Soldering paste easy to clean and preparation method thereof

Abstract

The invention relates to a divisional application with the application number of 2023103071686, belongs to the technical field of tin soldering materials, and provides easy-to-clean soldering paste and a preparation method thereof.The easy-to-clean soldering paste is composed of a solder, a soldering flux, an auxiliary and a solvent, the soldering flux uses a washing film-forming agent to replace traditional rosin, so that the soldering flux has good hydrophilicity, and in the welding process, the soldering flux is not prone to falling off, and the soldering flux is not prone to falling off. The bonding force between the welding slag and the substrate is reduced, clean water can be used for washing after welding is completed, the risk that the substrate is corroded by a cleaning solvent is reduced, VOC is not generated in the washing process, human health and environmental protection are facilitated, and the beneficial effects of being low in residue, good in washing effect, low in implementation cost and convenient to popularize and implement are achieved.

Description

[0001] This application is a divisional application. The application number of the original application is 2023103071686, the application date is March 27, 2023, and the name of the invention is "Environmentally friendly, low-residue, easy-to-clean solder paste and its preparation method." Technical Field

[0002] The invention belongs to the technical field of soldering materials, and in particular relates to an easy-to-clean solder paste and a preparation method thereof. Background Art

[0003] Solder paste is a new type of welding material that came into being with SMT. It is a paste-like mixture formed by solder powder, flux, etc. It is mainly used for welding electronic components such as resistors, capacitors, ICs, etc. on the surface of PCBs in the SMT industry. The flux commonly used in traditional solder paste is rosin or modified rosin. During the welding process, there is flux residue on the solder joint or near it, which may cause the morphology of the welding area to deteriorate and damage the contact effect of the pins of the electronic parts welded by the solder paste. Moreover, the resistivity decreases after the residue absorbs moisture in the air, thereby increasing the risk of short circuit of electronic components. The existing solder paste is generally washed with an organic solvent after welding, which takes a long time and has the risk of corroding the substrate. VOC is generated during the washing process, which is not conducive to human health and environmental protection. Now there is an urgent need for an easy-to-clean solder paste. Summary of the invention

[0004] In order to solve the technical problems of high residual content, difficulty in cleaning, and generation of VOC harmful to human body in the cleaning process of the existing solder paste, the present invention provides an easy-to-clean solder paste; The second object of the present invention is to provide a method for preparing an easy-to-clean solder paste.

[0005] In order to achieve the first purpose, this application adopts the following scheme: An easy-to-clean solder paste, comprising the following components by weight: 78-85 parts of solder, 12-19 parts of flux, 1-2 parts of auxiliary agent, and 3-5 parts of solvent; The solder is composed of the following components by mass fraction: 90.89-92.78wt% tin, 5.51-7.01wt% copper, and 1.65-2.11wt% silver; Preferably, the method for preparing the solder comprises the following steps: S401. Weigh the components of the solder according to the mass fraction and melt them to obtain liquid solder; S402. Pour the liquid solder obtained in step S401 into a mold and cool it to room temperature to obtain a solder brick; S403. After the solder brick obtained in step 402 is crushed by rolling, it is ball-milled in combination with a high-pressure homogenizer to a particle size of 18-41 μm.

[0006] Preferably, the auxiliary agent is composed of the following components by weight: 0.5-1 part of a stabilizer and 0.5-1 part of a dispersant, and the stabilizer is p-phenol.

[0007] Preferably, the solvent is a 2:1:1 mixture of ethanol, ethyl acetate and butyl acetate.

[0008] Preferably, the soldering flux is composed of the following components by weight: 6-8 parts of a water-washable film-forming agent, 2-4 parts of an activator, 1-2 parts of a thixotropic agent, 0.5-1 parts of an etchant slowing agent, and 0.5-1 parts of a wetting agent.

[0009] Preferably, the thixotropic agent is a 1:1:1 mixture of glyceryl tri-12-hydroxystearate, polyamide and stearamide, the etching slowing agent is benzotriazole, and the wetting agent is OP-10.

[0010] Preferably, the water-washable film-forming agent is composed of the following components by weight: 2-3 parts of modified wheat starch, 4-5 parts of modified acrylic resin, 1-2 parts of surfactant, and 2-3 parts of deionized water. More preferably, the surfactant is sodium dodecylbenzene sulfonate.

[0011] Preferably, the preparation method of the modified wheat starch comprises the following steps: Step 101. Put the crude wheat starch into a starch centrifuge and centrifuge at 1000-1300 rpm for 30-40 min, filter and dry to obtain refined starch; Step 102. The refined starch obtained in step 101 is put into a magnetic stirring kettle containing glycerol, and titanate coupling agent and anhydrous ethanol are added dropwise in sequence. After stirring at 200-300 rpm for 5-10 min, the mixture is stirred at 500-1200 rpm for 0.5-2.5 h to obtain modified wheat starch. The mass ratio of the glycerol to the refined starch is 1-2:1, and the anhydrous ethanol is used to adjust the viscosity of the system and ensure the stirring rate.

[0012] In actual use, the starch centrifuge can centrifuge the protein and B-type starch in the crude wheat starch to the bottom. After centrifugation, the film-forming ability and hydrophilicity of the modified starch can be improved. The refined starch is combined with a titanate coupling agent and anhydrous ethanol and put into glycerin to improve the hydrophilicity and film-forming property of the modified starch system. On the one hand, it is convenient to cover the solder joint position during the soldering process to prevent solder joint oxidation. On the other hand, after the welding is completed, the adsorption capacity of the modified starch and the substrate is weak. The modified wheat starch has a strong hydrophilicity and is easy to peel off after encountering water or anhydrous ethanol. The flux uses a water-washable film-forming agent instead of traditional rosin, so that the flux has good hydrophilicity. During the welding process, the adhesion between the welding slag and the substrate is reduced. After the welding is completed, clean water can be used for washing to reduce the risk of corrosion of the substrate by the cleaning solvent. No VOC is generated during the washing process, which is beneficial to human health and environmental protection. It has the advantages of low residue, good water washing effect, low implementation cost, and easy promotion and implementation.

[0013] Preferably, the preparation of the modified acrylic resin comprises the following steps: acrylic resin, castor oil alkyd resin, polyurethane resin and anhydrous ethanol are sequentially put into a stirring kettle, stirred at 300-500rpm for 5-10min, and after the stirring is completed, DMAEMA is dropped into the kettle and stirred at 800-900rpm for 20-40min to obtain the modified acrylic resin; more preferably, the mass ratio of the acrylic resin, polyurethane resin, anhydrous ethanol and DMAEMA is 6-9:1:2:0.5.

[0014] During actual use, on the one hand, castor oil alkyd resin, polyurethane modified resin and DMAEMA are used to modify acrylic resin, and a large number of hydroxyl groups and carboxyl groups are introduced into acrylic resin to improve the hydrophilicity of modified acrylic resin itself. On the other hand, a large number of amino flexible groups are introduced to make the solder paste have a good expansion rate in the soldering process, which is convenient for electronic printing, saves solder in the solder paste, and can prevent solder joint oxidation during the soldering process. The flux uses a water-washable film-forming agent instead of traditional rosin, so that the flux has good hydrophilicity. During the welding process, the adhesion between the welding slag and the substrate is reduced. After the welding is completed, it can be washed with clean water to reduce the risk of corrosion of the substrate by the cleaning solvent. No VOC is generated during the washing process, which is beneficial to human health and environmental protection. It has the advantages of low residue, good water washing effect, low implementation cost and easy promotion and implementation.

[0015] Preferably, the method for preparing the water-washable film-forming agent comprises the following steps: adding modified acrylic resin, surfactant, modified wheat starch and deionized water into a stirring kettle in sequence, stirring for 20-40 minutes at 500-700 rpm in a constant temperature water bath at 30-40°C, and cooling to room temperature after stirring.

[0016] Preferably, the activator is composed of the following components by weight: 5-7 parts of anhydrous citric acid, 2-4 parts of malic acid, 0.1-0.8 parts of triethanolamine, and 7-11 parts of acrylic resin.

[0017] Preferably, the preparation method of the activator comprises the following steps: Step 201. Anhydrous citric acid, malic acid and triethanolamine are sequentially placed in a stirring kettle, and stirred at 300-520 rpm in a water bath at 30-50° C. for 0.5-1.2 h to obtain an active substance body; Step 202. Adding acrylic resin to the active material obtained in step 1, stirring at 90-120° C. and 600-1200 rpm for 4-5 hours to obtain an active coating; Step 203. The active coating obtained in step 202 is dried and solidified at 25-30° C. and 200-400 rpm. After solidification, the active coating is ball-milled to 100-360 μm using a ball mill to obtain an activator.

[0018] In actual use, citric acid and DL-malic acid have a small wetting angle with the substrate, strong wetting ability, and poor corrosion ability to the substrate under low temperature conditions, which prevents the solder paste from corroding the substrate before soldering. During welding, it has a good effect on removing oxides from the substrate and improves the expansibility of the solder. After being coated with acrylic resin, on the one hand, it can prevent citric acid and DL-malic acid from volatilizing and oxidizing. On the other hand, it can further protect the substrate under low temperature conditions to prevent the activator from corroding the substrate. By using a water-washable film-forming agent instead of traditional rosin in the flux, the flux has good hydrophilicity. During the welding process, the bonding force between the welding slag and the substrate is reduced. After welding is completed, it can be washed with clean water to reduce the risk of corrosion of the substrate by the cleaning solvent. No VOC is generated during the washing process, which is beneficial to human health and environmental protection. It has the advantages of low residue, good water washing effect, low implementation cost, and easy promotion and implementation.

[0019] In order to achieve the second purpose, this application adopts the following technical solution: A method for preparing an easy-to-clean solder paste comprises the following steps: S301. The water-washed film-forming agent, activator, thixotropic agent, slow etching agent and wetting agent are sequentially placed in a stirring kettle and stirred at 40-50°C and 300-420rpm for 20-30min to obtain a soldering flux; S302. Put the solder, flux, additive and solvent into a vacuum stirring kettle in sequence and stir for 3-7 hours at 25-35°C and 400-620rpm to obtain an easy-to-clean solder paste.

[0020] Preferably, nitrogen needs to be introduced during the stirring process in step S302, and the vacuum degree of the vacuum stirring kettle is 0.03-0.04 MPa.

[0021] Compared with the prior art, this application has the following beneficial effects: 1. The present application provides an easy-to-clean solder paste, which is composed of solder, flux, additives, and solvents. The flux uses a water-washable film-forming agent instead of traditional rosin, so that the flux has good hydrophilicity. During the welding process, the adhesion between the welding slag and the substrate is reduced. After the welding is completed, it can be washed with clean water to reduce the risk of corrosion of the substrate by the cleaning solvent. No VOC is generated during the washing process, which is beneficial to human health and environmental protection. It has the advantages of low residue, good water washing effect, low implementation cost, and easy promotion and implementation.

[0022] 2. The present application provides a method for preparing an easy-to-clean solder paste, by stirring solder, flux, additives and solvents in a vacuum environment to prepare an easy-to-clean solder paste, which has the advantages of a wide range of applications, little environmental pollution, simple operation, strong reproducibility and low implementation cost. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with Table 1, Table 2, specific examples 1-3 and comparative example 1: (1) The preparation method of solder comprises the following steps: S401. Weigh the components of the solder according to the mass fraction and melt them to obtain liquid solder; S402. Pour the liquid solder obtained in step S101 into a mold and cool it to room temperature to obtain a solder brick; S403. After the solder brick obtained in step 102 is crushed by rolling, it is ball-milled to a particle size of 40 μm using a ball mill in combination with a high-pressure homogenizer.

[0024] Example 1 The preparation method of modified wheat comprises the following steps: S101. The crude wheat starch was put into a starch centrifuge and centrifuged at 1105 rpm for 32 min to obtain refined starch; S102. The refined starch obtained in S101 was put into a magnetic stirring kettle containing glycerol, and titanate coupling agent and anhydrous ethanol were added dropwise in sequence. After stirring at 257 rpm for 6 min, the mixture was stirred at 980 rpm for 0.7 h to obtain modified wheat starch.

[0025] The preparation method of the modified acrylic resin comprises the following steps: Acrylic resin, castor oil alkyd resin, polyurethane resin and anhydrous ethanol were put into a stirring kettle in a mass ratio of 6.5:1:2:0.5, and stirred at 375 rpm for 6 minutes. After stirring, DMAEMA was dropped into the mixture and stirred at 818 rpm for 22 minutes to obtain modified acrylic resin.

[0026] According to the weight parts shown in Table 2, the preparation method of the water-washable film-forming agent includes the following steps: Put the modified acrylic resin, surfactant, modified wheat starch and deionized water into a stirring kettle in sequence, stir for 20-40 minutes in a constant temperature water bath at 30-40°C and 500-700rpm, and cool to room temperature after stirring.

[0027] According to the weight parts shown in Table 3, the preparation method of the activator comprises the following steps: S201. Anhydrous citric acid, malic acid and triethanolamine were sequentially placed in a stirred tank and stirred at 33 ° C in a water bath at 312 rpm for 1.1 h to obtain an active substance body; S202. Add acrylic resin to the active material obtained in S1, and stir at 93°C and 630 rpm for 4.1 h to obtain an active coating; S203. The active coating obtained in S202 is dried and cured at 27°C and 240 rpm. After curing, the active coating is ball-milled to 108 μm using a ball mill to obtain an activator.

[0028] According to the weight parts shown in Table 4, the preparation method of easy-to-clean solder paste includes the following steps: S301. The water-washable film-forming agent, activator, thixotropic agent, slow etching agent, and wetting agent are sequentially placed in a stirring kettle and stirred at 42°C and 319 rpm for 22 minutes to obtain a soldering flux; S302. Put solder, flux, additive and solvent into a vacuum stirring kettle in sequence at 28°C and 450rpm, introduce nitrogen, and stir for 3.6 hours under the condition that the vacuum degree of the vacuum stirring kettle is 0.0318MPa to obtain an easy-to-clean solder paste.

[0029] Example 2 The preparation method of modified wheat comprises the following steps: S101. The crude wheat starch was put into a starch centrifuge and centrifuged at 1244 rpm for 35 min to obtain refined starch; S102. The refined starch obtained in S101 was put into a magnetic stirring kettle containing glycerol, and titanate coupling agent and anhydrous ethanol were added dropwise in sequence. After stirring at 257 rpm for 6 min, the mixture was stirred at 620 rpm for 1.1 h to obtain modified wheat starch.

[0030] The preparation method of the modified acrylic resin comprises the following steps: Acrylic resin, castor oil alkyd resin, polyurethane resin and anhydrous ethanol were put into a stirring kettle in a mass ratio of 7.2:1:2:0.5, and stirred at 390 rpm for 7 minutes. After stirring, DMAEMA was dropped into the mixture and stirred at 842 rpm for 27 minutes to obtain modified acrylic resin.

[0031] According to the weight parts shown in Table 2, the preparation method of the water-washable film-forming agent includes the following steps: The modified acrylic resin, surfactant, modified wheat starch and deionized water were sequentially placed in a stirring kettle, stirred at 35°C constant temperature water bath and 610 rpm for 29 minutes, and then cooled to room temperature to obtain the product.

[0032] According to the weight parts shown in Table 3, the preparation method of the activator comprises the following steps: S201. Anhydrous citric acid, malic acid and triethanolamine were sequentially placed in a stirred tank and stirred at 377 rpm in a water bath at 42 ° C for 0.8 h to obtain the active substance body; S202. Add acrylic resin to the active material obtained in S1, and stir at 109°C and 811rpm for 4.5h to obtain an active coating; S203. The active coating obtained in S202 is dried and cured at 28°C and 333 rpm. After curing, the active coating is ball-milled to 147 μm using a ball mill to obtain an activator.

[0033] According to the weight parts shown in Table 4, the preparation method of easy-to-clean solder paste includes the following steps: S301. The water-washable film-forming agent, activator, thixotropic agent, slow etching agent, and wetting agent are sequentially placed in a stirring kettle and stirred at 46°C and 365 rpm for 25 min to obtain a soldering flux; S302. Put solder, flux, additive and solvent into a vacuum stirring kettle in sequence at 28°C and 425rpm, introduce nitrogen, and stir for 4.2 hours under the condition that the vacuum degree of the vacuum stirring kettle is 0.0323MPa to obtain an easy-to-clean solder paste.

[0034] Example 3 The preparation method of modified wheat comprises the following steps: S101. The crude wheat starch was put into a starch centrifuge and centrifuged at 1288 rpm for 36 min to obtain refined starch; S102. The refined starch obtained in S101 was put into a magnetic stirring kettle containing glycerol, and titanate coupling agent and anhydrous ethanol were added dropwise in sequence. After stirring at 291 rpm for 9 minutes, the mixture was stirred at 1155 rpm for 2.3 hours to obtain modified wheat starch.

[0035] The preparation method of the modified acrylic resin comprises the following steps: Acrylic resin, castor oil alkyd resin, polyurethane resin and anhydrous ethanol were sequentially put into a stirring kettle at a mass ratio of 8.2:1:2:0.5, and stirred at 465 rpm for 7 min. After stirring, DMAEMA was dropped into the mixture and stirred at 842 rpm for 37 min to obtain modified acrylic resin.

[0036] According to the weight parts shown in Table 2, the preparation method of the water-washable film-forming agent includes the following steps: The modified acrylic resin, surfactant, modified wheat starch and deionized water were sequentially placed in a stirring kettle, stirred at 37°C constant temperature water bath and 633 rpm for 35 min, and then cooled to room temperature.

[0037] According to the weight parts shown in Table 3, the preparation method of the activator comprises the following steps: S201. Anhydrous citric acid, malic acid, and triethanolamine were sequentially placed in a stirred tank, and stirred at 46 ° C in a water bath at 517 rpm for 1.1 h to obtain an active substance body; S202. Add acrylic resin to the active material obtained in S1, and stir at 115°C and 1125rpm for 4.6h to obtain an active coating; S203. The active coating obtained in S202 is dried and cured at 28°C and 369rpm. After curing, the active coating is ball-milled to 337μm using a ball mill to obtain an activator.

[0038] According to the weight parts shown in Table 4, the preparation method of easy-to-clean solder paste includes the following steps: S301. The water-washable film-forming agent, activator, thixotropic agent, slow etching agent, and wetting agent are sequentially placed in a stirring kettle and stirred at 46°C and 411 rpm for 25 minutes to obtain a soldering flux; S302. Put solder, flux, additive and solvent into a vacuum stirring kettle in sequence at 33°C, 605rpm, introduce nitrogen, and stir for 5.2 hours under the condition that the vacuum degree of the vacuum stirring kettle is 0.0351MPa to obtain an easy-to-clean solder paste.

[0039] Comparative Example 1 The water-washable film-forming agent in the solder resist in Example 3 was replaced with an equal weight portion of rosin, and the other components remained unchanged.

[0040] Comparative Example 2 The water-washable film-forming agent in the solder resist in Example 3 is replaced by an equal weight portion of rosin, the activator is replaced by an equal weight portion of succinic acid after removing the acrylic resin, and the other components remain unchanged.

[0041] Table 1 Solder mass fraction composition of Examples 1-3 and Comparative Examples 1-2

[0042] Table 2 Composition of the water-washable film-forming agent in Examples 1-3 and Comparative Examples 1-2 by weight

[0043] Table 3 Composition of activators by weight in Examples 1-3 and Comparative Examples 1-2

[0044] Table 4 Composition of solder paste by weight in Examples 1-3 and Comparative Examples 1-2

[0045] Examples 1-3 and Comparative Examples 1-2 were tested according to IPC-TM-650 2.6.3.7:2007, IPC J-STD-004B, IPC-TM-650 2.4.34.3:1995, IPC-TM-650 2.4.45:1995, JIS-Z-31976.6.1, IPC-TM-6502.3.32D:2004, IPC-TM-650 2.4.46A:2004, IEC 62149-2-21, IPC-TM-650 2.3.13:2004 standard was used to perform solder paste performance tests and clean water and ethanol cleaning simulation experiments. The same mass of solder pastes of Examples 1-3 and Comparative Examples 1-2 were used to perform welding on solder discs of the same batch number at the same welding temperature for equal time. After welding, the test solder discs were respectively placed in ultrasonic vibration cleaning tanks filled with clean water or ethanol for vibration cleaning. After cleaning until no film-forming substances were visually observed on the surface of the test solder discs, the cleaning time was recorded. The test results are shown in Table 5 below.

[0046] Table 5 Test results of Examples 1-3 and Comparative Examples 1-2

[0047] As shown in Table 5, in actual use, the starch centrifuge can centrifuge the protein and B-type starch in the crude wheat starch to the bottom, and the film-forming ability and hydrophilicity of the modified starch can be improved after centrifugation. The refined starch is combined with a titanate coupling agent and anhydrous ethanol and put into glycerol to improve the hydrophilicity and film-forming property of the modified starch system. On the one hand, it is convenient to cover the solder joint position during the soldering process to prevent solder joint oxidation. On the other hand, after the welding is completed, the adsorption capacity of the modified starch and the substrate is weak. The modified wheat starch has a strong hydrophilicity and is easy to peel off after encountering water or anhydrous ethanol. The flux uses a water-washable film-forming agent instead of traditional rosin, so that the flux has good hydrophilicity. During the welding process, the bonding force between the welding slag and the substrate is reduced. After the welding is completed, clean water can be used for washing to reduce the risk of corrosion of the substrate by the cleaning solvent. No VOC is generated during the washing process, which is beneficial to human health and environmental protection. It has the advantages of low residue, good water washing effect, low implementation cost, and easy promotion and implementation.

[0048] During actual use, on the one hand, castor oil alkyd resin, polyurethane modified resin and DMAEMA are used to modify acrylic resin, and a large number of hydroxyl groups and carboxyl groups are introduced into acrylic resin to improve the hydrophilicity of modified acrylic resin itself. On the other hand, a large number of amino flexible groups are introduced to make the solder paste have a good expansion rate in the soldering process, which is convenient for electronic printing, saves solder in the solder paste, and can prevent solder joint oxidation during the soldering process. The flux uses a water-washable film-forming agent instead of traditional rosin, so that the flux has good hydrophilicity. During the welding process, the adhesion between the welding slag and the substrate is reduced. After the welding is completed, it can be washed with clean water to reduce the risk of corrosion of the substrate by the cleaning solvent. No VOC is generated during the washing process, which is beneficial to human health and environmental protection. It has the advantages of low residue, good water washing effect, low implementation cost and easy promotion and implementation.

[0049] From the results of copper plate corrosion test and copper mirror corrosion test, we can see that citric acid and malic acid as activators can remove oxides on the surface of solder joints. Under the wrapping of acrylic resin, it is not easy to corrode the solder plate at low temperature. Compared with succinic acid, it has a stronger protective effect on the circuit. From the results of water / ethanol simulation cleaning test, we can see that after the water-washable film-forming agent replaces rosin, the water cleanliness of the film-forming material is significantly improved, the residue is small, it is easy to clean, and the cleaning time is significantly reduced.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An easy-to-clean solder paste, characterized in that: The composition is composed of the following components by weight: 78-85 parts of solder, 12-19 parts of flux, 1-2 parts of auxiliary agent, and 3-5 parts of solvent; The soldering flux is composed of the following components by weight: 6-8 parts of a water-washable film-forming agent, 2-4 parts of an activator, 1-2 parts of a thixotropic agent, 0.5-1 parts of an etching slowing agent, and 0.5-1 parts of a wetting agent; The water-washable film-forming agent is composed of the following components by weight: 2-3 parts of modified wheat starch, 4-5 parts of modified acrylic resin, 1-2 parts of surfactant, and 2-3 parts of deionized water; The particle size of the solder is 18-41 μm; The preparation method of the modified wheat starch comprises the following steps: S101. The crude wheat starch is put into a starch centrifuge and centrifuged at 1000-1300 rpm for 30-40 min to obtain refined starch; S102. The refined starch obtained in S101 was put into a magnetic stirring reactor containing glycerol, and titanate coupling agent and anhydrous ethanol were added dropwise in sequence. After stirring at 200-300 rpm for 5-10 min, the mixture was stirred at 500-1200 rpm for 0.5-2.5 h to obtain modified wheat starch. The preparation method of the activator comprises the following steps: S201. Anhydrous citric acid, malic acid and triethanolamine were sequentially placed in a stirred tank and stirred at 30-50 ° C in a water bath at 300-520 rpm for 0.5-1.2 h to obtain the active substance body; S202. Adding acrylic resin to the active material obtained in S1, stirring at 90-120°C and 600-1200rpm for 4-5h to obtain an active coating; S203. The active coating obtained in S202 is dried and cured at 25-30°C and 200-400rpm. After curing, it is ball-milled to 100-360μm using a ball mill to obtain an activator.

2. The easy-to-clean solder paste according to claim 1, characterized in that: The solder consists of the following components by mass fraction: 90.89-92.78wt% of tin, 5.51-7.01wt% of copper, and 1.65-2.11wt% of silver.

3. The easy-to-clean solder paste according to claim 1, characterized in that: The preparation of the modified acrylic resin comprises the following steps: Put acrylic resin, castor oil alkyd resin, polyurethane resin and anhydrous ethanol into a stirring kettle in sequence, stir at 300-500rpm for 5-10min, and after stirring, drop DMAEMA into the mixture and stir at 800-900rpm for 20-40min to obtain modified acrylic resin.

4. The easy-to-clean solder paste according to claim 3, characterized in that: The mass ratio of the acrylic resin, the polyurethane resin, the anhydrous ethanol and the DMAEMA is 6-9:1:2:0.

5.

5. The easy-to-clean solder paste according to claim 1, characterized in that: The preparation method of the water-washable film-forming agent comprises the following steps: adding modified acrylic resin, surfactant, modified wheat starch and deionized water into a stirring kettle in sequence, stirring for 20-40 minutes in a constant temperature water bath at 30-40° C. and 500-700 rpm, and cooling to room temperature after stirring.

6. The easy-to-clean solder paste according to claim 1, characterized in that: The activator is composed of the following components by weight: 5-7 parts of anhydrous citric acid, 2-4 parts of DL-malic acid, 0.1-0.8 parts of triethanolamine, and 7-11 parts of acrylic resin.

7. The easy-to-clean solder paste according to claim 2, characterized in that: The preparation method of the solder comprises the following steps: S401. Weigh the components of the solder according to the mass fraction and melt them to obtain liquid solder; S402. Pour the liquid solder obtained in step S401 into a mold and cool it to room temperature to obtain a solder brick; S403. After the solder brick obtained in step 402 is crushed by rolling, it is ball-milled in combination with a high-pressure homogenizer to a particle size of 18-41 μm.

8. The easy-to-clean solder paste according to claim 1, characterized in that: The thixotropic agent is a 1:1:1 mixture of glyceryl tri-12-hydroxystearate, polyamide and stearamide, the etching slowing agent is benzotriazole, and the wetting agent is OP-10.

9. The method for preparing an easy-to-clean solder paste according to any one of claims 1 to 8, characterized in that: The following steps are involved: S301. The water-washed film-forming agent, activator, thixotropic agent, slow etching agent and wetting agent are sequentially placed in a stirring kettle and stirred at 40-50°C and 300-420rpm for 20-30min to obtain a soldering flux; S302. Put the solder, flux, additive and solvent into a vacuum stirring kettle in sequence and stir at 25-35°C and 400-620rpm for 3-7h to obtain an easy-to-clean solder paste.

10. The method for preparing the easy-to-clean solder paste according to claim 9, characterized in that: Nitrogen needs to be introduced during the stirring process in S302, and the vacuum degree of the vacuum stirring kettle is 0.03-0.04 MPa.

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