PCB dry film and preparation method thereof

Abstract

This invention discloses a PCB dry film and its preparation method, belonging to the field of PCB manufacturing materials. The dry film comprises a polyester carrier film, a functional resin layer, and a polyethylene protective film. The resin layer polymer composition contains, by weight,: (A) 45-65 parts of a base binder resin; (B) 20-40 parts of a crosslinkable monomer; (C) 28 parts of a crosslinking initiator; and (D) 0.5-5 parts of additives. Wherein (A) is a multifunctional modified acrylate copolymer, with main or side chain bonds containing nitrogen or sulfur heterocyclic groups, olefinic unsaturated crosslinking groups, free carboxyl groups, and polylactic acid ester or polycaprolactone microblocks, a weight-average molecular weight of 30,000-80,000, and an acid value of 120-180 mgKOH / g. This invention ensures that the dry film has excellent developability, thereby meeting the manufacturing requirements of high-quality printed circuit boards.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing materials, specifically to a PCB dry film and its preparation method. Background Technology

[0002] PCB dry film is widely used in various manufacturing stages of printed circuit boards. Existing PCB dry films are developing towards higher adhesion, resistance to side etching, and higher toughness while ensuring film formation and photosensitivity. Among them, the interfacial bonding ability of dry film in fine circuit processing is receiving increasing attention, and the requirements for the anti-overflow and dimensional stability of the products are extremely strict. The base binder resin is the matrix structure of dry film formation, and its micro-skeleton morphology and network uniformity directly affect the core indicators of dry film such as adhesion, development performance, and resistance to side etching.

[0003] In actual hot pressing and developing processes, the dry film needs to have good interfacial compliance to effectively fill the rough copper surface and form a stress buffer layer after curing to prevent the penetration of the etching solution. However, due to the limitations of the network structure characteristics of polymers, conventional resin layers often exhibit the characteristics of a rigid continuous phase, which not only results in concentrated shrinkage stress during curing but also has insufficient wetting properties. Traditional materials lack heterocyclic anchoring points that can form strong coordination with the copper surface, and the resin backbone fails to construct a sufficiently covalent cross-linked network with multifunctional monomers, causing unfixed chain segments to migrate under pressure, leading to edge overflow. This structural defect of poor network structure integrity and weak interfacial bonding easily promotes the diffusion of etching solution along the interface, resulting in severe side etching and a sharp decline in adhesion. Its overall performance is no longer able to meet the development requirements of modern high-precision printed circuit boards. Summary of the Invention

[0004] The purpose of this invention is to provide a PCB dry film and its preparation method to solve the problems mentioned in the background art.

[0005] The technical solution of the present invention includes: a dry film comprising a polyester carrier film, a functional resin layer coated on the polyester carrier film, and a polyethylene protective film laminated on the surface of the functional resin layer;

[0006] The functional resin layer is made of a polymer composition, which, by weight, comprises:

[0007] (A) Base binder resin: 45~65 parts;

[0008] (B) Crosslinkable monomers: 20-40 parts;

[0009] (C) Crosslinking initiator: 2-8 parts;

[0010] (D) Additives: 0.5~5 parts;

[0011] Wherein, the (A) base binder resin is a multifunctional modified acrylate copolymer, wherein the main chain or side chain of the acrylate copolymer is covalently bonded with nitrogen- or sulfur-containing heterocyclic groups, olefinic unsaturated crosslinking groups, free carboxyl groups, and polylactic acid ester or polycaprolactone microblocks; the (A) base binder resin has a weight-average molecular weight of 30,000 to 80,000 and an acid value of 120 to 180 mg KOH / g.

[0012] Preferably, the (B) crosslinkable monomer is selected from one or more of trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, and ethoxylated bisphenol A dimethacrylate;

[0013] The (C) crosslinking initiator is selected from one or more of azobisisobutyronitrile, benzoyl peroxide, and dicumyl peroxide;

[0014] The additives (D) include leveling agents, crystal violet lactone, malachite green, and thermal polymerization inhibitors.

[0015] Preferably, the nitrogen- or sulfur-containing heterocyclic group is selected from methacrylic acid derivative groups containing a thiadiazole structure or methacrylic acid derivative groups containing an imidazole structure.

[0016] A method for preparing PCB dry film, the method comprising the following steps:

[0017] Step S1, preparing the (A) base binder resin:

[0018] A methacrylic acid monomer containing a free carboxyl group, a vinyl monomer containing a nitrogen- or sulfur-containing heterocyclic group, and a macromonomer containing a polylactic acid ester or polycaprolactone microblock are mixed with a solvent, and an initiator is added to carry out a free radical solution copolymerization reaction to obtain a prepolymer solution.

[0019] Add an epoxy-containing methacrylate monomer, a ring-opening catalyst, and a polymerization inhibitor to the prepolymer solution to carry out a ring-opening esterification reaction, so that the epoxy-containing methacrylate monomer reacts with some of the carboxyl groups on the main chain of the prepolymer, and grafts olefinic unsaturated crosslinking groups to the resin side chain to obtain the (A) basic binder resin.

[0020] Step S2, preparing the polymer composition:

[0021] The (A) base binder resin, the (B) crosslinkable monomer, the (C) crosslinking initiator and the (D) additive are physically blended, solvent is added to adjust the viscosity, and after stirring evenly, the mixture is filtered to obtain the coating solution.

[0022] Step S3, Coating and Lamination:

[0023] The coating solution is uniformly applied to the polyester carrier film, and then dried to remove the solvent, forming the functional resin layer. The polyethylene protective film is then laminated onto the surface of the functional resin layer, and the film is wound up to obtain the PCB dry film.

[0024] Preferably, in step S1, the conditions for the free radical solution copolymerization reaction are: under nitrogen protection, the reaction temperature is 75~85℃, and the reaction time is 4~6 hours.

[0025] The solvent is selected from propylene glycol methyl ether acetate or butanone; the initiator is azobisisobutyronitrile.

[0026] Preferably, in step S1, the methacrylic acid monomer containing a free carboxyl group is a mixture of methacrylic acid and methyl methacrylate; the vinyl monomer containing the nitrogen- or sulfur-containing heterocyclic group is methacrylamido-1,3,4-thiadiazole or methacrylamido-5-methyl-1,3,4-thiadiazole; and the macromonomer containing the polylactic acid ester or polycaprolactone microblock is polylactic acid monomethacrylate.

[0027] The epoxy-containing methacrylate monomer is glycidyl methacrylate.

[0028] Preferably, in step S1, the conditions for the ring-opening esterification reaction are as follows: under the condition of introducing a trace amount of air, the temperature of the reaction is kept at 95~105℃, the reaction time is 8~12 hours, and the system acid value is measured to drop to 120~180mgKOH / g and remain basically unchanged before cooling down and discharging.

[0029] The ring-opening catalyst is selected from tetrabutylammonium bromide or triphenylphosphine; the polymerization inhibitor is p-methoxyphenol.

[0030] Preferably, in step S2, the filtration process uses a filter cartridge with a pore size of 5 μm.

[0031] Preferably, in step S3, the thickness of the polyester carrier film is 16 μm; the drying conditions are: drying at 80~100℃ for 3 minutes; the thickness of the functional resin layer is 30 μm; and the thickness of the polyethylene protective film is 15 μm.

[0032] This invention provides a PCB dry film and its preparation method, which has the following improvements and advantages compared with the prior art:

[0033] 1. This invention uses a multifunctional modified acrylate copolymer as the base binder resin. By covalently bonding various specific groups to its main chain or side chain, the material properties are synergistically improved. Among them, nitrogen-containing or sulfur-containing heterocyclic groups can effectively enhance the bonding force at the dry film interface; polylactic acid ester or polycaprolactone microblocks significantly improve the flexibility and film-forming properties of the dry film; olefinic unsaturated crosslinking groups ensure efficient subsequent crosslinking; and free carboxyl groups, combined with strictly controlled resin acid value and weight-average molecular weight, ensure that the dry film has excellent development performance, thereby meeting the manufacturing requirements of high-quality printed circuit boards.

[0034] 2. The preparation method of this invention achieves precise modification of the resin through a stepwise reaction; a prepolymer is synthesized by free radical solution copolymerization, and epoxy-containing methacrylate monomers are grafted onto the side chains through ring-opening esterification in the presence of a catalyst and a polymerization inhibitor; during this process, the stability and consistency of the synthesis of the base binder resin are ensured by strictly monitoring the heat preservation reaction time and the range of acid value decrease; in addition, the use of specific micron-sized pore size filtration treatment and precise control of the thickness parameters of each layer of polyester carrier film, functional resin layer and polyethylene protective film effectively ensures the high uniformity of the coating and the structural stability of the final product. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0036] Example 1: This example provides a PCB dry film, which is prepared according to the following steps;

[0037] S1, Preparation of basic binder resin: 120g of butanone was added to a four-necked flask equipped with a mechanical stirrer, thermometer, dropping funnel and condenser. After purging with nitrogen for 30min, the temperature was raised to 80℃. 28g of methacrylic acid, 32g of methyl methacrylate, 10g of methacrylamide-1,3,4-thiadiazole, 18g of polylactic acid monomethacrylate, 1.8g of azobisisobutyronitrile and 60g of butanone were mixed to form a monomer mixture, which was then added dropwise to the flask at a uniform rate over 2h.

[0038] After the addition is completed, the reaction is kept at a constant temperature for 4 hours to obtain a prepolymer solution. Its function is to provide a linear polymer backbone with specific microblocks and heterocyclic groups, providing reaction sites for subsequent grafting.

[0039] 12g of glycidyl methacrylate, 0.6g of tetrabutylammonium bromide, and 0.12g of p-methoxyphenol were added to the above prepolymer solution. The mixture was kept at 100°C with a trace amount of air introduced and reacted for 10 hours. The acid value was measured every 2 hours during the reaction. The reaction was stopped when the acid value stabilized at 152mgKOH / g. The mixture was cooled and discharged to obtain a base binder resin solution with a solid content of 48%. This solution not only serves as the matrix structure for dry film formation but also provides good compliance and interfacial adhesion during hot pressing. The weight-average molecular weight of this resin is 62,000.

[0040] S2, prepare a polymer composition coating solution; take the above-mentioned basic binder resin solution, 14 parts of trimethylolpropane triacrylate, 8 parts of dipentaerythritol hexaacrylate, 10 parts of ethoxylated bisphenol A dimethacrylate, 1.5 parts of azobisisobutyronitrile, 1.5 parts of benzoyl peroxide, 1.0 part of dicumyl peroxide, 0.4 parts of leveling agent, 0.3 parts of crystal violet lactone, 0.2 parts of malachite green, and 0.1 parts of heat-inhibiting agent for physical blending;

[0041] A mixed solvent of butanone and propylene glycol methyl ether acetate was added to control the coating viscosity at 2500 mPa·s. The mixture was stirred at 1800 rpm for 25 min using a disperser and then filtered using a 5 μm filter to obtain a uniform coating solution. This coating solution has good leveling properties and suitable viscosity, ensuring that no bubbles or streaks are generated in the subsequent coating process, and forming a coating of uniform thickness.

[0042] S3, Coating and Lamination: The coating liquid is evenly applied to a 16μm thick polyester carrier film through a slit die, and the wet film thickness is controlled to be about 65μm to ensure that the desired dry film thickness is obtained after drying. The film is dried in a 90℃ oven for 3 minutes to effectively remove the mixed solvent and prevent the crosslinking initiator from decomposing prematurely, forming a 30μm thick functional resin layer. A 15μm thick polyethylene protective film is laminated on the surface of the functional resin layer, and the film is wound up to obtain the PCB dry film.

[0043] Example 2: This example provides a PCB dry film, the preparation steps of which are the same as those in Example 1, the only difference being the types and amounts of each raw material as follows;

[0044] In S1, 12g of methacrylamide-5-methyl-1,3,4-thiadiazole was used as a heterocyclic vinyl monomer, 20g of polycaprolactone monomethacrylate was used as a macromonomer, and 26g of methacrylic acid, 28g of methyl methacrylate, and 2.2g of azobisisobutyronitrile were added and mixed; the free radical solution copolymerization temperature was 82℃, and the temperature was maintained for 5h;

[0045] Subsequently, 16g of glycidyl methacrylate, 0.8g of triphenylphosphine, and 0.15g of p-methoxyphenol were added, and the mixture was reacted at 98℃ for 9 hours. The resulting base binder resin solution had a resin acid value of 145mgKOH / g and a weight-average molecular weight of 54000.

[0046] In S2, the above-mentioned basic binder resin solution, 18 parts of trimethylolpropane triacrylate, 12 parts of dipentaerythritol hexaacrylate, 10 parts of ethoxylated bisphenol A dimethacrylate, 3 parts of azobisisobutyronitrile, 3 parts of benzoyl peroxide, 2 parts of dicumyl peroxide, 0.8 parts of leveling agent, 0.6 parts of crystal violet lactone, 0.3 parts of malachite green, and 0.2 parts of heat-resistant polymerization inhibitor are taken to prepare a uniform coating solution, which is then filtered through a 5μm filter.

[0047] In S3, a 30μm functional resin layer is formed by drying at 95℃ for 3 minutes, and then a 15μm polyethylene protective film is laminated on it.

[0048] Example 3: This example provides a PCB dry film, the preparation steps of which are the same as those in Example 1, the only difference being the types and amounts of each raw material as follows;

[0049] In S1, 30g of methacrylic acid, 40g of methyl methacrylate, 8g of methacrylamide-1,3,4-thiadiazole, 10g of polylactic acid monomethacrylate, and 1.5g of azobisisobutyronitrile are mixed and copolymerized at 78°C for 4.5h.

[0050] Subsequently, 8g of glycidyl methacrylate, 0.4g of tetrabutylammonium bromide, and 0.08g of p-methoxyphenol were added, and the mixture was reacted at 102℃ for 11h. The resulting resin had an acid value of 167mgKOH / g and a weight-average molecular weight of 73000.

[0051] In S2, by weight of solid components, there are 65 parts of base binder resin, 10 parts of trimethylolpropane triacrylate, 6 parts of dipentaerythritol hexaacrylate, 9 parts of ethoxylated bisphenol A dimethacrylate, 1 part of azobisisobutyronitrile, 1 part of benzoyl peroxide, 1 part of dicumyl peroxide, 0.25 parts of leveling agent, 0.2 parts of crystal violet lactone, 0.1 parts of malachite green, and 0.05 parts of heat-resistant polymerization inhibitor. After filtration, the coating solution is obtained.

[0052] In S3, a 30μm functional resin layer is formed by drying at 85℃ for 3 minutes, and then a 15μm polyethylene protective film is laminated on it.

[0053] Example 4: This example provides a PCB dry film, the preparation steps of which are the same as those in Example 1, the only difference being the types and amounts of each raw material as follows;

[0054] In S1, 27g of methacrylic acid, 34g of methyl methacrylate, 9g of methacrylic acid derivative monomer containing an imidazole structure, 16g of polycaprolactone monomethacrylate, and 1.9g of azobisisobutyronitrile were copolymerized at 80℃ for 5h; subsequently, 11g of glycidyl methacrylate, 0.5g of tetrabutylammonium bromide, and 0.10g of p-methoxyphenol were added, and the reaction was carried out at 100℃ for 10h. The resulting resin had an acid value of 156mgKOH / g and a weight-average molecular weight of 60000.

[0055] In S2, by weight of solid components, there are 60 parts of base binder resin, 12 parts of trimethylolpropane triacrylate, 7 parts of dipentaerythritol hexaacrylate, 11 parts of ethoxylated bisphenol A dimethacrylate, 2 parts of azobisisobutyronitrile, 2 parts of benzoyl peroxide, 1 part of dicumyl peroxide, 0.5 parts of leveling agent, 0.3 parts of crystal violet lactone, 0.2 parts of malachite green, and 0.1 parts of heat-resistant polymerization inhibitor. After filtration, the coating solution is obtained.

[0056] In S3, a 30μm functional resin layer is formed by drying at 90℃ for 3 minutes, and then a 15μm polyethylene protective film is laminated on it.

[0057] Comparative Example 1: The difference between this comparative example and Example 1 is that in step S1, nitrogen- or sulfur-containing heterocyclic vinyl monomers are omitted, and methyl methacrylate of equal mass is used to make up the total amount of monomers. Other operating steps and process parameters are exactly the same as in Example 1.

[0058] Comparative Example 2: The difference between this comparative example and Example 1 is that in step S1, polylactic acid monomethacrylate is omitted and methyl methacrylate of equal mass is used to make up the total amount of monomers. Other operating steps and process parameters are exactly the same as in Example 1.

[0059] Comparative Example 3: The difference between this comparative example and Example 1 is that the ring-opening esterification reaction of adding glycidyl methacrylate, ring-opening catalyst and polymerization inhibitor in step S1 is omitted, and the resulting prepolymer is used directly as the base binder resin. Other operating steps and process parameters are exactly the same as in Example 1.

[0060] Comparative Example 4: The difference between this comparative example and Example 1 is that in the ring-opening esterification stage of step S1, the reaction time is extended from 10h to 15h, so that the acid value of the system is reduced to 105mgKOH / g. Other operating steps and process parameters are exactly the same as those in Example 1.

[0061] Comparative Example 5: The difference between this comparative example and Example 1 is that the reaction time in the ring-opening esterification stage of step S1 is shortened to 5 hours, so that the acid value of the system is maintained at 192 mg KOH / g. Other operating steps and process parameters are exactly the same as those in Example 1.

[0062] Performance Tests and Data Sheets:

[0063] Adhesion was tested using the cross-cut adhesion test according to GB / T9286; edge adhesive overflow was characterized by the length of adhesive flow on the end face after being stored at 30℃ and compressed for 15 days; after removing the polyethylene protective film from the dry film sample, the exposed functional resin layer was applied to the copper-clad laminate at 85℃, and then heated to 130℃ for 8 minutes for heat curing. After etching with copper chloride, the cross-section was observed using a scanning electron microscope, and the maximum inward concavity at the junction of the dry film edge and the copper surface after etching was measured as the lateral etching width; the alkaline dissolution time was determined by using a 1% sodium carbonate solution at 30℃ to determine the time for complete dissolution of the uncured film layer; the elongation at break was determined by a tensile test; and the glass transition temperature was determined by DSC.

[0064]

[0065] Comparing the test results of Example 1 and Comparative Example 1 in the table, it can be seen that after omitting the nitrogen- or sulfur-containing heterocyclic groups, the adhesion decreased from 5B to 3B, and the side etching width increased from 3.2μm to 10.6μm. The underlying mechanism is that the nitrogen or sulfur atoms in the heterocyclic groups can have strong polar or coordination interactions with the copper surface, enabling the resin to form a high interfacial bonding strength on the copper surface. When this structure is missing, the adhesion of the resin to the copper surface mainly relies on the polar interaction of carboxyl groups and mechanical intercalation, the number of interfacial anchoring points decreases, and the etching solution is more likely to penetrate along the interface, thus aggravating the side etching.

[0066] Comparing the test results of Example 1 and Comparative Example 2 in the table, it can be seen that after omitting the polylactic acid microblock, the adhesion decreased from 5B to 3B, the elongation at break decreased from 14.6% to 6.5%, the edge overflow increased from 0.0mm to 0.8mm, and the side erosion width also increased to 8.7μm. The underlying mechanism is that there is a certain difference in segment polarity between the polylactic acid or polycaprolactone microblock and the acrylic acid backbone, which can form fine phase regions in the cured network, so that the resin has good stress buffering capacity and interface compliance during the hot pressing stage, and can absorb local stress after curing.

[0067] When this feature is lost, the resin layer tends to be a more rigid continuous phase, which reduces its ability to wet and fill rough copper surfaces during application. The stress concentration during curing shrinkage leads to a simultaneous decrease in interfacial bonding and film toughness. Due to the lack of constraints on the network by flexible polymer segments, edge flow is also more pronounced.

[0068] Comparing the test results of Example 1 and Comparative Example 3 in the table, it can be seen that after omitting the ring-opening esterification grafting step, the adhesion decreased to 2B, the side etching width increased to 12.4μm, the edge overflow increased to 1.6mm, the elongation at break decreased to 5.8%, and the Tg decreased to 72℃. The underlying mechanism is that after glycidyl methacrylate reacts with the carboxyl groups on the resin chain, polymerizable olefin bonds are grafted onto the polymer backbone. The basic binder resin can directly participate in cross-linking during the curing process to form a network structure connected with multifunctional monomers.

[0069] When this step is omitted, crosslinking is mainly concentrated in the small molecule monomer phase, the covalent connection points between the resin backbone and the network are significantly reduced, the network uniformity and integrity decrease, and the unfixed chain segments are more likely to migrate during storage and hot pressing, thus significantly increasing edge overflow; at the same time, the resin skeleton at the interface is not easy to form a stable and dense layer, resulting in significant deterioration of lateral corrosion and adhesion.

[0070] Comparing the test results of Example 1 and Comparative Example 4 in the table, it can be seen that when the acid value is reduced to 105 mg KOH / g, the alkali dissolution time is extended from 43 s to 93 s, and the side etching width is increased to 6.8 μm. The low acid value indicates that the number of free carboxyl groups retained in the resin is insufficient, the ionization and swelling ability of the alkali solution on the film layer is weakened, and the alkali dissolution rate decreases.

[0071] Meanwhile, the decrease in the number of carboxyl groups also weakens the polar adsorption of the resin on the copper surface and reduces the interfacial wetting ability of the resin during the hot pressing stage, resulting in poor interfacial continuity and thus increased side etching. This result indicates that the resin acid value needs to be maintained within a certain range, and excessive ring-opening esterification is not conducive to the balance between alkali solubility and interfacial adhesion.

[0072] Comparing the test results of Example 1 and Comparative Example 5 in the table, it can be seen that when the acid value is increased to 192 mg KOH / g, the adhesion decreases to 3B, the side etching width increases to 9.5 μm, the edge overflow increases to 0.6 mm, the elongation at break decreases to 7.2%, and the Tg decreases to 79°C. The underlying mechanism is that an excessively high acid value indicates that the proportion of carboxyl groups that have not participated in the grafting reaction in the resin is too high, while the number of crosslinkable olefin bonds introduced into the resin chain is insufficient. After curing, the network density decreases, resulting in a decrease in Tg and dimensional stability, and an increase in edge flow.

[0073] Meanwhile, excessive carboxyl groups increased the polarity and liquid absorption tendency of the resin, making the etching solution easier to diffuse along the interface, thus aggravating the side etching. This result shows that simply increasing the carboxyl content cannot replace the grafted cross-linking structure, and excessively high acid value is also detrimental to the overall performance.

[0074] Furthermore, based on the data from Examples 1 to 4, it can be seen that by adjusting the combination of photoinitiators and the amount of multifunctional acrylates in step S2, and by fine-tuning various additives, the film-forming properties and curing network density of the coating liquid can be effectively optimized.

[0075] Meanwhile, in step S3, the process parameters such as drying temperature of 85℃~95℃ and drying time of 3min are varied within the recommended range. This not only removes the solvent but also prevents premature thermal crosslinking. These adjustments together ensure the excellent performance of each embodiment in core indicators such as side erosion width and elongation at break.

[0076] Based on the data from Examples 1 to 4 in the table, it can be seen that within the limited range of resin acid value, molecular weight, heterocyclic structure, microblock structure, and the amount of crosslinkable monomers and initiators, the obtained PCB dry films can all take into account adhesion, resistance to side etching, resistance to edge overflow, toughness, and alkali solubility.

[0077] Among them, Example 1 achieved a more balanced result among various properties, indicating that the synergistic effect of the heterocyclic anchoring structure, microblock flexible structure and side chain olefin grafting structure in the base binder resin is the key to obtaining the comprehensive performance of this type of dry film.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A PCB dry film, characterized by, The dry film comprises a polyester carrier film, a functional resin layer coated on the polyester carrier film, and a polyethylene protective film laminated on the surface of the functional resin layer. The functional resin layer is made of a polymer composition, which, by weight, comprises: (A) Base binder resin: 45~65 parts; (B) Crosslinkable monomers: 20-40 parts; (C) Crosslinking initiator: 2-8 parts; (D) Additives: 0.5~5 parts; Wherein, the (A) base binder resin is a multifunctional modified acrylate copolymer, wherein the main chain or side chain of the acrylate copolymer is covalently bonded with nitrogen- or sulfur-containing heterocyclic groups, olefinic unsaturated crosslinking groups, free carboxyl groups, and polylactic acid ester or polycaprolactone microblocks; the (A) base binder resin has a weight-average molecular weight of 30,000 to 80,000 and an acid value of 120 to 180 mg KOH / g; The crosslinkable monomer (B) is selected from one or more of trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, and ethoxylated bisphenol A dimethacrylate; The (C) crosslinking initiator is selected from one or more of azobisisobutyronitrile, benzoyl peroxide, and dicumyl peroxide; The additives (D) include leveling agents, crystal violet lactone, malachite green, and heat-resistant polymerization inhibitors; The nitrogen- or sulfur-containing heterocyclic group is selected from methacrylic acid derivative groups containing thiadiazole structures or methacrylic acid derivative groups containing imidazole structures.

2. A method of manufacturing a dry film for a PCB according to claim 1, characterized in that, The method includes the following steps: Step S1, preparing the (A) base binder resin: A methacrylic acid monomer containing a free carboxyl group, a vinyl monomer containing a nitrogen- or sulfur-containing heterocyclic group, and a macromonomer containing a polylactic acid ester or polycaprolactone microblock are mixed with a solvent, and an initiator is added to carry out a free radical solution copolymerization reaction to obtain a prepolymer solution. Add an epoxy-containing methacrylate monomer, a ring-opening catalyst, and a polymerization inhibitor to the prepolymer solution to carry out a ring-opening esterification reaction, so that the epoxy-containing methacrylate monomer reacts with some of the carboxyl groups on the main chain of the prepolymer, and grafts olefinic unsaturated crosslinking groups to the resin side chain to obtain the (A) basic binder resin. Step S2, preparing the polymer composition: The (A) base binder resin, the (B) crosslinkable monomer, the (C) crosslinking initiator and the (D) additive are physically blended, solvent is added to adjust the viscosity, and after stirring evenly, the mixture is filtered to obtain the coating solution. Step S3, Coating and Lamination: The coating liquid is uniformly coated on the polyester carrier film, and then dried to remove the solvent, forming the functional resin layer. The polyethylene protective film is then laminated onto the surface of the functional resin layer, and the PCB dry film is obtained by winding. In step S1, the conditions for the ring-opening esterification reaction are as follows: under the condition of introducing a trace amount of air, the temperature of the reaction is kept at 95~105℃, the reaction time is 8~12 hours, and the system acid value is measured to drop to 120~180mgKOH / g and remain basically unchanged before cooling down and discharging. The ring-opening catalyst is selected from tetrabutylammonium bromide or triphenylphosphine; the polymerization inhibitor is p-methoxyphenol.

3. The method of claim 2, wherein the dry film is applied to the PCB by screen printing. In step S1, the conditions for the free radical solution copolymerization reaction are: under nitrogen protection, the reaction temperature is 75~85℃, and the reaction time is 4~6 hours; The solvent is selected from propylene glycol methyl ether acetate or butanone; the initiator is azobisisobutyronitrile.

4. The method of claim 2, wherein the dry film is applied to the PCB by screen printing. In step S1, the methacrylic acid monomer containing a free carboxyl group is a mixture of methacrylic acid and methyl methacrylate; the vinyl monomer containing the nitrogen- or sulfur-containing heterocyclic group is methacrylamido-1,3,4-thiadiazole or methacrylamido-5-methyl-1,3,4-thiadiazole; and the macromonomer containing the polylactic acid ester or polycaprolactone microblock is polylactic acid monomethacrylate. The epoxy-containing methacrylate monomer is glycidyl methacrylate.

5. The method for preparing a PCB dry film according to claim 2, characterized in that, In step S2, the filtration process uses a filter cartridge with a pore size of 5 μm.

6. The method for preparing a PCB dry film according to claim 2, characterized in that, In step S3, the thickness of the polyester carrier film is 16 μm; the drying conditions are: drying at 80~100℃ for 3 minutes; the thickness of the functional resin layer is 30 μm; and the thickness of the polyethylene protective film is 15 μm.

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