Aluminum film plating process for surface oxidation resistance of copper base material

Abstract

The invention provides an anti-oxidation aluminum film plating process for the surface of a copper base material, which comprises the following specific steps: S1, soaking and washing the copper base material in an acid solution, and then soaking the copper base material in a palladium chloride solution for activation, washing and oxidation treatment to obtain a base material I; s2, the base material I is immersed in a cobalt plating solution, current is applied, washing is carried out after electroplating is completed, and if micropores and microcracks exist in a plating layer, tissue densification treatment is carried out, and a base material II is obtained; s3, after cleaning and activating the base material II, immersing the base material II into a tin plating solution, applying current, washing after tin plating is completed, and if micropores and microcracks exist in a plating layer, performing tissue densification treatment to obtain a base material III; s4, the base material III is treated with an alkaline cleaning agent, washed, immersed in an aluminum plating solution, applied with current and washed after aluminum plating is completed, if micropores and microcracks exist in a plating layer, the structure is subjected to fine densification treatment, and a base material IV is obtained; and S5, the base material IV is subjected to chemical polishing, washing and drying, and the copper base material is obtained. According to the invention, by combining multiple plating layers with pulse electroplating, finer and more uniform plating layers are generated, and the stability and wear resistance of the plating layers are improved.

Description

Technical Field

[0001] The invention relates to the technical field of copper-aluminum conversion wiring, and in particular to an aluminum film plating process for anti-oxidation of the surface of a copper substrate. Background Art

[0002] Miniature Circuit Breaker (MCB) is a common circuit protection device widely used in residential, commercial and industrial electrical systems. Its terminals are usually made of copper, mainly because copper has excellent electrical conductivity, thermal conductivity and mechanical strength, which can ensure the reliability and stability of electrical connections. Currently, most of the existing miniature circuit breaker terminals are made of copper. Copper terminals can only connect copper wires. However, in the actual wiring process, you may encounter situations where the wires are aluminum wires. In this case, a copper-aluminum conversion joint is usually used to connect the aluminum wire to the copper terminal. The copper-aluminum transition joint is a specially designed connector with copper material on one end and aluminum material on the other end. A reliable connection between copper and aluminum is achieved by welding or crimping. However, this type of joint is large in size and difficult to use in installation environments with limited space.

[0003] In current technology, a layer of aluminum can be plated on the outer surface of a copper substrate. This not only saves space, but also provides a larger contact area and more uniform contact, thereby reducing contact resistance and simplifying the installation process. However, although a layer of aluminum film is formed on the surface of the copper substrate, the aluminum and copper are still in direct contact at certain microscopic interfaces. Because the potential of aluminum is lower than that of copper, when aluminum and copper are in direct contact, a battery effect forms at the contact point in a humid environment, causing electrochemical corrosion. This corrosion not only leads to poor electrical contact and increased contact resistance, but can also cause the temperature of the connection to rise, further exacerbating the corrosion process, and ultimately may cause the joint to fail, or even cause safety hazards such as fire. Summary of the Invention

[0004] In view of this, the present invention proposes an aluminum film plating process for anti-oxidation of the surface of a copper substrate to solve the problems existing in the above technical background.

[0005] The technical solution of the present invention is achieved as follows:

[0006] A process for coating an aluminum film on a copper substrate surface to prevent oxidation, comprising the following steps:

[0007] S1, immersing a copper substrate in an acidic solution, ultrasonically treating, washing, then immersing the substrate in a palladium chloride solution for activation, washing, and finally oxidizing to obtain substrate I;

[0008] S2, immersing substrate I in a cobalt plating solution, applying current while stirring the cobalt plating solution, washing the surface of the substrate after electroplating, and performing a microstructure refinement treatment if micropores and microcracks are present in the coating to obtain substrate II;

[0009] S3, after cleaning and activating the substrate II, immersing it in a tinning solution, applying current, and washing the surface of the substrate after the tinning is completed. If micropores and microcracks exist in the coating, a microstructure refinement treatment is performed to obtain substrate III;

[0010] S4. Treat substrate III with an alkaline cleaning agent, wash it, immerse it in an aluminum plating solution, apply current, and wash the surface of the substrate after the aluminum plating is completed. If micropores and microcracks exist in the coating, perform a microstructure refinement treatment to obtain substrate IV.

[0011] S5. Chemically polishing the substrate IV, washing it, and drying it to obtain the target copper substrate.

[0012] Furthermore, in step S1, the oxidation treatment is specifically:

[0013] (1) Micro-arc oxidation treatment: Prepare a micro-arc oxidation device, including a power supply, a reaction tank, a cathode, and an anode. Place the copper substrate as the anode, place the cathode in the reaction tank, and put the electrolyte in the reaction tank. Start the power supply. The arc in the electrolyte generates a local high temperature on the surface of the copper substrate, promoting the surface oxidation reaction to form an oxide ceramic coating.

[0014] (2) washing the copper substrate treated by micro-arc oxidation in step (1), drying, heating, and cooling.

[0015] Oxidation treatment enhances the adhesion and corrosion resistance of the coating. During the micro-arc oxidation process, a dense oxide film composed of copper oxide and copper-zinc oxide forms on the copper surface, significantly improving its corrosion resistance, hardness, and wear resistance. The ceramic oxide film formed by micro-arc oxidation has a high inherent bonding strength, which helps improve the adhesion of the coating. This is because the oxide film reduces direct contact between the substrate and the coating, reducing galvanic corrosion caused by the potential difference. In electroless plating, the large potential difference between the substrate and the coating can easily lead to severe galvanic corrosion. Forming a dense oxide film as an intermediate layer on the copper surface effectively reduces this corrosion risk, thereby improving the corrosion resistance and adhesion of the overall coating. Furthermore, the oxide film formed during micro-arc oxidation is primarily composed of stable oxides that are resistant to dissolution or reaction in the electroless plating solution, ensuring a stable bond between the coating and the substrate and preventing coating detachment. Therefore, the oxide film formed on the copper surface does not affect the original properties. In fact, its dense and uniform structure helps the cobalt plating layer form a smoother and more continuous coverage, further improving conductivity and adjusting magnetic properties.

[0016] Furthermore, in step (1), the power supply setting parameters are: voltage 200-600V, current density 20-100A / dm 2 , the duty cycle is 5%-20%, and the frequency is 50-3000Hz.

[0017] Furthermore, in step (2), the heating is specifically as follows: first heating to 100-200°C and maintaining for 20-30 minutes, then heating to 200-500°C and maintaining for 20-30 minutes.

[0018] Raise the temperature to 100-200℃ to eliminate the stress in the workpiece, and then raise the temperature to 200-500℃ to allow the heat to fully penetrate into the workpiece, melt the surface of the oxide film, fill the pores and cracks, and enhance the density of the film.

[0019] Furthermore, in steps S2-S4, the applied current is a pulse current, wherein the pulse frequency of step S2 is 1000 Hz and the duty cycle is 50%, the pulse frequency of step S3 is 500 Hz and the duty cycle is 60%, and the pulse frequency of step S4 is 2000 Hz and the duty cycle is 40%.

[0020] Applying pulsed current can produce a finer, more uniform coating, thereby improving its stability and wear resistance. Without increasing the coating thickness, it optimizes its microstructure and performance, improves the surface conductivity and weldability of the substrate, reduces the porosity of the coating, improves the hardness and wear resistance of the coating, and reduces the impurity content in the coating. In addition, the current changes during pulse plating can promote the interfacial reaction between the substrate and the coating, improving the adhesion of the coating. Pulse plating can also reduce internal stress in the coating and reduce the risk of cracking by adjusting the pulse parameters. During the pulse plating process, hydrogen molecules have the opportunity to desorb from the coating, reducing the occurrence of hydrogen embrittlement and improving the physical properties of the coating.

[0021] Furthermore, in steps S2-S4, the electroplating is carried out in a closed environment, using inert gas for rapid pressurization and gradual decompression. The air pressure in the sealed environment is 1-5 atmospheres. After rapid pressurization to 5 atmospheres, the substrate is deposited in the plating solution, and then gradually decompressed to 3 atmospheres to achieve a multi-layered coating structure.

[0022] Electroplating in a closed, high-pressure environment can achieve higher density and lower porosity in the cobalt layer. This environment helps inhibit the formation of bubbles and reduce pores in the coating, thereby improving its corrosion resistance and wear resistance. Cobalt deposition is performed under high pressure to improve the density and adhesion of the cobalt layer.

[0023] Furthermore, in steps S2-S4, the substrate surface needs to be heat treated after washing, specifically: first heating to 100-150°C and holding for 10 minutes, then continuing to heat to 200°C and holding for 10 minutes, and then cooling and performing subsequent operations.

[0024] Heat treatment can promote mutual diffusion between the plating solution and the copper substrate, enhance the bonding force between the layers, help eliminate residual stress within the coating, improve its stability, and further improve the corrosion resistance and wear resistance of the coating. It is especially suitable for application scenarios that need to withstand extreme environments.

[0025] Furthermore, in steps S2-S4, the tissue refinement process is specifically as follows:

[0026] (1) Immerse the plated part in a 0.8-1.2 mol / L phosphoric acid or sulfuric acid solution, connect the plated part to the anode, and use a stainless steel or lead plate as the cathode. Apply a voltage of 6-12 V to cause an anodic reaction on the surface of the plated part to remove surface irregularities and impurities.

[0027] (2) Place the plated part in an annealing furnace with a protective atmosphere, heat to 300-400°C for 30-120 minutes, and cool to room temperature;

[0028] (3) The plated parts are chemically polished for 10 minutes, washed, and placed in the electroplating solution for electroplating again to ensure that the coating is uniform and free of micropores and microcracks.

[0029] Furthermore, in step S1, the acidic solution is dilute hydrochloric acid or sulfuric acid with a concentration of 0.2-0.5 mol / L; the ultrasonic treatment is performed at 20-40 kHz and 25-30° C. for 3-5 min; the concentration of the palladium chloride solution is 0.002-0.005 mol / L; and the activation is performed at 20-25° C. for 2-4 min.

[0030] In step S2, the cobalt plating solution comprises: 100-200 g / L of cobalt sulfate, 30-50 g / L of sodium chloride, and 30-40 g / L of boric acid;

[0031] In step S3, the tin plating solution includes: 40-60 g / L of tin chloride, 50-100 g / L of sulfuric acid, and 10-20 g / L of citric acid;

[0032] In step S4, the aluminum plating solution includes: 150-250 g / L of aluminum chloride, 50-100 g / L of magnesium salt, and 30-60 g / L of dimethylformamide.

[0033] Furthermore, the cobalt plating solution, tin plating solution and aluminum plating solution also include 0.02 g / L of thiourea, 0.2 g / L of benzenesulfonic acid, 0.5 g / L of polyethylene glycol, 0.2 g / L of 2-mercaptobenzothiazole, 0.2 g / L of sodium lauryl sulfate, 0.2 g / L of nonylphenol polyoxyethylene ether, 0.2 g / L of gelatin, and 0.2 g / L of albumin.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention adopts a multi-layer plating process and utilizes the electrochemical properties of different metals to reduce the risk of electrochemical corrosion. A thin layer of cobalt is introduced as an intermediate layer between tin and copper, which can effectively inhibit the diffusion of copper atoms and reduce the formation of intermetallic compounds, thereby significantly improving the stability of the coating. Cobalt has a relatively positive electrode potential and strong corrosion resistance, which helps to form an effective isolation layer between copper and aluminum. This multi-layer structure not only improves the mechanical strength, but also significantly reduces the risk of electrochemical corrosion between the layers and reduces the difference in electrochemical activity between aluminum and the substrate.

[0036] 2. The present invention oxidizes the copper substrate to form a dense oxide film composed of copper oxide and copper-zinc oxide on the copper material surface, significantly improving its corrosion resistance, hardness, and wear resistance. The presence of the oxide film can reduce direct contact between the substrate and the coating, reducing galvanic corrosion caused by potential differences. By forming a dense oxide film as an intermediate layer on the copper surface, the risk of galvanic corrosion can be effectively reduced, thereby improving the corrosion resistance and bonding strength of the overall coating, ensuring a stable bond between the coating and the substrate, and preventing the coating from falling off.

[0037] 3. The present invention can produce a finer and more uniform coating by combining multiple coatings with pulse electroplating, improve its stability and wear resistance, and optimize its microstructure and performance without increasing the thickness of the coating. The current change of pulse electroplating can promote the interface reaction between the substrate and the coating, and improve the adhesion of the coating. Pulse electroplating reduces the internal stress in the coating and reduces the risk of cracking by adjusting the pulse parameters. During the pulse electroplating process, hydrogen molecules have the opportunity to desorb from the coating, reducing the occurrence of hydrogen embrittlement and improving the physical properties of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0039] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0040] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0041] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0042] Example 1

[0043] S1. Immerse the copper substrate in a 0.3 mol / L dilute hydrochloric acid or sulfuric acid solution, ultrasonically treat at 30 kHz and 28°C for 4 min, wash to remove residual acid, then immerse the substrate in a 0.004 mol / L palladium chloride solution, activate it at 23°C for 3 min, wash it, and finally oxidize it to obtain substrate I;

[0044] Among them, the specific steps of oxidation treatment are:

[0045] (1) Micro-arc oxidation treatment: Prepare micro-arc oxidation equipment, including power supply, reaction tank, cathode and anode. Place the copper substrate as the anode, place the cathode in the reaction tank, and put the electrolyte in the reaction tank. Start the power supply. The power supply setting parameters are: voltage 200V, current density 20A / dm 2 , the duty cycle is 5%, the frequency is 80Hz, the arc in the electrolyte generates local high temperature on the surface of the copper substrate, promoting the surface oxidation reaction and forming an oxide ceramic coating;

[0046] (2) washing the copper substrate treated by micro-arc oxidation in step (1) to remove residual electrolyte on the surface, drying the copper substrate in a clean environment, heating the copper substrate to 100° C. and holding it for 20 minutes to eliminate stress within the workpiece, then heating it to 200° C. and holding it for 20 minutes to allow heat to fully penetrate into the interior of the workpiece, melting the oxide film surface, filling pores and cracks, and enhancing the density of the film layer, and finally cooling it naturally to room temperature to remove oxide scale and impurities on the surface;

[0047] S2, immersing substrate I in a cobalt plating solution (cobalt sulfate 100g / L, sodium chloride 30g / L and boric acid 30g / L, thiourea 0.02g / L, benzenesulfonic acid 0.2g / L, polyethylene glycol 0.5g / L, 2-mercaptobenzothiazole 0.2g / L, sodium lauryl sulfate 0.2g / L, nonylphenol polyoxyethylene ether 0.2g / L, gelatin 0.2g / L, albumin 0.2g / L), applying a pulse current with a pulse frequency of 1000Hz and a duty cycle of 50%. During the electroplating process, the plating solution is slightly stirred to ensure a uniform coating. After the electroplating is completed, the surface of the substrate is washed with deionized water, and after rinsing, heat treatment is performed, first heating to 100°C for 10min, then continuing to heat to 200°C for 10min, cooling, and if micropores and microcracks are present in the coating, a tissue refinement treatment is performed to obtain substrate II;

[0048] S3. After cleaning and activating substrate II, immerse it in a tin plating solution (40 g / L tin chloride, 50 g / L sulfuric acid and 10 g / L citric acid, 0.02 g / L thiourea, 0.2 g / L benzenesulfonic acid, 0.5 g / L polyethylene glycol, 0.2 g / L 2-mercaptobenzothiazole, 0.2 g / L sodium lauryl sulfate, 0.2 g / L nonylphenol polyoxyethylene ether, 0.2 g / L gelatin, 0.2 g / L albumin), apply a pulse current with a pulse frequency of 500 Hz and a duty cycle of 60%. After the tin plating is completed, wash the surface of the substrate. If micropores and microcracks exist in the coating, perform a tissue refinement treatment to obtain substrate III.

[0049] S4. Treat substrate III with an alkaline detergent, wash it, and immerse it in an aluminum plating solution (150 g / L aluminum chloride, 500 g / L magnesium salt, 30 g / L dimethylformamide, 0.02 g / L thiourea, 0.2 g / L benzenesulfonic acid, 0.5 g / L polyethylene glycol, 0.2 g / L 2-mercaptobenzothiazole, 0.2 g / L sodium lauryl sulfate, 0.2 g / L nonylphenol polyoxyethylene ether, 0.2 g / L gelatin, and 0.2 g / L albumin). Apply a pulse current at a pulse frequency of 2000 Hz and a duty cycle of 40%. After the aluminum plating is completed, wash the surface of the substrate. If micropores and microcracks are present in the coating, perform a tissue refinement treatment to obtain substrate IV.

[0050] Among them, in steps S2-S4, electroplating needs to be carried out in a closed environment, using inert gas for rapid pressurization and gradual decompression. The air pressure in the sealed environment is 1-5 atmospheres. After rapid pressurization to 5 atmospheres, the substrate is deposited in the plating solution, and then gradually decompressed to 3 atmospheres to achieve a multi-layered coating structure.

[0051] If micropores and microcracks exist in the coating in steps S2-S4, a microstructure refinement treatment is performed, specifically:

[0052] (1) Immerse the plated part in a 1.0 mol / L phosphoric acid or sulfuric acid solution, connect the plated part to the anode, and use a stainless steel or lead plate as the cathode. Apply a 6 V voltage to cause an anodic reaction on the surface of the plated part to remove surface irregularities and impurities.

[0053] (2) Place the plated part in an annealing furnace with a protective atmosphere, heat to 300°C for 30 minutes, and cool to room temperature;

[0054] (3) The plated parts are chemically polished for 10 minutes, washed with deionized water, and then placed in the electroplating solution for electroplating again to ensure that the coating is uniform and free of micropores and microcracks;

[0055] S5. Chemically polishing the substrate IV, washing with deionized water, and drying to obtain the target copper substrate.

[0056] Example 2

[0057] S1. Immerse the copper substrate in a 0.2 mol / L dilute hydrochloric acid or sulfuric acid solution, ultrasonically treat at 20 kHz and 25°C for 3 min, wash to remove residual acid, then immerse the substrate in a 0.002 mol / L palladium chloride solution, activate it at 20°C for 2 min, wash it, and finally oxidize it to obtain substrate I;

[0058] Among them, the specific steps of oxidation treatment are:

[0059] (1) Micro-arc oxidation treatment: Prepare micro-arc oxidation equipment, including power supply, reaction tank, cathode and anode. Place the copper substrate as the anode, place the cathode in the reaction tank, and put the electrolyte in the reaction tank. Start the power supply. The power supply setting parameters are: voltage 400V, current density 60A / dm 2 , the duty cycle is 10%, the frequency is 2200Hz, the arc in the electrolyte generates local high temperature on the surface of the copper substrate, promotes the surface oxidation reaction, and forms an oxide ceramic coating;

[0060] (2) washing the copper substrate treated by micro-arc oxidation in step (1) to remove residual electrolyte on the surface, drying the copper substrate in a clean environment, heating the copper substrate to 150° C. and holding it for 20 minutes to eliminate stress within the workpiece, then heating it to 300° C. and holding it for 25 minutes to allow heat to fully penetrate into the workpiece, melt the oxide film surface, fill pores and cracks, and enhance the density of the film layer, and finally naturally cooling it to room temperature to remove oxide scale and impurities on the surface;

[0061] S2, immersing substrate I in a cobalt plating solution (cobalt sulfate 150g / L, sodium chloride 40g / L and boric acid 35g / L, thiourea 0.02g / L, benzenesulfonic acid 0.2g / L, polyethylene glycol 0.5g / L, 2-mercaptobenzothiazole 0.2g / L, sodium lauryl sulfate 0.2g / L, nonylphenol polyoxyethylene ether 0.2g / L, gelatin 0.2g / L, albumin 0.2g / L), applying a pulse current with a pulse frequency of 1000Hz and a duty cycle of 50%, stirring the plating solution slightly during the electroplating process to ensure a uniform coating, washing the substrate surface with deionized water after electroplating, and performing a heat treatment after rinsing, first heating to 130°C for 10min, then continuing to heat to 200°C for 10min, cooling, and if micropores and microcracks are present in the coating, performing a tissue refinement treatment to obtain substrate II;

[0062] S3. After cleaning and activating substrate II, immerse it in a tin plating solution (50 g / L tin chloride, 70 g / L sulfuric acid and 15 g / L citric acid, 0.02 g / L thiourea, 0.2 g / L benzenesulfonic acid, 0.5 g / L polyethylene glycol, 0.2 g / L 2-mercaptobenzothiazole, 0.2 g / L sodium lauryl sulfate, 0.2 g / L nonylphenol polyoxyethylene ether, 0.2 g / L gelatin, 0.2 g / L albumin), apply a pulse current with a pulse frequency of 500 Hz and a duty cycle of 60%. After the tin plating is completed, wash the surface of the substrate. If micropores and microcracks exist in the coating, perform a tissue refinement treatment to obtain substrate III.

[0063] S4. Treat substrate III with an alkaline detergent, wash it, and immerse it in an aluminum plating solution (180 g / L aluminum chloride, 80 g / L magnesium salt, 50 g / L dimethylformamide, 0.02 g / L thiourea, 0.2 g / L benzenesulfonic acid, 0.5 g / L polyethylene glycol, 0.2 g / L 2-mercaptobenzothiazole, 0.2 g / L sodium lauryl sulfate, 0.2 g / L nonylphenol polyoxyethylene ether, 0.2 g / L gelatin, and 0.2 g / L albumin). Apply a pulse current at a pulse frequency of 2000 Hz and a duty cycle of 40%. After the aluminum plating is completed, wash the surface of the substrate. If micropores and microcracks are present in the coating, perform a tissue refinement treatment to obtain substrate IV.

[0064] Among them, in steps S2-S4, electroplating needs to be carried out in a closed environment, using inert gas for rapid pressurization and gradual decompression. The air pressure in the sealed environment is 1-5 atmospheres. After rapid pressurization to 5 atmospheres, the substrate is deposited in the plating solution, and then gradually decompressed to 3 atmospheres to achieve a multi-layered coating structure.

[0065] If micropores and microcracks exist in the coating in steps S2-S4, a microstructure refinement treatment is performed, specifically:

[0066] (1) Immerse the plated part in a 0.8 mol / L phosphoric acid or sulfuric acid solution, connect the plated part to the anode, and use a stainless steel or lead plate as the cathode. Apply an 8 V voltage to cause an anodic reaction on the surface of the plated part to remove surface irregularities and impurities.

[0067] (2) Place the plated part in an annealing furnace with a protective atmosphere, heat to 350°C for 70 minutes, and cool to room temperature;

[0068] (3) The plated parts are chemically polished for 10 minutes, washed with deionized water, and then placed in the electroplating solution for electroplating again to ensure that the coating is uniform and free of micropores and microcracks;

[0069] S5. Chemically polishing the substrate IV, washing with deionized water, and drying to obtain the target copper substrate.

[0070] Example 3

[0071] S1. Immerse the copper substrate in a 0.5 mol / L dilute hydrochloric acid or sulfuric acid solution, ultrasonically treat at 40 kHz and 30°C for 5 min, wash to remove residual acid, then immerse the substrate in a 0.005 mol / L palladium chloride solution, activate it at 25°C for 4 min, wash it, and finally oxidize it to obtain substrate I;

[0072] Among them, the specific steps of oxidation treatment are:

[0073] (1) Micro-arc oxidation treatment: Prepare micro-arc oxidation equipment, including power supply, reaction tank, cathode and anode. Place the copper substrate as the anode, place the cathode in the reaction tank, and put the electrolyte in the reaction tank. Start the power supply. The power supply setting parameters are: voltage 600V, current density 100A / dm 2 , the duty cycle is 20%, the frequency is 3000Hz, the arc in the electrolyte generates local high temperature on the surface of the copper substrate, promotes the surface oxidation reaction, and forms an oxide ceramic coating;

[0074] (2) washing the copper substrate treated by micro-arc oxidation in step (1) to remove residual electrolyte on the surface, drying the copper substrate in a clean environment, heating the copper substrate to 200° C. and holding it for 30 minutes to eliminate stress within the workpiece, then heating it to 500° C. and holding it for 30 minutes to allow heat to fully penetrate into the workpiece, melting the oxide film surface, filling pores and cracks, and enhancing the density of the film layer, and finally cooling it naturally to room temperature to remove oxide scale and impurities on the surface;

[0075] S2, immersing substrate I in a cobalt plating solution (cobalt sulfate 200g / L, sodium chloride 50g / L and boric acid 40g / L, thiourea 0.02g / L, benzenesulfonic acid 0.2g / L, polyethylene glycol 0.5g / L, 2-mercaptobenzothiazole 0.2g / L, sodium lauryl sulfate 0.2g / L, nonylphenol polyoxyethylene ether 0.2g / L, gelatin 0.2g / L, albumin 0.2g / L), applying a pulse current with a pulse frequency of 1000Hz and a duty cycle of 50%, stirring the plating solution slightly during the electroplating process to ensure a uniform coating, washing the substrate surface with deionized water after electroplating, and performing a heat treatment after rinsing, first heating to 150°C for 10min, then continuing to heat to 200°C for 10min, cooling, and if micropores and microcracks are present in the coating, performing a tissue refinement treatment to obtain substrate II;

[0076] S3, after cleaning and activating substrate II, immersing it in a tin plating solution (60 g / L tin chloride, 100 g / L sulfuric acid and 20 g / L citric acid, 0.02 g / L thiourea, 0.2 g / L benzenesulfonic acid, 0.5 g / L polyethylene glycol, 0.2 g / L 2-mercaptobenzothiazole, 0.2 g / L sodium lauryl sulfate, 0.2 g / L nonylphenol polyoxyethylene ether, 0.2 g / L gelatin, 0.2 g / L albumin), applying a pulse current with a pulse frequency of 500 Hz and a duty cycle of 60%. After the tin plating is completed, the surface of the substrate is washed. If micropores and microcracks exist in the coating, a tissue refinement treatment is performed to obtain substrate III;

[0077] S4. Treat substrate III with an alkaline detergent, wash it, and immerse it in an aluminum plating solution (250 g / L aluminum chloride, 100 g / L magnesium salt, 60 g / L dimethylformamide, 0.02 g / L thiourea, 0.2 g / L benzenesulfonic acid, 0.5 g / L polyethylene glycol, 0.2 g / L 2-mercaptobenzothiazole, 0.2 g / L sodium lauryl sulfate, 0.2 g / L nonylphenol polyoxyethylene ether, 0.2 g / L gelatin, and 0.2 g / L albumin). Apply a pulse current at a pulse frequency of 2000 Hz and a duty cycle of 40%. After the aluminum plating is completed, wash the surface of the substrate. If micropores and microcracks are present in the coating, perform a tissue refinement treatment to obtain substrate IV.

[0078] Among them, in steps S2-S4, electroplating needs to be carried out in a closed environment, using inert gas for rapid pressurization and gradual decompression. The air pressure in the sealed environment is 1-5 atmospheres. After rapid pressurization to 5 atmospheres, the substrate is deposited in the plating solution, and then gradually decompressed to 3 atmospheres to achieve a multi-layered coating structure.

[0079] If micropores and microcracks exist in the coating in steps S2-S4, a microstructure refinement treatment is performed, specifically:

[0080] (1) Immerse the plated part in a 1.2 mol / L phosphoric acid or sulfuric acid solution, connect the plated part to the anode, and use a stainless steel or lead plate as the cathode. Apply a 12 V voltage to cause an anodic reaction on the surface of the plated part to remove surface irregularities and impurities.

[0081] (2) Place the plated part in an annealing furnace with a protective atmosphere, heat to 400°C for 120 minutes, and cool to room temperature;

[0082] (3) The plated parts are chemically polished for 10 minutes, washed with deionized water, and then placed in the electroplating solution for electroplating again to ensure that the coating is uniform and free of micropores and microcracks;

[0083] S5. Chemically polishing the substrate IV, washing with deionized water, and drying to obtain the target copper substrate.

[0084] Comparative Example 1

[0085] S1. Clean and remove pollutants and oxides on the surface of the copper substrate;

[0086] S2. Place the cleaned copper substrate into a vacuum chamber, evacuate to a base pressure of ≤1×10-5 Torr, introduce argon gas, and maintain the pressure at 0.5 Pa;

[0087] S3: Apply RF or DC bias and bombard the copper substrate surface with argon ions for 10 min, maintaining a sputtering pressure of 0.5 Pa, a sputtering power of DC 200 W, and a target current density of 10 mA / cm 2 , deposition for 2 h;

[0088] S4. After cooling naturally to room temperature, the mixture was unlocked by passing argon gas, and annealed at 300° C. for 2 h in argon gas to obtain a copper substrate.

[0089] Test example

[0090] 1. The copper substrates prepared in Examples 1-3 and Comparative Example 1 were used for 7 days and then subjected to open circuit potential (OCP) measurement:

[0091] Specific measurement method: (1) Polish the copper surface with 1200 grit sandpaper to remove the oxide layer and contaminants, ultrasonically clean it with acetone, ethanol and deionized water in sequence, blow dry it, and seal the copper sample with epoxy resin or insulating tape, exposing only the area to be measured; (2) Pour the electrolyte (100mL 0.1M NaCl) to ensure that the working electrode and the counter electrode are completely immersed, and place the reference electrode close to the working electrode surface through a salt bridge to reduce the influence of solution resistance. Connect the copper substrate, reference electrode, and counter electrode to the corresponding ports of the electrochemical workstation respectively; (3) Open the electrochemical workstation software, select "open circuit potential" or "OCP" mode, with a sampling interval of 10s and a total sampling time of 30min, until the potential stabilizes (fluctuation <1mV / min); (4) Start the measurement, monitor the potential-time curve in real time, observe the potential change until it reaches a stable value (the curve is flat), save the OCP change curve over time, and record the potential value after stabilization.

[0092] By measuring the natural potential of metal in electrolyte and observing its changes over time, the corrosion behavior of metal can be determined;

[0093] 2. Test the peel strength on a universal tensile testing machine. Before the peel strength test, make a peeling spline pattern by etching, and measure the peel strength vertically at 90°.

[0094] Specific measurement method: (1) Use photoresist or corrosion-resistant tape to cover the aluminum film, and make a parallel strip mask (width 10-25mm, length ≥100mm) by photolithography or template. Immerse the sample in aluminum etching solution (such as phosphoric acid-nitric acid mixture), etch the exposed aluminum film area until it is completely removed, exposing the copper substrate, rinse with deionized water and dry, and check under a microscope whether the edges of the etched lines are neat to ensure that the boundary between the aluminum film strip and the copper substrate is clear; (2) The upper clamp holds the free end of the aluminum film strip, and the lower clamp fixes the copper substrate to ensure that the peeling angle is always 90°. The tensile speed: according to the standard (such as ASTM D3330) set to 50-300 mm / min, 100 mm / min is usually used; (3) install the etched strip vertically, bend the aluminum film strip upward 90°, and the initial clamp spacing is 50 mm. Apply a preload of 0.1-0.5 N to eliminate slack, reset the force sensor, start the tensile machine, and continuously record the peel force-displacement curve. The peel length should be at least 50 mm (excluding the initial transient); (4) calculate the peel strength by taking the average force value of the peeling stable section (excluding the first 10% and last 10% data);

[0095] Peel strength (N / mm) = average force (N) / strip width (mm). At least 3 samples were tested in each group, the average value was taken, and the standard deviation was noted.

[0096] The results are shown in Table 1.

[0097] Table 1

[0098]

[0099] As shown in Table 1, the copper substrates prepared in Examples 1-3 of the present invention did not exhibit electrochemical corrosion after prolonged use. Peel strength, which represents the stability of the coating, was also superior to that of Comparative Example 1. This demonstrates that the copper substrates prepared in the present invention exhibit superior electrochemical corrosion resistance and excellent stability between coatings.

[0100] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0101] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for aluminum coating to prevent oxidation on the surface of a copper substrate, characterized in that: The specific steps include: S1, immersing a copper substrate in an acidic solution, ultrasonically treating, washing, then immersing the substrate in a palladium chloride solution for activation, washing, and finally oxidizing to obtain substrate I; S2, immersing substrate I in a cobalt plating solution, applying current while stirring the cobalt plating solution, washing the surface of the substrate after electroplating, and performing a microstructure refinement treatment if micropores and microcracks are present in the coating to obtain substrate II; S3, after cleaning and activating the substrate II, immersing it in a tinning solution, applying current, and washing the surface of the substrate after the tinning is completed. If micropores and microcracks exist in the coating, a microstructure refinement treatment is performed to obtain substrate III; S4. Treat substrate III with an alkaline cleaning agent, wash it, immerse it in an aluminum plating solution, apply current, and wash the surface of the substrate after the aluminum plating is completed. If micropores and microcracks exist in the coating, perform a microstructure refinement treatment to obtain substrate IV. S5. Chemically polishing the substrate IV, washing it, and drying it to obtain the target copper substrate.

2. The aluminum coating process for anti-oxidation of a copper substrate surface according to claim 1, characterized in that: In step S1, the oxidation treatment is specifically as follows: (1) Micro-arc oxidation treatment: Prepare a micro-arc oxidation device, including a power supply, a reaction tank, a cathode, and an anode. Place the copper substrate as the anode, place the cathode in the reaction tank, and put the electrolyte in the reaction tank. Start the power supply. The arc in the electrolyte generates a local high temperature on the surface of the copper substrate, promoting the surface oxidation reaction to form an oxide ceramic coating. (2) washing the copper substrate treated by micro-arc oxidation in step (1), drying, heating, and cooling.

3. The aluminum coating process for anti-oxidation of the surface of a copper substrate according to claim 2, characterized in that: In step (1), the power supply setting parameters are: voltage 200-600V, current density 20-100A / dm 2 , the duty cycle is 5%-20%, and the frequency is 50-3000Hz.

4. The aluminum coating process for anti-oxidation of a copper substrate surface according to claim 2, characterized in that: In step (2), the heating is specifically as follows: first heating to 100-200°C and maintaining for 20-30 minutes, then heating to 200-500°C and maintaining for 20-30 minutes.

5. The aluminum coating process for anti-oxidation of copper substrate surface according to claim 1, characterized in that: In steps S2-S4, the applied current is a pulse current, wherein the pulse frequency of step S2 is 1000 Hz and the duty cycle is 50%, the pulse frequency of step S3 is 500 Hz and the duty cycle is 60%, and the pulse frequency of step S4 is 2000 Hz and the duty cycle is 40%.

6. The aluminum coating process for anti-oxidation of copper substrate surface according to claim 1, characterized in that: In steps S2-S4, the electroplating is carried out in a closed environment, using inert gas for rapid pressurization and gradual decompression. The air pressure in the sealed environment is 1-5 atmospheres. After rapid pressurization to 5 atmospheres, the substrate is deposited in the plating solution, and then gradually decompressed to 3 atmospheres to achieve a multi-layered coating structure.

7. The aluminum coating process for anti-oxidation of a copper substrate surface according to claim 1, characterized in that: In steps S2-S4, after washing the substrate surface, heat treatment is required, specifically: first heating to 100-150°C and holding for 10 minutes, then continuing to heat to 200°C and holding for 10 minutes, and then cooling and performing subsequent operations.

8. The aluminum coating process for anti-oxidation of copper substrate surface according to claim 1, characterized in that: In steps S2-S4, the tissue refinement process is specifically as follows: (1) Immerse the plated part in a 0.8-1.2 mol / L phosphoric acid or sulfuric acid solution, connect the plated part to the anode, and use a stainless steel or lead plate as the cathode. Apply a voltage of 6-12 V to cause an anodic reaction on the surface of the plated part to remove surface irregularities and impurities. (2) Place the plated part in an annealing furnace with a protective atmosphere, heat to 300-400°C for 30-120 minutes, and cool to room temperature; (3) The plated parts are chemically polished for 10 minutes, washed, and placed in the electroplating solution for electroplating again to ensure that the coating is uniform and free of micropores and microcracks.

9. The aluminum coating process for anti-oxidation of copper substrate surface according to claim 1, characterized in that: In step S1, the acidic solution is dilute hydrochloric acid or sulfuric acid with a concentration of 0.2-0.5 mol / L; the ultrasonic treatment is performed at 20-40 kHz and 25-30° C. for 3-5 min; the concentration of the palladium chloride solution is 0.002-0.005 mol / L; and the activation is performed at 20-25° C. for 2-4 min. In step S2, the cobalt plating solution comprises: 100-200 g / L of cobalt sulfate, 30-50 g / L of sodium chloride, and 30-40 g / L of boric acid; In step S3, the tin plating solution includes: 40-60 g / L of tin chloride, 50-100 g / L of sulfuric acid, and 10-20 g / L of citric acid; In step S4, the aluminum plating solution includes: 150-250 g / L of aluminum chloride, 50-100 g / L of magnesium salt, and 30-60 g / L of dimethylformamide.

10. The aluminum coating process for anti-oxidation of the surface of a copper substrate according to claim 9, characterized in that: The cobalt plating solution, tin plating solution and aluminum plating solution also include 0.02 g / L of thiourea, 0.2 g / L of benzenesulfonic acid, 0.5 g / L of polyethylene glycol, 0.2 g / L of 2-mercaptobenzothiazole, 0.2 g / L of sodium lauryl sulfate, 0.2 g / L of nonylphenol polyoxyethylene ether, 0.2 g / L of gelatin and 0.2 g / L of albumin.

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