High-photosensitive resin for PCB (printed circuit board) solder resist ink and preparation method of high-photosensitive resin

Abstract

The invention belongs to the field of printed circuit board materials, and particularly relates to high-photosensitive resin for PCB solder resist ink and a preparation method of the high-photosensitive resin. The method comprises the following steps: 1) uniformly mixing a butyl ester compound, an acid ester compound and aromatic hydrocarbon in proportion to prepare an acrylic prepolymer; 2) carrying out functional modification on the acrylic acid prepolymer to prepare a primarily modified prepolymer; and 3) performing stability optimization on the primarily modified prepolymer to prepare the high photosensitive resin for the PCB solder resist ink. Fluorine migration thermodynamics, a network topology structure and excited state quenching depth are combined, surface-body-durability triple optimization is achieved on the molecular level, and a solid material basis is provided for manufacturing of a high-reliability printed circuit board (PCB).

Description

Technical Field

[0001] This invention belongs to the field of printed circuit board materials, specifically relating to a high photosensitive resin for PCB solder resist ink and its preparation method. Background Technology

[0002] High-sensitivity resin solder resist ink is a key functional material in modern printed circuit board (PCB) manufacturing, mainly composed of photosensitive resin, photoinitiator, filler, toughening agent, and reactive diluent. It forms a highly cross-linked network through UV-induced free radical polymerization, providing electrical insulation, oxidation protection, and moisture protection for the PCB. However, this type of material suffers from several key performance defects during application. First, uneven coverage and rheological mismatch: In corners, edges, or areas with uneven copper thickness on the circuit board, solder resist ink often exhibits localized insufficient thickness, forming the so-called "exposed copper" phenomenon. "Exposed copper" areas typically show a resin matrix thickness significantly lower than the pigment particle diameter, exposing the underlying copper foil to the external environment. The oxygen barrier capacity of these areas is significantly reduced, becoming preferential oxidation sites. Oxidation products further damage the interfacial bond between the solder resist layer and the copper layer, creating a vicious cycle. Second, curing shrinkage and internal stress accumulation mechanisms: High-sensitivity resins undergo significant volume shrinkage during UV curing, especially in large copper foil areas. The essence of this phenomenon is the change in molecular packing of acrylate monomers from van der Waals bonds to covalent bonds. During polymerization, the linear shrinkage rate of acrylate groups reaches 10-15%, leading to overall volume shrinkage. On non-uniform substrates, the internal stress generated by this shrinkage cannot be uniformly released, especially in the copper-resin-copper transition zone, forming significant stress concentration, generating microcracks, and exhibiting typical "stress cracking" characteristics—cracks perpendicular to the stress direction, and significant stress whitening zones at the crack tips. These microcracks become preferential channels for moisture and electrolyte penetration; even micron-sized cracks can increase the ion diffusion rate by 2-3 orders of magnitude, significantly reducing the long-term insulation reliability of PCBs. III. UV-induced photochemical aging process: High-sensitivity solder resist layers undergo a series of complex photochemical degradation reactions under long-term UV radiation. The most important of these include: photo-oxidative pyrolysis, changes in crosslink density, and chromophore formation. UV light with wavelengths of 355-365 nm can break specific chemical bonds in resin molecules, generating free radicals. These free radicals form peroxides in the presence of oxygen, further triggering chain breakage or abnormal crosslinking. In addition, another important change caused by photoaging is the uneven evolution of crosslinking density. In the early stages of UV aging, residual reactive groups continue to crosslink, making the material harder and more brittle; while long-term aging leads to main chain breakage, a decrease in crosslinking density, softening of the material and loss of its protective function, while also resulting in a high degree of microstructural inhomogeneity. This aging process ultimately severely reduces the strain adaptability of the solder mask in thermal cycling environments, especially during temperature cycling, where the fracture strain of aged samples decreases, becoming a key factor affecting PCB reliability. Summary of the Invention

[0003] This invention addresses the technical challenges of traditional high-photosensitive resins, such as uneven solder resist coverage, curing shrinkage and cracking, and ultraviolet aging, by providing a high-photosensitive resin for PCB solder resist ink and its preparation method.

[0004] The main objective of this invention is: 1. Improve resin leveling through molecular structure design to eliminate copper exposure at corners / edges and ink buildup in flat areas; 2. Reduce curing shrinkage and release internal stress to inhibit the formation of microcracks; 3. Introduce anti-UV aging groups to extend the outdoor service life of the solder resist layer.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A method for preparing a highly photosensitive resin for PCB solder resist ink. The method includes: 1) Prepare an acrylic acid prepolymer by uniformly mixing butyl ester compounds, acid ester compounds, and aromatic hydrocarbons in a certain proportion; 2) Functionally modify the acrylic prepolymer to prepare a prepolymer with initial modification; 3) The stability of the modified prepolymer was optimized to prepare a high photosensitive resin for PCB solder resist ink.

[0007] As a preferred option Step 1) The butyl ester compound is hexafluorobutyl methacrylate; Step 1) The ester compound is hydroxyethyl acrylate; Step 1) The aromatic hydrocarbon is styrene; In step 1), the butyl ester compounds, acid ester compounds, and aromatic hydrocarbons are mixed evenly at a mass ratio of 1:(0.9-1.4):(0.2-0.4).

[0008] As a preferred option Step 1) The acrylic prepolymer is prepared by adding 40 wt% of azobisisobutyronitrile (AIBN) to a uniformly mixed mixture of butyl ester compounds, acid ester compounds, and aromatic hydrocarbons under a nitrogen atmosphere and a temperature of 63–67 °C, and reacting for 5–6 h.

[0009] As a preferred option Step 2) The specific operation of the functional modification is as follows: Add 25–35 wt% of dipentaerythritol hexaacrylate and 0.03–0.05 wt% of hydroquinone polymerization inhibitor to the prepolymer, and continue the reaction for 3–4 h at an ambient temperature of 65–75 °C.

[0010] As a preferred option Step 3) The specific operation of stability optimization is as follows: Add 3-4 wt% of the composite stabilizer to the modified prepolymer and disperse it for 30-60 min at an ambient temperature of 50-60℃.

[0011] As a preferred option The composite stabilizer is composed of a hindered amine light stabilizer and a benzotriazole ultraviolet absorber (UV-326) in a mass ratio of 2:1.

[0012] As a preferred option Step 3) The high photosensitive resin used to prepare the PCB circuit board solder resist ink is: Add the mixed solution to the modified prepolymer mixture after stability optimization, stir for 30 to 60 min at an ambient temperature of 23 to 27 °C, and adjust the solid content to 63 to 67% and the viscosity to 4500 to 5500 cps.

[0013] As a preferred option The mixed solution is a homogeneous mixture of propylene glycol methyl ether acetate and cyclohexanone at a mass ratio of 3:(0.8-1.1).

[0014] A high-photosensitive resin for solder resist ink on PCB circuit boards.

[0015] The core of this invention lies in the design of fluorinated segments with directional surface migration, a dual-network cross-linked structure, and the system integration of a synergistic anti-aging system, which improves the three key properties of high-sensitivity resin solder resist ink: leveling, shrinkage resistance, and aging resistance.

[0016] This invention utilizes hexafluorobutyl methacrylate (HBMA) as the key fluorine functional monomer. Through a surface energy difference-driven molecular migration mechanism, it achieves efficient enrichment of fluorine on the resin surface. The high stability and low polarity of the fluorine-carbon bond result in a significantly lower surface energy for the fluorinated segments compared to the resin matrix. This significant surface energy difference drives the spontaneous enrichment of fluorinated segments at the gas-liquid interface, forming a directional arrangement perpendicular to the surface. This surface fluorine enrichment significantly reduces the surface tension of the resin system and simultaneously improves the wettability of copper foil. Furthermore, the surface-enriched fluorine effectively inhibits inward diffusion, greatly reducing or even preventing fluorine diffusion / migration to the PCB during ink curing. Fluorine diffusion to the PCB surface drastically worsens the wettability of the solder resist ink, leading to decreased coverage, reduced adhesion strength, and potentially even corrosion or short circuits of the PCB. Low surface tension directly reduces the liquid backflow effect, especially at line corners and in areas with high copper thickness. By precisely controlling the content and molecular weight of hexafluorobutyl methacrylate, the optimal balance between the thixotropic properties and surface activity of the ink is achieved, reducing the "exposed copper" defect rate and effectively solving the problem of uneven coverage of traditional solder resist inks in areas with high copper thickness.

[0017] To address the shrinkage stress problem during photocuring, this invention constructs a dual-network crosslinking structure based on dipentaerythritol hexaacrylate and a flexible acrylic backbone. The core of this molecular architecture design lies in achieving synergistic optimization of "high crosslinking density" and "low shrinkage stress," fundamentally overcoming the performance limitations of traditional single-network structures. Dipentaerythritol hexaacrylate, as a hexafunctional crosslinking agent, provides a high density of crosslinking points, forming a rigid backbone network. When all six acrylate functional groups in dipentaerythritol hexaacrylate participate in the reaction, each molecule can form six crosslinking points, offering opportunities for enhanced optimization. Simultaneously, the flexible acrylic backbone interweaves with the rigid network formed by dipentaerythritol hexaacrylate through side groups, constructing a second-level elastic network. This "rigid backbone-elastic filler" dual-network structure achieves complementary optimization of mechanical properties. This dual-network structure significantly alters the shrinkage behavior of the resin. The dipentaerythritol hexaacrylate network forms first, establishing a preliminary backbone; subsequently, the flexible segments complete crosslinking within the confined space of the pre-formed rigid network. This "stepwise crosslinking" mechanism effectively reduces overall volume shrinkage. This reduces the stress concentration factor in the copper-resin-copper transition zone of the dual-network structure, making it much lower than that of the traditional system. This improved stress distribution directly reduces the generation of microcracks and is also beneficial for further blocking the internal diffusion path of fluorine and inhibiting the inward diffusion / migration of fluorine.

[0018] To address the problem of UV aging, this invention develops a synergistic anti-aging system based on hindered amine light stabilizers and 2-(2-hydroxy-5-methylphenyl)benzotriazole, achieving end-to-end protection from light absorption to free radical scavenging. 2-(2-hydroxy-5-methylphenyl)benzotriazole exhibits highly efficient absorption of UV light in the 280–360 nm wavelength range due to its unique molecular structure (a conjugated system of the benzotriazole ring and hydroxyl group). After energy absorption, a rapid intramolecular proton transfer process occurs, converting light energy into heat energy and preventing photochemical bond breakage. Simultaneously, the hindered amine light stabilizer component (mainly tetramethylpiperidine derivatives) does not directly absorb UV light, but reacts with alkoxy radicals generated in the early stages of photooxidation to form stable imine oxides. These imine oxides can continuously capture polymer free radicals, blocking the photooxidation chain reaction. This cascade protection mechanism of "excited-state quenching-free radical scavenging" achieves end-to-end blocking of the photochemical degradation process. Most importantly, this invention solves the problems of easy migration and volatility of traditional light stabilizers by forming covalent bonds between 2-(2-hydroxy-5-methylphenyl)benzotriazole molecules and the resin network, thus ensuring the long-term stability of the protective effect.

[0019] Furthermore, in this invention, the fluorinated prepolymer serves as the basic framework of the entire system, providing not only excellent surface leveling properties but also significantly enhancing the moisture resistance after film formation due to its highly hydrophobic characteristics, reducing the leaching effect of moisture on the light stabilizer. The chemical stability of the fluorinated segments simultaneously improves the material's resistance to oxidation, synergistically enhancing the anti-aging effect. The dual-network crosslinking structure and the fluorinated system form a structure-performance complementarity. The surface orientation of the fluorinated segments improves the ink's leveling properties, ensuring uniform coating; while the low shrinkage stress controlled by the dual-network structure ensures the structural stability after film formation. This synergistic effect of "rheological optimization-stress control" fundamentally solves the adaptability problem of traditional solder resist inks on complex circuits. The anti-aging system, through precise molecular-level design, is embedded in the dual-network structure to form a durable protective barrier. The presence of the anti-aging component also unexpectedly improves the curing kinetics. The amine groups in the hindered amine light stabilizer can moderately regulate the free radical polymerization rate, making the network formation process more uniform and further reducing the accumulation of internal stress.

[0020] The advantage of this invention lies in combining fluorine migration thermodynamics, network topology, and excited-state quenching depth to achieve triple optimization of "surface-bulk-durability" at the molecular level, providing a solid material foundation for the manufacture of high-reliability printed circuit boards (PCBs). Attached Figure Description

[0021] Figure 1 This is a graph showing the fluorine / total fluorine ratio at different depths in the sample of Example 1; Figure 2 The results show the cross-sectional microstructure and elemental distribution characterization of the sample from Example 1. Detailed Implementation

[0022] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0023] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0024] Unless otherwise specified, the formulation of solder resist black used in the embodiments and comparative examples of this invention is as follows: 50 g of photosensitive resin, 1 g of photoinitiator TOP, 5 g of melamine, 10 g of titanium dioxide, 5 g of pentaerythritol triacrylate, 27 g of tetramethylbenzene, 1 g of defoamer, and 1 g of leveling agent prepared in the current embodiment or comparative example.

[0025] Example 1: A method for preparing a high-photosensitive resin for PCB solder resist ink. The method includes: 1) Mix hexafluorobutyl methacrylate, hydroxyethyl acrylate and styrene in a mass ratio of 1:0.9:0.2. Add 40 wt% azobisisobutyronitrile (AIBN) of the butyl acrylate compound under a nitrogen atmosphere and a temperature of 63 °C. React for 6 h to prepare an acrylic prepolymer. 2) The prepolymer was mixed with 25 wt% of pentaerythritol hexaacrylate and 0.05 wt% of hydroquinone polymerization inhibitor, and the mixture was reacted for 4 h at 65 ℃ to carry out functional modification and prepare the initially modified prepolymer. 3) Add 3 wt% of the modified prepolymer's composite stabilizer to the primary modified prepolymer and disperse it at 50 ℃ for 60 min to optimize stability. The composite stabilizer is a mixture of hindered amine light stabilizer and benzotriazole UV absorber (UV-326) at a mass ratio of 2:1. After stability optimization, use the mixed solution at 23 ℃ and stir for 60 min to adjust the solid content to 63% and the viscosity to 4500 cps. The mixed solution is a mixture of propylene glycol methyl ether acetate and cyclohexanone at a mass ratio of 3:1 to prepare a high photosensitive resin for PCB solder resist ink.

[0026] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0027] Surface tension testing: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. Referring to the testing method in ASTM D1331, the surface tension and leveling properties were determined using the dynamic Wilhelmy plate method. The test was conducted using a tensiometer with a platinum plate measuring 20 × 10 × 0.1 mm, at a test rate of 10 mm / min. During data acquisition, the dynamic contact angle change was monitored from 0 to 30 seconds, and the surface tension of the test sample was evaluated by calculating the spreading rate.

[0028] Curing shrinkage rate test: The material prepared in this example was used to prepare solder resist ink according to the existing solder resist ink formulation. Referring to the test method in "Determination of Total Volume Shrinkage of Unsaturated Polyester and Epoxy Resin", the ink was tested at a temperature of 25 ℃, a wavelength of 365 nm, and a power of 100 mW / cm². 2 Energy density 1000 mJ / cm³ 2 Testing was conducted using a UV curing machine under light-protected conditions.

[0029] Copper-based coverage: Copper-based coverage was evaluated according to "Qualification and Performance of Permanent Solder Masks". A 50 μm stepped copper substrate was used as the test substrate. Solder mask ink was prepared according to existing formulations, and a 25 μm thick layer of solder mask ink was applied to cover the surface of the test substrate. After standing for 2 hours, the coverage was calculated using a formula to quantitatively characterize the material's coverage effectiveness on the copper steps.

[0030] UV aging resistance testing: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. A 50 μm stepped copper substrate was used as the test substrate, and a 25 μm thick solder resist ink layer was applied to the surface of the test substrate. The solder resist ink was applied at 0.76 W / m². 2 Irradiation with a 340nm UVB-313 lamp, followed by a cycle of 4 hours of UV irradiation at 60℃ and then 4 hours of condensation at 50℃. The yellowing index was measured and calculated using a colorimeter under standard conditions of D65 light source and 10° viewing angle.

[0031] Thermal cycling test: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. A 50μm stepped copper substrate was used as the test substrate, and a 25μm thick layer of solder resist ink was applied to the surface of the test substrate. A three-chamber thermal shock chamber was used for thermal cycling testing, with a temperature range of -55 to 125 °C. Each temperature endpoint was held for 10 minutes, with a transition time of less than 10 seconds, for a total of 2500 cycles. Crack detection and analysis were performed after the test, with the criterion set as more than 5 cracks per unit area / cm². 2 This is considered invalid.

[0032]

[0033] Analysis of the characterization results shows that the high-sensitivity resin prepared in Example 1 exhibits excellent performance in three key dimensions: interfacial properties, crosslinking network characteristics, and environmental stability. This resin system exhibits a low surface tension of 27.3 mN / m, lower than traditional systems. This significant improvement stems from the directional enrichment of fluorinated segments provided by hexafluorobutyl methacrylate at the gas-liquid interface, indicating the formation of a highly homogeneous surface structure. The low surface tension directly improves the wetting and spreading behavior of the resin on substrates with high topological complexity, achieving a copper coverage of 95.7%. Uniform coverage is maintained, especially at line corners and areas with high copper thickness, without typical "backflow pitting" defects at the edges. This excellent coverage performance is attributed to the reduced surface tension gradient effect of the fluorinated groups, effectively suppressing uneven edge coating caused by flow. The resin system exhibits a low curing shrinkage rate of 3.2%, lower than traditional single-network systems. This significant shrinkage control originates from the "rigid-flexible" dual-network structure constructed by dipentaerythritol hexaacrylate and the flexible acrylic backbone. This dual-phase microstructure achieves stress dispersion and buffering at the molecular scale, enabling efficient release of thermal cycling stress. At the same time, the dual-network structure can effectively absorb deformation energy through molecular chain conformation adjustment. This characteristic directly explains its excellent performance of no microcracks after 1000 thermal cycles.

[0034] After accelerated UV aging testing, the resin maintained an extremely low yellowing index and excellent mechanical integrity. This superior anti-aging property stems from the multi-protective system formed by the hindered amine light stabilizer and benzotriazole. Notably, after 4000 hours of UV aging, the surface hardness change rate was only 8%, indicating that the resin network did not undergo significant post-crosslinking hardening or severe degradation and softening, verifying the comprehensive protective effect of the synergistic anti-aging system on the network structure.

[0035] In addition, the fluorine distribution of the PCB solder resist ink prepared in this example after curing with a high-sensitivity resin was characterized. Samples were sent to a third-party professional characterization and testing institution. The material prepared in this example was used to prepare solder resist ink according to existing solder resist ink formulations. A 50 μm stepped copper substrate was used as the test substrate, and a 25 μm thick layer of solder resist ink was applied to the surface of the test substrate. The coating cross-section was used for microscopic morphology characterization and the distribution of C, H, and F elements. SIMS was used to characterize the percentage of fluorine content in different depth ranges relative to the total fluorine content (not the atomic percentage of all elements, but only the percentage of fluorine in the original high-sensitivity resin, calculated from the depth profile results). The characterization results are as follows: Figure 1 and Figure 2As shown, the characterization results indicate that after the high photosensitive resin prepared in this example is used in the solder resist ink system and cured on the surface of the PCB circuit board, the cured layer surface covers approximately 90 at% fluorine within a depth of 0.5 μm, and almost all of the fluorine is fixed within a depth of 5 μm. This demonstrates that the special system constructed in this invention has a very significant regulatory effect on fluorine distribution, which can effectively limit the inward diffusion of fluorine, achieve surface enrichment of fluorine, maximize the utilization of the advantages of fluorine monomers, and avoid the potential corrosive damage to the PCB circuit board caused by the introduction of fluorine.

[0036] Furthermore, the performance of the high photosensitive resin prepared in this example was characterized. A 50 μm stepped copper substrate was used as the test substrate, and a 25 μm thick layer of solder resist ink from this example was applied to the surface of the test substrate. After curing, the high-frequency loss at 10 GHz was characterized, and the characterization results were compared with those of the control group ink and commercially available ink.

[0037] Control group ink formulation: 50 g of commercially available NPPN-272H photosensitive resin, 1 g of photoinitiator TOP, 5 g of melamine, 10 g of titanium dioxide, 5 g of pentaerythritol triacrylate, 27 g of tetramethylbenzene, 1 g of defoamer, and 1 g of leveling agent; Commercially available high-frequency ink grade: PSR-4000.

[0038] The characterization results are shown in the table below.

[0039]

[0040] The results in the table show that the high-sensitivity resin prepared in this example can effectively improve the overall performance of the solder resist ink under high-frequency conditions. This is mainly because the introduction of fluorine can effectively reduce the dielectric constant and signal loss, and suppress potential copper ion migration caused by environmental factors. It achieves or even slightly surpasses the performance of conventional high-frequency PCB solder resist inks.

[0041] Example 2: A method for preparing a high-photosensitive resin for PCB solder resist ink. The method includes: 1) Mix hexafluorobutyl methacrylate, hydroxyethyl acrylate and styrene in a mass ratio of 1:1.2:0.3. Add 40 wt% azobisisobutyronitrile (AIBN) of the butyl acrylate compound under a nitrogen atmosphere and a temperature of 65 °C. React for 5.5 h to prepare an acrylic prepolymer. 2) The prepolymer was mixed with 30 wt% of pentaerythritol hexaacrylate and 0.04 wt% of hydroquinone polymerization inhibitor, and the mixture was reacted for 3.5 h at 70 ℃ to carry out functional modification and prepare the initially modified prepolymer. 3) Add 3.5 wt% of the modified prepolymer's composite stabilizer to the primary modified prepolymer and disperse it at 55 ℃ for 45 min to optimize stability. The composite stabilizer is a mixture of hindered amine light stabilizer and benzotriazole UV absorber (UV-326) at a mass ratio of 2:1. After stability optimization, use the mixed solution at 25 ℃ and stir for 45 min to adjust the solid content to 65% and the viscosity to 5000 cps. The mixed solution is a mixture of propylene glycol methyl ether acetate and cyclohexanone at a mass ratio of 3:1 to prepare a high photosensitive resin for PCB solder resist ink.

[0042] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0043] Surface tension testing: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. Referring to the testing method in ASTM D1331, the surface tension and leveling properties were determined using the dynamic Wilhelmy plate method. The test was conducted using a tensiometer with a platinum plate measuring 20 × 10 × 0.1 mm, at a test rate of 10 mm / min. During data acquisition, the dynamic contact angle change was monitored from 0 to 30 seconds, and the surface tension of the test sample was evaluated by calculating the spreading rate.

[0044] Curing shrinkage rate test: The material prepared in this example was used to prepare solder resist ink according to the existing solder resist ink formulation. Referring to the test method in "Determination of Total Volume Shrinkage of Unsaturated Polyester and Epoxy Resin", the ink was tested at a temperature of 25 ℃, a wavelength of 365 nm, and a power of 100 mW / cm². 2 Energy density 1000 mJ / cm³ 2 Testing was conducted using a UV curing machine under light-protected conditions.

[0045] Copper-based coverage: Copper-based coverage was evaluated according to "Qualification and Performance of Permanent Solder Masks". A 50 μm stepped copper substrate was used as the test substrate. Solder mask ink was prepared according to existing formulations, and a 25 μm thick layer of solder mask ink was applied to cover the surface of the test substrate. After standing for 2 hours, the coverage was calculated using a formula to quantitatively characterize the material's coverage effectiveness on the copper steps.

[0046] UV aging resistance testing: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. A 50 μm stepped copper substrate was used as the test substrate, and a 25 μm thick solder resist ink layer was applied to the surface of the test substrate. The solder resist ink was applied at 0.76 W / m². 2Irradiation with a 340nm UVB-313 lamp, followed by a cycle of 4 hours of UV irradiation at 60℃ and then 4 hours of condensation at 50℃. The yellowing index was measured and calculated using a colorimeter under standard conditions of D65 light source and 10° viewing angle.

[0047] Thermal cycling test: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. A 50μm stepped copper substrate was used as the test substrate, and a 25μm thick layer of solder resist ink was applied to the surface of the test substrate. A three-chamber thermal shock chamber was used for thermal cycling testing, with a temperature range of -55 to 125 °C. Each temperature endpoint was held for 30 minutes, with a transition time of less than 10 seconds, for a total of 2500 cycles. Crack detection and analysis were performed after the test, with the criterion set as more than 5 cracks per unit area / cm². 2 This is considered invalid.

[0048]

[0049] Analysis of the characterization results shows that the highly photosensitive resin prepared in Example 2, through precise control of formulation and process, achieves optimization in three core dimensions: interfacial properties, cross-linked network structure, and environmental stability, exhibiting unique performance characteristics. The fine-tuning of the interfacial structure and the improvement in rheological properties are further reduced compared to Example 1. This improvement stems from the optimized directional arrangement of fluorinated segments at the interface. Simultaneously, the surface energy distribution is more uniform, and the droplet spreading behavior is more ideal. This change in interfacial structure directly optimizes the rheological properties of the photosensitive resin, which is beneficial for wetting and spreading in areas with high copper thickness and improves the microstructure filling capacity.

[0050] Example 2 exhibits a low curing shrinkage rate of 2.7%, a further reduction compared to Example 1. This optimization stems from fine-tuning of the monomer ratio and initiation system. By increasing the ratio of dipentaerythritol hexaacrylate to flexible monomers, and introducing a small amount of siloxane-modified acrylate as a stress buffer component, the crosslinking network structure is fine-tuned, which is beneficial for releasing internal stress. In particular, the curing kinetics of Example 2 exhibit a "slow start-fast finish" characteristic: the time required to reach a curing conversion rate of 10% is prolonged, but the total time to reach a 90% conversion rate is shortened. This kinetic characteristic makes the network formation process more controllable, avoids stress accumulation in the early curing stage, ensures production efficiency, reduces the internal stress of the material after film formation, increases the critical fracture strain, and significantly improves structural stability while maintaining a considerable copper-based coverage.

[0051] In addition, the fluorine distribution of the PCB circuit board solder resist ink prepared in this example after curing with the high photosensitive resin was characterized in the same way as in Example 1, and the performance of the high photosensitive resin prepared in this example was characterized.

[0052] The results are shown in the table below.

[0053]

[0054] Based on the above characterization results, the high photosensitive resin prepared in this example also has good fluorine distribution properties and good applicability to high-frequency solder resist inks.

[0055] Example 3: A method for preparing a high-photosensitive resin for PCB solder resist ink. The method includes: 1) Mix hexafluorobutyl methacrylate, hydroxyethyl acrylate and styrene in a mass ratio of 1:1.4:0.4. Add 40 wt% azobisisobutyronitrile (AIBN) of the butyl acrylate compound under a nitrogen atmosphere and a temperature of 67 °C. React for 5 h to prepare an acrylic prepolymer. 2) The prepolymer was mixed with 35 wt% of pentaerythritol hexaacrylate and 0.05 wt% of hydroquinone polymerization inhibitor, and the mixture was reacted for 3 h at 75 ℃ to carry out functional modification and prepare the initially modified prepolymer. 3) Add 4 wt% of the modified prepolymer's composite stabilizer to the primary modified prepolymer and disperse it at 60 ℃ for 30 min to optimize stability. The composite stabilizer is a mixture of hindered amine light stabilizer and benzotriazole UV absorber (UV-326) at a mass ratio of 2:1. After stability optimization, use the mixed solution at 27 ℃ and stir for 30 min to adjust the solid content to 67% and the viscosity to 5500 cps. The mixed solution is a mixture of propylene glycol methyl ether acetate and cyclohexanone at a mass ratio of 3:1.1 to prepare a high photosensitive resin for PCB solder resist ink.

[0056] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0057] Surface tension testing: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. Referring to the testing method in ASTM D1331, the surface tension and leveling properties were determined using the dynamic Wilhelmy plate method. The test was conducted using a tensiometer with a platinum plate measuring 20 × 10 × 0.1 mm, at a test rate of 10 mm / min. During data acquisition, the dynamic contact angle change was monitored from 0 to 30 seconds, and the surface tension of the test sample was evaluated by calculating the spreading rate.

[0058] Curing shrinkage rate test: The material prepared in this example was used to prepare solder resist ink according to the existing solder resist ink formulation. Referring to the test method in "Determination of Total Volume Shrinkage of Unsaturated Polyester and Epoxy Resin", the ink was tested at a temperature of 25 ℃, a wavelength of 365 nm, and a power of 100 mW / cm². 2 Energy density 1000 mJ / cm³ 2 Testing was conducted using a UV curing machine under light-protected conditions.

[0059] Copper-based coverage: Copper-based coverage was evaluated according to "Qualification and Performance of Permanent Solder Masks". A 50 μm stepped copper substrate was used as the test substrate. Solder mask ink was prepared according to existing formulations, and a 25 μm thick layer of solder mask ink was applied to cover the surface of the test substrate. After standing for 2 hours, the coverage was calculated using a formula to quantitatively characterize the material's coverage effectiveness on the copper steps.

[0060] UV aging resistance testing: The material prepared in this example was formulated into a solder resist ink according to existing solder resist ink formulations. A 50 μm stepped copper substrate was used as the test substrate, and a 25 μm thick solder resist ink layer was applied to the surface of the test substrate. The solder resist ink was applied at 0.76 W / m². 2 Irradiation with a 340nm UVB-313 lamp, followed by a cycle of 4 hours of UV irradiation at 60℃ and then 4 hours of condensation at 50℃. The yellowing index was measured and calculated using a colorimeter under standard conditions of D65 light source and 10° viewing angle.

[0061] Thermal cycling test: The material prepared in this example was formulated into solder resist ink according to existing solder resist ink formulations. A 50μm stepped copper substrate was used as the test substrate. The surface of the test substrate was covered with a 25μm thick layer of solder resist ink. Thermal cycling test was conducted using a three-chamber thermal shock chamber with a temperature range of -55 to 125 ℃. The holding time at each temperature endpoint was 30 min, and the transition time was less than 10 s. A total of 2500 cycles were completed. After the test, crack detection and analysis were performed. The judgment criterion was set as more than 5 cracks / cm2 per unit area, which was considered as failure.

[0062]

[0063] Analyzing the above characterization results, the high-photosensitivity resin prepared in Example 3, through further adjustments to the monomer ratio and process conditions, exhibits more balanced overall performance compared to Example 2, while maintaining excellent fluorine distribution and high-frequency performance. Specifically, the surface tension was slightly reduced to 26.0 mN / m, a fine adjustment that facilitates the wetting and spreading of solder resist ink on fine lines, improving printing accuracy. The curing shrinkage rate remained at 1.5%, indicating minimal volume change during curing, which helps maintain the dimensional stability of the circuit board. The copper-based coverage reached 99.4%, ensuring sufficient protection of the copper lines by the solder resist layer and avoiding the risk of short circuits. UV aging test results showed a yellowing index of 1.6, indicating that the material maintains good color stability under prolonged UV irradiation, meeting the application requirements in outdoor or high-light-intensity environments. In thermal cycling tests, after 2500 cycles of extreme temperature changes from -55 to 125 °C, no cracking occurred on the material surface, verifying its excellent temperature resistance and structural stability.

[0064] In addition, the fluorine distribution of the PCB circuit board solder resist ink prepared in this example after curing with the high photosensitive resin was characterized in the same way as in Example 1, and the performance of the high photosensitive resin prepared in this example was characterized.

[0065] The results are shown in the table below.

[0066]

[0067] The characterization results show that the high-sensitivity resin prepared in this example also exhibits good fluorine distribution and excellent applicability to high-frequency solder resist inks. This invention utilizes precise fluorine distribution control technology to construct a gradient fluorine concentration distribution structure, achieving systematic optimization of high-frequency signal transmission performance. The cured resin forms a highly ordered gradient fluorine concentration distribution: fluorine atoms account for over 90% in the surface 0.5 μm region, forming a dense fluorine-rich layer; within a depth of 5 μm, the fluorine fixation rate reaches over 98%, indicating that fluorine atoms form stable chemical bonds with the polymer matrix. This gradient distribution is not a simple physical segregation, but rather an ordered structure formed by the directional migration and selective cross-linking of fluorinated monomers during the curing process. The fluorine-rich surface region is mainly composed of -CF3 and -CF2- groups, forming a stable covalent bond structure. This surface fluorine enrichment not only provides excellent hydrophobicity but, more importantly, creates an effective fluorine diffusion barrier layer, preventing fluorine atoms from migrating deeper into the substrate.

[0068] The core of the fluorine migration suppression mechanism lies in the dual physical and chemical barrier of the fluorine-rich surface region against fluorine atom diffusion. The high fluorine concentration on the surface creates a concentration gradient resistance for inward diffusion, and the diffusion flux is proportional to the concentration gradient. The high surface concentration effectively reduces the net inward diffusion driving force, and the large-volume steric hindrance effect of the -CF3 group significantly increases the activation energy of fluorine atom migration, resulting in a lower diffusion coefficient compared to free fluoride ions. More importantly, the fluorine-rich surface layer blocks the diffusion path of fluorine to the PCB copper layer, preventing direct contact and reaction between fluorine and copper. Under high temperature and high humidity conditions, free fluoride ions readily react with copper to form copper fluoride. This compound has a certain degree of conductivity and forms a conductive path in the medium, significantly increasing dielectric loss. By suppressing fluorine migration, this invention eliminates this loss mechanism at its source.

[0069] The optimization of dielectric properties by surface -CF3 groups is based on their unique molecular polarity. Although CF bonds have large bond dipole moments, the symmetry of the -CF3 groups makes the total molecular dipole moment close to zero, exhibiting low polarity. This low polarity directly reduces the dielectric constant of the material. On the other hand, the large volume of the -CF3 groups and the strong CF bonds restrict the thermal motion of molecular chain segments, reducing the orientation polarization of dipoles under alternating electric fields.

[0070] Furthermore, a quantitative relationship between fluorine distribution depth and high-frequency signal loss was established through control experiments: when the fluorine distribution depth increased by 10%, the signal loss at 10 GHz increased by 0.03 dB / 10 mm. This correlation reflects the sensitive influence of fluorine distribution uniformity on dielectric properties. Increased depth of fluorine distribution implies a relative decrease in surface fluorine concentration, weakening the dielectric optimization effect of the surface layer. Optimal fluorine distribution should confine more than 90% of fluorine atoms within a 1 μm range on the surface. This distribution maximizes surface dielectric properties while avoiding the negative impact of deep fluorine distribution on the matrix's mechanical properties. When the fluorine-rich layer (90 at%) distribution depth exceeds the critical value (approximately 2 μm), the glass transition temperature of the material begins to decrease, and thermal stability is affected.

[0071] Comparative Example 1: Based on Example 2, this example only modifies the preparation process of the acrylic acid prepolymer; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0072] The performance testing methods for the products of Comparative Examples D1-1 and D1-2 are completely consistent with those of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0073]

[0074] Analysis of the characterization results shows that, compared to Example 2, replacing the fluorinated monomer hexafluorobutyl methacrylate with methyl methacrylate in D1-1 resulted in a significant increase in surface tension and a substantial rise in curing shrinkage, while the copper coverage decreased significantly. These performance degradations indicate that the type of fluorinated monomer has a significant impact on the performance of highly photosensitive resins, and the introduction of hexafluorobutyl methacrylate is crucial for optimizing the material's wettability, dimensional stability, and circuit protection capabilities.

[0075] In D1-2, reducing the amount of the fluorinated monomer hexafluorobutyl methacrylate to 50% of that in Example 2 resulted in increased surface tension, maintained high curing shrinkage, and decreased copper coverage. Furthermore, this sample exhibited coating peeling during thermal cycling testing, indicating that the reduction in fluorinated monomer content significantly impacted the material's thermal stability and adhesion. This result further emphasizes the importance of fluorinated monomers in highly photosensitive resins; an appropriate amount of fluorinated monomer is crucial for maintaining the overall performance of the material.

[0076] In addition, the fluorine distribution of the PCB circuit board solder resist ink prepared by D1-3 after curing with high photosensitive resin was characterized in the same way as in Example 1, and the performance of the high photosensitive resin prepared in this example was characterized.

[0077] The results are shown in the table below.

[0078]

[0079] The characterization results above reveal the crucial role of fluorinated monomer molecular design in high-frequency dielectric materials, demonstrating a precise structure-property relationship from molecular structure to macroscopic properties. High-performance fluorinated monomer molecular design requires meeting two key structural requirements: sufficiently long fluorocarbon segments and specific end-group configurations. Hexafluorobutyl segments (≥C4) provide the critical surface energy difference for achieving surface enrichment, based on the unique surface chemistry of fluorocarbon compounds. The surface energy of perfluoroalkyl chains is significantly lower than that of ordinary organic polymers; this substantial surface energy difference is the thermodynamic driving force propelling the migration of fluorinated segments to the gas-solid interface.

[0080] The trifluoroethyl ester (C2 short chain) used in groups D1-3 has a surface energy of about 15 mN / m, which is relatively small compared to the surface energy difference of the polymer matrix. Compared with hexafluorobutyl, the difference is significantly insufficient. The driving force for surface enrichment is proportional to the square of the surface energy difference. The small surface energy difference reduces the driving force for fluorine migration, making it impossible to achieve effective surface enrichment.

[0081] In this invention, the -CF3 end group plays a crucial role in molecular orientation during surface enrichment. The CF3 group has an approximately spherical symmetrical structure with a total molecular dipole moment close to zero. When it forms a vertically oriented arrangement on the surface, it can maximize the reduction of surface energy. The -CF3 end group tends to be vertically oriented at the gas-solid interface, with fluorine atoms pointing towards the gas phase, forming an ordered monolayer structure.

[0082] In contrast, the -CF2H end group in D1-3 has a significant dipole moment, disrupting the symmetry and orientation of the molecule. The -CF2H group exhibits random orientation at the interface, failing to form a dense fluorine-enriched layer. This significant difference in orientation efficiency directly leads to a decrease in the surface fluorine enrichment rate, weakening the surface dielectric optimization effect.

[0083] The decreased surface enrichment capacity leads to more fluorine atoms diffusing deeper into the substrate, eventually reaching the copper interface and undergoing a chemical reaction. The reaction between free fluoride ions and copper follows an electrochemical mechanism, forming copper fluoride with semiconductor properties. This conductive phase forms microscopic conductive pathways in the dielectric, generating additional conduction losses under high-frequency electric fields. The formation of copper fluoride also weakens the bonding strength at the copper-dielectric interface. The thermal expansion coefficient of the CuF2 layer differs significantly from that of copper and the polymer, generating interfacial stress during thermal cycling and leading to microcrack formation. The copper-dielectric interface of sample D1-3 exhibits obvious delamination, with a lower interfacial bonding strength than the optimized sample, showing coating blistering and even peeling during thermal cycling tests.

[0084] The fundamental reason for the sharp increase in high-frequency loss in the D1-3 group lies in the superimposed effect of multiple loss mechanisms: First, insufficient fluorine enrichment on the surface increases the dielectric constant, thus increasing polarization loss; second, the copper fluoride conductive layer introduces conduction loss, increasing the loss factor by approximately 0.005 at 10 GHz; finally, scattering loss caused by interfacial microcracks further deteriorates high-frequency performance. The D1-3 samples exhibit significant impedance discontinuities at high frequencies, with a higher reflection coefficient than the optimized samples. This impedance mismatch not only increases signal loss but may also cause signal integrity problems, such as intersymbol interference and timing shifts.

[0085] Comparative Example 2: Based on Example 2, this example only modifies the functional modification process of the acrylic prepolymer; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0086] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0087]

[0088] Analysis of the characterization results reveals that the dual-network structure plays a crucial role in fluorine diffusion control and coating stability maintenance, elucidating the cascade failure mechanism caused by network structure defects at the molecular level. The absence of the rigid network directly leads to the collapse of the molecular-level diffusion barrier, allowing fluorine atoms to migrate deeper into the substrate. Dipentaerythritol hexaacrylate, as a hexafunctional crosslinking agent, forms a highly branched three-dimensional cage-like structure during polymerization, with crosslinking point spacing of approximately 3–5 nm, effectively restricting the free diffusion of fluorine atoms. When the rigid network is absent, this cage-like constraint structure collapses into a continuous channel, resulting in an order-of-magnitude increase in the fluorine diffusion coefficient and a diffusion capacity enhancement of approximately two orders of magnitude. The fluorine content at a depth of 0.5 μm is significantly reduced in all comparative groups, and the surface enrichment effect essentially disappears. This homogenization of fluorine distribution disrupts the gradient concentration structure, causing the surface layer to lose its advantages of low dielectric constant and hydrophobicity, while simultaneously creating conditions for fluorine diffusion to the copper interface.

[0089] The flexible acrylic chain-based elastic network in the dual-network system serves a dual function of stress buffering and space filling. These long-chain molecules form physical entanglements with the rigid network through side groups, creating an elastic filling phase in the gaps of the cage-like structure. When the single-network structure cannot provide sufficient stress buffering, the curing shrinkage rate increases significantly, and the internal stress accumulates at the interface to reach a critical value, ultimately leading to the failure of the coating adhesion to the substrate. The storage modulus of the single-network system drops sharply in the glass transition region, lacking the wide plateau region characteristic of the dual-network system. This discontinuity in mechanical properties prevents the material from effectively releasing stress during thermal cycling, resulting in interfacial cracking and coating peeling.

[0090] When fluorine atoms penetrate to the copper interface, an electrochemical corrosion reaction is initiated under humid and hot conditions. Fluorine ions, acting as strong ligands, form stable complexes with copper ions, promoting the anodic dissolution of copper, followed by Cu... 2+ With F - The process involves the formation of CuF2 precipitate. This electrochemical process not only consumes metallic copper at the interface but also forms a loose and porous corrosion product layer at the interface, severely weakening the mechanical bond between the coating and the substrate. The corrosion interface exhibits a typical pitting morphology, with pits reaching depths of several micrometers. These defects become stress concentration points, which rapidly expand under external forces, ultimately leading to large-area peeling of the coating.

[0091] Group D2-1 used monofunctional isobornyl acrylate instead of dipentaerythritol hexaacrylate, significantly altering the topology of the crosslinked network. The introduction of the monofunctional monomer led to a substantial decrease in crosslinking density, a looser network structure, and a sharp increase in curing shrinkage. The looser network structure provided larger channels for fluorine atom migration, significantly reducing the surface fluorine enrichment efficiency and decreasing the fluorine content at a depth of 0.5 μm. The deterioration of fluorine distribution resulted in decreased dielectric properties, with signal loss at 10 GHz increasing to 0.57 dB / 10 mm. More seriously, the lack of network rigidity caused the coating to peel off during thermal cycling tests, rendering it ineffective.

[0092] Group D2-2 attempted to balance crosslinking density and curing shrinkage by adjusting the amount of dipentaerythritol hexaacrylate added. However, although the curing shrinkage decreased, the surface enrichment effect of fluorine was still unsatisfactory, with a fluorine content of 79.8 at% at a depth of 0.5 μm. This insufficient fluorine distribution also led to increased high-frequency signal loss and coating peeling during thermal cycling tests.

[0093] Group D2-3 used pentaerythritol triacrylate instead of dipentaerythritol hexaacrylate to introduce a moderate crosslinking density while maintaining network rigidity. However, this modification did not significantly improve the surface enrichment of fluorine; the fluorine content at a depth of 0.5 μm was 76.8 at%, and the high-frequency signal loss was 0.52 dB / 10 mm. Similarly, slight blistering of the coating occurred during thermal cycling tests, indicating insufficient rigidity of the network structure and its inability to effectively resist the accumulation of internal stress.

[0094] Comparative Example 3: Based on Example 2, this example only modifies the stability optimization process of the initially modified prepolymer; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0095] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0096]

[0097] Analysis of the characterization results shows that the D3-1 group did not undergo stability optimization of the initially modified prepolymer, resulting in a slight increase in surface tension and curing shrinkage, but these remained within acceptable limits. Although the coverage and yellowing index decreased, the thermal cycling stability was unaffected, which may be related to the inherent stability of the initially modified prepolymer itself. However, long-term stability still needs further verification.

[0098] Group D3-2, using only hindered amine light stabilizers instead of composite stabilizers, showed little change in surface tension, but a significant reduction in the yellowing index, indicating that hindered amine light stabilizers have a certain effect in resisting photoaging. However, the trends in curing shrinkage and coverage were similar to those of Group D3-1, and the coating blistered slightly during the thermal cycling stability test, suggesting that using hindered amine light stabilizers alone is insufficient to provide comprehensive stability assurance.

[0099] Group D3-3, using only a benzotriazole UV absorber (UV-326) to replace the composite stabilizer, showed similar trends in surface tension, curing shrinkage, and coverage as groups D3-1 and D3-2. Although the yellowing index was improved compared to group D3-1, it remained higher than in Example 2, and slight blistering of the coating was also observed during thermal cycling stability testing. This indicates that while benzotriazole UV absorbers have some effect in resisting UV aging, they cannot provide comprehensive stability assurance.

[0100] The stability optimization process of initially modified prepolymers has a significant impact on the overall performance of the material. The use of composite stabilizers can comprehensively improve the weather resistance, thermal stability, and chemical stability of the material, while using a single stabilizer often fails to achieve the desired effect. Therefore, the selection and combination of stability optimization processes should be fully considered in material design to ensure the long-term stability and reliability of the material.

Claims

1. A method for preparing a high-photosensitive resin for PCB solder resist ink, characterized in that, The method includes: 1) Prepare an acrylic acid prepolymer by uniformly mixing butyl ester compounds, acid ester compounds, and aromatic hydrocarbons in a certain proportion; 2) Functionally modify the acrylic prepolymer to prepare a prepolymer with initial modification; 3) The stability of the modified prepolymer was optimized to prepare a high photosensitive resin for PCB solder resist ink.

2. The method for preparing a high-photosensitive resin for PCB solder resist ink according to claim 1, characterized in that, Step 1) The butyl ester compound is hexafluorobutyl methacrylate; Step 1) The ester compound is hydroxyethyl acrylate; Step 1) The aromatic hydrocarbon is styrene; In step 1), the butyl ester compounds, acid ester compounds, and aromatic hydrocarbons are mixed evenly at a mass ratio of 1:(0.9-1.4):(0.2-0.4).

3. A method for preparing a high-photosensitive resin for PCB circuit board solder resist ink according to claim 1 or 2, characterized in that, Step 1) The acrylic prepolymer is prepared by adding 40 wt% of azobisisobutyronitrile (AIBN) to a uniformly mixed mixture of butyl ester compounds, acid ester compounds, and aromatic hydrocarbons under a nitrogen atmosphere and a temperature of 63–67 °C, and reacting for 5–6 h.

4. The method for preparing a high-photosensitive resin for PCB solder resist ink according to claim 1, characterized in that, Step 2) The specific operation of the functional modification is as follows: Add 25–35 wt% of dipentaerythritol hexaacrylate and 0.03–0.05 wt% of hydroquinone polymerization inhibitor to the prepolymer, and continue the reaction for 3–4 h at an ambient temperature of 65–75 °C.

5. The method for preparing a high-photosensitive resin for PCB solder resist ink according to claim 1, characterized in that, Step 3) The specific operation of stability optimization is as follows: Add 3-4 wt% of the composite stabilizer to the modified prepolymer and disperse it for 30-60 min at an ambient temperature of 50-60 ℃.

6. The method for preparing a high-photosensitive resin for PCB solder resist ink according to claim 5, characterized in that, The composite stabilizer is composed of a hindered amine light stabilizer and a benzotriazole ultraviolet absorber (UV-326) in a mass ratio of 2:

1.

7. A method for preparing a high-photosensitive resin for PCB solder resist ink according to claim 1, 5, or 6, characterized in that, Step 3) The high photosensitive resin used to prepare the PCB circuit board solder resist ink is: Add the mixed solution to the modified prepolymer mixture after stability optimization, stir for 30 to 60 min at an ambient temperature of 23 to 27 °C, and adjust the solid content to 63 to 67% and the viscosity to 4500 to 5500 cps.

8. The high photosensitive resin for PCB solder resist ink according to claim 7, characterized in that, The mixed solution is a homogeneous mixture of propylene glycol methyl ether acetate and cyclohexanone at a mass ratio of 3:(0.8-1.1).

9. A high photosensitive resin for PCB solder resist ink prepared by any one of claims 1 to 8.

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