Method for quantitatively controlling grain size of electro-deposition copper foil through power ultrasound

Abstract

The invention belongs to the technical field of electrolytic copper foils, and particularly relates to a method for quantitatively controlling the grain size of an electrodeposited copper foil through power ultrasound. According to the method, an ultrasonic field with a series of ultrasonic amplitudes is applied to an electrolyte for electro-deposition, and copper foils under different ultrasonic amplitudes are deposited on a cathode; and performing exponential fitting on the average grain size and the ultrasonic amplitude to obtain a formula I, and controlling the ultrasonic amplitude according to the formula I to perform electro-deposition to obtain the copper foil with the required average grain size. According to the method, the quantitative relation between the power ultrasonic characteristics and the grain size is combined, copper foil grain refinement is achieved by adjusting the ultrasonic amplitude, and the function correlation between the ultrasonic amplitude and the target grain size is established, so that accurate and controllable preparation of the copper foil grain structure is achieved, the uniformity of the grain size is improved, and the yield is improved. And the consistency and the stability of copper foil products are improved, and the method is suitable for preparing the grain-controllable self-supporting or carrier-attached type electrolytic copper foil. Formula I

Description

Technical Field

[0001] This invention belongs to the field of electrolytic copper foil technology, specifically relating to a method for quantitatively controlling the grain size of electrodeposited copper foil using power ultrasound. Background Technology

[0002] Copper foil, due to its excellent electrical and thermal conductivity and good ductility, has wide applications in electronics, communications, batteries, and many other fields. Especially in lithium-ion batteries and high-frequency, high-speed circuits, copper foil, as a key material, faces increasingly stringent performance requirements. The mechanical properties, electrical conductivity, and corrosion resistance of copper foil largely depend on its microstructure, particularly the size and distribution of its grains. Therefore, controlling the grain refinement of copper foil is crucial for improving its overall performance.

[0003] With technological advancements, there is a growing demand for thinner copper foils (e.g., <5µm). Currently, the mainstream industrial technology for copper foil fabrication employs electrodeposition. However, in traditional electrodeposition processes, grain growth is easily affected by factors such as ion diffusion rate, uneven current density distribution, and hydrogen evolution, leading to coarse and unevenly distributed grains, which in turn limits further improvements in copper foil performance. In the electrodeposition process, grain size directly determines key properties such as conductivity, mechanical properties, thermal stability, and interfacial bonding. Excessively large grains result in decreased mechanical strength, weakened grain boundaries, and reduced reliability; while excessively fine grains may lead to increased scattering of current-carrying electrons at grain boundaries, causing a decrease in conductivity, particularly significant in high-frequency electronic applications. Furthermore, uneven grain size can cause internal stress concentration and increased performance fluctuations within the copper foil, reducing product consistency and stability. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for quantitatively controlling the grain size of electrodeposited copper foil using power ultrasound. The present invention establishes a functional relationship between the ultrasonic amplitude and the copper foil grain size, and uses this functional relationship to back-calculate the ultrasonic amplitude corresponding to the copper foil with the required grain size, thereby achieving precise control of the copper foil grain size and improving the consistency and stability of copper foil products.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for quantitatively controlling the grain size of electrodeposited copper foil using power ultrasound, comprising the following steps: (1) Electrodeposition was performed by applying an ultrasonic field with a series of ultrasonic amplitudes in the electrolyte, and copper foils with different ultrasonic amplitudes were deposited on the cathode. (2) Obtain the average grain size of the copper foil under different ultrasonic amplitudes in step (1), and perform exponential fitting between the average grain size of the copper foil under different ultrasonic amplitudes and the series of ultrasonic amplitudes to obtain the functional relationship between the average grain size and the ultrasonic amplitude, as shown in Equation I: Equation I, where d The average grain size is expressed in µm. A The amplitude of the ultrasonic wave is expressed in µm. d 0 , k and d min These are the fitting parameters; (3) Set the ultrasonic amplitude of the ultrasonic field in step (1) to the ultrasonic amplitude corresponding to the average grain size of the desired copper foil as determined by formula I, and continue the electrodeposition in step (1) to obtain a copper foil with the desired average grain size.

[0006] Preferably, the frequency of the ultrasonic field is 20~100kHz; the series of ultrasonic amplitudes are any three or more point values ​​selected from 2~42µm; the ultrasonic field is a continuous ultrasonic field or an intermittent ultrasonic field.

[0007] Preferably, the current density of the electrodeposition is 0.5~100 A / dm³. 2 The current during the electrodeposition process is a constant current; the temperature of the electrolyte during the electrodeposition process is 20~60℃; and the electrodeposition time is 5~3600s.

[0008] Preferably, the equipment used for electrodeposition is an electrolytic cell; the distance between the anode and cathode in the electrolytic cell is 1~5cm.

[0009] Preferably, the electrolyte comprises a soluble copper salt, a conductive medium, and a solvent; the soluble copper salt comprises one or more of copper sulfate, copper chloride, and copper pyrophosphate; and the conductive medium comprises sulfuric acid and / or sodium chloride.

[0010] Preferably, the mass concentration of the soluble copper salt in the electrolyte is 70~80 g / L, and the mass concentration of the conductive medium is 90~100 g / L.

[0011] Preferably, the ultrasonic field generating device is an ultrasonic transmitting system; the ultrasonic transmitting system includes an ultrasonic power supply, an ultrasonic transducer, and an amplitude transformer.

[0012] Preferably, the lower ultrasonic emitting end of the amplitude transformer is located near the cathode and is directly inserted into the electrolyte; the diameter of the lower ultrasonic emitting end of the amplitude transformer is >5mm; and the distance between the lower ultrasonic emitting end of the amplitude transformer and the cathode is <10cm.

[0013] Preferably, the thickness of the copper foil is 0.5~20µm.

[0014] Preferably, the average grain size of the copper foil is 0.3~2μm.

[0015] This invention provides a method for quantitatively controlling the grain size of electrodeposited copper foil using power ultrasound, comprising the following steps: (1) Electrodeposition was performed by applying an ultrasonic field with a series of ultrasonic amplitudes in the electrolyte, and copper foils with different ultrasonic amplitudes were deposited on the cathode. (2) Obtain the average grain size of the copper foil under different ultrasonic amplitudes in step (1), and perform exponential fitting between the average grain size of the copper foil under different ultrasonic amplitudes and the series of ultrasonic amplitudes to obtain the functional relationship between the average grain size and the ultrasonic amplitude, as shown in Equation I: Equation I, where d The average grain size is expressed in µm. A The amplitude of the ultrasonic wave is expressed in µm. d 0 , k and d min These are the fitting parameters; (3) Set the ultrasonic amplitude of the ultrasonic field in step (1) to the ultrasonic amplitude corresponding to the average grain size of the desired copper foil as determined by formula I, and continue the electrodeposition in step (1) to obtain a copper foil with the desired average grain size.

[0016] This invention combines the quantitative relationship between power ultrasonic characteristics and grain size, achieving copper foil grain refinement by adjusting the ultrasonic amplitude, and establishing a functional correlation between ultrasonic amplitude and target grain size. This enables precise and controllable fabrication of the copper foil grain structure, improving grain size uniformity and enhancing the consistency and stability of copper foil products. This method is suitable for preparing self-supported or carrier-type electrolytic copper foil with controllable grain size, and can be widely used in lithium battery current collectors, high-frequency circuits, and precision electronic material manufacturing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the device used in the method for controlling the grain size of copper foil in the embodiment, where (a) is the side, (b) is the top, 1-amplifier rod, 2-electrolytic cell, 3-cathode, 4-anode; Figure 2 This is a grain distribution diagram of the self-supporting copper foil under different ultrasonic amplitudes in Example 1; Figure 3 This is a grain distribution diagram of the copper foil carrier under different ultrasonic amplitudes in Example 2. Detailed Implementation

[0018] This invention provides a method for quantitatively controlling the grain size of electrodeposited copper foil using power ultrasound, comprising the following steps: (1) Electrodeposition was performed by applying an ultrasonic field with a series of ultrasonic amplitudes in the electrolyte, and copper foils with different ultrasonic amplitudes were deposited on the cathode. (2) Obtain the average grain size of the copper foil under different ultrasonic amplitudes in step (1), and perform exponential fitting between the average grain size of the copper foil under different ultrasonic amplitudes and the series of ultrasonic amplitudes to obtain the functional relationship between the average grain size and the ultrasonic amplitude, as shown in Equation I: Equation I, where d The average grain size is expressed in µm. A The amplitude of the ultrasonic wave is expressed in µm. d 0 , k and d min These are the fitting parameters; (3) Set the ultrasonic amplitude of the ultrasonic field in step (1) to the ultrasonic amplitude corresponding to the average grain size of the desired copper foil as determined by formula I, and continue the electrodeposition in step (1) to obtain a copper foil with the desired average grain size.

[0019] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0020] Step (1): In this invention, an ultrasonic field with a series of ultrasonic amplitudes is applied to the electrolyte for electrodeposition, and copper foil with different ultrasonic amplitudes is deposited on the cathode.

[0021] In one embodiment, the electrodeposition equipment is an electrolytic cell; the cathode material is a conductive substrate; the conductive substrate includes stainless steel plate, industrial pure titanium plate, nickel sheet, copper foil, or a conductively treated substrate, specifically an industrial pure titanium plate; the conductively treated substrate includes glass or a polymer film; the polymer film is a polyimide (PI) film or a PET carbon film; the glass is ITO glass; the conductive treatment includes metal sputtering or surface coating with a conductive coating, specifically a metal sputtering conductive coating; the metal sputtering is vacuum sputtering of a copper layer; the surface coating with a conductive coating is chemical plating or electroplating, specifically chemical plating; the conductive coating includes a conductive polymer coating or a carbon-based coating, specifically a conductive polymer coating; the cathode thickness is 0.1~3mm, specifically 3mm; the titanium plate has good conductivity, mechanical strength, and electrolytic stability.

[0022] In one embodiment, the cathode is prepared by cutting the cathode material to a size suitable for the electrolytic cell, and then sequentially performing polishing, a first cleaning, activation treatment, and a second cleaning. The polishing is performed mechanically using sandpaper or polishing paste. The sandpaper is of grit 1000-3000, specifically grit 2000 in this embodiment. The polishing paste is micro-alumina. The micro-alumina has a particle size of 0.5-2.5µm, specifically 1-2µm in this embodiment. The first cleaning is performed by rinsing with water followed by ultrasonic cleaning. The water is deionized water. The ultrasonic cleaning has an ultrasonic power of [missing information]. The W power is 100~1000W, specifically 500~800W in this embodiment; the temperature is 20~30℃, specifically 25℃ in this embodiment; the time is 10~15min, specifically 10min in this embodiment; the activation treatment involves immersing the cathode material after the first cleaning in a sulfuric acid solution; the concentration of the sulfuric acid solution is 5~10wt%, specifically 10wt% in this embodiment; the activation treatment time is 1~5min, specifically 3min in this embodiment; the second cleaning involves rinsing with deionized water until the pH of the effluent is 6.5~7.5, specifically 7.0 in this embodiment. Polishing can remove the oxide layer and mechanical stress layer on the surface of the cathode material. The first cleaning can remove residual particles and organic contaminants on the surface of the cathode material. The activation treatment helps to remove the natural oxide film on the surface of the cathode material, enhances its surface roughness and activity, thereby improving the initial nucleation density of copper and the adhesion of the deposited layer.

[0023] In one embodiment, the anode in the electrolytic cell is made of either an insoluble inert anode or a soluble copper anode, specifically an insoluble inert anode in this embodiment; the insoluble inert anode is an iridium-tantalum-titanium electrode; the iridium-tantalum-titanium electrode is an iridium-tantalum-titanium coated titanium plate. The anode material is selected based on the stability of the electrodeposition system and the requirements for the metal source. The anode used in this invention has good electrochemical stability, corrosion resistance, and electrical conductivity.

[0024] In one embodiment, the surface area of ​​the anode is greater than or equal to the surface area of ​​the cathode; before electrodeposition, the method further includes: sequentially washing the anode with water and acid; the water washing is deionized water rinsing; the acid used for acid washing is sulfuric acid solution; the concentration of the sulfuric acid solution is 5~10wt%, specifically 5wt% in this embodiment; the acid washing temperature is 40~60℃, specifically 50℃ in this embodiment, and the time is 1~5min, specifically 3min in this embodiment; after water washing, the method further includes: replacing acid washing with acetone cleaning.

[0025] In this invention, the anode specifications are matched with the cathode, and the surface area of ​​the anode is greater than or equal to the surface area of ​​the cathode to ensure uniform electric field distribution. Before use, the anode should be rinsed with deionized water and, depending on the specific circumstances, surface acid washing can be performed to remove oxidative contaminants accumulated during transportation and storage.

[0026] In one implementation, the electrode distance between the anode and cathode is 1-5 cm, and in a specific embodiment, it is 2-3 cm. This electrode distance allows for a more uniform electric field distribution, ensuring uniform deposition of copper ions across the entire cathode surface.

[0027] In one embodiment, the electrolyte is a water-soluble electrolyte containing copper ions. Another embodiment includes a soluble copper salt, a conductive medium, and a solvent. The soluble copper salt includes one or more of copper sulfate (CuSO4), copper chloride (CuCl2), and copper pyrophosphate (K2CuP2O7), with copper sulfate being a specific example. The conductive medium includes sulfuric acid (H2SO4) and / or sodium chloride (NaCl), with sulfuric acid being a specific example. The solvent includes water, or a mixture of water and ethanol, with water being a specific example. The mass concentration of the soluble copper salt in the electrolyte is 70-80 g / L, with 80 g / L in a specific example, and the mass concentration of the conductive medium is 90-100 g / L, with 100 g / L in a specific example.

[0028] When using copper sulfate, the copper ion release rate is stable, which is suitable for obtaining a dense, fine-grained structure; in copper chloride, Cl... -The presence of [a substance] promotes selective adsorption on crystal faces, which is beneficial for refining grains and forming specific textures; the copper pyrophosphate system is suitable for neutral to weakly alkaline environments. Sulfuric acid provides a strongly acidic environment, which helps to form dense crystals and improve the conductivity of the electrolyte; sodium chloride contains chloride ions (Cl...). - It can participate in grain regulation and promote grain refinement.

[0029] In one embodiment, the electrolyte further includes: additives; the additives include one or more of brighteners, accelerators, inhibitors, adsorbents, complexing agents, and synergists, specifically brighteners and synergists in this embodiment; the brightener includes one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), and polyglycerol, specifically polyethylene glycol in this embodiment; the number average molecular weight of the polyethylene glycol (PEG) is 200-1000, specifically 300-500 in this embodiment; the amount of brightener added to the electrolyte is 50-500 mg / L, specifically... The concentration in the example is 100-300 mg / L; the accelerator includes sodium dimercaptopropanesulfonate (SPS) and / or 3-mercapto-1-propanesulfonic acid (MPS), with sodium dimercaptopropanesulfonate being used in a specific embodiment; the amount of the accelerator added to the electrolyte is 5-20 mg / L, with 10-15 mg / L in a specific embodiment; the inhibitor includes carboxymethyl cellulose (CMC) and / or polyacrylamide (PAM), with carboxymethyl cellulose being used in a specific embodiment; the amount of the inhibitor added to the electrolyte is 10-200 mg / L, with 20-100 mg / L in a specific embodiment; the synergist is a chloride-containing (Cl... - The substance containing chloride ions (Cl) - The substances include NaCl and / or KCl, with NaCl being used in a specific embodiment; the amount of the synergist added to the electrolyte is 10~100 mg / L, with 20~50 mg / L being used in a specific embodiment; the adsorption additives include imidazole substances and / or collagen, with collagen being used in a specific embodiment; the imidazole substances include one or more of 2-methylimidazole, 2-mercaptoimidazole, 1,2-dimethylimidazole, benzylimidazole and ethylimidazole, with 2-methylimidazole being used in a specific embodiment; the amount of the adsorption additives added to the electrolyte is 1~20 mg / L, with 5~10 mg / L being used in a specific embodiment; the complexing agent is pyrophosphate and / or an amine complexing agent; the amine complexing agent includes one or more of ethylenediamine, triethanolamine and diethylenetriamine, with triethanolamine being used in a specific embodiment; the amount of the complexing agent added to the electrolyte is 50~2000 mg / L, with 200~1000 mg / L being used in a specific embodiment.

[0030] This invention incorporates additives into the electrolyte to adjust the morphology and properties of the deposited copper layer. These additives improve the grain structure, surface smoothness, and physical properties of the deposited copper foil. Brighteners suppress tip deposition, smooth the copper foil surface, and refine the grains. Accelerators increase the electrodeposition rate, accelerate nucleus formation, and regulate grain size. Inhibitors control ion migration and deposition rates, preventing the formation of coarse grains. Synergists often work synergistically with other additives to enhance smoothness and grain refinement. In this invention, multiple additives work together to suppress abnormal grain growth and improve the smoothness and density of the copper layer.

[0031] When the soluble copper salt is copper sulfate, the additives in the electrolyte include a brightener, a synergist, and an accelerator; the brightener is polyethylene glycol (PEG); the synergist is a chloride-containing (Cl...) ion... - The electrolyte system contains a substance; the accelerator is 3-mercapto-1-propanesulfonic acid (MPS); this electrolyte system is suitable for the deposition of high-brightness copper foil. When the soluble copper salt is copper chloride, the additives in the electrolyte include adsorption additives, and this electrolyte system is used to regulate growth selectivity. When the soluble copper salt is copper pyrophosphate, the additives in the electrolyte are complexing agents, and this electrolyte system is suitable for neutral to weakly alkaline environments, suitable for the low-stress deposition requirements of microelectronic devices.

[0032] In one embodiment, the electrolyte is prepared by mixing a soluble copper salt, a conductive medium, and a solvent, followed by magnetic stirring, then allowing it to stand and filtering. The magnetic stirring temperature is room temperature to 60°C, specifically 30 to 50°C in this embodiment; the stirring speed is 200 to 600 rpm, specifically 400 rpm in this embodiment; and the stirring time is 10 to 60 minutes, specifically 30 to 50 minutes in this embodiment. The standing time is 10 to 30 minutes, specifically 20 minutes in this embodiment. The pore size of the filter membrane used for filtration is 0.22 to 1 µm, specifically 0.5 µm in this embodiment. This invention ensures the cleanliness and stability of the electrolyte system by completely dissolving the soluble copper salt and conductive medium through magnetic stirring and removing impurities or suspended particles through static filtration.

[0033] In one implementation, the ultrasonic field generating device is an ultrasonic transmitting system; the ultrasonic transmitting system includes an ultrasonic power supply, an ultrasonic transducer, and an amplitude transformer; the ultrasonic transducer is installed on the top of the electrolytic cell, and is mechanically connected to the amplitude transformer to form a complete energy conduction path; the lower ultrasonic transmitting end of the amplitude transformer is located near the cathode and is directly inserted into the electrolyte; the diameter of the lower ultrasonic transmitting end of the amplitude transformer is >5mm, and in a specific embodiment is ≥15mm; the amplitude transformer is made of titanium alloy, stainless steel, or quartz, and in a specific embodiment is titanium alloy; the amplitude transformer is made of a material with excellent acoustic performance and corrosion resistance, and the material of the amplitude transformer cannot chemically react with the electrolyte.

[0034] In one implementation, the distance between the lower ultrasonic transmitting end of the amplitude transformer and the cathode is <10cm, specifically 0.5~2cm in this embodiment. The lower ultrasonic transmitting end of the amplitude transformer is inserted into the electrolyte and brought close to the deposition area (cathode). The distance d between the transmitting end and the cathode has a significant impact on the sound pressure field distribution and cavitation effect. This invention utilizes the aforementioned distance between the transmitting end and the cathode to achieve maximum local perturbation and the most effective grain refinement. Too close a distance may lead to local cavitation and damage to the deposition morphology, while too far a distance will attenuate the ultrasonic energy and weaken the effect.

[0035] As one implementation, when the material of the amplitude transformer may react with the electrolyte, a protective coating is provided on the outer surface of the amplitude transformer. The material of the protective coating includes one or more of silicon dioxide, alumina, polytetrafluoroethylene, and polyvinylidene fluoride, with silicon dioxide or alumina being used in a specific embodiment. The thickness of the protective coating is 5~50µm, with 10~20µm being used in a specific embodiment. The protective coating does not react with the electrolyte, and the adhesion level between the protective coating and the amplitude transformer reaches HF1 level, with a peel strength greater than 1. σ The σ The calculation formula is: σ = ρ · h ·(2π f ) 2 · A 0, where: ρ Density (kg / m³) of the material used for the protective coating; h The thickness (m) of the protective coating; f The ultrasonic vibration frequency (Hz) of the ultrasonic field; A 0 represents the ultrasonic amplitude (µm).

[0036] The protective coating in this invention is designed to prevent corrosion of the amplitude transformer in a highly acidic electrolyte, thereby ensuring the structural integrity and energy transfer efficiency of the amplitude transformer during long-term operation and guaranteeing efficient ultrasonic energy conduction. The protective coating used in this invention is chemically stable with the electrolyte, and its adhesion strength to the amplitude transformer body exceeds the requirements of the amplitude and frequency used. By applying a protective coating with high bonding strength to the surface of the amplitude transformer, this invention not only effectively prevents direct corrosion of the amplitude transformer substrate by the electrolyte but also maintains structural integrity and adhesion stability under high-frequency ultrasonic vibration conditions. This enables long-term stable use of the amplitude transformer in highly corrosive environments, significantly improving its durability and service life, and reducing equipment maintenance frequency and costs.

[0037] Figure 1 This is a schematic diagram of the apparatus used in the method for controlling the grain size of copper foil in the embodiment, where (a) is the side view and (b) is the top view. From Figure 1 As can be seen, the amplitude transformer is inserted into the electrolyte of the electrolytic cell, located between the cathode and the anode.

[0038] In one implementation, the frequency of the ultrasonic field is 20~100kHz, specifically 20~50kHz in this embodiment; the series of ultrasonic amplitudes are any three or more points selected from 2~42µm, specifically 18, 30, and 42µm in this embodiment; the ultrasonic field is either a continuous ultrasonic field or an intermittent ultrasonic field, specifically a continuous ultrasonic field in this embodiment. In this invention, the ultrasonic field is a continuous ultrasonic field to maintain a stable acoustic environment. The frequency of the ultrasonic field affects the cavitation threshold and cavitation size distribution; lower frequencies (20~40kHz) are beneficial for enhanced cavitation intensity and contribute to grain refinement; higher frequencies are suitable for more precise and stable control.

[0039] As one implementation method, the specific process of electrodeposition is as follows: The cathode and anode are placed in an electrolytic cell; the electrode distance between the cathode and anode is adjusted to maintain the electrolyte level 2-3 cm above the top of the electrodes; the electrolytic cell is placed in a constant-temperature water bath; the electrolyte temperature is controlled to be stable; electricity is applied; and the ultrasonic emission system is started synchronously to perform electrodeposition; the current density of the electrodeposition is 0.5-100 A / dm³. 2 In specific embodiments, the value is 5~80 A / dm. 2 The current during the electrodeposition process is a constant current; the temperature of the electrolyte during the electrodeposition process is 20~60℃, specifically 25~40℃ in this embodiment; the electrodeposition time is 5~3600s, specifically 30~600s in this embodiment. The electrodeposition time t refers to the continuous deposition time from power-on to power-off, which depends on the expected target thickness of the copper foil and the deposition rate.

[0040] During electrodeposition, current and ultrasound are applied simultaneously to the electrolytic cell system, forming an acoustic-electric coupling deposition environment. This helps to suppress hydrogen evolution, enhance the migration rate of copper ions, and significantly affect the nucleation and growth behavior of copper.

[0041] When using a high-concentration copper salt or a strong complexing additive system in the electrolyte, the current density can be appropriately reduced and the electrolyte temperature increased to prevent dendrite growth or surface roughness. When the additive concentration is high, the electrodeposition time should be appropriately extended and the current density reduced to avoid defects caused by excessively rapid deposition.

[0042] When the electrolytic cell is a small experimental platform and the distance between the cathode and anode is less than 2 cm, a low current density (<20 A / dm²) is suitable. 2 When the electrolytic cell system is equipped with efficient stirring or ultrasonic assistance, it can withstand higher current density and shorter deposition time.

[0043] When the target is to prepare submicron grain copper foil, a higher current density (e.g., 8~12 A / dm²) is selected. 2 To promote rapid nucleation; when preparing copper foil with good structural uniformity and dense surface, a moderate electrolyte temperature (30~40℃) and a suitable deposition rate are selected to adjust the grain growth rate.

[0044] This invention employs a current density within the aforementioned range, which can both increase the supersaturation of copper ions and enhance the nucleation rate, thus facilitating the formation of smaller and more uniform grains, and avoid hydrogen evolution or dendrite growth caused by excessively high current, thereby compromising structural integrity. The electrolyte temperature within the aforementioned range can both increase the diffusion rate of copper ions, promoting the growth and expansion of copper foil grains and tending to form larger grains, and delay grain growth, thus facilitating grain refinement, and avoiding defects and decreased deposition efficiency caused by excessively low temperatures. Deposition time directly determines the thickness of the copper foil; the grain structure is more susceptible to the influence of initial conditions in the early deposition stages. Extending the deposition time will promote grain growth and even secondary recrystallization, leading to an increase in grain size. Therefore, if the goal is a fine-grained copper foil, deposition should be terminated within the time range before the grain size has significantly increased.

[0045] Step (2): The present invention obtains the average grain size of the copper foil under different ultrasonic amplitudes in step (1), and performs exponential fitting between the average grain size of the copper foil under different ultrasonic amplitudes and the series of ultrasonic amplitudes to obtain the functional relationship between the average grain size and the ultrasonic amplitude, as shown in Equation I: Equation I, where d The average grain size is expressed in µm. A The amplitude of the ultrasonic wave is expressed in µm. d 0 , kand d min These are the fitting parameters.

[0046] As one implementation method, the process of obtaining the average grain size of the copper foil is as follows: after electrodeposition, the power supply of the electrolytic cell and the ultrasonic field generating device are immediately turned off, the cathode is taken out of the electrolytic cell, and then it is cleaned, dehydrated and dried in sequence. Then, the copper foil is peeled off from the cathode to obtain free copper foil. The free copper foil is examined by scanning electron microscopy to obtain the average grain size of the copper foil. The cleaning is done by rinsing with deionized water. The solvent used for the dehydration treatment is ethanol. The drying temperature is 50~80℃, specifically 60℃ in this embodiment, and the drying time is 0.5~5min, specifically 1~3min in this embodiment. The drying equipment is an oven. The present invention does not have a special limitation on the peeling method, and blades or other mechanical means can be used.

[0047] In one implementation, the ultrasonic amplitude is detected by an instrument capable of measuring periodic displacement of 20~100kHz, specifically a laser vibrometer; the specific measurement process of the ultrasonic amplitude is as follows: the ultrasonic amplitude under different power supply output driving voltages in the ultrasonic field generating device is measured using an instrument capable of measuring periodic displacement of 20~100kHz. As one implementation, the functional relationship between the average grain size and the ultrasonic amplitude is as follows: .

[0048] The effects of copper foil thickness on grain size are mainly as follows: Copper foil thickness indirectly regulates grain size by influencing grain growth time and space: 1. Grain growth space effect: In thin copper foil (<5µm), the lateral and vertical growth space of grains is limited, and the grain size depends more on the initial nucleation stage conditions, usually maintaining a finer and more uniform structure. 2. Deposition time and recrystallization: When the copper foil thickness is large (>10µm), prolonged deposition time may lead to grain growth and preferred orientation evolution along the thickness direction, and even local coarsening or an increase in bicrystal structure.

[0049] After electrodeposition for a period of time t, a copper foil with a target thickness h is formed, and the grain structure is refined. t and h can be flexibly set according to the product design. The copper foil can be a self-supporting structure or a carrier structure, which is suitable for a variety of high-performance electronic application scenarios.

[0050] In this invention, a predictable functional relationship exists between the average grain size of the copper foil and the applied ultrasonic amplitude. This functional relationship can be obtained by conducting a series of exploratory deposition experiments beforehand and used to guide actual process parameter tuning, thereby achieving reverse derivation of the target grain size and selection of amplitude parameters. This strategy improves the repeatability and control efficiency of grain structure control, offering significant advantages. The ultrasonic amplitude selection method includes: ① measuring the ultrasonic amplitude response under different ultrasonic driving voltages using a laser vibrometer or similar instrument; ② obtaining the fitting functional relationship between the ultrasonic amplitude and grain size based on preliminary experiments; ③ inputting the target grain size d and deriving the required ultrasonic amplitude A through the fitting relationship; ④ applying this amplitude during the actual deposition process to achieve precise control of the grain structure.

[0051] In step (3), the ultrasonic amplitude of the ultrasonic field in step (1) is set to the ultrasonic amplitude corresponding to the average grain size of the desired copper foil as determined by formula I, and the electrodeposition in step (1) is continued to obtain a copper foil with the desired average grain size.

[0052] As one implementation method, the ultrasonic amplitude corresponding to the average grain size of the desired copper foil, as determined according to Formula I, is any value within the range of >0 and ≤42µm, specifically 2~42µm in this embodiment.

[0053] In one embodiment, the thickness of the copper foil is 0.5~20µm; in another embodiment, it is 1~10µm; and in a specific embodiment, it is 5µm. The thickness h of the copper foil refers to the vertical thickness of the electrodeposited copper layer, which can be adjusted according to different application requirements: for copper foil used in electronic devices such as high-frequency flexible circuits, the thickness is 2~5µm; for battery current collectors or support-type copper foil, the thickness is 5~20µm; for ultra-thin self-supporting copper foil, such as applications <2µm, short-time high-current-density electrodeposition can also be used.

[0054] In one embodiment, the average grain size of the copper foil is 0.3~2μm, and in a specific embodiment it is 0.4~1μm.

[0055] In the electrodeposition process described in step (3), the electrolyte, electrolytic cell and ultrasonic field settings are the same as in step (1), and will not be repeated here.

[0056] The ultrasonic amplitude of this invention A Based on target grain size d The selection is based on the preset parameters and the function relationship established in the pre-experiment.

[0057] This invention prepares copper foil using ultrasound-assisted electrodeposition, resulting in a uniform and dense grain structure with strong mechanical properties and bonding strength, making it suitable for manufacturing high-end electronic components such as lithium batteries and integrated circuits. By establishing a functional relationship between ultrasonic control and grain size, this invention achieves tunable and precise control over the microstructure of the copper foil; it avoids reliance on empirical parameter tuning, improving the repeatability and engineering adaptability of the preparation process; and it simplifies the process, reduces costs, and enhances stability without altering the conventional electrolyte system, demonstrating significant industrial application value.

[0058] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1 (1) Electrolyte preparation The electrolyte for copper electrodeposition was prepared using copper sulfate (CuSO4·5H2O) and sulfuric acid (H2SO4) as the main components, with water as the solvent. The mass concentration of copper sulfate was 80 g / L, and the mass concentration of sulfuric acid was 100 g / L. Additives were added to the electrolyte: polyethylene glycol (PEG, number average molecular weight 400, added at 200 mg / L) and sodium chloride (added at 20 mg / L). After preparation, the electrolyte was completely dissolved by magnetic stirring at 30°C (400 rpm for 30 min), and after standing for 20 min, it was filtered through a 0.5 µm filter membrane to remove impurities or suspended particles, ensuring the system was clean and stable. (2) Electrolytic cell configuration A 3mm thick industrial pure titanium plate was selected as the cathode substrate for electrodeposition. The titanium plate was cut to the size suitable for the electrolytic cell, mechanically polished with 2000 grit sandpaper, thoroughly rinsed with deionized water, and ultrasonically cleaned with 800W power for 10 minutes. After cleaning, the titanium plate was immersed in a 10wt% dilute sulfuric acid solution for activation treatment for 3 minutes. After activation, it was immediately rinsed thoroughly with deionized water until the pH value of the effluent was 7.0. An iridium-tantalum-titanium coated titanium plate is used as an insoluble anode. The anode plate specifications are matched with the cathode (titanium substrate), and its surface area should be equal to or slightly larger than that of the cathode. Before use, the anode is rinsed with deionized water, acid-washed, and cleaned with 5wt% dilute sulfuric acid solution at 50℃ for 3 minutes. The distance between the anode and cathode is set to 3 cm. (3) Ultrasonic transmitting system setup An ultrasonic transmitting system is arranged with its transmitting end located near the deposition area and inserted into the electrolyte. The transmitting end is 2 cm away from the cathode. The ultrasonic transmitting system consists of an ultrasonic power supply, an ultrasonic transducer, and an amplitude transformer. The ultrasonic transducer is installed on the top of the electrolytic cell and is connected to the amplitude transformer through a mechanical connection to form a complete energy conduction path. The lower ultrasonic transmitting end (15 mm in diameter) of the amplitude transformer is directly inserted into the electrolyte and is made of titanium alloy. The ultrasonic generator operates at a frequency of 20kHz, and the ultrasonic transmitter amplitude ranges from 12 to 42µm. The ultrasonic system operates continuously to maintain a stable acoustic field environment.

[0060] (4) Electrodeposition process Place the treated cathode and anode in the electrolytic cell, adjust the electrode distance to the set value, keep the electrolyte level 2-3 cm above the top of the electrodes, and place the electrolytic cell in a 40℃ constant temperature water bath to control the solution temperature to be stable. After powering on, a constant current density of 8.0 A / dm² was applied, and the ultrasonic system was started to work synchronously. The deposition time was 150 s. During the electrodeposition process, the current and ultrasound were applied to the system at the same time, forming an acoustic-electric coupling deposition environment, resulting in an electrodeposited copper foil with a thickness of 5 μm. The ultrasonic amplitudes of 0, 18, 30 and 42 µm under different ultrasonic driving voltages were measured using a laser vibrometer. (5) Copper foil collection and testing After deposition, immediately turn off the power and ultrasonic system, remove the titanium substrate from the electrolytic cell, rinse the deposited copper layer thoroughly with deionized water to remove electrolyte residue, and then quickly dehydrate it with ethanol. After drying it in a 60°C oven for 1 minute, use a blade to peel the copper foil off the titanium plate to obtain free copper foil. Scanning electron microscopy (EBSD) observations showed that the average grain size decreased from 2 μm without sonication to approximately 0.6 μm, and the grain distribution was more uniform, indicating significant grain refinement.

[0061] The ultrasonic amplitude and grain size data are shown in Table 1 below.

[0062] Table 1. Average grain size of copper foil under different ultrasonic amplitudes

[0063] Based on the above experimental results, the average grain size can be obtained. d With ultrasonic amplitude A The trend approximately decreases exponentially. Using exponential fitting, we obtain:

[0064] in, d Average grain size (µm). AThe amplitude of the ultrasonic wave is (µm). d 0 , k , d min The fitting parameters are as follows:

[0065] This invention can derive the optimal amplitude setting by inversely based on the required grain size and the function between the ultrasonic amplitude and the copper foil grain size, thereby achieving structurally controllable copper foil deposition.

[0066] Figure 2 This is a grain distribution diagram of the self-supporting copper foil under different ultrasonic amplitudes in Example 1. From... Figure 2 It can be seen that, under conditions without the application of ultrasound (static), the deposited copper layer exhibits a typical columnar crystal structure with coarse grains and concentrated orientation, showing a growth characteristic dominated by gradual nucleation.

[0067] When the amplitude is 18 μm, the grain morphology begins to show a trend of refinement, and some areas have already shown the prototype of equiaxed crystals, indicating that low-intensity ultrasound has a certain stimulating effect on the nucleation process.

[0068] When the amplitude was further increased to 30 μm, the grains were significantly refined and the structure became more uniform and dense, indicating that the strong cavitation and microfluidic effects significantly promoted the occurrence of instantaneous nucleation and broke the dominant direction of grain growth under local perturbation.

[0069] Under the condition of 42 μm amplitude, the deposited copper layer exhibits a highly refined equiaxed crystal structure, with significantly reduced grain size, diversified orientation, and the most compact overall structure.

[0070] In summary, this invention achieves microstructure control of electrodeposited copper foil by regulating the amplitude of ultrasonic waves. In particular, under high amplitude conditions, nanoscale equiaxed copper foil is effectively obtained, which is suitable for preparing high-strength, high-density metallic materials.

[0071] Example 2 The difference from Example 1 is that a 35µm commercial copper foil is used as the substrate, and a nickel layer is pre-deposited on its surface as the initial deposition layer. The electroplating solution used contains only a basic plating solution of copper sulfate, sulfuric acid and sodium chloride.

[0072] After deposition, scanning electron microscopy (EBSD) showed that the average grain size decreased from 2 μm without sonication to about 0.5 μm, and the grain distribution was more uniform, indicating that the grains were significantly refined.

[0073] Figure 3 This is a grain distribution diagram of the copper foil carrier under different ultrasonic amplitudes in Example 2. From... Figure 3It can be seen that the overall trend of change is the same as that in Example 1, indicating that the method of the present invention has good versatility, is applicable to different matrix materials and electrolyte systems, and can effectively achieve grain refinement and uniform distribution.

[0074] Comparative Example 1 The difference from Example 1 is that an ultrasonic field is not applied during the electrodeposition process.

[0075] Comparative Example 2 The difference from Example 1 is that traditional mechanical stirring was used instead of ultrasonic assistance during the electrodeposition process. Although it has a certain effect on promoting electrolyte convection, the degree of grain refinement is limited, with an average grain size of about 1.5µm, and the grain morphology is uneven, with obvious columnar crystals. The improvement in mechanical properties is limited, and it cannot achieve the uniform fine grain effect of ultrasonic assistance.

[0076] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for quantitatively controlling the grain size of electrodeposited copper foil using power ultrasound, characterized in that, Includes the following steps: (1) Electrodeposition was performed by applying an ultrasonic field with a series of ultrasonic amplitudes in the electrolyte, and copper foils with different ultrasonic amplitudes were deposited on the cathode. (2) Obtain the average grain size of the copper foil under different ultrasonic amplitudes in step (1), and perform exponential fitting between the average grain size of the copper foil under different ultrasonic amplitudes and the series of ultrasonic amplitudes to obtain the functional relationship between the average grain size and the ultrasonic amplitude, as shown in Equation I: Equation I, where d The average grain size is expressed in µm. A The amplitude of the ultrasonic wave is expressed in µm. d 0 , k and d min These are the fitting parameters; (3) Set the ultrasonic amplitude of the ultrasonic field in step (1) to the ultrasonic amplitude corresponding to the average grain size of the desired copper foil as determined by formula I, and continue the electrodeposition in step (1) to obtain a copper foil with the desired average grain size.

2. The method according to claim 1, characterized in that, The frequency of the ultrasonic field is 20~100kHz; the amplitude of the series of ultrasonic waves is any three or more point values ​​selected from 2~42µm; the ultrasonic field is a continuous ultrasonic field or an intermittent ultrasonic field.

3. The method according to claim 1, characterized in that, The current density for electrodeposition is 0.5~100 A / dm³. 2 The current during the electrodeposition process is a constant current; the temperature of the electrolyte during the electrodeposition process is 20~60℃; and the electrodeposition time is 5~3600s.

4. The method according to claim 1, characterized in that, The equipment used for electrodeposition is an electrolytic cell; the distance between the anode and cathode in the electrolytic cell is 1~5cm.

5. The method according to claim 1, characterized in that, The electrolyte comprises a soluble copper salt, a conductive medium, and a solvent; the soluble copper salt comprises one or more of copper sulfate, copper chloride, and copper pyrophosphate; the conductive medium comprises sulfuric acid and / or sodium chloride.

6. The method according to claim 5, characterized in that, The electrolyte contains 70-80 g / L of soluble copper salt and 90-100 g / L of conductive medium.

7. The method according to claim 1, characterized in that, The device for generating the ultrasonic field is an ultrasonic transmitting system; the ultrasonic transmitting system includes an ultrasonic power supply, an ultrasonic transducer, and an amplitude transformer.

8. The method according to claim 7, characterized in that, The lower ultrasonic emitting end of the amplitude transformer is located near the cathode and is directly inserted into the electrolyte; the diameter of the lower ultrasonic emitting end of the amplitude transformer is >5mm; the distance between the lower ultrasonic emitting end of the amplitude transformer and the cathode is <10cm.

9. The method according to claim 1, characterized in that, The thickness of the copper foil is 0.5~20µm.

10. The method according to claim 1 or 9, characterized in that, The average grain size of the copper foil is 0.3~2μm.

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