CN118393814A - Dry film resist and preparation method and application thereof - Google Patents

Abstract

The present invention discloses a dry film resist and a preparation method and application thereof, wherein 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-butylene adipate diol. The dry film resist formed by the combined action of HEMA-IPDI-R-IPDI-HEMA prepared by the present invention and an alkali-soluble polymer resin has reduced fluidity on the surface of a printed circuit board, performs excellently in an aperture of 100 μm, and can improve the plugging performance of the dry film resist.

Description

Dry film resist and its preparation method and application

Technical Field

The invention relates to the technical field of materials for pattern surface photoengraving, and in particular to a dry film resist and a preparation method and application thereof.

Background technique

With the progress and development of science and technology, electronic devices have gradually developed in the direction of being thin and light in recent years, and the size of the printed circuit board patterns carried by them has become smaller and smaller, in order to improve the yield rate of small-sized circuit boards. Therefore, dry film resists are required to have excellent resolution and adhesion at the same time. With the improvement of the precision of printed circuit boards, the number of through holes used to connect wiring layers in printed circuit boards increases, and the diameter of through holes decreases. The wet-pressed dry film is easy to press the dry film into the small holes during the film pressing and exposure process. It is difficult to completely wash off the dry film pressed into the small holes during the development and film stripping stage, resulting in the phenomenon of plugging holes, which makes it impossible to perform subsequent operations such as electroplating on the hole wall, and it is easy to cause the hole wall to have no conductive layer, causing the circuit board to short-circuit. In the existing process, the plugging problem of dry film resist is improved by increasing the adhesion of dry film resist or adjusting the processing technology of the circuit board, but the effect is not good. Therefore, it is very important to develop a dry film resist that has good adhesion to the printed circuit board and is not easy to plug holes.

The prior art, such as the phosphorus-containing polyurethane acrylate oligomer mentioned in patent CN11055663961A, a phosphorus-containing polyurethane acrylate oligomer and its preparation method and application, uses a polyol with three or more functions, forming a cyclic rigid structure, which mainly gives dry film adhesion. Chinese invention patent CN200610082639.4 discloses a dry film resist, which uses a carboxyl-containing adhesive and a photopolymerizable monomer with a specific structure to make the photopolymerizable resin composition contain a free radical polymerization inhibitor. The prepared photopolymerizable resin composition has excellent thermal stability and storage stability, but does not solve the problem of plugging holes in printed circuit boards with small through holes. Chinese invention patent CN201710500105.7 discloses a resin composition and its use. By adjusting the molar ratio of hydrophilic group ethylene oxide (EO) and hydrophobic group propylene oxide (PO) in the photopolymerizable monomer, the obtained resin composition has the characteristics of no pore plugging during film stripping and fast film stripping speed when used as a dry film resist. However, the effect of inhibiting pore plugging is not significant, and there is still a certain scrap rate in mass production.

Summary of the invention

The invention provides a dry film resist and a preparation method and application thereof, so as to solve the technical problem of plugging holes in a printed circuit board when the existing dry film resist is used.

According to one aspect of the present invention, a dry film resist is provided, comprising 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 containing an unsaturated double bond includes HEMA-IPDI-R-IPDI-HEMA, and its structural formula is as follows:

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 polybutylene adipate-1,4-diol.

The plugging rate of the dry film resist in a pore size of 100 μm is less than 2.2%.

Furthermore, the raw material components include the following parts by weight: 56-60 parts of alkali-soluble resin, 30-40 parts of photopolymerizable monomers, and 3-5 parts of photoinitiator.

Furthermore, the mass percentage of the HEMA-IPDI-R-IPDI-HEMA in the photopolymerizable monomer is 20-100%.

Furthermore, the photopolymerizable compound containing unsaturated double bonds also includes a photopolymerizable compound containing vinyl unsaturated groups, and the photopolymerizable compound containing vinyl unsaturated groups includes ethoxy nonylphenol acrylate, propoxy ethoxy dimethacrylate, ethoxy bisphenol A dimethacrylate, lauryl acrylate, isodecyl acrylate, tetrahydrofuran methyl acrylate, dioxolyl acrylate, 1,2-phthalic 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 glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate. One or more.

Furthermore, the alkali-soluble resin includes one or more of methacrylic resin, styrene resin, and phenolic resin;

The molecular weight of the alkali-soluble resin is 50,000-100,000 g/mol.

Furthermore, the synthetic monomers of the alkali-soluble resin include one or more of methacrylic acid, methyl methacrylate, butyl methacrylate, styrene, ethyl acrylate, and butyl acrylate.

Furthermore, 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.

Furthermore, 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.

According to another aspect of the present invention, there is also provided a method for preparing a dry film resist, comprising the following steps:

(1) Preparation of alkali-soluble resin: add butanone into the system, heat to reflux, mix the synthetic monomer of the alkali-soluble resin with the initiator and uniformly drip into the system, the dripping time is 1-4 hours, keep warm for 1-2 hours, continue to drip the mixture of initiator and butanone, the dripping time is 20-40 minutes, and then keep warm for 3-5 hours to obtain the alkali-soluble resin for standby use;

(2) Preparation of photopolymerizable compound HEMA-IPDI-R-IPDI-HEMA: R and isophorone diisocyanate were mixed evenly in a toluene solution, reacted at 50-70°C for 1-3h, and then hydroxyethyl methacrylate containing a catalyst was added dropwise for 40-80min, reacted at 70-80°C for 3-6h, and the NCO content was measured to be <0.1wt%, thereby obtaining HEMA-IPDI-R-IPDI-HEMA;

(3) mixing an alkali-soluble resin, a photopolymerizable monomer, a photoinitiator, an auxiliary agent and a solvent to obtain a dry film resist coating liquid;

(4) The dry film resist coating liquid is coated and baked to obtain a dry film resist.

According to yet another aspect of the present invention, there is provided an application of a dry film resist on a flexible circuit board.

The present invention has the following beneficial effects:

The present invention allows the photopolymerizable monomer HEMA-IPDI-R-IPDI-HEMA to act together with an alkali-soluble polymer resin, so that two carbamate groups in HEMA-IPDI-R-IPDI-HEMA are connected to more than two carboxyl groups in the alkali-soluble polymer resin through "hydrogen bonds". The strength of the "hydrogen bonds" is between the molecular force and the chemical bond, and the strength is relatively large. It can form a "physical cross-linking" similar to a spatial network structure, thereby reducing the static fluidity of the film material. Therefore, the dry film resist formed by the photopolymerizable monomer HEMA-IPDI-R-IPDI-HEMA prepared by the present invention and the alkali-soluble polymer resin has reduced fluidity on the surface of the printed circuit board, and performs excellently in a pore size of 100 μm, which can improve the plugging performance of the dry film resist, and the plugging problem is not likely to occur on the surface of the printed circuit board.

The present invention is different from the phosphorus-containing polyurethane acrylate oligomer mentioned in patent CN11055663961A, a phosphorus-containing polyurethane acrylate oligomer, and its preparation method and application, in that the alcohol used in the synthesis of the patent is a trifunctional or higher polyol, forming a cyclic rigid structure, and thus mainly imparts adhesion to the dry film; while in the photopolymerizable monomer HEMA-IPDI-R-IPDI-HEMA of the present invention, R is a diol with a difunctional structure having a certain molecular weight, and the molecular weight can be adjusted to adjust the distance between the two unsaturated bonds, thereby changing the crosslinking density of the compound after curing; and the use of a difunctional diol structure can make the product have a certain flexibility in the dry film, and during the wet pressing process of the FPC soft board, it can reduce the fluidity while making the flexible circuit board have a good wetting effect, and spread well on the surface of the printed circuit board.

Detailed ways

The following is a detailed description of the embodiments of the present invention, but the present invention can be implemented in many different ways as defined and covered below.

According to an embodiment of the first aspect of the present invention, there is provided a dry film resist, comprising the following raw material components in parts by weight: 50-70 parts of an alkali-soluble resin, 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 containing an unsaturated double bond includes HEMA-IPDI-R-IPDI-HEMA, and its structural formula is as follows:

The weight average molecular weight of R is 1000-3000 g/mol, and R is one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone glycol, and poly(1,4-butylene adipate) glycol.

The present invention allows HEMA-IPDI-R-IPDI-HEMA and an alkali-soluble polymer resin to act together, so that two carbamate groups in HEMA-IPDI-R-IPDI-HEMA are connected with more than two carboxyl groups in the alkali-soluble polymer resin 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 cross-linking" similar to a spatial 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 prepared by the present invention and the alkali-soluble polymer resin has reduced fluidity on the surface of the printed circuit board, which can improve the plugging performance of the dry film resist, and the plugging problem is not likely to occur on the surface of the printed circuit board.

In addition, the weight average molecular weight of R in the photopolymerizable monomer HEMA-IPDI-R-IPDI-HEMA of the present invention is 1000-3000 g/mol. Since the R group is a linear structure, the distance between two unsaturated bonds can be adjusted by adjusting the molecular weight, thereby changing the crosslinking density of the photocurable compound after curing, balancing the fluidity and wettability of the dry film resist, and having a good wetting effect on the printed circuit board while reducing the fluidity, and spreading well on the surface of the printed circuit board.

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

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.

In this embodiment, the dry film resist includes the following raw material components in parts by weight: 56-60 parts of alkali-soluble resin, 30-40 parts of photopolymerizable monomer, and 3-5 parts of photoinitiator.

If the amount of photopolymerizable monomer is less than 30 parts, insufficient resolution will occur, and if it is more than 40 parts, film removal will be difficult.

In this embodiment, the mass percentage of the HEMA-IPDI-R-IPDI-HEMA in the photopolymerizable monomer is 20-100%.

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

In some embodiments, the -NCO content in the HEMA-IPDI-R-IPDI-HEMA is less than 0.1 wt %.

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

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

As a preferred embodiment, the catalyst is dibutyltin laurate, and the solvent I is toluene.

In some embodiments, the preparation method of HEMA-IPDI-R-IPDI-HEMA comprises the following steps: adding R to a reaction kettle, then adding IPDI (isophorone diisocyanate), then adding solvent I and reacting at 50-70°C for 1-3h, then dropping HEMA (hydroxyethyl methacrylate) containing a catalyst for 40-80min, then reacting at 70-80°C for 3-6h, and determining the NCO content to obtain HEMA-IPDI-R-IPDI-HEMA.

As a preferred embodiment, the preparation method of HEMA-IPDI-R-IPDI-HEMA comprises the following steps: adding R to a reactor, then adding IPDI, then adding solvent I and reacting at 60° C. for 2 hours, then dripping HEMA containing a catalyst for 60 minutes, then reacting at 75° C. for 4 hours, and determining the NCO content to obtain HEMA-IPDI-R-IPDI-HEMA.

In this embodiment, the photopolymerizable compound containing unsaturated double bonds also includes a photopolymerizable compound containing vinyl unsaturated groups, and the photopolymerizable compound containing vinyl unsaturated groups includes ethoxy nonylphenol acrylate, lauryl acrylate, propoxyethoxy dimethacrylate, ethoxy bisphenol A dimethacrylate, isodecyl acrylate, tetrahydrofuran methyl acrylate, dioxolane acrylate, 1,2-phthalic 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 glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate. One or more.

In this embodiment, the alkali-soluble resin includes one or more of methacrylic resin, styrene resin, and phenolic resin; and/or the molecular weight of the alkali-soluble resin is 50,000-100,000 g/mol.

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

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

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

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 50,000 g/mol, and a molecular weight distribution of 1.8.

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 50,000 g/mol, and a molecular weight distribution of 1.9.

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.

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

The use of two alkali-soluble resins with a molecular weight of 50,000 g/mol and a photopolymerizable monomer with a molecular weight of 1,000-3,000 g/mol, with the two alkali-soluble resins in a weight ratio of (4-5):(5-6), can optimize the hole plugging problem of the dry film resist under the wet pressing process. The reason is that the low molecular weight photopolymerizable monomer can undergo polymerization on the high molecular weight alkali-soluble resin, and the hydrogen bonding effect of the macromolecular photopolymerizable monomer and the high molecular weight alkali-soluble resin further reduce the fluidity of the dry film, thereby preventing the dry film from flowing into the hole, and the hole plugging performance is further improved.

In some embodiments, the preparation method of 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 and reflux, mixing 300-500 parts by weight of monomer and 0.1-5 parts by weight of initiator and uniformly dripping into the system for 1-4 hours, keeping warm for 1-2 hours, continuing to drip a mixture containing 1-5 parts by weight of initiator and 150-250 parts by weight of solvent II for 20-40 minutes, then keeping warm for 3-5 hours, and finally cooling to 50°C for standby use.

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 and reflux, mixing 400 parts by weight of monomer and 4 parts by weight of initiator and uniformly dripping into the system for 3 hours, keeping warm for 1 hour, continuing to drip a mixture containing 4 parts by weight of initiator and 200 parts by weight of solvent II for 30 minutes, then keeping warm for 4 hours, and finally cooling to 50°C for standby use.

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 and reflux, mixing 400 parts by weight of monomer and 0.8 parts by weight of initiator and uniformly dripping into the system for 3 hours, keeping warm for 1 hour, continuing to drip a mixture containing 4 parts by weight of initiator and 200 parts by weight of solvent II for 30 minutes, then keeping warm for 4 hours, and finally cooling to 50°C for standby use.

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

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, and hexaarylbiimidazole series compounds.

In some embodiments, the photoinitiator includes benzoin ether, benzophenone, thioxanthone, anthraquinone, 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-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, benzyl 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, isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-tert-butylanthraquinone, N,N-dimethylbenzoic acid ethyl ester, dimethylaminoethyl benzoate, N,N-dimethylethanolamine, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-diimidazole, 2,2'-bis(2-bromo-5-methoxybenzene)-4,4',5,5'-tetraphenyldiimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyldiimidazole, bisimidazole, tetraethyl Michler's ketone or more.

In this embodiment, the raw materials of the dry film resist further include 0.5-10 parts of an auxiliary agent and 30-50 parts of a solvent.

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 halogen compound, and a stabilizer.

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

The embodiment of the second aspect of the present invention further provides a method for preparing a dry film resist, comprising the following steps:

(1) Preparation of alkali-soluble resin: add butanone into the system, heat to reflux, mix the synthetic monomer of the alkali-soluble resin with the initiator and uniformly drip into the system, the dripping time is 1-4 hours, keep warm for 1-2 hours, continue to drip the mixture of initiator and butanone, the dripping time is 20-40 minutes, and then keep warm for 3-5 hours to obtain the alkali-soluble resin for standby use;

(2) Preparation of photopolymerizable compound HEMA-IPDI-R-IPDI-HEMA: R and isophorone diisocyanate were mixed evenly in a toluene solution, reacted at 50-70°C for 1-3h, then hydroxyethyl methacrylate containing a catalyst was added dropwise for 40-80min, reacted at 70-80°C for 3-6h, and the NCO content was measured to be less than 0.1wt%, thereby obtaining HEMA-IPDI-R-IPDI-HEMA;

(3) mixing an alkali-soluble resin, a photopolymerizable monomer, a photoinitiator, an auxiliary agent and a solvent to obtain a dry film resist coating liquid;

(4) The dry film resist coating liquid is coated and baked to obtain a dry film resist.

As a preferred embodiment, the viscosity of the dry film resist coating liquid at 25° C. is 200-2000 mPa•s, more preferably 500-1500 mPa•s, and even more preferably 700-1200 mPa•s.

The embodiment of the third aspect of the present application also provides an application of a dry film resist on a flexible circuit board.

The dry film resist applied to the flexible circuit board of the present invention adopts a high molecular weight alkali-soluble resin composed of two different monomers, which can further optimize the hole plugging problem of the dry film resist under the wet pressing process.

The dry film resist applied to the flexible circuit board of the present invention has excellent resolution and adhesion, can reduce the hole plugging problem caused by the wet pressed dry film applied to the FPC after the development process, and performs excellently in the hole diameter of 100 μm.

Example 1

A dry film resist used for a flexible circuit board. The raw materials for preparation are, in percentage by weight: 30 parts of an alkali-soluble resin A, 28 parts of an alkali-soluble resin B, 18 parts of a photopolymerizable monomer 1, 10 parts of a photopolymerizable monomer 2, 5 parts of a photopolymerizable monomer 3, 4 parts of a photopolymerizable monomer 4, 0.2 parts of a photoinitiator 1, 4 parts of a photoinitiator 2, 0.5 parts of an auxiliary agent 1, 0.05 parts of an auxiliary agent 2, 0.01 parts of an auxiliary agent 3, 0.05 parts of an auxiliary agent 4, 1.5 parts of an auxiliary agent 5 and 30 parts of a solvent.

The preparation method of alkali-soluble resin A comprises the following steps: adding 400 parts by weight of butanone into a reaction kettle, heating to 80°C and reflux, mixing 400 parts by weight of monomer and 4 parts by weight of azobisisobutyronitrile and uniformly dripping into the system for 3 hours, keeping warm for 1 hour, continuing to drip a mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone for 30 minutes, keeping warm for 4 hours, and finally cooling to 50°C for standby use.

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

The preparation method of alkali-soluble resin B comprises the following steps: adding 400 parts by weight of butanone into a reaction kettle, heating to 80°C for reflux, mixing 400 parts by weight of monomer and 4 parts by weight of azobisisobutyronitrile and uniformly dripping into the system for 3 hours, keeping warm for 1 hour, continuing to drip a mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone for 30 minutes, keeping warm for 4 hours, and finally cooling to 50°C for standby use.

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

Photopolymerizable monomer 1 is HEMA-IPDI-R-IPDI-HEMA.

Photopolymerizable monomer 2 was ethoxylated bisphenol A dimethacrylate (purchased from Changxing Special Materials (Suzhou) Co., Ltd.);

Photopolymerizable monomer 3 was propoxyethoxy dimethacrylate (purchased from Changxing Special Materials (Suzhou) Co., Ltd.);

Photopolymerizable monomer 4 is ethoxylated nonylphenol acrylate (purchased from Changxing Special Materials (Suzhou) Co., Ltd.).

Photoinitiator 1 is bisimidazole; photoinitiator 2 is tetraethyl Michler's ketone.

The auxiliary agent is a color developer, and auxiliary agent 1 is colorless crystal violet; auxiliary agent 2 is malachite green; auxiliary agent 3 is hydroquinone; auxiliary agent 4 is 5-carboxybenzotriazole; and auxiliary agent 5 is p-toluenesulfonamide.

The solvent is butanone.

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

S1: Preparation of alkali-soluble resin: Add 400 parts by weight of butanone into a reaction kettle, heat to 80°C and reflux, mix 400 parts by weight of monomer and 4 parts by weight of azobisisobutyronitrile and uniformly drip into the system for 3 hours, keep warm for 1 hour, continue to drip a mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone for 30 minutes, then keep warm for 4 hours, and finally cool to 50°C to obtain alkali-soluble resin A for standby use;

Add 400 parts by weight of butanone into the reaction kettle, heat to 80°C and reflux, mix 400 parts by weight of the monomer and 4 parts by weight of azobisisobutyronitrile and uniformly drip into the system, the dripping time is 3 hours, keep warm for 1 hour, continue to drip a mixture containing 4 parts by weight of azobisisobutyronitrile and 200 parts by weight of butanone, the dripping time is 30 minutes, then keep warm for 4 hours, and finally cool to 50°C to obtain alkali-soluble resin B for standby use;

S2: Preparation of photopolymer monomer: Add 150 parts of R into the reactor, then add 66.5 parts of IPDI (isophorone diisocyanate), then add 40 parts of toluene and react at 60°C for 2 hours, then drop 0.135 parts of dibutyltin laurate and 45 parts of HEMA (hydroxyethyl methacrylate) for 60 minutes, then react at 75°C for 4 hours, and measure the -NCO content <0.1wt%, to obtain HEMA-IPDI-R-IPDI-HEMA. Wherein R is polypropylene glycol with a weight average molecular weight of 1000g/mol;

S3: mixing an alkali-soluble resin, a photopolymerizable monomer, a photoinitiator, an auxiliary agent and a solvent to obtain a dry film resist coating liquid;

S4: coating and baking the dry film resist coating liquid to obtain a dry film resist.

Example 2

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are replaced by an equal amount of photopolymerizable monomer 5;

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

Example 3

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are replaced by an equal amount of photopolymerizable monomer 6;

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

Example 4

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are replaced by an equal amount of photopolymerizable monomer 7;

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

Example 5

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are replaced by an equal amount of photopolymerizable monomer 8;

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

Example 6

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are replaced by an equal amount of photopolymerizable monomer 9;

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

Example 7

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are replaced by an equal amount of photopolymerizable monomer 11;

The preparation methods of the photopolymerizable monomer 11 are as follows: R used in the preparation process of the photopolymerizable monomer 1 is replaced with poly(1,4-butylene adipate)diol having a weight average molecular weight of 1000 g/mol.

Example 8

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 is adjusted to 24 parts, and photopolymerizable monomer 2 is adjusted to 7 parts.

Example 9

The difference between this embodiment and embodiment 1 is that the 18 parts of photopolymerizable monomer 1 in embodiment 1 is adjusted to 12 parts.

Example 10

The difference between this embodiment and embodiment 1 is that 18 parts of photopolymerizable monomer 1 in embodiment 1 are adjusted to 6 parts, and photopolymerizable monomer 2 is increased to 22 parts.

Comparative Example 1

The difference between this comparative example and Example 1 is that 18 parts of the photopolymerizable monomer 1 in Example 1 are replaced by an equal amount of the photopolymerizable monomer 12 .

The photopolymerizable monomer 12 is a reaction product of 2 mol of hydroxyethyl acrylate propoxylate and 1 mol of hexamethylene diisocyanate (purchased from Wuxi Chemical Industry Co., Ltd. with a product code of UXR-1200).

The reaction process is:

The difference between this comparative example and Example 1 is that 18 parts of photopolymerizable monomer 1 in Example 1 are eliminated, and photopolymerizable monomer 2 is increased to 28 parts.

Comparative Example 3

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

Comparative Example 4

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

Performance Testing

Test sample preparation:

(1) The prepared dry film resist was coated on a base film (PET), and then dried at 80°C for 1 h. The thickness after drying was 25 μm (excluding the base film);

(2) Then the dry film resist is hot pressed on a 0.0361mm thick FPC flexible copper clad board at 110°C, a pressure of 0.4-0.5MPa, and a conveying speed of 1.5m/min for exposure. The exposure equipment uses parallel light for exposure, a stouffer 41-grid exposure ruler, and a 125×25mm energy grid with an energy of 30-120mJ/cm ² . After exposure, the product is placed for 30 minutes before entering the development process.

(3) Based on the development point of 50%, set the development speed to 0-6m/min, tear off the base film, and place it on the transmission line of a special developer. The equipment is JL-2009XY-I. The temperature is set to 30±1℃, and the pressure is set to 0.14-0.17MPa. The unexposed part is completely washed off. After the development is completed, it can be dried.

1. Photosensitivity evaluation:

Exposure scale: Stouffer41ST exposure scale sensitivity test piece; developer: 1.0±0.2wt% Na ₂ CO ₃ aqueous solution; developing temperature: 30±1℃; developing pressure: 0.14-0.17MPa.

After the development is completed, let it dry, observe the number of remaining segments on the copper-clad laminate exposure scale, read the number of remaining grids on the 41-grid scale line, and use the energy corresponding to the number of remaining grids 16 as its sensitivity. The lower the energy value at the same number of grids, the better the sensitivity.

2. Adhesion ability evaluation:

After the development is completed and the board is dried, an optical microscope is used to observe the residual situation of the pattern on the copper clad laminate after development, and the minimum line of complete, clear, vertical and no debonding is used as the judgment standard.

The film is tested at L/400, with line width/line spacing equal to 10/400 to 40/400. The minimum value retained after the exposure and development process is read out, which is its adhesion ability.

3. Analytical ability evaluation:

After the development is completed, the plate is dried and an optical microscope is used to observe the development of the pattern on the copper clad laminate. The final result or judgment standard is the minimum line width and line spacing with no dry film residue between the lines and a clear vertical projection of the dry film side wall.

With L/S, line width/line spacing equal to 10/10 to 40/40, the minimum value retained after the exposure and development process is read out, which is its resolution.

4. Evaluation of film removal ability:

Defilming solution: 3.0±0.5wt% NaOH aqueous solution; Defilming temperature: 50±5℃.

After development, the time is counted from the moment the copper plate enters the film stripping solution until the dry film on the copper plate is completely peeled off. This period of time is recorded as the film stripping time.

Repeat the above steps 3 times, record and calculate the average film removal time.

5. Evaluation of plugging performance:

H1: 5wt% sulfuric acid aqueous solution pickling and soaking the 10,000-hole plate for 2 min;

H2: wet-laminate a double-layer flexible board containing 5000 100um micropores in two times;

H3: Exposure after 24 hours of exposure;

H4: After exposure, leave it for 30 minutes before developing;

H5: Use 3wt% sodium hydroxide at 50℃ to fade the film. The fading time is 1.5 times the minimum fading time. Wash with clean water and wipe dry with dust-free paper.

Observe the number of plugged holes under a magnifying glass and calculate the proportion of plugged holes to the total holes.

The test results are shown in Table 1.

Table 1 shows the test results of dry film resist properties in Examples 1-9 and Comparative Example 1

The sensitivity of Example 1 and Comparative Example 1 is consistent, but Example 1 uses a macromolecular photopolymer monomer 1, which reduces the overall fluidity of the dry film. The plugging rate of Example 1 is 0.82%, which is much smaller than the plugging rate of Comparative Example 1 of 10.22%. Comparative Example 2 does not add HEMA-IPDI-R-IPDI-HEMA, but uses a conventional dry film resist formula, and its plugging rate is as high as 15.68%.

Examples 2-3 respectively use polymerized monomers R with a weight average molecular weight of 2000 g/mol and 3000 g/mol, and their dry films have good sensitivity, resolution, adhesion, film-fading ability and small plugging rate. As the molecular weight of the polymerized monomer increases, the plugging rate of the dry film gradually decreases, but the film-fading performance gradually deteriorates, and the fluidity during the film formation 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. By adjusting the molecular weight, the distance between the two unsaturated bonds can be adjusted, thereby changing the crosslinking density of the photocurable compound after curing. The R molecular weight is small, the crosslinking density is high, and the alkali-resistant developing ability is strong, so that better resolution and adhesion can be obtained, but the material has higher fluidity; the R molecular weight is large, the material fluidity is reduced, and the plugging performance is improved; but the crosslinking density is reduced, and the alkali-resistant developing ability is weakened, resulting in degradation of the resolution and adhesion ability. In summary, the molecular weight of R should be kept within a certain range.

Examples 4-7 respectively use polymer monomers of 1000 g/mol weight average molecular weight, namely polycaprolactone diol, polybutylene glycol, polyethylene glycol, and polybutylene adipate-1,4-diol, and their dry films have good sensitivity, resolution, adhesion, film removal ability and small plugging rate.

Examples 8-10 are for changing the proportion of the prepared photopolymerizable monomer in the dry film application. It can be seen that as the proportion of the prepared photopolymerizable monomer in the dry film application decreases, the poor plugging of the dry film shows an upward trend, and too high a dosage will affect the parsing and adhesion ability of the dry film. For example, the parsing and adhesion ability shown in Example 8 are reduced. Therefore, it is preferred that the proportion of the unsaturated monomer is 40-60%.

In comparative example 3, after the amount of photopolymerizable monomer used is less than 30 parts, it can be seen that the analytical adhesion ability is significantly deteriorated. This is because the cross-linking density is partially eluted by the line during the development stage. In comparative example 4, after the amount of photopolymerizable monomer used is more than 40 parts, the film removal time is longer. This is because the amount of photopolymerizable monomer used is increased and the cross-linking density is denser, which leads to the deterioration of the film removal ability.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. The dry film resist is characterized by comprising the following raw material components in parts by weight: 50-70 parts of alkali-soluble resin solution, 30-40 parts of photopolymerization monomer and 0.2-5 parts of photoinitiator;

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, and the specific structural formula is as follows:

；

Wherein the weight average molecular weight of R is 1000-3000g/mol, and R is one of polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone glycol and poly (1, 4-butylene glycol adipate);

the dry film resist has a plug hole 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 alkali-soluble resin solution, 30-40 parts of photopolymerization monomer and 3-5 parts of photoinitiator.

3. The dry film resist according to claim 1, wherein the mass percentage of HEMA-IPDI-R-IPDI-HEMA in the photopolymerizable monomer is 20 to 100%.

4. The dry film resist of claim 1, wherein the unsaturated double bond-containing photopolymerizable compound further comprises a vinyl unsaturated group-containing photopolymerizable compound comprising ethoxynonylphenol acrylate, propoxyethoxydimethacrylate, ethoxybisphenol a dimethacrylate, lauryl acrylate, isodecyl acrylate, tetrahydrofuranyl acrylate, dioxolyl acrylate, 2-hydroxyethyl-2- [ (2-acryl) oxy ] ethyl 1, 2-phthalate; polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, ethoxylated bisphenol A diacrylate, 1, 6-hexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated glycerol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate.

5. The dry film resist of claim 1, wherein the alkali-soluble resin comprises one or more of methacrylic resin, styrenic resin, phenolic resin;

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

6. The dry film resist according to claim 5, wherein the synthetic monomer of the alkali-soluble resin comprises one or more of methacrylic acid, methyl methacrylate, butyl methacrylate, styrene, ethyl acrylate, butyl acrylate.

7. The dry film resist of claim 1, wherein the photoinitiator comprises one or more of benzoin ethers, benzophenones and derivatives thereof, thioxanthone series compounds, anthraquinones and derivatives thereof, thioxanthone series compounds, hexaarylbisimidazole series compounds.

8. The dry film resist according to claim 1, further comprising the following raw material components in parts by weight: 0.5-10 parts of auxiliary agent and 30-50 parts of solvent.

9. A method of preparing a dry film resist according to claim 1, comprising the steps of:

(1) Preparing alkali-soluble resin: butanone is added into the system, heated and refluxed, the synthetic monomer of the alkali-soluble resin and the initiator are mixed and then dripped into the system at a constant speed, the dripping time is 1-4h, the heat preservation is carried out for 1-2h, the mixture of the initiator and the butanone is continuously dripped, the dripping time is 20-40min, and then the heat preservation is carried out for 3-5h, thus obtaining the alkali-soluble resin for standby;

(2) Preparation of the photopolymerized compound HEMA-IPDI-R-IPDI-HEMA: uniformly mixing R and isophorone diisocyanate in toluene solution, reacting for 1-3 hours at 50-70 ℃, then dropwise adding hydroxyethyl methacrylate containing a catalyst for 40-80min, reacting for 3-6 hours at 70-80 ℃, and determining NCO content to be less than 0.1wt%, thus obtaining a photopolymerization compound HEMA-IPDI-R-IPDI-HEMA;

(3) Mixing alkali-soluble resin, a photopolymerization monomer, a photoinitiator, an auxiliary agent and a solvent to obtain a dry film resist coating liquid;

(4) And (3) coating and baking the dry film resist coating liquid to obtain the dry film resist.

10. Use of a dry film resist as claimed in any one of claims 1 to 8 on flexible circuit boards.