A high-temperature-resistant uv resin for PCB solder mask ink and a preparation method thereof

Abstract

The present application relates to a kind of UV resin for high-temperature-resistant PCB solder resist ink and its preparation method, provide a kind of mixed epoxy acrylate UV resin generated by the combination reaction of m-xylylenediamine type four functional groups epoxy resin, o-cresol formaldehyde epoxy resin and acrylic acid or methacrylic acid.M-xylylenediamine type four functional groups epoxy resin and the 50% o-cresol formaldehyde epoxy resin solution and acrylic acid or methacrylic acid are reacted under the catalysis of triphenylphosphine, after sufficient reaction, then add phthalic anhydride, when the system acid value reaches 50-60mgKOH / g, the target UV resin is prepared.The resin can meet the use requirement of heat resistance more than 200 DEG C, has excellent high-temperature-resistant stability, simultaneously, in high-temperature-resistant PCB solder resist ink application, with low energy curing, and PCB substrate has excellent adhesion, the outstanding characteristics of stable high-temperature-resistant performance, can be widely adapted to the practical application demand of high-end PCB solder resist field.

Description

Technical Field

[0001] This invention belongs to the field of UV (ultraviolet light curing) resin preparation. In particular, this invention relates to a method for preparing a high-temperature resistant UV resin for PCB solder resist ink, which is applicable to the production and application of high-end PCB solder resist ink and belongs to the field of printed circuit board materials. Background Technology

[0002] UV curing materials are polymeric materials that can rapidly transform from a liquid to a solid state under ultraviolet light irradiation. With their outstanding advantages of high efficiency, energy saving, environmental protection, and high performance, they have become an important advanced material technology in modern manufacturing and are widely used in many fields such as coatings, inks, and adhesives. Their application in the field of PCB (printed circuit board) solder resist inks is particularly critical.

[0003] PCB solder resist ink is one of the core materials in the printed circuit board manufacturing process. It is mainly used to protect the PCB substrate, prevent short circuits, improve the substrate's insulation performance, and also enhance the appearance and extend the PCB's lifespan. With the rapid development of the electronics and information industry, high-end electronic devices are moving towards miniaturization, high power, and high integration, placing increasingly stringent requirements on the operating environment of PCBs. Especially in fields such as automotive electronics, aerospace, and industrial control, PCBs need to operate in high-temperature environments for extended periods. This places higher demands on the high-temperature resistance of solder resist inks, which typically need to maintain stable performance at temperatures above 200°C without yellowing, cracking, or peeling.

[0004] Currently, most commercially available UV-curable PCB solder resist inks suffer from insufficient high-temperature resistance. They are prone to thermal degradation and yellowing at temperatures above 180°C, leading to decreased solder resist adhesion and poor insulation performance, failing to meet the requirements of high-end PCBs. Furthermore, some high-temperature resistant resins exhibit drawbacks such as high curing energy, poor adhesion to PCB substrates, and poor process compatibility, limiting their application in the high-end PCB solder resist field.

[0005] o-Cresolaldehyde epoxy resin, due to its multifunctional molecular structure, forms a rigid, three-dimensional structure with numerous and tightly packed cross-linked bonds after curing. Therefore, its cured products exhibit excellent thermal stability, mechanical strength, electrical insulation, and chemical resistance, making it one of the ideal raw materials for preparing high-temperature solder resist inks. The control of the epoxy equivalent significantly affects its performance. m-Phenylenediamine-type tetrafunctional epoxy resin belongs to aromatic diamine-modified epoxy resins. Its structure contains benzene rings and aliphatic chains, giving its products not only outstanding temperature resistance, chemical resistance, and mechanical strength, but also high reactivity due to the presence of the aliphatic amine structure, allowing it to synergistically enhance overall high-temperature resistance with other resins.

[0006] Therefore, developing a UV resin that can achieve low-energy curing, excellent high-temperature resistance (heat resistance exceeding 200℃), and excellent adhesion to PCB substrates, to address the shortcomings of existing technologies and meet the practical application needs of high-end PCB solder resist inks, has become an important research direction in the current PCB materials field, with significant industrial application value and market prospects. Summary of the Invention

[0007] To address the technical problems of insufficient high-temperature resistance, high curing energy, and poor adhesion to PCB substrates in existing UV-cured PCB solder resist inks, this invention provides a high-temperature resistant UV resin for PCB solder resist inks and its preparation method. This resin can meet the requirements for heat resistance exceeding 200℃, possesses excellent high-temperature stability, achieves low-energy curing, and exhibits excellent adhesion to PCB substrates, thus meeting the application needs of high-end PCB solder resist fields.

[0008] The technical solution of this invention is as follows: a composition of UV resin for high-temperature resistant PCB solder resist ink, which is synthesized in two steps. The first step is to synthesize a mixed epoxy acrylate primary product; the second step is to obtain the target UV resin by modification with phthalic anhydride, wherein the phthalic anhydride accounts for 8-12% of the mass of the mixed epoxy acrylate primary product. The mixed epoxy acrylate primary product, based on reactants, has the following composition: i) m-Phenylenediamine type tetrafunctional epoxy resin; ii) 50% o-crestyrene epoxy resin solution; iii) Acrylic acid or methacrylic acid; iv) Triphenylphosphine catalyst; In the synthesis of the mixed epoxy acrylate primary product, the mass ratio of m-phenylenediamine type tetrafunctional epoxy resin to 50% o-cresol epoxy resin solution is 1:3-4, the mass ratio of acrylic acid or methacrylic acid to mixed epoxy resin is 1:5-5.6, and the amount of triphenylphosphine used is 0.06-0.2% of the total reaction volume.

[0009] The 50% o-cresol epoxy resin solution is prepared by dissolving o-cresol epoxy resin with an epoxy equivalent of 200-205 g / eq in a propylene glycol methyl ether acetate solution at a solid content of 50% under constant temperature conditions of 80°C, and stirring until homogeneous.

[0010] The process for preparing the UV resin composition for high-temperature resistant PCB solder resist ink involves a two-step synthesis. The first step is to synthesize the mixed epoxy acrylate primary product: m-phenylenediamine type tetrafunctional epoxy resin, 50% o-cresol epoxy resin solution, and acrylic acid or methacrylic acid under the catalysis of triphenylphosphine, and heat to react until the acid value of the system drops below 3 mg KOH / g. The second step is to obtain the target UV resin by modifying it with phthalic anhydride: the mixed epoxy acrylate primary product is mixed with phthalic anhydride and heated to react. When the acid value of the system reaches 50-60 mg KOH / g, the target UV resin is obtained.

[0011] The first step is to heat the mixture at 90-110℃ for 5-6 hours.

[0012] The second step involves heating the reaction at 100°C for 1 hour.

[0013] Beneficial effects The high-temperature resistant UV resin for PCB solder resist ink prepared by this invention has the following significant advantages compared with the prior art: 1. Excellent high-temperature resistance: This invention uses a combination of m-phenylenediamine type tetrafunctional epoxy resin and o-cresol formaldehyde epoxy resin with an epoxy equivalent strictly controlled at 200-205 g / eq. The synergistic effect of the two, combined with phthalic anhydride modification process, allows the resin to form a molecular structure with moderate crosslinking density and excellent thermal stability after curing. The heat resistance exceeds 200℃, and it can maintain stable performance in high-temperature environments for a long time without yellowing, cracking, or peeling, thus meeting the high-temperature resistance requirements of high-end PCB solder resist inks.

[0014] 2. Low-energy curing and high efficiency: Under the action of triphenylphosphine catalyst, the reactivity of the resin system is significantly improved, which can realize low-energy UV curing, greatly reduce curing energy consumption, shorten curing time, and improve production efficiency, which is in line with the industrial development trend of energy conservation and environmental protection.

[0015] 3. Excellent adhesion to PCB substrate: By modifying the resin with phthalic anhydride to adjust the acid value to 50-60 mg KOH / g, the surface properties of the resin are optimized, enabling it to form a good bond with the PCB substrate (such as FR-4 substrate). The excellent adhesion can effectively prevent the solder mask layer from falling off, and improve the reliability and service life of PCB products.

[0016] 4. Green and environmentally friendly: This invention uses UV curing technology, which emits no VOCs during the curing process, complying with strict environmental regulations. At the same time, the raw materials used are all conventional industrial products, which are widely available, non-toxic and harmless, taking into account both environmental protection and practicality. This represents an important direction for PCB solder resist materials to move towards high performance and green synergy. Detailed Implementation

[0017] All formulations used in this invention are qualified industrial products, not limited to manufacturers, and are all commercially available conventional products.

[0018] Throughout the patent application, the following terms have specific meanings:

[0019] The present invention will be further described below with reference to embodiments.

[0020] A high-temperature resistant UV resin for PCB solder resist ink is synthesized in two steps. The first step involves synthesizing a mixed epoxy acrylate primary product PA, and the second step involves modifying it with phthalic anhydride to obtain the target UV resin PB.

[0021] The mixed epoxy acrylate primary product PA is a reaction product of the following substances: i) m-Phenylenediamine type tetrafunctional epoxy resin; ii) 50% o-cresol epoxy resin solution (o-cresol epoxy resin epoxy equivalent 200-205 g / eq, prepared by dissolving 50% solids in propylene glycol methyl ether acetate solution); iii) Acrylic acid or methacrylic acid; iv) Triphenylphosphine catalyst; In the synthesis of the mixed epoxy acrylate primary product PA, the mass ratio of m-phenylenediamine type tetrafunctional epoxy resin to 50% o-cresol epoxy resin solution is 1:3-4. The two are reacted with acrylic acid or methacrylic acid (either of the two reactive acids can be selected) under the catalysis of triphenylphosphine at 90-110℃ for 5-6 hours until the acid value of the system drops below 3mgKOH / g.

[0022] The raw materials for synthesizing the target UV resin PB include: A) 100 parts of mixed epoxy acrylate primary product PA; B) Phthalic anhydride---8-12 parts (equivalent to 8-12% of the mass of the mixed epoxy acrylate primary product); The 50% o-cresol formaldehyde epoxy resin solution is prepared by pre-dissolving o-cresol formaldehyde epoxy resin with an epoxy equivalent of 200-205 g / eq in a propylene glycol methyl ether acetate solution at a solid content of 50% under constant temperature conditions of 80°C, and stirring until homogeneous. This range of epoxy equivalents ensures that the o-cresol formaldehyde epoxy resin has matching reactivity with m-phenylenediamine-type tetrafunctional epoxy resin, acrylic acid, or methacrylic acid, avoiding insufficient or excessive reaction, while also guaranteeing the high-temperature stability and UV curing performance of the final resin.

[0023] The synthesis process of the target UV resin involves mixing a mixed epoxy acrylate precursor with phthalic anhydride, controlling the reaction temperature at 100℃, and maintaining the reaction temperature for 1 hour. The acid value of the system is monitored in real time, and the reaction is stopped when the acid value reaches 50-60 mg KOH / g, yielding the target UV resin PB. The addition of phthalic anhydride can modify the mixed epoxy acrylate precursor, adjust the acid value of the resin, and improve the adhesion and high-temperature stability of the resin to the PCB substrate.

[0024] The aforementioned m-phenylenediamine type tetrafunctional epoxy resin has an aromatic structure and excellent high-temperature resistance. Its products have both good mechanical strength and chemical resistance, making them suitable for the use of PCB solder resist inks. The benzene ring in its molecular structure can improve the thermal stability of the resin, while the aliphatic chain structure ensures the reactivity of the resin.

[0025] The o-cresol formaldehyde epoxy resin has its epoxy equivalent strictly controlled at 200-205 g / eq. This range of epoxy equivalent ensures that the resin has suitable reactivity and works synergistically with the m-phenylenediamine type tetrafunctional epoxy resin to form a molecular structure with moderate crosslinking density, which not only ensures the UV curing rate but also improves the resin's high temperature resistance and mechanical properties.

[0026] The triphenylphosphine catalyst described above can efficiently catalyze the addition reaction of epoxy resin with acrylic acid or methacrylic acid, accelerate the reaction rate, ensure the reaction proceeds fully, and will not negatively affect the high temperature resistance and UV curing performance of the final resin. It also has good stability and can adapt to temperature changes during the reaction process.

[0027] The phthalic anhydride, as a modifier, can react with the hydroxyl groups in the mixed epoxy acrylate primary product to adjust the acid value of the resin to 50-60 mgKOH / g, thereby improving the adhesion between the resin and the PCB substrate. At the same time, it further optimizes the high-temperature stability and UV curing performance of the resin, ensuring that the resin does not yellow or crack under high-temperature conditions.

[0028] The propylene glycol methyl ether acetate solution, as a solvent for o-cresol epoxy resin, has good solubility and compatibility, and can uniformly dissolve o-cresol epoxy resin to form a stable 50% concentration solution. Moreover, it will not undergo side reactions with other raw materials during subsequent reactions, and can naturally remain in the resin system after the reaction is completed without affecting the final performance of the resin.

[0029] The UV resin used in the synthetic high-temperature resistant PCB solder resist ink can be cured with low energy under ultraviolet light irradiation. After curing, the heat resistance exceeds 200℃, exhibiting excellent high-temperature stability, good adhesion to PCB substrates, and good insulation properties. It can be widely used in high-end PCB solder resist fields, such as automotive electronics, aerospace, and industrial control, where high-temperature resistance is required for PCB products.

[0030] Example 1 Synthesis of mixed epoxy acrylate primary product PA1 The synthesis of the primary product was carried out according to the data listed in the table.

[0031]

[0032] Add components 1, 2, and 4 above to a flask, stir well, heat to 90-110℃, slowly add methacrylic acid dropwise, and after the addition is complete, maintain the temperature for 5-6 hours, monitor the acid value of the system in real time, and stop the reaction when the acid value drops below 3mgKOH / g to obtain the mixed epoxy acrylate primary product PA1 for later use.

[0033] Example 2 Synthesis of mixed epoxy acrylate primary product PA2 The synthesis of the primary product was carried out according to the data listed in the table.

[0034]

[0035] Add components 1, 2, and 4 above to a flask, stir well, heat to 90-110℃, slowly add methacrylic acid dropwise, and after the addition is complete, maintain the temperature for 5-6 hours, monitor the acid value of the system in real time, and stop the reaction when the acid value drops below 3mgKOH / g to obtain the mixed epoxy acrylate primary product PA2, which is ready for use.

[0036] Example 3 Synthesis of mixed epoxy acrylate primary product PA3 The synthesis of the primary product was carried out according to the data listed in the table.

[0037]

[0038] Add components 1, 2, and 4 above to a flask, stir well, heat to 90-110℃, slowly add methacrylic acid dropwise, and after the addition is complete, maintain the temperature for 5-6 hours, monitor the acid value of the system in real time, and stop the reaction when the acid value drops below 3mgKOH / g to obtain the mixed epoxy acrylate primary product PA3 for later use.

[0039] Example 4 Synthesis of comparative mixed epoxy acrylate primary product PA4 The synthesis of the primary product was carried out according to the data listed in the table. In this example, ordinary bisphenol A epoxy resin was used instead of m-phenylenediamine type tetrafunctional epoxy resin, and the other conditions were the same as in Example 1.

[0040]

[0041] Add components 1, 2, and 4 above to a flask, stir well, heat to 90-110℃, slowly add methacrylic acid dropwise, and after the addition is complete, maintain the temperature for 5-6 hours, monitor the acid value of the system in real time, and stop the reaction when the acid value drops below 3mgKOH / g to obtain the comparative mixed epoxy acrylate primary product PA4, which is ready for use.

[0042] Example 5 Preparation of the target UV resin PB The resin was used to synthesize the corresponding target UV resins PB1, PB2, PB3, and PB4 using the above four mixed epoxy acrylate primary products PA according to the formulations in the table below.

[0043]

[0044] The initial products from the above components were added to a flask, heated to 100°C, phthalic anhydride was added, and the mixture was stirred until homogeneous. The reaction was carried out at a constant temperature of 100°C for 1 hour. The acid value of the system was monitored in real time. When the acid value reached 50-60 mg KOH / g, the reaction was stopped and the mixture was cooled to room temperature to obtain the target UV resins PB1, PB2, PB3, and PB4.

[0045] Example 6: Testing Curing Energy (Low Energy Curing Performance) Using the four experimental products from Example 5 above, photoinitiator TPO and 184 (mass ratio 1:1) were added, with the addition amount being 4% of the resin mass. The mixture was stirred evenly, and 75 μm films were formed. The films were cured under UV light (in a nitrogen atmosphere). The minimum curing energy when the degree of cure (RAU) was greater than 80% was measured. Three parallel tests were performed for each group, and the average value was taken. The specific data are shown in Table 6.

[0046]

[0047] The comparative experiments revealed that the target UV resins (PB1, PB2, PB3) synthesized in this invention have a faster curing speed and require lower curing energy to reach 80% curing degree, all below 100 mJ / cm², achieving low-energy curing. In contrast, the control group PB4 (using ordinary bisphenol A epoxy resin) requires as much as 150 mJ / cm², and its curing efficiency is significantly lower than that of the product of this invention. This indicates that the combination of the m-phenylenediamine type tetrafunctional epoxy resin and the o-cresol epoxy resin selected in this invention, combined with the catalytic effect of triphenylphosphine, can effectively improve the UV curing activity of the resin and reduce curing energy consumption.

[0048] Example 7: Testing high temperature resistance and adhesion The cured films from the four sets of experiments in Example 6 above were used to test their high-temperature resistance and adhesion to the PCB substrate (FR-4 substrate) according to relevant standards. The test conditions were: room temperature 25℃, humidity 50-60%. The high-temperature resistance test adopted the constant temperature aging method, in which the cured film was placed in a constant temperature oven at 220℃ and kept at that temperature for 24 hours. The appearance changes were observed and the performance was tested. The adhesion test adopted the cross-cut test (GB / T 9286-1998). The specific indicators are shown in Table 7.

[0049]

[0050] As can be seen from the table, the target UV resins (PB1, PB2, PB3) synthesized in this invention exhibit excellent high-temperature resistance. After being kept at 220℃ for 24 hours, they showed no yellowing, cracking, or peeling, fully meeting the requirements for heat resistance exceeding 200℃. Simultaneously, their adhesion to the PCB substrate reached grade 0, indicating excellent adhesion. In contrast, the control group PB4 showed significant yellowing and slight cracking after being kept at 220℃ for 24 hours, with an adhesion grade of only grade 2, significantly lower than the products of this invention. This demonstrates that this invention, through reasonable raw material ratios and process design, effectively improves the high-temperature stability and adhesion to the PCB substrate of the resins, making them widely adaptable to the practical application needs of high-end PCB solder mask applications.

Claims

1. A composition of a UV resin for high-temperature resistant PCB solder resist ink, characterized in that, The synthesis is carried out in two steps. In the first step, a mixed epoxy acrylate primary product is synthesized. In the second step, the target UV resin is obtained by modification with phthalic anhydride, where phthalic anhydride accounts for 8-12% of the mass of the mixed epoxy acrylate primary product. The mixed epoxy acrylate primary product, based on reactants, has the following composition: i) m-Phenylenediamine type tetrafunctional epoxy resin; ii) 50% o-crestyrene epoxy resin solution; iii) Acrylic acid or methacrylic acid; iv) Triphenylphosphine catalyst; In the synthesis of the mixed epoxy acrylate primary product, the mass ratio of m-phenylenediamine type tetrafunctional epoxy resin to 50% o-cresol epoxy resin solution is 1:3-4, the mass ratio of acrylic acid or methacrylic acid to mixed epoxy resin is 1:5-5.6, and the amount of triphenylphosphine used is 0.06-0.2% of the total reaction volume.

2. The composition of UV resin for high-temperature resistant PCB solder resist ink according to claim 1, characterized in that, The 50% o-cresol epoxy resin solution is prepared by dissolving o-cresol epoxy resin with an epoxy equivalent of 200-205 g / eq in a propylene glycol methyl ether acetate solution at a solid content of 50% under constant temperature conditions of 80°C, and stirring until homogeneous.

3. A process for preparing the composition of UV resin for high-temperature resistant PCB solder resist ink as described in claim 1 or 2, characterized in that, Synthesized in two steps The first step is to synthesize the mixed epoxy acrylate primary product: m-phenylenediamine type tetrafunctional epoxy resin, 50% o-cresol epoxy resin solution, and acrylic acid or methacrylic acid under the catalysis of triphenylphosphine, and heat to react until the acid value of the system drops below 3 mg KOH / g. The second step is to obtain the target UV resin by modifying it with phthalic anhydride: the mixed epoxy acrylate primary product is mixed with phthalic anhydride and heated to react. When the acid value of the system reaches 50-60 mg KOH / g, the target UV resin is obtained.

4. The process according to claim 3, characterized in that, The first step is to heat the mixture at 90-110℃ for 5-6 hours.

5. The process according to claim 3, characterized in that, The second step involves heating the reaction at 100°C for 1 hour.

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