Method and equipment for platinum electroforming process

Abstract

According to the method and equipment for the platinum electroforming process, a wax blank with a conducting layer is placed in an acid copper sulfate electrolyte, electroplating is carried out with copper as an anode and the wax blank as a cathode, and a flat, continuous and fine-grain copper substrate layer is constructed through electroplating, so that a stable metal substrate is provided for subsequent platinum metal deposition. And with the master mold as a cathode and the titanium mesh as an anode, electroplating in dinitroso diammine platinum electrolyte, depositing a platinum layer on the copper substrate layer to obtain a platinum layer electrocasting, and forming a continuous and fine-grained platinum layer on the flat copper substrate layer. The binding force of the platinum layer and the substrate is remarkably improved, the interface integrity can still be kept through thick layer deposition, and subsequent demolding and polishing are more stable. The thickness compactness is improved, the in-plane and inter-part thickness deviation of large-area / complex curved surface electroforming is reduced, the edge thickening and scorching tendency is reduced, and fine lines / blind areas can be controllably covered. And because the substrate is flat and the current is homogenized, the platinum layer is more compact, white and bright in appearance, the yield is improved, and the problem of hydrogen embrittlement is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of platinum electroforming process, and more particularly to a method and equipment for platinum electroforming process. Background Technology

[0002] Platinum electroforming is a precision forming technique based on cathodic electrodeposition. It involves depositing a platinum layer on the surface of a conductive mold, which is then separated to obtain the finished product. This process is widely used in the manufacture of precision components for jewelry and high-end decorations, industrial catalyst carriers, and electronics and avionics. Platinum, due to its excellent chemical stability and corrosion resistance, superior catalytic activity, and unique intrinsic white luster, is an ideal material for these fields. Compared to traditional machining, investment casting (molding), or hydraulic molding, electroforming can produce complex structures and fine textures with high fidelity; the finished products are lighter (weight reduction ≥50% compared to traditional processes), harder (Vickers hardness approximately HV180–220), and purer (Pt content ≥99.9%).

[0003] However, during platinum electroforming, water molecules are present in the electrolyte solution. Electroforming is often accompanied by water electrolysis, which produces hydrogen gas. The cathode needs to reduce platinum ions in the electrolyte solution to platinum, which then adheres to the mold for electroforming. However, platinum has a strong adsorption characteristic for hydrogen, which readily adsorbs onto the surface of the casting, causing pores and resulting in a rough, blackened, and porous electroformed layer. When the platinum electroformed layer thickness reaches 10 micrometers or more, hydrogen embrittlement occurs due to the adhesion of hydrogen, leading to cracking. If the thickness reaches 100 micrometers during electroforming, hydrogen embrittlement can cause the platinum electroformed layer to crack directly, making electroforming difficult. Summary of the Invention

[0004] Therefore, it is necessary to propose a method and equipment for platinum electroforming process to solve the above-mentioned technical problems.

[0005] This invention provides a method for platinum electroforming, the method comprising: Step S1: Immerse the wax blank in a copper powder mixture to form a conductive layer on the surface of the wax blank, thereby obtaining a wax blank with a conductive layer; Step S2: Place the wax blank with the conductive layer in a copper sulfate electrolyte, use copper as the anode and the coated wax blank as the cathode for electroplating, and obtain the initial plated part; Step S3: Clean and dry the initial plated part to obtain the original mold; Step S4: Using the original mold as the cathode and the titanium mesh as the anode, electroplating is performed in dinitrosodiammineplatinum electrolyte to obtain a platinum layer electrocast part. In at least one embodiment of this application, step S1 specifically includes the following steps: A conductive copper wire is inserted into the wax blank to form a wax blank with copper wire. Preparation of copper powder mixture: Ethyl acetate and ultrafine copper powder are mixed evenly at a mass ratio of 7:3 to obtain copper powder mixture; The wax blank with copper wire is immersed in the copper powder mixture, and then removed and allowed to dry and solidify naturally to form a conductive layer with a thickness of 10-20 μm on the surface of the wax blank, thus obtaining the wax blank with the conductive layer.

[0006] In at least one embodiment of this application, the formulation of the copper sulfate electrolyte is as follows: Prepare a copper sulfate electrolyte with a copper sulfate concentration of 150-200 g / L and a sulfuric acid concentration of 130-150 ml / L. The thickness of the electroplated copper layer on the initial plated part is 100-150 μm.

[0007] In at least one embodiment of this application, step S3 specifically includes the following steps: The initial plated part is removed from the copper sulfate electrolyte and cleaned a second time with pure water. After cleaning, the initial plated part is dried with a forced air dryer at a temperature ≤40℃ to obtain the original mold.

[0008] In at least one embodiment of this application, the formulation of the dinitrosodiammineplatinum electrolyte is as follows: The mixture consists of 20-25 g / L dinitrosodiamineplatin, 50 ml / L sulfuric acid, a complexing agent, a stabilizer, and a brightener, with a pH of 1-2. The original mold is placed in the dinitrosodiamineplatin electrolyte at 50°C for electroplating to obtain a platinum-coated electrocast part.

[0009] In at least one embodiment of this application, during the electroplating process in step S2 and / or step 4: The copper sulfate electrolyte and / or the dinitrosodiammineplatinum electrolyte are circulated by a first water pump and a second water pump; and gas is introduced into the copper sulfate electrolyte and / or the dinitrosodiammineplatinum electrolyte for aeration.

[0010] In at least one embodiment of this application, the anode is placed in the anode placement area between the first spiral circulation tube and the second spiral circulation tube; in the electroplating chamber, the second spiral circulation tube surrounds the electroplating area, the cathode is located in the electroplating area, and the first spiral circulation tube is arranged around the second spiral circulation tube. During the electroplating process, a first water pump pumps electrolyte into the electroplating chamber through a first spiral circulation pipe, and a second water pump pumps electrolyte from the electroplating chamber through a second spiral circulation pipe. The tangential outlet on the peripheral wall of the second spiral circulation pipe faces the electroplating area, and the tangential inlet on the peripheral wall of the first spiral circulation pipe faces the second spiral circulation pipe. The first and second spiral circulation pipes circulate to form a circumferential flow field around the electroplating area.

[0011] In at least one embodiment of this application, during the electroplating process, the outlet is connected to the second water pump to form a circulation in the electroplating area, thereby creating a flow rate difference between the second spiral circulation pipe and the electroplating area; The inlet, through the first water pump, creates centrifugal suction in the anode placement area and the electroplating area, thereby creating negative pressure centrifugal force in the anode placement area and the electroplating area.

[0012] In at least one embodiment of this application, the platinum electroforming process further includes: S5. Dewaxing and copper removal are performed on the platinum electrocasting part from step S4 to obtain a platinum casting. S6. Anneal and polish the platinum casting to obtain the finished platinum product.

[0013] This invention provides a platinum electroforming apparatus and a method for implementing the platinum electroforming process described in any of the above claims, the platinum electroforming apparatus comprising: The electroforming cylinder has an internal electroplating chamber and a filtration chamber. The first water pump is installed inside the electroplating chamber; The second water pump is installed inside the electroplating chamber; The first spiral circulation tube extends vertically upward from the bottom wall of the electroplating chamber. The first spiral circulation tube has an inlet. The end of the first spiral circulation tube away from the bottom wall of the electroplating chamber is connected to the filter chamber through the first water pump. The second spiral circulation tube extends vertically upward from the bottom wall of the electroplating chamber. The second spiral circulation tube and the electroplating chamber form an electroplating area. An outlet is opened on the side of the second spiral circulation tube near the electroplating area. The first spiral circulation tube surrounds the second spiral circulation tube. The end of the second spiral circulation tube near the bottom wall of the electroplating chamber is connected to the filter chamber through the second water pump.

[0014] In at least one embodiment of this application, the outlet is inclined relative to the axis of the second spiral circulation tube toward the bottom wall of the electroplating area; The inlet is inclined relative to the axis of the first spiral circulation tube, away from the bottom wall of the electroplating area; The platinum electroforming equipment also includes: A microporous diffuser is located at the end of the first spiral circulation pipe away from the first water pump, and the microporous diffuser is connected to an external air supply pipe.

[0015] The method and equipment for implementing the platinum electroforming process of this embodiment will have at least the following beneficial effects: The platinum electroplating process and equipment provided above involve placing a wax blank with a conductive layer in an acidic copper sulfate electrolyte, using copper as the anode and the wax blank as the cathode for electroplating. This electroplating process constructs a smooth, continuous, and fine-grained copper substrate layer, thereby providing a stable metal substrate for subsequent platinum metal deposition.

[0016] Using the original mold as the cathode and a titanium mesh as the anode, electroplating is performed in a dinitrosodiammonium platinum electrolyte to deposit a platinum layer on a copper substrate to obtain a platinum electrocast part, forming a continuous, fine-grained platinum layer on a flat copper substrate.

[0017] The bonding strength between the platinum layer and the substrate is significantly improved, and the interface remains intact even with thick deposition, resulting in more stable subsequent demolding and polishing.

[0018] With improved thickness density, the thickness deviation between the in-plane and between parts in large-area / complex curved surface electroforming is reduced, the tendency of edge thickening and scorching is reduced, and fine lines / blind areas can also be controlled and covered.

[0019] Due to the flat substrate and homogenized current, the platinum layer morphology is denser and brighter, improving the yield and reducing hydrogen embrittlement. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] in: Figure 1 A flowchart of a method for platinum electroforming process in one embodiment; Figure 2 A flowchart of a method for platinum electroforming in another embodiment; Figure 3 This is a structural block diagram of a platinum electroforming apparatus in one embodiment; Figure 4 An exploded view of a platinum electroforming apparatus in one embodiment; Figure 5 for Figure 3 A cross-sectional view of the platinum electroforming equipment; Figure 6 for Figure 3 Another sectional view of the Zhongping Platinum Electroforming Equipment; Figure 7 for Figure 6 Another sectional view of the platinum electroforming equipment.

[0022] Explanation of main component symbols 100. Platinum electroforming equipment; 110. Electroforming cylinder; 110a. Electroplating chamber; 110b. Filtering chamber; 120. First water pump; 121. Second water pump; 122. First spiral circulation pipe; 122a. Inlet; 123. Second spiral circulation pipe; 123a. Outlet; 123b. Electroplating area; 122b. Anode placement area; 130. Microporous diffuser; 140. Anode. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for platinum electroforming, the method comprising: Step S1: Immerse the wax blank in a copper powder mixture to form a conductive layer on the surface of the wax blank, thereby obtaining a wax blank with a conductive layer; Step S2: Place the wax blank with the conductive layer in a copper sulfate electrolyte, use copper as the anode and the coated wax blank as the cathode for electroplating, and obtain the initial plated part; Step S3: Clean and dry the initial plated part to obtain the original mold; Step S4: Using the original mold as the cathode and the titanium mesh as the anode, electroplating is performed in dinitrosodiammineplatinum electrolyte to obtain a platinum layer electrocast part. Please refer to Figure 1 In this embodiment, the wax blank is immersed in a copper powder mixture to form a continuous conductive layer on the surface of the wax blank, which serves as a uniform starting interface for electrodeposition and ensures uniform current distribution during subsequent electroplating.

[0025] A wax blank with a conductive layer is placed in an acidic copper sulfate electrolyte and electroplated with copper as the anode and the wax blank as the cathode. Electroplating constructs a smooth, continuous, and fine-grained copper substrate layer, thereby providing a stable metal substrate for subsequent platinum metal deposition. This copper substrate layer is directly used to improve the adhesion and thickness distribution stability of the platinum electroplated layer (homogenizing current density in complex curved surfaces and fine texture areas, and reducing thickness deviation caused by edge effects).

[0026] The initial plated part is cleaned and dried to remove the residue and entrained liquid from the previous tank, stabilize the subsequent interface state, and obtain the original mold.

[0027] Using the original mold as the cathode and a titanium mesh as the anode, electroplating is performed in a dinitrosodiammoniaplatinum electrolyte to deposit a platinum layer on a copper substrate to obtain a platinum electrocast part. The use of P-acidic electrolyte and titanium mesh anode helps to maintain the stability of the bath composition and electric field distribution, forming a continuous, fine-grained platinum layer on a flat copper substrate.

[0028] The bonding strength between the platinum layer and the substrate is significantly improved, and the interface remains intact even with thick deposition, resulting in more stable subsequent demolding and polishing.

[0029] With improved thickness density, the thickness deviation between the in-plane and between parts in large-area / complex curved surface electroforming is reduced, the tendency of edge thickening and scorching is reduced, and fine lines / blind areas can also be controlled and covered.

[0030] Due to the flat substrate and homogenized current, the platinum layer morphology is denser and brighter, improving overall appearance consistency and yield, and reducing hydrogen embrittlement.

[0031] In at least one embodiment of this application, step S1 specifically includes the following steps: S10. Insert conductive copper wire into the wax blank to form a wax blank with copper wire; S11. Preparation of copper powder mixture: Ethyl acetate and ultrafine copper powder are mixed evenly at a mass ratio of 7:3 to obtain copper powder mixture; S12. Immerse the wax blank with copper wire in the copper powder mixture, then remove it and allow it to dry and solidify naturally to form a conductive layer with a thickness of 10-20 μm on the surface of the wax blank, thereby obtaining the wax blank with the conductive layer.

[0032] Please refer to Figure 1 and Figure 2 In this embodiment, a section of flexible conductive copper wire is inserted into or pre-embedded in the wax blank, with its end exposed to form a stable electrical connection point. Preferably, the copper wire is inserted through a pre-drilled hole or a heating needle, so that the copper wire fits tightly against the wax body, facilitating subsequent clamping and energization by the hanger.

[0033] Preparation of copper powder mixture: Ethyl acetate and ultrafine copper powder are mixed at a mass ratio of 7:3 and stirred evenly to obtain a uniform suspension. Ethyl acetate has good wetting and volatility for wax materials, and can provide stable rheological and spreading properties without softening the wax; ultrafine copper powder provides a uniform and continuous conductive layer.

[0034] The wax blank containing copper wires is completely immersed in the copper powder mixture, allowing the mixture to cover the surface of the wax blank through wetting and capillary action. It is then slowly removed and allowed to dry and solidify naturally at room temperature, forming a continuous conductive layer with a thickness of 10–20 μm on the surface of the wax blank, resulting in a wax blank with a conductive layer. If necessary, a single dip-coating process or a thin-coat-short-dry-recoat method can be used to control the thickness and uniformity.

[0035] Compared to relying solely on external clamping points for power transmission, pre-embedded copper wires can significantly reduce contact resistance and contact position instability, preventing localized overheating, burning, or the formation of current hotspots during the initial plating stage. At the same time, it provides a reliable current path for the conductive layer, resulting in a more uniform potential distribution across the entire wax blank surface.

[0036] Ethyl acetate has good wettability on wax surfaces and evaporates quickly, forming a dense coating without introducing water, thus avoiding the initial hydrogen evolution and bubble entrainment caused by water-based primers.

[0037] The 7:3 mass ratio allows the suspension to easily wet fine lines while having a sufficient metal volume fraction to cross the conductive percolation threshold, thus forming a continuous copper conductive layer after curing.

[0038] The copper powder is consistent with the subsequent copper sulfate pre-plating solution, which is beneficial to the interfacial bonding and the continuity of subsequent bottom copper deposition.

[0039] Compared to brushing or spraying, dip coating is more likely to penetrate fine textures through capillary action and ensure uniform coverage, reducing the exposed area of ​​the wax substrate.

[0040] Natural drying avoids warping of the wax material or pinholes in the coating caused by surface tension gradients due to heating, thus obtaining a stable metal layer with a thickness of 10–20 μm.

[0041] The continuous metal conductive layer, combined with the pre-embedded copper wire, makes the overall potential field more balanced, the initial plating nucleation is uniform, significantly reduces the unevenness in the weak current area and during electroplating, and reduces the probability of pinholes and pitting.

[0042] The copper powder base coating is consistent with the subsequent copper sulfate solution, resulting in higher interfacial affinity and bonding strength, and a smoother and denser base copper layer, thereby improving the bonding strength and thickness density of the platinum electroforming layer.

[0043] It should be noted that the wax blank with copper wire is manually installed on the stainless steel coated hanger.

[0044] If the thickness is less than 10 μm on the surface of the wax blank, it is easy to cause electrical discontinuity and high resistance, and increase the weak electrical area during the initial plating. If it is greater than 20 μm, it may increase internal stress or form a step edge at the corner, affecting the uniformity of subsequent thickness and demolding.

[0045] In at least one embodiment of this application, the formulation of the copper sulfate electrolyte is as follows: S20. Preparation of copper sulfate electrolyte: Prepare copper sulfate electrolyte with a concentration of 150-200 g / L and a sulfuric acid concentration of 130-150 ml / L. S21. The thickness of the electroplated copper layer on the initial plated part is 100-150μm.

[0046] Please refer to Figure 1 and Figure 2 In this embodiment, the copper sulfate electrolyte is prepared with a copper sulfate concentration of 150-200 g / L, a sulfuric acid concentration of 130-150 ml / L, an electroplating temperature of 20-25°C, and a current density of 1-4 A / dm² during electroplating.

[0047] The wax blank with the conductive layer is manually installed on the hanger, and the hanger with the conductive layer is installed in the electroforming cylinder 110. Acidic copper sulfate electrolyte is used to pre-plate the wax blank with the conductive layer as the cathode and copper as the anode to form a base copper layer with a thickness of 100–150 μm.

[0048] Compared to depositing platinum metal directly on a conductive coating, first constructing a continuous, flat, and ductile copper substrate layer can improve the interfacial adhesion of subsequent platinum electroformed layers and avoid local delamination caused by discrete particles or surface undulations in the conductive coating. Constructing a 100–150 μm copper substrate layer significantly improves the adhesion of the platinum electroformed layer, and under thick deposition conditions, the interfacial integrity is better and peeling is less likely to occur.

[0049] The continuous metallic phase of the base copper can homogenize the potential and current density, stabilizing the thickness profile and suppressing edge effects in complex curved surfaces and fine-textured areas. By homogenizing the current distribution and providing rigid support for the metal, the thickness density of complex curved surfaces and fine-textured areas is improved, edge thickening and underplating in weak areas are significantly reduced, and the thickness deviation of the casting is reduced.

[0050] Using an acidic copper sulfate electrolyte to first form a flat and dense metal substrate can also smooth micro-undulations, reduce the transmission of initial plating defects, and provide a stable interface for subsequent platinum layer deposition.

[0051] It should be noted that heat is generated during the electroplating process. At this time, a cooling machine can be used to cool the internal electroplating solution to ensure that the electroplating temperature is 20-25℃.

[0052] The copper at the anode undergoes an oxidation reaction, losing electrons to form copper ions that enter the electrolyte. The copper ions in the cathode electrolyte are reduced to metallic copper by the motor and adhere to the surface of the wax blank with a conductive layer.

[0053] In at least one embodiment of this application, step S3 specifically includes the following steps: S30. The initial plated part is removed from the copper sulfate electrolyte and cleaned a second time with pure water. After cleaning, the initial plated part is dried by blowing air at a temperature ≤40℃ to obtain the original mold.

[0054] Please refer to Figure 1 and Figure 2 In this embodiment, after completing the bottom copper pre-plating in step S2, the initial plated part is taken out of the copper sulfate electrolyte and kept in a position that facilitates drainage (e.g., the opening / blind hole is facing down when it is taken out of the tank, and it is suspended to drip dry for 10–60 s). Then, it is sequentially cleaned with secondary pure water and dried with low temperature blower to obtain the original mold.

[0055] First stage (rough wash): A continuous overflow pure water tank is used, combined with gentle agitation, air stirring, or low-power ultrasound (20–40 kHz) to enhance fluid exchange in blind holes and fine lines. This rapidly dilutes or removes Cu from the surface and crevices. 2+ SO4 2- With free acid.

[0056] The second stage (fine cleaning): The surface enters a pure water bath with even lower conductivity, and can also be gently agitated or ultrasonically cleaned. This thoroughly removes residual salts and organic matter, ensuring the surface reaches the cleanliness required for subsequent precious metal electroforming.

[0057] Two-stage cleaning is preferably achieved through counter-current water replenishment or overflow to maintain water quality stability. The final stage effluent water can be sampled and tested using online conductivity monitoring or copper ion test paper to prevent components from the previous stage from being carried into the subsequent platinum electroforming tank.

[0058] After secondary cleaning, the initially plated parts are dried in a blower, clean nitrogen, or air environment at a temperature ≤40°C. It is preferable to use an oil-free air source that has been filtered (de-oiled / de-watered), and the airflow is directed at gaps, blind holes, and fine lines to shorten the drying time and remove any entrained water.

[0059] Cu in copper sulfate electrolyte 2+ SO4 2- Free acids and possible trace organic substances, if introduced into the dinitrosodiammineplatinum (P salt) electrolyte, can easily disrupt the complexing agent balance, cause abnormal cathode polarization, and result in a darkened appearance. Secondary cleaning, through a staged process of coarse washing for dilution and fine washing for purification, significantly reduces residues in the previous tank, maintains the chemical stability and appearance consistency of the platinum electroforming tank, and extends the service life of the tank solution.

[0060] The wax material is sensitive to temperature and swelling. Using a gentle drying temperature of ≤40 ℃ can not only dry quickly, but also avoid softening, warping, or stress disturbance at the interface with the underlying copper layer.

[0061] Two-stage cleaning removes salt and surfactants, and low-temperature blowing removes entrained water, which shortens the residence time of bubbles on the cathode and stabilizes the initial crystal nucleus distribution, thereby improving film density and thickness uniformity.

[0062] In at least one embodiment of this application, the formulation of the dinitrosodiammineplatinum electrolyte is as follows: S40. Prepare an electrolyte for dinitrosodiamineplatin: 20-25 g / L dinitrosodiamineplatin, 50 ml / L sulfuric acid, complexing agent, stabilizer, and brightener, with a pH of 1-2; at 50°C, place the original mold in the electrolyte for electroplating to obtain a platinum-coated electrocast part.

[0063] Please refer to Figure 1 and Figure 2 In this embodiment, an electrolyte is prepared using dinitrosodiammineplatin with a concentration of 20-25 g / L as the main salt, and complexing agents, stabilizers, brighteners, etc. (thiourea, EDTA, ammonium triacetic acid, potassium sodium tartrate, etc.) are added. The pH value is adjusted to the range of 1-2 using sulfuric acid or boric acid to obtain the dinitrosodiammineplatin electrolyte.

[0064] At 50°C, the electrolyte of dinitrosodiammineplatin is used with a current density of 1-3 A / dm². The original mold is installed on the hanger and placed in the electrolyte of dinitrosodiammineplatin. Electroplating is performed with a titanium mesh as the anode and the hanger as the cathode. After electroplating to the target thickness, the power is turned off and the mold is removed to obtain a platinum electrocast part.

[0065] In low-pH electrolytes, Pt complexed with P salts is more stable, with weak hydrolysis and spontaneous decomposition tendencies, controllable cathodic polarization, and high nucleation density, which facilitates the acquisition of fine and dense morphologies. At the same time, the higher acidity combined with 50 mL / L sulfuric acid provides sufficient conductivity and a stable anodic electric field, reducing the risk of roughness and scorching of the generated platinum layer.

[0066] 50 ℃ increases the charge transfer and diffusion rate, which helps to improve the cathode current efficiency and the deposition of platinum layer on the surface. It also avoids the decomposition of complexing agents or brighteners and the aging of the bath caused by excessive temperature, making the surface of platinum electrocast parts smoother.

[0067] Complexing agents are used to buffer Pt 2+ Increase activity, broaden the usable potential window, and reduce abnormal substitution and coarse grains.

[0068] Stabilizers inhibit the spontaneous precipitation of colloidal platinum or metal particles, improving bath life and repeatability.

[0069] Brighteners increase nucleation density, refine grain size, and reduce bubble adhesion, which helps to achieve a bright white appearance and lower porosity.

[0070] Under the conditions of P salt 20–25 g / L, pH 1–2, and 50 ℃, combined with a complexing, stabilizing, and brightening system, the platinum layer exhibits a fine-grained, bright white morphology, with a significant reduction in pinholes, pitting, and blackening.

[0071] A platinum layer is deposited on a flat copper substrate and the electric field is kept stable by an inert titanium mesh, resulting in a stronger interface bond and a smaller thickness difference on complex curved surfaces.

[0072] At the anode, hydroxide ions in the electrolyte undergo an oxidation reaction, losing electrons to generate oxygen. At the cathode, platinum ions in the electrolyte gain electrons and are reduced to metallic platinum, which is deposited on the surface of the original mold.

[0073] In at least one embodiment of this application, during the electroplating process in step S2 and / or step 4: The copper sulfate electrolyte and / or the dinitrosodiammineplatinum electrolyte are circulated by a first water pump and a second water pump; and gas is introduced into the copper sulfate electrolyte and / or the dinitrosodiammineplatinum electrolyte for aeration.

[0074] In at least one embodiment of this application, the anode is placed in the anode placement area between the first spiral circulation tube 122 and the second spiral circulation tube 123. In the electroplating chamber, the second spiral circulation tube surrounds the electroplating area 123b, and the cathode is located in the electroplating area 123b. The first spiral circulation tube 122 is arranged around the second spiral circulation tube 123. During the electroplating process, the first water pump 120 pumps electrolyte into the electroplating chamber 110a through the first spiral circulation pipe 122, and the second water pump 121 pumps electrolyte from the electroplating chamber 110a through the second spiral circulation pipe 123. The tangential outlet 123a on the peripheral wall of the second spiral circulation pipe 123 faces the electroplating area 123b, and the tangential inlet 122a on the peripheral wall of the first spiral circulation pipe 122 faces the second spiral circulation pipe 123. The first spiral circulation pipe 122 and the second spiral circulation pipe 123 circulate to form a circumferential flow field around the electroplating area 123b.

[0075] Please refer to Figure 1 and Figure 2In this embodiment, during step S2 (bottom copper pre-plating) and / or step S4 (platinum electroforming), a first spiral circulation tube 122 and a second spiral circulation tube 123 are arranged in the electroplating chamber 110a: the cathode (wax blank or original mold with conductive layer) is placed in the second spiral circulation tube 123 and the electroplating chamber 110a together to form an electroplating area 123b, the cathode is located in the electroplating area 123b, and the first spiral circulation tube 122 is arranged around the second spiral circulation tube 123.

[0076] Electrolyte is pumped from the second water pump 121 to the second spiral circulation pipe 123 and sprayed into the electroplating area 123b through the tangential outlet 123a of its peripheral wall, forming a circumferential mainstream around the cathode surface; at the same time, the first water pump 120 draws back the peripheral electrolyte through the tangential inlet 122a of the peripheral wall of the first spiral circulation pipe 122, forming a closed circulation.

[0077] The dual loop of tangential jetting and circumferential back suction establishes a circumferential flow field around the electroplating area 123b, and the velocity difference between the two paths generates stable shearing and centrifugal effects near the cathode wall.

[0078] The combined effect of tangential small-scale shearing and slight centrifugation makes it easy for the hydrogen bubbles generated at the cathode to be torn into small bubbles and desorbed quickly, significantly shortening the residence time and shielding area. At the same time, the generated tiny hydrogen bubbles can separate from the platinum layer under the combined action of circulation force and centrifugal force, preventing hydrogen from adhering to the platinum layer.

[0079] Replacing point-by-point punching with circumferential shearing solves the problem of hydrogen bubble retention and improves quality and thickness uniformity, thus achieving a comprehensive result with lower defects and higher consistency in thick-layer electroforming of platinum.

[0080] For step S2, air or an inert gas can be used, while for step S4, an inert gas (such as nitrogen) is preferred.

[0081] The anode, driven by microbubbles of inert gas, rapidly carries away the generated oxygen, thus accelerating the oxidation reaction. A 10–20 µm microporous diffuser 130 is selected, with a starting gas flow rate of 0.05–0.2 vvm.

[0082] In deposits >10 μm or even thicker, timely defoaming results in a continuous and dense platinum layer with significantly reduced cracks, allowing for a moderate increase in average current density to increase production while ensuring smoothness.

[0083] In S4, the use of inert gas aeration can reduce dissolved oxygen and additive oxidation, and combine fine filtration and circulation.

[0084] It should be noted that a magnetically driven centrifugal pump is preferred, and the liquid passing material is PVDF / PTFE or an equivalent corrosion-resistant material.

[0085] In at least one embodiment of this application, during the electroplating process, the outlet 122a forms a circulating flow in the electroplating area 123b through the second water pump 121, so as to generate a flow rate difference between the second spiral circulation pipe 123 and the electroplating area 123b; The inlet 122a generates centrifugal suction in the anode placement area 122b and the electroplating area 123b through the first water pump 120, thereby generating negative pressure centrifugal force in the anode placement area 122b and the electroplating area 123b.

[0086] In this embodiment, during the electroplating process, an electrolyte is pumped in by a second water pump 121. The pumped electrolyte flows through the outlet 123a of the second spiral circulation pipe 123 toward the electroplating area 123b, so that the flow rate of the second spiral circulation pipe 123 is greater than the flow rate of the electroplating area 123b, thereby creating a flow rate difference between the second spiral circulation pipe 123 and the electroplating area 123b. Under the action of the flow rate difference, the hydrogen gas generated at the cathode is stripped off from the cathode and moved away from the cathode.

[0087] The inlet 122a draws out the electrolyte from the anode placement area 122b through the first water pump 120, causing the anode placement area 122b and the electroplating area 123b to form a centrifugal suction, thereby creating a negative pressure centrifugal force in the anode placement area 122b and the electroplating area 123b. This force removes hydrogen bubbles from the electroplating area 123b and oxygen from the anode placement area 122b, and then draws them out through the first spiral circulation pipe 122 to the filter chamber 110b for gas filtration, so as to prevent hydrogen from adhering to the platinum layer and avoid the problem of hydrogen embrittlement of the platinum layer.

[0088] Since the spiral directions of the first spiral circulation tube 122 and the second spiral circulation tube 123 are consistent and the flow rates are the same, the directions of the inner and outer circulations are consistent, resulting in better hydrogen extraction. This avoids turbulence affecting the effect of hydrogen stripping from the platinum layer, allowing hydrogen to be immediately discharged through the inner and outer circulations at the moment of generation, thus preventing hydrogen from adhering to the platinum layer.

[0089] In at least one embodiment of this application, the platinum electroforming process further includes: S5. Dewaxing and copper removal are performed on the platinum electrocasting part from step S4 to obtain a platinum casting. S6. Anneal and polish the platinum casting to obtain the finished platinum product.

[0090] Please refer to Figure 1 and Figure 2 In this embodiment, dewaxing: after the electroformed part is removed from the platinum bath, it is allowed to drain naturally for 10–60 seconds to prevent the platinum bath liquid from being carried into the subsequent hot water / solvent.

[0091] Immerse the workpiece in deionized hot water at 70–90 ℃ and supplement with low-power ultrasound at 20–40 kHz to soften and remove the wax core.

[0092] For deep or narrow cavities, short-term alternating soaking with ethyl acetate or petroleum ether can be added to hot water to dissolve residual wax film; after completion, rinse with hot water to remove solvent residue.

[0093] For all workpieces, it is preferable to drill holes (e.g., 0.4–0.6 mm) after electroplating to facilitate cleaning and subsequent dewaxing. At the same time, a slight vacuum or pressurized circulation should be used during dewaxing to accelerate the removal of wax from the inner cavity.

[0094] Rinse with hot water until the water is clear, there is no oil film, and there are no visible wax stains on the surface.

[0095] Copper removal: The dewaxed electrocast parts are immersed in a solution of nitric acid-water at a volume ratio of 1:1 and a temperature of 25–45 ℃ for etching. Nitric acid is used to selectively dissolve the underlying copper layer (including conductive copper coating and pre-plated base copper 100–150 μm). During the etching process, slight stirring or sonication is maintained to promote the escape of nitrogen oxide gas and the removal of reaction products. This process is repeated until no yellow smoke is generated and the acid solution no longer turns blue.

[0096] After removing the copper plating, place the plated parts in a large beaker of pure water and boil them on an electric stove to remove any residual nitric acid. Then, place them in an ultrasonic cleaner (frequency 40kHz) for a thorough cleaning.

[0097] Annealing: preferably in vacuum (≤10) -2 In a high-purity inert atmosphere (mbar) or high-purity inert atmosphere (Ar), the heating rate is 10℃ / min. The platinum casting is heated to 1300℃ and held for 0.5h, and the platinum casting is heated to 500℃ and held for 1h. The casting is then cooled to below 200℃ in the furnace and removed to avoid oxidation.

[0098] After annealing, the internal stress of electrodeposition decreases significantly, adsorbed and retained hydrogen is effectively expelled, and cracks, edge breakage and porous areas are significantly reduced under thick layer (>10 μm or even thicker) conditions.

[0099] Polishing: Place the annealed platinum castings into a polishing machine / grinding machine, add filler and water, and polish at 200 rpm for 1-2 hours. The surface of the plating becomes bright through friction with the filler. After polishing, screen out the plating, clean it in an ultrasonic cleaner, and then dry it to obtain the finished platinum product.

[0100] This invention provides a platinum electroforming apparatus 100 for implementing the platinum electroforming process described in any of the above claims, the platinum electroforming apparatus 100 comprising: The electroforming cylinder 110 has an electroplating chamber 110a and a filter chamber 110b inside. The first water pump 120 is installed inside the electroplating chamber 110a; The second water pump 121 is installed inside the electroplating chamber 110a; The first spiral circulation pipe 122 extends spirally upward in the vertical direction from the bottom wall of the electroplating chamber 110a. The first spiral circulation pipe 122 has an inlet 122a. The end of the first spiral circulation pipe 122 away from the bottom wall of the electroplating chamber 110a is connected to the filter chamber 110b through the first water pump 120. The second spiral circulation pipe 123 extends vertically upward from the bottom wall of the electroplating chamber 110a. The second spiral circulation pipe 123 and the electroplating chamber 110a form an electroplating area 123b. The second spiral circulation pipe 123 has an outlet 123a on the side near the electroplating area 123b. The first spiral circulation pipe 122 surrounds the second spiral circulation pipe 123. The end of the second spiral circulation pipe 123 near the bottom wall of the electroplating chamber 110a is connected to the filter chamber 110b through the second water pump 121.

[0101] Please refer to Figures 1-6 In this embodiment, during operation, the electrolyte in the filter chamber 110b is continuously pumped in the second spiral circulation pipe 123 and enters the electroplating area 123b from the outlet 123a. Affected by the position of the spiral channel and the outlet 123a, a circumferential or spiral liquid flow is formed around the cathode, establishing a velocity gradient in the electroplating area 123b and continuously surrounding the cathode boundary layer. Subsequently, the main stream is equipotentially drawn back by the inlet 122a of the first spiral circulation pipe 122 in the circumferential direction. After entering the filter chamber 110b through the first water pump 120 for impurity interception and temperature correction, it is replenished from the top to the second spiral circulation pipe 123.

[0102] This structure forms a closed loop consisting of a spiral pump flow, the main flow in the electroplating zone 123b, a spiral back suction, and a filter chamber 110b for replenishment. The combination of this structure and the flow path ensures that the electroplating zone 123b maintains continuous orderly circumferential shear and a stable temperature. Furthermore, the flow rate difference causes hydrogen bubbles generated on the cathode surface to detach and be carried away rapidly, resulting in a more uniform platinum layer and better heat dissipation.

[0103] Closed-loop flow reduces dead zones in the electroplating area 123b, thins and makes the boundary layer thinner and more uniform, stabilizes the supply of metal ions and additives, reduces thickness deviation, and suppresses edge burning and center underplating.

[0104] The residence time of hydrogen bubbles at the cathode interface is significantly shortened under the influence of the circumferential or spiral mainstream and the velocity difference, resulting in fewer defects such as pinholes, pits, and blackening, making the platinum or copper layer more dense and continuous.

[0105] The electroforming cylinder 110 is divided into an electroplating chamber 110a and a filter chamber 110b connected thereto. The two chambers are connected by a corrosion-resistant partition and a replaceable pipeline. The cylinder body and internal pipes are preferably made of PVDF, PTFE or polypropylene (PP).

[0106] Both the first water pump 120 and the second water pump 121 are installed inside the electroplating chamber 110a. Magnetic-driven centrifugal pumps are preferred to reduce the risk of shaft seal leakage.

[0107] The first water pump 120 is used to transport the tank liquid recovered through the first spiral circulation pipe 122 to the filter chamber 110b, and the second water pump 121 is used to supply liquid from the bottom of the electroplating chamber 110a to the second spiral circulation pipe 123 and spray it into the electroplating area 123b through the opening on its outer wall.

[0108] The first spiral circulation pipe 122 extends vertically upward from the bottom wall of the electroplating chamber 110a. The pipe wall is provided with an inlet 122a. The end of the pipe away from the bottom wall is connected to the filter chamber 110b via the first water pump 120. It is used to circumferentially draw back the bath liquid around the electroplating area 123b and send it into the filter chamber 110b.

[0109] The second spiral circulation pipe 123 also extends spirally upward from the bottom wall, and together with the electroplating chamber 110a, it encloses the electroplating area 123b. It has an outlet 123a on the side near the electroplating area 123b, and one end near the bottom wall is connected to the second water pump 121, and the other end is connected to the filter chamber 110b.

[0110] It should be noted that the inlet 122a is opened tangentially along its first spiral circulation pipe 122, and the outlet 123a is opened tangentially along its second spiral circulation pipe 123.

[0111] In at least one embodiment of this application, the outlet 123a is inclined relative to the axis of the second spiral circulation tube 123 toward the bottom wall of the electroplating area 123b; The inlet 122a is inclined relative to the axis of the first spiral circulation tube 122, away from the bottom wall of the electroplating area 123b; The platinum electroforming equipment 100 also includes: A microporous diffuser 130 is disposed at the end of the first spiral circulation pipe 122 away from the first water pump 120, and the microporous diffuser 130 is connected to an external air supply pipe.

[0112] Please refer to Figures 1-6In this embodiment, the tangential outlet 123a of the second spiral circulation pipe 123 near the electroplating area 123b is inclined relative to the pipe axis toward the bottom wall of the electroplating area 123b, so that the tank liquid pressurized by the second water pump 121 and propelled along the spiral path is sprayed out tangentially from the outlet 123a, forming a wall-attached spiral sweep flow near the cathode and establishing a velocity difference between the circumferential mainstream and the near wall.

[0113] The circumferential velocity simultaneously generates a radial pressure gradient (centrifugal field) within the electroplating area 123b. In conjunction with this, the tangential inlet 122a of the first spiral circulation pipe 122 is inclined relative to its axis away from the bottom wall of the electroplating area 123b, preferentially drawing back the mainstream from a higher position to avoid bottom-feedback drawing back and causing deposit entrainment and bottom backflow vortex. A microporous diffuser 130 connected to an external gas supply pipe is provided at the end of the first spiral circulation pipe 122 away from the first water pump 120. When necessary, microbubbles (preferably inert gas) are introduced to keep the gas and liquid at a small scale under the shear of the circumferential mainstream and sweep past the anode. At the same time, the microbubble disturbance introduced by the microporous diffuser 130 weakens bubble adhesion and acts as a bubble carrier to carry away residual gas.

[0114] During operation, the hydrogen bubbles generated on the cathode surface are first rapidly stripped off by near-wall shearing and dragging caused by the downward tangential jet; then they are pushed outward by centrifugal force from the circumferential mainstream and migrate to the outside of the electroplating area 123b.

[0115] Finally, the first spiral circulation pipe 122, arranged upwards, is drawn back into the filter chamber 110b to complete filtration and constant temperature before replenishment, thus realizing a continuous structure of downward tangential ejection, near-wall spiral shearing (flow velocity difference), centrifugal outward push, upward back suction closed loop, and micropore microbubble coordinated defoaming.

[0116] The suction of the first spiral circulation tube 122 and the second spiral circulation tube 123 significantly reduces the residence time and shielding area of ​​hydrogen at the cathode interface, and significantly reduces defects such as pinholes, pitting, and blackening caused by bubble shielding and interface contamination. The near-wall spiral sweeping makes the boundary layer thinner and more uniform, and with the upward back suction suppressing the bottom backflow vortex and bottom roll, the current density and mass transfer conditions tend to be uniform.

[0117] During thick-layer (>10μm to hundreds of micrometers) electroforming, due to continuous defoaming and stable mass transfer, the platinum layer is more continuous and dense, and the through cracks and porous areas are greatly reduced, avoiding the problem of hydrogen embrittlement.

[0118] It should be noted that the end of the first spiral circulation pipe 122 away from the first water pump 120 is the blocked end, and the end of the second spiral circulation pipe 123 away from the second water pump 121 is the blocked end.

[0119] Meanwhile, when the microporous diffuser 130 uses an inert gas, it can reduce dissolved oxygen and slow down the oxidation of additives, making the platinum layer more compact.

[0120] It should be noted that, please refer to Figure 7 In the process, when the second water pump 121 draws the liquid from the filter chamber 110b into the second spiral circulation pipe 123, a spiral flow is formed in the second spiral circulation pipe 123. The spiral flow enters the electroplating area 122b through the tangentially set outlet 123a along the dashed path marked 1 in the figure, generating a spiral circulation. A velocity difference is generated around the electroplating area 122b, making the velocity around the electroplating area 122b greater than the velocity in the electroplating area 122b itself. This results in the pressure around the electroplating area 122b being lower than the pressure at the center of the electroplating area 122b, attracting the generated hydrogen bubbles. At the same time, the first water pump 120 draws in the liquid through the inlet 122a along the dashed path marked 2 in the figure into the first spiral circulation pipe 122, forming a centrifugal flow path near the second spiral circulation pipe 123. This generates a force (making the flow path approximately S-shaped), drawing the hydrogen bubbles into the second spiral circulation pipe 123 for filtration in the filter chamber 110b.

[0121] Secondly, the oxygen generated by the anode 140 located between the first spiral circulation tube 122 and the second spiral circulation tube 123 can also be drawn into the first spiral circulation tube 122 through the inlet 122a for discharge.

[0122] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method of a platinum electroforming process, characterized by, The method of the platinum electroforming process comprises: Step S1: immerse the wax embryo in a copper powder mixture to form a conductive layer on the surface of the wax embryo, and obtain a wax embryo with a conductive layer; Step S2: place the wax embryo with a conductive layer in a copper sulfate electrolyte, use copper material as anode, and use the coated wax embryo as cathode for electroplating to obtain an initial plated part; Step S3: clean and dry the initial plated part to obtain a master mold; Step S4: use the master mold as cathode and titanium mesh as anode for electroplating in a bis-nitroso-diamino platinum electrolyte to obtain a platinum layer electroformed part.

2. The method of the platinum electroforming process according to claim 1, characterized in that, The specific steps of step S1 include: Insert a conductive copper wire into the wax embryo to form a wax embryo with a copper wire; Prepare a copper powder mixture by uniformly mixing ethyl acetate and ultra-fine copper powder at a mass ratio of 7:3 to obtain a copper powder mixture; Immerse the wax embryo with a copper wire in the copper powder mixture, then take it out and dry it naturally to form a conductive layer with a thickness of 10-20 μm on the surface of the wax embryo, and obtain the wax embryo with a conductive layer.

3. The method of the platinum electroforming process according to claim 1, characterized in that, The formula of the copper sulfate electrolyte includes: Prepare a copper sulfate electrolyte with a copper sulfate concentration of 150-200 g / L and a sulfuric acid concentration of 130-150 ml / L; Step S2 further includes: The thickness of the electroplated copper layer of the initial plated part is 100-150 μm.

4. The method of the platinum electroforming process according to claim 1, characterized in that, The specific steps of step S3 include: Take the initial plated part out of the copper sulfate electrolyte, clean it with pure water for the second time, and then dry the initial plated part by air blowing at a temperature of ≤40℃ to obtain the master mold.

5. The method of the platinum electroforming process according to claim 1, characterized in that, The formula of the bis-nitroso-diamino platinum electrolyte includes: Bis-nitroso-diamino platinum 20-25 g / L, sulfuric acid 50 ml / L, complexing agent, stabilizer, and brightener, pH value 1-2; Step S4 further includes: Electroplate the master mold in the bis-nitroso-diamino platinum electrolyte at 50℃ to obtain the platinum layer electroformed part.

6. The method of the platinum electroforming process according to claim 1, characterized in that, During the electroplating process of step S2 and / or step S4: Recycle the copper sulfate electrolyte and / or the bis-nitroso-diamino platinum electrolyte through the first water pump and the second water pump; And aerate the copper sulfate electrolyte and / or the bis-nitroso-diamino platinum electrolyte by introducing gas.

7. The method of the platinum electroforming process according to claim 6, characterized in that, The step of recycling the copper sulfate electrolyte and / or the bis-nitroso-diamino platinum electrolyte through the first water pump and the second water pump includes: Place the anode in the anode placement area between the first spiral circulation pipe and the second spiral circulation pipe; in the electroplating cavity, the second spiral circulation pipe is arranged to form an electroplating area, and the cathode is located in the electroplating area, and the first spiral circulation pipe is arranged around the second spiral circulation pipe; During the electroplating process, the first water pump pumps the electrolyte out of the electroplating cavity through the first spiral circulation pipe, and the second water pump pumps the electrolyte from the electroplating cavity through the second spiral circulation pipe, the tangential outlets on the circumferential wall of the second spiral circulation pipe face the electroplating area, the tangential inlets on the circumferential wall of the first spiral circulation pipe face the second spiral circulation pipe, and the first spiral circulation pipe and the second spiral circulation pipe circulate to form a circumferential flow field around the electroplating area.

8. The method of the platinum electroforming process according to claim 7, characterized in that, In the electroplating process, the outlet is connected to the second water pump to form a circulation in the electroplating area to generate a flow rate difference between the second spiral circulation pipe and the electroplating area; The inlet is connected to the first water pump to form a centrifugal suction in the anode placement area and the electroplating area to form a negative pressure centrifugal force in the anode placement area and the electroplating area.

9. A platinum electroforming apparatus for carrying out the method of the platinum electroforming process according to any one of claims 1 to 8, characterized in that The platinum electrocasting device comprises: An electrocasting cylinder, which is internally formed with an electroplating cavity and a filtering cavity; A first water pump, which is installed in the electroplating cavity; A second water pump, which is installed in the electroplating cavity; A first spiral circulation pipe, which spirally extends upward from the bottom wall of the electroplating cavity in the vertical direction, the first spiral circulation pipe is provided with an inlet, and the end of the first spiral circulation pipe away from the bottom wall of the electroplating cavity is connected to the filtering cavity through the first water pump; A second spiral circulation pipe, which spirally extends upward from the bottom wall of the electroplating cavity in the vertical direction, the second spiral circulation pipe and the electroplating cavity form an electroplating area, the second spiral circulation pipe is provided with an outlet on the side close to the electroplating area, the first spiral circulation pipe surrounds the second spiral circulation pipe, and the end of the second spiral circulation pipe close to the bottom wall of the electroplating cavity is connected to the filtering cavity through the second water pump.

10. The platinum electroforming apparatus of claim 9, wherein, The outlet is inclined relative to the axis of the second spiral circulation pipe and faces the bottom wall of the electroplating area; The inlet is inclined relative to the axis of the first spiral circulation pipe and faces away from the bottom wall of the electroplating area; The platinum electrocasting device further comprises: A microporous diffuser, which is arranged at the end of the first spiral circulation pipe away from the first water pump, and the microporous diffuser is connected to an external air supply pipeline.

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