Copper-tin alloy electroplating solution, preparation method thereof and preparation method of solar cell metal electrode

Abstract

The invention provides a copper-tin alloy electroplating solution, a preparation method thereof and a preparation method of a solar cell metal electrode, and particularly relates to the technical field of solar cell preparation. The copper-tin alloy electroplating solution provided by the invention comprises copper salt, tin salt, a complexing agent, an antioxidant, a surfactant and water. Wherein the complexing agent and the copper salt act and are combined with the surfactant to reduce the charge density of an electrode interface, increase cathode polarization and reduce the equilibrium potential difference between copper and tin, so that the reduction and deposition efficiency of metal ions in the electroplating process is improved, the porosity, roughness and defects of a plating layer are reduced, and the plating layer is more uniform and compact. The structure of the antioxidant serving as the plating layer can also prevent the plating layer from being oxidized, and the service life of the copper-tin alloy is prolonged. According to the electroplating liquid, codeposition of copper and tin can be achieved, the working procedure is simplified, therefore, wastewater discharge in the production process is reduced, the manufacturing cost is reduced, and the electroplating liquid is more competitive in industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell preparation, in particular to a copper-tin alloy electroplating solution and a preparation method thereof, and a preparation method of a solar cell metal electrode. Background Art

[0002] Electroplating solar cells uses electroplating to deposit a metal layer on the surface of solar cells to enhance their conductivity and protective properties. Typically, the electrodes utilize a nickel-copper-tin structure, consisting of multiple layers of metal, each with a specific function. The nickel layer acts as a barrier, preventing direct contact between other metals and the solar cell's silicon substrate, thereby protecting it from corrosion. The copper layer, acting as a conductive layer, contributes to improved cell efficiency due to its excellent electrical conductivity. The tin layer acts as a protective layer, covering the copper layer to prevent oxidation and extend the battery's lifespan.

[0003] However, existing electroplated solar cells lack corrosion and heat resistance. These performance deficiencies can lead to degradation in harsh environmental conditions or even failure during long-term use, impacting the overall performance and lifespan of the solar cell. Furthermore, traditional electroplating methods require a step-by-step process, which not only increases the complexity of the production process but also reduces production efficiency. Each layer of metal requires specific conditions and time, which undoubtedly increases production costs and time.

[0004] To complicate matters, the plating solution used in the electroplating process needs to be cleaned after plating is complete, generating significant amounts of wastewater. This wastewater contains heavy metals and other hazardous chemicals, which, if not properly treated, can cause significant environmental pollution. Consequently, existing electroplating methods not only increase production costs but also place a burden on the environment.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a copper-nickel alloy electroplating solution with improved performance, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0007] A second object of the present invention is to provide a method for preparing a copper-nickel alloy electroplating solution.

[0008] A third object of the present invention is to provide a metal electrode for a solar cell.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0010] A first aspect of the present invention provides a copper-tin alloy electroplating solution comprising a copper salt, a tin salt, a complexing agent, an antioxidant, a surfactant and water.

[0011] Furthermore, in parts by weight, each unit volume of the copper-tin alloy electroplating solution includes 100-200 parts of copper salt, 10-40 parts of tin salt, 5-30 parts of complexing agent, 0.5-2 parts of antioxidant, 0.2-1 parts of surfactant, and the balance is water.

[0012] Furthermore, the copper salt includes at least one of copper sulfate, copper chloride, copper acetate and copper methanesulfonate.

[0013] Preferably, the tin salt includes at least one of stannous sulfate, stannous chloride and stannous methanesulfonate.

[0014] Preferably, the complexing agent comprises at least one of citric acid, gluconic acid, aminoacetic acid, tartaric acid and phenylalanine.

[0015] Furthermore, the antioxidant includes at least one of phenol, phenolsulfonic acid, cresolsulfonic acid, resorcinol, hydroquinone and catechol.

[0016] Preferably, the surfactant includes at least one of polyethylene glycol, polypropylene glycol, octylphenol polyglycol ether and polyethylene glycol formal.

[0017] Preferably, the water comprises pure water.

[0018] A second aspect of the present invention provides a method for preparing the copper-tin alloy electroplating solution, comprising the following steps:

[0019] A. Add copper salt and complexing agent into water to react and obtain complexed copper salt;

[0020] B. dissolving the complexed copper salt in water, adding tin salt, surfactant and antioxidant and mixing evenly to obtain the copper-tin alloy electroplating solution.

[0021] Furthermore, in step A, the reaction temperature is 40-50° C. and the reaction time is 15-45 min.

[0022] Preferably, the pH of the copper-tin alloy electroplating solution is 2.0-4.0.

[0023] A third aspect of the present invention provides a method for preparing a metal electrode for a solar cell, wherein a double-sided nickel-plated silicon substrate for a solar cell is placed in a copper-tin alloy electroplating solution for direct current electroplating to obtain a metal electrode for the solar cell;

[0024] Wherein, the copper-tin alloy electroplating solution is the copper-tin alloy electroplating solution described in the first aspect.

[0025] Furthermore, the solar cell is an N-type TOPCon cell.

[0026] Preferably, the solar cell metal electrode includes a nickel layer and a copper-nickel alloy layer disposed on the nickel layer.

[0027] Preferably, the nickel layer has a thickness of 0.5 to 1.0 μm.

[0028] Furthermore, the copper-nickel alloy layer has a thickness of 8 to 10 μm.

[0029] Furthermore, the temperature of the direct current electroplating is 30-50° C., and the time is 6-12 minutes.

[0030] Preferably, the current density of the DC electroplating is 4 to 8 A / dm 2 .

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] In the copper-tin alloy electroplating solution provided by the present invention, the complexing agent acts on the copper salt and combines with the surfactant to reduce the charge density of the electrode interface, increase the cathode polarization, and reduce the equilibrium potential difference between copper and tin, thereby helping to improve the reduction and deposition efficiency of metal ions in the electroplating process, reduce the porosity, roughness and defects of the coating, and make the coating more uniform and dense. The antioxidant as the structure of the coating can also prevent the oxidation of the coating and increase the life of the copper-tin alloy. The electroplating solution of the present invention can achieve the co-deposition of copper and tin, simplifying the process that needs to be carried out step by step in the traditional electroplating process, thereby reducing the discharge of wastewater in the production process. This simplification not only improves production efficiency, but also reduces manufacturing costs, making the electroplating solution of the present invention more competitive in industrial production.

[0033] The preparation method provided by the present invention first complexes the copper salt, thereby improving the stability of the copper salt and reducing the equilibrium potential difference between the copper salt and the tin salt, laying the foundation for the formation of a uniform copper-tin alloy layer. The preparation method of the present invention is simple in process, reduces production costs, and is suitable for industrial large-scale production.

[0034] The method for preparing metal electrodes for solar cells provided by the present invention, in view of the advantages of the above-mentioned copper-tin alloy electroplating solution, simplifies the preparation steps of the metal electrodes, reduces wastewater discharge during the production process, improves production efficiency and reduces preparation costs, so that the prepared solar cells have better market competitiveness. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0037] A first aspect of the present invention provides a copper-tin alloy electroplating solution comprising a copper salt, a tin salt, a complexing agent, an antioxidant, a surfactant and water.

[0038] In the copper-tin alloy electroplating solution provided by the present invention, the complexing agent acts on the copper salt and combines with the surfactant to reduce the charge density of the electrode interface, increase the cathode polarization, and reduce the equilibrium potential difference between copper and tin, thereby helping to improve the reduction and deposition efficiency of metal ions in the electroplating process, reduce the porosity, roughness and defects of the coating, and make the coating more uniform and dense. The antioxidant as the structure of the coating can also prevent the oxidation of the coating and increase the life of the copper-tin alloy. The electroplating solution of the present invention can achieve the co-deposition of copper and tin, simplifying the process that needs to be carried out step by step in the traditional electroplating process, thereby reducing the discharge of wastewater in the production process. This simplification not only improves production efficiency, but also reduces manufacturing costs, making the electroplating solution of the present invention more competitive in industrial production.

[0039] Specifically, the complexing agent in the copper-tin alloy electroplating solution of the present invention reacts with the copper salt to form a complex reaction. This process not only enhances the stability of the electroplating solution, but also lays the foundation for the subsequent electroplating process. At the same time, the addition of the surfactant significantly improves the cathode polarization, and the synergistic effect with the complexing agent effectively reduces the equilibrium potential difference between copper and tin. The reduction of this potential difference is the key to achieving copper-tin co-deposition, which enables the two metals to be more evenly deposited on the substrate during the electroplating process, thereby obtaining a dense and uniform coating. This dense and uniform coating not only significantly enhances the bonding strength with the substrate, but also is not easily oxidized and discolored in the air, maintaining the lasting stability of the appearance. When faced with a weak acid or weak base environment, the coating exhibits strong corrosion resistance, which greatly expands its scope of application, especially in situations where special requirements are placed on corrosion resistance.

[0040] In addition, the coating also has good heat resistance, allowing it to maintain its performance even in high-temperature environments. These characteristics make copper-tin alloy electroplating solutions have broad application prospects in industries such as electronics, automobiles, and aviation.

[0041] Because the components of the electroplating solution are nonvolatile and highly stable, material waste and environmental issues caused by component volatilization can be reduced during actual production. Furthermore, because the electroplating solution of the present invention can achieve co-deposition of copper and tin, it simplifies the traditional electroplating process, which requires separate steps, thereby reducing wastewater discharge during the production process. This simplification not only improves production efficiency but also reduces manufacturing costs, making the electroplating solution of the present invention more competitive in industrial production.

[0042] Furthermore, in parts by weight, each unit volume of the copper-tin alloy electroplating solution includes 100-200 parts of copper salt, 10-40 parts of tin salt, 5-30 parts of complexing agent, 0.5-2 parts of antioxidant, 0.2-1 parts of surfactant, and the balance is water.

[0043] Typically but not limiting, in terms of weight parts, per unit volume of the copper-tin alloy electroplating solution, the amount of the copper salt can be, for example, 100 parts, 120 parts, 140 parts, 160 parts, 180 parts or 200 parts, or any value within the range of 100 to 200 parts; the amount of the tin salt can be, for example, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts, or any value within the range of 10 to 40 parts; the complexing agent can be, for example, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts, or any value within the range of 10 to 40 parts; The amount of the agent can be, for example, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, or 30 parts, or any value within the range of 5 parts to 30 parts; the amount of the antioxidant can be, for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, or any value within the range of 0.5 parts to 2 parts; the amount of the surfactant can be, for example, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, or 1 part, or any value within the range of 0.2 parts to 1 part. The remainder is made up of water to the required total volume of the electroplating solution.

[0044] Furthermore, the copper salt includes at least one of copper sulfate, copper chloride, copper acetate and copper methanesulfonate.

[0045] Preferably, the tin salt includes at least one of stannous sulfate, stannous chloride and stannous methanesulfonate.

[0046] Preferably, the complexing agent comprises at least one of citric acid, gluconic acid, aminoacetic acid, tartaric acid and phenylalanine.

[0047] Furthermore, the antioxidant includes at least one of phenol, phenolsulfonic acid, cresolsulfonic acid resorcinol, hydroquinone and catechol.

[0048] Preferably, the surfactant includes at least one of polyethylene glycol, polypropylene glycol, octylphenol polyglycol ether and polyethylene glycol formal.

[0049] Preferably, the water comprises pure water.

[0050] A second aspect of the present invention provides a method for preparing the copper-tin alloy electroplating solution, comprising the following steps:

[0051] A. Add copper salt and complexing agent into water to react and obtain complexed copper salt;

[0052] B. dissolving the complexed copper salt in water, adding tin salt, surfactant and antioxidant and mixing evenly to obtain the copper-tin alloy electroplating solution.

[0053] The preparation method provided by the present invention first complexes the copper salt, thereby improving the stability of the copper salt and reducing the equilibrium potential difference between the copper salt and the tin salt, laying the foundation for the formation of a uniform copper-tin alloy layer. The preparation method of the present invention is simple in process, reduces production costs, and is suitable for industrial large-scale production.

[0054] Specifically, step A achieves the complexation of copper salt by adding copper salt and complexing agent to water for reaction. This step is crucial because it not only provides the necessary chemical basis for the subsequent electroplating process, but also improves the solubility and stability of copper salt through complexation reaction, laying a solid foundation for forming a uniform copper-tin alloy coating. Subsequently, in step B, the complexed copper salt is dissolved in water, and tin salt, surfactant and antioxidant are added and mixed to obtain the final copper-tin alloy electroplating solution. The mixing process in this step ensures the uniform distribution between the components, provides a guarantee for the stability of the electroplating solution and the uniform deposition during the electroplating process. The addition of surfactant, as mentioned above, helps to improve cathode polarization and improve the quality of the coating, while the presence of antioxidant effectively prevents oxidation of the coating and prolongs the service life of the metal electrode.

[0055] The copper-tin alloy electroplating solution produced by this preparation method exhibits good stability, uniform coating formation, excellent corrosion and heat resistance, and excellent electrical conductivity. Furthermore, this method simplifies the preparation process for the electroplating solution, reduces production costs, and minimizes environmental impact, contributing to the sustainable development of electroplating technology.

[0056] Furthermore, in step A, the reaction temperature is 40-50° C. and the reaction time is 15-45 min.

[0057] In the complexation reaction, the complexing agent, which includes at least one of citric acid, gluconic acid, aminoacetic acid, tartaric acid, and phenylalanine, binds to the copper ions in the copper salt through coordination bonds to form a stable copper complex. This reduces the free concentration of copper ions in the electroplating solution and prevents subsequent differences in plating performance caused by different copper-tin deposition rates. Because the copper ions form a stable complex with the complexing agent, the solubility of copper is improved, which helps maintain a stable copper ion concentration during the electroplating process, ensuring the uniformity of the electroplating solution and the quality of the electroplated layer. The formation of the copper complex reduces the hydrolysis of copper ions, thereby improving the chemical stability of the electroplating solution and extending the service life of the electroplating solution.

[0058] Typically, but not limiting, the temperature setting during the reaction process can be 40°C, 42°C, 44°C, 46°C, 48°C or 50°C, or any temperature value within the range of 40°C to 50°C; the reaction duration can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min or 45 min, or any time value within the range of 15 min to 45 min.

[0059] Preferably, the pH of the copper-tin alloy electroplating solution is 2.0-4.0.

[0060] Controlling the pH value of the copper-tin alloy electroplating solution within the range of 2.0 to 4.0 can ensure the stability of copper and tin salts in the electroplating solution, prevent them from undergoing unnecessary chemical reactions or precipitation, and thus maintain the long-term stability and service life of the electroplating solution. At the same time, this pH range is conducive to promoting the uniform deposition of copper-tin alloy, because under this pH condition, the reduction potential and deposition rate of the metal ions can be well matched, reducing the risk of uneven coating or defects. At the same time, a moderately acidic environment helps to improve the bonding strength between the coating and the substrate, because the acidic conditions can slightly etch the surface of the nickel layer, increase the surface roughness, and thus enhance the adhesion of the coating.

[0061] Typically but not limiting, the pH value of the copper-tin alloy electroplating solution can be precisely set to 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8 or 4.0, or any pH value within the range of 2.0 to 4.0.

[0062] A third aspect of the present invention provides a method for preparing a metal electrode for a solar cell, wherein a double-sided nickel-plated silicon substrate for a solar cell is placed in a copper-tin alloy electroplating solution for direct current electroplating to obtain a metal electrode for the solar cell;

[0063] Wherein, the copper-tin alloy electroplating solution is the copper-tin alloy electroplating solution described in the first aspect.

[0064] The method for preparing metal electrodes for solar cells provided by the present invention, in view of the advantages of the above-mentioned copper-tin alloy electroplating solution, simplifies the preparation steps of the metal electrodes, reduces wastewater discharge during the production process, improves production efficiency and reduces preparation costs, so that the prepared solar cells have better market competitiveness.

[0065] Furthermore, the solar cell is an N-type TOPCon cell.

[0066] Preferably, the solar cell metal electrode includes a nickel layer and a copper-nickel alloy layer disposed on the nickel layer.

[0067] Preferably, the nickel layer has a thickness of 0.5 to 1.0 μm.

[0068] The thickness of the nickel layer is controlled within the range of 0.5-1 micron. This nickel layer acts as an effective barrier, preventing direct contact between the silicon substrate and the copper-nickel alloy layer, thereby protecting the battery from corrosion and chemical attack and enhancing its stability. At the same time, the moderate thickness of the nickel layer ensures good electrical conductivity, facilitating efficient current transmission and improving the battery's conversion efficiency.

[0069] Typically but not limiting, the thickness of the nickel layer may be precisely 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm, or any value within the range of 0.5 μm to 1.0 μm.

[0070] Furthermore, the copper-nickel alloy layer has a thickness of 8 to 10 μm.

[0071] The thickness of the copper-nickel alloy layer is controlled within the range of 8 to 10 microns, which not only provides good electrical conductivity and ensures efficient current transmission, but also increases the mechanical strength and wear resistance of the electrode, thereby improving the durability and reliability of the battery. In addition, this thickness range of the copper-nickel alloy layer also helps to improve production efficiency because the electroplating process can be completed in a shorter time and the uniformity of the plating layer is easy to achieve, reducing production costs and meeting the needs of industrial large-scale production.

[0072] Typically but not limiting, the thickness of the copper-nickel alloy layer may be 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, or any value within the range of 8 μm to 10 μm.

[0073] Furthermore, the temperature of the direct current electroplating is 30-50° C., and the time is 6-12 minutes.

[0074] Controlling the electroplating temperature between 30°C and 50°C and setting the plating time between 6 and 12 minutes can comprehensively optimize both plating results and production efficiency. This temperature range accelerates electrochemical reactions and increases the reduction rate of metal ions at the electrode, thereby speeding up deposition, shortening production cycles, and improving production efficiency. Furthermore, a moderate temperature helps reduce thermal stress and deformation that may occur during the electroplating process, maintaining uniformity and adhesion of the coating.

[0075] This temperature range also helps reduce the decomposition of functional substances in the electrolyte, maintaining the stability of the plating solution and extending its service life. A shorter plating time combined with a moderate temperature can reduce the porosity and roughness of the coating, improve the density and smoothness of the coating, and thus produce a higher-quality copper-nickel alloy layer. This high-quality coating not only improves the conductivity of the solar cell but also enhances its corrosion and wear resistance, thereby extending the battery's service life.

[0076] Typically, but not limiting, the temperature during the DC electroplating process can be set to 30° C., 35° C., 40° C., 45° C., or 50° C., or any value within the range of 30° C. to 50° C. The electroplating time can be set to 6 min, 7 min, 8 min, 9 min, 10 min, or 12 min, or any value within the range of 6 min to 12 min.

[0077] Preferably, the current density of the DC electroplating is 4 to 8 A / dm 2 .

[0078] The current density is controlled at 4~8A / dm 2 Within this range, the efficiency of the electroplating process and the superiority of the coating quality can be ensured. This current density range helps to achieve a faster deposition rate, thereby shortening the production cycle and improving production efficiency. At the same time, 4 to 8 A / dm 2 The current density can promote the uniform reduction of metal ions on the electrode, reduce the porosity and roughness of the coating, and improve the density and smoothness of the coating.

[0079] Typically, but not limiting, the current density during the DC electroplating process may be 4A / dm 2 , 4.5A / dm 2 , 5A / dm 2 , 5.5A / dm 2 , 6A / dm 2 , 6.5A / dm 2 , 7A / dm 2 or 8A / dm 2 , or 4A / dm 2 Up to 8A / dm 2 Any value in the range.

[0080] The present invention is further illustrated below by specific examples and comparative examples. However, it should be understood that these examples are merely for the purpose of further explanation and should not be construed as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, unless otherwise specified, were prepared under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0081] Example 1

[0082] This embodiment provides a copper-tin alloy electroplating solution, which contains 150 g / L of cupric chloride, 25 g / L of stannous chloride, 20 g / L of citric acid, 1 g / L of phenol, 0.3 g / L of octylphenol polyglycol ether, 0.3 g / L of polyethylene glycol, and the rest is pure water.

[0083] The preparation method of the above-mentioned copper-tin alloy electroplating solution is as follows:

[0084] 1. Add 150g of copper chloride and 20g of citric acid to an appropriate amount of water and mix well. React at 40℃ for 30min. After the reaction is completed, evaporate the water to obtain the complexed copper chloride.

[0085] 2. Add the complexed copper chloride to 800 mL of pure water, dissolve the stannous chloride, continue to add phenol, octylphenol polyglycol ether and polyethylene glycol and stir evenly, detect the pH in the range of 2.0 to 4.0, and dilute the above solution to 1 L with pure water to obtain the copper-tin alloy electroplating solution.

[0086] Example 2

[0087] This embodiment provides a copper-tin alloy electroplating solution, which contains 120 g / L of copper sulfate, 20 g / L of stannous sulfate, 10 g / L of tartaric acid, 2 g / L of hydroquinone, 0.3 g / L of octylphenol polyglycol ether, 0.3 g / L of polyethylene glycol, and the rest is pure water.

[0088] The preparation method of the copper-tin alloy electroplating solution is the same as that of Example 1.

[0089] Example 3

[0090] This embodiment provides a copper-tin alloy electroplating solution, wherein copper acetate is 180 g / L, stannous methanesulfonate is 35 g / L, phenylalanine is 8 g / L, cresol sulfonic acid resorcinol is 1 g / L, octylphenol polyglycol ether is 0.6 g / L, and the remainder is pure water.

[0091] The preparation method of the copper-tin alloy electroplating solution is the same as that of Example 1.

[0092] Example 4

[0093] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the cupric chloride is 100 g / L and the stannous chloride is 10 g / L. The remaining raw materials are the same as those in Example 1 and are not repeated here.

[0094] The preparation method of the copper-tin alloy electroplating solution is the same as that of Example 1.

[0095] Example 5

[0096] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the cupric chloride is 200 g / L and the stannous chloride is 40 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0097] The preparation method of the copper-tin alloy electroplating solution is the same as that of Example 1.

[0098] Example 6

[0099] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the amount of citric acid is 30 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0100] The preparation method of the copper-tin alloy electroplating solution is the same as that of Example 1.

[0101] Example 7

[0102] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the amount of citric acid is 5 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0103] The preparation method of the copper-tin alloy electroplating solution is the same as that of Example 1.

[0104] Example 8

[0105] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the amount of phenol is 0.5 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0106] Example 9

[0107] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the amount of phenol is 2 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0108] Example 10

[0109] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the content of octylphenol polyglycol ether is 0.1 g / L and the content of polyethylene glycol is 0.1 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0110] Example 11

[0111] This embodiment provides a copper-tin alloy electroplating solution. The difference from Example 1 is that the content of octylphenol polyglycol ether is 0.5 g / L and the content of polyethylene glycol is 0.5 g / L. The remaining raw materials are the same as those in Example 1 and are not described again here.

[0112] Comparative Example 1

[0113] This comparative example provides a copper-tin alloy electroplating solution. The difference from Example 1 is that citric acid is omitted. The remaining raw materials and steps are the same as those in Example 1. The preparation method accordingly omits step 1 and directly prepares the electroplating solution in pure water without treating the copper chloride.

[0114] Comparative Example 2

[0115] This comparative example provides a copper-tin alloy electroplating solution. The difference from Example 1 is that phenol is eliminated. The remaining raw materials and preparation methods are the same as those in Example 1 and are not described again here.

[0116] Comparative Example 3

[0117] This comparative example provides a copper-tin alloy electroplating solution. The difference from Example 1 is that octylphenol polyglycol ether and polyethylene glycol are eliminated. The remaining raw materials and preparation methods are the same as those in Example 1 and are not described again here.

[0118] Test Example 1

[0119] The copper-tin alloy electroplating solutions obtained in the examples and comparative examples were placed in a constant temperature water bath at 75° C. and heated for 1 hour. The changes were observed and recorded in Table 1.

[0120] It should be noted that the stability of the copper-tin alloy electroplating solution is determined by observing whether the plating solution changes during the reaction process. A stable copper-tin alloy electroplating solution maintains its clarity and transparency throughout the electroplating process.

[0121] If the plating solution remains clear in the plating tank and there is no metal deposit at the bottom, it indicates that the plating solution has good stability. On the contrary, if metal deposits are found at the bottom of the plating tank, it means that the plating solution is unstable.

[0122] Test Example 2

[0123] The double-sided nickel-plated solar cell silicon substrate was immersed in the copper-tin alloy electroplating solution obtained in the embodiment and the comparative example, and the temperature was controlled at 40°C for DC electroplating for 9 minutes. The DC electroplating current density was 6A / dm 2 , a copper-tin alloy layer is obtained, and the height of the fine grid lines on the front of the solar cell is measured using a 3D microscope according to the nine-square grid method, and the average value is taken.

[0124] Table 1

[0125]

[0126]

[0127] As can be seen from Table 1, the copper ions and the complexing agent form a stable complex, which improves the solubility of copper and ensures the uniformity of the electroplating solution. At the same time, the hydrolysis of the copper ions is reduced, and the presence of the antioxidant prevents the oxidation of the tin ions, thereby improving the chemical stability of the electroplating solution and extending the service life of the copper-tin alloy electroplating solution.

[0128] Test Example 3

[0129] The solar cell with the copper-tin alloy layer obtained in Test Example 2 was subjected to a coating adhesion test. The main grid and PAD points of the copper-tin alloy grid lines on the front and back of the crystalline silicon solar cell were covered with low-temperature solder tape, assisted by a small amount of flux, and soldered at 180°C. The welding tension at 12 PAD points was tested with a tensile gauge, and the average value was taken (all points ≥0.8N were qualified). The obtained data were recorded in Table 2.

[0130] Table 2

[0131]

[0132]

[0133] As can be seen from Table 2, the use of chelating agents and antioxidants helps to improve the quality of copper-tin alloy plating. If the additives of the copper-tin alloy electroplating solution are not properly matched, the copper-tin alloy will not be co-deposited, and only copper will be deposited on the surface of the solar cell. It will be easily oxidized in the air, resulting in poor corrosion resistance of the battery and reduced welding tensile strength.

[0134] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A copper-tin alloy electroplating solution, characterized in that It includes copper salt, tin salt, complexing agent, antioxidant, surfactant and water.

2. The copper-tin alloy electroplating solution according to claim 1, characterized in that Calculated by weight, each unit volume of the copper-tin alloy electroplating solution includes 100-200 parts of copper salt, 10-40 parts of tin salt, 5-30 parts of complexing agent, 0.5-2 parts of antioxidant, 0.2-1 parts of surfactant, and the balance is water.

3. The copper-tin alloy electroplating solution according to claim 1 or 2, characterized in that The copper salt includes at least one of copper sulfate, copper chloride, copper acetate and copper methanesulfonate; Preferably, the tin salt comprises at least one of stannous sulfate, stannous chloride and stannous methanesulfonate; Preferably, the complexing agent comprises at least one of citric acid, gluconic acid, aminoacetic acid, tartaric acid and phenylalanine.

4. The copper-tin alloy electroplating solution according to claim 1 or 2, characterized in that The antioxidant comprises at least one of phenol, phenolsulfonic acid, cresolsulfonic acid resorcinol, hydroquinone and catechol; Preferably, the surfactant comprises at least one of polyethylene glycol, polypropylene glycol, octylphenol polyglycol ether and polyethylene glycol formal; Preferably, the water comprises pure water.

5. A method for preparing the copper-tin alloy electroplating solution according to any one of claims 1 to 4, characterized in that: The following steps are involved: A. Add copper salt and complexing agent into water to react and obtain complexed copper salt; B. dissolving the complexed copper salt in water, adding tin salt, surfactant and antioxidant and mixing evenly to obtain the copper-tin alloy electroplating solution.

6. The preparation method according to claim 5, characterized in that In step A, the reaction temperature is 40-50°C and the reaction time is 15-45 minutes; Preferably, the pH of the copper-tin alloy electroplating solution is 2.0-4.

0.

7. A method for preparing a metal electrode for a solar cell, characterized in that: The solar cell silicon substrate with double-sided nickel plating is placed in a copper-tin alloy electroplating solution for direct current electroplating to obtain a solar cell metal electrode; Wherein, the copper-tin alloy electroplating solution is the copper-tin alloy electroplating solution according to any one of claims 1 to 4.

8. The preparation method according to claim 7, characterized in that The solar cell is an N-type TOPCon cell; Preferably, the solar cell metal electrode comprises a nickel layer and a copper-nickel alloy layer disposed on the nickel layer; Preferably, the thickness of the nickel layer is 0.5-1.0 μm.

9. The preparation method according to claim 8, characterized in that The thickness of the copper-nickel alloy layer is 8-10 μm.

10. The preparation method according to claim 7, characterized in that The temperature of the direct current electroplating is 30-50°C and the time is 6-12 minutes; Preferably, the current density of the DC electroplating is 4 to 8 A / dm 2 .

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