Dry film resist, and preparation method therefor and use thereof

Abstract

A dry film resist, and a preparation method therefor and a use thereof. The dry film resist comprises the following raw material components in parts by weight: 50-70 parts of an alkali-soluble resin solution, 30-40 parts of a photopolymerizable monomer, and 0.2-5 parts of a photoinitiator. The photopolymerizable monomer is a photopolymerizable compound containing an unsaturated double bond, and the photopolymerizable compound comprises HEMA-IPDI-R-IPDI-HEMA, wherein the weight-average molecular weight of R is 1000-3000 g / mol, and R is one of polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone diol, and poly(1,4-butanediol adipate) diol. The dry film resist formed under the combined action of HEMA-IPDI-R-IPDI-HEMA and an alkali-soluble polymer resin has reduced flowability on the surface of a printed circuit board and excellent performance in a via diameter of 100 μm, so that the via plugging performance of the dry film resist can be improved.

Description

Dry film resist and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of photographic materials for patterned surfaces, in particular, relates to a dry film resist and preparation method and application thereof. BACKGROUND

[0002] With the progress and development of science and technology, electronic devices have gradually developed towards lightness, thinness and smallness in recent years, and the size of the printed circuit board patterns carried by the electronic devices is becoming smaller and smaller. In order to improve the yield of small-sized circuit boards, it is necessary for the dry film resist to have excellent resolution and adhesion at the same time. With the improvement of the precision of the printed circuit board, the number of through holes for connecting the wiring layers in the printed circuit board increases, and the diameter of the through holes decreases. In the process of dry film exposure, the wet dry film is easily pressed into the small holes, and it is difficult to completely wash off the dry film pressed into the small holes in the development film removal stage, resulting in the phenomenon of hole plugging, which leads to the fact that the hole wall cannot be electroplated, and the hole wall is easy to be short-circuited without a conductive layer. In the existing process, the adhesion of the dry film resist is increased or the processing process of the circuit board is adjusted to improve the hole plugging problem of the dry film resist, but the effect is not good. Therefore, it is very important to develop a dry film resist which has good adhesion to the printed circuit board and is not easy to plug the hole.

[0003] The related technology such as the phosphorus-containing polyurethane acrylate oligomer and its preparation method and application in patent CN11055663961A are mentioned. The alcohol used in the synthesis of the patent is a polyol with three or more functions, forming a cyclic rigid structure, so the dry film mainly has adhesion;

[0004] Patent CN200610082639.4 discloses a dry film resist, which uses a carboxyl-containing adhesive and a specific structure of a photopolymerization monomer to coact, so that the photopolymerizable resin composition contains a free radical polymerization inhibitor. The prepared photopolymerizable resin composition has excellent thermal stability and storage stability, but the hole plugging problem of the printed circuit board with small through holes is not solved;

[0005] Patent CN201710500105.7 discloses a resin composition and its use. By adjusting the molar ratio of the hydrophilic group ethylene oxide (EO) to the hydrophobic group propylene oxide (PO) in the photopolymerization monomer, the prepared resin composition has the characteristics of no hole plugging when the film is removed, fast film removal speed, etc. when used as a dry film resist, but the effect of inhibiting hole plugging is not significant, and there is still a certain percentage of defective products in mass production. SUMMARY

[0006] The present application provides a dry film resist and a preparation method and application thereof to solve the technical problem of hole plugging of the existing dry film resist used in the printed circuit board.

[0007] According to one aspect of the present application, a dry film resist is provided, comprising the following raw material components by weight: 50-70 parts of alkali-soluble resin solution, 30-40 parts of photopolymerization monomer, 0.2-5 parts of photoinitiator;

[0008] The photopolymerization monomer is a photopolymerization compound containing unsaturated double bonds, and the photopolymerization compound containing unsaturated double bonds comprises HEMA-IPDI-R-IPDI-HEMA, the structural formula of which is as follows:

[0009] wherein the weight average molecular weight of R is 1000-3000 g / mol, and R is one of polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone glycol, poly-1,4-butanediol adipate glycol,

[0010] The dry film resist has a plug rate of less than 2.2% in a pore size of 100 μm.

[0011] Further, the following raw material components by weight are included: 56-60 parts of alkali-soluble resin, 30-40 parts of photopolymerization monomer, and 3-5 parts of photoinitiator.

[0012] Further, the mass percentage of HEMA-IPDI-R-IPDI-HEMA in the photopolymerization monomer is 20-100%.

[0013] Further, the photopolymerization compound containing unsaturated double bonds further comprises a photopolymerization compound containing a vinyl unsaturated group, and the photopolymerization compound containing a vinyl unsaturated group comprises one or more of ethoxylated nonylphenol acrylate, propoxyethoxy dimethyl acrylate, ethoxylated bisphenol A dimethyl acrylate, lauryl acrylate, isodecyl acrylate, tetrahydrofurfuryl acrylate, dioxolane acrylate, 1,2-benzenedicarboxylic acid-2-hydroxyethyl-2-[(2-acryloyl)oxy]ethyl ester, polyethylene glycol diacrylate, polypropylene glycol dimethyl acrylate, ethoxylated bisphenol A diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glyceryl triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate.

[0014] Further, the alkali-soluble resin comprises one or more of methacrylic resin, styrene resin, and phenolic resin.

[0015] The molecular weight of the alkali-soluble resin is 50000-100000 g / mol.

[0016] Further, the monomers for synthesizing the alkali-soluble resin include one or more of methyl methacrylate, methyl methacrylate, butyl methacrylate, styrene, ethyl acrylate, and butyl acrylate.

[0017] Further, the photoinitiator includes one or more of benzoin ether, benzophenone and its derivatives, thioxanthone series compounds, anthraquinone and its derivatives, thioxanthone series compounds, and hexaarylbiimidazole series compounds.

[0018] Further, the dry film resist further includes the following raw material components by weight: 0.5-10 parts of an auxiliary agent and 30-50 parts of a solvent.

[0019] According to another aspect of the present application, a preparation method of a dry film resist is also provided, including the following steps:

[0020] (1) Preparation of an alkali-soluble resin: add butanone in the system, heat and reflux, and then drop the mixture of the monomers for synthesizing the alkali-soluble resin and the initiator into the system at a constant speed, the dropping time is 1-4 h, keep warm for 1-2 h, continue to drop the mixture of the initiator and butanone, the dropping time is 20-40 min, and then keep warm for 3-5 h to obtain the alkali-soluble resin, which is ready for use;

[0021] (2) Preparation of a photopolymerization compound HEMA-IPDI-R-IPDI-HEMA: uniformly mix R and isophorone diisocyanate in a toluene solution, react at 50-70℃ for 1-3 h, then drop hydroxyethyl methacrylate containing a catalyst, the dropping time is 40-80 min, react at 70-80℃ for 3-6 h, and then determine the NCO content <0.1 wt% to obtain HEMA-IPDI-R-IPDI-HEMA;

[0022] (3) Mix the alkali-soluble resin, the photopolymerization monomer, the photoinitiator, the auxiliary agent, and the solvent to obtain a dry film resist coating solution;

[0023] (4) Coating and baking the dry film resist coating solution to obtain a dry film resist.

[0024] According to still another aspect of the present application, the application of the dry film resist on a flexible circuit board is also provided.

[0025] The present application has the following beneficial effects:

[0026] The application makes the two urethane groups in the photopolymerization monomer HEMA-IPDI-R-IPDI-HEMA and the two or more carboxyl groups in the alkali-soluble high molecular resin connected through "hydrogen bonds", the strength of the "hydrogen bonds" is between the molecular force and the chemical bond, and the strength is relatively large, so that a "physical crosslinking" similar to a spatial network structure can be formed, and the static flowability of the film material is reduced. Therefore, the dry film resist formed by the photopolymerization monomer HEMA-IPDI-R-IPDI-HEMA and the alkali-soluble high molecular resin has reduced flowability on the surface of the printed circuit board, and can exhibit excellent performance in a 100-micron aperture, so that the hole plugging performance of the dry film resist can be improved, and the hole plugging problem on the surface of the printed circuit board can be avoided.

[0027] The phosphorus-containing polyurethane acrylate oligomer mentioned in the patent CN11055663961A and the application of the phosphorus-containing polyurethane acrylate oligomer and the preparation method thereof are different from each other. In the patent, an alcohol with three or more polyols is used for synthesis to form a cyclic rigid structure, so that the dry film adhesion is mainly given. In the application, the R in the photopolymerization monomer HEMA-IPDI-R-IPDI-HEMA is a dihydric alcohol with a certain molecular weight and a dihydric structure, and the crosslinking density of the compound after curing can be adjusted by adjusting the molecular weight and the distance between the two unsaturated bonds. In addition, the use of the dihydric alcohol structure can make the product have a certain flexibility in the dry film, so that the flexible circuit board has good wetting effect and good spreading on the surface of the printed circuit board during the wet pressing process of the FPC soft board. DETAILED DESCRIPTION

[0028] The embodiments of the application are described in detail below, but the application can be implemented in various different ways as defined and covered by the following description.

[0029] According to the first aspect of the embodiments of the application, a dry film resist is provided, which comprises the following raw material components by weight: 50-70 parts of an alkali-soluble resin, 30-40 parts of a photopolymerization monomer, and 0.2-5 parts of a photoinitiator.

[0030] The photopolymerization monomer is a photopolymerization compound containing an unsaturated double bond, and the photopolymerization compound containing an unsaturated double bond comprises HEMA-IPDI-R-IPDI-HEMA, and the structural formula is as follows:

[0031] wherein the weight average molecular weight of R is 1000-3000 g / mol, and the R is one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone diol, and poly-1,4-butanediol adipate diol.

[0032] The application makes the two urethane groups in HEMA-IPDI-R-IPDI-HEMA and the two or more carboxyl groups in the alkali-soluble high molecular resin connect through "hydrogen bond", the strength of "hydrogen bond" is between molecular force and chemical bond, the strength is relatively large, and "physical crosslinking" similar to space network structure can be formed, thereby reducing the static fluidity of the film material. Therefore, the dry film resist formed by the photopolymerization monomer HEMA-IPDI-R-IPDI-HEMA and the alkali-soluble high molecular resin has reduced fluidity on the surface of the printed circuit board, and the via hole performance of the dry film resist can be improved, and the via hole problem is less likely to occur on the surface of the printed circuit board.

[0033] In addition, the weight average molecular weight of R in the photopolymerization monomer HEMA-IPDI-R-IPDI-HEMA of the application is 1000-3000 g / mol. Since the R group is a linear structure, the distance between the two unsaturated bonds can be adjusted by adjusting the molecular weight, so as to change the crosslinking density after the light-curable compound is cured, and the fluidity and wettability of the dry film resist are balanced, the fluidity is reduced, and the printed circuit board also has good wettability and good spreading on the surface of the printed circuit board.

[0034] In some embodiments, the weight average molecular weight of R is more preferably 1000-2000 g / mol, and more preferably 1000-1500 g / mol.

[0035] The R is polypropylene glycol with a weight average molecular weight of 1000 g / mol, polycaprolactone diol with a weight average molecular weight of 1000 g / mol, or polybutylene glycol with a weight average molecular weight of 1000 g / mol.

[0036] In this embodiment, the dry film resist comprises the following raw material components by weight: 56-60 parts of alkali-soluble resin, 30-40 parts of photopolymerization monomer, and 3-5 parts of photoinitiator.

[0037] If the amount of photopolymerization monomer is less than 30 parts, the problem of insufficient resolution will occur, and if the amount is more than 40 parts, the problem of difficult film stripping will occur.

[0038] In this embodiment, the mass percentage of HEMA-IPDI-R-IPDI-HEMA in the photopolymerization monomer is 20-100%.

[0039] In some embodiments, the mass percentage of HEMA-IPDI-R-IPDI-HEMA in the photopolymerization monomer is preferably 40-60%.

[0040] In some embodiments, the HEMA-IPDI-R-IPDI-HEMA has a -NCO content < 0.1 wt%.

[0041] In some embodiments, the raw materials for preparing the HEMA-IPDI-R-IPDI-HEMA include 40-50 parts by weight of HEMA (hydroxyethyl methacrylate), 60-70 parts by weight of IPDI (isophorone diisocyanate), 140-160 parts by weight of R, 0.1-0.25 parts by weight of catalyst, and 30-50 parts by weight of solvent I.

[0042] In some embodiments, the raw materials for preparing the HEMA-IPDI-R-IPDI-HEMA include 45 parts by weight of HEMA, 66.5 parts by weight of IPDI, 150 parts by weight of R, 0.135 parts by weight of catalyst, and 40 parts by weight of solvent I.

[0043] As a preferred embodiment, the catalyst is dibutyl tin laurate, and the solvent I is toluene.

[0044] In some embodiments, the method for preparing the HEMA-IPDI-R-IPDI-HEMA includes the following steps: adding R into a reaction kettle, then adding IPDI (isophorone diisocyanate), then adding solvent I, reacting at 50-70°C for 1-3 h, then adding HEMA (hydroxyethyl methacrylate) containing catalyst dropwise, dropwise adding time being 40-80 min, then reacting at 70-80°C for 3-6 h, and determining NCO content, thereby obtaining HEMA-IPDI-R-IPDI-HEMA.

[0045] As a preferred embodiment, the method for preparing the HEMA-IPDI-R-IPDI-HEMA includes the following steps: adding R into a reaction kettle, then adding IPDI, then adding solvent I, reacting at 60°C for 2 h, then adding HEMA containing catalyst dropwise, dropwise adding time being 60 min, then reacting at 75°C for 4 h, and determining NCO content, thereby obtaining HEMA-IPDI-R-IPDI-HEMA.

[0046] In the present embodiment, the light polymerization compound containing unsaturated double bonds further includes a light polymerization compound containing a vinyl unsaturated group, the light polymerization compound containing a vinyl unsaturated group including one or more of ethoxy nonyl phenol acrylate, lauryl acrylate, propoxy ethoxy dimethyl acrylate, ethoxy bisphenol A dimethyl acrylate, isodecyl acrylate, tetrahydrofurfuryl acrylate, dioxane acrylate, 1,2-benzenedicarboxylic acid-2-hydroxyethyl-2-[(2-propenoyl)oxy]ethyl ester; polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, ethoxylated bisphenol A diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glyceryl triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate.

[0047] In the present embodiment, the alkali-soluble resin includes one or more of a methacrylic resin, a styrene resin, a phenolic resin; and / or, the alkali-soluble resin has a molecular weight of 50000-100000 g / mol.

[0048] In some embodiments, the alkali-soluble resin is a combination of two alkali-soluble resins.

[0049] In the present embodiment, the synthetic monomers of the alkali-soluble resin include one or more of methacrylic acid, methyl methacrylate, butyl methacrylate, styrene, ethyl acrylate, butyl acrylate.

[0050] In some embodiments, the alkali-soluble resin is selected from one or more of alkali-soluble resin A, alkali-soluble resin B, alkali-soluble resin C.

[0051] The synthetic monomers of the alkali-soluble resin A are a combination of methacrylic acid, methyl methacrylate and butyl methacrylate, with a molar ratio of (20-30):(30-50):(30-40), and a further preferred molar ratio of 25:40:35, a weight average molecular weight of 50000 g / mol, and a molecular weight distribution of 1.8.

[0052] The synthetic monomers of the alkali-soluble resin B are a combination of methacrylic acid, methyl methacrylate, butyl acrylate and styrene, with a molar ratio of (20-30):(30-50):(10-30):(10-20), and a further preferred molar ratio of 25:40:20:15, a weight average molecular weight of 50000 g / mol, and a molecular weight distribution of 1.9.

[0053] The synthetic monomers of the alkali-soluble resin C are a combination of methacrylic acid, methyl methacrylate, ethyl acrylate and butyl acrylate, with a molar ratio of (20-30):(40-50):(10-20):(10-30), and a further preferred molar ratio of 22:45:13:20, a weight average molecular weight of 100000 g / mol, and a molecular weight distribution of 1.9.

[0054] As a preferred embodiment, the alkali-soluble resin is a combination of the alkali-soluble resin A and the alkali-soluble resin B, with a weight ratio of (4-5):(5-6).

[0055] The combination of two alkali-soluble resins with a molecular weight of 50000 g / mol and photopolymerization monomers with a molecular weight of 1000-3000 g / mol, with a weight ratio of (4-5):(5-6), can optimize the plugging problem of dry film resist in wet pressing process, because the low molecular weight photopolymerization monomers can polymerize on the high molecular weight alkali-soluble resin, the hydrogen bonding of macromolecular photopolymerization monomers and the high molecular weight alkali-soluble resin further reduce the flowability of the dry film, avoiding the flow of the dry film into the hole, and further improving the plugging performance.

[0056] In some embodiments, the method for preparing the alkali-soluble resin comprises the following steps: adding 300-500 parts by weight of solvent II into a reaction kettle, heating to 80°C reflux, mixing 300-500 parts by weight of monomers with 0.1-5 parts by weight of initiator, and then dropping into the system at a constant speed, with a dropping time of 1-4 h, maintaining for 1-2 h, continuously dropping a mixture containing 1-5 parts by weight of initiator and 150-250 parts by weight of solvent II, with a dropping time of 20-40 min, and then maintaining for 3-5 h, and finally cooling to 50°C for standby.

[0057] As a preferred embodiment, the method for preparing the alkali-soluble resin comprises the following steps: adding 400 parts by weight of solvent II into a reaction kettle, heating to 80°C reflux, mixing 400 parts by weight of monomers with 4 parts by weight of initiator, and then dropping into the system at a constant speed, with a dropping time of 3 h, maintaining for 1 h, continuously dropping a mixture containing 4 parts by weight of initiator and 200 parts by weight of solvent II, with a dropping time of 30 min, and then maintaining for 4 h, and finally cooling to 50°C for standby.

[0058] As a preferred embodiment, the preparation method of the alkali-soluble resin comprises the following steps: adding 400 parts by weight of solvent II into a reaction kettle, heating to 80°C backflow, mixing 400 parts by weight of monomer with 0.8 parts by weight of initiator, and then dropping into the system at a constant speed, the dropping time is 3h, keeping for 1h, continuing to drop the mixture containing 4 parts by weight of initiator and 200 parts by weight of solvent II, the dropping time is 30min, then keeping for 4h, and finally cooling to 50°C for standby.

[0059] As a preferred embodiment, the solvent II is butanone; and the initiator is azobisisobutyronitrile.

[0060] In this embodiment, the photoinitiator includes one or more of benzoin ether, benzophenone and its derivatives, thioxanthone series compounds, anthraquinone and its derivatives, thioxanthone series compounds, hexaarylbiimidazole series compounds.

[0061] In some embodiments, the photoinitiator includes one or more of benzoin ether, benzophenone, thioxanthone, anthraquinone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthrenequinone, 2,3-dimethylanthraquinone, benzoin methyl ether, benzoin ethyl ether, benzoin phenyl ether, benzil dimethyl ketal, benzoin dimethyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin phenyl ether, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, benzophenone, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), 4,4'-bis(diethylamino)benzophenone, isopropyl thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-tert-butylanthraquinone, N,N-dimethylbenzoyl ethyl ester, dimethylaminoethyl benzoate, N,N-dimethylethanolamine, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2-bromo-5-methoxyphenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, bisimidazole, tetraethyl Michler's ketone.

[0062] In this embodiment, the raw material of the dry film resist further includes 0.5-10 parts of an auxiliary agent and 30-50 parts of a solvent.

[0063] In some embodiments, the auxiliary agent is selected from one or more of a dye, a color changing agent, a plasticizer, an antioxidant, an organic halide compound, a stabilizing agent.

[0064] In some embodiments, the solvent is selected from one or more of ketone solvents or alcohol solvents.

[0065] Embodiments of the second aspect of the application also provide a preparation method of the dry film resist, comprising the following steps:

[0066] (1) Preparation of alkali-soluble resin: add butanone into the system, heat and reflux, mix the synthetic monomers of the alkali-soluble resin with the initiator, and then drop into the system at a constant speed, the dropping time is 1-4h, keep warm for 1-2h, continue to drop the mixture of the initiator and butanone, the dropping time is 20-40min, and then keep warm for 3-5h to obtain the alkali-soluble resin for standby;

[0067] (2) Preparation of photopolymerization compound HEMA-IPDI-R-IPDI-HEMA: mix R and isophorone diisocyanate uniformly in a toluene solution, react at 50-70℃ for 1-3h, then drop hydroxyethyl methacrylate containing a catalyst, the dropping time is 40-80min, react at 70-80℃ for 3-6h, and determine that the NCO content is <0.1wt% to obtain HEMA-IPDI-R-IPDI-HEMA;

[0068] (3) Mix the alkali-soluble resin, photopolymerization monomer, photoinitiator, auxiliary agent and solvent to obtain a dry film resist coating solution;

[0069] (4) Coating and baking the dry film resist coating solution to obtain a dry film resist.

[0070] As a preferred embodiment, the viscosity of the dry film resist coating solution at 25℃ is 200-2000mPa·s, further preferably 500-1500mPa·s, and more further preferably 700-1200mPa·s.

[0071] Embodiments of the third aspect of the application also provide an application of the dry film resist on a flexible circuit board.

[0072] The dry film resist for the flexible circuit board of the application adopts a high molecular weight alkali-soluble resin combined with two different monomers, which can further optimize the hole plugging problem of the dry film resist under the wet pressing process.

[0073] The dry film resist for the flexible circuit board of the application has excellent resolution and adhesion, and can reduce the hole plugging problem of the FPC wet pressing dry film after the development process, and performs excellently in a 100μm aperture.

[0074] Example 1

[0075] A dry film resist applied to a flexible circuit board, the preparation raw materials are as follows in percentage by weight: 30 parts of alkali-soluble resin A, 28 parts of alkali-soluble resin B, 18 parts of photopolymerization monomer 1, 10 parts of photopolymerization monomer 2, 5 parts of photopolymerization monomer 3, 4 parts of photopolymerization monomer 4, 0.2 parts of photoinitiator 1, 4 parts of photoinitiator 2, 0.5 parts of additive 1, 0.05 parts of additive 2, 0.01 parts of additive 3, 0.05 parts of additive 4, 1.5 parts of additive 5 and 30 parts of solvent.

[0076] The preparation method of the alkali-soluble resin A comprises the following steps: adding 400 parts by weight of butanone into a reaction kettle, heating to 80℃ backflow, mixing 400 parts by weight of monomers with 4 parts by weight of azobisisobutyronitrile, dropping into the system at a constant speed, the dropping time is 3h, keeping warm for 1h, continuously dropping the mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone, the dropping time is 30min, then keeping warm for 4h, and finally cooling to 50℃ for standby.

[0077] The monomers are a combination of methacrylic acid, methyl methacrylate and butyl methacrylate, the molar ratio is 25:40:35. The weight average molecular weight is 50000g / mol, and the molecular weight distribution is 1.8.

[0078] The preparation method of the alkali-soluble resin B comprises the following steps: adding 400 parts by weight of butanone into a reaction kettle, heating to 80℃ backflow, mixing 400 parts by weight of monomers with 4 parts by weight of azobisisobutyronitrile, dropping into the system at a constant speed, the dropping time is 3h, keeping warm for 1h, continuously dropping the mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone, the dropping time is 30min, then keeping warm for 4h, and finally cooling to 50℃ for standby.

[0079] The monomers are a combination of methacrylic acid, methyl methacrylate, butyl acrylate and styrene, the molar ratio is 25:40:20:15. The weight average molecular weight is 50000g / mol, and the molecular weight distribution is 1.9.

[0080] The photopolymerization monomer 1 is HEMA-IPDI-R-IPDI-HEMA.

[0081] The photopolymerization monomer 2 is ethoxylated bisphenol A dimethacrylate (purchased from Changxing Special Materials (Suzhou) Co., Ltd.);

[0082] The photopolymerization monomer 3 is propoxyethoxy dimethacrylate (purchased from Changxing Special Materials (Suzhou) Co., Ltd.);

[0083] The photopolymerization monomer 4 is ethoxylated nonylphenol acrylate (purchased from Changxing Special Materials (Suzhou) Co., Ltd.).

[0084] The photoinitiator 1 is bisimidazole; the photoinitiator 2 is tetraethyl Michler's ketone.

[0085] The auxiliary is a color developer, auxiliary 1 is colorless crystal violet; auxiliary 2 is malachite green; auxiliary 3 is hydroquinone; auxiliary 4 is 5-carboxybenzimidazole; auxiliary 5 is p-toluenesulfonamide.

[0086] The solvent is butanone.

[0087] The preparation method of the dry film resist comprises the following steps:

[0088] S1: preparing an alkali-soluble resin: 400 parts by weight of butanone is added to a reaction kettle, heated to 80°C reflux, 400 parts by weight of monomers and 4 parts by weight of azobisisobutyronitrile are mixed and then uniformly dropped into the system, the dropping time is 3h, and the system is kept at 80°C for 1h, then a mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone is continuously dropped, the dropping time is 30min, then the system is kept at 80°C for 4h, and finally the temperature is reduced to 50°C, thus obtaining the alkali-soluble resin A for standby;

[0089] S1: preparing an alkali-soluble resin: 400 parts by weight of butanone is added to a reaction kettle, heated to 80°C reflux, 400 parts by weight of monomers and 4 parts by weight of azobisisobutyronitrile are mixed and then uniformly dropped into the system, the dropping time is 3h, and the system is kept at 80°C for 1h, then a mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone is continuously dropped, the dropping time is 30min, then the system is kept at 80°C for 4h, and finally the temperature is reduced to 50°C, thus obtaining the alkali-soluble resin B for standby;

[0090] S2: preparing a photopolymerization monomer: 150 parts of R is added to a reaction kettle, then 66.5 parts of IPDI (isophorone diisocyanate) is added, then 40 parts of toluene is added and reacted at 60°C for 2h, then a mixture of 0.135 parts of dibutyltin laurate and 45 parts of HEMA (hydroxyethyl methacrylate) is dropped, the dropping time is 60min, then the system is reacted at 75°C for 4h, and the -NCO content is determined to be <0.1wt%, thus obtaining HEMA-IPDI-R-IPDI-HEMA. Wherein R is polypropylene glycol with a weight average molecular weight of 1000g / mol;

[0091] S3: mixing the alkali-soluble resin, the photopolymerization monomer, the photoinitiator, the auxiliary and the solvent to obtain a dry film resist coating solution;

[0092] S4: coating and baking the dry film resist coating solution to obtain a dry film resist.

[0093] Example 2

[0094] The difference between this example and example 1 is that 18 parts of the photopolymerization monomer 1 in example 1 is replaced by an equal amount of the photopolymerization monomer 5;

[0095] The preparation method of the photopolymerization monomer 5 is to replace R used in the preparation process of the photopolymerization monomer 1 with polypropylene glycol with a weight average molecular weight of 2000 g / mol.

[0096] Example 3

[0097] The difference between this example and Example 1 is only that 18 parts of the photopolymerization monomer 1 in Example 1 is replaced with an equal amount of the photopolymerization monomer 6;

[0098] The preparation method of the photopolymerization monomer 6 is to replace R used in the preparation process of the photopolymerization monomer 1 with polypropylene glycol with a weight average molecular weight of 3000 g / mol.

[0099] Example 4

[0100] The difference between this example and Example 1 is only that 18 parts of the photopolymerization monomer 1 in Example 1 is replaced with an equal amount of the photopolymerization monomer 7;

[0101] The preparation method of the photopolymerization monomer 7 is to replace R used in the preparation process of the photopolymerization monomer 1 with polycaprolactone diol with a weight average molecular weight of 1000 g / mol.

[0102] Example 5

[0103] The difference between this example and Example 1 is only that 18 parts of the photopolymerization monomer 1 in Example 1 is replaced with an equal amount of the photopolymerization monomer 8;

[0104] The preparation method of the photopolymerization monomer 8 is to replace R used in the preparation process of the photopolymerization monomer 1 with polybutylene glycol with a weight average molecular weight of 1000 g / mol.

[0105] Example 6

[0106] The difference between this example and Example 1 is only that 18 parts of the photopolymerization monomer 1 in Example 1 is replaced with an equal amount of the photopolymerization monomer 9;

[0107] The preparation method of the photopolymerization monomer 9 is to replace R used in the preparation process of the photopolymerization monomer 1 with polyethylene glycol with a weight average molecular weight of 1000 g / mol.

[0108] Example 7

[0109] The difference between this example and Example 1 is only that 18 parts of the photopolymerization monomer 1 in Example 1 is replaced with an equal amount of the photopolymerization monomer 11;

[0110] The preparation method of the photopolymerization monomer 11 is to replace R used in the preparation process of the photopolymerization monomer 1 with polyethylene glycol with a weight average molecular weight of 1000 g / mol.

[0111] Polybutylene adipate glycol with a molecular weight of 1000 g / mol.

[0112] Example 8

[0113] The difference between this example and Example 1 is that 18 parts of photopolymerizable monomer 1 in Example 1 is adjusted to 24 parts, and photopolymerizable monomer 2 is adjusted to 7 parts.

[0114] Example 9

[0115] The difference between this example and Example 1 is only that 18 parts of photopolymerizable monomer 1 in Example 1 is adjusted to 12 parts.

[0116] Example 10

[0117] The difference between this example and Example 1 is that 18 parts of photopolymerizable monomer 1 in Example 1 is adjusted to 6 parts, and photopolymerizable monomer 2 is increased to 22 parts.

[0118] Comparative Example 1

[0119] The difference between this comparative example and Example 1 is only that 18 parts of photopolymerizable monomer 1 in Example 1 is replaced with an equal amount of photopolymerizable monomer 12.

[0120] The photopolymerizable monomer 12 is a reactant of 2 mol of propylene glycol hydroxyethyl acrylate and 1 mol of hexamethylene diisocyanate (purchased from Huazhuo Chemical Co., Ltd. Wuxi, product code UXR-1200).

[0121] The reaction process is: OCNRNCO + 2R1-OH → R1OOCHNRNHCOOR1

[0122] Comparative Example 2

[0123] The difference between this comparative example and Example 1 is only that 18 parts of photopolymerizable monomer 1 in Example 1 is cancelled, and photopolymerizable monomer 2 is increased to 28 parts.

[0124] Comparative Example 3

[0125] The difference between this comparative example and Example 1 is that 10 parts of photopolymerizable monomer 2 in Example 1 is adjusted to 3 parts, and photopolymerizable monomer 3 is adjusted to 3 parts.

[0126] Comparative Example 4

[0127] The difference between this comparative example and Example 1 is that 10 parts of photopolymerizable monomer 2 in Example 1 is adjusted to 15 parts.

[0128] Performance Test

[0129] Test sample preparation:

[0130] (1) The prepared dry film resist is coated on a base film (PET), and then dried at 80°C for 1 hour, and the thickness after drying is 25 μm (not including the base film);

[0131] (2) The dry film resist is then hot-pressed on a 0.0361 mm thick FPC flexible copper-clad plate at 110°C, a pressure of 0.4-0.5 MPa, and a conveying speed of 1.5 m / min, exposed using parallel light, and exposed using a stouffer 41-grid exposure ruler with an energy grid of 125 x 25 mm at an energy of 30-120 mJ / cm 2 After exposure, the product is left to stand for 30 minutes before entering the developing process;

[0132] (3) The developing speed is set to 0-6 m / min with a frequency conversion, the base film is torn off, and placed on the transmission line of a special developing machine, the equipment is JL-2009XY-I, the temperature is set to 30±1°C, and the pressure is set to 0.14-0.17 MPa, the unexposed part is completely washed off, and after the developing is finished, it is dried.

[0133] 1. Sensitivity evaluation:

[0134] Exposure ruler: Stouffer 41ST exposure ruler sensitivity test sheet; developing solution: 1.0±0.2 wt% Na2CO3 aqueous solution; developing temperature: 30±1°C; developing pressure: 0.14-0.17 MPa.

[0135] After developing is finished, dry, observe the residual number of the copper-clad plate exposure ruler, read the residual grid number of the 41-grid ruler line, and take the energy corresponding to the residual grid number 16 as the sensitivity. The lower the energy value under the same grid number, the better the sensitivity.

[0136] 2. Adhesion evaluation:

[0137] After developing is finished, dry, and observe the residual pattern on the developed copper-clad plate using an optical microscope, and take the minimum line width as the determination standard, which is complete, clear, vertical, and without line loss.

[0138] The performance test film with L / 400, line width / line spacing equal to 10 / 400 to 40 / 400 is read after the exposure and developing process, and the minimum value of the remaining is the adhesion.

[0139] 3. Resolution evaluation:

[0140] After developing is finished, dry, and observe the developed pattern on the developed copper-clad plate using an optical microscope, and take the minimum line width and line spacing as the final result or determination standard, which is without dry film residue between lines, and the projection of the dry film side wall is clear.

[0141] The minimum value of the remaining after the exposure and development process with L / S (line width / line space) of 10 / 10 to 40 / 40 is read, and is the resolution.

[0142] 4. Stripping ability evaluation:

[0143] Stripping solution: 3.0±0.5wt% NaOH aqueous solution; Stripping temperature: 50±5℃.

[0144] After development, the time from the copper plate into the stripping solution to the complete peeling of the dry film on the copper plate is recorded as the stripping time;

[0145] The above step is repeated 3 times, and the average value of the stripping time is recorded and calculated.

[0146] 5. Pinhole performance evaluation:

[0147] H1: 5wt% sulfuric acid aqueous solution acid pickling immersion million-hole plate for 2min;

[0148] H2: wet paste twice with double-layer flexible plate containing 5000 100um micropores;

[0149] H3: exposure after 24h;

[0150] H4: development after exposure for 30min;

[0151] H5: stripping with 50℃ 3wt% sodium hydroxide, the stripping time is 1.5 times the minimum stripping time, washed with clean water, and then dried with dust-free paper.

[0152] The number of pinholes is observed under a magnifying glass, and the proportion of pinhole number in total holes is calculated.

[0153] The test results are shown in Table 1.

[0154] Table 1 is the performance test results of dry film resist in Examples 1-9 and Comparative Example 1

[0155] Example 1 and Comparative Example 1 have the same photosensitivity, but Example 1 uses macromolecular photopolymerization monomer 1, which reduces the overall fluidity of the dry film. The pinhole rate of Example 1 is much smaller than that of Comparative Example 1, which is 0.82% vs. 10.22%, while Comparative Example 2 does not add HEMA-IPDI-R-IPDI-HEMA, but uses a conventional dry film resist formula, and its pinhole rate is as high as 15.68%.

[0156] The dry films of the polymerized monomer R with a weight average molecular weight of 2000 g / mol and 3000 g / mol respectively in Examples 2-3 all have good photosensitivity, resolution, adhesion, film stripping ability and small hole plugging rate. With the increase of the molecular weight of the polymerized monomer, the hole plugging rate of the dry film gradually decreases, but the film stripping performance gradually deteriorates, and the flowability in the film forming process also gradually deteriorates. Therefore, the molecular weight of the polymerized monomer R used to prepare the photopolymerizable monomer should not be too high or too low, and is preferably between 1000-3000 g / mol. The basic principle is that the R group is a linear structure, and by adjusting the molecular weight, the distance between the two unsaturated bonds can be adjusted, thereby changing the crosslinking density of the cured light-curable compound. When the molecular weight of R is small, the crosslinking density is high, the alkali development resistance is strong, and thus better resolution and adhesion can be obtained, but the flowability of the material is high. When the molecular weight of R is large, the flowability of the material is reduced, which improves the hole plugging performance. However, the crosslinking density is reduced, the alkali development resistance is weakened, and thus the resolution and adhesion are deteriorated. In summary, the molecular weight of R should be kept within a certain range.

[0157] The dry films of the polymerized monomer poly-caprolactone diol, poly-butylene glycol, poly-ethylene glycol, and poly-1,4-butanediol adipate diol with a weight average molecular weight of 1000 g / mol respectively in Examples 4-7 all have good photosensitivity, resolution, adhesion, film stripping ability and small hole plugging rate.

[0158] Examples 8-10 are to change the proportion of the prepared photopolymerizable monomer in the dry film application. It can be seen that with the decrease of the proportion of the prepared photopolymerizable monomer in the dry film application, the hole plugging defect of the dry film shows an upward trend. However, too high a dosage will affect the resolution and adhesion of the dry film. For example, the resolution and adhesion shown in Example 8 are decreased. Therefore, the proportion of the unsaturated monomer is preferably 40-60%.

[0159] In Comparative Example 3, the resolution and adhesion are significantly deteriorated when the dosage of the photopolymerizable monomer is less than 30 parts. This is because the crosslinking density is washed off by the line part during the development stage. In Comparative Example 4, the film stripping time is long when the dosage of the photopolymerizable monomer is more than 40 parts. This is because the crosslinking density is more dense due to the increase of the dosage of the photopolymerizable monomer, thereby leading to the deterioration of the film stripping ability.

[0160] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A dry film resist comprising the following raw material components in parts by weight: 50-70 parts of an alkali-soluble resin solution, 30-40 parts of a photopolymerization monomer, and 0.2-5 parts of a photoinitiator; The photo-polymerizable monomer is a photo-polymerizable compound containing an unsaturated double bond, which includes HEMA-IPDI-R-IPDI-HEMA, and the specific structural formula is as follows: wherein the weight average molecular weight of R is 1000-3000 g / mol, and R is one of polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone glycol, and poly-1,4-butanediol adipate glycol; the dry film resist has a plug rate of less than 2.2% in a pore size of 100 μm. 2.The dry film resist according to claim 1, comprising the following raw material components in parts by weight: 56-60 parts of an alkali-soluble resin solution, 30-40 parts of a photopolymerization monomer, and 3-5 parts of a photoinitiator. 3.The dry film resist according to claim 1, wherein the mass percentage of HEMA-IPDI-R-IPDI-HEMA in the photopolymerization monomer is 20-100%; the raw materials for preparing the HEMA-IPDI-R-IPDI-HEMA include, in parts by weight, 40-50 parts of hydroxyethyl methacrylate, 60-70 parts of isophorone diisocyanate, 140-160 parts of R, 0.1-0.25 parts of a catalyst, and 30-50 parts of a solvent I; wherein the catalyst is dibutyl tin laurate, and the solvent I is toluene. 4.The dry film resist according to claim 1, wherein the photopolymerization compound containing an unsaturated double bond further comprises a photopolymerization compound containing a vinyl unsaturated group, and the photopolymerization compound containing a vinyl unsaturated group comprises one or more of ethoxylated nonyl phenol acrylate, propoxy ethoxy dimethyl acrylate, ethoxylated bisphenol A dimethyl acrylate, lauryl acrylate, isodecyl acrylate, tetrahydrofurfuryl acrylate, dioxane acrylate, 1,2-benzenedicarboxylic acid-2-hydroxyethyl-2-[(2-acryloyl)oxy]ethyl ester, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, ethoxylated bisphenol A diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glyceryl triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate. 5.The dry film resist according to claim 1, wherein the alkali-soluble resin comprises one or more of a methacrylic resin, a styrene resin, and a phenolic resin; the molecular weight of the alkali-soluble resin is 50000-100000 g / mol; the synthetic monomers of the alkali-soluble resin comprise one or more of methacrylic acid, methyl methacrylate, butyl methacrylate, styrene, ethyl acrylate, and butyl acrylate. 6.The dry film resist according to claim 5, wherein the alkali-soluble resin is selected from one or more of alkali-soluble resin A, alkali-soluble resin B, and alkali-soluble resin C. wherein The synthetic monomers of the alkali-soluble resin A are a combination of methacrylic acid, methyl methacrylate and butyl methacrylate, with a molar ratio of (20-30):(30-50):(30-40); The synthetic monomers of the alkali-soluble resin B are a combination of methacrylic acid, methyl methacrylate, butyl acrylate and styrene, with a molar ratio of (20-30):(30-50):(10-30):(10-20); The synthetic monomers of the alkali-soluble resin C are a combination of methacrylic acid, methyl methacrylate, ethyl acrylate and butyl acrylate, with a molar ratio of (20-30):(40-50):(10-20):(10-30).

7. The dry film resist according to claim 6, wherein the alkali-soluble resin is a combination of the alkali-soluble resin A and the alkali-soluble resin B, with a weight ratio of (4-5):(5-6).

8. The dry film resist according to claim 1, wherein the photoinitiator comprises one or more of benzoin ether, benzophenone and its derivatives, thioxanthone series compounds, anthraquinone and its derivatives, thioxanthone series compounds, hexaarylbiimidazole series compounds. The dry film resist further comprises the following raw material components in parts by weight: 0.5-10 parts of an auxiliary agent and 30-50 parts of a solvent.

9. A method for preparing the dry film resist according to any one of claims 1-8, comprising the following steps: (1) Preparation of the alkali-soluble resin: add butanone into the system, heat and reflux, and then add the mixture of the synthetic monomers of the alkali-soluble resin and the initiator into the system at a constant speed, with a dropping time of 1-4 h, keep warm for 1-2 h, continue to add the mixture of the initiator and butanone, with a dropping time of 20-40 min, and then keep warm for 3-5 h to obtain the alkali-soluble resin, which is ready for use; (2) Preparation of the photopolymerization compound HEMA-IPDI-R-IPDI-HEMA: uniformly mix R and isophorone diisocyanate in a toluene solution, react at 50-70℃ for 1-3 h, then add hydroxyethyl methacrylate containing a catalyst, with a dropping time of 40-80 min, react at 70-80℃ for 3-6 h, and determine the NCO content to be <0.1 wt% to obtain the photopolymerization compound HEMA-IPDI-R-IPDI-HEMA; (3) Mix the alkali-soluble resin, the photopolymerization monomer, the photoinitiator, the auxiliary agent and the solvent to obtain a dry film resist coating solution; (4) Coating and baking the dry film resist coating solution to obtain the dry film resist.

10. Use of the dry film resist according to any one of claims 1-8 and the dry film resist prepared by the method of claim 9 on a flexible circuit board.

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