High tensile strength electrolytic copper foil and method for producing the same

Abstract

The application provides an electrolytic copper foil for electromagnetic shielding and a preparation method thereof, and relates to the technical field of electrolytic copper foils.The electrolytic copper foil comprises a copper foil substrate, a roughening layer and a functional layer arranged in sequence along the thickness direction, and the roughening layer comprises copper roughening particles formed on the surface of the copper foil substrate.During preparation, the electrolytic green foil is subjected to pickling, then the copper roughening particles are formed through electrochemical roughening, the roughened surface is subjected to limited degree chemical micro-etching, then the copper roughening particle surface subjected to micro-etching treatment is further deposited with copper to form the roughening layer, and surface treatment is performed to form the functional layer.The application controls the size, distribution and bonding stability of the roughening particles through the continuous treatment of electrochemical roughening, chemical micro-etching and subsequent copper deposition, reduces the copper transfer of the roughening layer after mechanical action, retains the effective roughening structure, and thus gives consideration to the anti-dusting stability of the roughening layer and the interfacial bonding performance between the roughening layer and the resin substrate.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil preparation, and in particular to a high tensile strength electrolytic copper foil and its preparation method. Background Technology

[0002] Electrolytic copper foil possesses excellent electrical conductivity and processing properties, and is widely used in printed circuit boards, flexible circuit boards, and other electronic circuit products. As electronic circuits become increasingly thinner and more refined, copper foil needs to withstand certain mechanical loads during lamination, etching, slitting, and subsequent processing. Therefore, higher requirements are placed on the tensile strength, elongation, and electrical conductivity of electrolytic copper foil.

[0003] In the existing technology, the main methods to improve the tensile strength of electrolytic copper foil include adjusting the electrolyte composition, changing the organic additive system, controlling the copper crystal structure, and introducing trace strengthening elements into electrodeposited copper.

[0004] For example, Chinese patent (authorization announcement number: CN1125194C) discloses a high tensile strength electrolytic copper foil and its manufacturing method. It uses an electrolyte containing copper sulfate and sulfuric acid as the main components, and iron ions, polyether, tin sulfate and low concentration of chloride ions for electrodeposition. The copper deposition process is adjusted by tin ions, iron ions and polyether to improve the tensile strength of the copper foil and its mechanical properties after heating.

[0005] US Patent (Patent No.: US6194056B1) discloses a high tensile strength electrodeposited copper foil, which uses a copper sulfate-sulfuric acid electrolyte containing polyether, tin ions and iron ions for electrodeposition. The copper foil has a tin content of 50-1200 ppm and an iron content of 1-50 ppm. The tensile properties of the copper foil at room temperature and after heat treatment are improved by adjusting the copper crystal orientation and surface state.

[0006] In addition, Chinese patent (authorization announcement number: CN107587172B) discloses a high-strength, high-heat-resistant electrolytic copper alloy foil and its manufacturing method. It improves the tensile strength of the copper foil and the strength retention performance after heat treatment by introducing tungsten element into the electrolytic copper foil and utilizing the influence of tungsten-containing components on copper grain growth.

[0007] The aforementioned existing technologies mainly improve the mechanical properties of electrolytic copper foil by adjusting the electrolyte composition, controlling the crystal structure, or introducing trace reinforcing elements such as tin and tungsten into the electrodeposited copper. For techniques using trace reinforcing elements, these elements typically enter the copper foil material during the electrodeposition process, and the degree of reinforcement depends on the amount and distribution of these elements within the copper foil. Increasing the overall amount of reinforcing elements improves the reinforcement level of the copper foil, but it may also increase the influence of the reinforcing elements on the plastic deformation and electron transport of the copper matrix, thus affecting the elongation and conductivity of the copper foil. Conversely, reducing the overall amount of reinforcing elements may result in insufficient reinforcement.

[0008] Therefore, a new solution is needed to rationally control the distribution and local content of strengthening elements in electrolytic copper foil, obtain the required strengthening effect while controlling the overall amount of strengthening elements introduced, and take into account the elongation and conductivity of electrolytic copper foil. Summary of the Invention

[0009] The purpose of this invention is to provide a high tensile strength electrolytic copper foil and its preparation method, so as to solve the problem that electrolytic copper foil reinforced with trace strengthening elements in the prior art is difficult to balance tensile strength, elongation and conductivity.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] A high tensile strength electrolytic copper foil, wherein the high tensile strength electrolytic copper foil comprises, along its thickness direction, a copper foil substrate and a reinforcing layer formed on the surface of the copper foil substrate;

[0012] The copper foil substrate contains 300-500 ppm of tin, the reinforcing layer is a copper-tin alloy layer, the reinforcing layer contains 2200-4000 ppm of tin, and the ratio of the tin content in the reinforcing layer to the tin content in the copper foil substrate is (7-10):1.

[0013] The thickness of the reinforcing layer is 0.5-2.5 μm, and the thickness of the reinforcing layer accounts for 5%-18% of the total thickness of the high tensile electrolytic copper foil;

[0014] The high tensile strength electrolytic copper foil has a room temperature tensile strength of 550-680 MPa, a room temperature elongation of 4.0%-8.0%, and an electrical conductivity of 90%-98% IACS.

[0015] Preferably, the average tin content in the high tensile electrolytic copper foil is 450-900 ppm.

[0016] Preferably, after the high tensile strength electrolytic copper foil is kept at 180°C for 60 minutes and then cooled to room temperature, the tensile strength retention rate is 82%-95% and the elongation rate is 3.5%-7.0%.

[0017] Furthermore, the present invention also provides a method for preparing high tensile strength electrolytic copper foil, comprising the following steps:

[0018] S1. Prepare the first electrolyte, place the rotating cathode roller in the first electrolyte for continuous electrodeposition, so that copper ions and tin ions are deposited together, and a copper foil substrate with a tin content of 300-500ppm is formed on the surface of the rotating cathode roller.

[0019] S2. While the copper foil substrate is still attached to the rotating cathode roller, the copper foil substrate is removed from the first electrolyte and its surface is brought into contact with a second electrolyte with a higher tin ion concentration than the first electrolyte. Electrodeposition continues, allowing copper ions and tin ions to be deposited together, forming a copper-tin alloy reinforcement layer with a tin content of 2200-4000 ppm on the surface of the copper foil substrate.

[0020] S3. By adjusting the tin ion concentration in the first and second electrolytes and the electrodeposition conditions in the first and second stages, the ratio of tin content in the reinforcing layer to tin content in the copper foil substrate is (7-10):1, and the thickness of the reinforcing layer is 0.5-2.5 μm, accounting for 5%-18% of the total thickness of the obtained high tensile electrolytic copper foil; after the obtained high tensile electrolytic copper foil reaches the predetermined thickness, it is peeled off.

[0021] Preferably, both the first electrolyte and the second electrolyte include a copper source, a tin source, sulfuric acid, a chloride ion source, a polyether inhibitor, a sulfur-containing accelerator, and a nitrogen-containing leveling agent.

[0022] Preferably, the copper source is copper sulfate, and the tin source is stannous sulfate;

[0023] The chloride ion source is selected from at least one of hydrochloric acid, sodium chloride, and potassium chloride;

[0024] The polyether inhibitor is selected from at least one of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer;

[0025] The sulfur-containing accelerator is selected from at least one of disodium bis-(3-sulfopropyl)disulfide and 3-mercapto-1-propanesulfonate;

[0026] The nitrogen-containing leveling agent is selected from at least one of polyethyleneimine and polyquaternary ammonium salt.

[0027] Preferably, in the first electrolyte, Cu 2+ The concentration is 75-105 g / L, Sn 2+ The concentration of [unspecified substance] is 0.03-0.08 g / L, the concentration of H2SO4 is 90-120 g / L, and the concentration of Cl [unspecified substance] is [unspecified substance]. -The concentration of the first electrolyte is 15-30 mg / L, the concentration of the polyether inhibitor is 4-10 mg / L, the concentration of the sulfur-containing accelerator is 0.5-1.5 mg / L, the concentration of the nitrogen-containing leveling agent is 0.3-1.0 mg / L, and the temperature of the first electrolyte is 48-58℃.

[0028] Preferably, in the second electrolyte, Cu 2+ The concentration is 75-100 g / L, Sn 2+ The concentration of [unspecified substance] is 0.25-0.7 g / L, the concentration of H2SO4 is 90-120 g / L, and the concentration of Cl [unspecified substance] is [unspecified substance]. - The concentration of the first electrolyte is 15-30 mg / L, the concentration of the polyether inhibitor is 2-6 mg / L, the concentration of the sulfur-containing accelerator is 1.0-3.0 mg / L, the concentration of the nitrogen-containing leveling agent is 0.5-1.5 mg / L, and the temperature of the second electrolyte is 48-58℃.

[0029] Preferably, the second electrolyte and the Sn in the first electrolyte 2+ The concentration ratio of the second electrolyte to the first electrolyte is (5-15):1, the concentration ratio of the sulfur-containing accelerator in the second electrolyte to the first electrolyte is (1.5-4.0):1, and the concentration ratio of the polyether inhibitor in the second electrolyte to the first electrolyte is (0.1-0.8):1.

[0030] Preferably, the cathode current density when electrodepositing with the first electrolyte is 28-45 A / dm², the cathode current density when electrodepositing with the second electrolyte is 35-58 A / dm², and the ratio of the cathode current density when electrodepositing with the second electrolyte to the cathode current density when electrodepositing with the first electrolyte is (1.05-1.30):1.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The high tensile strength electrolytic copper foil of the present invention forms a copper-tin alloy reinforcing layer with a high tin content on the surface of the copper foil substrate, so that the tin element is distributed differentially along the thickness direction of the high tensile strength electrolytic copper foil. By controlling the tin content, tin content ratio in the copper foil substrate and the reinforcing layer, as well as the thickness and thickness ratio of the reinforcing layer, a higher content of tin element is concentrated in the finite thickness of the reinforcing layer. While exerting a local strengthening effect, the overall amount of tin element introduced is controlled, so that the resulting high tensile strength electrolytic copper foil has high tensile strength and maintains corresponding elongation and conductivity.

[0033] 2. The preparation method of the present invention employs a continuous two-stage electrodeposition process. In the first stage, a first electrolyte is used to form a copper foil substrate with a low tin content. While the copper foil substrate is still attached to the rotating cathode roller, electrodeposition continues using a second electrolyte with a higher tin ion concentration, forming a reinforcing layer with a higher tin content on the surface of the copper foil substrate. By separately controlling the electrolyte composition and electrodeposition conditions in the two stages, the tin content in the copper foil substrate and the reinforcing layer can be differentially controlled, and the reinforcing layer can be directly formed on the surface of the copper foil substrate, thereby achieving the continuous preparation of the high tensile strength electrolytic copper foil. Attached Figure Description

[0034] The accompanying drawings are used to further illustrate the technical solutions of the present invention and constitute a part of this specification. The following drawings illustrate exemplary embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0035] Figure 1 This is a schematic diagram of the high tensile strength electrolytic copper foil in this invention;

[0036] Figure 2 This is a schematic diagram of the process for preparing high tensile strength electrolytic copper foil in this invention;

[0037] Figure 3 This is a comparison chart of the tin content of the reinforcing layer and the tensile strength at room temperature in Example 1 and Comparative Example 2 of the present invention;

[0038] Figure 4 This is a comparison chart of the tin content and conductivity of the strengthening layer in Example 1 and Comparative Example 2 of the present invention. Detailed Implementation

[0039] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the invention will be more thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0040] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of the invention. However, those skilled in the art will recognize that the technical solutions of the invention can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of the invention.

[0041] According to a first aspect of the present invention, a high-tensile-strength electrolytic copper foil is provided, comprising, along its thickness direction, a copper foil substrate and a reinforcing layer formed on the surface of the copper foil substrate. In this invention, the copper foil substrate corresponds to a main region formed by a first-stage electrodeposition using a first electrolyte; the reinforcing layer corresponds to a copper-tin alloy region formed on the surface of the copper foil substrate by a second-stage electrodeposition using a second electrolyte while the copper foil substrate is still attached to the rotating cathode roller. The reinforcing layer is not an independent tin layer, but rather a copper-tin alloy region formed by the co-electrodeposition of copper ions and tin ions. By making the copper foil substrate and the reinforcing layer have different tin content, and by limiting the thickness of the reinforcing layer and its proportion to the total thickness of the high-tensile-strength electrolytic copper foil, a differentiated configuration of tin elements is achieved along the thickness direction of the high-tensile-strength electrolytic copper foil.

[0042] In this application, unless otherwise stated, ppm means parts per million by mass, that is, one part per million by mass.

[0043] In some embodiments of the present invention, the tin content in the copper foil matrix is ​​300-500 ppm, for example, 300 ppm, 350 ppm, 400 ppm, 450 ppm, or 500 ppm. When the tin content in the copper foil matrix is ​​within the above range, the copper foil matrix maintains a low tin introduction level, allowing the copper foil matrix to participate in the overall mechanical load-bearing while avoiding an increase in the overall alloying degree of the high-tensile electrolytic copper foil due to excessive tin content in the main body of the copper foil. If the tin content in the copper foil matrix is ​​too low, the overall strengthening degree of the resulting high-tensile electrolytic copper foil may be insufficient when the thickness of the reinforcing layer is limited; if the tin content in the copper foil matrix is ​​too high, it will increase the amount of tin introduced into the main body of the copper foil, which is detrimental to the maintenance of elongation and conductivity.

[0044] In some embodiments of the present invention, the tin content in the reinforcing layer is 2200-4000 ppm, for example, 2200 ppm, 2500 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3500 ppm, 3800 ppm, or 4000 ppm. The tin content in the reinforcing layer is higher than the tin content in the copper foil substrate, allowing the higher tin content to concentrate in the reinforcing layer without simultaneously increasing the tin content in the entire copper foil substrate. If the tin content in the reinforcing layer is too low, the difference in tin content between the reinforcing layer and the copper foil substrate decreases, which is not conducive to forming the desired localized strengthening effect; if the tin content in the reinforcing layer is too high, the alloying degree in the high-tin content region further increases, which may adversely affect the elongation and conductivity of the resulting high-tensile electrolytic copper foil.

[0045] In some embodiments of the present invention, the ratio of tin content in the reinforcing layer to tin content in the copper foil substrate is (7-10):1, for example, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, or 10:1. By limiting the above tin content ratio, a clear difference in tin content is maintained between the reinforcing layer and the copper foil substrate, and the reinforcing layer assumes the function of a region with higher tin content. If the above tin content ratio is too small, the difference in tin content between the reinforcing layer and the copper foil substrate is insufficient; if the above tin content ratio is too large, it is necessary to further increase the tin content in the reinforcing layer or decrease the tin content in the copper foil substrate, which may lead to a narrowing of the coordination range between the degree of reinforcement, elongation performance, and conductivity performance.

[0046] In some embodiments of the present invention, the thickness of the reinforcing layer is 0.5-2.5 μm, for example, it can be 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, or 2.5 μm; the thickness of the reinforcing layer accounts for 5%-18% of the total thickness of the high-tensile electrolytic copper foil, for example, it can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, or 18%. Limiting the thickness and percentage of the reinforcing layer keeps the high-tin content region within a limited range in the high-tensile electrolytic copper foil. When the thickness or percentage of the reinforcing layer is too small, the contribution of the reinforcing layer to the overall performance of the high-tensile electrolytic copper foil is limited; when the thickness or percentage of the reinforcing layer is too large, the proportion of the high-tin content region in the high-tensile electrolytic copper foil increases, correspondingly increasing the overall introduction of tin, which is detrimental to maintaining elongation and conductivity. The aforementioned structural parameters, together with the tin content in the copper foil substrate and reinforcing layer, enable the high tensile electrolytic copper foil to be strengthened through localized areas with higher tin content, while controlling the overall tin content of the copper foil.

[0047] In some embodiments of the present invention, the average tin content in the high-tensile electrolytic copper foil is 450-900 ppm, for example, 450 ppm, 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 750 ppm, 800 ppm, 850 ppm, or 900 ppm. The average tin content in the high-tensile electrolytic copper foil is determined by the tin content in the copper foil matrix, the tin content in the reinforcing layer, and the thickness ratio of the reinforcing layer. By having a relatively low tin content in the copper foil matrix and placing a higher tin content in a reinforcing layer of limited thickness, the high-tensile electrolytic copper foil can form locally higher tin content areas while maintaining its overall average tin content within the aforementioned range, thus corresponding to the technical requirements for controlling the overall introduction amount of reinforcing elements.

[0048] In some embodiments of the present invention, the high-tensile electrolytic copper foil has a room-temperature tensile strength of 550-680 MPa, for example, 550 MPa, 570 MPa, 590 MPa, 610 MPa, 630 MPa, 650 MPa, 670 MPa or 680 MPa; a room-temperature elongation of 4.0%-8.0%, for example, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5% or 8.0%; and a conductivity of 90%-98% IACS, for example, 90% IACS, 91% IACS, 92% IACS, 93% IACS, 94% IACS, 95% IACS, 96% IACS, 97% IACS or 98% IACS. The aforementioned performance parameters are used to characterize the tensile strength, elongation, and conductivity of high-tensile electrolytic copper foil, respectively, corresponding to the problem that it is difficult to simultaneously achieve these three properties in existing trace-strengthening processes, which this invention aims to address. By limiting the tin content, tin content ratio, and the thickness and thickness ratio of the strengthening layer in the copper foil matrix and the strengthening layer, the resulting high-tensile electrolytic copper foil achieves high room-temperature tensile strength while maintaining corresponding room-temperature elongation and conductivity.

[0049] In some embodiments of the present invention, after the high-tensile-strength electrolytic copper foil is held at 180°C for 60 minutes and then cooled to room temperature, its tensile strength retention rate is 82%-95%, for example, 82%, 84%, 86%, 88%, 90%, 92%, 94%, or 95%, and its elongation is 3.5%-7.0%, for example, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, or 7.0%. This property is used to further characterize the retention of mechanical properties of the obtained high-tensile-strength electrolytic copper foil after heat treatment, and serves as a supplementary performance indicator in addition to room temperature tensile strength and room temperature elongation.

[0050] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-mentioned high tensile strength electrolytic copper foil, comprising the following steps:

[0051] S1. Prepare the first electrolyte, place the rotating cathode roller in the first electrolyte for continuous electrodeposition, so that copper ions and tin ions are deposited together, and a copper foil substrate with a tin content of 300-500ppm is formed on the surface of the rotating cathode roller.

[0052] S2. While the copper foil substrate is still attached to the rotating cathode roller, the copper foil substrate is removed from the first electrolyte and its surface is brought into contact with the second electrolyte, which has a higher tin ion concentration than the first electrolyte. Electrodeposition continues, so that copper ions and tin ions are deposited together to form a copper-tin alloy reinforcement layer with a tin content of 2200-4000ppm on the surface of the copper foil substrate.

[0053] S3. By adjusting the tin ion concentration in the first and second electrolytes and the electrodeposition conditions in the first and second stages, the ratio of tin content in the reinforcing layer to tin content in the copper foil substrate is (7-10):1, and the thickness of the reinforcing layer is 0.5-2.5μm and accounts for 5%-18% of the total thickness of the obtained high tensile electrolytic copper foil; after the obtained high tensile electrolytic copper foil reaches the predetermined thickness, it is peeled off.

[0054] It should be noted that the rotating cathode roller in this invention serves as the cathode and copper foil deposition carrier in the electrodeposition process. The copper foil substrate formed in the first stage of electrodeposition is attached to the surface of the rotating cathode roller and moves continuously with the rotating cathode roller to the second stage of the electrodeposition process.

[0055] The predetermined thickness refers to the total thickness of the copper foil that is pre-set according to the target electrolytic copper foil specifications. The thickness of the copper foil substrate and the reinforcing layer can be adjusted by the deposition time, current density and operating conditions of the rotating cathode roller in the corresponding electrodeposition stage.

[0056] Steps S1 to S3 involve a two-stage electrodeposition process to form a copper foil substrate and a reinforcing layer. Step S1 uses a first electrolyte to form a copper foil substrate with a relatively low tin content. Step S2, while the copper foil substrate is still attached to the rotating cathode roller, continues electrodeposition using a second electrolyte to form a copper-tin alloy reinforcing layer with a higher tin content on the surface of the copper foil substrate. Step S3 further controls the tin content ratio between the reinforcing layer and the copper foil substrate, as well as the thickness and thickness percentage of the reinforcing layer. This results in varying tin content levels in different regions of the high-tensile-strength electrolytic copper foil, rather than maintaining a uniform or similar tin content across the entire thickness of the copper foil. This creates a structure combining the copper foil substrate and the reinforcing layer in the high-tensile-strength electrolytic copper foil. The copper foil substrate constitutes the main body of the high-tensile-strength electrolytic copper foil, while the reinforcing layer represents the region with a relatively high tin content; together, they form the final high-tensile-strength electrolytic copper foil.

[0057] It should be noted that both the first and second electrolytes contain copper, tin, sulfuric acid, chloride ion, polyether inhibitors, sulfur-containing accelerators, and nitrogen-containing leveling agents. However, the tin ion concentration in the second electrolyte is higher than that in the first electrolyte, thus differentiating the tin introduction conditions in step S2 from those in step S1. The first electrolyte is used to co-deposit copper and tin ions to form a copper foil substrate with a tin content of 300-500 ppm. The second electrolyte is used to further form a copper-tin alloy reinforcing layer with a higher tin content on the surface of the copper foil substrate. Through this two-stage electrodeposition method, it is not necessary to simultaneously increase the tin content in the copper foil substrate to form a higher tin content in a localized area. Simultaneously, the copper foil substrate is not peeled off from the rotating cathode roller before the reinforcing layer is formed, allowing the second-stage electrodeposition to continue directly on the already formed copper foil substrate surface. This helps maintain the continuous connection between the copper foil substrate and the reinforcing layer, and forms a high-tensile-strength electrolytic copper foil.

[0058] It is understood that this invention controls the tin content in the copper foil substrate and the reinforcing layer through steps S1 and S2 respectively, and controls the tin content ratio between the two and the thickness ratio of the reinforcing layer in the high-tensile electrolytic copper foil through step S3. The aim is to avoid simply increasing the amount of tin introduced into the entire copper foil to achieve higher tensile strength. The tin content in the copper foil substrate is maintained at 300-500 ppm, ensuring a relatively low tin content in the areas constituting the main thickness; the tin content in the reinforcing layer is higher than that in the copper foil substrate, concentrating the higher tin content in areas of limited thickness. Through this compositional and structural relationship, while controlling the overall tin introduction into the high-tensile electrolytic copper foil, the reinforcing layer can have a relatively high tin content, thus addressing the problem that existing methods of strengthening with trace reinforcing elements often fail to simultaneously achieve tensile strength, elongation, and conductivity.

[0059] It is worth noting that in step S3, the ratio of tin content in the reinforcing layer to tin content in the copper foil substrate, as well as the proportion of reinforcing layer thickness, need to be controlled in a coordinated manner. The tin content ratio is (7-10):1, maintaining a certain difference in tin content between the reinforcing layer and the copper foil substrate; the reinforcing layer thickness is 0.5-2.5 μm and accounts for 5%-18% of the total thickness of the high-tensile-strength electrolytic copper foil, keeping the tin-rich reinforcing layer within a limited thickness range. If the proportion of the reinforcing layer is too small, its effect on the overall performance of the high-tensile-strength electrolytic copper foil may be limited; if the proportion of the reinforcing layer is too large, the proportion of high-tin-content areas in the high-tensile-strength electrolytic copper foil increases, correspondingly increasing the overall tin introduction. Therefore, the above-mentioned tin content ratio and the relationship between the reinforcing layer size are used to adjust the relationship between the degree of local reinforcement and the overall tin introduction, so that the obtained high-tensile-strength electrolytic copper foil can maintain corresponding elongation and conductivity while achieving high tensile strength.

[0060] Furthermore, the continuous two-stage electrodeposition of the present invention refers to the copper foil substrate not being peeled off from the surface of the rotating cathode roller after the first stage electrodeposition is completed, and continuing to perform the second stage electrodeposition while still attached to the rotating cathode roller, so that the strengthening layer is directly formed on the surface of the copper foil substrate.

[0061] In some embodiments of the present invention, both the first electrolyte and the second electrolyte contain a chloride ion source, a polyether inhibitor, a sulfur-containing accelerator, and a nitrogen-containing leveling agent. Chloride ions are mainly used to regulate the adsorption and electrodeposition state at the cathode interface, and together with organic additives, influence the deposition process of copper ions; the polyether inhibitor is used to suppress excessively rapid deposition in localized areas, thereby reducing the unevenness of the deposition layer thickness and surface condition; the sulfur-containing accelerator is used to regulate the deposition activity of the cathode surface, enabling copper ions to continuously deposit under a set current density; and the nitrogen-containing leveling agent is used to improve the deposition uniformity between different regions. The above components are related to Cu... 2+ Sn 2+ H2SO4 and cathode current density together constitute the electrodeposition conditions, which are used to ensure that the copper foil substrate and the reinforcing layer can be formed continuously, and to make the resulting electrodeposited layer have a relatively stable composition and thickness.

[0062] In some embodiments of the present invention, the chloride ion concentrations in the first electrolyte and the second electrolyte are maintained within a similar range, while the second electrolyte, relative to the first electrolyte, increases the concentrations of Sn²⁺ and sulfur-containing accelerators and decreases the concentration of polyether inhibitors, while simultaneously employing a higher cathode current density. Through these parameter adjustments, the electrodeposition conditions in the second stage differ from those in the first stage, thereby increasing the amount of tin introduced into the reinforcing layer. This results in a higher tin content in the reinforcing layer than in the copper foil substrate, without simultaneously increasing the tin content in the copper foil substrate. Thus, the first stage is used to form a copper foil substrate with a lower tin content, and the second stage is used to form a copper-tin alloy reinforcing layer with a higher tin content. The two stages work together to achieve a differentiated configuration of tin in the high-tensile electrolytic copper foil, addressing the problem in the prior art where it is difficult to coordinate tensile strength, elongation, and conductivity when the overall amount of reinforcing elements introduced increases.

[0063] In some embodiments of the present invention, while other electrodeposition conditions remain unchanged, the Sn in the second electrolyte is adjusted... 2+ The concentration can be adjusted to regulate the degree of tin introduction during the second-stage electrodeposition process, thereby regulating the tin content in the reinforcing layer. With the total thickness of the resulting electrolytic copper foil remaining constant, the thicknesses of the copper foil substrate and the reinforcing layer can be controlled separately by adjusting the electrodeposition levels of the first and second stages, thus adjusting the proportion of the reinforcing layer thickness to the total thickness of the resulting electrolytic copper foil. The electrodeposition level at each stage can be adjusted by the deposition time, current density, and / or the operating speed of the rotating cathode roller.

[0064] Example 1:

[0065] Please see Figure 1-2 This embodiment provides a method for preparing high tensile strength electrolytic copper foil, including the following steps:

[0066] Step S1: Preparation of copper foil substrate. Take an appropriate amount of deionized water, add copper sulfate, stannous sulfate, sulfuric acid, hydrochloric acid, polyethylene glycol, disodium bis-(3-sulfopropyl)disulfide, and polyethyleneimine. After all components dissolve, dilute to volume with deionized water to obtain the first electrolyte; wherein, in the first electrolyte, Cu... 2+ Concentration of 90 g / L, Sn 2+ The concentration is 0.05 g / L, the H2SO4 concentration is 105 g / L, and the Cl concentration is... - The electrolyte concentrations were 22 mg / L, polyethylene glycol 8.0 mg / L, disodium bis-(3-sulfopropyl)disulfide 0.8 mg / L, and polyethyleneimine 0.6 mg / L. The temperature of the first electrolyte was 53 °C. A rotating cathode roller was placed in the first electrolyte, and continuous electrodeposition was performed at a cathode current density of 36 A / dm² until a copper foil substrate with a thickness of 10.8 μm was formed on the surface of the rotating cathode roller.

[0067] Step S2: Preparation of the reinforcement layer. Take an appropriate amount of deionized water, add copper sulfate, stannous sulfate, sulfuric acid, hydrochloric acid, polyethylene glycol, disodium bis-(3-sulfopropyl)disulfide, and polyethyleneimine. After all components dissolve, dilute to volume with deionized water to obtain the second electrolyte. The second electrolyte contains Cu... 2+ Concentration of 88 g / L, Sn 2+ The concentration is 0.40 g / L, the H2SO4 concentration is 105 g / L, and the Cl concentration is... - The concentrations of the electrolytes were 22 mg / L, polyethylene glycol 4.0 mg / L, disodium bis-(3-sulfopropyl)disulfide 1.6 mg / L, and polyethyleneimine 0.9 mg / L. The temperature of the second electrolyte was 53°C. After the first stage of electrodeposition, the copper foil substrate was kept attached to the surface of the rotating cathode roller, allowing the copper foil substrate to leave the first electrolyte and its surface to contact the second electrolyte. Electrodeposition continued at a cathode current density of 42 A / dm² until a 1.2 μm thick reinforcing layer was formed on the surface of the copper foil substrate.

[0068] Step S3: Obtaining high tensile electrolytic copper foil. After completing the second stage of electrodeposition, the obtained electrolytic copper foil is peeled off from the surface of the rotating cathode roller, washed with deionized water and dried to obtain a high tensile electrolytic copper foil with a total thickness of 12.0 μm, wherein the thickness of the reinforcing layer accounts for 10% of the total thickness of the high tensile electrolytic copper foil.

[0069] The tin element composition and properties of the obtained high tensile electrolytic copper foil were determined according to the following test methods.

[0070] Example 2

[0071] The difference from Example 1 is that Sn in the second electrolyte in step S2 2+ The concentration was 0.35 g / L; the composition of the electrolyte, electrodeposition conditions, thickness of the reinforcing layer and other process parameters were the same as in Example 1.

[0072] Example 3

[0073] The difference from Example 1 is that Sn in the second electrolyte in step S2 2+ The concentration was 0.50 g / L; the composition of the electrolyte, electrodeposition conditions, thickness of the reinforcing layer and other process parameters were the same as in Example 1.

[0074] Example 4

[0075] The difference from Example 1 is that in step S1, a first-stage electrodeposition is performed until a copper foil substrate with a thickness of 11.4 μm is formed; in step S2, a second-stage electrodeposition is performed until a reinforcing layer with a thickness of 0.6 μm is formed on the surface of the copper foil substrate, so that the thickness of the reinforcing layer accounts for 5% of the total thickness of the high tensile electrolytic copper foil; the total thickness of the resulting high tensile electrolytic copper foil is 12.0 μm; the remaining process steps and process parameters are the same as in Example 1.

[0076] Example 5

[0077] The difference from Example 1 is that in step S1, a first-stage electrodeposition is performed until a copper foil substrate with a thickness of 9.84 μm is formed; in step S2, a second-stage electrodeposition is performed until a reinforcing layer with a thickness of 2.16 μm is formed on the surface of the copper foil substrate, so that the thickness of the reinforcing layer accounts for 18% of the total thickness of the high tensile electrolytic copper foil; the total thickness of the resulting high tensile electrolytic copper foil is 12.0 μm; the remaining process steps and process parameters are the same as in Example 1.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that an electrolytic copper foil is prepared by a single-stage continuous electrodeposition method, without the preparation of the strengthening layer in step S2; the electrodeposition is carried out continuously using the first electrolyte and corresponding electrodeposition conditions in step S1 of Example 1 until an electrolytic copper foil with a total thickness of 12.0 μm is formed on the surface of the rotating cathode roller. The obtained electrolytic copper foil is then peeled off from the surface of the rotating cathode roller, washed with deionized water and dried; the remaining process conditions are the same as in Example 1.

[0080] Comparative Example 2

[0081] The difference from Example 1 is that Sn in the second electrolyte in step S2 2+The concentration was 0.20 g / L; the composition of the electrolyte, electrodeposition conditions, thickness of the reinforcing layer and other process parameters were the same as in Example 1.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that in step S1, a first-stage electrodeposition is performed until a copper foil substrate with a thickness of 9.0 μm is formed; in step S2, while the copper foil substrate is attached to the rotating cathode roller, the surface of the copper foil substrate is brought into contact with the second electrolyte, and a second-stage electrodeposition is performed until a copper-tin alloy layer with a thickness of 3.0 μm is formed on the surface of the copper foil substrate. The thickness of the copper-tin alloy layer accounts for 25% of the total thickness of the obtained electrolytic copper foil, and the total thickness of the obtained electrolytic copper foil is 12.0 μm; the remaining electrolyte composition, electrodeposition conditions and process parameters are the same as in Example 1.

[0084] Performance testing

[0085] The composition, structure and performance of the electrolytic copper foils prepared in Examples 1-5 and Comparative Examples 1-3 were tested. The specific test methods are as follows.

[0086] (1) Tin content test: The average tin content in electrolytic copper foil was determined by ICP-OES. A certain mass of electrolytic copper foil sample was taken, digested with acid, and then tested after being brought to a constant volume. The average tin content in the electrolytic copper foil was calculated based on the measured tin content and the sample mass. The tin content in the reinforcing layer was determined by X-ray fluorescence spectrometry (XRF). A standard sample matching the copper-tin alloy reinforcing layer / copper foil substrate bilayer system was used for calibration, and the surface of the reinforcing layer was tested to reduce the influence of the copper foil substrate on the tin content determination results of the reinforcing layer. Based on the average tin content in the electrolytic copper foil, the tin content in the reinforcing layer, and the mass ratio of the reinforcing layer to the copper foil substrate, the tin content in the copper foil substrate was calculated according to the mass conservation relationship, and the ratio of the tin content in the reinforcing layer to the tin content in the copper foil substrate was further calculated. At least 3 parallel samples were taken for each group of samples, and the test results were taken as the arithmetic mean.

[0087] (2) Thickness test: The total thickness of the electrolytic copper foil was measured using a metal foil thickness gauge. The thickness of the reinforcing layer was measured using an X-ray fluorescence film thickness measurement method calibrated with a standard sample of the copper-tin alloy reinforcing layer / copper foil substrate double-layer system. The ratio of the reinforcing layer thickness to the total thickness of the electrolytic copper foil was calculated. At least 5 locations were selected for measurement in each sample group, and the arithmetic mean was taken as the test result.

[0088] (3) Room temperature tensile strength and room temperature elongation test: The test was conducted according to GB / T 29847-2025 "Test Method for Copper Foil for Printed Circuit Boards". Samples were cut longitudinally from the obtained electrolytic copper foil and subjected to tensile testing at room temperature using a universal testing machine. The initial gauge length was 50 mm, and the tensile speed was 50 mm / min until the sample broke. The room temperature tensile strength was calculated based on the maximum tensile load, and the room temperature elongation was calculated based on the change in gauge length before and after the sample broke. At least four valid samples were selected from each group for testing, and the arithmetic mean of the results was taken.

[0089] (4) Conductivity test: The resistance of electrolytic copper foil was determined according to GB / T 29847-2025 "Test Method for Copper Foil for Printed Circuit Boards". The volume resistivity was calculated based on the sample length, cross-sectional area and measured resistance. The results were converted to the conditions at 20℃ and the relative conductivity was calculated according to the international standard for annealed copper, expressed as %IACS. Each group of samples was subjected to no less than 3 valid tests, and the arithmetic mean was taken as the test result.

[0090] (5) Mechanical property test after heat treatment: The electrolytic copper foil sample was kept at 180℃ for 60 min and cooled to room temperature. The tensile strength and elongation after heat treatment were determined according to the above test methods for room temperature tensile strength and room temperature elongation. The tensile strength retention rate was calculated as the ratio of the tensile strength after heat treatment to the room temperature tensile strength before heat treatment.

[0091] The electrolytic copper foils prepared in Examples 1-5 and Comparative Examples 1-3 were tested according to the above test methods, and the results of their composition and performance tests are shown in Table 1.

[0092] Table 1. Composition and performance test results of electrolytic copper foils obtained in Examples 1-5 and Comparative Examples 1-3

[0093]

[0094] As shown in Table 1, in the high tensile strength electrolytic copper foils obtained in Examples 1-5, the tin content of the reinforcing layer is higher than that of the copper foil substrate. Furthermore, by controlling the difference in tin content between the reinforcing layer and the copper foil substrate, the obtained high tensile strength electrolytic copper foils can maintain corresponding room-temperature elongation and conductivity while possessing high room-temperature tensile strength. Compared to Example 1, Comparative Example 1 uses single-stage continuous electrodeposition, which does not form a reinforcing layer with high tin content, resulting in lower room-temperature tensile strength. In Comparative Example 2, the tin content of the reinforcing layer and its comparison with the tin content of the copper foil substrate are low, leading to a corresponding decrease in room-temperature tensile strength. In Comparative Example 3, the increased thickness of the reinforcing layer leads to an increase in the average tin content in the electrolytic copper foil. Although the room-temperature tensile strength is improved, the room-temperature elongation and conductivity are significantly reduced. Therefore, by forming a reinforcing layer with a high tin content on the surface of the copper foil substrate and controlling the difference in tin content between the copper foil substrate and the reinforcing layer, as well as the thickness ratio of the reinforcing layer, it is possible to maintain a good balance between the tensile strength, elongation, and conductivity of the electrolytic copper foil while controlling the overall amount of tin introduced.

[0095] At the same time, such as Figure 3 and Figure 4 As shown, compared with Comparative Example 2, the tin content in the reinforcing layer of Example 1 is higher, resulting in a corresponding increase in room temperature tensile strength and a decrease in electrical conductivity. This indicates that the tin content in the reinforcing layer affects both the tensile strength and electrical conductivity of the electrolytic copper foil. Controlling the tin content in the reinforcing layer within an appropriate range is beneficial for balancing tensile strength and electrical conductivity.

[0096] Furthermore, the electrolytic copper foils prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to mechanical property tests after being kept at 180°C for 60 min. The test results are shown in Table 2.

[0097] Table 2. Test results of the mechanical properties of electrolytic copper foils obtained in Examples 1-5 and Comparative Examples 1-3 after heat treatment.

[0098]

[0099] Table 2 shows that the high tensile strength electrolytic copper foils obtained in Examples 1-5 maintained high tensile strength retention and corresponding elongation after being held at 180℃ for 60 minutes. Comparative Examples 1 and 2 showed relatively low tensile strength retention, while Comparative Example 3, although exhibiting a high tensile strength retention, showed a significant decrease in elongation after heat treatment. These results further demonstrate that the present invention, by controlling the tin content and the thickness ratio of the reinforcing layer in the copper foil substrate and reinforcing layer, is beneficial in improving the strengthening effect while maintaining the mechanical properties after heat treatment.

[0100] Furthermore, the thickness of the copper foil substrate, the thickness of the reinforcing layer, the total thickness of the electrolytic copper foil, and the percentage of the reinforcing layer thickness of the electrolytic copper foils prepared in Examples 1-5 and Comparative Examples 1-3 were statistically analyzed, and the results are shown in Table 3.

[0101] Table 3. Test results of the thickness and reinforcement layer thickness ratio of the electrolytic copper foil obtained in Examples 1-5 and Comparative Examples 1-3.

[0102]

[0103] As shown in Table 3, the reinforcing layer thickness of the high tensile strength electrolytic copper foils obtained in Examples 1-5 ranges from 5% to 18%. Specifically, the reinforcing layer thickness ratio in Examples 1-3 is 10%, while in Examples 4 and 5 it is 5% and 18%, respectively. Comparative Example 1 did not form a reinforcing layer, Comparative Example 2 had the same reinforcing layer thickness ratio as Example 1, and Comparative Example 3 increased its reinforcing layer thickness ratio to 25%. Combined with Table 1, it can be seen that while an excessively large reinforcing layer thickness ratio can improve tensile strength, it will reduce elongation and conductivity. Therefore, controlling the reinforcing layer thickness ratio within 5%-18% is beneficial for balancing the tensile strength, elongation, and conductivity of the electrolytic copper foil.

[0104] Those skilled in the art, upon reading this specification and implementing the invention, will conceive of other embodiments of the invention. This application is intended to cover variations, uses, or adaptations of the invention; common knowledge or conventional techniques in the art can be used in specific implementations without departing from the basic principles of the invention. The specification and embodiments are for illustrative purposes only, and the scope of protection of the invention is defined by the claims.

[0105] It should be understood that the present invention is not limited to the specific embodiments described above, and corresponding modifications and changes can be made without departing from the concept and scope of the claims.

Claims

1. A high tensile strength electrolytic copper foil, characterized in that, The high tensile strength electrolytic copper foil includes, along its thickness direction, a copper foil substrate and a reinforcing layer formed on the surface of the copper foil substrate. The copper foil substrate contains 300-500 ppm of tin, the reinforcing layer is a copper-tin alloy layer, the reinforcing layer contains 2200-4000 ppm of tin, and the ratio of the tin content in the reinforcing layer to the tin content in the copper foil substrate is (7-10):

1. The thickness of the reinforcing layer is 0.5-2.5 μm, and the thickness of the reinforcing layer accounts for 5%-18% of the total thickness of the high tensile electrolytic copper foil; The high tensile strength electrolytic copper foil has a room temperature tensile strength of 550-680 MPa, a room temperature elongation of 4.0%-8.0%, and an electrical conductivity of 90%-98% IACS.

2. The high tensile strength electrolytic copper foil according to claim 1, characterized in that, The average tin content in the high tensile electrolytic copper foil is 450-900 ppm.

3. The high tensile strength electrolytic copper foil according to claim 1, characterized in that, The high tensile strength electrolytic copper foil, after being kept at 180℃ for 60 minutes and cooled to room temperature, retains 82%-95% of its tensile strength and 3.5%-7.0% of its elongation.

4. A method for preparing high tensile strength electrolytic copper foil as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Prepare the first electrolyte, place the rotating cathode roller in the first electrolyte for continuous electrodeposition, so that copper ions and tin ions are deposited together, and a copper foil substrate with a tin content of 300-500ppm is formed on the surface of the rotating cathode roller. S2. While the copper foil substrate is still attached to the rotating cathode roller, the copper foil substrate is removed from the first electrolyte and its surface is brought into contact with a second electrolyte with a higher tin ion concentration than the first electrolyte. Electrodeposition continues, allowing copper ions and tin ions to be deposited together, forming a copper-tin alloy reinforcement layer with a tin content of 2200-4000 ppm on the surface of the copper foil substrate. S3. By adjusting the tin ion concentration in the first and second electrolytes and the electrodeposition conditions in the first and second stages, the ratio of tin content in the reinforcing layer to tin content in the copper foil substrate is made to be (7-10):1, and the thickness of the reinforcing layer is made to be 0.5-2.5 μm and account for 5%-18% of the total thickness of the obtained high tensile electrolytic copper foil; after the obtained high tensile electrolytic copper foil reaches the predetermined thickness, it is peeled off.

5. The method for preparing high tensile strength electrolytic copper foil according to claim 4, characterized in that, Both the first electrolyte and the second electrolyte include a copper source, a tin source, sulfuric acid, a chloride ion source, a polyether inhibitor, a sulfur-containing accelerator, and a nitrogen-containing leveling agent.

6. The method for preparing high tensile strength electrolytic copper foil according to claim 5, characterized in that, The copper source is copper sulfate, and the tin source is stannous sulfate; The chloride ion source is selected from at least one of hydrochloric acid, sodium chloride, and potassium chloride; The polyether inhibitor is selected from at least one of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer; The sulfur-containing accelerator is selected from at least one of disodium bis-(3-sulfopropyl)disulfide and 3-mercapto-1-propanesulfonate; The nitrogen-containing leveling agent is selected from at least one of polyethyleneimine and polyquaternary ammonium salt.

7. The method for preparing high tensile strength electrolytic copper foil according to claim 5, characterized in that, In the first electrolyte, Cu 2+ The concentration is 75-105 g / L, Sn 2+ The concentration of [unspecified substance] is 0.03-0.08 g / L, the concentration of H2SO4 is 90-120 g / L, and the concentration of Cl [unspecified substance] is [unspecified substance]. - The concentration of the first electrolyte is 15-30 mg / L, the concentration of the polyether inhibitor is 4-10 mg / L, the concentration of the sulfur-containing accelerator is 0.5-1.5 mg / L, the concentration of the nitrogen-containing leveling agent is 0.3-1.0 mg / L, and the temperature of the first electrolyte is 48-58℃.

8. The method for preparing high tensile strength electrolytic copper foil according to claim 5, characterized in that, In the second electrolyte, Cu 2+ The concentration is 75-100 g / L, Sn 2+ The concentration of [unspecified substance] is 0.25-0.7 g / L, the concentration of H2SO4 is 90-120 g / L, and the concentration of Cl [unspecified substance] is [unspecified substance]. - The concentration of the first electrolyte is 15-30 mg / L, the concentration of the polyether inhibitor is 2-6 mg / L, the concentration of the sulfur-containing accelerator is 1.0-3.0 mg / L, the concentration of the nitrogen-containing leveling agent is 0.5-1.5 mg / L, and the temperature of the second electrolyte is 48-58℃.

9. The method for preparing high tensile strength electrolytic copper foil according to claim 5, characterized in that, The second electrolyte and the Sn in the first electrolyte 2+ The concentration ratio of the second electrolyte to the first electrolyte is (5-15):1, the concentration ratio of the sulfur-containing accelerator in the second electrolyte to the first electrolyte is (1.5-4.0):1, and the concentration ratio of the polyether inhibitor in the second electrolyte to the first electrolyte is (0.1-0.8):

1.

10. The method for preparing high tensile strength electrolytic copper foil according to claim 4, characterized in that, The cathode current density when electrodepositing with the first electrolyte is 28-45 A / dm², and the cathode current density when electrodepositing with the second electrolyte is 35-58 A / dm². The ratio of the cathode current density when electrodepositing with the second electrolyte to the cathode current density when electrodepositing with the first electrolyte is (1.05-1.30):1.

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