires pickling to improve its surface adhesion. Specifically, the smooth surface of the raw foil is used as the roughing treatment surface for pickling. The pickling solution is a 140-150 g / L sulfuric acid aqueous solution. The sulfuric acid aqueous solution can effectively remove the oxide layer and impurities on the surface of the raw foil, increasing the surface roughness to improve the adhesion between the electrolytic copper foil and the substrate. The pickling temperature is 34-40℃. It should be noted that excessively high temperatures may damage the surface of the raw foil, while excessively low temperatures may result in unsatisfactory pickling results. This temperature range ensures the optimal balance of pickling effects.

[0029] Immerse the raw foil in the pickling solution for approximately 10-15 minutes. The immersion time can be adjusted as needed to ensure uniformity and effectiveness of the surface treatment. During pickling, maintain gentle stirring to accelerate the reaction and ensure uniform surface treatment. Preferably, after pickling, thoroughly rinse the raw foil surface with deionized water to remove residual acid and prevent corrosion in subsequent processes. After rinsing, place the raw foil in a drying apparatus to ensure no moisture remains on the surface. Through the pickling process described above, a micro-rough structure is formed on the surface of the raw foil, providing better surface properties for the subsequent bonding of electrolytic copper foil to the substrate.

[0030] Step 2: Laser leveling pretreatment; During the laser leveling pretreatment, the raised areas on the surface of the acid-washed green foil are selectively ablated, and the height of the raised areas is greater than 100 nm. Through laser treatment, the raised parts of the surface are ablated and removed, thereby leveling the surface, reducing its roughness, and making the surface roughness Ra ≤ 0.1 μm; In this embodiment, the laser planarization pretreatment in step 2 uses a picosecond laser. Picosecond lasers have extremely short pulse widths, allowing for precise control of the ablation depth and range, thus achieving micron-level fine surface treatment and avoiding excessive thermal impact or damage to the substrate. Preferably, the processing parameters are: laser wavelength 532nm, pulse energy 0.5-5mJ, and scanning speed 1-10m / s. During the laser planarization pretreatment, an automated control system precisely adjusts the laser wavelength, pulse energy, and scanning speed to ensure consistent treatment results for each piece of green foil that meet design requirements.

[0031] After laser planarization pretreatment, in order to further improve the bonding force between electrolytic copper foil and substrate and homogenize the surface structure, a dense copper layer is deposited to fill the micro-pits on the bright surface of the raw foil after pickling, and a dense copper layer is formed on the bright surface to further optimize the surface quality.

[0032] Step 3: Deposit a dense copper layer; A dense copper layer is deposited on the smooth surface of the laser-ablated copper foil to fill the micro-pits on the smooth surface of the raw foil after acid washing, thereby homogenizing the smooth surface of the raw foil and forming a dense copper layer. In this embodiment, an electrochemical deposition method is used to uniformly deposit a copper layer onto the surface of the copper foil. A deposition temperature of 40-42℃ is selected to deposit a dense copper layer, avoiding excessively high temperatures that could cause overly rapid or uneven deposition, while excessively low temperatures could result in a slow deposition rate. A current density of 8-12 A / dm² is used to deposit a dense copper layer 0.1-0.4 μm thick. This thickness effectively fills the micro-pits on the surface of the raw foil after pickling, while maintaining the flatness and density of the copper layer, ensuring the stability and reliability of the final product during use.

[0033] During the deposition process, the copper foil undergoes a reduction reaction with copper ions in the electrolyte, gradually forming a dense copper layer. After deposition, the copper foil undergoes appropriate post-treatment, such as washing and drying, to remove any residual chemicals that may have remained from the deposition process and to further ensure the stability and adhesion of the copper layer.

[0034] Preferably, the deposition solution for depositing the dense copper layer in step 3 contains 48-52 g / L of copper ions, 90-100 g / L of sulfuric acid, and 24-48 mg / L of deposition additives. The deposition additives include 8.0-16.0 mg / L of sodium 3-mercapto-1-propanesulfonate (MPS), 10.0-20.0 mg / L of polyethylene glycol (PEG), and 6.0-12.0 mg / L of polyethyleneimine. The molecular weight of the polyethylene glycol is 2000-3000 Da, and the molecular weight of the polyethyleneimine is 1000-2000 Da.

[0035] Step 4: Coarsening; In this embodiment, a roughening tank containing a roughening solution is used to roughen the copper foil with a deposited dense copper layer. The roughening process can effectively improve the surface roughness and texture of the copper foil, thereby improving its adhesion in subsequent coating processes and its performance as a substrate.

[0036] The roughening solution contains 10-13 g / L copper ions, 110-130 g / L sulfuric acid, 10-20 mg / L sodium tungstate, and 10-20 mg / L sodium molybdate. Preferably, the roughening conditions in step 4 are: temperature 20-30℃, current density 12-15 A / dm³. 2 .

[0037] Copper ions can participate in the roughening reaction, dissolving part of the copper layer on the copper surface and helping to form a rough surface.

[0038] Sulfuric acid, as the main acidic medium, plays a strong corrosive role in the process of dissolving copper, helping to remove oxides and uneven areas on the copper surface.

[0039] Sodium tungstate and sodium molybdate: These two compounds, as additives, can effectively inhibit excessive corrosion of copper, control the degree of roughening, and ensure that the surface roughness of copper foil is moderate and uniform.

[0040] In this embodiment, the roughening process is as follows: In the roughening tank, the copper foil serves as the anode, and the roughening solution in the electrolyte is the electrolyte. By applying an external current, the copper surface undergoes chemical dissolution, forming a rough surface. The temperature, current density, and composition of the roughening solution within the roughening tank directly affect the roughening effect; therefore, precise control is required. The roughening time typically ranges from a few minutes to tens of minutes, and the specific time can be adjusted according to the initial state of the copper foil and the desired surface roughness.

[0041] After roughening, the copper foil surface will exhibit a moderate roughness, neither too rough nor too smooth. At this point, the copper foil surface has good adhesion and is suitable for subsequent coating or plating operations. The roughened copper foil can be washed with water to remove residual roughening solution and then dried.

[0042] The roughened surface of the copper foil not only improves the adhesion of subsequent coatings or platings, but also increases surface activity and enhances its overall performance. It is particularly suitable for applications requiring high adhesion and good surface uniformity, such as high-performance circuit boards and electronic components.

[0043] Step 5: Curing; Curing is performed in a curing bath containing a curing solution; by forming a stable cured layer on the surface of the copper foil, the corrosion resistance, oxidation resistance, and mechanical strength of the copper foil are improved. The cured layer not only improves the surface stability of the copper foil, but also enhances its performance in subsequent processing (such as coating, plating, etc.).

[0044] The curing solution contains 45-50 g / L copper ions, 90-100 g / L sulfuric acid, 4.0-9.0 mg / L sodium 3-mercapto-1-propanesulfonate (MPS), 4.0-9.0 mg / L hydroxyethyl cellulose (HEC), 4.0-9.0 mg / L polyethylene glycol (PEG), and 3.0-7.0 mg / L hydrolyzed collagen. It should be noted that the functions of the above-mentioned components are as follows: Copper ions: provide the necessary copper source and participate in the formation of a stable copper plating or cured layer during the curing process.

[0045] Sulfuric acid: As an acidic medium, sulfuric acid can promote the reduction of copper ions, help the solidification process, and maintain the acidic environment of the solution.

[0046] Sodium 3-mercapto-1-propanesulfonate (MPS): As a surfactant, MPS helps improve the wettability and dispersibility of the curing solution, making the curing process more uniform.

[0047] Hydroxyethyl cellulose (HEC): It acts as a thickener, increasing the viscosity of the curing solution and helping to better coat the copper foil surface.

[0048] Polyethylene glycol (PEG): As a surface treatment agent, PEG can improve the lubricity of copper foil surfaces and enhance the stability of the cured layer.

[0049] Hydrolyzed collagen: Provides a certain degree of protection and enhances the adhesion and durability of the cured layer on the copper foil surface.

[0050] During the curing process, controlling the temperature and current density of the curing solution is crucial for the curing effect on the copper foil surface. In this embodiment, the specific curing conditions are as follows: Temperature: The curing temperature is controlled at 40-42℃. This temperature range can ensure that the curing reaction proceeds smoothly without causing excessive heat damage to the copper foil.

[0051] Current density: The current density is set to 8-12A / dm². A suitable current density can ensure that the curing reaction is fully carried out and that the cured layer is uniform and dense.

[0052] In this embodiment, the curing process is controlled as follows: the curing treatment is carried out in a curing tank, with copper foil as the anode and curing solution as the electrolyte. Under the action of an external current, copper ions on the surface of the copper foil are reduced under the action of the electric field, forming a dense cured layer. Other components in the curing solution, such as MPS, HEC, PEG, and hydrolyzed collagen, work synergistically to improve the surface structure of the copper foil and enhance the adhesion and stability of the cured layer. After curing, a uniform cured layer is formed on the surface of the copper foil. This cured layer can significantly improve the corrosion resistance, oxidation resistance, and surface adhesion of the copper foil. At this point, the copper foil can undergo further processing, such as coating, plating, or other surface treatment processes.

[0053] The curing time is adjusted according to the requirements of the copper foil and the concentration of the curing solution, and generally ranges from a few minutes to tens of minutes. During the process, it is necessary to monitor the current density and temperature in real time to ensure process stability and avoid over-curing or uneven curing.

[0054] Furthermore, the main purpose of anti-oxidation treatment is to enhance the copper foil surface's resistance to external oxidation, corrosion, and thermal damage by forming a protective oxide film. This treatment effectively prevents discoloration, corrosion, or damage to the copper foil during subsequent use, ensuring its excellent electrical and mechanical properties.

[0055] Step 6: Anti-oxidation treatment Anti-oxidation treatment includes heat resistance treatment and passivation treatment, which are carried out in treatment tanks containing heat resistance treatment solution and passivation treatment solution, respectively.

[0056] Heat resistance treatment: Preferably, the heat-resistant treatment solution in step 6 contains 1.1-2.6 g / L of zinc ions, 2.3-5.4 g / L of nickel ions, and... The concentration of zinc ions and nickel ions in the heat-resistant treatment solution is 70-80 g / L, and the pH of the solution is 10-12. The role of zinc ions and nickel ions in the heat-resistant treatment solution is to form a protective film through electrolytic reaction, thereby improving the copper foil's resistance to high-temperature oxidation. Potassium pyrophosphate, on the other hand, contributes to the stability of the film.

[0057] The conditions for heat resistance treatment are: temperature 25-35℃, current density 2.5-3.5A / dm³. 2 .

[0058] Passivation treatment: The passivation solution in step 6 contains The passivation solution contains 2.0-2.5 g / L of potassium pyrophosphate and 90-100 g / L of potassium 4P2O7, with a pH of 11-12. The chromate in the passivation solution effectively forms a passivation film on the copper foil surface, preventing copper foil oxidation. Potassium pyrophosphate further enhances the stability and durability of the passivation film.

[0059] The passivation conditions are: temperature 30-40℃, current density 2.4-2.8 A / dm³. 2 .

[0060] In this embodiment, the copper foil undergoes an anti-oxidation treatment process, firstly through a heat-resistant treatment stage, where it undergoes an electrolytic reaction in a heat-resistant treatment solution within a treatment tank. Next, the copper foil enters a passivation treatment stage, where it is further processed in a passivation treatment tank. The time, temperature, and current density of each treatment step must be strictly controlled to ensure the formation of an ideal protective film on the copper foil surface. After treatment, the copper foil will exhibit significant oxidation and corrosion resistance, making it suitable for more demanding working environments.

[0061] Copper foil that has undergone heat resistance and passivation treatment possesses the following superior properties: Through passivation, the passivation film formed on the copper foil surface effectively prevents oxidation reactions, ensuring the stability of the copper foil in air. The passivation film also effectively isolates the copper foil surface from contact with external corrosive substances, preventing corrosion in acidic or alkaline environments. Heat resistance treatment enhances the copper foil's high-temperature resistance, enabling it to operate stably for extended periods in high-temperature environments.

[0062] Step 7: Silanization treatment; Silanization is mainly used to form an organosilicon protective film on the surface of materials by spraying an organosilicon coupling agent. This improves the adhesion of metal materials to coatings, resins, and other materials, and enhances their corrosion resistance, high-temperature resistance, and mechanical strength. It is particularly useful in the electronics, semiconductor, and coating industries.

[0063] Preferably, the silicone coupling agent sprayed in step 7 is at least one of KH550, KH560 and KH570; Specifically: KH550: Used to improve the adhesion between materials and organic substrates.

[0064] KH560: Used to improve the corrosion resistance of materials.

[0065] KH570: It has good adhesion to metal surfaces and is used for the adhesion of metal coatings.

[0066] The concentration of the organosilicon coupling agent is 1.0-1.5 g / L. This concentration effectively ensures the uniform distribution of the coupling agent on the metal surface, forming a stable silanized film, while avoiding uneven film formation or performance degradation due to excessive accumulation. The pH of the spraying solution is 9-12, and the spraying temperature is 25-35℃. It should be noted that excessively high or low temperatures may affect the reaction efficiency of the coupling agent and the coating quality. Therefore, controlling the spraying temperature within this range helps to achieve the best surface treatment effect.

[0067] The silanization process involves spraying an organosilane coupling agent solution uniformly onto the material surface using a sprayer or spray gun. During spraying, it is crucial to ensure the uniformity of the coupling agent solution and control the spraying time and amount to guarantee a uniform and robust silanized film. The sprayed material then needs to be dried at an appropriate temperature to promote the reaction and curing of the silane coupling agent. The drying temperature can be controlled between 60-80℃, and the drying time is approximately 30-60 minutes to ensure the stability and adhesion of the film.

[0068] Step 8: Dry and rewind to obtain electrolytic copper foil; The resulting electrolytic copper foil has a thickness of 9-35μm, which can meet the needs of different types of batteries, circuit boards and electronic devices.

[0069] After the surface of the electrolytic copper foil is smoothed, the surface roughness of the pressed surface is required to be Rz≤1.5μm and Ra≤0.2μm. The peel strength of the pressed electrolytic copper foil is ≥0.7N / mm, and no copper powder falls off after pressing. The drying temperature is 130-140℃, the time is 5-10s, and the winding speed is 4-6m / min.

[0070] Specifically, such as Figure 3 This is a SEM image of the glossy surface of a foil in existing technology. Figure 4 This is a SEM image of the glossy surface of the green foil shown in an embodiment of the present invention. Figure 5 This is a SEM image of the foil after surface treatment in the existing technology. Figure 6 This is a SEM image of the raw foil after surface treatment as shown in an embodiment of the present invention. By adopting the above-described manufacturing process, the roughness of the present application is significantly reduced compared with the prior art.

[0071] Based on the above-described method and steps for improving the adhesion between electrolytic copper foil and substrate under low roughness, further corresponding embodiments are provided for verification as follows: Option 1: Preparation of low-roughness, high-adhesion electrolytic copper foil 1. Raw material preparation: Electrolytic copper foil with a thickness of 12μm was selected (the smooth side was used as the surface for subsequent rough curing treatment), and the size was 400mm×600mm.

[0072] 2. Specific process steps: Step 1: Pickling of raw foil.

[0073] Pickling solution: 145 g / L sulfuric acid aqueous solution.

[0074] Process conditions: Temperature 36℃, immerse the raw foil completely in the pickling solution for 30 seconds, then rinse with deionized water for 20 seconds.

[0075] Objective: To remove the oxide layer and oil stains from the surface of raw foil and to activate the surface.

[0076] Step 2: Laser leveling pretreatment.

[0077] Equipment: Picosecond laser.

[0078] Processing parameters: laser wavelength 532nm, pulse energy 2mJ, scanning speed 5m / s.

[0079] Processing method: Selectively ablate areas with surface protrusion height > 100 nm.

[0080] Result: The surface roughness Ra after treatment is 0.08 μm.

[0081] Step 3: Deposit a dense copper layer.

[0082] Deposition solution composition: 50 g / L copper ions (provided by copper sulfate), 95 g / L sulfuric acid, 36 mg / L deposition additive (containing 12 mg / L MPS, 15 mg / L PEG, and 9 mg / L polyethyleneimine; PEG molecular weight 2000 Da, polyethyleneimine molecular weight 1500 Da). Process conditions: temperature 41℃, current density 10A / dm², deposition time 60 seconds.

[0083] Result: A dense copper layer with a thickness of 0.2 μm was formed, completely filling the surface micro-pits.

[0084] Step 4: Roughening process.

[0085] The roughening solution consists of: 12 g / L copper ions, 120 g / L sulfuric acid, 15 mg / L sodium tungstate, and 15 mg / L sodium molybdate.

[0086] Process conditions: temperature 25℃, current density 13A / dm², processing time 45 seconds.

[0087] Result: Uniformly distributed micron-sized rough protrusions formed on the surface.

[0088] Step 5: Curing process.

[0089] The curing solution consists of: 48 g / L copper ions, 95 g / L sulfuric acid, 6 mg / L MPS, 6 mg / L HEC, 6 mg / L PEG, and 5 mg / L hydrolyzed collagen.

[0090] Process conditions: temperature 41℃, current density 10A / dm², processing time 50 seconds.

[0091] Result: A dense copper nodule structure was formed on the surface of the roughened layer.

[0092] Step 6: Anti-oxidation treatment.

[0093] Heat resistance treatment: The heat resistance treatment solution contains 1.8 g / L zinc ions and 3.8 g / L nickel ions. 75 g / L (pH=11), temperature 30℃, current density 3 A / dm², treatment time 30 seconds.

[0094] Passivation treatment: The passivation solution contains 2.2g / L 95 g / L (pH=11.5), temperature 35℃, current density 2.6 A / dm², treatment time 25 seconds.

[0095] Step 7: Silanization treatment.

[0096] Organosilicon coupling agent: KH560, concentration 1.2g / L, pH=10, spraying temperature 30℃.

[0097] Treatment method: Spray evenly and let it drain for 10 seconds.

[0098] Step 8: Drying and winding.

[0099] Drying: Temperature 135℃, time 8 seconds.

[0100] Rewinding speed: 5m / min.

[0101] 3. Product performance testing: Thickness: 12μm (consistent with raw foil, no significant increase in thickness).

[0102] Surface roughness of the pressed surface: Rz=1.2μm, Ra=0.15μm.

[0103] Peel strength: 0.73 N / mm.

[0104] Pressing test: After hot pressing at 120℃ for 30 minutes, no copper powder fell off.

[0105] Corrosion resistance: After immersion in 5% NaCl solution for 48 hours, no oxidation spots are observed on the surface.

[0106] Option 2: Preparation of low-roughness, high-adhesion electrolytic copper foil.

[0107] 1. Raw material preparation: Electrolytic copper foil with a thickness of 20μm and a size of 400mm×600mm was selected.

[0108] 2. Adjustment of key process parameters (differences from Example 1): Step 1: Pickling solution 140g / L sulfuric acid, temperature 34℃, treatment time 40 seconds.

[0109] Step 2: Laser pulse energy 0.5mJ, scanning speed 10m / s, Ra=0.09μm after processing.

[0110] Step 3: The deposition solution contains 48 g / L copper ions and 24 mg / L deposition additives (8 mg / L MPS, 10 mg / L PEG, 6 mg / L polyethyleneimine), with a deposition thickness of 0.1 μm.

[0111] Step 4: The roughening solution contains 10 g / L copper ions, 110 g / L sulfuric acid, at a temperature of 20°C and a current density of 12 A / dm².

[0112] Step 5: Curing solution MPS 4mg / L, HEC 4mg / L, temperature 40℃, current density 8A / dm².

[0113] Step 6: Silane coupling agent KH550, concentration 1.0 g / L, pH=9.

[0114] 3. Product performance testing: Surface roughness of the pressed surface: Rz=1.3μm, Ra=0.17μm.

[0115] Peel strength: 0.75 N / mm.

[0116] Other properties: all meet the basic requirements (no copper powder falls off during pressing, good corrosion resistance).

[0117] Option 3: Preparation of low-roughness, high-adhesion electrolytic copper foil.

[0118] 1. Raw material preparation: Electrolytic copper foil with a thickness of 35μm and a size of 400mm×600mm was selected.

[0119] 2. Adjustment of key process parameters (differences from Example 1): Step 1: Pickling solution 150g / L sulfuric acid, temperature 40℃, treatment time 25 seconds.

[0120] Step 2: Laser pulse energy 5mJ, scanning speed 1m / s, Ra=0.07μm after processing.

[0121] Step 3: The deposition solution contains 52 g / L copper ions and 48 mg / L deposition additives (MPS 16 mg / L, PEG 20 mg / L, polyethyleneimine 12 mg / L), with a deposition thickness of 0.4 μm.

[0122] Step 4: The roughening solution contains 13 g / L copper ions, 130 g / L sulfuric acid, at a temperature of 30°C and a current density of 15 A / dm².

[0123] Step 5: Curing solution MPS 9mg / L, HEC 9mg / L, temperature 42℃, current density 12A / dm².

[0124] Step 6: Silane coupling agent KH570, concentration 1.5g / L, pH=12.

[0125] 3. Product performance testing: Surface roughness of the pressed surface: Rz=1.4μm, Ra=0.17μm.

[0126] Peel strength: 0.92 N / mm.

[0127] Other properties: No copper powder falls off after pressing, and the corrosion resistance is better than that of Example 1.

[0128]

[0129] The three embodiments described above achieved a synergistic effect of "low roughness" (Ra≤0.2μm, Rz≤1.5μm) and "high adhesion" (peel strength ≥0.7N / mm) by adjusting process parameters (such as laser energy, deposition thickness, additive concentration, etc.), and no copper powder fell off after pressing.

[0130] In a second embodiment, this application also proposes an electrolytic copper foil, which is prepared by a method for improving the adhesion between the electrolytic copper foil and the substrate under low roughness as described in the first aspect.

[0131] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of the invention. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as claimed in the appended claims.

[0132] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0133] Although the description of the invention has been given in conjunction with the specific embodiments described above, it will be apparent to those skilled in the art that many substitutions, modifications, and variations can be made based on the foregoing. Therefore, all such substitutions, modifications, and variations are included within the spirit and scope of the appended claims.

Claims

1. A method for improving the adhesion between electrolytic copper foil and substrate under low roughness, characterized in that, include: Step 1, pickling of raw foil: Select raw foil with a thickness of 9-35μm, and use the smooth side of the raw foil as the surface for rough curing treatment, and pickle it; Step 2, Laser leveling pretreatment: Selectively ablate the raised areas on the surface of the raw foil after acid pickling. The raised areas are those with a raised height > 100 nm. After laser leveling, the surface roughness Ra ≤ 0.1 μm. Step 3: Deposit a dense copper layer on the smooth surface of the laser-ablated copper foil to fill the micro-pits on the smooth surface of the raw foil after acid washing, homogenize the smooth surface of the raw foil and form a dense copper layer. Step 4: Roughen in a roughening tank containing a roughening solution; the roughening solution contains 10-13 g / L copper ions, 110-130 g / L sulfuric acid, 10-20 mg / L sodium tungstate, and 10-20 mg / L sodium molybdate. Step 5: Curing is carried out in a curing tank containing a curing solution; the curing solution contains 45-50 g / L copper ions, 90-100 g / L sulfuric acid, 4.0-9.0 mg / L sodium 3-mercapto-1-propanesulfonate (MPS), 4.0-9.0 mg / L hydroxyethyl cellulose (HEC), 4.0-9.0 mg / L polyethylene glycol (PEG), and 3.0-7.0 mg / L hydrolyzed collagen. Step 6, Anti-oxidation treatment: This includes heat resistance treatment and passivation treatment, which are carried out in treatment tanks containing heat resistance treatment solution and passivation treatment solution, respectively. Step 7, Silanization treatment: Spraying organosilane coupling agent; Step 8: Drying and winding to obtain electrolytic copper foil; the surface roughness of the pressed surface obtained by the smoothing treatment is Rz≤1.5μm, Ra≤0.2μm, peel strength≥0.7N / mm, and no copper powder falls off after pressing; wherein, the drying temperature is 130-140℃, the time is 5-10s, and the winding speed is 4-6m / min. In step 3, the deposition solution for depositing the dense copper layer contains 48-52 g / L of copper ions, 90-100 g / L of sulfuric acid, and 24-48 mg / L of deposition additives. The deposition additives include sodium 3-mercapto-1-propanesulfonate (MPS) at 8.0-16.0 mg / L, polyethylene glycol (PEG) at 10.0-20.0 mg / L, and polyethyleneimine at 6.0-12.0 mg / L. The polyethylene glycol has a molecular weight of 2000-3000 Da, and the polyethyleneimine has a molecular weight of 1000-2000 Da. In step 3, the dense copper layer is deposited at a deposition temperature of 40-42℃ and a current density of 8-12A / dm2, resulting in a dense copper layer with a thickness of 0.1-0.4μm.

2. The method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions according to claim 1, characterized in that, In step 1, the pickling solution is a sulfuric acid aqueous solution of 140-150 g / L, and the pickling temperature is 34-40℃.

3. The method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions according to claim 2, characterized in that, In step 2, the laser planarization pretreatment is performed using a picosecond laser with the following parameters: laser wavelength 532nm, pulse energy 0.5-5mJ, and scanning speed 1-10m / s.

4. The method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions according to claim 3, characterized in that, The conditions for roughening in step 4 are: temperature 20-30 °C, current density 12-15 A / dm 2 .

5. The method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions according to claim 4, characterized in that, The conditions for curing in Step 5 were: temperature 40-42°C, current density 8-12 A / dm 2 .

6. The method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions according to claim 5, characterized in that, The heat-resistant treatment solution in step 6 contains 1.1-2.6 g / L of zinc ions, 2.3-5.4 g / L of nickel ions, and 70-80 g / L of K4P2O7. The pH of the heat-resistant treatment solution is 10-12. The conditions for heat treatment resistance are: temperature 25-35°C, current density 2.5-3.5 A / dm 2 ; The passivation solution in step 6 contains CrO4 2- 2.0-2.5 g / L and K4P2O7 90-100 g / L, wherein the pH of the passivation solution is 11-12; The passivation conditions are: temperature 30-40℃, current density 2.4-2.8 A / dm³. 2 .

7. The method for improving the adhesion between electrolytic copper foil and substrate under low roughness conditions according to claim 6, characterized in that, In step 7, the organosilane coupling agent sprayed is at least one of KH550, KH560 and KH570, the concentration of the organosilane coupling agent is 1.0-1.5 g / L, the pH is 9-12, and the spraying temperature is 25-35℃.

Images