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

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to high photosensitive resin for PCB circuit ink and a preparation method of the high photosensitive resin. The method comprises the following steps: 1) uniformly mixing an ester compound, an acid ester compound and polyphenol in proportion to prepare a premixed monomer; 2) mixing the composite photoinitiator and the premixed monomer in proportion, and stirring to prepare a precursor; 3) uniformly mixing the precursor and a carboxylic acid compound in proportion, and stirring to prepare an optimized base material; and 4) deaerating the optimized base material under reduced pressure, and filtering to prepare the high-photosensitive resin. According to the invention, a novel PCB circuit ink photosensitive resin system with high sensitivity, high resolution, excellent chemical resistance and excellent thermal mechanical properties is successfully developed through a multi-dimensional collaborative strategy of molecular structure design, photo-initiation system optimization, cross-linked network construction and process parameter control; and a key material support is provided for sustainable development of a high-density interconnection technology.

Description

Technical Field

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

[0002] The traditional photosensitive circuit inks currently used in PC manufacturing for businesses have dimensional performance limitations, severely hindering the development of high-density interconnect (HDI) technology. Analysis of molecular structure and photochemical reaction mechanisms reveals these limitations primarily at three key technical levels: First, traditional photosensitive resin systems generally suffer from insufficient photosensitivity. From the perspective of photopolymerization kinetics, their low quantum efficiency leads to insufficient free radical generation efficiency during projection exposure, resulting in significant attenuation of the photoinitiation effect. This defect directly limits the circuit imaging resolution to above 10 μm, making precise replication of micro-circuits impossible. With the increasing demands for circuit density in 5G mobile communications and advanced computing devices, reaching sub-5 μm levels, traditional photosensitive resins can no longer support the technological iteration of micro-circuit manufacturing processes.

[0003] Secondly, from the perspective of the physicochemical nature of polymers, traditional photosensitive resins suffer from microstructural defects due to uneven cross-linking networks. Their molecular weight distribution index generally exceeds 2.0, indicating significant differences in molecular chain length. This leads to uneven steric hindrance during the cross-linking reaction, resulting in a three-dimensional network structure with obvious defects. This uneven network structure directly affects the glass transition temperature and mechanical strength of the material, making it prone to softening and deformation during high-temperature reflow soldering processes, threatening circuit integrity and reliability. With the increasing integration of electronic devices and the rising process temperatures, this problem is becoming increasingly prominent.

[0004] Existing technologies have attempted to improve these properties by adding efficient photoinitiators or adjusting the acrylate monomer ratio. However, these single-dimensional optimization solutions fail to fundamentally address the insufficient synergistic effect among the components of the material system. According to structure-performance analysis, isolated improvements to a single component often lead to trade-offs and sacrifices in other properties; for example, increasing photosensitivity may reduce chemical resistance, while increasing crosslinking density may increase brittleness. Photosensitive resin systems lacking systematic and innovative design struggle to achieve overall performance improvements and cannot meet the multi-dimensional material requirements of next-generation PCB manufacturing technologies. Summary of the Invention

[0005] This invention addresses the technical challenges of insufficient photosensitivity and uneven cross-linking networks in traditional PCB circuit board inks by providing a high-photosensitivity resin and its preparation method.

[0006] The main objective of this invention is to achieve high photosensitivity through the synergistic effect of novel acrylate monomers and composite photoinitiators.

[0007] 2. A uniform crosslinking network is constructed using an epoxy acrylate crosslinking agent to improve chemical resistance.

[0008] 3. Optimize polymerization process parameters to ensure molecular weight distribution and enhance resin stability.

[0009] To achieve the above objectives, the present invention adopts the following technical solution.

[0010] A method for preparing a high-sensitivity resin for PCB circuit board ink, the method comprising: 1) mixing ester compounds, acid ester compounds and polyphenols in proportion to prepare a premixed monomer.

[0011] 2) Mix the composite photoinitiator and premixed monomer in a certain proportion and stir to prepare the precursor.

[0012] 3) Mix the precursor and carboxylic acid compound in a certain proportion and stir to prepare the optimized substrate.

[0013] 4) The optimized substrate is degassed under reduced pressure and filtered to produce a highly photosensitive resin.

[0014] Preferably, the ester compound in step 1) is glycidyl methacrylate.

[0015] Step 1) The ester compound is pentaerythritol triacrylate.

[0016] Step 1) The polyphenol is hydroquinone.

[0017] Step 1) The ester compounds, acid ester compounds and polyphenols are mixed evenly at a mass ratio of (2.8-3.2):1:(0.02-0.04).

[0018] Preferably, the preparation of the premixed monomer in step 1) is carried out by stirring for 20 to 40 minutes under nitrogen atmosphere, temperature of 35 to 45 °C and rotation speed of 400 to 600 rpm.

[0019] Preferably, the composite photoinitiator in step 2) is prepared by mixing ethyl 2,4,6-trimethylbenzoylphenylphosphonate and photoinitiator 819 at a mass ratio of 1:(1.8-2.2); the composite photoinitiator and the premixed monomer in step 2) are mixed uniformly at a mass ratio of (0.05-0.09):1.

[0020] Preferably, the stirring preparation in step 2) is carried out in an environment with a temperature of 23-27 ℃, a rotation speed of 300-500 rpm, and in the dark, for 20-40 min.

[0021] Preferably, the carboxylic acid compound in step 3) is an epoxy acrylate; the precursor and the carboxylic acid compound in step 3) are mixed evenly at a mass ratio of 1:(0.25~0.35).

[0022] Preferably, the stirring preparation in step 3) is carried out under environmental conditions of 58-62 ℃ and 400-600 rpm for 3-5 h.

[0023] Preferably, step 4) involves degassing under reduced pressure for 10 to 15 minutes at an ambient pressure of -0.3 to -0.1 MPa. Step 4) The filtration is performed using a 5-7 μm filter membrane.

[0024] A high-photosensitive resin for PCB circuit board ink.

[0025] The core of the technical solution of this invention lies in overcoming the technical obstacles of traditional PCB ink materials in the field of micro-line manufacturing through a four-dimensional integrated design strategy of monomer selection, initiation system, crosslinking agent design, and process control.

[0026] From a molecular design perspective, this invention uses glycidyl methacrylate as the key monomer, whose molecular structure simultaneously possesses epoxy groups and methacrylate double bonds, forming a unique bifunctional reaction center. The epoxy groups participate in the secondary crosslinking reaction, enhancing the stability of the network structure; while the α,β-unsaturated ester groups exhibit extremely high reactivity under photoinitiation conditions, significantly improving the photopolymerization kinetic efficiency. Simultaneously, pentaerythritol triacrylate is introduced as a multifunctional crosslinking monomer. Its three-dimensional structure forms a highly crosslinked network with three acrylate groups, effectively restricting molecular chain segment movement and improving the glass transition temperature and dimensional stability of the material. The synergistic effect of glycidyl methacrylate and pentaerythritol triacrylate establishes a uniform and dense three-dimensional network structure, avoiding the problem of uneven local crosslinking density commonly found in traditional systems.

[0027] In terms of photoinitiation system design, this invention constructs a composite photoinitiation system covering a wide spectral range. Ethyl 2,4,6-trimethylbenzoylphenylphosphonate is used as a highly efficient initiator in the short wavelength region, generating a high concentration of primary free radicals in a very short time, enabling rapid surface imaging. Simultaneously, bisacylphosphine photoinitiator 819 is introduced as a deep-curing accelerator. Its long-wavelength absorption characteristics and high penetration depth ensure uniform cross-linking of the thick film layer, effectively avoiding the delamination phenomenon of "overexposed surface, uncured interior." The synergistic effect of the two photoinitiators significantly improves light energy utilization and lowers the energy threshold required for photosensitivity, enabling the resin system to achieve complete curing under low-dose exposure conditions, providing a key material basis for the precise replication of sub-5 μm micro-circuits.

[0028] This invention further introduces epoxy acrylate as the backbone resin, whose molecular structure combines the chemical stability of epoxy resin with the high reactivity of acrylate. From the reaction mechanism analysis, the epoxy groups in the epoxy acrylate molecule undergo ring-opening in an alkaline developing environment to form stable ether bonds, rather than the easily hydrolyzed ester bonds in traditional polyurethanes, significantly improving the material's alkali resistance. Simultaneously, the acrylate functional groups participate in the free radical photopolymerization process, forming an interpenetrating network structure with glycidyl methacrylate and pentaerythritol triacrylate; the epoxy groups can also undergo ring-opening addition reactions with the hydroxyl groups in hydroxyethyl methacrylate, further enhancing the network's density and uniformity, and improving the material's mechanical strength and thermal stability.

[0029] In terms of process control, this invention establishes a precise reaction parameter system to ensure narrow-range control of the resin's molecular weight distribution. The reaction temperature is set at 58–62 °C, at which the ring-opening rate of epoxy groups and the free radical-initiated polymerization rate are balanced, effectively suppressing the prepolymer gelation phenomenon that easily occurs under high-temperature conditions. The reaction time is optimized to 3–5 h, ensuring sufficient reaction between the epoxy acrylate and the monomer while avoiding the broadening of the molecular weight distribution caused by excessively long reaction times. Through precise two-dimensional control of temperature and time, the molecular weight distribution index (PDI) of the resin is successfully controlled below 1.3, significantly better than traditional photosensitive resins (PDI>2.0), providing a microstructural basis for the uniform and stable performance of the material.

[0030] The advantages of this invention are: through a multi-dimensional synergistic strategy of molecular structure design, photoinitiation system optimization, cross-linking network construction and process parameter control, a novel PCB circuit ink photosensitive resin system with high photosensitivity, high resolution, excellent chemical resistance and superior thermomechanical properties has been successfully developed, providing key material support for the continued development of high-density interconnect technology. Detailed Implementation

[0031] The present invention will be further described clearly and in detail below with reference to specific embodiments. 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.

[0032] 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.

[0033] Example 1: A method for preparing a high photosensitive resin for PCB circuit board ink, the method comprising: 1) mixing glycidyl methacrylate, pentaerythritol triacrylate and hydroquinone in a mass ratio of 2.8:1:0.02, stirring for 40 min under nitrogen atmosphere, temperature of 35 ℃ and rotation speed of 400 rpm to prepare a premixed monomer.

[0034] 2) The composite photoinitiator and the premixed monomer were mixed evenly at a mass ratio of 0.05:1. The mixture was stirred for 40 min at a temperature of 23 ℃, a rotation speed of 300 rpm, and in the dark to prepare the precursor. The composite photoinitiator was prepared by mixing ethyl 2,4,6-trimethylbenzoylphenylphosphonate and photoinitiator 819 at a mass ratio of 1:1.8.

[0035] 3) The precursor and epoxy acrylate were mixed evenly at a mass ratio of 1:0.25 and stirred for 5 h at an ambient temperature of 58 ℃ and a rotation speed of 400 rpm to prepare the optimized substrate.

[0036] 4) The optimized substrate was degassed for 15 min under an environment with a pressure of -0.3 MPa, and then filtered using a 5 μm filter membrane to prepare a highly photosensitive resin.

[0037] The high photosensitivity resin prepared in this example was subjected to performance testing, and the specific characterization results are as follows: Photosensitivity test: The resin was coated on a copper substrate with a thickness of 18 μm, pre-baked at 80 ℃ for 10 min, and then passed through a photomask (resolution test pattern) with a gradient energy (10~100 mJ / cm²). 2 Expose the circuit, develop it, and observe its integrity. The minimum energy required for complete development without any residue is taken as the photosensitivity value.

[0038] Resolution detection: SEM linewidth measurement was used in conjunction with photolithography pattern transfer onto an 18 μm thick copper substrate. A KarlSuss MA6 mask alignment machine was used to perform secondary electron imaging under environmental conditions of 5 kV acceleration voltage and 8 mm working distance. Three points with the narrowest linewidth were measured at 100 μm intervals, and the average value was calculated.

[0039] Alkali resistance test: The resin prepared in the example was coated onto a glass substrate with a coating thickness of 20 μm to make a test sample. The test sample was immersed in 10% NaOH solution for 30 min. After removal, the surface condition was observed every 1 min. The adhesion was tested with a cross-cut tester. No peeling in the cross-cut area was considered qualified. The time when the resin film began to peel off was recorded.

[0040] Viscosity testing: At an environment of 25 °C, the viscosity was measured in 10 seconds. -1The shear rate was determined by using a Brookfield DV2T rotational viscometer, which was rotated for 30 seconds to obtain the viscosity value. This process was repeated three times and the average value was taken.

[0041] Adhesion testing: The resin prepared in the examples was coated onto a glass substrate to a thickness of 20 μm to create a test sample. A 1 mm × 1 mm grid (10 × 10 mesh) was drawn on the surface of the cured resin using a cross-cutting tool. 3M 600 tape was then applied and peeled off at a constant speed of 1 cm / s. The rating criteria were: Grade 0: No peeling; Grade 1: Edge peeling ≤ 5%; Grade 2: Peeling 5–15%; Grade 5: Peeling > 65%.

[0042] Thermal performance testing: The resin prepared in the example was coated onto a polytetrafluoroethylene plate and cured at 80 °C for 5 min. The glass transition temperature of the resin was measured using a TA Instruments Q800 dynamic mechanical analyzer.

[0043] Table 1: Characterization results of Example 1:

[0044] Analysis of the characterization results in Table 1 above shows that the highly photosensitive resin prepared in this embodiment exhibits excellent comprehensive performance. The photosensitivity reaches 45.3 mJ / cm². 2 Compared to traditional photosensitive resins, this value is significantly improved, indicating that the resin of this invention can achieve rapid and complete curing under low-dose exposure conditions, which is beneficial for the precise replication of micro-circuits. The resolution test result is 5.2 μm, far below the 10 μm limit of traditional photosensitive resins, achieving in-depth technical optimization and meeting the extremely high requirements of line density for fifth-generation mobile communication and advanced computing devices. In the alkali resistance test, the resin film did not peel off after being immersed in 10% NaOH solution for 32 min, demonstrating excellent chemical stability, which is crucial for ensuring the long-term reliability of electronic devices in complex working environments. The viscosity value is 1980.6 mPa·s, and the suitable viscosity range is conducive to the uniform dispersion of the resin in ink and subsequent coating processes. The adhesion test result is level 0, meaning no peeling, ensuring the structural integrity of the circuit board during manufacturing and use. The glass transition temperature is 135℃. The high glass transition temperature means that the material can maintain excellent dimensional stability and mechanical strength during high-temperature reflow soldering processes, avoiding softening and deformation, thereby effectively maintaining circuit integrity and reliability.

[0045] Example 2: A method for preparing a high photosensitive resin for PCB circuit board ink, the method comprising: 1) mixing glycidyl methacrylate, pentaerythritol triacrylate and hydroquinone in a mass ratio of 3:1:0.03, stirring for 30 min under nitrogen atmosphere, temperature of 40 ℃ and rotation speed of 500 rpm to prepare a premixed monomer.

[0046] 2) The composite photoinitiator and the premixed monomer were mixed evenly at a mass ratio of 0.07:1. The mixture was stirred for 30 min at a temperature of 25 ℃, a rotation speed of 400 rpm, and in the dark to prepare the precursor. The composite photoinitiator was prepared by mixing ethyl 2,4,6-trimethylbenzoylphenylphosphonate and photoinitiator 819 at a mass ratio of 1:2.

[0047] 3) The precursor and epoxy acrylate were mixed evenly at a mass ratio of 1:0.3 and stirred for 4 h at an ambient temperature of 60 ℃ and a rotation speed of 500 rpm to prepare the optimized substrate.

[0048] 4) The optimized substrate was degassed for 13 min under an environmental pressure of -0.2 MPa, filtered using a 6 μm filter membrane, and the filtered product was made into a highly photosensitive resin.

[0049] The high photosensitivity resin prepared in this example was subjected to performance testing, and the specific characterization results are as follows: Photosensitivity test: The resin was coated on a copper substrate with a thickness of 18 μm, pre-baked at 80 ℃ for 10 min, and then passed through a photomask (resolution test pattern) with a gradient energy (10~100 mJ / cm²). 2 Expose the circuit, develop it, and observe its integrity. The minimum energy required for complete development without any residue is taken as the photosensitivity value.

[0050] Resolution detection: SEM linewidth measurement was used in conjunction with photolithography pattern transfer onto an 18 μm thick copper substrate. A KarlSuss MA6 mask alignment machine was used to perform secondary electron imaging under environmental conditions of 5 kV acceleration voltage and 8 mm working distance. Three points with the narrowest linewidth were measured at 100 μm intervals, and the average value was calculated.

[0051] Alkali resistance test: The resin prepared in the example was coated onto a glass substrate with a coating thickness of 20 μm to make a test sample. The test sample was immersed in 10% NaOH solution for 30 min. After removal, the surface condition was observed every 1 min. The adhesion was tested with a cross-cut tester. No peeling in the cross-cut area was considered qualified. The time when the resin film began to peel off was recorded.

[0052] Viscosity testing: At an environment of 25 °C, the viscosity was measured in 10 seconds. -1The shear rate was determined by using a Brookfield DV2T rotational viscometer, which was rotated for 30 seconds to obtain the viscosity value. This process was repeated three times and the average value was taken.

[0053] Adhesion testing: The resin prepared in the examples was coated onto a glass substrate to a thickness of 20 μm to create a test sample. A 1 mm × 1 mm grid (10 × 10 mesh) was drawn on the surface of the cured resin using a cross-cutting tool. 3M 600 tape was then applied and peeled off at a constant speed of 1 cm / s. The rating criteria were: Grade 0: No peeling; Grade 1: Edge peeling ≤ 5%; Grade 2: Peeling 5–15%; Grade 5: Peeling > 65%.

[0054] Thermal performance testing: The resin prepared in the example was coated onto a polytetrafluoroethylene plate and cured at 80 °C for 5 min. The glass transition temperature of the resin was measured using a TA Instruments Q800 dynamic mechanical analyzer.

[0055] Table 2: Characterization results of Example 2:

[0056] Analysis of the characterization results in Table 2 shows that the highly photosensitive resin prepared in this embodiment exhibits excellent overall performance. Compared to Example 1, this embodiment further improves the resin's performance by fine-tuning the raw material ratio and reaction conditions. The photosensitivity reaches 45.4 mJ / cm². 2 The results were slightly better than in Example 1, indicating that the resin was more sensitive to light while maintaining efficient curing. The resolution was 5.3 μm, demonstrating deep optimization of the technology and meeting the needs of finer circuit manufacturing. In the alkali resistance test, the resin film did not peel off after immersion in 10% NaOH solution for 33 min, showing a slight improvement in alkali resistance, which is significant for extending the lifespan of electronic devices in harsh environments. The viscosity was 1980.4 mPa·s, similar to Example 1, maintaining good processing performance. The adhesion test result remained at level 0, ensuring the stability of the circuit board structure. The glass transition temperature was 134.6 ℃, slightly lower than in Example 1, but still at a high level, sufficient to meet the requirements of most electronic packaging processes.

[0057] Example 3: A method for preparing a high photosensitive resin for PCB circuit board ink, the method comprising: 1) mixing glycidyl methacrylate, pentaerythritol triacrylate and hydroquinone in a mass ratio of 3.2:1:0.04, stirring for 20 min under nitrogen atmosphere, temperature of 45 ℃ and rotation speed of 600 rpm to prepare a premixed monomer.

[0058] 2) The composite photoinitiator and the premixed monomer were mixed evenly at a mass ratio of 0.09:1. The mixture was stirred for 20 min at a temperature of 27 ℃, a rotation speed of 500 rpm, and in the dark to prepare the precursor. The composite photoinitiator was prepared by mixing ethyl 2,4,6-trimethylbenzoylphenylphosphonate and photoinitiator 819 at a mass ratio of 1:2.2.

[0059] 3) The precursor and epoxy acrylate were mixed evenly at a mass ratio of 1:0.35 and stirred for 3 h at an ambient temperature of 62 ℃ and a rotation speed of 600 rpm to prepare the optimized substrate.

[0060] 4) The optimized substrate was degassed for 10 min under an environmental pressure of -0.1 MPa, filtered using a 7 μm filter membrane, and the filtered product was made into a highly photosensitive resin.

[0061] The high photosensitivity resin prepared in this example was subjected to performance testing, and the specific characterization results are as follows: Photosensitivity test: The resin was coated on a copper substrate with a thickness of 18 μm, pre-baked at 80 ℃ for 10 min, and then passed through a photomask (resolution test pattern) with a gradient energy (10~100 mJ / cm²). 2 Expose the circuit, develop it, and observe its integrity. The minimum energy required for complete development without any residue is taken as the photosensitivity value.

[0062] Resolution detection: SEM linewidth measurement was used in conjunction with photolithography pattern transfer onto an 18 μm thick copper substrate. A KarlSuss MA6 mask alignment machine was used to perform secondary electron imaging under environmental conditions of 5 kV acceleration voltage and 8 mm working distance. Three points with the narrowest linewidth were measured at 100 μm intervals, and the average value was calculated.

[0063] Alkali resistance test: The resin prepared in the example was coated onto a glass substrate with a coating thickness of 20 μm to make a test sample. The test sample was immersed in 10% NaOH solution for 30 min. After removal, the surface condition was observed every 1 min. The adhesion was tested with a cross-cut tester. No peeling in the cross-cut area was considered qualified. The time when the resin film began to peel off was recorded.

[0064] Viscosity testing: At an environment of 25 °C, the viscosity was measured in 10 seconds. -1 The shear rate was determined by using a Brookfield DV2T rotational viscometer, which was rotated for 30 seconds to obtain the viscosity value. This process was repeated three times and the average value was taken.

[0065] Adhesion testing: The resin prepared in the examples was coated onto a glass substrate to a thickness of 20 μm to create a test sample. A 1 mm × 1 mm grid (10 × 10 mesh) was drawn on the surface of the cured resin using a cross-cutting tool. 3M 600 tape was then applied and peeled off at a constant speed of 1 cm / s. The rating criteria were: Grade 0: No peeling; Grade 1: Edge peeling ≤ 5%; Grade 2: Peeling 5–15%; Grade 5: Peeling > 65%.

[0066] Thermal performance testing: The resin prepared in the example was coated onto a polytetrafluoroethylene plate and cured at 80 °C for 5 min. The glass transition temperature of the resin was measured using a TA Instruments Q800 dynamic mechanical analyzer.

[0067] Table 3: Characterization results of Example 3:

[0068] Analysis of the characterization results in Table 3 above shows that the highly photosensitive resin prepared in this embodiment exhibits excellent comprehensive performance.

[0069] The photosensitivity reached 45.4 mJ / cm², comparable to Example 2, indicating that this example maintains its high-efficiency curing characteristics even after adjusting the preparation conditions. The resolution was 5.1 μm, slightly lower than Example 2 but better than Example 1, demonstrating the potential of this example in fine circuit manufacturing. In the alkali resistance test, the resin film did not peel off after immersion in 10% NaOH solution for 32 min, with alkali resistance comparable to Example 1, ensuring the long-term reliability of electronic devices in complex environments. The viscosity was 1980.7 mPa·s, similar to Examples 1 and 2, indicating that the resin in this example has good processing performance, which is beneficial for the uniform dispersion of ink and subsequent coating processes. The adhesion test result was still grade 0, i.e., no peeling, further verifying the excellent adhesion performance of the resin in this example. The glass transition temperature was 134.5 °C, slightly lower than Examples 1 and 2, but still at a high level, sufficient to meet the thermal performance requirements of most electronic packaging processes. In summary, this embodiment successfully prepared a highly photosensitive resin with excellent comprehensive performance by precisely controlling the raw material ratio and preparation conditions, providing a new solution for the preparation of PCB circuit board inks.

[0070] Comparative Example 1: Based on Example 2, this example only modifies the premixed monomer component; the remaining steps are the same as in Example 2. Specific settings are shown in Table 4 below.

[0071] Table 4: Comparison Table of Process Adjustments for Comparative Example 1

[0072] 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 Table 5 below.

[0073] Table 5: Characterization results of Comparative Example 1 and its comparison with Example 2:

[0074] Analysis of the characterization results in Table 5 shows that replacing glycidyl methacrylate (GMA) with 1-hydroxyethylaziridine has a comprehensive negative impact on the performance of the photosensitive resin. From a molecular structure perspective, 1-hydroxyethylaziridine lacks epoxy functional groups and cannot form a stable COC ether bond structure with the carboxyl groups in the crosslinking agent, resulting in significant structural defects during the formation of the crosslinking network. This molecular-level functional group mismatch directly leads to the loosening of the polymer network structure, thereby causing a series of macroscopic property degradations.

[0075] Optical performance evaluation showed that the photosensitivity of the comparative example D1-1 was significantly reduced to 122 mJ / cm². 2 Compared to 45.4 mJ / cm in Example 2 2 The increase was approximately 168.7%. Although the four-membered ring structure of aziridine has a certain ring strain, its NC bond energy is high, and its reactivity under the attack of primary free radicals generated by the photoinitiation system is much lower than that of the α,β-unsaturated double bonds in the GMA molecule. Electronic spectroscopy analysis showed that 1-hydroxyethylaziridine has a low light absorption coefficient in the 365–405 nm wavelength range, resulting in insufficient light energy conversion efficiency, which leads to a significant decrease in the quantum yield of the polymerization reaction, and limits both the curing depth and the degree of crosslinking. This mechanism is directly reflected in the resolution of the circuit after development; Comparative Example D1-1 can only achieve a resolution of 15.5 μm, which cannot reach the 5.3 μm micro-circuit level of Example 2, thus restricting the application of high-density interconnects.

[0076] Chemical stability tests showed that Comparative Example D1-1 had a tolerance time of only 9 min in 10% NaOH solution, far lower than the relevant indicators of Example 2. Analysis of the molecular structure-performance relationship reveals this difference stems from the lack of epoxy groups involved in the secondary cross-linking reaction in the aziridine structure, preventing the formation of a high-density COC ether bond network. In an alkaline environment, the NC bonds on the aziridine ring are more susceptible to OH reactions than the COC ether bonds formed by hydroxyethyl methacrylate. - Nucleophilic attacks accelerate the hydrolytic degradation process of the network structure. This significant decrease in chemical stability will severely affect the long-term reliability of the circuit board in humid or alkaline environments.

[0077] Rheological property tests showed that the viscosity of Comparative Example D1-1 was 1326.5 mPa·s, lower than that of Example 2. From a polymer physicochemical perspective, this viscosity reduction stems from the smaller molecular size of 1-hydroxyethylaziridine compared to hydroxyethyl methacrylate, and the weaker intermolecular hydrogen bonding, leading to reduced chain entanglement. Although this viscosity remains within the applicable range for the process, it may affect the uniform dispersion and adhesion of the ink on the substrate, resulting in unstable coating quality. This inference was verified in the adhesion test; the adhesion grade of sample D1-1 was only 3, exhibiting significant interfacial peeling, which seriously threatens the structural integrity of the electronic circuitry.

[0078] Thermomechanical property analysis showed that the glass transition temperature of Comparative Example D1-1 was only 98.1 °C, which was 27% lower than that of Example 2 (134.6 °C). From the perspective of polymer chain segment motion theory, this difference stems from the fact that 1-hydroxyethylaziridine cannot participate in the formation of a high-density cross-linked network. This weakens the spatial confinement between molecular chain segments, lowers the Brownian motion threshold temperature of the chain segments, and allows the molecular chain segments to acquire sufficient thermal energy within this temperature range to begin large-scale motion. This leads to macroscopic softening of the material, which can cause irreversible deformation or damage to the circuit board under high-temperature conditions.

[0079] Comparative Example 2: Based on Example 2, this example only modifies the composite photoinitiator process; the remaining steps are the same as in Example 2. Specific settings are shown in Table 6 below.

[0080] Table 6: Comparison Table of Process Adjustments for Comparative Example 2

[0081] 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 Table 7 below.

[0082] Table 7: Characterization results of Comparative Example 2 and its comparison with Example 2:

[0083] Analysis of the characterization results in Table 7 shows that the single photoinitiator system differs significantly from the composite photoinitiator system in terms of photochemical kinetics and polymerization mechanism, leading to a significant degradation in the overall performance of the photosensitive resin. Comparative Example D2-1 uses only the bisacylphosphine photoinitiator 819 as a single initiation system, and its UV-Vis absorption spectrum is mainly concentrated in the 365–410 nm band. In contrast, the composite photoinitiator system used in Example 2 forms a broad absorption band of 350–430 nm, significantly improving the utilization rate of the exposure light source energy and establishing a surface-to-deep gradient photoinitiation mechanism through the synergistic effect of different initiators. Photodynamic measurements show that the photosensitivity of Comparative Example D2-1 decreased to 83 mJ / cm².2 Compared to 45.4 mJ / cm in Example 2 2 The increase of approximately 82.8% directly reflects the limitations of single initiators in terms of light energy capture and conversion efficiency. Photoinitiator 819 primarily generates benzoyl and phosphonoyl primary free radicals through α-cleavage of the CP bond under illumination, while ethyl 2,4,6-trimethylbenzoylphenylphosphonate generates different types of active free radicals through C / C bond cleavage. The two are complementary in terms of reactivity and steric hindrance. In the composite initiation system, this complementarity significantly improves the initiation efficiency and crosslinking uniformity of the reaction system; however, in the single initiator system, the free radicals are of a single type and unevenly distributed, leading to increased local differences in the crosslinking reaction, ultimately affecting the microstructure and macroscopic properties of the material.

[0084] Microstructure characterization revealed that the line resolution of Comparative Example D2-1 was only 8.1 μm, an increase of approximately 52.8% compared to 5.3 μm in Example 2. Scanning electron microscopy analysis showed that the line edge contours of Sample D2-1 were blurred, exhibiting a significant "undercutting" phenomenon, which is closely related to the uneven depth of photopolymerization caused by a single initiator. From the perspective of photopolymerization kinetics, the single photoinitiator 819 is rapidly consumed in the surface layer, forming a high-density cross-linked layer that hinders further light penetration, resulting in a typical gradient structural defect of "excessive surface cross-linking and insufficient internal cross-linking." This uneven cross-linking gradient directly leads to edge erosion and linewidth fluctuations during development, reducing the accuracy and reproducibility of the line resolution.

[0085] Chemical stability assessment results showed that Comparative Example D2-1 tolerated 10% NaOH solution for 21 min, a decrease of approximately 36.4% compared to 33 min in Example 2. This reduction in alkali resistance is directly related to the uniformity and density of the crosslinked network. In a single initiator system, the unevenness of local crosslinking density leads to numerous microscopic defects and low-density regions in the network structure. These regions become preferential channels for the penetration and attack of alkaline solutions, accelerating the hydrolytic degradation process of the material.

[0086] Interfacial performance testing showed that Comparative Example D2-1 had an adhesion grade of 1 (edge ​​detachment ≤5%), which, although still within an acceptable range, was significantly lower than Example 2. From an interfacial physicochemical perspective, this decrease in adhesion is related to the uneven distribution of internal stress in the cross-linked network. The uneven cross-linked structure caused by a single initiator generates high local internal stress, creating potential stress concentration areas at the substrate interface. Under external force, these areas are prone to forming initiation points for interfacial detachment, reducing overall adhesion strength. This phenomenon was further confirmed in the lap shear strength test; the interfacial bonding strength of sample D2-1 was approximately 25% lower than that of Example 2, indicating a significant risk to interfacial reliability.

[0087] Thermomechanical property analysis showed that the glass transition temperature of Comparative Example D2-1 was 120.4 °C, which was about 10.5% lower than that of Example 2 (134.6 °C). This was attributed to the uneven crosslinking network structure. From a polymer physics perspective, the uneven crosslinking density caused by a single initiator allows the relaxation process of molecular chain segments to gradually complete over a wider temperature range. Chain segments in the low crosslinking regions begin thermal motion at lower temperatures, leading to a decrease in the overall glass transition temperature. This decrease in thermal stability directly affects the dimensional stability and reliability of the material in high-temperature processes such as reflow soldering.

[0088] Comparative Example 3: Based on Example 2, this example only modifies the substrate process; the remaining steps are the same as in Example 2. Specific settings are shown in Table 8 below.

[0089] Table 8: Comparison Table of Process Adjustments for Comparative Example 3:

[0090] 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 Table 9 below.

[0091] Table 9: Characterization results of Comparative Example 3 and its comparison with Example 2:

[0092] Analysis of the characterization results in Table 9 shows that the introduction of polyurethane as a crosslinking agent into the photosensitive resin system leads to significant changes in the material's performance spectrum, particularly severe degradation in chemical stability and thermomechanical properties. From a molecular structure perspective, the key chemical group in the polyurethane crosslinking agent—the urethane bond—exhibits extremely high hydrolysis sensitivity in alkaline environments. Under alkaline conditions, the breaking of this bond follows second-order reaction kinetics, with a reaction rate constant much higher than that of the COC ether bond formed by the epoxy group reaction. - The ions first undergo a nucleophilic attack on the carbonyl carbon atom of the urethane bond, forming a tetrahedral intermediate. A β-elimination reaction then occurs, leading to bond breakage and the release of carbon dioxide, ultimately decomposing into amine and alcohol fragments. This molecular-level structural defect is directly reflected in the alkali resistance test of sample D3-1, where its tolerance time in 10% NaOH solution is only 4.5 min, a decrease of approximately 86.4% compared to 33 min in Example 2. This indicates that the polyurethane crosslinking network almost completely fails in an alkaline environment.

[0093] In terms of photochemical performance, the photosensitivity of comparative example D3-1 was 48 mJ / cm. 2The efficiency was similar to 45.4 mJ / cm² in Example 2, with a difference of only 5.7%, indicating that the polyurethane crosslinking agent had a limited impact on the initiation and propagation stages of the free radical polymerization reaction. This phenomenon can be explained by the fact that although the urea and urethane groups in the polyurethane structure can undergo chain transfer reactions with free radicals, their impact on the kinetic parameters of the main polymerization reaction is small, and the photoinitiation system can still maintain basic reaction efficiency. However, in the termination stage, the presence of polyurethane may prematurely terminate some growth chains through chain transfer reactions. This explains why the resolution test result of 5.5 μm for sample D3-1 was slightly lower than that of 5.3 μm in Example 2, indicating a slight decrease in the ability to precisely control the microstructure.

[0094] Interface performance evaluation showed that the adhesion grade of comparative example D3-1 dropped to level 4, with large-area delamination, reflecting significant defects in the interfacial bonding of the polyurethane crosslinking network. From a polymer morphology perspective, there was a clear microphase separation between the soft segments (polyether or polyester) and hard segments (urea or urethane groups formed by diisocyanate and chain extenders) in the polyurethane molecular chain, resulting in an uneven crosslinking network structure. Further observation revealed a scale-based phase separation structure on the surface of sample D3-1, with high-modulus "islands" formed in areas rich in hard segments and low-modulus "oceans" in areas rich in soft segments. This microscopic inhomogeneity leads to uneven interfacial stress distribution, easily forming stress concentration zones under thermo-mechanical cyclic loading, becoming the starting point for interfacial delamination. The heterogeneity of the polyurethane crosslinking network at the interface directly results in a significant decrease in adhesion.

[0095] Thermomechanical property analysis showed that the glass transition temperature of Comparative Example D3-1 was 102.7 °C, which was approximately 23.6% lower than that of Example 2 (134.6 °C). The results indicate that this non-uniform thermal transition behavior causes the material to gradually soften over a wide temperature range, leading to a decrease in the overall glass transition temperature. This thermal instability poses a serious risk of structural damage to the material during reflow soldering processes.

[0096] From a molecular dynamics simulation perspective, while hydrogen bond interactions in the polyurethane crosslinked network can provide additional physical crosslinking points and enhance the network structure at room temperature, these hydrogen bonds begin to dissociate rapidly in the 70–90 °C range, leading to significant relaxation of the network structure in the mid-to-high temperature region. In contrast, the chemically crosslinked network composed of COC ether bonds and CC covalent bonds in Example 2 exhibits higher thermal stability and can maintain structural integrity over a wider temperature range.

[0097] Comparative Example 4: Based on Example 2, this example only modifies the substrate preparation process; the remaining steps are the same as in Example 2. Specific settings are shown in Table 10 below.

[0098] Table 10: Comparison Table of Process Adjustments for Comparative Example 4

[0099] 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 Table 11 below.

[0100] Table 11: Characterization results of Comparative Example 4 and its comparison with Example 2:

[0101] Analysis of the characterization results in Table 11 shows that the high-temperature preparation process produces a multi-level thermally induced effect on the photosensitive resin system, ranging from free radical thermodynamics to polymer chain thermal degradation, leading to a systematic degradation of the entire spectrum of material properties. The photosensitivity of D4-1 increased to 52 mJ / cm². 2 Compared to 45.4 mJ / cm in Example 2 2 This represents an increase of approximately 14.5%. This decrease in photochemical efficiency can be explained by the free radical thermodynamic equilibrium theory. At higher temperatures, the rate constants of side reactions often increase more significantly than those of the main reaction, leading to a decrease in selectivity. At high temperatures, secondary reactions of free radicals are significantly enhanced, promoting bimolecular termination reactions between free radicals and increasing the rate of β-cleavage reactions, thus reducing initiation efficiency. Simultaneously, thermally induced chain transfer reactions generate third-generation, less reactive free radicals through hydrogen extraction mechanisms. These chain transfer events inhibit the self-acceleration process of polymerization, ultimately leading to decreased photosensitivity, manifested as an increase in required exposure energy.

[0102] Microstructural characterization revealed a significant impact of thermally induced structural defects on resolution. The line resolution of D4-1 deteriorated to 10.3 μm, an increase of approximately 94.3% compared to 5.3 μm in Example 2. Further observation revealed significant spatial inhomogeneity at the microscale in the D4-1 sample. High temperatures led to interactions within the reaction system, promoting microphase separation between components and forming inhomogeneous polymerization reaction regions. This resulted in spatially inhomogeneous cross-linked networks during photocuring, causing finger-like instability at the polymerization front. These microscopic morphological defects were further amplified during development, directly causing serrated fluctuations at the line edges and a substantial decrease in resolution.

[0103] Environmental stability assessments revealed the impact of thermal degradation on chemical resistance. The resistance time of D4-1 in 10% NaOH solution decreased to 18 min, a reduction of approximately 45.5% compared to 33 min in Example 2. High temperatures lead to the creation of heat-sensitive sites in the material, increasing the chemical environmental diversity of ester and ether bonds, which is directly related to the molecular chain breakage caused by thermal degradation. Simultaneously, the chemical weaknesses generated by thermal degradation become preferential sites for alkali attack, significantly reducing the material's alkali resistance.

[0104] Interfacial performance analysis revealed the mechanism by which thermal stress undermines interfacial stability, with the adhesion grade of D4-1 decreasing to level 2 (5% < peeling area ≤ 15%). The number of oxygen bridges, such as ether bonds (COC) and ester bonds (C(O)-O), at the resin-substrate interface in D4-1 decreased. This indicates that polar functional groups degrade under high-temperature conditions, leading to increased complexity and inhomogeneity in the interfacial structure. This change in interfacial structure directly stems from conformational changes in molecular chains, chemical bond breaking, and interfacial migration effects caused by high temperatures, resulting in a significant decrease in interfacial bonding strength, manifested as a deterioration in adhesion grade.

[0105] Comparative Example 5: Based on Example 2, this example only modifies the premixed monomer component; the remaining steps are the same as in Example 2. Specific settings are shown in Table 12 below.

[0106] Table 12: Comparison Table of Process Adjustments for Comparative Example 5:

[0107] 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 Table 13 below.

[0108] Table 13: Characterization results of Comparative Example 5 and its comparison with Example 2:

[0109] Analysis of the characterization results in Table 13 above shows that although the adjustment of the proportion of premixed monomer components in Comparative Example D5-1 brought a slight improvement in microstructure control, it also caused varying degrees of performance degradation in key indicators such as photochemical sensitivity, chemical stability, interfacial adhesion, and thermomechanical properties.

[0110] The D5-1 exhibited a significant degradation in photosensitivity, reaching 65.0 mJ / cm². 2 Compared to 45.4 mJ / cm in Example 2 2 The increase was approximately 43.2%. This is closely related to the changes in the photoinitiator microenvironment caused by the adjustment of the ratio of glycidyl methacrylate, pentaerythritol triacrylate, and hydroquinone. The reduced polarity of the chemical environment surrounding the benzoyl group of the photoinitiator in D5-1 led to a decrease in both the initiation efficiency and propagation rate of the photopolymerization reaction. This further affected photosensitivity, manifested as a significant increase in the light energy threshold required for curing.

[0111] Microstructure characterization revealed that D5-1 achieved a line resolution of 4.9 μm, slightly better than the 5.3 μm of Example 2, representing an improvement of approximately 7.5%. Further observation revealed root-mean-square roughness at the edges of the D5-1 lines; this improvement in microstructure can be attributed to the inhibitory effect of monomer composition adjustment on phase separation behavior. The improved structural uniformity and reduced correlation length at the nanoscale of D5-1 indicate a weakened tendency for microphase separation. However, this slight improvement in microstructure control failed to compensate for the significant degradation in other key performance indicators.

[0112] Chemical stability assessments showed that the tolerance time of D5-1 in 10% NaOH solution was shortened to 24 min, a decrease of approximately 27.3% compared to 33 min in Example 2. The COC ether bonds of D5-1 are more sensitive to alkaline hydrolysis in an alkaline environment. The pore size distribution widens, the cross-linked network structure loosens, and more diffusion channels are formed. This microstructural change directly leads to accelerated alkali penetration, an increase in attack points, and ultimately a significant decrease in alkali resistance.

[0113] Interfacial performance analysis showed that the adhesion grade of D5-1 dropped to level 1 (edge ​​detachment ≤ 5%), a slight deterioration compared to level 0 (no detachment) in Example 2. Further observation revealed that the weakened charge transfer effect of D5-1 resulted in a decrease in interfacial adhesion strength, leading to a higher risk of interfacial failure during service, especially under thermo-mechanical cyclic loading.

Claims

1. A method for preparing a high-photosensitive resin for PCB circuit board ink, characterized in that, The method includes: 1) mixing ester compounds, acid ester compounds and polyphenols in proportion to prepare a premixed monomer; 2) mixing a composite photoinitiator and the premixed monomer in proportion and stirring to prepare a precursor; 3) mixing the precursor and a carboxylic acid compound in proportion and stirring to prepare an optimized substrate; 4) degassing the optimized substrate under reduced pressure and filtering to prepare a highly photosensitive resin.

2. The method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1, characterized in that, The ester compound in step 1) is glycidyl methacrylate; the acid ester compound in step 1) is pentaerythritol triacrylate; the polyphenol in step 1) is hydroquinone; the ester compound, acid ester compound and polyphenol in step 1) are mixed evenly in a mass ratio of (2.8-3.2):1:(0.02-0.04).

3. A method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1 or 2, characterized in that, Step 1) The preparation of the premixed monomer is carried out under nitrogen atmosphere, temperature of 35-45 ℃, and stirring at 400-600 rpm for 20-40 min.

4. The method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1, characterized in that, Step 2) The composite photoinitiator is prepared by mixing ethyl 2,4,6-trimethylbenzoylphenylphosphonate and photoinitiator 819 at a mass ratio of 1:(1.8-2.2); Step 2) The composite photoinitiator and the premixed monomer are mixed uniformly at a mass ratio of (0.05-0.09):

1.

5. A method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1 or 4, characterized in that, Step 2) The stirring preparation is carried out in an environment with a temperature of 23-27 ℃, a rotation speed of 300-500 rpm, and in the dark, for 20-40 min.

6. The method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1, characterized in that, Step 3) The carboxylic acid compound is an epoxy acrylate; Step 3) The precursor and the carboxylic acid compound are mixed evenly at a mass ratio of 1:(0.25~0.35).

7. A method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1 or 6, characterized in that, Step 3) The stirring preparation is carried out under environmental conditions of 58-62 ℃ and 400-600 rpm for 3-5 h.

8. The method for preparing a high-photosensitive resin for PCB circuit board ink according to claim 1, characterized in that, Step 4) The degassing is performed under reduced pressure conditions of -0.3 to -0.1 MPa for 10 to 15 minutes; Step 4) The filtration is performed using a 5 to 7 μm filter membrane.

9. A high-photosensitive resin for PCB circuit board line ink prepared by any one of claims 1 to 8.

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