UV-moisture dual-curing three-proofing adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of three-proofing adhesives, and particularly relates to a UV-moisture dual-curing three-proofing adhesive as well as a preparation method and application thereof. The UV-moisture dual-curing three-proofing adhesive disclosed by the invention is prepared from a polyurethane modified acrylate prepolymer, a fluorine-containing acrylate reactive diluent, a fluorine-free acrylate reactive diluent and a photoinitiator. The fluorine-containing acrylate reactive diluent with low surface tension is introduced and acts together with other components, so that the surface tension of the three-proofing glue can be reduced, the three-proofing glue has good wettability, the problem of glue shrinkage when the three-proofing glue is sprayed on a base material with low surface energy is solved, and the construction performance of the three-proofing glue is ensured; and meanwhile, after the three-proofing glue is coated and cured into a film, the electrical property is excellent, the volume resistivity is higher, the insulativity is good, and the safety and reliability of the printed circuit board can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of three-proof adhesives, and particularly relates to a UV-moisture dual-curing three-proof adhesive and a preparation method and application thereof. Background Art

[0002] As electronic products become more intelligent, portable and interconnected, the electronic assembly industry has also developed rapidly, and the requirements for assembled products have continued to increase. Printed circuit boards play an important role in assembled products, and their quality and reliability are becoming more and more important. Conformal adhesive can effectively protect printed circuit boards and reduce environmental damage to printed circuit boards.

[0003] Most of the early three-proof adhesives were solvent-based products, which were widely promoted in the market due to their low price, short curing time, and easy rework. However, since solvent-based three-proof adhesives are harmful to human health and with the continuous improvement of environmental protection requirements, environmentally friendly solvent-free ultraviolet light-moisture dual-curing three-proof adhesives (UV-moisture dual-curing three-proof adhesives) have begun to replace solvent-based three-proof adhesives and become the focus of research. UV-moisture dual-curing three-proof adhesives have been increasingly widely used due to their safety, environmental protection, fast curing speed, and excellent moisture and chemical resistance. However, the use of more no-clean flux in the welding process of printed circuit boards will reduce the surface energy of the printed circuit boards, resulting in the three-proof adhesive being unable to fully wet the circuit boards during the spraying process, resulting in shrinkage and other problems in some areas of the printed circuit boards, reducing the insulation performance of the printed circuit boards, increasing the risk of leakage or short circuits, and affecting the protection of the three-proof adhesive to the printed circuit boards. At the same time, in scenarios with high requirements for electrical performance, the UV-moisture dual-curing conformal adhesive itself needs to have high insulation performance, but the insulation performance of the current conformal adhesive cannot meet the requirements well.

[0004] Therefore, it is of great significance to develop a three-proof adhesive with good wettability and insulation properties. Summary of the invention

[0005] The present invention aims to solve one or more technical problems existing in the above-mentioned prior art, and at least provide a beneficial choice or create conditions. Specifically, the present invention provides a UV-moisture dual-curing three-proof adhesive, which has good wettability and insulation, and can improve the safety and reliability of printed circuit boards.

[0006] The inventive concept of the present invention: The UV-moisture dual-curing three-proof adhesive of the present invention includes a polyurethane modified acrylate prepolymer, a fluorine-containing acrylate reactive diluent, a fluorine-free acrylate reactive diluent, and a photoinitiator. The present invention introduces a fluorine-containing acrylate reactive diluent with low surface tension. The intermolecular force of the fluorine-containing compound is relatively weak. It works together with other components to reduce the surface tension of the three-proof adhesive, so that the three-proof adhesive has good wettability, solves the problem of shrinkage of the three-proof adhesive when sprayed on a substrate with low surface energy, and ensures the construction performance of the three-proof adhesive and the protective effect on the printed circuit board; at the same time, the three-proof adhesive has excellent electrical properties after coating and curing into a film, has higher volume resistance, good insulation, and can improve the safety and reliability of the printed circuit board.

[0007] Therefore, the first aspect of the present invention provides a UV-moisture dual-curing conformal adhesive.

[0008] Specifically, the UV-moisture dual-curing three-proof adhesive includes a polyurethane-modified acrylate prepolymer, a fluorine-containing acrylate reactive diluent, a fluorine-free acrylate reactive diluent, and a photoinitiator.

[0009] Preferably, the UV-moisture dual-curing conformal adhesive comprises 18-65 parts of polyurethane-modified acrylate prepolymer, 9-45 parts of fluorine-containing acrylate reactive diluent, 9-45 parts of fluorine-free acrylate reactive diluent, and 0.9-5.5 parts of photoinitiator, in parts by weight.

[0010] Further preferably, the UV-moisture dual-curing conformal adhesive comprises 20-60 parts of polyurethane-modified acrylate prepolymer, 10-40 parts of fluorine-containing acrylate reactive diluent, 10-40 parts of fluorine-free acrylate reactive diluent, and 1-5 parts of photoinitiator, in parts by weight.

[0011] Preferably, the UV-moisture dual-curing conformal adhesive further comprises at least one of a coupling agent and a defoaming agent.

[0012] Preferably, the UV-moisture dual-curing three-proof adhesive further includes a coupling agent and a defoaming agent, and in parts by weight, the UV-moisture dual-curing three-proof adhesive includes 18-65 parts of polyurethane modified acrylate prepolymer, 9-45 parts of fluorine-containing acrylate reactive diluent, 9-45 parts of fluorine-free acrylate reactive diluent, 0.9-5.5 parts of photoinitiator, 0.5-3.3 parts of coupling agent, and 0.5-2.2 parts of defoaming agent.

[0013] Further preferably, the UV-moisture dual-curing three-proof adhesive also includes a coupling agent and a defoaming agent, and in parts by weight, the UV-moisture dual-curing three-proof adhesive includes 20-60 parts of polyurethane modified acrylate prepolymer, 10-40 parts of fluorine-containing acrylate reactive diluent, 10-40 parts of fluorine-free acrylate reactive diluent, 1-5 parts of photoinitiator, 0.5-3 parts of coupling agent, and 0.5-2 parts of defoaming agent.

[0014] Preferably, the fluorine-containing acrylate reactive diluent includes at least one of hexafluorobutyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, and tridecafluorooctyl methacrylate.

[0015] Specifically, the present invention introduces fluorine-containing acrylate monomers. Since the fluorine atom has an extremely high electronegativity, the polarity of the CF bond (carbon-fluorine bond) is relatively high, so that the fluorine-containing compound exhibits a weaker intermolecular force at the molecular level, resulting in a lower surface tension. Its lower surface tension enables the three-proof adhesive to have higher wetting properties. At the same time, since the electronegativity of the fluorine atom is very high, the fluorine-carbon bond in the fluorine-containing acrylate polymer is very stable and not easy to break. This stability helps to maintain the insulating properties of the polymer in the electric field, reduce the transition and leakage of electrons, and make the three-proof adhesive have excellent insulating properties at the same time.

[0016] Preferably, the fluorine-free acrylate reactive diluent includes at least one of isobornyl acrylate, isobornyl methacrylate, ethoxyethoxyethyl acrylate, tetrahydrofuran acrylate, and cyclic trimethylolpropane formal acrylate.

[0017] Preferably, the photoinitiator includes at least one of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO), 2-hydroxy-2-methyl-1-phenylpropanone (photoinitiator 1173), 1-hydroxycyclohexyl benzophenone (photoinitiator 184), and benzophenone.

[0018] Preferably, the coupling agent includes a silane coupling agent; further preferably, the silane coupling agent includes at least one of 3-aminopropyltrimethoxysilane (KH540), γ-aminopropyltriethoxysilane (KH550), γ-glycidyloxypropyltrimethoxysilane (KH560), and γ-methacryloxypropyltrimethoxysilane (KH570).

[0019] Preferably, the defoamer includes a silicone defoamer; further preferably, the defoamer includes at least one of BYK-141, BYK-088, BYK-070, BYK-065, and BYK-057.

[0020] Specifically, the BYK-141, BYK-088, BYK-070, BYK-065 and BYK-057 were purchased from BYK Chemicals.

[0021] Preferably, the structural formula of the polyurethane modified acrylate prepolymer is as follows:

[0022]

[0023] Among them, n is 5-15.

[0024] The second aspect of the present invention provides a method for preparing the UV-moisture dual-curing conformal adhesive according to the first aspect of the present invention.

[0025] Specifically, the preparation method of the UV-moisture dual-curing conformal adhesive comprises the following steps:

[0026] The raw material components are mixed to prepare the UV-moisture dual-curing three-proof adhesive.

[0027] Preferably, the preparation method of the UV-moisture dual-curing three-proof adhesive is specifically, adding the photoinitiator, coupling agent, and defoaming agent to the fluorine-free acrylate reactive diluent and the fluorine-containing acrylate reactive diluent, vacuum stirring, and then adding the polyurethane modified acrylate prepolymer, vacuum stirring, to obtain the UV-moisture dual-curing three-proof adhesive.

[0028] A third aspect of the present invention provides a printed wiring board.

[0029] Specifically, the printed circuit board includes an adhesive layer formed by the UV-moisture dual-curing conformal adhesive described in the first aspect of the present invention.

[0030] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0031] (1) The UV-moisture dual-curing three-proof adhesive of the present invention includes a polyurethane modified acrylate prepolymer, a fluorine-containing acrylate reactive diluent, a fluorine-free acrylate reactive diluent, and a photoinitiator. The present invention introduces a low surface tension fluorine-containing acrylate reactive diluent, which works together with other components to reduce the surface tension of the three-proof adhesive, improve the wetting performance of the three-proof adhesive, solve the problem of shrinkage of the three-proof adhesive when sprayed on a substrate with low surface energy, and ensure the construction performance of the three-proof adhesive and the protective effect on the printed circuit board; at the same time, the three-proof adhesive has excellent electrical properties after coating and curing to form a film, has a higher volume resistance, good insulation, and can improve the safety and reliability of the printed circuit board.

[0032] (2) The fluorine atoms in the fluorine-containing acrylate reactive diluent of the present invention have extremely high electronegativity, resulting in a high polarity of the CF bond. Therefore, the intermolecular force of the fluorine-containing compound is small, so that the fluorine-containing acrylate reactive diluent has a lower surface tension, and thus the conformal adhesive has higher wetting properties. At the same time, since the electronegativity of the fluorine atom is very high, the fluorine-carbon bond is very stable and not easy to break, which helps to maintain the insulating properties of the polymer in the electric field, so that the conformal adhesive also has excellent insulating properties.

[0033] (3) The preparation process of the present invention is simple and convenient for large-scale production and application. DETAILED DESCRIPTION

[0034] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0035] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0036] Example 1

[0037] A UV-moisture dual-curing three-proof adhesive, comprising 30 parts of polyurethane modified acrylate prepolymer, 35 parts of hexafluorobutyl methacrylate, 30 parts of isobornyl acrylate, 3 parts of photoinitiator TPO, 1 part of coupling agent KH550, and 11 parts of defoaming agent BYK-14;

[0038] Among them, the structural formula of polyurethane modified acrylate prepolymer is:

[0039]

[0040] The preparation method of polyurethane modified acrylate prepolymer comprises the following steps: adding 2 mol of toluene-2,4-diisocyanate and catalyst dibutyltin laurate into a reactor, heating to 50°C, slowly dripping 1 mol of polyethylene glycol, reacting for 1 hour, heating to 60°C, measuring the NCO value to a calculated value, adding 1 mol of methacrylic acid and polymerization inhibitor hydroquinone, heating to 70°C; measuring the -NCO value to 5% of the calculated value, and obtaining the polyurethane modified acrylate prepolymer.

[0041] A method for preparing a UV-moisture dual-curing conformal adhesive comprises the following steps:

[0042] The photoinitiator, coupling agent and defoaming agent were added to isobornyl acrylate and hexafluorobutyl methacrylate, and the mixture was vacuumed and stirred for 15 minutes with a high-speed stirrer. After the mixture was completely dissolved, the polyurethane modified acrylate prepolymer was added and vacuum stirred for 15 minutes to obtain a UV-moisture dual-curing three-proof adhesive.

[0043] Example 2

[0044] A UV-moisture dual-curing conformal adhesive, comprising 30 parts of polyurethane modified acrylate prepolymer, 35 parts of dodecafluoroheptyl methacrylate, 30 parts of isobornyl acrylate, 3 parts of photoinitiator TPO, 1 part of coupling agent KH550, and 11 parts of defoaming agent BYK-14;

[0045] Wherein, the structural formula and preparation method of the polyurethane modified acrylate prepolymer are the same as those in Example 1.

[0046] A method for preparing a UV-moisture dual-curing conformal adhesive comprises the following steps:

[0047] The photoinitiator, coupling agent and defoamer were added to isobornyl acrylate and dodecafluoroheptyl methacrylate, and the mixture was vacuumed and stirred for 15 minutes with a high-speed stirrer. After the mixture was completely dissolved, the polyurethane modified acrylate prepolymer was added and vacuum stirred for 15 minutes to obtain a UV-moisture dual-curing three-proof adhesive.

[0048] Comparative Example 1

[0049] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, hexafluorobutyl methacrylate is replaced by an equal amount of dodecyl methacrylate, and the rest is the same as in Example 1.

[0050] Comparative Example 2

[0051] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses an equal amount of 3,3,5-trimethylcyclohexyl acrylate to replace hexafluorobutyl methacrylate, and the rest is the same as Example 1.

[0052] Performance Testing

[0053] The performance test of the UV-moisture dual-curing conformal adhesive prepared in Example 1-2 and Comparative Example 1-2 was carried out, and the specific test items and test methods are as follows:

[0054] Surface tension test: The surface tension of the three-proof adhesive is tested using the dynamic hanging drop method;

[0055] Viscosity test: Use cone-plate viscometer, use 1# rotor, 60rpm to test three times and calculate the average value;

[0056] Volume resistivity test: Use volume resistivity meter to test.

[0057] Among them, the surface tension test and viscosity test are tests on the three-proof adhesive before curing, and the volume resistivity test is to first perform UV-humidity dual curing on the three-proof adhesive and then perform the test. The UV-humidity dual curing is to first perform UV curing with a mercury lamp and then moisture curing. The curing conditions are:

[0058] Mercury lamp curing conditions: Use medium pressure mercury lamp for UV curing, and the radiation intensity is 200mW / cm 2 , total energy is 1500mJ / cm 2 ;

[0059] Moisture curing conditions: Curing for five days under constant temperature and humidity conditions (25±2°C, 50±5%RH).

[0060] The performance test results of the UV-moisture dual-curing conformal adhesive prepared in Example 1-2 and Comparative Example 1-2 are shown in Table 1.

[0061] Table 1: Performance test results of UV-moisture dual-curing conformal adhesives prepared in Examples 1-2 and Comparative Examples 1-2

[0062]

[0063] It can be seen from Table 1 that the UV-moisture dual-curing conformal adhesive of the present invention has a low surface tension and a high volume resistivity, which indicates that the UV-moisture dual-curing conformal adhesive of the present invention has good wettability and insulation.

[0064] Comparative Example 1 uses dodecyl methacrylate to replace the hexafluorobutyl methacrylate in Example 1 in equal amounts, so that the surface tension of Comparative Example 1 is significantly higher than that of Example 1, and the volume resistivity is significantly lower than that of Example 1, especially the volume resistivity. The volume resistivity of Example 1 of the present invention is 5.5 times that of Comparative Example 1. This shows that the use of fluorinated acrylate reactive diluent in the present invention can significantly reduce the surface tension of the three-proof adhesive and increase the volume resistivity, so that the three-proof adhesive has good wettability and insulation at the same time.

[0065] Comparative Example 2 uses 3,3,5-trimethylcyclohexyl acrylate to replace the hexafluorobutyl methacrylate in Example 1 in an equal amount, so that the surface tension of Comparative Example 1 is significantly higher than that of Example 1, and the volume resistivity is significantly lower than that of Example 1, especially the volume resistivity. The volume resistivity of Example 1 of the present invention is 5.1 times that of Comparative Example 1, indicating that the use of fluorinated acrylate reactive diluent in the present invention can significantly reduce the surface tension of the three-proof adhesive and increase the volume resistivity, so that the three-proof adhesive has good wettability and insulation at the same time.

[0066] In summary, the present invention introduces a fluorine-containing acrylate reactive diluent. Since the fluorine atom has an extremely high electronegativity, the polarity of the CF bond is relatively high. Therefore, the intermolecular force of the fluorine-containing compound is relatively small, so that it has a lower surface tension. It works together with other components to make the three-proof adhesive have good wettability, solve the problem of shrinkage of the three-proof adhesive when sprayed on a substrate with low surface energy, and ensure the construction performance of the three-proof adhesive; at the same time, the three-proof adhesive has excellent electrical properties after coating and curing to form a film, has a higher volume resistance, and has good insulation, which can improve the safety and reliability of the printed circuit board.

[0067] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A three-proof adhesive, characterized in that: It includes polyurethane modified acrylate prepolymer, fluorine-containing acrylate reactive diluent, fluorine-free acrylate reactive diluent and photoinitiator.

2. The three-proof adhesive according to claim 1, characterized in that: In parts by weight, the three-proof adhesive comprises 18-65 parts of polyurethane-modified acrylate prepolymer, 9-45 parts of fluorine-containing acrylate reactive diluent, 9-45 parts of fluorine-free acrylate reactive diluent, and 0.9-5.5 parts of photoinitiator.

3. The three-proof adhesive according to claim 1, characterized in that: The three-proof adhesive also includes at least one of a coupling agent and a defoaming agent.

4. The three-proof adhesive according to claim 3, characterized in that: The three-proof glue also includes a coupling agent and a defoaming agent, and by weight, the three-proof glue includes 18-65 parts of polyurethane modified acrylate prepolymer, 9-45 parts of fluorine-containing acrylate reactive diluent, 9-45 parts of fluorine-free acrylate reactive diluent, 0.9-5.5 parts of photoinitiator, 0.5-3.3 parts of coupling agent, and 0.5-2.2 parts of defoaming agent.

5. The three-proof adhesive according to claim 1, characterized in that: The fluorine-containing acrylate reactive diluent includes at least one of hexafluorobutyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, and tridecafluorooctyl methacrylate.

6. The three-proof adhesive according to claim 1, characterized in that: The fluorine-free acrylate reactive diluent includes at least one of isobornyl acrylate, isobornyl methacrylate, ethoxyethoxyethyl acrylate, tetrahydrofuran acrylate, and cyclic trimethylolpropane formal acrylate; and / or, the photoinitiator includes at least one of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl benzophenone, and benzophenone; and / or, the coupling agent includes a silane coupling agent; and / or, the defoamer includes a silicone defoamer.

7. The three-proof adhesive according to any one of claims 1 to 6, characterized in that: The structural formula of the polyurethane modified acrylate prepolymer is as follows Among them, n is 5-15.

8. The method for preparing the three-proof adhesive according to any one of claims 1 to 7, characterized in that: The following steps are involved: The raw material components are mixed to prepare the three-proof adhesive.

9. The preparation method according to claim 8, characterized in that: The photoinitiator, coupling agent and defoaming agent are added to the fluorine-free acrylate reactive diluent and the fluorine-containing acrylate reactive diluent, and then the polyurethane modified acrylate prepolymer is added and the mixture is stirred in vacuum to obtain the three-proof adhesive.

10. A printed circuit board, characterized in that: A glue layer formed by the triple-proof glue as described in any one of claims 1 to 7.

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