Photosensitive resin composition, photosensitive dry film and circuit board

Abstract

The invention belongs to the technical field of membrane materials. The invention discloses a photosensitive resin composition. The photosensitive resin composition comprises epoxy acrylic resin, a photoinitiator, a thermal curing agent and a functional monomer, in the photosensitive resin composition, the mole number of-NCO groups in the functional monomer is a, the mole number of hydroxyl groups in the epoxy acrylic resin is b, the mole number of carboxyl groups in the epoxy acrylic resin is c, the mole number of epoxy groups in the thermal curing agent is d, the mole number of amino groups in the thermal curing agent is e, and b + c + d < = a + e. The invention further discloses the photosensitive dry film. The invention further discloses a circuit board. A film layer formed by curing the photosensitive resin composition in the application has relatively good heat resistance and bending resistance, and has relatively high reliability and relatively wide application scenarios.

Description

Technical Field

[0001] The present application belongs to the technical field of film materials, and in particular relates to a photosensitive resin composition, a photosensitive dry film and a circuit board. Background Art

[0002] In the process of wave soldering and reflow soldering, it is usually necessary to apply flux (i.e., flux, including liquid and gaseous flux and solid solder paste) to remove the oxide layer on the surface of the components to be soldered and improve the soldering performance. When applying the flux, the solder mask layer on the surface of the PCB (printed circuit board) will also be coated with flux.

[0003] During the soldering process, the flux melts, and the acidic components in its formula, such as dicarboxylic acid, special carboxylic acid and organic halide, are released, corroding the solder mask, causing it to swell or even dissolve to varying degrees, resulting in blistering, delamination or film breakage, etc. At this point, it is necessary to rework and reset the solder mask or scrap the PCB board, which seriously reduces production efficiency and causes waste.

[0004] In order to avoid the above situation, it is necessary to improve the flux resistance of the solder mask (acid resistance and solvent resistance at high temperature (265-288°C)). Epoxy resin or oxetane resin is generally added to the conventional solder mask as a thermosetting component. During the thermosetting process, the ring-opening reaction of the epoxy / oxetane group will be accompanied by the formation of hydroxyl groups. The hydroxyl group has a certain water absorption capacity, which leads to a decrease in the high temperature resistance and solvent resistance of the solder mask. In the prior art, amino resins or blocked isocyanates are usually added to the solder mask to consume hydroxyl groups to improve the heat resistance of the solder mask, thereby improving the flux resistance. However, amino resins and blocked isocyanates will reduce the bending resistance of the solder mask, causing the solder mask to deform and crack easily, which limits the application of solder masks in IC substrates and rigid-flex boards. Summary of the invention

[0005] The embodiment of the present application provides a photosensitive resin composition, and the film layer formed by curing the photosensitive resin composition has good heat resistance and good bending resistance and good reliability.

[0006] One aspect of an embodiment of the present application provides a photosensitive resin composition, which includes an epoxy acrylic resin, a photoinitiator, a thermal curing agent and a functional monomer; the functional monomer is a blocked isocyanate curing agent containing a vinyl group; in the photosensitive resin composition, the molar number of -NCO groups in the functional monomer is a, the molar number of hydroxyl groups in the epoxy acrylic resin is b, the molar number of carboxyl groups in the epoxy acrylic resin is c, the molar number of epoxy groups in the thermal curing agent is d, and the molar number of amino groups in the thermal curing agent is e, satisfying b+c+d≤a+e.

[0007] Furthermore, the functional monomer is prepared from a vinyl-containing isocyanate and a capping agent; the capping agent includes at least one of a phenol capping agent, a lactam capping agent, an active methylene capping agent, an alcohol capping agent, an oxime capping agent, a thiol capping agent, an amide capping agent, an imide capping agent, an amine capping agent or a pyrazole capping agent.

[0008] Furthermore, the deblocking temperature of the functional monomer is greater than or equal to 95°C and less than or equal to 150°C.

[0009] Furthermore, the deblocking temperature of the functional monomer is greater than or equal to 120° C. and less than or equal to 140° C.

[0010] Furthermore, the vinyl-containing isocyanate is (CH2=CH) s -Y-(NCO) q or (CH2=C(CH3)) s -Y-(NCO) q At least one of, wherein q is greater than or equal to 1, n is greater than or equal to 1, and the Y group includes at least one of a substituted or unsubstituted carbon chain group, an aliphatic ring group, an aromatic ring group or an oxygen-containing group.

[0011] Furthermore, the epoxy acrylic resin is an alkali-soluble epoxy acrylic resin.

[0012] Furthermore, the acid value of the alkali-soluble epoxy acrylic resin is 45 to 80 mgKOH / g, and the weight average molecular weight of the epoxy acrylic resin is 10,000 to 30,000.

[0013] Furthermore, the photosensitive resin composition further includes a urethanization catalyst, and the added amount of the urethanization catalyst is 0.1 wt % to 1 wt % of the functional monomer.

[0014] Furthermore, the urethanization catalyst includes at least one of a tin-based catalyst, a metal chloride, a metal acetylacetonate, a metal sulfate, an amine compound or an amine salt.

[0015] Furthermore, the amount of the urethanization catalyst added is 0.3 wt % to 0.6 wt % of the functional monomer.

[0016] Furthermore, the photosensitive resin composition also includes a reactive diluent, and the reactive diluent is at least one of the reactive diluents containing at least one vinyl group.

[0017] Furthermore, the reactive diluent does not contain an ethoxy group or a propoxy group.

[0018] Further, the photoinitiator includes at least one of a cleavage-type free radical initiator and a hydrogen abstraction-type free radical initiator.

[0019] Furthermore, the cleavage-type free radical initiator includes at least one of α-hydroxyketone derivative initiators, α-aminoketone derivative initiators, acylphosphine oxide photoinitiators or oxime ester initiators, and the hydrogen abstraction-type free radical initiator includes at least one of benzophenone and its derivative initiators, thioxanthone and its derivative initiators, anthraquinone and its derivative initiators or titanocene initiators.

[0020] Furthermore, the photoinitiator includes at least one of an acylphosphine oxide initiator or an oxime ester photopolymerization initiator.

[0021] Further, the thermal curing agent includes at least one of an isocyanate compound, a blocked isocyanate compound, an amino resin, a benzoxazine resin, a carbodiimide resin, a cyclocarbonate compound, an epoxy compound, a multifunctional oxetane compound or an episulfide resin.

[0022] Further, the thermal curing agent includes at least one of an epoxy compound, a multifunctional oxetane compound or an amino resin.

[0023] Furthermore, the weight ratio of the epoxy compound to the amino resin is (2-4):(1-4).

[0024] Furthermore, the photosensitive resin composition includes, by weight, 100 parts of epoxy acrylic resin, 0.1 to 5 parts of photoinitiator, 30 to 60 parts of thermal curing agent, 1 to 5 parts of functional monomer and 0 to 20 parts of active diluent.

[0025] A second aspect of the embodiments of the present application provides a photosensitive dry film, which is made from the aforementioned photosensitive resin composition.

[0026] A third aspect of the embodiments of the present application provides a circuit board, the circuit board comprising a film layer after the above-mentioned photosensitive dry film is processed.

[0027] A vinyl-containing blocked isocyanate curing agent is added to the photosensitive resin composition in the present application, so that the photosensitive dry film formed by curing the photosensitive resin composition can have high heat resistance and flux resistance at high temperatures without reducing the curvature of the photosensitive dry film, thereby improving the reliability of the photosensitive dry film. DETAILED DESCRIPTION

[0028] In order to make the technical scheme of the present application better understood by the personnel in the field, the technical scheme in the specific implementation mode of the present application is described clearly and completely below. In the present application, unless otherwise specified, the molecular weights recorded are all weight average molecular weights (Mw), and the ratios or percentages between the substances recorded are all weight ratios or weight percentages.

[0029] The embodiment of the present application provides a photosensitive resin composition, which includes epoxy acrylic resin, photoinitiator, thermosetting agent and functional monomer, wherein the functional monomer is a vinyl-containing blocked isocyanate curing agent. In the photosensitive resin composition, the molar number of -NCO groups in the functional monomer is a, the molar number of hydroxyl groups in the epoxy acrylic resin is b, the molar number of carboxyl groups in the epoxy acrylic resin is c, the molar number of epoxy groups in the thermosetting agent is d, and the molar number of amino groups in the thermosetting agent is e, satisfying b+c+d≤a+e. The photosensitive resin composition in the present application can be mainly used to prepare solder resist layers on components such as PCBs. In the present application, epoxy acrylic resin is the main component in the composition, and epoxy acrylic resin is used as the main thermosetting component. During the thermosetting process, the epoxy groups in the epoxy acrylic resin undergo a ring-opening reaction, and hydroxyl groups are continuously generated as the ring-opening reaction proceeds. These generated hydroxyl groups cause a certain degree of decrease in the water resistance and high temperature resistance of the composition, thereby reducing the water resistance and high temperature resistance of the solder resist layer formed by the photosensitive resin composition. In the present application, the blocked isocyanate curing agent containing vinyl is used as the functional monomer, and the functional monomer contains both vinyl and blocked isocyanate. Under a relatively low temperature environment, the closed isocyanate group can stably exist. During the heat curing process, the blocked isocyanate in the functional monomer is unblocked and releases the isocyanate group (-NCO group), which can react with the hydroxyl group present in the composition system and the hydroxyl group (-OH group) produced during the ring opening process of the epoxy group during the heat curing process, and can consume these hydroxyls as soon as possible and form a new cross-linked network. The isocyanate group produced by unblocking in the functional monomer can solve the problem of the water resistance and high temperature resistance of the composition and solder mask layer brought by the generation of hydroxyl groups in the heat curing, and the isocyanate group can increase the purpose of the cross-linking point between the chains after the reaction of the hydroxyl group, and increase the segment length in the cross-linked network. In addition, the functional monomer also contains vinyl, and the vinyl can be connected to the macromolecular chain of epoxy acrylic resin etc. by chemical bonds during the photocuring reaction, which can effectively increase the segment length in the cross-linked network, and give the photo-cross-linked network with better perturbability. The vinyl-containing blocked isocyanate functional monomer not only combines the effects of the vinyl monomer and the blocked isocyanate alone, but the vinyl-containing blocked isocyanate can also bridge the photopolymerization network and the thermal cross-linking network by means of double bonds and the reaction between isocyanate and hydroxyl groups, giving the composition unique heat resistance, water solvent resistance and flexural resistance. In addition to excellent heat resistance, water resistance and solvent resistance, the composition with the addition of functional monomers also has very good flexural resistance. In the photosensitive resin composition, the molar number of -NCO groups in the functional monomer is a, the molar number of hydroxyl groups in the epoxy acrylic resin is b, the molar number of carboxyl groups in the epoxy acrylic resin is c, the molar number of epoxy groups in the thermal curing agent is d, and the molar number of amino groups in the thermal curing agent is e, satisfying b+c+d≤a+e.The relationship between the number of -NCO moles in 1g of functional monomer and the molecular weight is, -NCO moles (a) = isocyanate functionality / molecular weight of functional monomer; the relationship between the number of carboxyl moles in 1g of alkali-soluble resin and the acid value is, carboxyl moles (c) = resin acid value / (1000 × potassium hydroxide molar mass); the relationship between the number of epoxy moles in 1g of epoxy resin and the epoxy equivalent is, epoxy moles (d) = 1 / (100 × epoxy equivalent); the relationship between the number of amino moles in 1g of amino resin and the weight-average molecular weight of amino resin is, amino moles (e) = amino functionality / weight-average molecular weight of amino resin. In addition, (1.2 × 10. -3 )≤a≤(5.0×10 -3 ), (0.8×10 -3 )≤b≤(4.0×10 -3 ), (0.8×10 -3 )≤c≤(1.4×10 -3 ), (2.5×10 -3 )≤d≤(6.7×10 -3 ), (7.7×10 -3 )≤e≤(10.4×10 -3 ). Through the above-mentioned limitation on the functional monomer, the amount of the functional monomer added can satisfy that after the functional monomer is unblocked, the hydroxyl group, carboxyl group in the composition system and the hydroxyl group generated during the ring opening of the epoxy group during the thermal curing process can be basically completely reacted by the amino group in the thermal curing agent and the -NCO group generated after the functional monomer is unblocked. The photoinitiator can absorb energy of the corresponding wavelength in the ultraviolet light region or the visible light region, generate free radicals or cations, etc., thereby initiating the polymerization reaction of the epoxy acrylic resin and the functional monomer to form a cross-linked network structure. The thermal curing agent can assist the epoxy acrylic resin and the functional monomer in the thermal curing reaction, improve the overall heat resistance of the cured product, and enhance the adhesion between the component materials.

[0030] As an optional implementation, the functional monomer is prepared from a vinyl-containing isocyanate and a capping agent; the capping agent includes at least one of a phenolic capping agent, a lactam capping agent, an active methylene capping agent, an alcohol capping agent, an oxime capping agent, a thiol capping agent, an amide capping agent, an imide capping agent, an amine capping agent or a pyrazole capping agent. The above-mentioned capping agent is selected in the functional monomer, which can not only make the functional monomer have good stability at a relatively low temperature and will not be unblocked, but also make the functional monomer unblocked when the epoxy acrylic resin undergoes a ring-opening reaction, so that the isocyanate group can react with the hydroxyl group generated by the ring-opening of the epoxy acrylic resin and consume the hydroxyl group to the maximum extent, thereby improving the water resistance and high temperature resistance of the final soldering layer.

[0031] As an optional embodiment, the unsealing temperature of the functional monomer is greater than or equal to 95°C and less than or equal to 150°C. Generally speaking, the preheating and baking temperature during the production process of the solder mask is approximately between 75°C and 95°C, and the maturation temperature is approximately between 150°C and 160°C. When the unsealing temperature of the functional monomer is within the range of 95°C to 150°C, the functional monomer can remain stable during the preheating and baking stage, and can be quickly unsealed during the maturation stage and can react quickly with the hydroxyl group generated during the ring-opening reaction of the epoxy acrylic resin, consuming the generated hydroxyl group and avoiding the degradation of the performance of the solder mask by the hydroxyl group. Furthermore, the unsealing temperature of the functional monomer is greater than or equal to 120°C and less than or equal to 140°C.

[0032] As an optional embodiment, the vinyl-containing isocyanate is (CH2=CH)sY-(NCO) q or (CH2=C(CH3))sY-(NCO) q At least one of, wherein s is a natural number greater than or equal to 1, q is a natural number greater than or equal to 1, and the Y group includes at least one of a substituted or unsubstituted carbon chain group, an aliphatic ring group, an aromatic ring group or an oxygen-containing group. Exemplarily, the oxygen-containing group can be an ester group, an ether group, a ketone group, etc., s can be 1, 2 or 3, and q can be 1, 2 or 3. Specifically, the Y group can be at least one of Y1 or Y2 or COO-Y1 or Y2-COO-Y1 or OCO-Y1 or Y2-OCO-Y1 or CONH-Y1 or Y2-CONH-Y1 or Y2-O-Y1 or O-Y1. Y1 and Y2 can be independently selected from -(CH x (CH3) y ) n -、-(CH x (C2H5) y ) n -、-(CH x (C3H7) y ) n -、-(CH x (C4H9) y ) n -、-(CH2CH x (CH3) y O) n -、-(CH2CH x (C2H5) y O) n -、-(CH2CH x (C3H7) y O) n -、-(CH2CH x (C4H9) y O) n -、-(CH2CH2O)r -C6H4-(CH2CH2O) t -、-(CH2CH2O) r -C6H4-(CH2CH2O) t -、-(CH2CH2O) r -C6H4-C(CH3)2-C6H4-(CH2CH2O) t -, -CH2-adamantane-CH2- or -CH2-C6H 10 At least one of -CH2-, x can be 0, 1 or 2, x+y=2, n, r and t are natural numbers greater than or equal to 1. Among them, -C3H7- can be n-propyl or isopropyl; -C4H9- can be n-butyl, isobutyl, sec-butyl or tert-butyl. As an optional embodiment, the epoxy acrylic resin is an alkali-soluble epoxy acrylic resin. Specifically, at least one of an o-cresol alkali-soluble epoxy acrylic resin or a biphenyl alkali-soluble epoxy acrylic resin can be selected.

[0033] As an optional embodiment, the acid value of the alkali-soluble epoxy acrylic resin is 45-80 mgKOH / g, and the weight average molecular weight of the epoxy acrylic resin is 10,000-30,000. The acid value of the alkali-soluble epoxy acrylic resin affects the speed of development and whether residual glue is produced, and the molecular weight of the alkali-soluble epoxy acrylic resin affects the film-forming property and touch dryness of the composition. When the acid value of the alkali-soluble epoxy acrylic resin is within the range of 45 mgKOH / g to 80 mgKOH / g, it can not only improve the development effect, avoid the problems of poor development, residual glue and incomplete development, but also avoid excessive development, resulting in line width and line spacing deviation from the standard value. Furthermore, the present application adopts a technical solution of using a low weight average molecular weight low acid value resin (low molecular weight means a weight average molecular weight Mw of 10000-15000, and low acid value means an acid value of 45-55 mgKOH / g) and a high weight average molecular weight high acid value resin (high molecular weight means a weight average molecular weight Mw of 24000-30000, and high acid value means an acid value of 70-80 mgKOH / g). The overall weight average molecular weight of the resin combination obtained after compounding the low weight average molecular weight low acid value resin and the high weight average molecular weight high acid value resin is 10000-30000, and the acid value is 45-80 mgKOH / g. The resin combination obtained after compounding is used to obtain a composition with moderate development time and good touch drying. Specifically, the alkali-soluble epoxy acrylic resin can be selected from at least one of the o-cresol alkali-soluble epoxy acrylic resins. For example, the alkali-soluble epoxy acrylic resin may be CCR4959HW and CCR-1235 produced by Nippon Kayaku Co., Ltd., PR-3000 and PR-300CP produced by Showa Denko K.K., and the like.

[0034] As an optional embodiment, the photosensitive resin composition further includes a reactive diluent, wherein the reactive diluent is a reactive diluent having a vinyl functional group, and may be at least one of a monofunctional reactive diluent, a bifunctional reactive diluent, a trifunctional reactive diluent, or a multifunctional reactive diluent. Preferably, the reactive diluent does not contain an ethoxy group or a propoxy group. Preferably, the glass transition temperature of the reactive diluent is from -10°C to 80°C. The monofunctional reactive diluent can be selected from (meth)acrylamide, hydroxymethyl (meth)acrylamide, methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, butoxymethoxymethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, (meth)acrylic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, crotonic acid, 2-acrylamide-2-methylpropane sulfonic acid, tert-butyl acrylamide sulfonic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl At least one of (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, glycerol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate or a semi-(meth)acrylate of a phthalic acid derivative. The bifunctional reactive diluent may be selected from at least one of tricyclodecane dimethanol diacrylate, propylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, or 1,6-hexanediol di(meth)propionate. The trifunctional reactive diluent may be selected from at least one of trimethylolpropane tri(meth)acrylate, propoxy-modified trimethylolpropane tri(methacrylate), tri(2-hydroxyethyl)isocyanuric acid triacrylate, or pentaerythritol triacrylate. The multifunctional reactive diluent may be selected from at least one of di-trimethylolpropane tetraacrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, or dipentaerythritol hexa(meth)acrylate. In addition, it should be noted that in the above-mentioned active diluent, "(meth)acrylate" refers to both "acrylate" and "methacrylate", "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and "(meth)acryloyloxy" refers to both "acryloyloxy" and "methacryloyloxy", and other components involving "(meth)" are also similar.

[0035] As an optional embodiment, the photoinitiator includes at least one of a cleavage-type free radical initiator and a hydrogen abstraction-type free radical initiator. Further, the cleavage-type free radical initiator includes at least one of an α-hydroxyketone derivative initiator, an α-aminoketone derivative initiator, an acylphosphine oxide initiator or an oxime ester initiator, and the hydrogen abstraction-type free radical initiator includes at least one of benzophenone and its derivative initiators, thioxanthone and its derivative initiators, anthraquinone and its derivative initiators or a titanocene initiator. Exemplarily, the α-hydroxyketone derivative initiator can be 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-[4-(2-hydroxy)-phenyl]-3-hydroxy-2-methyl-1-propanone-1-one, and the commercially available products can be Omnirad 184, Omnirad 1173, etc. manufactured by IGM Resins. The α-aminoketone derivative initiator may be 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinylbenzylphenyl)butanone, 2-p-methylbenzyl-2-dimethylamino-1-(4-morpholinylphenyl)-1-butanone, etc., and commercially available products may be Omnirad 907, Omnirad 369, Omnirad 379, etc. manufactured by IGM Resins. The acylphosphine oxide initiator may be 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc., and commercially available products may be Omnirad TPO, Omnirad 819, Omnirad TPO-L, etc. manufactured by IGM Resins. Oxime ester initiators may be 1,8-bis[9-ethyl-6-nitro-9H-carbazole-3-yl]-, 1,8-bis(O-acetyl oxime), 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyl oxime), etc., and commercially available products may be OXE-01 and OXE-02 manufactured by BASF and NCI-831 and N-1919 manufactured by ADEKA CORPORATION, etc. Thioxanthone and its derivative initiators may be 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythioxanthone, etc., and commercially available products may be ITX, DETX, etc. The titanocene initiator can be bis(cyclopentadienyl)-diphenyltitanium, bis(cyclopentadienyl)-titanium dichloride, bis(cyclopentadienyl)-bis(2,3,4,5,6-pentafluorophenyl)titanium, bis(cyclopentadienyl)-bis(2,6,-difluoro-3-(pyrrol-1-yl)phenyl)titanium, etc. Commercially available products include Omnirad 784 manufactured by IGM Resins BV.

[0036] As an optional embodiment, the photoinitiator includes an acylphosphine oxide initiator and an oxime ester initiator. The absorption wavelength of the photolysis product of the acylphosphine oxide photoinitiator can be shifted to a short wavelength, has a photobleaching effect, is conducive to the transmission of ultraviolet rays, and the photolysis product is colorless and does not yellow. Oxime ester initiators have good stability and high sensitivity. Acylphosphine oxide initiators combined with oxime ester initiators can significantly increase the photopolymerization rate and shorten the curing time. Acylphosphine oxide initiators combined with oxime ester photopolymerization initiators can significantly increase the photopolymerization rate and shorten the curing time. Furthermore, the weight ratio of acylphosphine oxide initiators to oxime ester initiators is (1-4): (0-1).

[0037] As an optional embodiment, the thermal curing agent includes at least one of an isocyanate compound, a blocked isocyanate compound, an amino resin, a benzoxazine resin, a carbodiimide resin, a cyclocarbonate compound, an epoxy compound, a multifunctional oxetane compound or an episulfide resin. The thermal curing agent can realize or promote the thermal crosslinking reaction of other components in the photosensitive resin composition, improve the heat resistance of the cured product and its binding ability and adhesion to the substrate. Among them, the epoxy compound can be selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, alicyclic epoxy resin, brominated epoxy resin, hydroquinone type epoxy resin, biphenyl type crystalline epoxy resin, naphthalene type epoxy resin, sulfide type epoxy resin, o-cresol novolac type epoxy resin, biphenol novolac type epoxy resin, trishydroxyphenylmethane type epoxy resin, dimethylbenzene type epoxy resin, At least one of phenol-type or biphenol-type epoxy resins or mixtures thereof, bisphenol A novolac-type epoxy resins, tetramethylolethane-type epoxy resins, heterocyclic epoxy resins, diglycidyl phthalate resins, tetraglycidyl ditoluoylethane resins, dicyclopentadiene skeleton glycidyl methacrylate copolymer epoxy resins, cyclohexylmaleimide and glycidyl methacrylate copolymer epoxy resins, epoxy-modified polybutadiene rubber derivatives or CTBN-modified epoxy resins. The polyfunctional oxetane compound may be selected from bis[(3-methyl-3-oxetanylmethoxy)methyl]ether, bis[(3-ethyl-3-oxetanylmethoxy)methyl]ether and 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, (3-methyl-3-oxetanyl)methyl acrylate, (3-ethyl-3-oxetanyl)methyl acrylate, etc. At least one of multifunctional oxetane such as (oxetane) methacrylate, (3-methyl-3-oxetane) methyl methacrylate, (3-ethyl-3-oxetane) methyl methacrylate and oligomers or copolymers thereof, oxetane alcohol and novolac resin, poly(p-hydroxystyrene), Cardo-type bisphenol, calixarene, calixisophthalene and etherification products with resins having hydroxyl groups (such as silsesquioxane). Amino resin is a general term for resins formed by condensation of amino-containing compounds such as urea, melamine or phenyl melamine with formaldehyde or alcohols. The amino resin can be selected from at least one of hydroxymethyl melamine compounds, hydroxymethyl benzoguanamine compounds, hydroxymethyl glycoluril compounds or hydroxymethyl urea compounds. Preferably, the thermal curing agent includes at least one of epoxy compounds, multifunctional oxetane compounds or amino resins.

[0038] As an optional embodiment, the thermal curing agent includes epoxy compounds and amino resins. The epoxy group of the epoxy compound can react with the carboxyl group during the thermal curing process to reduce the acid value of the solder mask layer and improve the acid and alkali resistance and nickel-gold performance of the solder mask layer; the amino resin can react with both the carboxyl group and the hydroxyl group during the thermal curing process, and can simultaneously reduce the acid and hydroxyl value of the solder mask layer, improve the acid and alkali resistance, nickel-gold performance, heat resistance, water resistance and solvent resistance of the solder mask layer, and the amino resin is generally an alkylated melamine formaldehyde resin or a benzoguanamine formaldehyde resin, containing a triazine ring structure, which further improves the heat resistance and adhesion to the copper surface. When the epoxy compound and the amino resin are used together as a curing agent, the carboxyl group is more likely to react with the epoxy group, and the hydroxyl group is more likely to react with the amino group, which can better react the carboxyl and hydroxyl groups in the system, giving the subsequently prepared photosensitive dry film excellent acid and alkali resistance, nickel-gold performance, heat resistance, water resistance and other properties. The weight ratio of the epoxy compound to the amino resin is (2-4): (1-4).

[0039] The catalyst that can promote the reaction of hydroxyl and isocyanate groups can promote the curing reaction between the isocyanate groups after the functional monomer is unblocked and the hydroxyl and carboxyl groups generated after the epoxy acrylic resin is opened, so as to consume the hydroxyl and carboxyl groups generated by the epoxy acrylic resin opening as soon as possible. The catalyst can be a carbamate catalyst, and the amount of the carbamate catalyst added is 0.1wt% to 1wt% of the functional monomer. Further, the amount of the carbamate catalyst added is 0.3wt% to 0.6wt% of the functional monomer. Specifically, the carbamate catalyst can be at least one selected from a tin catalyst, a metal chloride, a metal salt of acetylacetone, a metal sulfate, an amine compound or an amine salt.

[0040] As an optional embodiment, the photosensitive resin composition also includes at least one of an inorganic filler, a pigment, an antioxidant, a dispersant, a defoamer, a thixotropic agent, a thickener, a flame retardant or an adhesion promoter. In the photosensitive resin composition of the present application, in addition to the above-mentioned main raw materials, an appropriate amount of additives or auxiliary agents can be added according to actual needs. The inorganic filler can play a role in adjusting the viscosity of the photosensitive resin composition, inhibiting the curing shrinkage phenomenon during heating and drying, and improving the adhesion of the composition to the substrate. Specifically, the inorganic filler can be selected from at least one of barium sulfate, barium titanate, talc, clay, aluminum oxide, aluminum hydroxide, silicon nitride or aluminum nitride. Preferably, the inorganic filler can be selected from at least one of barium sulfate or silicon dioxide. The amount of the inorganic filler can be selected according to the actual situation, and preferably the weight ratio of the inorganic filler to the epoxy acrylic resin is more suitable in the range of (0-0.45): 1. The pigment can give the photosensitive resin composition a corresponding color, give the photosensitive resin composition and the prepared solder mask a certain degree of recognition or adapt to the surrounding environment. Specifically, the pigment can be selected from at least one of phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, titanium oxide, carbon black or naphthalene black. Antioxidants can prevent the adverse reaction between oxygen in the environment and the photosensitive resin composition, can help capture and neutralize free radicals, delay aging, and increase service life. Specifically, the antioxidant can be selected from hydroquinone, 4-tert-butylcatechol, 2-tert-butylhydroquinone, hydroquinone monomethyl ether, 2,6-di-tert-butyl-p-cresol, 2,2-methylene-bis(4-methyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris(3',5'-di-tert-butyl-4-hydroxybenzyl) -S-triazine-2,4,6-(1H,3H,5H)trione and other phenolic compounds, p-methoxyphenol, quinone and other quinone compounds, bis(2,2,6,6-tetramethyl-4-piperidinyl)-sebacate or phenothiazine and other amine compounds, antioxidants can also be selected from phosphorus compounds such as triphenyl phosphite with peroxide decomposition agent, pentaerythritol tetralauryl thiopropionate, dilauryl thiodipropionate or distearyl 3,3'-thiodipropionate and other sulfur compounds. The amount of antioxidant can be selected according to actual conditions, preferably the weight ratio of antioxidant to epoxy acrylic resin is more suitable in the range of (0.0001-0.01):1.

[0041] As an optional embodiment, the photosensitive resin composition includes, by weight, 100 parts of epoxy acrylic resin, 0.1 to 5 parts of photoinitiator, 30 to 60 parts of thermal curing agent, 1 to 5 parts of functional monomer and 0 to 20 parts of active diluent.

[0042] Another aspect of the embodiment of the present application further provides a photosensitive dry film made from the aforementioned photosensitive resin composition.

[0043] Another aspect of the embodiment of the present application further provides a circuit board, which contains a film layer after the above-mentioned photosensitive dry film is processed.

[0044] The technical solution in the present application is further illustrated below in conjunction with embodiments, but the protection scope of the present application is not limited to the embodiments.

[0045] The photosensitive resin composition was prepared using the components listed in Tables 1 to 3 below.

[0046] Table 1 Formulation of the photosensitive resin composition in Examples 1 to 8

[0047]

[0048] Table 2 Formulation of the photosensitive resin composition in Examples 9 to 15

[0049]

[0050]

[0051] Table 3 Composition of the photosensitive resin composition in Comparative Examples 1 to 8

[0052]

[0053] Among them: alkali-soluble resin a is an acid-modified o-cresol epoxy acrylic resin synthesized internally, with an acid value of 45 mgKOH / g and a weight-average molecular weight (Mw) of 10,000; alkali-soluble resin b is an acid-modified o-cresol epoxy acrylic resin synthesized internally, with an acid value of 80 mgKOH / g and a weight-average molecular weight (Mw) of 30,000; alkali-soluble resin c is an acid-modified o-cresol epoxy acrylic resin synthesized internally, with an acid value of 65 mgKOH / g and a weight-average molecular weight (Mw) of 20,000.

[0054] Schematic diagram of the structure of the internal synthetic resin (o-cresol epoxy acrylic resin):

[0055]

[0056] The photosensitive resin compositions in the above embodiments and comparative examples are prepared by mixing the components and contents of the corresponding formulas, high-speed sand milling, high-speed stirring dissolution and filtering, and are stored in a light-proof environment for later use.

[0057] Performance Testing

[0058] 1. Preparation of solder mask

[0059] The photosensitive resin composition in the above-mentioned embodiment and comparative example is coated and dried to obtain a photosensitive dry film, and then the photosensitive dry film is laminated, exposed, developed and thermally cured to obtain a solder resist layer.

[0060]

Coating

[0061] The photosensitive resin composition was formed into a film on a polyethylene terephthalate (PET) substrate layer, and a coater was used for coating, and the coating thickness was 30 μm.

[0062]

drying

[0063] The substrate layer coated with the photosensitive resin composition is placed in an electric hot air drying oven to remove the solvent by drying to form a photosensitive dry film. The drying temperature of the oven is 85° C. and the drying time is 30 minutes.

[0064]

Film

[0065] Lay the photosensitive dry film onto the surface of the PCB board, and then compact it with a vacuum laminator to ensure that the bubbles between the circuits are completely exhausted.

[0066]

exposure

[0067] Selectively expose the photosensitive dry film, select the appropriate film according to the target pattern, use a high-pressure mercury lamp for exposure, and the exposure energy is 400mJ / cm 2 .

[0068]

development

[0069] The exposed photosensitive dry film is developed, with a 1 wt % sodium carbonate aqueous solution as the developer, a development temperature of 28-32° C., and a development pressure of 0.2-0.4 MPa.

[0070]

Thermal curing

[0071] The developed solder resist dry film is heat cured to form a patterned solder resist layer, the heat curing temperature is 150° C., and the heat curing time is 1 hour.

[0072] 2. Solder mask test

[0073] The solder resist layer prepared by the above method was tested as follows.

[0074]

Solder paste resistance

[0075] The PCB board with solder mask layer was tested for its tolerance to solder paste using a reflow oven. The maximum reflow temperature was set to 265°C, and the solder paste model was Alpha OM363. First, a square area with a length*width*height of 25mm*25mm*0.2mm was circled on the surface of the solder mask layer using a high temperature resistant tape, and then the solder paste was brushed in the square grid to make its thickness flush with the height of the square grid, and then placed in the reflow oven. After the board cooled down, the adhesion of the solder mask layer was evaluated using 3M tape.

[0076] The adhesion evaluation method is as follows: 1mm checkerboard holes (10×10) are formed on a PCB board containing a solder mask layer, and a transparent 3M600 tape is completely attached to the checkerboard holes. After one end of the tape is kept at a right angle to the substrate, the number of checkerboard holes that are not completely peeled off and remain is confirmed by instant peeling. The number of remaining checkerboard holes is used as the numerator, and the total number of checkerboard holes (100) is used as the denominator, and the results are recorded. If the number of checkerboard holes remaining in the adhesion peeling test after one reflow soldering is 100, a second reflow soldering test is performed until the number of checkerboard grids is less than 100, then the test is stopped, and the total number of reflow soldering times and the number of remaining checkerboard holes are recorded; if the number of checkerboard holes remaining in the adhesion peeling test after one reflow soldering is less than 100, the test is stopped, and the number of reflow soldering times and the number of remaining checkerboard holes are recorded. On the premise that the total number of checkerboard eyes after the peel test is 100, the more reflow times it can withstand, the better the solder paste resistance performance; on the premise that the number of reflow times is the same, the more checkerboard eyes remaining after the peel test, the better the solder paste resistance performance.

[0077]

Flux resistance

[0078] The resistance of the PCB board containing the above solder mask layer to flux is tested using a lead-free tin furnace.

[0079] The lead-free soldering furnace temperature is set to 288°C, and the flux model is HAR-809KA.

[0080] The PCB board containing the solder mask layer is immersed in the flux for 30 seconds and then instantly immersed vertically in a 288°C lead-free tin furnace. It is immersed in the tin furnace for 10 seconds and then taken out. After the board cools down, the adhesion of the solder mask layer is evaluated with 3M tape. The evaluation method refers to the evaluation method in the performance of solder paste resistance. In the peeling test, when the number of chessboard eyes is less than 100, stop the test and record the remaining number of chessboard eyes and the number of times immersed in the tin furnace. Under the premise of ensuring that the number of chessboard eyes is 100, the more times it is immersed in the tin furnace, the better the flux resistance performance; under the premise of the same number of immersion in the tin furnace, the more chessboard eyes remain after the glass test, the better the flux resistance performance.

[0081]

Disruption

[0082] Manually fold the heat-cured solder mask layer to evaluate the maximum folding angle it can withstand, where 0°~45° represents a poor bending performance level, 45°~90° represents a medium bending performance level, 90°~135° represents a good bending performance level, and 135°~180° represents an excellent bending performance level. When the maximum folding angle is the critical point value, the level is downgraded.

[0083] Performance Test Results

[0084] The performance test results of the above embodiments and comparative examples are shown in Tables 4 and 5 below.

[0085] Table 4 Performance test results of Examples 1 to 12

[0086]

[0087] Table 5 Performance test results of Examples 13 to 15 and Comparative Examples 1 to 8

[0088]

[0089] It can be seen from Tables 4 and 5 above that the addition of a vinyl-containing blocked isocyanate curing agent can not only improve the Flux resistance (flux resistance and flux resistance) of the photosensitive dry film, but also ensure the flexural properties of the photosensitive dry film.

[0090] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A photosensitive resin composition, characterized in that: The photosensitive resin composition comprises epoxy acrylic resin, photoinitiator, thermal curing agent and functional monomer; the functional monomer is a blocked isocyanate curing agent containing vinyl; In the photosensitive resin composition, the molar number of -NCO groups in the functional monomer is a, the molar number of hydroxyl groups in the epoxy acrylic resin is b, the molar number of carboxyl groups in the epoxy acrylic resin is c, the molar number of epoxy groups in the thermal curing agent is d, and the molar number of amino groups in the thermal curing agent is e, satisfying b+c+d≤a+e.

2. The photosensitive resin composition according to claim 1, characterized in that: The functional monomer is prepared from vinyl-containing isocyanate and a blocking agent; the blocking agent includes at least one of a phenol blocking agent, a lactam blocking agent, an active methylene blocking agent, an alcohol blocking agent, an oxime blocking agent, a thiol blocking agent, an amide blocking agent, an imide blocking agent, an amine blocking agent or a pyrazole blocking agent; Preferably, the deblocking temperature of the functional monomer is greater than or equal to 95°C and less than or equal to 150°C.

3. The photosensitive resin composition according to claim 2, characterized in that: The vinyl-containing isocyanate is (CH2=CH) s -Y-(NCO) q or (CH2=C(CH3)) s -Y-(NCO) q At least one of, wherein q is greater than or equal to 1, n is greater than or equal to 1, and the Y group includes at least one of a substituted or unsubstituted carbon chain group, an aliphatic ring group, an aromatic ring group or an oxygen-containing group.

4. The photosensitive resin composition according to claim 1, characterized in that: The epoxy acrylic resin is an alkali-soluble epoxy acrylic resin; Preferably, the acid value of the alkali-soluble epoxy acrylic resin is 45 to 80 mgKOH / g, and the weight average molecular weight of the epoxy acrylic resin is 10,000 to 30,000.

5. The photosensitive resin composition according to claim 1, characterized in that: The photosensitive resin composition further includes a urethanization catalyst, and the addition amount of the urethanization catalyst is 0.1wt% to 1wt% of the functional monomer; Preferably, the carbamate catalyst comprises at least one of a tin catalyst, a metal chloride, a metal acetylacetonate, a metal sulfate, an amine compound or an amine salt; and the amount of the carbamate catalyst added is 0.3 wt % to 0.6 wt % of the functional monomer.

6. The photosensitive resin composition according to claim 1, characterized in that: The photosensitive resin composition further comprises a reactive diluent, wherein the reactive diluent is at least one of the reactive diluents containing at least one vinyl group; Preferably, the reactive diluent does not contain ethoxy groups or propoxy groups.

7. The photosensitive resin composition according to claim 1, characterized in that: The photoinitiator includes at least one of a cleavage-type free radical initiator and a hydrogen abstraction-type free radical initiator; preferably, the cleavage-type free radical initiator includes at least one of an α-hydroxyketone derivative initiator, an α-aminoketone derivative initiator, an acylphosphine oxide photoinitiator or an oxime ester initiator, and the hydrogen abstraction-type free radical initiator includes at least one of a benzophenone and its derivative initiator, a thioxanthone and its derivative initiator, an anthraquinone and its derivative initiator or a titanocene initiator; More preferably, the photoinitiator includes at least one of an acylphosphine oxide-based initiator or an oxime ester-based photopolymerization initiator.

8. The photosensitive resin composition according to claim 1, characterized in that: The thermal curing agent includes at least one of an isocyanate compound, a blocked isocyanate compound, an amino resin, a benzoxazine resin, a carbodiimide resin, a cyclocarbonate compound, an epoxy compound, a multifunctional oxetane compound or an episulfide resin; Preferably, the thermal curing agent comprises at least one of an epoxy compound, a multifunctional oxetane compound or an amino resin; Preferably, the weight ratio of the epoxy compound to the amino resin is (2-4):(1-4).

9. The photosensitive resin composition according to claim 1, characterized in that: In parts by weight, the photosensitive resin composition comprises 100 parts by weight of the epoxy acrylic resin, 0.1 to 5 parts by weight of the photoinitiator, 30 to 60 parts by weight of the thermal curing agent, 1 to 5 parts by weight of the functional monomer and 0 to 20 parts by weight of the reactive diluent.

10. A photosensitive dry film, characterized in that: The photosensitive dry film is prepared from the photosensitive resin composition according to any one of claims 1 to 9.

11. A circuit board, characterized in that: The circuit board comprises a film layer obtained by processing the photosensitive dry film according to claim 10.

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