Stripping solution and method for stripping tin-containing plating layer

Abstract

The invention provides a deplating solution. The deplating solution comprises the following components in percentage by weight: 10%-30% of sulfuric acid, 0.5%-1.5% of stannous mono-sulphate, 0.5%-2.5% of sodium sulfate, 0.5%-2.5% of a complexing agent, 0.1%-0.5% of an antioxidant, 1%-3% of a copper protection agent, 0.1%-0.5% of an additive and the balance of water, wherein the complexing agent is any one or two of sulfamic acid, methanesulfonic acid, phenolsulfonic acid and citric acid; the antioxidant is any one of resorcinol, hydroquinone and ascorbic acid; the copper protection agent is a core-shell structure corrosion inhibition microsphere, the core-shell structure corrosion inhibition microsphere takes hollow silicon dioxide as a core, the surface of the core-shell structure corrosion inhibition microsphere is grafted with benzotriazole, the outer layer of the core-shell structure corrosion inhibition microsphere is coated with a layer of pH sensitive type polymethylacrylic acid hydrogel shell, and the particle size is controlled to be 5-20 microns; the additive is any one of polyethylene glycol and gelatin. By optimizing the formula of the deplating solution and especially upgrading the copper protection agent system, efficient and lossless deplating of the tin-containing plating layer is achieved, meanwhile, the tin and copper recovery purity is improved, and the service life of the deplating solution is prolonged.

Description

Technical Field

[0001] This invention relates to the field of metal plating removal technology, specifically to a plating stripping solution and a method for removing tin-containing plating. Background Technology

[0002] Tin-containing plating is widely used in the electronics, hardware, and electroplating industries to improve the corrosion resistance, solderability, and decorative properties of products. However, during product manufacturing, problems such as uneven plating thickness, defects, and substandard products often occur, requiring the removal of the tin-containing plating and re-electroplating. Simultaneously, the recycling and processing of waste tin-containing plating products also necessitates efficient tin stripping processes to achieve the recycling of precious metals such as tin and copper.

[0003] Currently, existing tin stripping processes are mainly divided into two categories: chemical tin stripping and electrochemical tin stripping. Chemical tin stripping processes suffer from slow stripping speed, difficulty in separating tin from copper, short service life of stripping solution, and the generation of a large amount of tin-containing waste residue and waste liquid. It also easily corrodes the base copper, causing the base copper to lose its gloss and become damaged. Although electrochemical tin stripping processes have improved stripping efficiency, they generally suffer from low process control precision. Especially when stripping to the tin-copper alloy interface, voltage changes are difficult to capture accurately, which can easily lead to over-stripping (corroding the base copper) or incomplete stripping. In addition, the purity of tin deposited during the stripping process is low, the brightness of the copper base is poor, and subsequent resource recovery requires additional separation and purification processes, which are cumbersome and costly.

[0004] Furthermore, the existing stripping solution formulations lack sufficient synergistic effects of complexing agents, antioxidants, and copper protectants, which easily leads to poor stability of the stripping solution. After long-term use, it is prone to turbidity and failure, and the copper protection effect is limited, failing to achieve bright retention of the copper substrate. At the same time, the existing process does not consider the dynamic matching of parameters such as temperature and current density during the stripping process, further affecting the stripping effect and resource recovery efficiency.

[0005] Crucially, existing copper protection agents (such as benzotriazole BTA and methylbenzotriazole) are all molecularly dispersed, exhibiting significant technical drawbacks: First, the copper protection agent molecules adhere to the copper substrate surface through physical adsorption. Under the intense stirring and high-current impact during the stripping process, they are prone to desorption and loss, resulting in an unsustainable copper protection effect. After a long period of stripping, the copper substrate will still show corrosion and loss of gloss. Second, for copper substrate surfaces that have already developed slight pitting and roughness, traditional molecular copper protection agents can only achieve surface coverage and cannot specifically repair defective areas, resulting in insufficient surface smoothness of the copper substrate after stripping, affecting the quality of subsequent replating. Third, molecularly dispersed copper protection agents are easily carried out by the stripping solution and lost with the waste liquid, which not only reduces the utilization rate of the copper protection agent and increases production costs but also increases the burden of waste liquid treatment.

[0006] In view of the shortcomings of the existing technologies, there is an urgent need to develop a process for removing tin-containing plating layers that is highly efficient, does not damage the copper substrate, has high purity of tin-copper recovery, has good stability of the stripping solution, and has strong process controllability. In particular, it is necessary to solve the pain points of traditional copper protection agents that do not provide long-lasting protection and have weak repair capabilities, improve the practicality and economy of the process, and meet the needs of large-scale industrial production and resource recycling. Summary of the Invention

[0007] Technical problem to be solved: The purpose of this invention is to provide a tin stripping solution and a process method for removing tin-containing plating layers with the tin stripping solution. By optimizing the formulation of the stripping solution, especially upgrading the copper protection agent system, the invention achieves efficient and non-destructive removal of tin-containing plating layers, while improving the purity of tin-copper recovery and extending the service life of the stripping solution. This solves the problems of low stripping efficiency, easy corrosion of the substrate, difficulty in resource recovery, poor process controllability, and the lack of long-lasting copper protection and weak repair ability of traditional copper protection agents in the prior art.

[0008] Technical solution: A stripping solution, wherein the stripping solution comprises the following components by weight percentage: Sulfuric acid: 10~30% Stannous sulfate: 0.5~1.5% Sodium sulfate: 0.5~2.5% Complexing agent: 0.5~2.5% Antioxidant: 0.1~0.5% Copper protectant: 1-3% Additives: 0.1~0.5% The remainder is water; The complexing agent is any one or two of aminosulfonic acid, methanesulfonic acid, phenolsulfonic acid, and citric acid. The antioxidant is any one of resorcinol, hydroquinone, and ascorbic acid; The copper protection agent is a core-shell structured corrosion inhibitor microsphere. The core-shell structured corrosion inhibitor microsphere has a hollow silica core, a benzotriazole grafted on the surface, and an outer layer of pH-sensitive polymethacrylic acid hydrogel shell. The particle size is controlled at 5~20μm. The additive is either polyethylene glycol or gelatin.

[0009] Preferably, the preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water are mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen is immersed in the sol, then removed and dried, and then heat-treated to obtain the hollow microsphere core. S12. The core of the hollow microspheres above is added to water and ultrasonically dispersed for 5-8 min. Then, 3-aminopropyltriethoxysilane is added, with an amount of 5-10% of the mass of the hollow microspheres. After stirring and reacting at 50-60℃ for 1-2 h, benzotriazole is added, with an amount of 15-25% of the mass of the hollow microspheres. The reaction is continued for 2-3 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide, and ammonium persulfate to the suspension. The amount of polymethacrylic acid monomer is 20-30% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent is 1-2% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate is 0.5-1% of the mass of polymethacrylic acid monomer. Purge with nitrogen to remove air and polymerize at 60-70℃ for 1-1.5 h. A polymethacrylic acid hydrogel shell with a thickness of 0.1-0.5 μm is formed on the outer layer of the microspheres. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

[0010] Preferably, the tin stripping solution further contains 0.05-0.15% rare earth oxides and 0.03-0.08% aminotrimethylenephosphonic acid, wherein the rare earth oxides are either cerium oxide or lanthanum oxide.

[0011] A method for removing tin-containing plating involves using the aforementioned tin stripping solution to perform surface tin stripping treatment on the tin plating material.

[0012] Preferably, the tin plating material to be stripped is placed in a titanium blue, and the titanium blue containing the part to be stripped is immersed in the optimized stripping solution, ensuring that the part to be stripped is completely submerged; a rectifier is connected to the positive terminal and the negative terminal is connected to an iron plate. The current is first adjusted to be controlled by a constant current mode. When the stripping reaches the tin-copper alloy, the voltage will jump significantly; the PLC control system quickly adjusts the rectifier to the voltage stabilization mode, controlling the voltage between 2.8 and 3.2V, and finally, metallic tin is obtained on the iron plate and bright metallic copper is obtained in the titanium blue.

[0013] Preferably, the heat treatment temperature in step S11 is 500~600℃ and the time is 2~3h.

[0014] Preferably, in step S12, the amount of 3-aminopropyltriethoxysilane used is 5-10% of the mass of the hollow microspheres, and the amount of benzotriazole used is 15-25% of the mass of the hollow microspheres.

[0015] Preferably, in step S14, the amount of polymethacrylic acid monomer used is 20-30% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent used is 1-2% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate used is 0.5-1% of the mass of polymethacrylic acid monomer.

[0016] Beneficial effects: The tin stripping solution of the present invention has the following advantages: In this invention, the copper protection agent can be uniformly suspended during the stirring of the stripping solution, without settling or agglomerating. Through Brownian motion, the microspheres can continuously remain near the surface of the copper substrate, avoiding the problem of insufficient local concentration caused by the dispersion of traditional BTA molecules, thus ensuring a uniform copper protection effect. During the stripping process, when local reactions are intense (such as in high-current areas or at the tin-copper alloy interface), the temperature may rise slightly or the pH value may drop slightly. At this time, the outer pH-sensitive hydrogel shell will swell, accelerating the release of chemically bonded BTA molecules inside the shell and on the surface. This is especially true at defective areas of the copper substrate, such as pitting and rough areas. With higher activity and lower local pH, the hydrogel shell swells faster, releasing more BTA to achieve targeted repair, fill defect areas, and improve the surface smoothness of the copper substrate. BTA molecules are chemically bonded to the surface and inner wall of the microspheres, making them less prone to desorption under stirring or high current impact compared to traditional physical adsorption. At the same time, the microspheres are physical entities and are not easily carried out by the stripping solution, allowing them to remain in the stripping solution for a long time, continuously releasing BTA for a long-lasting copper protection effect. In addition, the microspheres can synergistically work with rare earth oxides to further enhance the density of the protective film and improve the copper protection effect. The rare earth oxides added in this invention can significantly improve the antioxidant properties and stability of the stripping solution, inhibit the generation of impurities in the stripping solution, and promote the uniform deposition of tin ions on the negative electrode, further improving the purity of recovered tin and reducing subsequent purification costs. In addition, rare earth oxides can also enhance the film-forming properties of copper protectants and improve the brightness and corrosion resistance of the copper substrate. This invention incorporates an organophosphonic acid-based auxiliary complexing agent—aminotrimethylenephosphonic acid—to form a synergistic complexing system with the original composite complexing agent. The main complexing agent is responsible for the basic complexing stability of tin and copper ions, while the auxiliary complexing agent can specifically chelate trace amounts of iron, lead, and other impurity ions in the stripping solution, preventing impurity ions from competing with the main complexing agent for complexing sites, thus preventing the stripping solution from becoming turbid or ineffective. At the same time, it can further improve the complexing stability of tin ions, ensuring uniform deposition of tin on the negative electrode. In addition, the organophosphonic acid-based auxiliary complexing agent can also improve the high-temperature resistance of the stripping solution, broaden the temperature adaptability range, and reduce the impact of temperature fluctuations on the stripping effect. In this invention, the conductivity of the solution is increased by adding stannous sulfate and sodium sulfate, which reduces side reactions and thus reduces energy consumption; the tin stripping rate is increased and tin oxidation is reduced by adding a complexing agent. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0018] A stripping solution comprising the following components by weight percentage: Sulfuric acid: 10%, stannous sulfate: 1.5%, sodium sulfate: 0.5%, complexing agent: 0.5%, antioxidant: 0.5%, copper protectant: 1%, additives: 0.1%, balance: water; The complexing agent is aminosulfonic acid; The antioxidant is ascorbic acid; The copper protection agent is a core-shell structured corrosion-inhibiting microsphere with a particle size controlled at 5~20μm; The additive is polyethylene glycol; Preferably, the preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water are mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen is immersed in the sol, then removed and dried. It is then subjected to heat treatment at a temperature of 500℃ for 3 hours to obtain the hollow microsphere core. S12. The core of the hollow microspheres above is added to water and ultrasonically dispersed for 8 min. Then, 3-aminopropyltriethoxysilane is added, with an amount of 5% of the mass of the hollow microspheres. After stirring and reacting at 60°C for 1 h, benzotriazole is added, with an amount of 15% of the mass of the hollow microspheres. The stirring and reaction is continued for 2 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide, and ammonium persulfate to the suspension. The amount of polymethacrylic acid monomer is 20% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent is 1% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate is 0.5% of the mass of polymethacrylic acid monomer. Purge with nitrogen to remove air and polymerize at 70°C for 1 hour. A polymethacrylic acid hydrogel shell with a thickness of 0.1~0.5μm is formed on the outer layer of the microspheres. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

[0019] Example 2

[0020] A stripping solution comprising the following components by weight percentage: Sulfuric acid: 30%, stannous sulfate: 0.5%, sodium sulfate: 2.5%, complexing agent: 2.5%, antioxidant: 0.1%, copper protectant: 3%, additives: 0.5%, balance: water; The complexing agent is methanesulfonic acid; The antioxidant is resorcinol; The copper protection agent is a core-shell structured corrosion-inhibiting microsphere with a particle size controlled at 5~20μm; The additive is gelatin; Preferably, the preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water were mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen was immersed in the sol, then removed and dried, and then subjected to heat treatment at a temperature of 600℃ for 2 hours to obtain the hollow microsphere core. S12. The core of the hollow microspheres above is added to water and ultrasonically dispersed for 5 min. Then, 3-aminopropyltriethoxysilane is added, with an amount of 10% of the mass of the hollow microspheres. After stirring and reacting at 50°C for 2 h, benzotriazole is added, with an amount of 25% of the mass of the hollow microspheres. The stirring and reaction is continued for 3 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide, and ammonium persulfate to the suspension. The amount of polymethacrylic acid monomer is 30% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent is 2% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate is 1% of the mass of polymethacrylic acid monomer. Purge with nitrogen to remove air and polymerize at 60°C for 1.5 h. A polymethacrylic acid hydrogel shell with a thickness of 0.1~0.5 μm is formed on the outer layer of the microspheres. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

[0021] Example 3

[0022] A stripping solution comprising the following components by weight percentage: Sulfuric acid: 15%, stannous sulfate: 0.8%, sodium sulfate: 2%, complexing agent: 0.5%, antioxidant: 0.5%, copper protectant: 1.5%, additives: 0.4%, cerium oxide: 0.08%, aminotrimethylenephosphonic acid: 0.07%, balance: water; The complexing agent is aminosulfonic acid and citric acid, with a mass ratio of 1:4; The antioxidant is hydroquinone; The copper protection agent is a core-shell structured corrosion-inhibiting microsphere with a particle size controlled at 5~20μm; The additive is polyethylene glycol; Preferably, the preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water were mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen was immersed in the sol, then removed and dried. The sol was then subjected to heat treatment at a temperature of 530℃ for 3 hours to obtain the hollow microsphere core. S12. The core of the hollow microspheres above was added to water and ultrasonically dispersed for 5 min. Then, 3-aminopropyltriethoxysilane was added, with an amount of 9% of the mass of the hollow microspheres. After stirring and reacting at 52℃ for 1.5 h, benzotriazole was added, with an amount of 22% of the mass of the hollow microspheres. The stirring and reaction was continued for 2.2 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide, and ammonium persulfate to the suspension. The amount of polymethacrylic acid monomer is 28% of the mass of the BTA-modified hollow microspheres, the amount of crosslinking agent is 1.6% of the mass of the polymethacrylic acid monomer, and the amount of ammonium persulfate is 0.9% of the mass of the polymethacrylic acid monomer. Purge with nitrogen to remove air and polymerize at 60°C for 1.5 h. A polymethacrylic acid hydrogel shell with a thickness of 0.1~0.5 μm is formed on the outer layer of the microspheres. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

[0023] Example 4

[0024] A stripping solution comprising the following components by weight percentage: Sulfuric acid: 25%, stannous sulfate: 1.2%, sodium sulfate: 1.5%, complexing agent: 2.5%, antioxidant: 0.1%, copper protectant: 2.5%, additives: 0.2%, cerium oxide: 0.12%, aminotrimethylenephosphonic acid: 0.04%, balance: water; The complexing agent is aminosulfonic acid and citric acid, with a mass ratio of 1:4; The antioxidant is ascorbic acid; The copper protection agent is a core-shell structured corrosion-inhibiting microsphere with a particle size controlled at 5~20μm; The additive is polyethylene glycol; Preferably, the preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water were mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen was immersed in the sol, then removed and dried. The sol was then subjected to heat treatment at a temperature of 580℃ for 2 hours to obtain the hollow microsphere core. S12. The core of the hollow microspheres above was added to water and ultrasonically dispersed for 8 min. Then, 3-aminopropyltriethoxysilane was added, with an amount of 9% of the mass of the hollow microspheres. After stirring and reacting at 58 °C for 1.2 h, benzotriazole was added, with an amount of 18% of the mass of the hollow microspheres. The stirring and reaction was continued for 2.8 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide, and ammonium persulfate to the suspension. The amount of polymethacrylic acid monomer is 22% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent is 1.2% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate is 0.6% of the mass of polymethacrylic acid monomer. Purge with nitrogen to remove air and polymerize at 70°C for 1 hour. A polymethacrylic acid hydrogel shell with a thickness of 0.1~0.5μm is formed on the outer layer of the microspheres. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

[0025] Example 5

[0026] A stripping solution comprising the following components by weight percentage: Sulfuric acid: 20%, stannous sulfate: 1%, sodium sulfate: 1.8%, complexing agent: 1.8%, antioxidant: 0.4%, copper protectant: 2%, additives: 0.3%, cerium oxide: 0.1%, aminotrimethylenephosphonic acid: 0.06%, balance: water; The complexing agent is aminosulfonic acid and citric acid, with a mass ratio of 1:4; The antioxidant is resorcinol; The copper protection agent is a core-shell structured corrosion-inhibiting microsphere with a particle size controlled at 5~20μm; The additive is polyethylene glycol; Preferably, the preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water are mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen is immersed in the sol, then removed and dried. It is then subjected to heat treatment at a temperature of 550℃ for 2 hours to obtain the hollow microsphere core. S12. The core of the hollow microspheres above was added to water and ultrasonically dispersed for 7 min. Then, 3-aminopropyltriethoxysilane was added, with an amount of 8% of the mass of the hollow microspheres. After stirring and reacting at 55°C for 1.5 h, benzotriazole was added, with an amount of 20% of the mass of the hollow microspheres. The stirring and reaction was continued for another 2.5 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide, and ammonium persulfate to the suspension. The amount of polymethacrylic acid monomer is 25% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent is 1.4% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate is 0.8% of the mass of polymethacrylic acid monomer. Purge with nitrogen to remove air and polymerize at 65°C for 1.2 seconds to form a polymethacrylic acid hydrogel shell with a thickness of 0.1~0.5μm on the outer layer of the microspheres. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

[0027] Comparative Example 1 The difference between Comparative Example 1 and Example 5 is that benzotriazole was added directly; A stripping solution comprising the following components by weight percentage: Sulfuric acid: 20%, stannous sulfate: 1%, sodium sulfate: 1.8%, complexing agent: 1.8%, antioxidant: 0.4%, copper protectant: 0.2%, additives: 0.3%, cerium oxide: 0.1%, aminotrimethylenephosphonic acid: 0.06%, balance: water; The complexing agent is aminosulfonic acid and citric acid, with a mass ratio of 1:4; The antioxidant is resorcinol; The copper protectant is benzotriazole; The additive is polyethylene glycol.

[0028] Comparative Example 2 The difference between Comparative Example 2 and Example 5 is that cerium oxide is not added.

[0029] Comparative Example 3 The difference between Comparative Example 3 and Example 5 is that aminotrimethylenephosphonic acid is not added.

[0030] Comparative Example 4 The difference between Comparative Example 4 and Example 5 is that sodium sulfate is not added.

[0031] The following performance tests were conducted on the tin stripping solutions prepared in Examples 1-5 and Comparative Examples 1-3; Tin stripping rate: The test copper sheet was dried in an oven at 105℃ and then weighed, and the mass was recorded as m1. Then, the copper sheet was soaked in the above-mentioned desoldering solution at room temperature for 20 seconds, then placed in an oven at 105℃ for 10 minutes and weighed. The mass was recorded as m2. The mass difference of the copper sheet after desoldering was calculated by subtracting m2 from m1. Then, the desoldering rate of the desoldering solution (unit: mg / min) was obtained by dividing m1 by the soaking time during desoldering.

[0032] Copper sheet surface corrosion test The copper sheet after the above test treatment was placed under a microscope and observed at 5X magnification. The corrosion was recorded after observation. Then, the gloss of the copper sheet was measured using a gloss meter. The gloss was measured at three different locations, and the average value was recorded. The specific performance is shown in Table 1 below.

[0033]

[0034] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A stripping solution, characterized in that: The stripping solution contains the following components by weight percentage composition: Sulfuric acid: 10~30% Stannous sulfate: 0.5~1.5% Sodium sulfate: 0.5~2.5% Complexing agent: 0.5~2.5% Antioxidant: 0.1~0.5% Copper protectant: 1-3% Additives: 0.1~0.5% The remainder is water; The complexing agent is any one or two of aminosulfonic acid, methanesulfonic acid, phenolsulfonic acid, and citric acid. The antioxidant is any one of resorcinol, hydroquinone, and ascorbic acid; The copper protection agent is a core-shell structured corrosion inhibitor microsphere. The core-shell structured corrosion inhibitor microsphere has a hollow silica core, a benzotriazole grafted on the surface, and an outer layer of pH-sensitive polymethacrylic acid hydrogel shell. The particle size is controlled at 5~20μm. The additive is either polyethylene glycol or gelatin.

2. The desoldering solution according to claim 1, characterized in that, The preparation method of the core-shell structured corrosion-inhibiting microspheres includes the following steps: S11. Tetraethyl orthosilicate, hydrochloric acid, anhydrous ethanol and water are mixed in a molar ratio of 1:1:80:4 to obtain a sol. Pollen is immersed in the sol, then removed and dried, and then heat-treated to obtain the hollow microsphere core. S12. The core of the hollow microspheres above is added to water and ultrasonically dispersed for 5-8 min. Then, 3-aminopropyltriethoxysilane is added and stirred at 50-60℃ for 1-2 h. After stirring, benzotriazole is added and the reaction is continued for 2-3 h to obtain BTA-modified hollow microspheres. S13. Add BTA-modified hollow microspheres to deionized water and ultrasonically disperse them to form a suspension. Add polymethacrylic acid monomer, N,N-methylenebisacrylamide and ammonium persulfate to the suspension. Purge with nitrogen to remove air and polymerize at 60-70℃ for 1-1.5h. A polymethacrylic acid hydrogel shell with a thickness of 0.1-0.5μm is formed on the outer layer of the microspheres. After the reaction is complete, centrifuge, wash and vacuum dry to obtain core-shell structured corrosion-inhibiting microspheres.

3. The desoldering solution according to claim 1, characterized in that: The tin stripping solution also contains 0.05-0.15% rare earth oxides and 0.03-0.08% aminotrimethylenephosphonic acid, wherein the rare earth oxides are either cerium oxide or lanthanum oxide.

4. A method for removing a tin-containing plating layer, characterized in that: The tin plating material is subjected to surface tin stripping treatment using the tin stripping solution according to any one of claims 1-3.

5. The method for removing tin-containing plating according to claim 4, characterized in that: The tin plating material to be stripped is placed in a titanium blue, and the titanium blue containing the part to be stripped is immersed in the optimized stripping solution, ensuring that the part to be stripped is completely submerged. A rectifier is connected to the positive terminal and the negative terminal is connected to an iron plate. The current is first adjusted to be controlled by a constant current mode. When the stripping reaches the tin-copper alloy, the voltage will jump significantly. The PLC control system quickly adjusts the rectifier to the voltage stabilization mode, controlling the voltage between 2.8 and 3.2V. Finally, metallic tin is obtained on the iron plate and bright metallic copper is obtained in the titanium blue.

6. The desoldering solution according to claim 2, characterized in that: The heat treatment in step S11 is performed at a temperature of 500~600℃ for 2~3 hours.

7. The desoldering solution according to claim 2, characterized in that: In step S12, the amount of 3-aminopropyltriethoxysilane used is 5-10% of the mass of the hollow microspheres, and the amount of benzotriazole used is 15-25% of the mass of the hollow microspheres.

8. The desoldering solution according to claim 2, characterized in that: In step S14, the amount of polymethacrylic acid monomer used is 20-30% of the mass of BTA-modified hollow microspheres, the amount of crosslinking agent used is 1-2% of the mass of polymethacrylic acid monomer, and the amount of ammonium persulfate used is 0.5-1% of the mass of polymethacrylic acid monomer.

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