A method for the production of high purity metal starting sheets for electrodeposition

Abstract

This invention relates to the field of hydrometallurgical electrowinning technology, specifically to a method for preparing large-area high-purity metal starter sheets for electrowinning production. This invention fundamentally solves the inherent defects of traditional starter sheets. Starter sheets prepared by traditional electrowinning methods accumulate deformation energy internally, easily leading to warping, edge cracking, and other problems. This invention, however, uses CVD technology to deposit metal at the atomic level, resulting in a flat starter sheet free from warping and cracking. Simultaneously, it significantly simplifies the preparation process. Traditional processes require more than ten steps, with a single sheet preparation cycle exceeding 48 hours; this invention requires only three steps, shortening the cycle to approximately 18 hours. Furthermore, it achieves complete peeling of large-area metal layers with a success rate exceeding 98%, and is applicable to various high-value metals such as cobalt, gold, silver, and platinum.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical electrowinning technology, specifically to a method for preparing a high-purity metal starter sheet for electrowinning. Background Technology

[0002] Electrowinning / electrolytic refining is a major industrial method for obtaining high-purity metals, widely used in the production of valuable metals such as cobalt and nickel, as well as precious metals such as gold, silver, and platinum. In this process, the seed plate (also known as the cathode plate) serves as the initial deposition substrate, and its quality directly determines the flatness, purity, and production efficiency of the final product. Industry consensus states that "if the quality of the seed plate is substandard, the quality of the produced electrowinning cobalt plates will be uncontrollable."

[0003] The inherent defects of traditional electrodeposition methods for preparing starter sheets are as follows:

[0004] (1) High coupling between processes leads to the amplification of defects at each stage. The preparation of the starter sheet involves seed plate pretreatment (grinding, polishing, insulating edge wrapping, curing, forming an isolation layer and repeated maintenance), seed plate electrowinning (30-60 hours), peeling (opening, rod separation, removal of residues), starter sheet post-treatment (leveling, edge trimming, texturing, lug making, bending, welding / riveting, pickling, drying, etc.), and repeated plate refining during the electrowinning process, totaling more than ten processes. Quality defects in the preceding processes will be passed down and amplified along the process chain. Even a small deviation in any link may lead to the scrapping of the starter sheet or the failure of the final product quality.

[0005] (2) It is heavily reliant on manual operation experience. Key processes such as applying insulating tape, peeling off openings, removing residues, leveling operations, and welding lifting lugs all depend on the operator's skill and experience. The cobalt starting sheet is hard and brittle, and the lifting lugs are prone to breakage when heated. Micro-cracks or breakage are easily generated during cutting, flattening, and punching. It is heavily reliant on manual operation, which is time-consuming and labor-intensive, making it difficult to achieve standardized and automated production, and resulting in large fluctuations in product quality.

[0006] (3) The process is lengthy, inefficient, and prone to quality problems. From seed board pretreatment to the final usable starter sheet, more than ten processes are required. Each process is not only time-consuming (the preparation cycle of a single starter sheet usually exceeds 48 hours), but also prone to problems such as tape detachment, edge damage, peeling and cracking, leveling cracking, and welding failure, resulting in frequent rework, production interruption, and extremely low overall efficiency.

[0007] (4) The deformation energy accumulated inside the electrodeposition layer cannot be eliminated. During the electrodeposition process, metal ions accumulate significant deformation energy inside the deposition layer during the cathodic reduction deposition. This deformation energy inevitably leads to problems such as warping, edge cracking, and increased brittleness in the starter sheet.

[0008] In response to the above problems, the industry has tried a variety of improvement solutions, but none of them have been able to fundamentally solve the technical difficulties in the preparation of the starting electrode.

[0009] 1. Seed plate surface treatment technology. For example, the prior art CN120844157A discloses a method for treating titanium cathode plates, which generates a nano-sized oxide film on the surface of the titanium seed plate by two-stage gradient temperature washing to reduce the difficulty of peeling. This method only focuses on optimizing the peeling process and fails to solve systemic problems such as the internal stress of the starting electrode itself, the welding of the lifting lugs, and automated processing.

[0010] 2. Automated processing equipment. For example, existing technology CN119609567A discloses an automated production method for electrolytic cobalt plate starter sheets, which integrates processes such as hot washing, peeling, annealing, leveling, edge trimming, and welding. Although this solution reduces some manual operations, it is essentially a mechanical automation transformation of the traditional multi-step process. The number of processes has not been reduced, and the complexity of the equipment and investment costs have actually increased.

[0011] 3. Alternative Seed Plate Materials and Structural Designs. For example, existing technology CN102234822B proposes using rolling to prepare nickel starter sheets to circumvent the seed plate electrowinning process. However, the rolling process can only press the contact surfaces of adjacent layers of nickel foam together densely, but the outermost layers of the composite plate (i.e., the upper and lower surfaces) still retain the original porous structure of a single layer of nickel foam. This is because the outer surface faces the rolls during rolling, not other nickel foam layers, and lacks "ribs from the opposite side" to fill its pores. Even with immense pressure from the rolls, only the ribs on the outer surface can be flattened, not the inherent porosity. Therefore, the so-called "bright and non-porous" appearance only refers to the macroscopic appearance of the composite plate; at the material structure level, the porous characteristics of the two outer surfaces still exist. Furthermore, this solution still requires welding or riveting to attach the electrode lugs (lifting lugs). Due to the inherent porous structure of the outer surface of nickel foam, it is difficult for the weld pool to form a continuous and dense bond during welding, resulting in insufficient tab connection strength—which is consistent with the well-known engineering practice that "welding nickel foam tabs is both difficult and weak."

[0012] Therefore, the series of technical problems caused by the starter sheet in the existing electrode preparation process, such as "sheet bursting, deformation, weak lug connection, reliance on manual labor, and complex and lengthy process," are common in the cobalt and precious metals fields. Moreover, due to the extremely high value per gram of precious metals, the material losses and production interruption costs caused by the above problems are even more prominent. Summary of the Invention

[0013] In view of the common problems in the preparation of starter sheets for cobalt electrowinning in the above-mentioned prior art, such as high internal stress, easy plate explosion, need for cutting and welding, and high dependence on manual labor, the present invention provides an integrated starter sheet preparation method and system based on chemical vapor deposition (CVD).

[0014] To achieve the above objectives, the present invention provides the following technical solution:

[0015] A method for preparing a high-purity metal starter sheet for electrodeposition includes the following steps: depositing a uniformly thick metal deposition layer with built-in lifting lugs directly on a substrate using CVD technology; then peeling the metal deposition layer directly off the substrate to obtain the high-purity metal starter sheet; the lifting lugs include fixing holes.

[0016] A method for preparing a high-purity metal starter sheet for electrodeposition, comprising the following specific steps:

[0017] S1: A substrate is provided, wherein a recessed groove structure is provided on the surface of the substrate at a position corresponding to the lifting lug of the target starter sheet, and a protruding block is provided at the bottom of the recessed groove structure. The recessed groove structure is used to make the thickness of the lifting lug formed by deposition greater than the thickness of the sheet body. The block is used to form a through hole during the deposition process, and the surface of the substrate is passivated.

[0018] S2: The substrate is placed in a chemical vapor deposition reaction chamber, and a precursor gas containing the target metal and an inert carrier gas are introduced. The partial pressure of the precursor gas is 10-50 Pa and the total pressure is 100-1000 Pa. Chemical vapor deposition is performed at a deposition temperature of 200-350℃ to form a metal deposition layer on the substrate surface. The thickness of the metal deposition layer is 0.3-1.5 mm and the deposition rate is 0.5-2.0 μm / min.

[0019] S3: After deposition, the substrate is cooled, and the metal deposition layer is separated from the substrate by utilizing the difference in thermal expansion coefficients between the substrate and the metal deposition layer, thus obtaining the high-purity metal starter sheet.

[0020] In step S2, the target metal is one of cobalt, gold, silver or platinum; in step S1, the substrate is selected from one of titanium plate or molybdenum plate.

[0021] When the target metal is cobalt, the deposition temperature is 200-280℃, the deposition pressure is 200-800Pa, and the deposition rate is 0.5-1.5μm / min.

[0022] In step S1, the passivation process involves holding the substrate at 400-600°C for 1-2 hours in an oxidizing atmosphere to form a dense oxide film. The substrate dimensions include, but are not limited to: 0.6m×0.8m, 0.8m×0.8m, 0.8m×1.0m, and 1.0m×1.0m.

[0023] In step S2, the reaction chamber includes a spray-type gas distribution plate and a multi-zone independent temperature-controlled heating stage, which makes the temperature field and airflow field on the substrate surface uniformly distributed; the thickness tolerance of the metal deposition layer is within ±5% of the target thickness.

[0024] The spray-type gas distribution plate uniformly sprays the deposited gas, and the opening density is 50-200 holes / square meter.

[0025] After deposition is completed in step S3, the sample is cooled to room temperature at a rate of 2-5℃ / min in an inert atmosphere, and separated with the aid of an air knife at a pressure of 0.5-1.0MPa.

[0026] In step S3, the area of ​​the high-purity metal starter sheet is not less than 0.45 square meters, and in step S1, the area of ​​the substrate is not less than 0.45 square meters.

[0027] In step S3, the thickness of the high-purity metal starter sheet is 0.3-1.5 mm, the thickness tolerance is within ±5% of the target thickness, the surface roughness Ra≤0.5 μm, the number of lifting lugs is two, the thickness of the lifting lugs is slightly thicker than that of the sheet-like cobalt body, and they are symmetrically arranged on the same side edge of the sheet-like body; the diameter of the through hole is 5-15 mm, and the purity of the starter sheet is ≥99.9995%.

[0028] Chemical vapor deposition (CVD) is a thin film preparation technique that utilizes gaseous precursors to undergo chemical reactions on a heated substrate surface to deposit solid materials. CVD has become an important technology in the field of materials preparation, widely used in electronics, optoelectronics, catalysis, and energy applications, such as semiconductor device manufacturing, silicon wafer fabrication, and solar cells. It can prepare pure coatings with consistent thickness (micrometer-nanometer level) and controllable porosity, and can even be applied to complex or curved surfaces. In the field of metallic materials, CVD technology is mainly used to deposit metal thin films or coatings on substrate surfaces. For example, CVD can be used to grow metal thin films such as copper and aluminum to form conductive layers such as wiring and electrodes; it can be used to coat wear-resistant TiC or TiN thin films with a thickness ≤10 micrometers on tool steel surfaces; it can be used to deposit iridium thin films on graphite and ceramic substrates; and it can also be used to coat gas turbine components with metal to improve their corrosion and wear resistance. In addition, CVD is also used to prepare freestanding thick film / plate structures such as diamond thick films (0.3-1.3 mm), self-supporting diamond thick plates, and high-purity tungsten slabs. It can be seen that the current applications of CVD technology are mainly concentrated in the following directions: (1) thin film deposition in the field of semiconductor microelectronics; (2) wear-resistant / corrosion-resistant coatings on the surface of tools and parts; (3) independent thick film / thick plate preparation of refractory materials such as diamond and tungsten. It is one of the technical solutions for surface modification. In the application of existing CVD metal technology, the deposited layer is either retained on the substrate as a permanent functional layer (such as semiconductor wiring, electrodes, anti-corrosion coatings, etc.), or the deposited layer itself is the final product form (such as diamond thick film, tungsten plate blanks, etc.). Its typical application is to deposit permanent thin films or coatings on the substrate surface (such as semiconductor wiring, tool coatings, anti-corrosion layers, etc.). The deposited layer is usually only a few micrometers thick and can be used directly without being peeled off from the substrate.

[0029] Unlike the problems addressed by traditional CVD technologies, the CVD process in this invention undertakes a completely different task: a specially structured mold is set on the substrate surface to simultaneously form an integrated structure of a sheet-like body, lifting lugs, and through-holes during deposition. Grooves are used for thickening, with a depth of 1-2 mm. Thickening the lifting lugs improves their mechanical strength and fatigue resistance, enhances conductivity and current carrying capacity, while reducing contact resistance and energy consumption. This completely eliminates the traditional lifting lug reinforcement process and completely removes subsequent processes such as cutting, flattening, welding, and pickling in traditional starter sheet preparation. A metal layer with a thickness of 0.3-1.5 mm is deposited on a reusable substrate, allowing it to be completely peeled off as an independent starter sheet for direct use in the electrodeposition process. To achieve this goal, the substrate surface undergoes special treatment to reduce the adhesion between the deposited layer and the substrate, and the difference in their thermal expansion coefficients facilitates separation after cooling or allows for separation assisted by an air knife.

[0030] The advantages and inventiveness of this invention compared to the prior art are as follows:

[0031] (1) It completely solves the inherent defects of traditional starter sheets. The starter sheets prepared by the traditional electrodeposition method accumulate deformation energy inside, resulting in warping, edge cracking and increased brittleness, and this problem cannot be eliminated by process adjustment. The present invention uses CVD technology to deposit metal at the atomic level, and the starter sheet is flat without warping and cracking, which fundamentally eliminates this quality hazard.

[0032] (2) The preparation process is greatly simplified. Traditional processes require more than ten steps, including pretreatment of the substrate, electrowinning, peeling, annealing, leveling, edge trimming, embossing, lug fabrication, welding, and pickling, with a single sheet preparation cycle exceeding 48 hours. This invention uses a substrate protrusion mold to simultaneously form the lugs and through-holes during the deposition process. After deposition, the finished product is obtained by peeling. Only three steps are required, and the cycle is shortened to about 18 hours.

[0033] (3) Complete peeling of large-area metal layers has been achieved. Traditional peeling processes are prone to damaging the starter plate or seed plate, with a peeling success rate of only about 85%. This invention achieves automatic separation of metal layers with an area of ​​0.45 square meters or more after cooling through the synergistic effect of substrate passivation treatment and the difference in thermal expansion coefficients, with a peeling success rate of over 98%.

[0034] (4) Applicable to a variety of high-value metals such as cobalt, gold, silver, and platinum. By selecting appropriate precursors for different metals and adjusting the deposition temperature, this invention can be uniformly applied to the preparation of starter sheets for a variety of metals.

[0035] (5) The substrate is designed independently, with a raised baffle structure at the bottom of the substrate groove. During the CVD deposition process, the baffle is located where no metal vapor is deposited (or is blocked), and a through hole is formed on the lifting lug accordingly. The bottom and surrounding sidewalls of the groove simultaneously receive metal vapor deposition, making the total deposit mass per unit projected area in the groove area greater than that in the flat area. Therefore, in the same deposition time, the thickness growth rate of the lifting lug formed in the groove area (based on projected area) is higher than that of the sheet-like body formed in the flat area, realizing the 'in-situ accelerated thickening' of the lifting lug. This solves the problem of lifting lug thickening and easy breakage during electrodeposition. The selected substrate material (titanium, molybdenum) and the deposition metal (cobalt, gold, silver, platinum) have appropriate differences in their coefficients of thermal expansion, and a stable and dense passivation film can be formed on the substrate surface. Furthermore, no significant diffusion reaction or intermetallic compound formation occurs between the substrate and the deposition metal at the CVD deposition temperature.

[0036] The aforementioned effects are unattainable with existing technologies. Existing CVD technology is only used for nanoscale thin film deposition in the semiconductor field, producing permanent coatings that do not require stripping, with a thickness less than one-thousandth that of this invention and an area less than one-tenth that of this invention.

[0037] Attached Figure

[0038] Figure 1 This is a schematic diagram of the substrate structure in Embodiment 1 of the present invention. Figure 1 (Front view).

[0039] Figure 2 This is a schematic diagram of the substrate structure in Embodiment 1 of the present invention. Figure 2 (Top view).

[0040] Figure 3 This is a schematic diagram of the separation state between the metal deposition layer and the substrate after CVD deposition in Embodiment 1 of the present invention.

[0041] Figure 4 This is a schematic diagram of the final starter electrode product in Embodiment 1 of the present invention. Detailed Implementation

[0042] The present invention will be described in detail below with reference to embodiments and comparative examples. Those skilled in the art should understand that the following embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0043] Example 1: Preparation of cobalt starting sheet

[0044] This embodiment provides a method for preparing a large-area high-purity cobalt starting sheet.

[0045] S1: Substrate Preparation and Passivation Treatment. A titanium substrate is provided, with a deposition area size of 0.8m × 1.0m and a thickness of 10mm. The substrate surface is mechanically polished to a surface roughness Ra ≤ 0.05μm. Two 2mm deep groove structures with stops are provided at the corresponding positions of the lifting lugs on the substrate edge to form thicker lifting lugs and through holes during the deposition process. The processed substrate is placed in a muffle furnace and held at 500℃ for 1 hour in air atmosphere to form a dense TiO2 oxide film on the substrate surface.

[0046] S2: CVD deposition involves placing the passivated substrate in the CVD reaction chamber. The reaction chamber is equipped with a spray-type gas distribution plate with an opening density of 100 holes / m² and a 9-zone independent temperature-controlled heating stage.

[0047] High-purity argon (purity ≥99.999%) was used as the carrier gas to introduce cobalt octacarbonyl vapor into the reaction chamber. The precursor gas and carrier gas were uniformly sprayed onto the substrate surface through a spray-type gas distribution plate, controlling the precursor partial pressure at 20 Pa and the total pressure at 300 Pa. A 9-zone independently temperature-controlled heating stage maintained all areas of the substrate at 240°C. Chemical vapor deposition was performed at this temperature at a deposition rate of 1.0 μm / min for approximately 16.3 hours (target thickness 1.0 mm). During deposition, the cobalt layer simultaneously covered the flat areas and recessed baffle structures of the substrate, forming a sheet-like body, lifting lugs, and through-holes.

[0048] S3: After cooling and delamination, heating is stopped, and the substrate is cooled to room temperature at a rate of 2°C / min under argon protection. During cooling, the titanium substrate (with a coefficient of thermal expansion of approximately 8.6 × 10⁻⁶) undergoes thermal expansion. -6 / K) and cobalt deposit (thermal expansion coefficient approximately 13×10) -6 Due to the difference in thermal expansion coefficients between K and the substrate surface, the cobalt deposit automatically peels off from the substrate surface. The starting electrode is then removed intact by wiping along the edge with a 0.8 MPa air knife. The substrate can be reused after inspection.

[0049] The resulting cobalt starter sheet has an area of ​​0.8 m², a thickness of 1.0 mm, a thickness tolerance of ±0.03 mm, a surface roughness Ra ≤ 0.3 μm, a flat surface without warping or cracking, and meets purity standards. The starter sheet consists of a sheet-like body and two integrally formed lifting lugs. The lifting lugs have through holes (10 mm in diameter). The lifting lugs and the sheet-like body are made of continuous cobalt material, without any welding seams or connection marks.

[0050] like Figure 1 , 2 As shown, the substrate surface has a recessed groove structure at the corresponding position of the lifting lug. When viewed from above the substrate surface, the groove structure is a recessed area that is lower than the substrate reference plane. When viewed from the bottom of the groove, there is a raised block at the bottom of the groove.

[0051] During CVD deposition, both the flat and grooved regions of the substrate receive metal vapor deposition simultaneously. Since the deposition initiation surface of the grooved region is lower than that of the flat region, the accumulated deposition layer thickness in the grooved region is greater than that in the flat region under the same deposition time. After deposition, the flat region forms a sheet-like body (thickness t1), and the grooved region forms a lug (thickness t2) (Figure 4). t2 > t1, which is the microstructure design feature of this invention. This thickening method is different from the traditional electrodeposition method of cutting thickened sheets and then welding reinforcement. The thickness growth rate of the lug formed in the grooved region (based on projected area) is higher than that of the sheet-like body formed in the flat region. In the later stage of deposition, the thickening rate of the flat region decreases significantly due to the surface stabilization, while the irregular surface of the grooved region still maintains high deposition activity. By extending the deposition time, the lug can achieve continuous thickening. The corners / edges of the groove form local additional thickening due to the step coverage effect, providing reinforcement at the key stress points of the lug.

[0052] Example 2: Preparation of cobalt starting sheet

[0053] The difference between this embodiment and Embodiment 1 lies in the substrate size and some process parameters. Except for step S2, all other steps are the same. Step S2 is as follows:

[0054] S2: CVD Deposition: High-purity argon gas was used as the carrier gas to introduce cobalt octacarbonyl vapor, which was uniformly sprayed onto the substrate surface through a spray-type gas distribution plate. The precursor partial pressure was controlled at 20 Pa, and the total pressure at 500 Pa. A 9-zone independently temperature-controlled heating stage was used to maintain all areas of the substrate at 260°C, with a deposition rate of 1.2 μm / min and a deposition time of approximately 13 hours (target thickness 1.0 mm). During the deposition process, uniform spraying through the spray-type gas distribution plate and independent temperature compensation through the 9-zone independently temperature-controlled heating stage ensured a uniform distribution of temperature and gas flow across the large-area substrate surface.

[0055] The resulting cobalt starting sheet has an area of ​​0.8 m², a thickness of 1.0 mm, a thickness tolerance of ±0.04 mm, a surface roughness Ra≤0.3 μm, a flat surface without warping, and the lifting lugs are integrally formed with the sheet body without any welding seams. The purity is qualified.

[0056] Example 3: Preparation of gold-based electrode sheets

[0057] This embodiment provides a method for preparing a large-area high-purity gold starting sheet to verify the versatility of the technical solution of the present invention for different metals.

[0058] S1: A molybdenum substrate with dimensions of 0.8m × 1.0m (area 0.8m²) and a thickness of 8mm is provided. The substrate surface is mechanically polished to Ra≤0.05μm, and two 2mm deep groove structures and stops are provided at the edges. The substrate is heated at 550℃ for 0.5 hours in an oxidizing atmosphere to form a dense oxide film.

[0059] S2: Using high-purity argon as the carrier gas, trimethyl (methylcyclopentadienyl) gold (Me2Au(acac)) vapor is introduced into the reaction chamber and uniformly sprayed onto the substrate surface through a spray-type gas distribution plate. The pore density is 100 pores / m², the precursor partial pressure is controlled at 10 Pa, and the total pressure is controlled at 200 Pa. A 9-zone independent temperature-controlled heating stage is used to maintain each area of ​​the substrate at 300℃, with a deposition rate of 0.5 μm / min, a deposition time of 16.7 hours, and a target thickness of 0.5 mm.

[0060] S3: After deposition, the gold deposition layer is slowly cooled to room temperature under argon protection, and the gold deposition layer automatically separates from the substrate to obtain a high-purity gold starting sheet.

[0061] The resulting gold-bearing electrode has an area of ​​0.8 m², a thickness of 0.5 mm, a flat surface, and qualified purity. The lifting lugs are integrally formed with the sheet body, without any welding seams and with through holes (15 mm in diameter).

[0062] Example 4: Preparation of silver starting sheet

[0063] This embodiment provides a method for preparing a large-area high-purity silver starting sheet to further verify the versatility of the technical solution of the present invention for different metals.

[0064] S1: A titanium substrate is provided, with dimensions of 1.0m × 1.0m (area of ​​1.0 square meters) and a thickness of 10mm. The substrate surface is mechanically polished to Ra≤0.05μm, and two 2mm groove structures are provided at the edge with a stop for forming through holes. The substrate is heated to 500℃ in air for 1.5 hours to form a dense oxide film.

[0065] S2: Using high-purity argon as the carrier gas, (1,5-cyclooctadiene) (hexafluoroacetylacetonate) silver (I) vapor was introduced into the reaction chamber and uniformly sprayed onto the substrate surface through a spray-type gas distribution plate with an opening density of 100 holes / m². The precursor partial pressure was controlled at 10 Pa, and the total pressure at 150 Pa. The substrate was kept at 250°C in each area using a 9-zone independent temperature-controlled heating stage, with a deposition rate of 0.6 μm / min and a deposition time of approximately 13.9 hours (target thickness 0.5 mm).

[0066] S3: After deposition, heating is stopped, and the substrate is cooled to room temperature at a rate of 2℃ / min under argon protection. The silver deposition layer automatically separates from the substrate and is peeled off with the assistance of a 0.8MPa gas knife to obtain a high-purity silver starting sheet.

[0067] The resulting silver starting sheet has an area of ​​1.0 m², a thickness of 0.5 mm, a thickness tolerance of ±0.02 mm, a surface roughness Ra≤0.3 μm, a flat surface without warping, and the lifting lugs are integrally formed with the sheet body without welding seams, and the purity is qualified.

[0068] Example 5: Large-area uniformity verification experiment

[0069] This embodiment is used to verify the deposition uniformity of the present invention on a large-area substrate.

[0070] Using the same substrate size (0.8m × 1.0m) and process parameters as in Example 1, after deposition, nine measurement points (four corners, four midpoints and center) were selected along the diagonal and center line of the substrate, and the deposition layer thickness at each point was measured.

[0071] Measurement results:

[0072]

[0073] The thicknesses at all nine measurement points were within the range of 0.97-1.01 mm, with a maximum deviation of ±3.0% of the target thickness, which is better than the ±5% tolerance requirement. This indicates that by using a spray-type gas distribution plate and a multi-zone independent temperature-controlled heating stage under the specific parameters of this invention (the spray-type distribution plate ensures that the precursor gas is uniformly sprayed to each area, and the multi-zone temperature control ensures that the temperature is consistent in each area of ​​the substrate), this invention achieves excellent deposition uniformity on large-area (≥0.45 m²) substrates.

[0074] Example 6: Effect of different deposition temperatures on the preparation of cobalt starting sheets

[0075] In this embodiment, deposition experiments were conducted at five temperature points: 200℃, 240℃, 280℃, 320℃, and 350℃, to verify the adjustability of the deposition temperature within the 200-350℃ temperature window and its impact on product quality. All experimental groups used the same substrate (0.8m × 1.0m titanium substrate, passivated at 500℃), the same precursor (Co2(CO)8), the same pressure conditions (total pressure 300Pa, partial pressure 20Pa), and the same target thickness (1.0mm).

[0076]

[0077] Experimental results show that the cobalt deposited layer can be completely peeled off from the substrate surface within a temperature range of 200-350℃.

[0078] At 200℃, the deposition rate is low (0.3 μm / min), the deposition layer is dense and the plate surface is flat, but the deposition time is long (about 55.6 h).

[0079] The deposition rate is moderate at 240-280℃, resulting in excellent deposition layer quality and a smooth, glossy plate surface, making it the preferred temperature range.

[0080] At 320-350℃, the deposition rate is high and the production efficiency is improved, but slight diffusion begins to appear at the interface, and there is a slight stickiness when peeling, but it is still within an acceptable range.

[0081] This embodiment demonstrates that the present invention can achieve complete deposition and stripping of cobalt starter sheets within a temperature window of 200-350℃, allowing users to flexibly select the deposition temperature based on production efficiency and product quality priorities. The optimal deposition temperature for gold, silver, etc., is slightly higher than that for cobalt.

[0082] Example 7: Sedimentation experiments under different deposition pressures

[0083] This embodiment conducts deposition experiments under different deposition pressures to verify the adjustability of the process within the total pressure range of 100-1000 Pa. In each experimental group, the total pressure was changed by adjusting the carrier gas flow rate, and the precursor partial pressure was adjusted accordingly to ensure the deposition rate. The remaining process parameters were basically the same as in Example 1.

[0084] CVD deposition under different pressures was performed using high-purity argon as the carrier gas and introducing octacarbonyl cobalt vapor. The substrate temperature was 240℃, and the target thickness was 1.0 mm. The total pressure of each experimental group was controlled by adjusting the carrier gas flow rate and the throttle valve opening, and the precursor partial pressure was adjusted by controlling the precursor source temperature to ensure that the deposition rate was basically consistent. The parameters for each group are as follows:

[0085]

[0086] Results Analysis: With a total pressure of 200 Pa-800 Pa, a deposition time of approximately 1 μm / min, a thickness tolerance of ±2.5%~3%, and a surface roughness Ra≤0.3 μm, excellent uniformity was maintained. This indicates that uniformity could still be maintained even with further increases in pressure. As the total pressure increased further to 1000 Pa, the gas distribution began to be affected by the increased molecular collision frequency, resulting in a decrease in the diffusion coefficient. The diffusion of the precursor towards the substrate edge was hindered, reducing the number of molecules effectively reaching the surface. The deposition time was approximately 18.5 h, with a slightly thicker deposition in the center of the substrate. The thickness tolerance was ±4.5%, and the surface roughness Ra≤0.32 μm. Although complete peeling and a smooth surface were still possible, it was observed that the gas molecular collision frequency increased with higher partial pressures, leading to a slightly thicker deposition in the central region due to a slightly longer gas residence time.

[0087] Example 8

[0088] This embodiment illustrates the specific application of the chemical vapor deposition system provided by the present invention in the preparation of large-area cobalt starter sheets, in order to further verify the function and collaborative effect of each component of the system.

[0089] S1: Substrate preparation and installation

[0090] A titanium substrate is provided, with a deposition area size of 0.8m × 1.0m and a thickness of 10mm. The substrate surface is mechanically polished to a surface roughness Ra ≤ 0.05μm. The substrate surface has raised structures corresponding to the lugs and through-holes of the target starter electrode—a 2mm groove is provided at the edge of the substrate corresponding to the lug position, with a bottom protrusion at the bottom of the groove for forming the lugs and through-holes during the deposition process; the groove can increase the thickness of the lugs. The processed substrate is placed in a muffle furnace and held at 500℃ for 1 hour in air atmosphere to form a dense TiO2 oxide film. The passivated substrate is fixed on a multi-zone independently temperature-controlled heating platform within the reaction chamber, with the center of the substrate aligned with the center of the spray-type gas distribution plate to ensure that all areas of the substrate are within the spray coverage area.

[0091] S2: System airtightness and airflow adjustment

[0092] Close the reaction chamber, activate the vacuum system to evacuate to a base vacuum (≤10Pa), and purge with high-purity argon gas (purity ≥99.999%) to 100Pa. Maintain this pressure for 30 minutes and confirm the system's airtightness. Adjust the flow distribution of each opening area of ​​the spray-type gas distribution plate to ensure uniform airflow across the substrate surface, with flow deviation controlled within ±5%. Preheat each area of ​​the substrate to 200℃ using a 9-zone independently temperature-controlled heating stage and hold for 30 minutes to stabilize the substrate temperature field.

[0093] S3: Precursor supply and deposition

[0094] The octacarbonyl cobalt (Co2(CO)8) source bottle was heated to 40-45℃ in a thermostatic bath. High-purity argon gas (flow rate 200-500 sccm) was used as the carrier gas to introduce the precursor vapor into the reaction chamber. The precursor supply system controlled the partial pressure of the precursor to 20 Pa and the total pressure to 300 Pa using a mass flow controller and pressure regulating valve. The precursor gas and carrier gas were uniformly sprayed onto the substrate surface using a spray-type gas distribution plate. The substrate temperature was maintained at 240℃, the deposition rate was 1.0 μm / min, and the deposition time was approximately 16.7 hours (target thickness 1.0 mm). During deposition, a 9-zone independent temperature-controlled heating stage provided independent temperature compensation for different areas of the substrate (temperature deviation ≤ ±2℃). The spray-type gas distribution plate ensured uniform distribution of the precursor on the substrate surface, collectively achieving uniform deposition thickness over a large area.

[0095] S4: Cooling and Stripping Assist

[0096] After deposition, heating is stopped, the precursor supply is shut off, and argon gas is continuously supplied. The cooling system is programmed to cool to room temperature at a rate of 2°C / min. During cooling, due to the difference in thermal expansion coefficients between the titanium substrate and the cobalt deposited layer, the cobalt deposited layer automatically peels off from the substrate surface. When the edge of the deposited layer peels off by approximately 1-3 mm, the air knife assembly is activated to provide a high-pressure argon gas flow of 0.8 MPa to the interface between the deposited layer and the substrate, uniformly sweeping along the substrate edge to assist in complete peeling. The substrate can be reused after inspection.

[0097] Comparative Example 1: Preparation of Cobalt Starter Sheets by Conventional Electrowinning

[0098] Cobalt starter sheets were prepared using a traditional seed plate electrowinning method. After pretreatment including insulating edges, grinding, polishing, applying insulating tape, and waxing, the titanium seed plate was electrowinning in a seed plate groove at a current density of 300 A / m² for 48 hours, depositing a cobalt layer of approximately 1.0 mm. During peeling, manual opening with a flat chisel, separation with a stick, and removal of residue were required. The peeled cobalt sheet was curled and required annealing, leveling with large equipment, edge trimming, and texturing. Lifting lugs were then separately cut from scrap material, bent, and finally fixed to the starter sheet by resistance spot welding. Results: The total time was approximately 55 hours, involving more than 12 processes, with a yield of only about 85%. The surface roughness of the obtained starter sheet was Ra > 1.0 μm, and the surface exhibited varying degrees of warping deformation. Obvious weld points and heat-affected zones were present at the welded joints of the lifting lugs.

[0099] Example 1 requires only 3 steps and approximately 18 hours to obtain the finished product, with a sheet yield rate of ≥98%. The lifting lugs and the sheet body are integrally formed without welds, and the plate surface is flat and free of warping. The traditional electrowinning method is significantly inferior to this invention in terms of the number of steps, preparation cycle, sheet yield rate, product flatness, and lifting lug reliability.

[0100] Comparative Example 2: Substrate without passivation treatment

[0101] The same CVD process parameters as in Example 1 were used (titanium substrate, Co2(CO)8 precursor, 240°C, total pressure 300Pa, precursor partial pressure 20Pa), but the substrate was not subjected to oxidation passivation treatment.

[0102] Results: After deposition, a metallurgical bond formed between the cobalt deposit and the titanium substrate due to atomic diffusion. This bond was too strong to be completely peeled off. Forced peeling resulted in the cobalt layer fracturing, with a peeling success rate of less than 10%. A large amount of cobalt residue remained on the substrate surface, requiring re-polishing before reuse.

[0103] Comparative Example 3: Deposition temperature exceeds the range of this invention (400℃, 500℃ high temperature)

[0104] The same CVD process parameters as in Example 1 were used (titanium substrate, passivated at 500°C, Co2(CO)8 precursor, total pressure 300Pa, partial pressure 20Pa), but the deposition temperature was increased to 400°C and 500°C.

[0105] Results: At high temperatures of 400℃ and 500℃, the TiO2 oxide film formed on the titanium substrate surface at 500℃ gradually failed and dissolved. Cobalt came into direct contact with the titanium substrate and underwent a significant diffusion reaction, forming intermetallic compounds (such as TiCo3). The deposited layer was completely "welded" to the substrate, making peeling difficult, and electrode breakage occurred. The higher the temperature, the more likely the substrate would be scrapped. Furthermore, at higher temperatures, some of the precursor gas had already undergone partial physicochemical transformation in the air before even contacting the substrate.

[0106] Comparative Example 4: Deposition temperature was lower than the range of this invention (low temperature 150°C)

[0107] The same CVD process parameters as in Example 1 were used (titanium substrate, passivated at 500°C, Co2(CO)8 precursor, total pressure 300Pa, partial pressure 20Pa), but the deposition temperature was reduced to 150°C.

[0108] Results: The decomposition rate of octacarbonyl cobalt at 150℃ is extremely low, with a deposition rate of only 0.04 μm / min. At this rate, it would take approximately 210 hours to achieve the target thickness of 0.5 mm. The deposited layer is loose, has poor density, and is under tensile stress. During subsequent cooling, the deposited layer cracks and peels off spontaneously, making it impossible to obtain a complete starter sheet. The low temperature of 150℃, slow deposition rate, and long time required result in incomplete decomposition of the precursor, residual organic carbon and oxide impurities in the deposited layer, incomplete grain growth, and poor mechanical properties of the deposited layer.

[0109] Comparative Example 5: Deposition thickness exceeds the scope of this invention.

[0110] The present invention sets the thickness of the starter sheet to 0.3-1.5mm, which is based on the actual requirements of the electrowinning process for the mechanical strength of the starter sheet. The core of the present invention is to prepare the starter sheet: when the thickness is less than 0.3mm, the starter sheet is not strong enough and cannot withstand the stress of the lifting lug, the impact of entering the slot and the electrowinning process.

[0111] The same CVD process parameters as in Example 1 were used (titanium substrate, passivated at 500°C, Co2(CO)8 precursor, 240°C, total pressure 300Pa, partial pressure 20Pa), but the deposition time was shortened to the target thickness of 0.1 mm (approximately 1.7 hours).

[0112] Results: After deposition, the cobalt layer could be easily and completely peeled off from the substrate surface, with a silver-gray appearance, a surface roughness Ra≤0.2μm, and uniform thickness. However, this cobalt layer was extremely thin (only 0.1mm), soft in texture, and had very low bending strength. It curled up under unsupported conditions and could not be used as a starter sheet in subsequent electrodeposition processes.

[0113] When the thickness exceeds 1.5 mm, on the one hand, material consumption increases, deposition time is prolonged, and economic efficiency decreases; on the other hand, the internal stress of the CVD deposited layer increases with thickness, significantly increasing the risk of cracking and reducing the complete peeling rate. Therefore, 0.3-1.5 mm is a reasonable range that can be determined by those skilled in the art based on the actual situation of the starter sheet, the requirements of the electrodeposition process, and the stress control law of CVD thick film preparation.

[0114] Comparative Example 6: No spray-type gas distribution plate used (single-pipe air inlet)

[0115] The same substrate size (0.8m × 1.0m titanium substrate), passivation treatment, precursor and deposition parameters (Co2(CO)8, 240℃, total pressure 300Pa, partial pressure 20Pa, target thickness 1.0mm) as in Example 1 were used, but instead of a spray-type gas distribution plate, a conventional single-pipe sidewall gas inlet method was used, with gas introduced through a single inlet pipe on the sidewall of the reaction chamber.

[0116] Results: The thickness at different locations on the substrate surface was measured after deposition. Five measurement points were selected along the gas flow direction (from the inlet to the outlet), and the thicknesses were as follows: inlet end (50 mm from the inlet) 1.32 mm (deviation +32.0%), near inlet end (200 mm from the inlet) 1.18 mm (deviation +18.0%), central area (400 mm from the inlet) 0.95 mm (deviation -5.0%), far inlet end (600 mm from the inlet) 0.72 mm (deviation -28.0%), and outlet end (800 mm from the inlet) 0.58 mm (deviation -42.0%).

[0117] The substrate surface exhibits a severe "thicker at the front, thinner at the back" thickness distribution—the thickness at the air inlet end exceeds the standard by +32%, while the thickness at the exhaust end deviates by -42%. For large-area substrates with an area ≥0.45m², without a spray-type gas distribution plate, the precursor gas will generate a significant concentration gradient on the substrate surface, making uniform deposition impossible. This uneven deposition layer not only affects the quality consistency of the starter sheet but also leads to uneven local stress distribution due to thickness differences, increasing the risk of cracking during subsequent peeling.

[0118] Comparative Example 7: Heating station without multi-zone independent temperature control (single temperature control)

[0119] The same parameters as in Example 1 were used, but instead of a 9-zone independent temperature-controlled heating stage, a single temperature-controlled heating method was used, with the center temperature of the substrate monitored only by a single thermocouple.

[0120] Results: After deposition, the thickness at different locations on the substrate surface was measured. The thickness in the central region was 1.02 mm (deviation +2.0%), while the thickness in the edge region (50 mm from the edge) ranged from 0.82 to 0.88 mm (deviation -12% to -18%), exhibiting a temperature-edge effect distribution of "thicker in the center and thinner at the edge". The surface roughness Ra was ≤0.30 μm in the central region and reached 0.55-0.65 μm in the edge region.

[0121] During the heating process of large-area substrates, the heat radiation loss in the edge regions is significantly greater than that in the center regions. Without multi-zone independent temperature control, the edge temperature is much lower than the center, leading to a decrease in precursor decomposition rate, deposition rate, and insufficient grain growth in the edge regions. Multi-zone independent temperature-controlled heating stages are necessary to achieve uniform temperature field in large-area substrates; a single temperature control method cannot guarantee the deposition consistency of large-area substrates.

[0122] Comparative Example 8: Using existing CVD thin film deposition technology

[0123] Referring to existing CVD cobalt thin film deposition technology, the following parameters were used for comparative experiments: octacarbonyl cobalt was used as the precursor, the deposition temperature was 80℃, the total pressure was 10Pa (low pressure), the substrate was a silicon wafer (a commonly used substrate in existing technologies), and the target thickness was 0.5mm.

[0124] Results: The deposition rate was extremely low (approximately 0.005 μm / min), requiring approximately 1667 hours (about 69 days) to achieve a thickness of 0.5 mm. The deposited layer was grayish-black, loose, and porous with extremely poor adhesion, resulting in localized peeling during the deposition process and making it impossible to obtain a complete starter sheet. Part of the cobalt deposited layer exhibited severe diffusion bonding with the titanium substrate, making it impossible to peel off. Forced peeling caused the cobalt layer to fracture, leaving cobalt deposited layers on the substrate surface.

[0125] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

[0126] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing a high-purity metal starter sheet for electrodeposition, characterized in that, The steps are as follows: A uniform metal deposition layer, consisting of a sheet-like body and a lug continuously connected to the sheet-like body, is directly deposited on the substrate using CVD technology. The metal deposition layer is then directly peeled off from the substrate to obtain the high-purity metal starter sheet. The lug contains fixing holes.

2. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 1, characterized in that, The specific steps are as follows: S1: A substrate is provided, wherein a recessed groove structure is provided on the surface of the substrate at a position corresponding to the lifting lug of the target starter sheet, and a protruding block is provided at the bottom of the recessed groove structure. The recessed groove structure is used to make the thickness of the lifting lug formed by deposition greater than the thickness of the sheet body. The block is used to form a through hole during the deposition process, and the surface of the substrate is passivated. S2: The substrate is placed in a chemical vapor deposition reaction chamber, and a precursor gas containing the target metal and an inert carrier gas are introduced. The partial pressure of the precursor gas is 10-50 Pa and the total pressure is 100-1000 Pa. Chemical vapor deposition is performed at a deposition temperature of 200-350℃ to form a metal deposition layer on the substrate surface. The thickness of the metal deposition layer is 0.3-1.5 mm and the deposition rate is 0.5-2.0 μm / min. S3: After deposition, cooling is performed to separate the metal deposition layer from the substrate, thus obtaining the high-purity metal starter sheet.

3. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 2, characterized in that: In step S2, the target metal is one of cobalt, gold, silver or platinum; in step S1, the substrate is selected from one of titanium plate or molybdenum plate, and the groove depth is 1-2 mm.

4. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 3, characterized in that: When the target metal is cobalt, the deposition temperature is 200-280℃, the deposition pressure is 200-800Pa, and the deposition rate is 0.5-1.5μm / min.

5. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 2, characterized in that: In step S1, the passivation treatment involves holding the material at 400-600°C for 1-2 hours in an oxidizing atmosphere to form a dense oxide film.

6. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 2, characterized in that: In step S2, the reaction chamber includes a spray-type gas distribution plate and a multi-zone independent temperature-controlled heating stage; the thickness tolerance of the metal deposition layer is within ±5% of the target thickness.

7. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 6, characterized in that: The spray-type gas distribution plate uniformly sprays the deposited gas, and the opening density is 50-200 holes / square meter.

8. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 2, characterized in that: After deposition is completed in step S3, the sample is cooled to room temperature at a rate of 2-5℃ / min in an inert atmosphere, and separated with the aid of an air knife at a pressure of 0.5-1.0MPa.

9. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 2, characterized in that: In step S3, the area of ​​the high-purity metal starter sheet is not less than 0.45 square meters, and in step S1, the area of ​​the substrate is not less than 0.45 square meters.

10. The method for preparing a high-purity metal starter sheet for electrodeposition as described in claim 2, characterized in that: In step S3, the thickness of the high-purity metal starter sheet is 0.3-1.5 mm, the thickness tolerance is within ±5% of the target thickness, the surface roughness Ra≤0.5 μm, the number of the lifting lugs is two, symmetrically arranged on the same edge of the sheet body, and the thickness is thicker than the sheet body; the diameter of the through hole is 5-15 mm, and the purity of the starter sheet is ≥99.9995%.

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