A method for preparing a composite coating and applications thereof

Abstract

The present application belongs to the technical field of plating, in particular, to a preparation method of a composite plating layer and application thereof. The steps are as follows: oil removal, micro-etching, activation of the conductive substrate, then copper plating, deposition of microcrystals, preparation of a barrier layer, preparation of a filling layer, preparation of an alloy layer, and finally forming a composite plating layer on the conductive substrate. The composite plating layer is applied in a high-current connector. The composite plating layer prepared by the present application can be used in a high-current connector, and the plating layer comprises a mechanical interlocking structure formed by three-dimensional micron-sized copper dendrite crystals or micro-column arrays completely wrapped by nickel, and a Cu-Ag-Zn-Sn-Ni quinary nanoscale eutectic alloy transient liquid phase bonding layer generated in situ at the outermost layer of the silver layer and all interfaces between silver and nickel and copper. The present application improves the adhesion, wear resistance and electrical conductivity of the composite plating layer.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and in particular, to a method for preparing a composite coating and its application. Background Technology

[0002] In the field of electrical connectors, especially in high-power-density, high-current energy storage systems, connector terminals need to maintain excellent conductivity, mechanical reliability, and durability under long-term high-current loads. Traditional connector plating technology typically employs single-layer or multi-layer plating structures, such as copper plating, nickel plating, and silver plating, to balance conductivity, wear resistance, and corrosion resistance.

[0003] However, for high-current connectors in energy storage, pure copper-nickel-silver alloys have the following potential problems: Fretting wear: High current causes heat generation, and thermal expansion and contraction will cause minute movements on the contact surface, leading to wear and oxidation of the coating.

[0004] Insufficient hardness of the silver layer: Pure silver is too soft and is easily worn down with repeated insertions and removals.

[0005] Weak bonding: Multilayer metals are prone to delamination under high current thermal shock. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a method for preparing a composite coating and its application.

[0007] To solve its technical problem, the present invention adopts the following technical solution: In a first aspect, a method for preparing a composite coating includes the following steps: The conductive substrate is degreased, micro-etched, and activated, then copper is plated, microcrystals are deposited, a barrier layer is prepared, a filler layer is prepared, an alloy layer is prepared, and finally a composite coating is formed on the conductive substrate.

[0008] Furthermore, the conductive substrate is degreased, micro-etched, and activated, including the following steps: Immerse the conductive substrate in an alkaline degreasing solution at 40-80℃ and ultrasonically clean for 5-8 minutes. Then soak it in a micro-etching solution for 30-60 seconds until the surface turns pink and matte. Next, soak it in an activating solution for 10-20 seconds and finally rinse it with deionized water.

[0009] Furthermore, the alkaline degreasing solution includes sodium hydroxide and / or sodium carbonate; the micro-etching solution includes sodium persulfate and / or sulfuric acid; and the activating solution includes dilute sulfuric acid.

[0010] Furthermore, copper plating includes the following steps: After washing with water, the conductive substrate is immersed in an acidic brightening copper agent at a temperature of 20-30℃ and an A / dm². 2Electroplating at current density for 4-8 minutes forms a copper plating coating on a conductive substrate; Among them, acidic bright copper agents include at least one of copper sulfate, sulfuric acid, chloride ions, and acidic copper brighteners.

[0011] It should be noted that the copper plating coating is prepared first to make the surface of the contact parts smooth.

[0012] Furthermore, the deposition of microcrystals includes the following steps: The conductive substrate is transferred into a tank containing the first plating solution, and the plating is carried out at a temperature of 25-30℃ and a current density of 8-12 A / dm³. 2 Under these conditions, electroplating is performed using the first plating solution for 45-90 seconds to form microcrystals; The first plating solution includes copper sulfate pentahydrate and / or sulfuric acid.

[0013] It should be noted that the copper microcrystalline array is the conductive substrate. In this invention, it can also serve as a physical anchor point, providing a surface area greater than that of a flat surface.

[0014] In the first plating step, any leveling or brightening agent (such as polyethylene glycol, thiourea, etc.) is added, using a pure inorganic system to promote rough crystal growth.

[0015] This invention selects a current density of 8-12 A / dm. 2 Conventional processes only achieve 2-4 A / dm 2 This invention utilizes high current density to create apical dominance and generate dendrites.

[0016] The processing time of this invention is 45-90 seconds. The purpose of controlling the time in this way is to form micropillars / dendritices of appropriate height.

[0017] Furthermore, the barrier layer is prepared by the following steps: The conductive substrate is transferred into a tank containing a second plating solution, and the plating is carried out at a temperature of 40-60℃ and a current density of 1-2 A / dm³. 2 Under these conditions, electroplating is performed using a second plating solution for 2-3 minutes to form a barrier layer; The second plating solution includes at least one of nickel sulfate, nickel chloride, and boric acid.

[0018] It should be noted that the barrier layer prevents copper atoms from diffusing into the filling layer (silver layer), serving as the substrate for subsequent eutectic reactions. At transient high temperatures, Ni participates in complex interfacial reactions, generating a Ni-containing pentagonal eutectic phase, preventing excessive dissolution of the copper framework during the eutectic reaction.

[0019] This invention sets the current density to 1-2 A / dm 2Using low current ensures uniform plating capability, allowing nickel to be evenly coated on the sidewalls of copper dendrites.

[0020] Further, the filling layer is prepared, including the following steps: The conductive substrate is transferred into a tank containing a third plating solution. First, conventional direct current is applied at a temperature of 30-40℃ and a current density of 0.5-1.0 A / dm³. 2 Under these conditions, a filler layer is formed by electrodeposition using a third plating solution; The third plating solution includes at least one of potassium silver cyanide, potassium cyanide, eutectic agent, and reinforcing agent.

[0021] It should be noted that the current density in this invention is set to 0.5-1.0 A / dm. 2 Slow deposition ensures that silver ions can fill the framework.

[0022] Preferably, the eutectic agent includes at least one of zinc sulfate, stannous sulfate, and potassium pyrophosphate, and the reinforcing agent includes aminated graphene quantum dots.

[0023] It should be noted that Zn and Sn, as trace additives, are usually considered as impurities or added to increase hardness.

[0024] In this invention, it serves as an initiator for the transient liquid phase. Utilizing its low melting point, it melts first under localized hot spots excited by an acoustic-electric field, acting as a solvent to induce liquid-phase diffusion of high-melting-point Ag and Cu, achieving "cold welding" at low temperatures. Aminographene quantum dots can adsorb onto the surface of silver grains, inhibiting their growth; simultaneously, utilizing the quantum tunneling effect, high-speed electron channels are established at potential lattice mismatches in the eutectic layer.

[0025] Further, the alloy layer is prepared by the following steps: After preparing the filler layer, do not disconnect the power or remove the product from the electroplating tank. Instead, switch the power mode and activate the ultrasonic waves directly inside the electroplating tank. First, activate the 100-140kHz high-frequency ultrasonic waves, then switch the rectifier to pulse mode with a peak current density of 10⁻²² A / dm³. 2 The duty cycle is 5-12%, the frequency is 800-1200Hz, and the duration is 60-90 seconds.

[0026] It should be noted that high-frequency ultrasound, pulsed current, Zn, and Sn constitute an acoustic-thermal-electric coupling field. The collapse of cavitation bubbles from ultrasound generates instantaneous high temperatures in local micro-regions (which can also subside in a very short time), which, combined with the Joule heating of the pulsed current, causes Zn / Sn to melt without heating the entire plating bath.

[0027] Furthermore, after preparing the alloy layer, post-treatment is performed, which includes the following steps: cleaning the treated conductive substrate, then immersing it in an anti-silver tarnishing agent, and drying it with hot air. The anti-silver tarnishing agent includes benzotriazole (BTA) and / or octadecyl mercaptan and / or commercially available anti-silver tarnishing agents.

[0028] Secondly, the composite coating is applied in energy storage high-current connectors. The composite coating is prepared on the equipment or parts of the energy storage high-current connector, and the composite coating is prepared according to the preparation method of the composite coating described above.

[0029] The present invention has at least the following beneficial effects: The present invention provides a composite coating that can be used in high-current connectors. The coating includes a mechanically interlocking structure formed by a three-dimensional micron-sized copper dendrite or micropillar array completely encapsulated by nickel, and a Cu-Ag-Zn-Sn-Ni pentagonal nano-eutectic alloy transient liquid phase bonding layer generated in situ at the outermost layer of the silver layer and at all interfaces between silver and nickel and copper.

[0030] 1. Traditional multilayer coatings rely primarily on physical adsorption and limited mechanical interlocking, resulting in weak bonding. This invention constructs a copper microcrystalline array framework through anisotropic deposition and utilizes a co-induced acoustic-thermal-electric field in-situ liquid-phase transient eutectic process to generate a Cu-Ag-Zn-Sn-Ni pentagonal nano-eutectic alloy layer at the coating interface. This alloy layer forms a strong interdiffusion metallurgical bond with the underlying copper and nickel layers and the surface silver layer, improving coating adhesion and effectively resisting interlayer delamination caused by repeated insertion / removal, thermal cycling, and vibration.

[0031] 2. The unique three-dimensional skeleton-filler layer-alloy interface triple structure of the composite coating works synergistically to achieve wear resistance superior to traditional coatings. The three-dimensional skeleton composed of copper microcrystalline array and ultrathin nickel layer provides a mechanical anchoring effect; the in-situ generated nano-eutectic alloy layer further increases the adhesion of each layer; and amino-based graphene quantum dots, as nano-reinforcing phases, are dispersed in the silver layer, improving hardness and self-lubricating properties. This makes it particularly suitable for energy storage connector applications requiring frequent plugging and unplugging.

[0032] 3. This invention achieves a reduction in contact resistance through the construction of a multi-level conductive network. The dense and flat pure silver surface layer provides excellent surface conductivity; the highly oriented copper microcrystal array at the bottom layer and the highly conductive eutectic alloy layer form a low-resistance vertical conductive channel; and the uniformly dispersed graphene quantum dots enhance the integrity of the overall conductive network of the silver layer.

[0033] 4. By adjusting anisotropic deposition parameters (such as current density and time), eutectic-induced pulse parameters (duty cycle and frequency), and the composition of functional additives (such as eutectic agents and reinforcing agents), the microstructure, alloy phase composition, and mechanical / electrical properties of the coating can be controlled. For example, Example 2 shows that without the addition of graphene quantum dot reinforcing agents, the wear resistance is slightly reduced; adjusting the pulse duty cycle can optimize heat input and prevent the coating from scorching. This allows the present invention to flexibly adapt to connector requirements under different operating conditions (such as current load, insertion / removal frequency, and environmental corrosivity). Detailed Implementation

[0034] The technical solutions in some embodiments of this disclosure will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments provided in this disclosure, all other embodiments obtained by those skilled in the art are within the scope of protection of this disclosure.

[0035] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0036] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0037] Example 1 A method for preparing a composite coating, comprising the following specific steps: Prepare equipment: Select an electroplating tank made of PP or PVC. The tank should have a high-power ultrasonic vibrating plate installed at the bottom or sidewalls, with an ultrasonic frequency at least 28kHz for cleaning and stirring, and 120kHz for inducing eutectic reactions; its power density should be ≥0.5W / cm³. 2 .

[0038] The electroplating tank is equipped with titanium heating tubes and a circulating cooler for temperature control. It also has a circulating filtration function, with a continuous filter and a filter element with a precision of 5μm. The circulation rate is 4-6 times / hour of the tank volume.

[0039] Power supply system: uses a high-frequency pulse rectifier; output waveform: square wave pulse; frequency range: 0-5000Hz adjustable; duty cycle: 0-100% adjustable.

[0040] Anode configuration: Copper plating: Phosphor bronze balls are placed in a titanium basket.

[0041] Nickel plating: nickel-sulfur buckles or nickel-sulfur cakes, placed in a titanium basket.

[0042] Silver plating: Pure silver plate (purity ≥ 99.99%).

[0043] Prepare the ingredients: Alkaline degreasing solution: composed of 40g / L sodium hydroxide and 30g / L sodium carbonate.

[0044] Micro-etching solution: composed of 100 g / L sodium persulfate and 2% sulfuric acid by volume.

[0045] Activation solution: 10% dilute sulfuric acid (by volume).

[0046] Acidic copper brightener: Composed of 200g / L copper sulfate, 60g / L sulfuric acid, 60ppm chloride ions, and 5ml / L acidic copper brightener. The acidic copper brightener can be selected from Anmet Copper ULTRA brightener.

[0047] The first plating solution consists of 200 g / L copper sulfate pentahydrate and 55 g / L sulfuric acid.

[0048] The second plating solution consists of 250 g / L nickel sulfate, 40 g / L nickel chloride, and 35 g / L boric acid.

[0049] The third plating solution consists of 35 g / L potassium silver cyanide, 110 g / L potassium cyanide, eutectic agent, and reinforcing agent.

[0050] Eutectic agent: Composed of 0.5 g / L zinc sulfate and 0.3 g / L stannous sulfate. Before use, it needs to be complexed with potassium pyrophosphate. Specifically, zinc sulfate is slowly added dropwise to a potassium pyrophosphate solution, followed by the addition of stannous sulfate to form a complexing solution, thus obtaining the eutectic agent.

[0051] Enhancer: Aminated graphene quantum dots. Aminated graphene quantum dots N-150 from Suzhou Xianfeng Nanomaterials Technology Co., Ltd. were selected. Before use, the mixture was ultrasonically dispersed in water for 2 hours to obtain a 50 ml / L aminated graphene quantum dot dispersion.

[0052] The purity of the raw materials is generally selected to be electroplating grade.

[0053] Preparation using the above-mentioned raw materials: 1. Pretreatment of substrate: The conductive substrate is degreased, micro-etched, and activated. Specifically, the conductive substrate is immersed in an alkaline degreasing solution at 60°C and ultrasonically cleaned for 6 minutes. Then, it is soaked in a micro-etching solution for 45 seconds until the surface appears pink and matte. Then, it is soaked in an activation solution for 15 seconds and finally rinsed with deionized water.

[0054] After washing with water, the conductive substrate is immersed in an acidic bright copper agent at 25°C and 3 A / dm. 2 Electroplating at a current density for 6 minutes forms a bright, dense, and smooth copper plating coating on a conductive substrate, resulting in a pretreated substrate.

[0055] 2. Anisotropic sedimentation: The pretreated substrate is transferred into a tank containing the first plating solution, and the plating is carried out at a temperature of 25°C and a current density of 10 A / dm³. 2 Under these conditions, electroplating is performed using the first plating solution for 60 seconds to form an electrodeposited copper microcrystal array with a height of 6μm. The purpose is to grow a layer of fine "fluffy" copper dendrites on a bright copper base.

[0056] 3. Preparation of the nickel barrier layer: The substrate treated in step 2 is transferred into a tank containing the second plating solution, and the plating is carried out at a temperature of 50°C and a current density of 1.5 A / dm³. 2 Under these conditions, a second plating solution was used for electroplating treatment for 2.5 minutes to form an ultrathin nickel barrier layer of 0.6 μm on the copper microcrystal array of the substrate.

[0057] It should be noted that this preserves the morphology of the copper microcrystal array without flattening the aforementioned morphology.

[0058] 4. Preparation of the filler layer: The substrate treated in step 3 is transferred into a tank containing the third plating solution. Initially, conventional direct current is used at a temperature of 35°C and a current density of 0.8 A / dm³. 2 Under these conditions, a third plating solution is used for electrodeposition to form a filler layer, deposited to a total thickness of approximately 12 μm, until the surface is restored to a bright and smooth state.

[0059] The purpose of this is to use silver to fill the surface of the substrate, during which Zn and Sn, graphene quantum dots and silver are co-deposited.

[0060] 5. Preparation of alloy layer: After step 4 is completed, do not turn off the power or remove the product from the tank. Instead, switch the power mode and turn on the ultrasonic waves directly inside the electroplating tank.

[0061] First, turn on the 120kHz high-frequency ultrasonic wave, then switch the rectifier to pulse mode with a peak current density of 20 A / dm³. 2 The duty cycle is 8%, the frequency is 1000Hz, and the duration is 60 seconds.

[0062] It should be noted that high-frequency ultrasound has a strong cavitation heat effect, and the duty cycle parameter can prevent the coating from burning, utilizing only the peak energy.

[0063] The reaction mechanism is as follows: This step induces in-situ transient liquid-phase eutectic through the synergistic effect of acoustic-thermal-electric fields. Specifically, under the superposition of local hot spots generated by high-frequency ultrasonic cavitation and the thermal effect of high-pulse current, trace amounts of Zn and Sn elements inside the coating melt instantaneously, inducing a liquid-phase diffusion reaction at the interface between Ag and the underlying copper and nickel framework. After cooling, a Cu-Ag-Zn-Sn-Ni pentagonal nano-eutectic alloy layer is formed in situ at the interface.

[0064] 6. Post-treatment: After treatment, the substrate is rinsed with pure water, then immersed in an anti-silver discoloration protectant for 30 seconds, and dried with hot air. The anti-silver discoloration protectant includes benzotriazole (BTA) and / or octadecyl mercaptan and / or a commercially available anti-silver discoloration agent. In this embodiment, benzotriazole (BTA) is selected as the anti-silver discoloration protectant.

[0065] Post-processing is an optional step and can be selected according to actual needs.

[0066] Example 2 There are two differences compared to Example 1.

[0067] 1. No reinforcing agent is added to the third plating solution.

[0068] The third plating solution consists of 35 g / L potassium silver cyanide, 110 g / L potassium cyanide, eutectic agent, and reinforcing agent.

[0069] Eutectic agent: Composed of 0.5 g / L zinc sulfate and 0.3 g / L stannous sulfate. Before use, it needs to be complexed with potassium pyrophosphate. Specifically, zinc sulfate is slowly added dropwise to a potassium pyrophosphate solution, followed by the addition of stannous sulfate to form a complexing solution, thus obtaining the eutectic agent.

[0070] 2. In step 5, first turn on the 120kHz high-frequency ultrasonic wave, then switch the rectifier to pulse mode with a peak current density of 20 A / dm. 2 The duty cycle is 12%, the frequency is 1000Hz, and the duration is 60 seconds.

[0071] The rest is the same as in Example 1.

[0072] Example 3 There are two differences compared to Example 1: 1. In step 2, the current density is 12 A / dm². 2 Under these conditions, electroplating was performed using the first plating solution for 90 seconds to form an 8μm high electrodeposited copper microcrystal array.

[0073] 2. In step 5, first turn on the 120kHz high-frequency ultrasonic wave, then switch the rectifier to pulse mode with a peak current density of 22 A / dm. 2 The duty cycle is 10%, the frequency is 1000Hz, and the duration is 90 seconds.

[0074] The rest is the same as in Example 1.

[0075] Comparative Example 1 In this comparative example, steps 2 and 5 are omitted. The specific steps are as follows: 1. Pretreatment of substrate: The conductive substrate is degreased, micro-etched, and activated. Specifically, the conductive substrate is immersed in an alkaline degreasing solution at 60°C and ultrasonically cleaned for 6 minutes. Then, it is soaked in a micro-etching solution for 45 seconds until the surface appears pink and matte. Then, it is soaked in an activation solution for 15 seconds and finally rinsed with deionized water.

[0076] After washing with water, the conductive substrate is immersed in an acidic bright copper agent at 25°C and 3 A / dm. 2 Electroplating at a current density for 6 minutes forms a bright, dense, and smooth copper plating coating on a conductive substrate, resulting in a pretreated substrate.

[0077] 2. Preparation of the nickel barrier layer: The pretreated substrate is transferred into a tank containing the second plating solution, and the plating is carried out at a temperature of 50°C and a current density of 1.5 A / dm³. 2 Under these conditions, a second plating solution was used for electroplating for 2.5 minutes to form a 0.6 μm nickel barrier layer on the copper microcrystal array of the substrate.

[0078] 3. Preparation of the filler layer: The substrate treated in step 2 is transferred into a tank containing the third plating solution. Initially, conventional direct current is used at a temperature of 35°C and a current density of 0.8 A / dm². 2 Under these conditions, a third plating solution is used for electrodeposition to form a filler layer, deposited to a total thickness of approximately 12 μm, until the surface is restored to a bright and smooth state.

[0079] 4. Post-treatment: The treated substrate is rinsed with pure water, then immersed in an anti-silver discoloration protectant for 30 seconds, and dried with hot air. The anti-silver discoloration protectant includes benzotriazole (BTA) and / or octadecyl mercaptan and / or a commercially available anti-silver discoloration agent. In this embodiment, benzotriazole (BTA) is selected as the anti-silver discoloration protectant.

[0080] The rest is the same as in Example 1.

[0081] Applications: The composite coating of this invention can be applied to high-current energy storage connectors. For example, a conductive substrate can be selected as the connector terminal.

[0082] The composite coatings of Examples 1-3 and Comparative Example 1 were tested below.

[0083] Based on the application scenarios of high-current energy storage connectors, copper (T2 copper) with a diameter of 5mm and a thickness of 1mm was selected as the conductive substrate sample.

[0084] Detection: 1. Use the cross-cut test and 3M tape tear test to measure the adhesion of the coating.

[0085] Testing steps: Use a standard cross-cutting tool to vertically cut 25 lines on the coating surface to form a grid shape.

[0086] Apply 15N of force to scratch along the longitudinal and transverse directions, ensuring the scratches are clear and penetrate the coating.

[0087] To test adhesion strength using 3M tape, firmly adhere the tape to the marked area, then forcefully tear off the tape and check if the coating has peeled off. Adhesion strength is graded from 0 (no peeling) to 5 (severe peeling).

[0088] The results were as follows: Example 1 was grade 0, indicating no peeling; Example 2 was grade 0, indicating no peeling; Example 3 was grade 0, indicating no peeling; Comparative Example 1 was grade 1, indicating slight peeling at the edges.

[0089] 2. Use the insertion and removal test to measure the wear life.

[0090] Testing Procedure: Refer to EIA-364-09 "Test Method for Mating and Removal Durability of Electrical Connectors". Set up a standard mating and removal test device to allow the sample to repeatedly perform mating and removal actions during the mating and removal process.

[0091] Specifically, an automatic insertion and removal life tester is used as the testing equipment. The plating sample is used as a movable plug and paired with a standard gold-plated socket. The socket springs ensure stable contact pressure.

[0092] Test conditions: Each insertion and removal takes about 1 second, with a frequency of 20 times per minute, and the insertion and removal test is carried out until the sample shows obvious wear or contact failure.

[0093] The results showed that in Example 1, the number of insertion and removal cycles was >10,000, and no wear or electrical connection failures were observed.

[0094] Example 2: After more than 8,000 insertion and removal cycles, no wear or electrical connection failure was observed.

[0095] Example 3: After more than 9,000 insertion and removal cycles, no wear or electrical connection failure was observed.

[0096] Comparative Example 1: After 1500 insertions and removals, copper layer exposure occurred.

[0097] 3. Contact resistance Test Procedure: Refer to EIA-364-23 "Test Method for Contact Resistance of Electrical Connectors" and connect the test circuit using the four-wire method (Kelvin connection method). Connect the current lead to both ends of the sample away from the contact point, and connect the voltage measurement lead directly near the contact point to eliminate the resistance of the wires and the sample body.

[0098] Apply a constant DC test current of 1A to the test circuit. After the reading stabilizes, record the contact resistance value displayed by the microohmmeter.

[0099] The results were as follows: the contact resistance of Example 1 was 8.2 μΩ, the contact resistance of Example 2 was 11.5 μΩ, the contact resistance of Example 3 was 8.8 μΩ, and the contact resistance of Comparative Example 1 was 32 μΩ.

[0100] Analysis: Example 1 contains a reinforcing agent, while Example 2 does not. Graphene quantum dots, as a nanoscale reinforcing phase, are dispersed in the silver filler layer, playing a role in dispersion reinforcement and self-lubrication, thereby improving the hardness, wear resistance, and conductivity of the coating.

[0101] Example 3 increased the height of the copper microcrystals and the pulse current intensity, resulting in excellent wear resistance and contact resistance, but slightly inferior to Example 1. This indicates that excessively high microcrystal height may lead to difficulties in achieving complete planarization of the subsequent filler layer, or uneven energy distribution during the eutectic reaction. The parameters of Example 1 are preferred.

[0102] Compared with Comparative Example 1, Examples 1-3 demonstrate that this invention solves the problem of plating wear caused by frequent insertion and removal of energy storage connectors under high current, extending their lifespan several times over. Ultra-low resistance effectively reduces heat generation during high-current operation, improving system safety and meeting the application requirements of high-current connectors. The in-situ induced liquid-phase transient eutectic process solves the problem of easy delamination and peeling at dissimilar metal (copper / nickel / silver) interfaces.

[0103] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for preparing a composite coating, characterized in that, Includes the following steps: The conductive substrate is degreased, micro-etched, and activated, then copper is plated, microcrystals are deposited, a barrier layer is prepared, a filler layer is prepared, an alloy layer is prepared, and finally a composite coating is formed on the conductive substrate.

2. The method for preparing a composite coating according to claim 1, characterized in that, The conductive substrate undergoes degreasing, micro-etching, and activation, including the following steps: Immerse the conductive substrate in an alkaline degreasing solution at 40-80℃ and ultrasonically clean for 5-8 minutes. Then soak it in a micro-etching solution for 30-60 seconds until the surface turns pink and matte. Next, soak it in an activating solution for 10-20 seconds and finally rinse it with deionized water.

3. The method for preparing a composite coating according to claim 1, characterized in that, Alkaline degreasing solutions include sodium hydroxide and / or sodium carbonate; micro-etching solutions include sodium persulfate and / or sulfuric acid; activating solutions include dilute sulfuric acid.

4. The method for preparing a composite coating according to claim 1, characterized in that, Copper plating includes the following steps: After washing with water, the conductive substrate is immersed in an acidic brightening copper agent at a temperature of 20-30℃ and an A / dm². 2 Electroplating at current density for 4-8 minutes forms a copper plating coating on a conductive substrate; Among them, acidic bright copper agents include at least one of copper sulfate, sulfuric acid, chloride ions, and acidic copper brighteners.

5. The method for preparing a composite coating according to claim 1, characterized in that, The deposition of microcrystals includes the following steps: The conductive substrate is transferred into a tank containing the first plating solution, and the plating is carried out at a temperature of 25-30℃ and a current density of 8-12 A / dm³. 2 Under these conditions, electroplating is performed using the first plating solution for 45-90 seconds to form microcrystals; The first plating solution includes copper sulfate pentahydrate and / or sulfuric acid.

6. The method for preparing a composite coating according to claim 1, characterized in that, The preparation of the barrier layer includes the following steps: The conductive substrate is transferred into a tank containing a second plating solution, and the plating is carried out at a temperature of 40-60℃ and a current density of 1-2 A / dm³. 2 Under these conditions, electroplating is performed using a second plating solution for 2-3 minutes to form a barrier layer; The second plating solution includes at least one of nickel sulfate, nickel chloride, and boric acid.

7. The method for preparing a composite coating according to claim 1, characterized in that, The preparation of the filler layer includes the following steps: The conductive substrate is transferred into a tank containing a third plating solution. First, conventional direct current is applied at a temperature of 30-40℃ and a current density of 0.5-1.0 A / dm³. 2 Under these conditions, a filler layer is formed by electrodeposition using a third plating solution; The third plating solution includes at least one of potassium silver cyanide, potassium cyanide, eutectic agent, and reinforcing agent.

8. The method for preparing a composite coating according to claim 7, characterized in that, The eutectic agent includes at least one of zinc sulfate, stannous sulfate, and potassium pyrophosphate, and the reinforcing agent includes amino-based graphene quantum dots.

9. The method for preparing a composite coating according to claim 1, characterized in that, The preparation of the alloy layer includes the following steps: After preparing the filler layer, do not disconnect the power or remove the product from the electroplating tank. Instead, switch the power mode and activate the ultrasonic waves directly inside the electroplating tank. First, activate the 100-140kHz high-frequency ultrasonic waves, then switch the rectifier to pulse mode with a peak current density of 10⁻²² A / dm³. 2 The duty cycle is 5-12%, the frequency is 800-1200Hz, and the duration is 60-90 seconds.

10. A composite coating is used in high-current energy storage connectors, characterized in that, A composite coating is prepared on a device or component of an energy storage high-current connector, the composite coating being prepared by a method according to any one of claims 1-9.