UV moisture dual-curing conformal coating

Abstract

The invention discloses a UV moisture dual-curing conformal coating, and belongs to the technical field of conformal coatings. The UV moisture dual-curing three-proofing paint is prepared from the following components in percentage by mass: 5 to 50 percent of aliphatic difunctional polyurethane acrylic resin, 10 to 60 percent of dual-curing polyurethane acrylate resin, 15 to 50 percent of acrylate monomer, 1.05 to 10 percent of photoinitiator, 0 to 2 percent of water removal agent, 0 to 2 percent of antioxidant, 0.01 to 2 percent of polymerization inhibitor, 0.05 to 2 percent of defoaming agent and 0.1 to 2 percent of fluorescent powder. Wherein the aliphatic two-functional-group polyurethane acrylic resin is Blukenau L-6201. The invention further discloses a preparation method of the polyurethane acrylic resin. The conformal coating can improve the adhesive force of a curing layer on the premise of ensuring full curing with low energy consumption, so that the uniformity and the uniformity of a split board during fracture are enhanced, and the problem that filaments are easily generated at fractures during board splitting is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of conformal coatings, and in particular to a UV-moisture dual-curing conformal coating. Background Art

[0002] Conformal coatings are specially formulated coatings with excellent resistance to high and low temperatures, as well as superior insulation, moisture, salt spray, mildew, leakage current, shock, dust, corrosion, aging, and corona properties. Polyurethane conformal coatings offer excellent overall properties, including quick drying, strong adhesion, impact resistance, excellent electrical insulation, exceptional flexibility, and resistance to wear and chemicals, making them particularly effective and suitable for corrosion protection of circuit boards. Currently, dual-curing UV / moisture-resistant polyurethane conformal coatings for electronic product protection primarily utilize polyurethane acrylate resins, other resin monomers, and additives, and are typically cured using traditional initiators such as TPO or TMO. In actual production, after conventional polyurethane conformal coatings are sprayed onto circuit boards or other substrates and cured in a UV curing oven, operators must separate large circuit boards containing multiple smaller ones or remove the edge strips. However, due to the low excitation efficiency of conventional initiators, which results in insufficient curing and poor adhesion between the conformal coating and the substrate, the curing layer often fails to completely break apart at the fracture surface, forming filaments. This not only significantly affects the product appearance, but also increases the difficulty of subsequent processing steps and the operator's workload, reducing production efficiency. Furthermore, conventional polyurethane conformal coatings struggle to balance low energy consumption with excellent curing performance, compromising process stability and operational efficiency.

[0003] In view of this, it is very necessary to develop a UV moisture dual-curing conformal coating that can achieve low-energy full curing and improve the adhesion between the cured layer and the substrate to ensure neat breakage during depaneling and avoid the formation of filaments. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a UV moisture dual-cure three-conformal coating. The three-conformal coating can improve the adhesion of the cured layer while ensuring sufficient curing with low energy consumption, thereby enhancing the uniformity and regularity of the board fracture, thereby effectively avoiding the problem of filaments easily generated at the fracture surface during board separation.

[0005] In order to solve the above problems, the technical solutions adopted by the present invention are as follows: A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 5-50% aliphatic difunctional polyurethane acrylate resin, 10-60% dual-cure polyurethane acrylate resin, 15-50% acrylate monomer, 1.05-10% photoinitiator, 0-2% water scavenger, 0-2% antioxidant, 0.01-2% polymerization inhibitor, 0.05-2% defoamer, and 0.1-2% phosphor; wherein the aliphatic difunctional polyurethane acrylate resin is Lancolu L-6201.

[0006] As a preferred embodiment of the present invention, the amount of the aliphatic difunctional polyurethane acrylic resin is 10-30%. The aliphatic difunctional polyurethane acrylic resin has no moisture curing function and only has unsaturated double bonds that can be UV-cured.

[0007] As a preferred embodiment of the present invention, the acrylate monomer is at least one of isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, n-butyl acrylate, isodecyl acrylate, lauric acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, pentaerythritol tetraacrylate, 4-acryloylmorpholine, ethoxyethoxyethyl acrylate, β-hydroxyethyl methacrylate, isobornyl acrylate, β-carboxyethyl acrylate, tripropylene glycol diacrylate, and pentaerythritol triacrylate.

[0008] As a preferred embodiment of the present invention, the photoinitiator consists of 2-hydroxy-2-methylphenylacetone, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide and benzophenone.

[0009] As a preferred embodiment of the present invention, the amounts of the components in the photoinitiator are as follows: 0.5-4% 2-hydroxy-2-methylphenylacetone, 0.5-4% 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, and 0.05-2% benzophenone.

[0010] In a preferred embodiment of the present invention, the dual-cure urethane acrylate resin comprises a photocurable group and a moisture-curable group. The photocurable group is one or more of vinyl, acryloxy, and mercapto groups, and the moisture-curable group is an isocyanate or siloxy group. Further preferably, the dual-cure urethane acrylate resin is at least one of EBECRYL® 4141, EBECRYL® 4396, and EBECRYL® 4150.

[0011] As a preferred embodiment of the present invention, the dewatering agent is one or more of a p-toluenesulfonyl isocyanate dewatering agent, an oxazolidine dewatering agent, and a triethyl orthoformate dewatering agent; the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, tea polyphenols, butylated hydroxyanisole, and tert-butylhydroquinone; and the polymerization inhibitor is a p-hydroxyanisole polymerization inhibitor.

[0012] In a preferred embodiment of the present invention, the defoamer is at least one of a mineral oil defoamer, an alcohol defoamer, a fatty acid and fatty acid ester defoamer, an amide defoamer, a phosphate defoamer, a silicone defoamer, a polyether defoamer, and a polyether-modified polysiloxane defoamer. More preferably, the defoamer is BYK-361.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The UV moisture dual-curing conformal coating of the present invention improves the physical properties of the cured layer, such as adhesion, by using a low-energy, fast-curing aliphatic difunctional polyurethane polyacrylate resin. It also ensures that the conformal coating is rapidly and fully cured under low UV energy, thereby effectively enhancing the uniformity and neatness of the fracture surface of the cured layer. This avoids the problem of filaments at the fracture surface during panel separation, reduces the difficulty of subsequent processing steps, and reduces the labor intensity of operators. This significantly improves operational efficiency and product quality, stabilizes the overall performance of the product, and meets industrial application requirements for energy conservation, emission reduction, and efficient production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Example 1 of the present invention; Figure 2 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Example 2 of the present invention; Figure 3 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Example 3 of the present invention; Figure 4 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Example 4 of the present invention; Figure 5 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Example 5 of the present invention; Figure 6 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Comparative Example 1 of the present invention; Figure 7 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Comparative Example 2 of the present invention; Figure 8This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Comparative Example 3 of the present invention; Figure 9 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Comparative Example 4 of the present invention; Figure 10 This is a panel separation effect diagram of the UV moisture dual-curing conformal coating prepared in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] The UV-moisture dual-cure conformal coating provided by the present invention is designed to address the problem of existing conformal coatings prone to filamentous material formation at the fracture surface during depaneling, which increases the difficulty of subsequent processing steps. The UV-moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 5-50% aliphatic difunctional urethane acrylate resin, 10-60% dual-cure urethane acrylate resin, 15-50% acrylate monomer, 1.05-10% photoinitiator, 0-2% water scavenger, 0-2% antioxidant, 0.01-2% polymerization inhibitor, 0-2% defoamer, and 0-2% phosphor. During research and development, the applicant discovered that using the aliphatic difunctional urethane acrylate resin Lancolu L-6201 as the key film-forming agent in the conformal coating, supplemented with the dual-cure urethane acrylate resin, not only maintains good adhesion between the cured layer and the substrate, ensuring a clean fracture surface during depaneling and preventing filamentous material, but also enables rapid and thorough curing of the cured layer at low UV energy. Furthermore, the amount of the aliphatic difunctional polyurethane acrylic resin is preferably 10-30%.

[0017] In the above formulation, the photoinitiator consists of 2-hydroxy-2-methylphenylacetone (photoinitiator 1173), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO), and benzophenone (photoinitiator BP). This photoinitiator combination ensures efficient excitation at low UV energy, achieving rapid and thorough curing of the cured layer while reducing energy consumption. Specifically, the dosage of each component in the photoinitiator is as follows: 0.5-4% 2-hydroxy-2-methylphenylacetone, 0.5-4% 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, and 0.05-2% benzophenone.

[0018] Preferably, the acrylate monomer is at least one of isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, n-butyl acrylate (BA), isodecyl acrylate, lauric acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, pentaerythritol tetraacrylate, 4-acryloylmorpholine (ACMO), ethoxyethoxyethyl acrylate (EOEOEA), β-hydroxyethyl methacrylate, isobornyl acrylate, β-carboxyethyl acrylate, tripropylene glycol diacrylate, and pentaerythritol triacrylate. The dual-cure polyurethane acrylate resin is EBECRYL® 4141, EBECRYL® 4396, or EBECRYL® 4150. The dehumidifier is p-toluenesulfonyl isocyanate (PTSI). The antioxidant is 2,6-di-tert-butyl-4-methylphenol (BHT). The polymerization inhibitor is p-hydroxyanisole (MeHQ). The defoamer is the surface additive BYK-361. The phosphor is Tinopal OB from BASF.

[0019] Example 1 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 125% of Lancolu L-620, 18.5% of EBECRYL® 4141, 13% of butyl acrylate, 5% of 4-acryloylmorpholine, 29.09% of EOEOEA, 3.5% of photoinitiator 1173, 2.5% of TMO, 1.1% of photoinitiator BP, 0.2% of PTSI, 0.2% of BHT, 0.11% of MeHQ, 1% of BYK-361, and 0.8% of Tinopal OB.

[0020] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0021] Example 2 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 128% of Lancolu L-620, 15.5% of EBECRYL® 4141, 13% of butyl acrylate, 5% of 4-acryloylmorpholine, 29.09% of EOEOEA, 3.5% of photoinitiator 1173, 2.5% of TMO, 1.1% of photoinitiator BP, 0.2% of PTSI, 0.2% of BHT, 0.11% of MeHQ, 1% of BYK-361, and 0.8% of Tinopal OB.

[0022] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0023] Example 3 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 15% of Lancolu L-620, 28.5% of EBECRYL® 4141, 13% of butyl acrylate, 5% of 4-acryloylmorpholine, 29.09% of EOEOEA, 3.5% of photoinitiator 1173, 2.5% of TMO, 1.1% of photoinitiator BP, 0.2% of PTSI, 0.2% of BHT, 0.11% of MeHQ, 1% of BYK-361, and 0.8% of Tinopal OB phosphor.

[0024] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0025] Example 4 A UV moisture dual-curing conformal coating comprises the following components, calculated by mass percentage: 113% of Lancolu L-620, 35% of EBECRYL® 4396, 44.09% of isobornyl acrylate, 3% of photoinitiator 1173, 3% of TMO, 1.3% of photoinitiator BP, 0.11% of MeHQ, and 0.5% of BYK-361.

[0026] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0027] Example 5 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 120% of Lancolu L-620, 13% of EBECRYL® 4150, 15% of EBECRYL® 4396, 43.80% of ethoxyethoxyethyl acrylate, 4% of photoinitiator 1173, 2.5% of TMO, 1% of photoinitiator BP, 0.2% of MeHQ, and 0.5% of BYK-361.

[0028] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0029] Comparative Example 1 A UV moisture dual-curing conformal coating comprises the following components, calculated by mass percentage: 3.5% of Lancolu L-62014, 13% of butyl acrylate, 5% of 4-acryloylmorpholine, 29.09% of EOEOEA, 3.5% of photoinitiator 1173, 2.5% of TMO, 1.1% of photoinitiator BP, 0.2% of PTSI, 0.2% of BHT, 0.11% of MeHQ, 1% of BYK-361, and 0.8% of Tinopal OB.

[0030] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0031] Comparative Example 2 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 25% Kunshan Custer CURE9581, 18.5% EBECRYL® 4141, 13% butyl acrylate, 5% 4-acryloylmorpholine, 29.09% EOEOEA, 3.5% photoinitiator 1173, 2.5% TMO, 1.1% photoinitiator BP, 0.2% PTSI, 0.2% BHT, 0.11% MeHQ, 1% BYK-361, and 0.8% Tinopal OB.

[0032] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0033] Comparative Example 3 A UV moisture dual-cure conformal coating comprising the following components, calculated by mass percentage: 48% EBECRYL® 4396, 44.05% isobornyl acrylate, 7.3% TMO, 0.11% MeHQ, and 0.5% BYK-361.

[0034] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0035] Comparative Example 4 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 12% of Lancolu L-620, 21% of EBECRYL® 4150, 25% of EBECRYL® 4396, 43.80% of ethoxyethoxyethyl acrylate, 4% of photoinitiator 1173, 2.5% of TMO, 1% of photoinitiator BP, 0.2% of MeHQ, and 0.5% of BYK-361.

[0036] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0037] Comparative Example 5 A UV moisture dual-cure conformal coating comprises the following components, calculated by mass percentage: 12% of Lancolu L-620, 21% of EBECRYL® 4150, 25% of EBECRYL® 4396, 43.80% of ethoxyethoxyethyl acrylate, 7.5% of photoinitiator 1173, 0.2% of MeHQ, 0.3% of BYK-361, and 0.2% of Tinopal OB.

[0038] Mix the components in the above proportions and stir thoroughly until uniform to obtain UV moisture dual-curing conformal coating.

[0039] Comparative test of split board effect The conformal coatings prepared in Examples 1-5 and Comparative Examples 1-5 were applied to circuit boards under the same conditions and cured using the same process. After curing, the surface dryness and adhesion properties were observed. The same operator was then asked to perform a board separation operation to observe the results.

[0040] 1. Test method UV curing oven: SK-103-300GDP, Shenzhen Sankun Technology Co., Ltd.; UV curing energy: UVA 400-420mJ / cm 2 , UVB 500-520mJ / cm 2 .

[0041] Surface drying: Use a 100um thick applicator to evenly apply a layer of conformal coating on the FR4 board. After passing through a UV curing oven, let it stand at room temperature for 1 minute. Touch the surface with your finger and lift it up. According to the degree of surface stickiness, give a grade of 0 to 5, where 0 is the surface not sticky at all, 1 is the surface slightly sticky, 2 is the surface somewhat sticky, 3 is the surface is quite sticky, when you lift your finger, the FR4 board will follow your finger slightly off the table, and then the FR4 board will fall immediately, 4 is very sticky, the FR4 board will follow your finger off the table very high before falling, and 5 is extremely sticky, the FR4 board will follow your finger off the table and will not fall.

[0042] Adhesion: Use a 100µm applicator to evenly apply a layer of conformal coating to the FR4 board. After passing through a UV curing oven, let it sit at room temperature for 1 minute, then test using the 100-grid method. Adhesion is graded from 0 to 5, with 0 being the best and 5 being the worst.

[0043] Depaneling: Use a brush to evenly apply a layer of conformal coating on the edge of the PCBA board. After passing through a UV curing oven, let it stand at room temperature for 1 minute. Place the edge of the board into the groove of the depaneler and manually break the board body to separate the board body and edge. Observe whether the cross section is clean and whether there are any filaments.

[0044] The results are shown in Table 1 and Figures 1 to 10 .

[0045] Table 1. Depaneling effect of circuit boards made with conformal coatings of Examples 1 to 5 and Comparative Examples 1 to 5.

[0046] Depend on Figures 1 to 10 As can be seen from the results in Table 1, when the formula ratio of the present invention is used, the test results of good curing and clean cross-section of the separated boards without drawing lines can be obtained; when the aliphatic difunctional polyurethane acrylic resin is not used, cross-section drawing lines or peeling will occur; when the aliphatic difunctional polyurethane acrylic resin is used but the aliphatic difunctional polyurethane acrylic resin specified by the present invention is not used, cross-section drawing lines or peeling will occur; when the aliphatic difunctional polyurethane acrylic resin specified by the present invention is used but the amount used is too small, cross-section drawing lines or peeling will occur; when the initiator combination of the present invention is not used, poor surface setting and poor curing will occur; when only part of the initiator of the present invention is used but the entire initiator combination is not used, poor surface setting and poor curing will also occur.

[0047] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A UV moisture dual-curing conformal coating, characterized by: The invention comprises the following components in percentage by mass: 5-50% aliphatic difunctional polyurethane acrylate resin, 10-60% dual-cure polyurethane acrylate resin, 15-50% acrylate monomer, 1.05-10% photoinitiator, 0-2% water scavenger, 0-2% antioxidant, 0.01-2% polymerization inhibitor, 0-2% defoaming agent, and 0-2% phosphor; Wherein, the aliphatic difunctional polyurethane acrylic resin is Lankolu L-6201.

2. The UV moisture dual-curing conformal coating according to claim 1, characterized in that: The amount of the aliphatic difunctional polyurethane acrylic resin is 10-30%.

3. The UV moisture dual-curing conformal coating according to claim 1 or 2, characterized in that: The acrylate monomer is at least one of isobornyl acrylate, isobornyl methacrylate, isooctyl acrylate, isooctyl methacrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, n-butyl acrylate, isodecyl acrylate, lauric acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, pentaerythritol tetraacrylate, 4-acryloylmorpholine, ethoxyethoxyethyl acrylate, β-hydroxyethyl methacrylate, isobornyl acrylate, β-carboxyethyl acrylate, tripropylene glycol diacrylate, and pentaerythritol triacrylate.

4. The UV moisture dual-curing conformal coating according to claim 1 or 2, characterized in that: The photoinitiator consists of 2-hydroxy-2-methylphenylacetone, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide and benzophenone.

5. The UV moisture dual-curing conformal coating according to claim 4, characterized in that: The dosage of each component in the photoinitiator is as follows: 0.5-4% of 2-hydroxy-2-methylphenylacetone, 0.5-4% of 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, and 0.05-2% of benzophenone.

6. The UV moisture dual-curing conformal coating according to claim 1 or 2, characterized in that: The dual-curing polyurethane acrylate resin has a light-curing group and a moisture-curing group, wherein the light-curing group is one or more of vinyl, acryloxy, and mercapto; and the moisture-curing group is isocyanate or siloxy.

7. The UV moisture dual-cure conformal coating according to claim 1 or 2, wherein: The dewatering agent is one or more of p-toluenesulfonyl isocyanate dewatering agents, oxazolidine dewatering agents, and triethyl orthoformate dewatering agents; the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, tea polyphenols, butylated hydroxyanisole, and tert-butylhydroquinone; and the polymerization inhibitor is a p-hydroxyanisole polymerization inhibitor.

8. The UV moisture dual-curing conformal coating according to claim 1 or 2, characterized in that: The defoaming agent is at least one of mineral oil defoaming agents, alcohol defoaming agents, fatty acid and fatty acid ester defoaming agents, amide defoaming agents, phosphate defoaming agents, silicone defoaming agents, polyether defoaming agents, and polyether-modified polysiloxane defoaming agents.

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