Super-hydrophobic tri-proof coating material for PCB board surface, preparation method and application thereof

Abstract

The application relates to an ultra-hydrophobic three-protection coating material for a PCB board surface, a preparation method and application, and the three-protection coating material comprises a primer and a topcoat, wherein the raw materials of the primer comprise bonding resins, additives and powder dispersion liquid in a mass ratio of (10-30):(0.3-2):100; the powder dispersion liquid is prepared by uniformly dispersing nano-silicon dioxide, aluminum hydroxide and silane modified diatomite in an organic solvent; the raw materials of the topcoat comprise a silicon sol alkaline solution, an organic alcohol and chlorosilane; the proportion between the silicon sol and the organic alcohol is (10-15) g:(700-900) mL, and the amount of the chlorosilane accounts for 4-6% of the total mass of the silicon sol alkaline solution and the organic alcohol. The three-protection coating formed by the primer and the topcoat has a great static water contact angle and a very low rolling angle, can make water drops slide down quickly after being generated, effectively reduces the accumulation of corrosion factors, and reduces the corrosion of moisture and other corrosion factors on the PCB board.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating materials, in particular to a super-hydrophobic type of three-proofing coating material for PCB surface, and a preparation method and application thereof. BACKGROUND

[0002] Three-proofing paint is a special formula of paint, which is used to protect the circuit board and its related equipment from the erosion of the environment. At present, the three-proofing paint mainly used is mainly of six types: poly-p-xylene three-proofing paint, polyurethane three-proofing paint, acrylic resin three-proofing paint, epoxy resin three-proofing paint, synthetic rubber three-proofing paint and organic silicon three-proofing paint.

[0003] Among them, the poly-p-xylene three-proofing paint is mostly made into film by plasma spraying, and has good protective performance, but the equipment and raw materials are extremely high; the polyurethane three-proofing paint has poor yellowing resistance, and has the problems of aging and sticking in high temperature and high humidity environment; the raw material price of the acrylic resin three-proofing paint is relatively high, and the light aging resistance is poor; the epoxy resin three-proofing paint has poor flexibility, high shrinkage rate, and difficult rework; the synthetic rubber three-proofing paint can form a thin film on the surface of the circuit board by means of solvent evaporation, and has good protective performance, but has poor adhesion to the substrate; the organic silicon three-proofing paint has excellent electrical protection performance and weather resistance, but the price is high.

[0004] The protective means of these three-proofing paints mainly lies in the shielding effect of corrosion factors, but under long-term humid conditions, the corrosion factors such as moisture will inevitably penetrate into the coating after accumulating on the surface of the substrate, thereby causing damage. SUMMARY

[0005] The present application aims to overcome the above technical deficiencies, and provides a super-hydrophobic type of three-proofing coating material for PCB surface, and a preparation method and application thereof, which solves the technical problem of poor shielding effect of three-proofing paint on corrosion factors such as moisture in the prior art.

[0006] To achieve the above technical purpose, the technical solution provided by the present application is as follows:

[0007] In a first aspect, the present application provides a super-hydrophobic type of three-proofing coating material for PCB surface, which comprises a primer and a topcoat, wherein the raw materials of the primer include bonding resin, additives and powder dispersion liquid in a mass ratio of (10-30):(0.3-2):100; the powder dispersion liquid is prepared by uniformly dispersing nano-silicon dioxide, aluminum hydroxide and silane modified diatomite in an organic solvent; the raw materials of the topcoat include silica sol alkalization liquid, organic alcohol and chlorosilane; the silica sol alkalization liquid is prepared by alkalization treatment of silica sol; the ratio between the silica sol and the organic alcohol is (10-15) g:(700-900) mL, and the amount of chlorosilane accounts for 4-6% of the total mass of the silica sol alkalization liquid and the organic alcohol.

[0008] In a second aspect, the present application provides a preparation method of an ultra-hydrophobic type three-protection coating material for a PCB board surface, comprising the following steps: uniformly dispersing nano-silicon dioxide, aluminum hydroxide and silane modified diatomite in an organic solvent to obtain a powder dispersion liquid, uniformly mixing a bonding resin, an additive and the powder dispersion liquid to obtain a primer; alkalinizing a silica sol to obtain a silica sol alkalinization liquid, uniformly mixing the silica sol alkalinization liquid and an organic alcohol, and then adding chlorosilane and placing for 20-26 hours to obtain a topcoat.

[0009] In a third aspect, the present application provides a construction process of an ultra-hydrophobic type three-protection coating for a PCB board surface, comprising the following steps: coating the primer on the surface of the PCB board, coating the topcoat after the surface is dried, and obtaining the ultra-hydrophobic type three-protection coating for the PCB board surface.

[0010] Compared with the prior art, the present application has the following beneficial effects:

[0011] The nano-silicon dioxide in the primer can be well stored in the silane modified diatomite to form microspheres with micro-nano structures, which can be uniformly distributed in the bonding resin and can maintain long-term hydrophobicity after being dried into a film, and the addition of the aluminum hydroxide can improve the electrical performance of the coating; the addition of chlorosilane in the topcoat forms a network with the silica sol, which is helpful to long-term hydrophobic stability, and the three-protection coating formed by the primer and the topcoat has a great static water contact angle (greater than 150°) and a very low rolling angle (less than 10°), which can make water droplets quickly slide off after being generated, effectively reduce the accumulation of corrosion factors, and reduce the corrosion of moisture and other corrosion factors on the PCB board. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a schematic diagram of the action mechanism of the primer of the present application;

[0013] Figure 2 is a scanning electron microscope (SEM) image of the silica sol used in Comparative Example 1 of the present application;

[0014] Figure 3 is a SEM image of the silica sol used in Example 1 of the present application. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0016] In view of the defect that the current three-proofing paint has poor shielding effect on moisture and other corrosion factors under long-term humid conditions, the application provides an ultra-hydrophobic three-proofing coating material for PCB surface and a preparation method thereof.

[0017] In a first aspect, the application provides an ultra-hydrophobic three-proofing coating material for PCB surface, comprising a primer and a topcoat, wherein,

[0018] The raw materials of the primer include bonding resin, additives and powder dispersion liquid with a mass ratio of (10-30):(0.3-2):100; the powder dispersion liquid is prepared by uniformly dispersing nano-silicon dioxide, aluminum hydroxide and silane modified diatomite in an organic solvent;

[0019] The raw materials of the topcoat include silica sol alkalization liquid, organic alcohol and chlorosilane; the silica sol alkalization liquid is prepared by alkalization treatment of silica sol; the ratio between the silica sol and the organic alcohol is (10-15) g:(700-900) mL, and the amount of chlorosilane accounts for 4-6% of the total mass of the silica sol alkalization liquid and the organic alcohol.

[0020] Preferably, the bonding resin includes fluorosilicon resin; the additives include one or more of dispersants and leveling agents. The application uses fluorosilicon resin to provide excellent weather resistance, that is, in addition to the high hydrophobicity of the coating of the application, the weather resistance such as acid and alkali resistance, temperature change resistance and artificial climate aging resistance is also very good due to the selection of fluorosilicon resin as the base material, which has the characteristics of good shielding effect on corrosion factors, and due to its low surface energy characteristics, it is difficult for corrosion factors to adhere to its surface (anti-fouling), further improving its corrosion resistance. At the same time, fluorosilicon resin has the advantages of fluorocarbon and organic silicon, and the cost is low.

[0021] Preferably, in the powder dispersion liquid, the mass ratio of the powder and the organic solvent is (5-15):(85-95). The powder includes nano-silicon dioxide, aluminum hydroxide and silane modified diatomite.

[0022] Preferably, the mass ratio of nano-silicon dioxide, silane modified diatomite and aluminum hydroxide is (5-7):(2-3):1; more preferably 7:3:1.

[0023] Preferably, the organic solvent includes one or more of dimethylbenzene and butyl acetate.

[0024] Preferably, the silica sol includes chain silica sol, and further preferably, it is MEK-ST-IP type silica sol of Rongda Chemical.

[0025] Preferably, the chlorosilane includes perfluorodecyltrichlorosilane.

[0026] In a second aspect, the present application provides a preparation method of an ultra-hydrophobic type three-proofing coating material for a PCB board surface, comprising the following steps:

[0027] The nano-silica, aluminum hydroxide and silane modified diatomite are added into an organic solvent to be uniformly dispersed to obtain a powder dispersion liquid, and the bonding resin, the additive and the powder dispersion liquid are uniformly mixed to obtain a primer.

[0028] The silica sol is subjected to an alkalization treatment to obtain a silica sol alkalization liquid, the silica sol alkalization liquid and an organic alcohol are uniformly mixed and dispersed, and then chlorosilane is added and placed for 20-26 hours to obtain a topcoat.

[0029] Preferably, the nano-silica, aluminum hydroxide and silane modified diatomite are added into an organic solvent and ground for 1.5-2.5 hours to be uniformly dispersed.

[0030] Preferably, the preparation steps of the silane modified diatomite include: the diatomite is dispersed in an alkaline alcohol solution, then n-octyl triethoxysilane is added and subjected to a silanization treatment, and then dried to obtain the silane modified diatomite.

[0031] Further preferably, the ratio of the diatomite and the alkaline alcohol solution is (20-40) g:(600-1000) mL, and the addition amount of the n-octyl triethoxysilane is 0.1-0.5% of the total mass of the diatomite and the alkaline alcohol solution.

[0032] Further preferably, the alkaline alcohol solution is prepared by mixing ethanol, deionized water and 28wt% ammonia water in a volume ratio of 20:2:1.

[0033] Further preferably, the silanization treatment is stirring and reaction at 45-55℃ for 22-26 hours, and the drying is freezing drying.

[0034] Preferably, the preparation steps of the silica sol alkalization liquid specifically include: the silica sol, deionized water and ammonia water are mixed in a ratio of (10-15) g:(70-90) mL:(30-50) mL, and then stirred for 8-12 minutes to obtain the silica sol alkalization liquid.

[0035] In a third aspect, the present application provides a construction process of an ultra-hydrophobic type three-proofing coating for a PCB board surface, comprising the following steps: applying a primer on the surface of the PCB board, applying a topcoat after the surface is dried, and obtaining the ultra-hydrophobic type three-proofing coating for the PCB board surface.

[0036] Preferably, the surface drying is drying at room temperature for 25-35 minutes after the primer is applied on the surface of the PCB board.

[0037] Preferably, the dry film thickness of the primer is 20-30 μm, and the total film thickness of the primer and the topcoat is 30-40 μm.

[0038] Main mechanism and advantages of the present application:

[0039] (1) Referring to Figure 1 , the nano-silica in the primer can be well stored in the pores of the silanized diatomite, thereby forming microspheres with micro-nano structures, the microspheres can be uniformly distributed in the subsequently added resin, and can maintain long-term hydrophobicity after drying into a film; the addition of aluminum hydroxide can improve the electrical properties of the coating, so that the material has high electrical strength and volume resistivity.

[0040] (2) The present application adds perfluorodecyltrichlorosilane in the topcoat, which spontaneously undergoes self-condensation during functionalization, and plays a crucial role in the formation of the network. The trichlorosilane groups on the silane and the hydroxyl groups on the silica mainly form covalent bonds through condensation reaction, thereby forming a primary functional layer on the surface of the silica nanoparticles. In the presence of sufficient trichlorosilane, the trichlorosilane groups on the silane form oligomers through random self-condensation reaction. When the trichlorosilane is in excess, the oligomers further react to form a network. Therefore, the super-hydrophobic tri-proof coating embedded with silica nanoparticles has a dense fluoralkyl network filler in the sub-nanometer and nanometer regions, which helps to maintain the long-term hydrophobic stability of the tri-proof coating.

[0041] The present application will be further described in detail through specific examples.

[0042] Example 1

[0043] A preparation method of a super-hydrophobic tri-proof coating material for a PCB board surface, comprising the following steps:

[0044] S1, preparing a primer:

[0045] S101, preparing modified diatomite: first, disperse 30 g of diatomite in a 1000 mL solution containing ethanol, deionized water and ammonia water (mass fraction of 28%) at a volume ratio of 20:2:1 and mechanically stir, then add 4 wt% of n-octyl triethoxysilane, and stir at 50°C for 24 h to silanize the surface of the diatomite; finally, freeze-dry to obtain silane-modified diatomite powder;

[0046] S102, preparing a powder dispersion liquid: add a mixture of 10 g of nano-silica, silane-modified diatomite and aluminum hydroxide (mass ratio of 7:3:1) to 90 g of solvent (dichlorobenzene and butyl acetate are compounded at a mass ratio of 3:2), and grind and disperse for 2 h to obtain a powder dispersion liquid;

[0047] S103, primer preparation: 20 g of fluorosilicon resin was selected as the adhesive resin, 100 g of powder dispersion liquid, 0.6 g of Dow Corning DC-3 silicone dispersant, and 0.6 g of Dow Corning 205SL silicone leveling agent were added, and a PCB surface super-hydrophobic type three-proofing coating material primer was prepared by stirring and dispersing processes.

[0048] S2, preparation of topcoat:

[0049] A 12 g of Yoroz Chemical MEK-ST-IP type silica sol (chain) was selected, 80 mL of deionized water, 40 mL of ammonia water (mass fraction of 28%) was dispersed and alkalized for 10 min to obtain a silica sol alkaline solution, and then added to 800 mL of anhydrous ethanol and dispersed for 30 min, and finally 5% of perfluorodecyltrichlorosilane based on the total mass of the silica sol alkaline solution and anhydrous ethanol was slowly added, and placed for 24 h to obtain a PCB surface super-hydrophobic type three-proofing coating material topcoat.

[0050] Air spraying can be used to apply the coating on the surface of the PCB, and the dry film thickness of the primer is about 20 μm. After drying at room temperature for 30 min, the surface is dry, and then the topcoat is sprayed, and the total film thickness is about 30 μm, to obtain a super-hydrophobic type three-proofing coating.

[0051] Comparative Example 1

[0052] The difference between Example 1 and Comparative Example 1 is only that the ordinary silica sol (granular) is used instead of the silica sol (chain) in Example 1, and the other steps and conditions are the same as in Example 1.

[0053] The scanning electron microscope images of the silica sol used in Example 1 and Comparative Example 1 are shown in Figure 2 and Figure 3 , Figure 2 the ordinary silica sol, Figure 3 the chain-like silica sol, compared with the ordinary silica sol, the chain-like silica sol can form a more dense network structure with perfluorodecyltrichlorosilane, thereby producing better water immersion resistance.

[0054] The three-proofing coatings obtained in Example 1 and Comparative Example 1 were tested for hydrophobic performance according to GB / T 23764-2009 "Performance Test Methods for Photocatalytic Self-cleaning Materials", and the results are shown in Table 1.

[0055] Table 1 Hydrophobic performance test results of three-proofing coatings obtained in Example 1 and Comparative Example 1

[0056]

[0057] The test results show that the coating prepared by using the silica sol (chain) in Example 1 is more outstanding in liquid immersion resistance than the coating prepared by using the ordinary silica sol (granular) in Comparative Example 1.

[0058] After the sample plate was soaked in water for 24 h, the PCB plate of Example 1 could still be powered on and operated, and experiments showed that the coating could effectively protect the PCB plate under humid conditions and significantly improve the service life thereof; the circuit in the PCB plate of Comparative Example 1 was in a short-circuit state, which led to a break in the signal processing or transmission line and resulted in a failure.

[0059] Example 2

[0060] The difference from Example 1 is only that the amount of the silica sol (chain-like) is adjusted to be 4 g, 10 g, 15 g, and 20 g, respectively, and the other steps and conditions are the same as those in Example 1.

[0061] The test results show that when the amount of the silica sol (chain-like) is too large, the perfluorodecyltrichlorosilane is insufficient, and only a primary functional layer on the nanoparticles can be formed in the functionalization process, so that the functional layer structure is not dense and the durability is weakened; when the amount of the silica sol (chain-like) is too small, a large amount of excess perfluorodecyltrichlorosilane is self-condensed and cannot form a network structure with the silica sol (chain-like); therefore, the amount of the silica sol (chain-like) is preferably 10-15 g, and the test results show that the obtained coating has a static water contact angle greater than 150° and a rolling angle less than 10°, and the amount of the silica sol (chain-like) is further preferably 12 g as used in Example 1.

[0062] Comparative Example 2

[0063] The difference from Example 1 is only that the aluminum hydroxide is removed, and the other steps and conditions are the same as those in Example 1.

[0064] The electrical performance tests of the super-hydrophobic three-proofing coatings obtained in Example 1 and Comparative Example 2 were carried out, in which the electrical strength test standard refers to GB / T 1408.1-2016, and the volume resistivity test standard refers to GB / T 31838.2-2019; the results are shown in Table 2.

[0065] Table 2 Electrical performance test results of the three-proofing coatings obtained in Example 1 and Comparative Example 2

[0066]

[0067] As shown in Table 2, the addition of aluminum hydroxide can improve the electrical performance of the coating, and the electrical strength and volume resistivity of the obtained three-proofing coating are improved, which indicates that the insulation performance is better.

[0068] The specific embodiments of the application described above do not constitute a limitation on the scope of protection of the application. Any various other corresponding changes and modifications made in accordance with the technical concept of the application should be included in the scope of protection of the claims of the application.

Claims

1. A superhydrophobic, three-proof coating material for PCB board surface, characterized in that, Including primer and topcoat, among which, The raw materials of the primer include an adhesive resin, additives, and a powder dispersion in a mass ratio of (10-30):(0.3-2):100; the powder dispersion is prepared by uniformly dispersing nano-silica, aluminum hydroxide, and silane-modified diatomaceous earth in an organic solvent. The raw materials for the topcoat include silica sol alkalization solution, organic alcohol, and chlorosilane; the silica sol alkalization solution is obtained by alkalizing silica sol; the ratio between silica sol and organic alcohol is (10-15) g: (700-900) mL, and the amount of chlorosilane used accounts for 4-6% of the total mass of silica sol alkalization solution and organic alcohol; The mass ratio of powder to organic solvent in the powder dispersion is (5-15):(85-95); The mass ratio of the nano-silica, the aluminum hydroxide, and the silane-modified diatomaceous earth is 7:1:3; The silica sol includes chain-like silica sol; The chlorosilanes include perfluorodecyltrichlorosilane.

2. The superhydrophobic three-proof coating material for PCB board surface according to claim 1, characterized in that, The adhesive resin includes fluorosilicone resin; the additives include one or more of dispersants and leveling agents.

3. The superhydrophobic three-proof coating material for PCB board surface according to claim 1, characterized in that, The organic solvent includes one or more of xylene and butyl acetate.

4. The method for preparing a superhydrophobic three-proof coating material for PCB board surface as described in any one of claims 1-3, characterized in that, Includes the following steps: Nano-silica, aluminum hydroxide and silane-modified diatomaceous earth are added to an organic solvent and dispersed evenly to prepare a powder dispersion. The adhesive resin, additives and powder dispersion are mixed evenly to obtain a primer. The silica sol is alkalized to obtain an alkalized silica sol solution. The alkalized silica sol solution is mixed and dispersed evenly with an organic alcohol, and then chlorosilane is added. After standing for 20-26 hours, a topcoat is obtained.

5. The method for preparing a superhydrophobic three-proof coating material for PCB board surface according to claim 4, characterized in that, The nano-silica, aluminum hydroxide, and silane-modified diatomaceous earth are added to an organic solvent and then ground for 1.5–2.5 hours to disperse them evenly.

6. The method for preparing a superhydrophobic three-proof coating material for PCB board surface according to claim 4, characterized in that, The preparation steps of the silane-modified diatomaceous earth include: dispersing diatomaceous earth in an alkaline alcohol solution, adding n-octyltriethoxysilane, performing silanization treatment, and drying to obtain silane-modified diatomaceous earth.

7. The method for preparing a superhydrophobic three-proof coating material for PCB board surface according to claim 6, characterized in that, The ratio of the diatomaceous earth to the alkaline alcohol solution is (20-40) g : (600-1000) mL; The amount of n-octyltriethoxysilane added is 0.1% to 0.5% of the total mass of the diatomaceous earth and the alkaline alcohol solution; The alkaline alcohol solution is prepared by mixing ethanol, deionized water and 28 wt% ammonia in a volume ratio of 20:2:

1. The silanization treatment was carried out by stirring at 45–55°C for 22–26 hours; the drying was carried out by freeze drying.

8. The method for preparing a superhydrophobic three-proof coating material for PCB board surface according to claim 4, characterized in that, The specific steps for preparing the silica sol alkalization solution include: mixing silica sol, deionized water and ammonia water in a ratio of (10-15) g: (70-90) mL: (30-50) mL and stirring for 8-12 minutes to obtain the silica sol alkalization solution.

9. A construction process for a superhydrophobic three-proof coating on the surface of a PCB board, characterized in that, Includes the following steps: A primer is applied to the surface of a PCB board, and after the surface dries, a topcoat is applied to obtain a superhydrophobic three-proof coating on the surface of the PCB board; the primer and topcoat are the primer and topcoat in the superhydrophobic three-proof coating material for PCB board surface as described in any one of claims 1-3.

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