Water-based circuit board or circuit board protective coating liquid and preparation method thereof

Abstract

The invention discloses a water-based circuit board or circuit board protective coating liquid which comprises the following components in parts by weight: 15-25 parts of (methyl) acrylic acid modified polyethylene resin; the molar equivalence ratio of the addition amount of the alkali to the content of the (methyl) acrylic acid in the (methyl) acrylic acid modified polyethylene resin is (85-120): 100; the aqueous dispersion of the modified polyethylene resin is prepared from the (methyl) acrylic acid modified polyethylene resin and the alkali, and the aqueous dispersion of the modified polyethylene resin and the polycarbodiimide curing agent are uniformly mixed according to the mass ratio of (100: 2)-(100: 8) to obtain the water-based circuit board or circuit board protective coating liquid. The invention also discloses a preparation method of the composition. The protective coating liquid prepared by the invention is applied to an integrated circuit board or a circuit board as a surface protective coating, has excellent low temperature resistance (less than-60 DEG C) flexibility, acid resistance, alkali resistance, oil resistance, salt mist resistance, insulation and the like, and provides long-term stable protection for the integrated circuit board or the circuit board.

Description

Technical Field

[0001] The invention belongs to the field of circuit board or circuit board protection, and specifically relates to an aqueous circuit board or circuit board protective coating liquid and a preparation method thereof. Background Art

[0002] Electronic assembly circuit boards or circuit boards are widely used in various fields such as transportation, electrical appliances, military industry, automobiles, machinery, precision instruments, etc. The use environment varies greatly. Some will be used in harsh environments for a long time, such as mountains and underwater; there are also many chemical environments, such as coolants, grease, acid / alkaline gases or liquids; mechanical vibration, dust, high temperature, humidity, salt spray and other environments will affect the circuit boards or circuit boards, causing corrosion or deformation, and unable to work and use normally. The common method is to apply a layer of protective coating (commonly known as three-proof paint) on the surface of the circuit board or circuit board to prevent external environmental factors from damaging the circuit board or circuit board, and improve the service life and performance stability.

[0003] There are many types of protective coatings in the early days, mainly alkyd resins, polyester resins, acrylate resins, polyurethane resins and silicone resins. Most of these resins are dissolved in easily volatile solvents (such as toluene, xylene, n-hexane, ethyl acetate, isopropanol, etc.), sprayed or brushed on the surface of the circuit board or circuit board, and dried at room temperature or heated to form a dense layer of protective film. Such a product system requires the use of a high content of solvent, causing a large amount of volatile organic compounds (VOCs) to evaporate into the air, causing damage to the environment, especially during the construction of circuit boards and circuit boards, most of which need to be in a dust-free workshop, which is often a closed positive pressure environment, which will also cause great health damage to operators.

[0004] Driven by environmental protection, many technologies based on solvent-free circuit board or circuit board protective coatings have been developed. Among them, solvent-free UV curable systems and water-based resin systems have received a lot of attention and technical innovation as two major technical routes. The solvent-free UV system has high requirements for equipment and needs to avoid the impact of ultraviolet rays on the environment. It requires additional protective measures and has certain limitations during use. The water-based resin system can usually be constructed and used in existing equipment and environmental systems, and is more favored by users of circuit board and circuit board protective coatings.

[0005] Compared with solvent-based systems, water-based resin systems require the resin to be treated to be hydrophilic so that it can form a water-soluble or water-dispersible solution under the action of alkali. For example, polyacrylic acid resin aqueous dispersions are prepared using hydrophilic acrylic acid or methacrylic acid and emulsifiers; polyurethane resin aqueous dispersions require the addition of dihydroxymethylpropionic acid (DMPA) containing carboxyl groups to provide hydrophilicity to form a dispersible state in water; water-based polyesters and water-based alkyds also add hydrophilic monomers containing carboxyl groups, and then form dispersions in water by adding alkali.

[0006] Patent CN114045101A discloses a waterborne polyurethane three-proof paint and its preparation method, which is composed of waterborne polyurethane resin, acrylic emulsion, composite dispersant, film-forming aid, composite defoamer, and deionized water. The document uses a combination of commercially available waterborne polyurethane and waterborne acrylic emulsion. Patent CN117586692A discloses a waterborne polyurethane three-proof paint and its preparation method and application, which is prepolymerized with polycarbonate diol and isocyanate and then chain extended, and dimethylol propionic acid (DMPA) is used as a hydrophilic substance to form an aqueous dispersion under the action of alkali.

[0007] The water-based resin system greatly reduces VOC and is an environmentally friendly technical solution. However, it also brings some defects. Since the resin system contains hydrophilic groups and substances, the water resistance and alkali resistance of the film after formation are greatly reduced; sometimes the glass transition temperature of the prepared resin is high, and the film formation during construction needs to be considered, and film-forming aids need to be added, which leads to the introduction of VOC and odor, which is also unfavorable to the environment.

[0008] Commonly used water-based resins are polyacrylic resin and polyurethane resin. Polyacrylic resin used for the protection of circuit boards and circuit boards needs to maintain a certain high temperature to prevent re-sticking, which requires raising the glass transition temperature, but it will cause it to crack easily at low temperatures; the ester group in acrylate will hydrolyze in both alkaline and acidic environments, causing damage to the polymer structure and reducing the protective effect.

[0009] Waterborne polyurethane can maintain a balance between flexibility and anti-adhesion within a certain glass transition range, which is slightly better than polyacrylic resin, but it cannot achieve the effect of maintaining flexibility at low temperatures and anti-adhesion at high temperatures. In addition, the salt spray resistance of this resin containing hydrophilic groups will be greatly reduced, and it is easy for water vapor and salt spray to penetrate, causing blistering and shedding of the paint film, and losing the protective effect. Summary of the invention

[0010] Based on the above-mentioned defects of the prior art, the object of the present invention is to provide an aqueous circuit board or circuit board protective coating liquid and a preparation method thereof.

[0011] In order to achieve the purpose of the present invention, the technical solution adopted is:

[0012] A water-based circuit board or circuit board protective coating liquid, calculated by weight, comprising:

[0013] 15-25 parts of (meth)acrylic acid modified polyethylene resin;

[0014] Base, wherein the base is added in an amount of 85-120:100 in a molar equivalent ratio to the (meth)acrylic acid content in the (meth)acrylic acid modified polyethylene resin;

[0015] preparing an aqueous dispersion of a modified polyethylene resin by using the (meth)acrylic acid-modified polyethylene resin and the base,

[0016] The water dispersion of the modified polyethylene resin and the polycarbodiimide curing agent are uniformly mixed in a mass ratio of 100:2-100:8 to obtain the water-based circuit board or circuit board protective coating liquid.

[0017] In a preferred embodiment of the present invention, the content of (meth)acrylic acid in the (meth)acrylic acid modified polyethylene resin is 10-20%, preferably 12-18%.

[0018] In a preferred embodiment of the present invention, the melt index of the (meth)acrylic acid modified polyethylene resin is 50-300, measured using ASTM D 1238, preferably 85-250.

[0019] In a preferred embodiment of the present invention, the preparation method of the aqueous dispersion of the modified polyethylene resin is as follows:

[0020] The (meth)acrylic acid modified polyethylene resin is heated and reacted with the alkali under normal pressure or pressure to obtain the product, wherein the reaction temperature of the heating reaction is 90-120°C.

[0021] In a preferred embodiment of the present invention, the base is aqueous ammonia or an organic base.

[0022] The organic base is any one or more of dimethylethanolamine, triethylamine, diethanolamine, triethanolamine or methyldiethanolamine.

[0023] Aqueous ammonia and dimethylethanolamine are preferred.

[0024] In a preferred embodiment of the present invention, the preparation method of the polycarbodiimide curing agent is as follows:

[0025] The isocyanate monomer containing a difunctional group is catalyzed by a catalyst to form a homopolymer or copolymer, and then reacts through the hydrophilic end group to form an aqueous dispersion.

[0026] The isocyanate monomer containing a difunctional group is any one or more of dicyclohexylmethane-4,4'-diisocyanate (HMDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and diphenylmethane diisocyanate (MDI).

[0027] Preferably dicyclohexylmethane-4,4'-diisocyanate (HMDI) or hexamethylene diisocyanate (HDI);

[0028] The hydrophilic end group is any one or more of methyl polyoxyethylene ether with a molecular weight of 200-500, butyl polyoxyethylene ether with a molecular weight of 200-500, triethylene glycol butyl ether or tetraethylene glycol butyl ether. Methyl polyoxyethylene ether MPEG350 and tetraethylene glycol butyl ether are preferred;

[0029] The catalyst is 3-methyl-1-phenyl-2-phospholene-1-oxide.

[0030] A method for preparing a water-based circuit board or circuit board protective coating liquid, specifically comprising:

[0031] The aqueous dispersion of the modified polyethylene resin and the polycarbodiimide curing agent are uniformly mixed in a mass ratio of 100:2-100:8, sprayed or brushed onto the surface of an integrated circuit board or a circuit board, and then dried at 25-80° C. to form a dense protective coating.

[0032] The beneficial effects of the present invention are:

[0033] First, the water-based modified polyolefin polymer / polycarbodiimide system circuit board or circuit board protective coating liquid prepared by the present invention can form a dense protective film without using any organic solvent or film-forming aid. It maintains excellent flexibility and protective effect at ultra-low temperatures (below -60°C) and does not re-stick at high temperatures.

[0034] Second, based on the chemical structure of the modified polyolefin structure, the protective layer formed by the water-based circuit board or circuit board protective coating liquid has very excellent acid resistance, alkali resistance, salt spray resistance, water resistance, oil resistance, and corrosion ion resistance, and has excellent insulation protection performance.

[0035] Third, the circuit board or circuit board protective coating liquid of the water-based modified polyolefin polymer / polycarbodiimide system uses water as a carrier, does not contain any organic solvents, and has excellent environmental protection. DETAILED DESCRIPTION

[0036] If not otherwise specified, as described in the present invention, each preferred solution is combined with other preferred solutions to form a new technical solution. Due to limited space, the combined technology is not described in detail, however, all technical solutions combined with each other should be considered to have been clearly described in the present invention.

[0037] The water-based circuit board or circuit board protective coating liquid of the present invention uses a water-based polyolefin polymer solution and a water-based polycarbodiimide curing agent to form an excellent flexibility in an ultra-low temperature environment and an anti-rebound effect in a high temperature environment; and provides excellent water resistance, hydrophobicity, acid resistance, alkali resistance and salt spray resistance.

[0038] Polyolefins, especially polyethylene, have a very low glass transition temperature (-120℃--90℃), and have good high temperature resistance and re-adhesion effect. They are an ideal resin that can withstand extreme high and low temperature environments. They also have excellent hydrophobic effect, acid resistance, alkali resistance, oil resistance, electrolyte resistance, and salt spray resistance. However, polyethylene has poor solubility, and the film forming process is usually carried out by high temperature laminating, which is not feasible for circuit boards and circuit boards.

[0039] Based on the advantages of polyethylene polymer, the present invention solves the problem of film-forming property by using (meth)acrylic acid to modify polyethylene resin to prepare water-based modified polyethylene resin. Due to the hydrophobicity of polyethylene chain segments and the crystallinity of the structure, a certain amount of carboxyl content has little effect on its water resistance and acid and alkali resistance.

[0040] The present invention also uses a water-based polycarbodiimide curing agent to react with the carboxyl group on the polymer chain, thereby eliminating the influence of the carboxyl group on the alkali resistance and providing a bulk cross-linking structure, so that the film is more dense and the resistance is further improved.

[0041] The (meth)acrylic acid-modified polyethylene resin used in the present invention is a polymer resin obtained by copolymerization of ethylene and (meth)acrylic acid.

[0042] The polycarbodiimide curing agent used in the present invention is a water-dispersible curing agent which is formed by reacting a difunctional isocyanate monomer with a catalyst to form a homopolymer or a copolymer and then reacting and modifying the monomer with a hydrophilic end group.

[0043] The following examples are used to illustrate the process and composition of the present invention. These examples are helpful for those skilled in the art to understand the present invention. However, the present invention is not limited to these examples.

[0044] Embodiment 1:

[0045] 200 g of (meth)acrylic acid modified polyethylene resin (methacrylic acid content: 20%, melt index: 210) was added to a reaction bottle with a reflux condenser, and then 750 g of deionized water and 35 g of 25% ammonia water were added, and heating was started to 98-105°C until the polymer particles were completely dissolved to form a translucent solution. The insoluble matter was removed by cooling and filtering to obtain an aqueous vinyl resin dispersion DS-1 with a solid content of 20.5% and a pH of 9.8.

[0046] Embodiment 2:

[0047] 200 g of (meth)acrylic acid modified polyethylene resin (acrylic acid content 20%, melt index: 300) was added to a reaction bottle with a reflux condenser, and then 750 g of deionized water and 38 g of 25% ammonia water were added, and heating was started to 98-105°C until the polymer particles were completely dissolved to form a translucent solution. The insoluble matter was removed by cooling and filtering to obtain an aqueous vinyl resin dispersion DS-2 with a solid content of 20.3% and a pH of 9.6.

[0048] Embodiment 3:

[0049] 190 g of (meth)acrylic acid modified polyethylene resin (acrylic acid content 20%, melt index: 300) was added to a reaction bottle with a reflux condenser, and then 750 g of deionized water and 46.5 g of dimethylethanolamine were added. The solution was heated to 98-105° C. until the polymer particles were completely dissolved to form a translucent solution. The solution was cooled and filtered to remove insoluble matter, thereby obtaining an aqueous vinyl resin dispersion DS-3 with a solid content of 21.3% and a pH of 10.5.

[0050] Embodiment 4:

[0051] 120g (meth)acrylic acid modified polyethylene resin (acrylic acid content 15%, melt index: 58) was added to a hydrothermal reaction synthesis reactor with stirring and pressure relief devices, and then 460g deionized water and 25g dimethylethanolamine were added, tightened, heated to 110-115℃, and the maximum pressure was set to 5Mpa. After stirring for 6 hours, the temperature was lowered to 45℃, the pressure was released, and the insoluble matter was removed by filtration to obtain a milky white translucent solution, which was the aqueous vinyl resin dispersion DS-4. The solid content was 20.5% and the pH was 10.8.

[0052] Embodiment 5:

[0053] 120g (meth)acrylic acid modified polyethylene resin (acrylic acid content 10%, melt index: 83) was added to a hydrothermal reaction synthesis reactor with a stirring and pressure relief device, and then 460g deionized water and 22.5g dimethylethanolamine were added, tightened, heated to 115-120℃, and the maximum pressure was set to 5Mpa. After stirring for 8 hours, the temperature was lowered to 45℃, the pressure was released, and the insoluble matter was removed by filtration to obtain a milky white solution, which was the aqueous vinyl resin dispersion DS-5. The solid content was 19.8% and the pH was 11.6.

[0054] Embodiment 6:

[0055] 120g (meth)acrylic acid modified polyethylene resin (acrylic acid content 12%, melt index: 150) was added to a hydrothermal reaction synthesis reactor with stirring and pressure relief devices, and then 460g deionized water and 21g dimethylethanolamine were added, tightened, heated to 115-120℃, and the maximum pressure was set to 5Mpa. After stirring for 4 hours, the temperature was lowered to 45℃, the pressure was released, and the insoluble matter was removed by filtration to obtain a milky white solution, which was the aqueous vinyl resin dispersion DS-6. The solid content was 20.1% and the pH was 10.3.

[0056] The polycarbodiimide curing agent was prepared as in Examples 7-9.

[0057] Embodiment 7:

[0058] 100g of dicyclohexylmethane-4,4'-diisocyanate (HMDI) and 2g of an organic phosphorus catalyst (3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide) were added to a reaction bottle with a stirrer, and the temperature was raised to 160°C under nitrogen protection and stirred for reaction for 8 hours to obtain a polycarbodiimide with an isocyanate group at the end. The NCO% was measured to be 4.2% and the degree of polymerization n=8.

[0059] The system was cooled to 120°C, 30 g of polyethylene glycol monomethyl ether (molecular weight 350, hereinafter referred to as MPEG350) was added and the reaction temperature was maintained at 120°C. After reacting for 4 hours, the isocyanate absorption peak at a wavelength of 2200-2300 detected by infrared spectroscopy (FTIR) disappeared. The system was then cooled to 80°C, 130 g of water was added and stirred for 25 minutes to obtain polyether-terminated polycarbodiimide CDI-1.

[0060] Embodiment 8:

[0061] 80g of dicyclohexylmethane-4,4'-diisocyanate (HMDI), 20g of toluene diisocyanate (TDI) and 2g of an organophosphorus catalyst (3-methyl-1-phenyl-2-phosphopentene-1-oxide) were added to a reaction bottle with a stirrer, heated to 140°C under nitrogen protection and stirred for 2 hours, then heated to 150°C and stirred for 3 hours to obtain a polycarbodiimide with an isocyanate group at the end. When the NCO% was measured to be 3.8%, the degree of polymerization n=10.

[0062] The system was cooled to 120°C, 25 g of polyethylene glycol monomethyl ether (molecular weight 350, hereinafter referred to as MPEG350) was added, and the reaction temperature was maintained at 120°C. After reacting for 4 hours, the isocyanate absorption peak at a wavelength of 2200-2300 detected by infrared spectroscopy (FTIR) disappeared. The system was then cooled to 80°C, 125 g of water was added, and stirred for 25 minutes to obtain polyether-terminated polycarbodiimide CDI-2.

[0063] Embodiment 9:

[0064] 60 g of dicyclohexylmethane-4,4'-diisocyanate (HMDI), 40 g of hexamethylene diisocyanate (HDI) and 2 g of an organophosphorus catalyst (3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide) were added to a reaction bottle with a stirrer, and the temperature was raised to 160° C. under nitrogen protection, and the reaction was stirred for 8 hours to obtain a polycarbodiimide with an isocyanate group at the end.

[0065] The NCO% was measured to be 4.8%, and the degree of polymerization was n=6.

[0066] The system was cooled to 120°C, 22 g of tetraethylene glycol butyl ether was added, and the reaction temperature was maintained at 120°C for 4 hours. The isocyanate absorption peak at a wavelength of 2200-2300 detected by infrared spectroscopy (FTIR) disappeared. The system was then cooled to 80°C, 122 g of water was added, and the blocked carbodiimide CDI-3 was obtained after stirring for 25 minutes.

[0067] Examples 10-14

[0068] The prepared aqueous vinyl resin dispersion and polycarbodiimide curing agent aqueous solution were mixed according to the proportions in Table 1.

[0069] Table 1: Examples 10-14

[0070]

[0071] Comparative Example 1:

[0072] The preparation method is the same as that of Example 1, using 200 g of polyethylene acrylate polymer (acrylic acid content 25%, melt index: 510) and 47.5 g of ammonia water.

[0073] Comparative Example 2:

[0074] According to the preparation method of patent CN114045101A, 85 parts of Stahl PU-3758 waterborne polyurethane resin, 6 parts of Lubrizol Carbost CR-765 emulsion, and 15 parts of deionized water are used.

[0075] Salt water resistance test:

[0076] The coated integrated circuit board was baked at 60℃ for 20 minutes, the dry film thickness was controlled at 15-20um, and then placed in a 5% sodium chloride aqueous solution. The coating was observed at regular intervals to see if there was bubbling, whitening, or shedding, and if there was any metal corrosion. The test lasted 3300 hours.

[0077] Acid resistance test:

[0078] The coated integrated circuit board was baked at 60℃ for 20 minutes, the dry film thickness was controlled at 15-20um, and then placed in a 10% sulfuric acid aqueous solution. The coating was observed at regular intervals to see if there was bubbling, whitening, or shedding, and if there was metal corrosion. The test lasted 240 hours.

[0079] Alkali resistance test:

[0080] The coated integrated circuit board was baked at 60℃ for 20 minutes, the dry film thickness was controlled at 15-20um, and then placed in a 10% sodium hydroxide aqueous solution. The coating was observed at regular intervals to see if there was bubbling, whitening, or shedding, and if there was metal corrosion. The test lasted 240 hours.

[0081] Salt spray resistance test method:

[0082] Bake the coated integrated circuit board at 60℃ for 20 minutes, control the dry film thickness to 15-20um, and then put it into the salt spray box, set the temperature to 45℃ and 5% sodium chloride. Take it out at regular intervals to observe whether the coating has blistering, whitening, shedding, and whether there is metal corrosion. The test lasts 400 hours.

[0083] High temperature and high humidity double 85 test method:

[0084] Bake the coated integrated circuit board at 60℃ for 20 minutes, control the dry film thickness to 15-20um, then put it into a constant temperature and humidity box, set the temperature to 85℃ and the humidity to 85%. Take it out after 1000 hours, dry it at room temperature for 2 hours, test the surface resistance and volume resistance, if there is no change, it passes.

[0085] High and low temperature cycle test method (refer to MIL-STD-810 and GB / T2423.17-2008):

[0086] Bake the coated integrated circuit board at 60℃ for 20 minutes, control the dry film thickness to 15-20um, and then put it into the high and low temperature cycle test chamber. The setting temperature range can generally reach -60℃ to 150℃, and the temperature difference is controlled within ±0.5℃. The relative humidity is set to 75%RH. The cooling and heating rates are 110℃ / h, and each time the temperature drops to the lowest and highest points, it is set to maintain for 2h. One cycle every 12 hours, and observe whether the paint film is cracked every 20 cycles. Test 600 cycles.

[0087] The test results are listed in Table 2.

[0088] Table 2: Performance test results of water-based circuit board or circuit board protective coating liquid

[0089]

[0090] It can be seen that compared with the prior art, the present invention has very excellent acid resistance, alkali resistance, salt spray resistance, water resistance, oil resistance, corrosion ion resistance, and has excellent insulation protection performance.

[0091] It can form a dense protective film without using any organic solvents or film-forming aids. It maintains excellent flexibility and protective effect at ultra-low temperatures (below -60°C) and does not stick back at high temperatures.

[0092] The electrical performance test and comparison after the hot and cold cycle of Example 13 were carried out, and the results are listed in Table 3.

[0093] Table 3: Comparison of hot and cold cycle electrical performance test of Example 13

[0094]

[0095] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A water-based circuit board or circuit board protective coating liquid, calculated by weight, characterized in that: include: 15-25 parts of (meth)acrylic acid modified polyethylene resin; Base, wherein the base is added in an amount of 85-120:100 in a molar equivalent ratio to the (meth)acrylic acid content in the (meth)acrylic acid modified polyethylene resin; preparing an aqueous dispersion of a modified polyethylene resin by using the (meth)acrylic acid-modified polyethylene resin and the base, The water dispersion of the modified polyethylene resin and the polycarbodiimide curing agent are uniformly mixed in a mass ratio of 100:2-100:8 to obtain the water-based circuit board or circuit board protective coating liquid.

2. The aqueous circuit board or circuit board protective coating liquid according to claim 1, characterized in that: The content of (meth)acrylic acid in the (meth)acrylic acid modified polyethylene resin is 10-20%.

3. The aqueous circuit board or circuit board protective coating liquid according to claim 1, characterized in that: The melt index of the (meth)acrylic acid modified polyethylene resin is 50-300, measured by ASTM D 1238 standard.

4. The aqueous circuit board or circuit board protective coating liquid according to claim 1, characterized in that: The preparation method of the aqueous dispersion of the modified polyethylene resin is as follows: The (meth)acrylic acid modified polyethylene resin is heated and reacted with the alkali under normal pressure or pressure to obtain the product, wherein the reaction temperature of the heating reaction is 90-120°C.

5. The aqueous circuit board or circuit board protective coating liquid according to claim 1, characterized in that: The base is aqueous ammonia or an organic base.

6. The aqueous circuit board or circuit board protective coating liquid according to claim 1, characterized in that: The preparation method of the polycarbodiimide curing agent is as follows: The isocyanate monomer containing a difunctional group is catalyzed by a catalyst to form a homopolymer or copolymer, and then reacts through the hydrophilic end group to form an aqueous dispersion. The difunctional isocyanate monomer is any one or more of dicyclohexylmethane-4,4'-diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate; The hydrophilic end group is any one or more of methyl polyoxyethylene ether with a molecular weight of 200-500, butyl polyoxyethylene ether with a molecular weight of 200-500, triethylene glycol butyl ether or tetraethylene glycol butyl ether; The catalyst is 3-methyl-1-phenyl-2-phospholene-1-oxide.

7. A method for preparing a water-based circuit board or circuit board protective coating liquid as claimed in any one of claims 1 to 6, characterized in that: Specifically: The aqueous dispersion of the modified polyethylene resin and the polycarbodiimide curing agent are uniformly mixed in a mass ratio of 100:2-100:8, sprayed or brushed onto the surface of an integrated circuit board or a circuit board, and then dried at 25-80° C. to form a dense protective coating.

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