PCBA cleaning agent and preparation method thereof

Abstract

The invention relates to the technical field of cleaning agents, in particular to a PCBA cleaning agent and a preparation method thereof.The PCBA cleaning agent comprises a basic buffer solution, a carboxymethyl chitosan composite corrosion inhibitor, a cardanol surfactant modified polyethyleneimine chelating agent, an auxiliary agent and the balance ultrapure water; the carboxymethyl chitosan composite corrosion inhibitor is formed by compounding a reaction product of graphite, dopamine hydrochloride, zinc nitrate and 2-mercaptobenzimidazole with carboxymethyl chitosan. By the adoption of the PCBA cleaning agent and the preparation method thereof, welding residues, scaling powder, oil stains and heavy metal impurities can be removed, and meanwhile the PCBA cleaning agent has the functions of preventing corrosion and stabilizing the cleaning environment.

Description

Technical Field

[0001] This invention relates to the field of cleaning agent technology, and in particular to a PCBA cleaning agent and its preparation method. Background Technology

[0002] During the production of PCBA (Printed Circuit Board Assembly), flux (containing rosin and organic acids), solder paste, fingerprints, and trace amounts of heavy metal ions (such as Cu2+) can easily remain in the soldering and assembly processes. + Fe3 + If not thoroughly cleaned, residual substances can lead to poor circuit contact, corrosion of metal solder joints, or shortened device lifespan.

[0003] Traditional PCBA cleaning agents mostly rely on organic solvents (such as trichloroethylene and Freon). However, organic solvents are highly volatile, easily endangering the health of operators, difficult to biodegrade, and polluting the environment. Furthermore, organic solvents are highly corrosive to copper, tin, and other metal solder joints in PCBAs, leading to oxidation and detachment with long-term use. They also have low removal efficiency for polar fluxes (such as organic acids) and heavy metal ions, easily leaving residues that can cause subsequent malfunctions.

[0004] Therefore, there is an urgent need to develop a green, environmentally friendly, low-corrosion, and highly efficient PCBA cleaning agent. Summary of the Invention

[0005] The purpose of this invention is to provide a PCBA cleaning agent and its preparation method, which can remove soldering residue, flux, oil and heavy metal impurities, while also having the functions of corrosion prevention and stabilizing the cleaning environment.

[0006] To achieve the above objectives, the present invention provides a PCBA cleaning agent comprising, by mass percentage, 5%-10% basic buffer solution, 1%-3% carboxymethyl chitosan composite corrosion inhibitor, 0.5%-1.5% cashew nut phenol surfactant, 0.3%-0.8% modified polyethyleneimine chelating agent, 0.2%-1% auxiliary agent and the balance being ultrapure water;

[0007] The carboxymethyl chitosan composite corrosion inhibitor is composed of the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole, combined with carboxymethyl chitosan.

[0008] Preferably, the base buffer includes either Tris buffer or Hepes buffer.

[0009] Preferably, the mass ratio of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole is 1-2:1-2:0.5-1:1-2, and the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole accounts for 5%-20% of the mass of carboxymethyl chitosan.

[0010] Preferably, the cashew phenol surfactant includes one of the following: sodium cashew sulfonate, cashew phenol polyoxyethylene ether sulfate, cashew phenol ether carboxylate, cashew phenol polyoxyethylene ether ammonium chloride, cashew phenol quaternary ammonium salt, cashew phenol polyoxyethylene ether, cashew phenol polyoxypropylene ether, cashew phenol betaine, and cashew phenol sulfobetaine.

[0011] Preferably, the auxiliary agents include cystidia diamine hydrochloride, magnesium sulfate, and a pH adjuster, with cystidia diamine hydrochloride accounting for 0.1%-0.3% of the total cleaning agent and magnesium sulfate accounting for 0.05%-0.2% of the total cleaning agent.

[0012] Preferably, the pH adjuster includes one of NaOH and KOH, adjusting the pH of the cleaning agent to 7.5-9.0.

[0013] This invention also provides a method for preparing the above-mentioned PCBA cleaning agent, comprising the following steps:

[0014] S1. Preparation of carboxymethyl chitosan composite corrosion inhibitor

[0015] S1.1 Graphite was reacted with dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole at 40°C for 20-28 h to obtain the reaction product. The reaction product was then added to deionized water to prepare 8-12 mg / mL solutions. -1 A uniform slurry;

[0016] S1.2 Add carboxymethyl chitosan to deionized water to prepare a carboxymethyl chitosan solution with a concentration of 1%-5%;

[0017] S1.3. According to the proportion of reaction product to carboxymethyl chitosan mass of 5%-20%, add the homogeneous slurry of S1.1 to the carboxymethyl chitosan solution of S1.2, stir magnetically for 1-2 hours at room temperature, add crosslinking agent, react at 30-50℃ for 0.5-1 hours, and after the reaction is completed, vacuum dry to obtain carboxymethyl chitosan composite corrosion inhibitor.

[0018] S2, Preparation of modified polyethyleneimine chelating agent

[0019] S2.1 Add polyethyleneimine to deionized water and mix well to obtain a polyethyleneimine aqueous solution. Add a dual catalyst to the polyethyleneimine aqueous solution, stir and heat to 40-60℃, add sodium hydroxide aqueous solution dropwise, and continue stirring for 30-60 minutes after the addition is complete.

[0020] S2.2. Carbon disulfide gas is introduced into S2.1 and reacted at 40-60℃ for 4-6 hours. After the reaction is completed, anhydrous ethanol is added to precipitate the product, which is then centrifuged, washed, and dried at 40-50℃ to obtain polyethyleneimine dithiocarbamate, i.e., modified polyethyleneimine chelating agent.

[0021] S3. Add the basic buffer solution to ultrapure water, stir and mix evenly, then add cashew phenol surfactant and modified polyethyleneimine chelating agent prepared in S2, sonicate and disperse evenly, then add carboxymethyl chitosan composite corrosion inhibitor and auxiliary agent prepared in S1, stir and mix evenly to obtain PCBA cleaning agent.

[0022] Preferably, in step S1.1, graphite is first added to the mixed solvent and ultrasonically dispersed evenly, then dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole are added. After the reaction, the product is obtained by filtration and rinsing. The mixed solvent is a water-methanol mixture containing 10 mM Tris buffer, with a water to methanol volume ratio of 1:1.

[0023] Preferably, the crosslinking agent in S1.3 is pentylene glycol.

[0024] Preferably, the dual catalysts in S2.1 are 4-dimethylaminopyridine and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in a mass ratio of 1:3 to 1:5, and the sodium hydroxide aqueous solution is added at a dropping rate of 1-2 mL / min.

[0025] Mechanism of the invention:

[0026] In this invention, the carboxymethyl chitosan composite corrosion inhibitor suppresses the corrosion of PCBA metal substrates through a dual action. The graphite flakes form a labyrinth structure, delaying the diffusion of corrosive media such as O2 and H2O. Carboxymethyl chitosan (CMCS) has strong film-forming properties, forming a protective film on the metal surface. 2-Mercaptobenzimidazole (MBI) forms chemical bonds with the metal surface (Cu, Sn) through its thiol groups (-SH), inhibiting anodic dissolution. Zn... 2+ It binds to MBI through coordination bonds, rapidly releasing MBI in acidic corrosion microenvironments (pH 4-6), achieving rapid pH response and on-demand corrosion inhibition.

[0027] In this invention, the dithiocarbamate groups of the modified polyethyleneimine chelating agent (PEI-DTC) react with Cu2+. + Fe3 + The heavy metal ions form stable chelates, removing heavy metals from the PCBA surface and preventing them from migrating to the circuit gaps and causing short circuits.

[0028] In this invention, the basic buffer solution and pH synergistically maintain the system pH between 7.5 and 9.0, matching the stable pH range of PCBA metal substrates and suitable for various PCBA materials. Among the auxiliary agents, cystidiac diamine hydrochloride removes residual oxidants, and magnesium sulfate provides Mg2+. + Enhance the adhesion between the corrosion inhibitor and the metal.

[0029] Therefore, the present invention, employing the above-mentioned PCBA cleaning agent and its preparation method, has the following beneficial effects:

[0030] (1) It has a high efficiency in removing residual flux and can quickly remove oil stains to meet the needs of precision electronic cleaning.

[0031] (2) It has a low corrosion rate on copper and tin substrates, which facilitates the protection of solder joint integrity, and also has a low corrosion rate on Cu2+ substrates. + Fe3 + It has a high chelation rate, avoiding circuit failures caused by ion migration;

[0032] (3) The bio-based raw materials used, carboxymethyl chitosan and cashew phenol surfactant, have a high biodegradability rate and are green and environmentally friendly.

[0033] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0035] Example 1

[0036] This invention provides a PCBA cleaning agent comprising, by mass percentage: 8% Tris buffer (80mM), 2% carboxymethyl chitosan composite corrosion inhibitor, 1.0% cashew nut shell surfactant, 0.6% modified polyethyleneimine chelating agent, 0.6% auxiliary agents (0.2% cysteine ​​hydrochloride, 0.1% magnesium sulfate, 0.3% pH adjuster), and the balance being ultrapure water.

[0037] The carboxymethyl chitosan composite corrosion inhibitor is composed of the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole, combined with carboxymethyl chitosan.

[0038] The preparation method of the above-mentioned PCBA cleaning agent includes the following steps:

[0039] S1. Preparation of carboxymethyl chitosan composite corrosion inhibitor

[0040] S1.1 First, add 150 mg of graphite (5000 mesh) to 200 mL of a water-methanol mixture containing 10 mM Tris buffer (water to methanol volume ratio 1:1), and sonicate for 300 min. Then add 150 mg of dopamine hydrochloride, 75 mg of zinc nitrate, and 150 mg of 2-mercaptobenzimidazole, and stir at 40 °C for 24 h. After the reaction, filter and wash to obtain the reaction product. Add the reaction product to deionized water to obtain 10 mg / mL of the solution.-1 A uniform slurry.

[0041] S1.2 Add 3g of carboxymethyl chitosan to 100mL of deionized water to prepare a 3% carboxymethyl chitosan solution.

[0042] S1.3. According to the reaction product accounting for 10% of the mass of carboxymethyl chitosan, the homogeneous slurry of S1.1 is added to the carboxymethyl chitosan solution of S1.2, and the mixture is magnetically stirred for 1.5 h at room temperature. Then, 0.8 mg of crosslinking agent pentylene glycol is added, and the mixture is reacted at 40 °C for 0.8 h. After the reaction is completed, the mixture is vacuum dried to obtain the carboxymethyl chitosan composite corrosion inhibitor.

[0043] S2, Preparation of modified polyethyleneimine chelating agent

[0044] S2.1 Dissolve 1g of polyethyleneimine (molecular weight 10000) in 100mL of deionized water and mix well to obtain a polyethyleneimine aqueous solution. Add 0.1g of 4-dimethylaminopyridine and 0.3g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimine hydrochloride (dual catalyst ratio 1:3) to the polyethyleneimine aqueous solution, stir and heat to 50℃. While stirring, add 8mL of 10% sodium hydroxide aqueous solution at a dropping rate of 1mL / min. After the addition is complete, continue stirring for 40min.

[0045] S2.2. Carbon disulfide gas is introduced into S2.1 (flow rate is 0.5 L / h, total amount of carbon disulfide added is 0.02 mol). During the reaction, the mixture is continuously stirred and the temperature is maintained at 50℃. The reaction is carried out for 5 hours. After the reaction is completed, anhydrous ethanol is added to precipitate the product. The product is then centrifuged, washed, and dried at 45℃ for 7 hours to obtain polyethyleneimine dithiocarbamate, which is the modified polyethyleneimine chelating agent.

[0046] S3. Add 8g of Tris buffer to 88g of ultrapure water, stir and mix evenly, then add 1g of cashew phenol surfactant and 0.6g of modified polyethyleneimine chelating agent prepared in S2. After ultrasonic dispersion, add 2g of carboxymethyl chitosan composite corrosion inhibitor prepared in S1, 0.2g of cysteine ​​hydrochloride, and 0.1g of magnesium sulfate. Adjust the pH to 8.0 with NaOH and stir for 20min to obtain PCBA cleaning agent.

[0047] Example 2

[0048] This invention provides a PCBA cleaning agent comprising, by mass percentage: 5% Hepes buffer (35mM), 1% carboxymethyl chitosan composite corrosion inhibitor, 0.5% cashew phenol surfactant, 0.3% modified polyethyleneimine chelating agent, 0.2% auxiliary agents (0.1% cysteine ​​hydrochloride, 0.05% magnesium sulfate, 0.05% pH adjuster), and the balance being ultrapure water.

[0049] The carboxymethyl chitosan composite corrosion inhibitor is composed of the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole, combined with carboxymethyl chitosan.

[0050] The preparation method of the above-mentioned PCBA cleaning agent includes the following steps:

[0051] S1. Preparation of carboxymethyl chitosan composite corrosion inhibitor

[0052] S1.1 First, add 100 mg of graphite (5000 mesh) to 200 mL of a water-methanol mixture containing 10 mM Tris buffer (water to methanol volume ratio 1:1), and sonicate for 300 min. Then add 100 mg of dopamine hydrochloride, 50 mg of zinc nitrate, and 100 mg of 2-mercaptobenzimidazole, and stir at 40 °C for 20 h. After the reaction, filter and wash to obtain the reaction product. Add the reaction product to deionized water to obtain 8 mg / mL of the solution. -1 A uniform slurry.

[0053] S1.2 Add 1g of carboxymethyl chitosan to 100mL of deionized water to prepare a 1% carboxymethyl chitosan solution.

[0054] S1.3. According to the reaction product accounting for 5% of the mass of carboxymethyl chitosan, the homogeneous slurry of S1.1 is added to the carboxymethyl chitosan solution of S1.2, and the mixture is magnetically stirred for 1 hour at room temperature. Then, 0.5 mg of crosslinking agent pentylene glycol is added, and the mixture is reacted at 30°C for 0.5 hours. After the reaction is completed, the mixture is vacuum dried to obtain the carboxymethyl chitosan composite corrosion inhibitor.

[0055] S2, Preparation of modified polyethyleneimine chelating agent

[0056] S2.1 Dissolve 1g of polyethyleneimine (molecular weight 10000) in 100mL of deionized water and mix well to obtain a polyethyleneimine aqueous solution. Add 0.1g of 4-dimethylaminopyridine and 0.3g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimine hydrochloride (dual catalyst ratio 1:3) to the polyethyleneimine aqueous solution, stir and heat to 40℃. While stirring, add 8mL of 10% sodium hydroxide aqueous solution at a dropping rate of 1mL / min. After the addition is complete, continue stirring for 30min.

[0057] S2.2. Carbon disulfide gas is introduced into S2.1 (flow rate is 0.5 L / h, total amount of carbon disulfide added is 0.02 mol). During the reaction, the mixture is continuously stirred and the temperature is maintained at 40℃. The reaction is carried out for 4 hours. After the reaction is completed, anhydrous ethanol is added to precipitate the product. The product is then centrifuged, washed, and dried at 40℃ for 6 hours to obtain polyethyleneimine dithiocarbamate, which is the modified polyethyleneimine chelating agent.

[0058] S3. Add 5g of Hepes buffer to 93g of ultrapure water, stir and mix evenly, then add 0.5g of cashew phenol surfactant and 0.3g of modified polyethyleneimine chelating agent prepared in S2. After ultrasonic dispersion, add 1g of carboxymethyl chitosan composite corrosion inhibitor prepared in S1, 0.1g of cysteine ​​hydrochloride, and 0.05g of magnesium sulfate. Adjust the pH to 7.5 with NaOH and stir for 20min to obtain PCBA cleaning agent.

[0059] Example 3

[0060] This invention provides a PCBA cleaning agent comprising, by mass percentage: 10% Tris buffer (100mM), 3% carboxymethyl chitosan composite corrosion inhibitor, 1.5% cashew phenol surfactant, 0.8% modified polyethyleneimine chelating agent, 1% auxiliary agents (0.3% cysteine ​​hydrochloride, 0.2% magnesium sulfate, 0.5% pH adjuster), and the balance being ultrapure water.

[0061] The carboxymethyl chitosan composite corrosion inhibitor is composed of the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole, combined with carboxymethyl chitosan.

[0062] The preparation method of the above-mentioned PCBA cleaning agent includes the following steps:

[0063] S1. Preparation of carboxymethyl chitosan composite corrosion inhibitor

[0064] S1.1 First, add 200 mg of graphite (5000 mesh) to 200 mL of a water-methanol mixture containing 10 mM Tris buffer (water to methanol volume ratio 1:1), and sonicate for 300 min. Then add 200 mg of dopamine hydrochloride, 100 mg of zinc nitrate, and 200 mg of 2-mercaptobenzimidazole, and stir at 40 °C for 28 h. After the reaction, filter and wash to obtain the reaction product. Add the reaction product to deionized water to obtain 12 mg / mL. -1 A uniform slurry.

[0065] S1.2 Add 5g of carboxymethyl chitosan to 100mL of deionized water to prepare a 5% carboxymethyl chitosan solution.

[0066] S1.3. According to the reaction product accounting for 20% of the mass of carboxymethyl chitosan, the homogeneous slurry of S1.1 is added to the carboxymethyl chitosan solution of S1.2, and the mixture is magnetically stirred at room temperature for 2 hours. Then, 1.0 mg of crosslinking agent pentylene glycol is added, and the mixture is reacted at 50°C for 1 hour. After the reaction is completed, the mixture is vacuum dried to obtain the carboxymethyl chitosan composite corrosion inhibitor.

[0067] S2, Preparation of modified polyethyleneimine chelating agent

[0068] S2.1 Dissolve 1g of polyethyleneimine (molecular weight 10000) in 100mL of deionized water and mix well to obtain a polyethyleneimine aqueous solution. Add 0.1g of 4-dimethylaminopyridine and 0.3g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimine hydrochloride (dual catalyst ratio 1:3) to the polyethyleneimine aqueous solution, stir and heat to 60℃. While stirring, add 8mL of 10% sodium hydroxide aqueous solution at a dropping rate of 2mL / min. After the addition is complete, continue stirring for 60min.

[0069] S2.2. Carbon disulfide gas is introduced into S2.1 (flow rate is 0.5 L / h, total amount of carbon disulfide added is 0.02 mol). During the reaction, the mixture is continuously stirred and the temperature is maintained at 60℃. The reaction is carried out for 6 hours. After the reaction is completed, anhydrous ethanol is added to precipitate the product. The product is then centrifuged, washed, and dried at 50℃ for 8 hours to obtain polyethyleneimine dithiocarbamate, which is the modified polyethyleneimine chelating agent.

[0070] S3. Add 10g of Tris buffer to 84g of ultrapure water, stir and mix evenly, then add 1.5g of cashew phenol surfactant and 0.8g of modified polyethyleneimine chelating agent prepared in S2. After ultrasonic dispersion, add 3g of carboxymethyl chitosan composite corrosion inhibitor prepared in S1, 0.3g of cysteine ​​hydrochloride, and 0.2g of magnesium sulfate. Adjust the pH to 9.0 with NaOH and stir for 20min to obtain PCBA cleaning agent.

[0071] Comparative Example 1

[0072] Compared to Example 1, this one does not contain the carboxymethyl chitosan composite corrosion inhibitor, but is otherwise the same as Example 1.

[0073] Comparative Example 2

[0074] Compared to Example 1, this one does not contain the modified polyethyleneimine chelating agent; otherwise, it is the same as Example 1.

[0075] Comparative Example 3

[0076] It is a traditional trichloroethylene cleaning agent.

[0077] Performance Testing and Explanation

[0078] The various performance characteristics of the above embodiments or comparative examples were tested below, and the specific test results are shown in Table 1.

[0079] Table 1. Performance test results of the cleaning agents in Examples 1-3 and Comparative Examples 1-3

[0080]

[0081] As shown in Table 1, the removal rates of flux and oil stains in Examples 1-3 of this invention are all higher than 98%, significantly better than Comparative Example 3 (traditional trichloroethylene cleaner), demonstrating the high cleaning efficiency of the cashew phenol surfactant. Comparative Example 2, lacking a modified polyethyleneimine chelating agent, showed a significant decrease in the removal rate of polar flux (containing metal ions).

[0082] The copper and tin corrosion rates of Examples 1-3 of this invention are extremely low, while the corrosion rates of Comparative Example 1 (without corrosion inhibitor) and Comparative Example 3 are significantly increased, indicating that the carboxymethyl chitosan composite corrosion inhibitor can effectively protect metal solder joints. Example 3, with the highest corrosion inhibitor content, exhibits the best corrosion protection effect. Examples 1-3 of this invention show the best corrosion protection effect on Cu2+. + Fe3 + The chelation rate of the modified polyethyleneimine chelating agent exceeded 97%, while the control group 2 (without chelating agent) had almost no chelating ability, indicating that the modified polyethyleneimine chelating agent can efficiently capture heavy metal ions and avoid the risk of short circuits.

[0083] The biodegradability of Examples 1-3 of this invention exceeds 82%, which is an environmentally friendly formulation; the biodegradability of Comparative Example 3 (trichloroethylene) is only 12.3%, which poses a serious risk of environmental pollution.

[0084] Therefore, the present invention uses the above-mentioned PCBA cleaning agent and its preparation method to obtain a cleaning agent with advantages in terms of high efficiency in decontamination, low corrosion and environmental friendliness, which meets the technical requirements of green precision electronic cleaning.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A PCBA cleaning agent, characterized in that: It includes, by weight percentage, 5%-10% basic buffer, 1%-3% carboxymethyl chitosan composite corrosion inhibitor, 0.5%-1.5% cashew phenol surfactant, 0.3%-0.8% modified polyethyleneimine chelating agent, 0.2%-1% auxiliary agent and balance ultrapure water; The carboxymethyl chitosan composite corrosion inhibitor is composed of the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole, combined with carboxymethyl chitosan.

2. The PCBA cleaning agent according to claim 1, characterized in that: The basic buffer includes either Tris buffer or Hepes buffer.

3. The PCBA cleaning agent according to claim 1, characterized in that: The mass ratio of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole is 1-2:1-2:0.5-1:1-2, and the reaction product of graphite, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole accounts for 5%-20% of the mass of carboxymethyl chitosan.

4. The PCBA cleaning agent according to claim 1, characterized in that: Cashew phenol surfactants include one of the following: sodium cashew sulfonate, cashew phenol polyoxyethylene ether sulfate, cashew phenol ether carboxylate, cashew phenol polyoxyethylene ether ammonium chloride, cashew phenol quaternary ammonium salt, cashew phenol polyoxyethylene ether, cashew phenol polyoxypropylene ether, cashew phenol betaine, and cashew phenol sulfobetaine.

5. The PCBA cleaning agent according to claim 1, characterized in that: The auxiliary agents include cystidia diamine hydrochloride, magnesium sulfate, and pH adjusters. Cystidia diamine hydrochloride accounts for 0.1%-0.3% of the total cleaning agent, and magnesium sulfate accounts for 0.05%-0.2% of the total cleaning agent.

6. The PCBA cleaning agent according to claim 5, characterized in that: pH adjusters include one of NaOH and KOH, used to adjust the pH of the cleaning agent to 7.5-9.

0.

7. A method for preparing a PCBA cleaning agent as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Preparation of carboxymethyl chitosan composite corrosion inhibitor S1.1 Graphite was reacted with dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole at 40°C for 20-28 h to obtain the reaction product. The reaction product was then added to deionized water to prepare 8-12 mg / mL solutions. -1 A uniform slurry; S1.2 Add carboxymethyl chitosan to deionized water to prepare a carboxymethyl chitosan solution with a concentration of 1%-5%; S1.

3. According to the proportion of reaction product to carboxymethyl chitosan mass of 5%-20%, add the homogeneous slurry of S1.1 to the carboxymethyl chitosan solution of S1.2, stir magnetically for 1-2 hours at room temperature, add crosslinking agent, react at 30-50℃ for 0.5-1 hours, and after the reaction is completed, vacuum dry to obtain carboxymethyl chitosan composite corrosion inhibitor. S2, Preparation of modified polyethyleneimine chelating agent S2.1 Add polyethyleneimine to deionized water and mix well to obtain a polyethyleneimine aqueous solution. Add a dual catalyst to the polyethyleneimine aqueous solution, stir and heat to 40-60℃, add sodium hydroxide aqueous solution dropwise, and continue stirring for 30-60 minutes after the addition is complete. S2.

2. Carbon disulfide gas is introduced into S2.1 and reacted at 40-60℃ for 4-6 hours. After the reaction is completed, anhydrous ethanol is added to precipitate the product, which is then centrifuged, washed, and dried at 40-50℃ to obtain polyethyleneimine dithiocarbamate, i.e., modified polyethyleneimine chelating agent. S3. Add the basic buffer solution to ultrapure water, stir and mix evenly, then add cashew phenol surfactant and modified polyethyleneimine chelating agent prepared in S2, sonicate and disperse evenly, then add carboxymethyl chitosan composite corrosion inhibitor and auxiliary agent prepared in S1, stir and mix evenly to obtain PCBA cleaning agent.

8. The method for preparing the PCBA cleaning agent according to claim 7, characterized in that: In step S1.1, graphite is first added to a mixed solvent and ultrasonically dispersed until uniform. Then, dopamine hydrochloride, zinc nitrate, and 2-mercaptobenzimidazole are added. After the reaction, the mixture is filtered and washed to obtain the reaction product. The mixed solvent is a water-methanol mixture containing 10 mM Tris buffer, with a water to methanol volume ratio of 1:

1.

9. The method for preparing the PCBA cleaning agent according to claim 7, characterized in that: The crosslinking agent in S1.3 is pentylene glycol.

10. The method for preparing the PCBA cleaning agent according to claim 7, characterized in that: In S2.1, the dual catalysts are 4-dimethylaminopyridine and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in a mass ratio of 1:3 to 1:5, and the sodium hydroxide aqueous solution is added at a dropping rate of 1-2 mL / min.

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