CN118377190A - Photosensitive resin composite and photosensitive solder mask dry film - Google Patents

Abstract

The invention discloses a photosensitive resin composite and a photosensitive solder resist dry film, belonging to the technical field of dry film photoresists. The photosensitive resin composite comprises the following components: A: acidic unsaturated resin, 40-70 parts by weight; B: epoxy resin: 20-45 parts by weight; C: filler and pigment: 5-25 parts by weight; D: (methyl) acrylate, 0-15 parts by weight; the total weight of components A-D is 100 parts by weight; and E: photoinitiator, the amount of photoinitiator is 0.1-5% of the total weight of components A-D; in component A, the acidic unsaturated resin comprises an acidic unsaturated fluorine-containing epoxy resin. The photosensitive resin composite can be etched into a fine circuit pattern by UV light curing and alkaline aqueous solution, and the solder resist layer prepared finally has Dk＜3.4, Df＜0.02.

Description

Photosensitive resin composite and photosensitive solder mask dry film

Technical Field

The invention belongs to the technical field of dry film photoresists, and particularly relates to a photosensitive resin composite and a photosensitive solder resist dry film made from the photosensitive resin composite.

Background technique

Printed circuit boards (PCBs) are carriers and integrated bodies of microelectronic components. The solder mask (also known as solder resist) is a protective film formed on the surface of the PCB using a special processing technology to prevent the circuits on the PCB from contacting other metals, solder or conductive objects and causing short circuits. It plays the role of insulation and protection of the copper layer. It can selectively expose the copper PAD, IC, etc. required for welding, save solder, and prevent various scratches and scratches on the PCB during manufacturing and transportation. It can also resist various harsh environments and chemical erosions, and extend the service life. Therefore, PCBs are almost always covered with solder resist during manufacturing.

The solder mask is an organic dielectric material that generates parasitic capacitance when an electromagnetic field is induced. The dielectric (dielectric constant Dk) and loss (loss factor Df) characteristics of the dielectric material will affect the electromagnetic transmission of the outer layer circuit: the electromagnetic signal transmission rate is inversely proportional to √(D_k), and the transmission loss is proportional to √(D_k) and Df. The higher the frequency of the electromagnetic wave, the more serious the dielectric effect. At present, the Dk and Df of the solder mask are about 3.9-4.5 and 0.02 respectively. For high-speed PCBs, such as IC substrates and PCBs for high-frequency and ultra-high-frequency applications, dielectric materials with lower Dk/Df are required as solder masks.

The solder resist layer material can be liquid solder resist ink or film solder resist dry film. The former is printed on the PCB board by screen printing and other methods, and then cured by heating or light radiation. Since the liquid form has a certain impact on the environment due to the release of VOC, good ventilation conditions and waste gas treatment steps are required; while the film solder resist material only needs to be simply heated and bonded on the PCB board, and then exposed (or directly imaged by laser) and developed through a patterned mask, the solder resist coating can be prepared on the PCB, which is simpler in process and more convenient to use. Therefore, advanced PCB processing requires dry film photosensitive solder resist materials.

As mentioned above, the current solder mask material is not suitable for high-frequency and ultra-high-frequency PCBs and IC substrates due to its high Dk and Df characteristics. At the same time, liquid solder mask ink has the disadvantages of solvent volatilization and strong odor stimulation during use.

Summary of the invention

In view of this, the present invention provides a photosensitive resin composite and a solder resist dry film with lower Dk and Df. The solder resist dry film can be bonded to a fine PCB electronic circuit board by hot pressing, and a solder resist pattern is formed through mask exposure (or laser direct imaging) and development, and then post-baked and heated to become a solder resist layer with excellent performance, or a protective film layer of a fine PCB electronic circuit board.

In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

A photosensitive resin composite comprises the following components:

A: acidic unsaturated resin, 40-70 parts by weight, preferably 45-65 parts by weight;

B: epoxy resin, 20-45 parts by weight, preferably 25-40 parts by weight;

C: micron filler and pigment, 5-25 parts by weight, preferably 6-20 parts by weight, wherein the amount of filler can be 0 parts by weight;

D: (meth)acrylate, 0-15 parts by weight, preferably 0-10 parts by weight;

The total weight of components A-D is 100 parts by weight;

In addition, it also includes E: a photoinitiator, wherein the amount of the photoinitiator is 0.1-5%, preferably 0.5-3%, of the total weight of components A-D.

In component A of the photosensitive resin composite, the acidic unsaturated resin (a) is an acidic unsaturated fluorinated epoxy resin (a1), which is prepared by modifying the fluorinated epoxy resin shown below as a raw material, wherein the chemical formula of F-B contains a phenylene group substituted with a 1,3-meta or 1,4-para position.

Acidic unsaturated resin a, such as fluorine-free epoxy resin as raw material, such as bisphenol A epoxy resin, novolac epoxy resin, biphenyl type and epoxy resin containing naphthalene ring skeleton, can be made into acidic unsaturated fluorine-containing epoxy resin as acidic photosensitive resin by reacting with unsaturated acid and acid anhydride, which is used as liquid and solid photosensitive imaging material of PCB board. The D _k of acidic photosensitive resin modified by these epoxy resins is relatively high, so the photosensitive solder mask material composed of them as the main body has obvious adverse effect on the transmission of high-frequency electromagnetic signals. Compounds containing fluorine atoms have a lower dielectric constant D _k , such as polytetrafluoroethylene fluorocarbon resin (PTFE) has a very low D _k , which has been used to prepare PCB boards with extremely high D _k requirements, but PTFE has low surface energy and weak bonding with conductive metal materials; and PTFE is not a photosensitive resin and cannot be used to prepare photosensitive solder mask. Fluorinated long-chain alkane compounds are often used to reduce the dielectric constant of materials, but they have low Tg, insufficient mechanical strength and heat resistance, and cannot meet the high performance requirements of the solder mask layer.

The inventors have found that the fluorine content of the above-mentioned fluorine-containing epoxy resin is high, ranging from about 25.4% (mass percentage) of the fluorinated bisphenol A epoxy resin with the lowest fluorine content to 45.5% (mass percentage) of fluorophenyl bis(hexafluoroisopropyl) glycidyl ether. Their chemical structure is similar to that of bisphenol A epoxy resin, and the glass transition temperature Tg after curing is greater than 100°C, and they have good heat resistance and mechanical properties, reflecting the characteristics of rigid resins. Replacing ordinary epoxy resin with fluorine-containing epoxy resin can take into account the performance requirements of high Tg, high heat resistance and low dielectric constant required by the solder mask, and achieve the purpose of preparing the photosensitive solder mask material required for high-performance electronic circuit boards for high-frequency electromagnetic signal transmission.

The epoxy equivalent value of the above acidic unsaturated fluorine-containing epoxy resin a1 can be 220-1000 g/mol. The higher the epoxy equivalent value, the larger the molecular weight of the epoxy resin and the better the film-forming property; but when the epoxy equivalent value is too large, after modification with acid and anhydride, the photosensitivity of the acidic resin becomes weaker and the developing property becomes worse.

The epoxy equivalent value of epoxy resin is the mass of epoxy resin corresponding to each mol of epoxy functional group. It can be determined by the hydrochloric acid-acetone method according to the GB/T1677-2008 standard method; the mass percentage of fluorine can be determined by elemental analysis, and the glass transition temperature Tg can be determined by a dynamic mechanical properties analyzer (DMA) or thermal analysis methods such as differential scanning calorimeter (DSC). The Tg of the cured product is related to the curing agent, and the Tg of the cured product using methyltetrahydrophthalic anhydride (MTPA) as the curing agent shall prevail.

The fluorinated epoxy resin reacts with an unsaturated acid and then reacts with an acid anhydride to obtain an acidic unsaturated fluorinated epoxy resin a1. Unsaturated acids include: (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, etc. (meth) acrylic acid represents methacrylic acid or acrylic acid. Taking acrylic acid modification as an example, acrylic acid reacts with the epoxy functional group of the fluorinated epoxy resin to produce acrylate and hydroxyl groups. The latter can then react with an acid anhydride to introduce carboxyl groups into the resin to obtain an acidic unsaturated fluorinated epoxy resin a1 containing acryloyloxy and carboxyl groups. If a dibasic unsaturated acid such as maleic acid is used for modification, the resulting resin will have both carboxyl groups and carbon-carbon unsaturated groups, and no further modification with anhydride is required. The fluorinated epoxy resin itself contains a small amount of hydroxyl groups. If it is directly esterified by reacting with an acid anhydride, the carboxyl groups produced by the reaction will continue to react with the epoxy functional groups, making the product structure complex and polymerized, and may also cause the resin to gel. The acid anhydride that reacts with the hydroxyl group after the reaction of the fluorinated epoxy resin and the unsaturated acid includes aromatic and alicyclic polyanhydrides, such as dibasic anhydrides such as phthalic anhydride, (methyl) tetrahydrophthalic anhydride, (methyl) hexahydrophthalic anhydride, (methyl) dioxic anhydride, and maleic anhydride, and tertiary or tetrabasic anhydrides such as trimellitic anhydride, pyromellitic dianhydride, diphenyl ether tetraacid dianhydride, and biphenyl tetraacid dianhydride. The acid unsaturated fluorinated epoxy resin a1 modified with dibasic acid anhydride has a high acid equivalent value and a low carboxyl concentration, while the acid unsaturated fluorinated epoxy resin a1 modified with polyacid anhydride has a low acid equivalent value and a low carboxyl concentration. Therefore, the acid equivalent value of the acid unsaturated fluorinated epoxy resin a1 can be adjusted by a combination of different acid anhydrides. The molecular weight of the acidic unsaturated fluorine-containing epoxy resin a1 reacted with the unsaturated acid and the acid anhydride is generally 500-3000 g/mol. By using an epoxy resin with a higher molecular weight, an acidic unsaturated fluorine-containing resin with a higher molecular weight can be obtained.

The reaction of fluorinated epoxy resin and unsaturated acid can refer to the reaction method similar to that of common epoxy resin, for example, the reaction conditions of bisphenol A epoxy resin and acrylic acid. The reaction usually requires catalysis of organic base, acid or other catalyst, and the reaction is stirred at 80-110°C for several hours. See the following implementation examples. The reaction of anhydride and acid-modified epoxy resin can be carried out at the same or slightly lower temperature. Generally, it is necessary to add an appropriate amount of solvent. Ether solvents with a boiling point of 60-180°C, preferably 60-130°C, such as tetrahydrofuran (THF), dipropyl ether, dibutyl ether; ketone solvents, such as acetone, butanone, cyclohexanone, etc.; alcohol and ester solvents, such as ethanol, isopropanol, butanol, butyl acetate, dimethyl carbonate, dibutyl carbonate, etc. High boiling point solvents, such as DMF, NMP, DMSO, etc., are preferably used in combination with other low boiling point solvents. The acid equivalent value of the pure acidic unsaturated fluorine-containing epoxy resin a1 after the solvent is removed is 190-600 g/mol, preferably 210-550 g/mol. If it is lower or higher than this range, that is, the acidity of the resin is too high or too low, the photosensitivity and developability of the later photosensitive solder resist dry film is not good, which is not conducive to the etching of fine patterns. The acid equivalent value of the resin can be determined by alkali titration.

The Tg of the acidic unsaturated fluorine-containing epoxy resin a1 is greater than 100° C., and the mass ratio of fluorine in the solvent-free neat acidic unsaturated resin a is greater than 25%.

The acidic unsaturated resin a can also include acidic unsaturated epoxy resins (a2) other than the acidic unsaturated fluorine-containing epoxy resin a1. They can be prepared by modifying the aforementioned fluorine-free epoxy resin with unsaturated acid and anhydride in a similar way to the preparation method of a1. The raw materials can be the same except that the epoxy resin does not contain fluorine. A solvent can be added when preparing a2. The molecular weight of the acidic unsaturated epoxy resin a2 is 600-3000g/mol. Similar to a1, the epoxy resin used in a2 has a glass transition temperature Tg higher than 100°C after being cured with methyltetrahydrophthalic anhydride (MTPA), and a modulus greater than 3GPa, reflecting the characteristics of a rigid resin.

The acidic unsaturated epoxy resin a2 can also be replaced by a carboxyl-containing (meth) acrylic resin (a3), which is prepared by reacting a hydroxyl-containing (meth) acrylic ester with an acid anhydride, for example, by reacting hydroxyethyl (meth) acrylate, hydroxyethyl (meth) acrylate, etc. with the aforementioned polyacid anhydride. A3 may contain a solvent. The molecular weight of a3 is 200-1000 g/mol, and the Tg after photocuring is greater than 100°C. In the acidic unsaturated resin a without the solvent, the acid equivalent value Va of the acidic (meth) acrylic resin is greater than 210 g/mol. In the solvent-free acidic unsaturated resin a, the mass ratio of the acidic unsaturated fluorine-containing epoxy resin a1 is greater than 60%, and the acidic (meth) acrylic resin is the balance.

In the net acidic unsaturated resin a after the solvent is removed, the mass ratio of a2 or a3 is less than 40%, preferably less than 35%, or even not added at all. The photosensitive resin composite uses the acidic unsaturated epoxy resin a2 and the acidic unsaturated fluorine-containing epoxy resin a1 to adjust the photosensitivity, development characteristics and properties of the cured product of the photosensitive resin composite, including Tg, mechanical properties and dielectric properties.

In the pure photosensitive resin composite excluding the solvent, the mass ratio of the acidic unsaturated resin a to the total mass of components A-D is greater than 40% and less than 70%, preferably in the range of 45%-65%, so as to take into account the performance of the cured product.

The Tg of the epoxy resin of component B in the photosensitive resin composite is greater than 100°C. The epoxy resin undergoes a cross-linking reaction with the carboxyl group in the photosensitive resin composite, which can improve the heat resistance and adhesion of the cured product and consume the carboxyl group of the acidic unsaturated resin a. The epoxy resin suitable for component B of the present invention includes the fluorinated epoxy resin in the preparation of the acidic unsaturated fluorinated epoxy resin a1, as well as fluorine-free bisphenol A type, bisphenol F type, bisphenol S type, phenolic type, biphenyl type, epoxy resin containing aromatic rings such as naphthalene skeleton, heterocyclic type, alicyclic type, halogen-substituted epoxy resin, and difunctional, trifunctional glycidyl ether, glycidyl ester type epoxy resin, etc. From the perspective of mechanical properties, heat resistance and dielectric properties, fluorinated epoxy resins and bisphenol A type, bisphenol F type, phenolic type, biphenyl type, naphthalene skeleton type epoxy resin, hydantoin epoxy resin, glycidyl ether type epoxy resin, and combinations thereof are preferred. The epoxy equivalent value of the epoxy resin is 70-600 g/mol, preferably 80-400 g/mol, and the molecular weight is between 200-2000. It can be a monofunctional, difunctional or even tetrafunctional epoxy compound, that is, each resin molecule contains 1-4 epoxy functional groups. Within this range, the thermal reactivity of the photosensitive resin composite is high, the crosslinking of the epoxy resin is sufficient, and the density, hardness and heat resistance of the cured product can be taken into account. After photocuring and further thermal curing with the epoxy resin, the Tg of the photosensitive resin composite will be higher than the Tg of the acidic unsaturated resin of component A and the epoxy resin of component B after curing, and it has good heat resistance. The mass ratio of epoxy resin to the total mass of components A-D in the net photosensitive resin composite excluding solvent is at least 20%, but up to 45%. Adding too much will affect the exposure and developability. A more accurate dosage can be determined according to performance requirements. Preferably, the mass ratio of epoxy resin to the total mass of components A-D in the solvent-free photosensitive resin composite is between 25-40%.

Component C in the photosensitive resin composite is a nanofiller and a pigment. It should be noted that, for the case where no filler is needed, the amount of filler can be 0, and the amount of filler and pigment added can be freely selected according to the specific situation of the resin. The solder mask needs to have a color mark, and pigments or fillers need to be added. The color of some inorganic fillers themselves can take into account the use of pigments. Adding inorganic fillers can improve the mechanical and heat resistance of the cured product, but inorganic fillers usually have a higher dielectric constant. Inorganic nanofillers with lower dielectric constants are preferred, such as silicon dioxide, nitrogen carbide, boron nitride, mica powder, kaolin, etc., among which boron nitride has the lowest dielectric constant, about 1.6. The Dk of silicon dioxide is related to its preparation method. The Dk of nano silicon dioxide is about 2.0, but nano silicon dioxide has strong aggregation and poor dispersibility, and will significantly increase the viscosity of the resin composite. Micron-scale inorganic fillers are preferred. Large-particle fillers are easier to disperse. The particle size is 0.5-5um, preferably 1-5um, which can take into account the coating process and photosensitivity of the resin composite and the fineness of the photolithographic pattern. Surface modification of fillers can improve their dispersibility in the resin and the fluidity and developability of the photosensitive resin composite. Fillers and pigments of different chemical compositions and particle sizes can be combined and used in combination. Those skilled in the art can select these fillers, fillers and their combinations according to performance requirements to take into account the dielectric properties, photosensitivity, developability and performance of the photosensitive solder mask dry film after curing. The mass ratio of fillers and pigments to the total mass of component AD in the pure photosensitive resin composite after solvent removal is 5%-25%, preferably 6-20%. Adding more fillers and pigments, such as more than 30%, will affect the photosensitivity and etching performance. In the present invention, fillers and pigments are preferably spherical _SiO2 with a particle size of 0.5-1.5um and pigments commonly used in the field.

Component D in the photosensitive resin composite is (meth)acrylate. Adding an appropriate amount of (meth)acrylate to the photosensitive resin composite can improve the photocuring activity, enhance the photosensitivity, adjust the fluidity of the composite and the performance of the cured product, and therefore, it plays the role of an active diluent. Suitable (meth)acrylates are preferably multifunctional (meth)acrylates, which have high photocuring activity, good mechanical properties and heat resistance. 2-4 functional (meth)acrylates can be selected, such as ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, etc., preferably tri- or tetra-functional methacrylates, which have high activity and better mechanical properties. The amount of (meth)acrylate added to the total mass of components A-D in the resin composite is preferably less than 15%, preferably 0-10%, and may not be added.

Component E in the photosensitive resin composite is a photoinitiator. The photoinitiator provides photoactivity to the photosensitive resin composite. Under the action of ultraviolet light or visible light, the photoinitiator generates highly active free radicals, which trigger the polymerization reaction of the unsaturated groups in the photosensitive resin composite, crosslinking the resin molecules in the exposed area, while the unexposed area remains in an unpolymerized soluble state. The photoinitiator that can be used is a free radical photoinitiator that is sensitive to 280-410nm light waves radiated by mercury lamps, UV-LEDs, lasers, pulsed flashes, etc., including but not limited to various types of commercially available aromatic alkyl ketones, α-hydroxy ketones, acylphosphine oxides and their derivatives, various oxime esters, etc., such as the oxime esters of the OXE series commonly known as 1173, 184, 2959, 907, 369, 819, TPO, OXE-1 and OXE-2, and also includes benzophenone and substituted benzophenone, substituted thioxanthone, coumarin, xanthone-type hydrogen abstraction photosensitizers. The amount of photoinitiator and photosensitizer added is 0.1-5% of the total mass of components A-D, preferably 0.5-3%.

During preparation, a proper amount of solvent can be added to the photosensitive resin composite to adjust the viscosity, and to facilitate the full mixing and dissolution of the raw material components, so as to facilitate coating on the supporting base film. The boiling point of the solvent is 60-180°C, and preferably 60-120°C ether solvents, such as tetrahydrofuran (THF), dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether; ketone solvents, such as acetone, butanone, cyclohexanone, etc.; aromatic hydrocarbon solvents, such as toluene, xylene; alcohol and ester solvents, such as ethanol, isopropanol, butanol, butyl acetate, dimethyl carbonate, dibutyl carbonate, ethylene glycol ethyl ether acetate, etc. These solvents can be used alone or in combination, and the amount used is based on the appropriate viscosity of the photosensitive resin composite, convenient coating and removal.

Other additives: A proper amount of additives can be added to the photosensitive resin composite as needed, including thermal initiators that can improve the thermal curing activity of epoxy resin, such as tertiary amines, boron trifluoride amine complexes, substituted imidazoles, dicyandiamide, dihydrazides, etc., and defoamers, leveling aids, antioxidant stabilizers, etc. can also be added to adjust the performance. Thermal curing allows the (meth) acrylate to fully react and the epoxy resin to cure with acid. The curing temperature can be in the range of 150-220°C and the time can be 40-90 minutes. Suitable curing conditions can be determined by infrared spectroscopy and the mechanical properties of the cured product. Those skilled in the art can refer to the thermal curing conditions and processes of the photosensitive ink and photosensitive dry film of the PCB board, and can select additives based on experience or information.

The solvent volatilization temperature in the photosensitive composite resin compound should be lower than 120°C to reduce the influence of high temperature on the resin performance. The time for removing the solvent should be controlled within 12 minutes, preferably within 8 minutes. The temperature and time for removing the solvent are related to the selected solvent. The better conditions for removing the solvent are 60-100°C and within 8 minutes. In order to accelerate the removal of the solvent, a hot air drying tunnel or a blast oven can be used, or a ventilated infrared heating furnace can be used. If the coating is relatively thin, such as the dry film thickness within 15 microns, under better hot air and temperature conditions, the solvent can be basically removed within 5 minutes, and the residual amount is within 10%.

The photosensitive resin composite can be etched into a fine circuit pattern through UV light curing and alkaline aqueous solution, and after further UV light curing and heat treatment, the prepared solder resist layer has Dk<3.4, Df<0.02, and can withstand the soldering temperature.

A photosensitive solder resist dry film comprises a transparent PET carrier base film, a photosensitive resin compound coated on the transparent PET carrier base film, and a dark protective film attached to the photosensitive resin compound layer.

The preparation method of the above-mentioned photosensitive solder resist dry film is as follows: the components of the photosensitive resin composite are mixed with a solvent, stirred evenly to form a fluid, coatable slurry fluid, applied to a transparent PET carrier base film, and the solvent is evaporated at a temperature of 60-120°C to form a photosensitive solder resist dry film. In order to facilitate storage, transportation, and use, a layer of dark PE film or PP plastic film must be attached to these photosensitive films. That is, first apply a uniform, coatable slurry photosensitive resin composite to a transparent PET carrier base film, and after the solvent is quickly evaporated at a temperature of 60-120°C, a thin dark protective film is attached to form a photosensitive solder resist dry film or a photosensitive protective dry film with a support film on the lower surface and a protective film on the upper surface.

The above coating can be a single coating or continuous coating in a roll-to-roll manner on the coating line. After removing the solvent and applying the protective film, it can be rolled into a roll or cut into sheets of the required size. In order to maintain a good performance state, the photosensitive solder mask dry film should be stored at a lower temperature, such as -10-10℃, and in a dry state away from light.

In order to make the filler uniformly dispersed in the resin composition, the filler can be firstly mixed with the components of the composite except the photoinitiator by means of a solvent, and then the remaining components are added to prepare a uniform, coatable slurry photosensitive resin composite. Forced mixing equipment can be used, including grinders, high-speed dispersers, sand mills, etc. to grind the filler-resin mixture. Preferably, the filler is firstly uniformly dispersed with an acidic unsaturated resin or an epoxy resin and a reactive diluent, and then mixed with the remaining components to form a uniform, coatable slurry.

The thickness of the photosensitive solder resist dry film after removing the solvent is 10-60um, preferably 15-40um, to meet the opening requirements of fine circuits. A variety of coating methods and equipment can be used to apply the uniform paste-like composite resin composition to the carrier film, including coating methods such as blade coating, roller coating, slit coating, and screen printing.

The thickness of the transparent PET carrier base film is 30-60um, and the thickness of the protective film is 20-60um.

The protective coating prepared by the photosensitive solder resist dry film after photolithography, UV curing and heat treatment has Dk<3.4, Df<0.02, and excellent heat resistance and chemical resistance.

The photosensitive resin composite is coated on a transparent PET carrier base film, and after drying, the PE protective film is affixed thereto to prepare a photosensitive solder resist dry film with a support body that can be rolled up, stored at low temperatures and transported.

Detailed ways

In order to allow those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below.

Example

Fluorinated epoxy resin: Hexafluorobisphenol A epoxy resin (F-E) is a commercially available product, phenyl bis(hexafluoroisopropyl) epoxy resin (FB) and fluorophenyl bis(hexafluoroisopropyl) epoxy resin (F-FB) were provided by the College of Polymer Science and Engineering, Sichuan University. Their chemical structures are shown below:

In Table 1, phenylbis(hexafluoroisopropyl) epoxy resin (F-B) contains two structures, a para isomer (F-B-1) and a meta isomer (F-B-2), and the ratio of the two is approximately F-B-1/F-B-2=1/9.

The epoxy equivalent values and Tg data of the three resins after curing are listed in Table 1. The Tg data are measured by DMA method after curing at 120°C, 160°C and 200°C for 2h, respectively, with the ratio of fluorinated epoxy resin to MTPA curing agent being 1:1.05.

Table 1, fluorinated epoxy resin

F-E F-B F-FB Epoxy equivalent g/mol 250 310 320 Tg℃ 145 130 138

The non-fluorine-containing epoxy resin is a commercially available o-cresol epoxy resin (referred to as novolac epoxy), the epoxy equivalent value of which is distributed at 200 g/mol and the molecular weight is about 300-600.

The filler is spherical SiO ₂ with a particle size of 2 μm produced by Jiangsu Lianrui New Materials Co., Ltd., and the pigment is commercial phthalocyanine green.

Photoinitiators: TPO and 907, both are products of Jiuri Chemical Co., Ltd.

Active diluent: ethylene glycol di(meth)acrylate, a product of Changxing Chemical Company.

The following is an example of the synthesis of the acidic unsaturated resin (a) of component A (all in parts by mass or mass %):

Resin Synthesis Example 1: 220 parts of hexafluorobisphenol A epoxy resin F-E, 70 parts of acrylic acid, 0.5 parts of hydroquinone and 3 parts of triphenylphosphine are added to a flask equipped with a thermometer, a mechanical stirrer and a condenser, and stirring is turned on. After heating to 100°C for 6 hours, the temperature is lowered to 70°C, 200 parts of butanone and 190 parts of trimellitic anhydride are added, and the reaction is stirred for 5 hours to obtain an acidic unsaturated fluorine-containing epoxy resin with an acid equivalent value of 240 g/mol and a non-volatile content of 70%, which is hereinafter referred to as F-E-A.

Resin Synthesis Example 2: 310 parts of phenylbis(hexafluoroisopropyl)epoxy resin F-B, 80 parts of methacrylic acid, 0.5 parts of hydroquinone and 3 parts of triphenylphosphine were added to a flask equipped with a thermometer, a mechanical stirrer and a condenser, stirring was started, the temperature was raised to 100 degrees and reacted for 6 hours, then the temperature was lowered to 70 degrees, 200 parts of butanone and 140 parts of phthalic anhydride were added, and the reaction was stirred for 5 hours to obtain an acidic unsaturated fluorine-containing epoxy resin with an acid equivalent value of 530 g/mol and a non-volatile content of 74%, recorded as F-B-MA.

Resin Synthesis Example 3: Similarly, 320 parts of fluorophenyl bis(hexafluoroisopropyl) epoxy resin F-FB are used instead of phenyl bis(hexafluoroisopropyl) epoxy resin, 70 parts of acrylic acid and 190 parts of trimellitic anhydride are used instead of phthalic anhydride, and the rest is the same as Resin Synthesis Example 1 to obtain an acidic unsaturated fluorine-containing epoxy resin with an acid equivalent value of 290 g/mol and a non-volatile content of 76%, which is recorded as F-FB-A.

Resin Synthesis Example 4: Using 200 parts of o-cresol epoxy resin, 70 parts of acrylic acid and 190 parts of trimellitic anhydride, similar to the method of Resin Synthesis Example 1, an acidic unsaturated epoxy resin with an acid equivalent value of 230 g/mol and a non-volatile content of 75% was prepared, recorded as Ph-A.

Resin Synthesis Example 5: 300 parts of pentaerythritol triacrylate, 155 parts of methyltetrahydrophthalic anhydride, 100 parts of butanone, and 0.1 part of hydroquinone were added into a flask equipped with a thermometer, a mechanical stirrer, and a condenser. Stirring was started, the temperature was raised to 70° C., and the reaction was stirred for 6 hours to obtain an acid-modified methacrylic resin with an acid equivalent value of 450 g/mol and a non-volatile content of 84%, recorded as 4H-A.

Description of implementation method

Sample preparation of photosensitive solder resist dry film: The composition of photosensitive resin composite examples 1-4 and comparative examples 1, 2 and 3 is shown in Table 2, wherein each component is 100% solid content by weight; wherein, except for comparative example 3, each example also adds 1% of the total solid content in Table 2 of photoinitiator TPO and 1% of photoinitiator 907, and 0.5% of thermal initiator boron trifluoride ethylamine to catalyze the curing of epoxy resin; comparative example 3 only adds 1% of thermal initiator, without photoinitiator, to compare photosensitivity. The acidic unsaturated resin and filler of component A of each embodiment are mixed with an appropriate amount of ethylene glycol ethyl ether acetate, and then stirred and mixed into a uniform slurry using a high-speed mixing device; then, the initiator, epoxy resin and active diluent and other components are added according to the composition ratio in Table 2, and stirred for 30 minutes in a dark place to obtain a photosensitive slurry. The slurry was coated onto a 35um transparent PET carrier base film using a slit coater, the solvent was removed by blowing hot air at 100°C for 8 minutes, and a 20um thick PE film was attached to obtain a 20um thick photosensitive solder resist dry film with a carrier film and a protective film, which was stored away from light and at a low temperature of 0°C.

Photolithography evaluation: peel off the PE protective film on the photosensitive solder resist dry film, and laminate the exposed photosensitive solder resist dry film to a 30um thick copper foil in a vacuum laminating machine (vacuum for 30 seconds, 80°C and 0.7MPa); take out the sample, place a film with a line width/line spacing of 40um/40um on the PET film of the photosensitive solder resist dry film, and irradiate with a UV lamp with an exposure energy of 150mJ/ ^cm2 ; leave it for 30 minutes after exposure, remove the pattern film, peel off the PET carrier base film, spray it with a 1% mass concentration _NaCO3 aqueous solution at 0.2MPa for 2 minutes, blow dry the moisture with hot air, and check it with a digital microscope. If 40um/40um lines can be etched, it will be marked as √, otherwise it will be marked as ×.

Adhesion evaluation: Cut the copper foil and the developed patterned samples into 70×50mm strips, irradiate with 1J/ ^cm2 UV lamp, rinse with pure water, put in a 100℃ blast oven for 10 minutes, and then heat treat in a 200℃ oven for about 90 minutes. Float the sample on a 288℃ tin bath with the ball surface facing upwards to observe whether the pattern layer peels off or bubbles. If there is no abnormal phenomenon such as peeling or bubbling, it is marked as qualified for adhesion and heat resistance, recorded as √; if there is abnormal phenomenon such as peeling, falling off or bubbling, it is marked as unqualified, recorded as ×.

Physical property measurement and evaluation: For the samples used for physical property testing, the photosensitive solder resist dry film was irradiated with a UV lamp, with an exposure energy of 150mJ/ ^cm2 . After exposure, it was left for 30 minutes, the PE film was peeled off, and a 1% _NaCO3 aqueous solution was sprayed at 0.2MPa for 2 minutes, and then irradiated with a UV lamp of 1J/ ^cm2 , and placed in a blast oven at 100℃ for 10 minutes, and then heat treated in an oven at 200℃ for about 90 minutes. The samples were measured for storage modulus E at room temperature using a dynamic mechanical properties tester (DMA), with a heating rate of 10℃/min. Storage modulus E greater than 3.2GPa was marked as √, otherwise it was marked as ×. The dielectric properties of the samples at room temperature and in the range of 100Hz-5MHz were tested using a Concept 50 broadband dielectric anti-relaxation spectrometer, and the dielectric constant _Dk at 1MHz was recorded. The dielectric loss was marked as √ if it was less than 0.02, otherwise it was marked as ×. The electrical insulation is tested with a DDJ-50KV withstand voltage breakdown tester produced by Beijing Guance Precision Instruments. If the insulation resistance is greater than 1x10 ¹³ Ω, it is marked as √, otherwise it is marked as ×.

Table 2. Composition of photosensitive resin composites and properties of solder mask dry films

The above example results are shown in Table 2. The photosensitive solder resist dry film of the present invention meets the requirements of low dielectric constant, low dielectric loss, high electrical insulation, adhesion and resistance to soldering temperature, and can be used for photolithography to prepare fine patterns. According to these examples, technicians in this field can further combine different components, which may make the solder resist dry film have a lower D _k and obtain other better properties. Under comparative conditions, the photosensitive solder resist dry film with conventional epoxy resin as the raw material, the heat resistance and voltage breakdown resistance of Example 1 are excellent, but the D _k is very high and the photosensitivity is weak, so that the dielectric impedance is high and fine patterns cannot be etched. Example 2 increases the photosensitivity. Although fine patterns can be photoetched, the dielectric constant of the cured layer material is very high and cannot meet the requirements of low dielectric constant; while the heat-curing solder resist dry film, Example 3, has no photochemical reactivity and cannot be photoetched.

The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims (10)

1. A photosensitive resin composite, characterized in that it comprises the following components: A: acidic unsaturated resin, 40-70 parts by weight; B: epoxy resin, 20-45 parts by weight; C: fillers and pigments, 5-25 parts by weight; wherein the minimum amount of fillers is 0 parts by weight; D: (meth)acrylate, 0-15 parts by weight; The total weight of components A-D is 100 parts by weight; In addition, it also includes E: a photoinitiator, wherein the amount of the photoinitiator is 0.1-5% of the total weight of components A-D; In component A, the acidic unsaturated resin includes an acidic unsaturated fluorine-containing epoxy resin, which is prepared by modifying the fluorine-containing epoxy resin represented by F-E, F-B, or F-FB as a raw material; 2. A photosensitive resin composite according to claim 1, characterized in that it comprises the following components: A: acidic unsaturated resin, 45-65 parts by weight; B: epoxy resin: 25-40 parts by weight; C: fillers and pigments: 6-20 parts by weight; D: (meth)acrylate: 0-10 parts by weight; The total weight of components A-D is 100 parts by weight; In addition, the amount of the photoinitiator is 0.5-3% of the total weight of components A-D. 3. A photosensitive resin composite according to claim 1, characterized in that the epoxy equivalent value of the acidic unsaturated fluorine-containing epoxy resin is 220-1000 g/mol, and the acid equivalent value is 190-600 g/mol, preferably 210-550 g/mol. 4. A photosensitive resin composite according to claim 1, characterized in that the acidic unsaturated fluorine-containing epoxy resin is prepared by reacting the fluorine-containing epoxy resin with an unsaturated acid as raw materials, and if there is no carboxyl group in the resin product obtained after the reaction, it is further modified with anhydride to introduce a carboxyl group into the resin, and the unsaturated acid is selected from (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid; The acid anhydride is selected from the dibasic anhydride of phthalic anhydride, (methyl)tetrahydrophthalic anhydride, (methyl)hexahydrophthalic anhydride, (methyl)dihydrophthalic anhydride, maleic anhydride, or the polybasic anhydride of trimellitic anhydride, pyromellitic dianhydride, diphenyl ether tetrahydrophthalic anhydride, biphenyl tetrahydrophthalic anhydride, preferably a combination of different dibasic anhydrides and polybasic anhydrides. 5. A photosensitive resin composite according to claim 4, characterized in that the acidic unsaturated resin further comprises an acidic unsaturated epoxy resin or (meth) acrylic resin accounting for 0-40% by mass of component A; The acidic unsaturated epoxy resin is prepared by modifying a fluorine-free epoxy resin with an unsaturated acid and anhydride, and has a molecular weight of 600-3000 g/mol; The (meth) acrylic resin is prepared by reacting a hydroxyl-containing (meth) acrylic ester with an acid anhydride, has a molecular weight of 200-1000 g/mol, and a Tg after photocuring greater than 100° C. The hydroxyl-containing (meth) acrylic ester is selected from hydroxyethyl (meth) acrylate and hydroxyethyl (meth) acrylate, and the acid anhydride is selected from trimellitic anhydride, pyromellitic dianhydride, diphenyl ether tetracarboxylic dianhydride, and biphenyl tetracarboxylic dianhydride. 6. A photosensitive resin composite according to claim 1, characterized in that, in component B, the Tg of the epoxy resin is greater than 100°C, the epoxy equivalent value of the epoxy resin is 70-600 g/mol, preferably 80-400 g/mol, and the molecular weight is between 200-2000; The epoxy resin is selected from the group consisting of fluorine-containing epoxy resins, fluorine-free bisphenol A type, bisphenol F type, bisphenol S type, phenolic type, biphenyl type, naphthalene skeleton type epoxy resins, heterocyclic type, alicyclic type, halogen-substituted epoxy resins, and difunctional, trifunctional glycidyl ether type, glycidyl ester type epoxy resins, preferably at least one of the fluorine-containing epoxy resins, bisphenol A type, bisphenol F type, phenolic type, biphenyl type, naphthalene skeleton type epoxy resins, hydantoin epoxy resins, and glycidyl ether type epoxy resins shown in F-E, F-B, and F-FB. 7. A photosensitive resin composite as claimed in claim 1, characterized in that the filler and pigment are micron-sized inorganic fillers with their own colors, or a combination of micron-sized inorganic fillers and pigments such as silicon dioxide, nitrogen carbide, boron nitride, mica powder, and kaolin; The filler is preferably spherical silica, and the particle size of the inorganic filler is 0.5-1.5 μm, preferably 1-5 μm. 8. A photosensitive resin composite as claimed in claim 1, characterized in that in component D, the (meth)acrylate is selected from ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. 2-4 functional (meth)acrylate. 9. A photosensitive solder resist dry film, characterized in that it comprises a transparent PET carrier base film, a photosensitive resin composite layer formed by drying the photosensitive resin composite according to any one of claims 1 to 8 coated on the transparent PET carrier base film, and a dark protective film attached to the photosensitive resin composite layer; The thickness of the photosensitive resin composite layer is 10-60um, preferably 15-40um; The thickness of the transparent PET carrier base film is 30-60um; The thickness of the dark protective film is 20-60um. 10. The method for preparing the photosensitive solder resist film according to claim 9, characterized in that it comprises the following steps: The raw material components of the photosensitive resin composite are mixed with a solvent and stirred evenly to form a slurry fluid that is fluid and can be applied; Then the slurry fluid is coated onto a transparent PET carrier base film, and the solvent is evaporated to form a photosensitive solder resist dry film; A dark protective film is applied on the photosensitive solder resist dry film; The solvent is selected from one or more of tetrahydrofuran, dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, acetone, butanone, cyclohexanone, toluene, xylene, ethanol, isopropanol, butanol, butyl acetate, dimethyl carbonate, dibutyl carbonate, and ethylene glycol ethyl ether acetate, and the boiling point of the solvent is 60-180° C., preferably 60-120° C.