A dry film resist laminate, a resin composition, and a method for preparing the same

Abstract

The present invention discloses a dry film resist laminate and a preparation method thereof. The laminate includes a support layer, a resist layer above the support layer, and a protective layer above the resist layer. The resist layer has a first surface facing the protective layer and a second surface opposite to the first surface. The resist layer is a pre-crosslinked resist layer, and the degree of pre-crosslinking of the first surface is less than that of the second surface. The dry film resist laminate of the present invention has both good followability and storage stability. During the lamination process, it can fully fill the pits on the substrate, and at the same time can prevent glue overflow to a certain extent and improve storage stability. The dry film resist laminate can be applied to fields such as printed circuit boards, lead frames, solar cells, conductor encapsulation, BGA (Ball Grid Array) encapsulation, CSP (Chip Size Package) encapsulation, etc., and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of photoresists, and particularly relates to a dry film resist laminate and a preparation method thereof. Background Art

[0002] In the fields of printed circuit boards, lead frames, solar cells, conductor packages, BGA (Ball Grid Array) packages, CSP (Chip Size Package) packages, etc., dry film resists are widely used as key materials for pattern transfer. For example, when manufacturing a printed circuit board, first, a dry film resist is laminated on a substrate, covered with a mask having a certain pattern, and subjected to pattern exposure, or directly exposed by laser direct writing; then, the unexposed part is removed by a developer, and then etching or electroplating treatment is performed to form a pattern; finally, the cured part of the dry film is removed, thereby realizing pattern transfer. However, the substrates used in the actual production process are not uniformly flat and smooth on the surface. The multi-layered circuit boards are often affected by the inner layer circuits and vias, resulting in unevenness; if there is a gap between the substrate and the resist, it will cause gaps in the resist pattern, and the etching solution will invade this gap during the etching process, eventually leading to circuit notches or even open circuits. Therefore, we hope that the photosensitive dry film resist has good fluidity and followability, and can smoothly and fully fill the pits on the substrate during the lamination process; however, excellent fluidity and followability will affect the storage stability to a certain extent; when the dry film is transported and stored in the form of a roll, the resist layer in the middle will flow under the action of pressure, that is, the resist layer will have uneven thickness due to local flow and overflow to both ends of the dry film roll, that is, bleeding (overflowing) occurs, thus affecting the normal use of the dry film and shortening its shelf life. At present, the shelf life of the pre-cut dry film rolls on the market can generally only be maintained for about 1 to 3 months.

[0003] In order to improve the storage stability of the photosensitive dry film, people have made a lot of efforts. Patent US3867153A performs photocuring treatment on very narrow edge regions at both ends of the photosensitive dry film to prevent the resist from flowing out from both ends and improve the storage stability; however, it still cannot solve the problem of uneven thickness caused by local flow in the un-pre-crosslinked middle region. Patent CN108227379A mainly improves the bleeding problem by adding cellulose to increase the viscosity of the photopolymerization component, but the addition of cellulose will affect properties such as resolution, photosensitivity, and developability. Patent CN101196686B provides a dry film resist with good resolution after development, reduced formation of aggregates, and good bleeding and followability by adjusting the synthesis components of the alkali-soluble resin; however, it is more difficult to start from the synthesis.

[0004] In summary, how to make the dry film resist laminate have both good followability and excellent storage stability, which are two contradictory properties, is a difficult problem that urgently needs to be solved. Summary of the Invention

[0005] The object of the present invention is to solve the above problems and provide a dry film resist laminate with both followability and storage stability.

[0006] To achieve the above object, the technical method adopted by the present invention is as follows:

[0007] A dry film resist laminate, the laminate includes a resist layer, a support layer on one side of the resist layer, and a protective layer on the other side of the resist layer. The resist layer has a first surface facing the protective layer and a second surface opposite to the first surface; the resist layer is a pre-crosslinked resist layer, and the pre-crosslinking degree of the first surface is less than that of the second surface.

[0008] In the existing dry film resist during the exposure process, using external energies such as ultraviolet light and laser, the photosensitive substances contained undergo photochemical reactions to form crosslinked structures to achieve the effect of selective local complete curing, and at this time the crosslinking degree is relatively high; before the exposure process or before the dry film resist product is used, the photosensitive substances in the resist layer do not undergo photochemical reactions and the crosslinking degree is 0, that is, in an uncured state. We call the resist layer that is actively irradiated and undergoes a certain degree of crosslinking reaction and presents a semi-cured state before the exposure process or during the preparation of the dry film resist laminate a pre-crosslinked resist layer, and the method of irradiating the resist layer to make it present a semi-cured state is called the crosslinking treatment method.

[0009] Further, the pre-crosslinking degree of the resist layer increases in the extending direction from the first surface to the second surface.

[0010] Further, the pre-crosslinking degree of the resist layer is not more than 20%.

[0011] Further, the part with a pre-crosslinking degree of 0 - 5% of the resist layer is the low pre-crosslinking degree part, and the part with a pre-crosslinking degree of 5% - 20% is the high pre-crosslinking degree part; the thickness of the low pre-crosslinking degree part is 50% - 90% of the thickness of the resist layer, and the thickness of the high pre-crosslinking degree part is 10% - 50% of the thickness of the resist layer.

[0012] Further, the thickness of the low pre-crosslinking degree part is 70% - 90% of the thickness of the pre-crosslinked resist layer, and the thickness of the high pre-crosslinking degree part is 10% - 30% of the thickness of the pre-crosslinked resist layer.

[0013] Further, the resist layer is a single-layer structure or a multi-layer structure.

[0014] Furthermore, the thickness of the resist layer is 15 - 60 μm.

[0015] Another object of the present invention is to provide a resin composition for preparing the resist layer of the dry film resist laminate, and the resin composition comprises the following components: 30 - 70 parts by mass of an alkali-soluble resin, 30 - 50 parts by mass of an ethylenically photopolymerizable unsaturated monomer, 0.1 - 5 parts by mass of an initiator, and 0.1 - 5 parts by mass of an additive.

[0016] Another object of the present invention is to provide a method for preparing the dry film resist laminate, comprising the steps of:

[0017] (1) Dissolving all components of the resist layer in an organic solvent and dispersing them uniformly to form a mixture with a solid content of 35% - 50%;

[0018] (2) Providing a support layer, coating the mixture on one side of the support layer and then performing a drying treatment to obtain a resist preparation layer;

[0019] (3) Performing a crosslinking treatment on the resist preparation layer from one side of the support layer or / and from the side away from the support layer to obtain a resist layer;

[0020] (4) Attaching a protective layer to the side of the resist layer away from the support layer to obtain the dry film resist laminate;

[0021] Or,

[0022] (1) Dissolving all components of the resist layer in an organic solvent and dispersing them uniformly to form a mixture with a solid content of 35% - 50%;

[0023] (2) Providing a support layer, coating the mixture on one side of the support layer and then performing a drying treatment to obtain a resist preparation layer;

[0024] (3) Attaching a protective layer to the side of the resist preparation layer away from the support layer to obtain a laminate preparation;

[0025] (4) Performing a crosslinking treatment on the laminate preparation from one side of the support layer or / and from the side away from the support layer to obtain the dry film resist laminate.

[0026] Furthermore, the crosslinking treatment methods include laser crosslinking and ultraviolet crosslinking.

[0027] Furthermore, the energy of the crosslinking treatment is 0.1 - 18 mJ.

[0028] The beneficial effects produced by the technical solution of the present invention include:

[0029] The present invention provides a dry film resist laminate, a resin composition for preparing a resist layer, and a method for preparing the laminate. The resist layer is a single-layer structure or a multi-layer structure. By performing a crosslinking treatment to make the resist layer a pre-crosslinked resist layer and controlling the pre-crosslinking degree of the first surface of the resist layer to be less than that of the second surface, the fluidity of the entire resist layer can be reduced, bleeding of the glue can be prevented, and at the same time, good following performance and adhesion performance of the first surface can be ensured, achieving the matching of followability and storage stability, thereby further improving the production yield and efficiency of PCBs. Specific embodiments

[0030] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be further described in detail below with reference to specific embodiments.

[0031] Unless otherwise defined, the technical terms or scientific terms used in the disclosure of the present invention should have the ordinary meaning that can be understood by those skilled in the art in the field to which the present invention pertains.

[0032] As analyzed in the background art, in the prior art, the resist layer of the dry film resist laminate has a certain fluidity, and during storage or transportation, under the action of pressure, adverse phenomena such as bleeding of the glue will occur, seriously affecting its storage stability; in addition, during the use of the dry film resist laminate, the resist layer is also required to have a certain followability and filling property, and the prior art cannot simultaneously take into account these two mutually contradictory properties of storage stability and followability. To solve this problem, the present invention provides a dry film resist laminate, a resin composition for preparing a resist layer, and a method for preparing the laminate.

[0033] In a typical embodiment of the present application, a dry film resist laminate is provided. The dry film resist laminate includes a resist layer, a support layer on one side of the resist layer, and a protective layer on the other side of the resist layer. The resist layer has a first surface facing the protective layer and a second surface opposite to the first surface; the resist layer is a pre-crosslinked resist layer, and the pre-crosslinking degree of the first surface is less than that of the second surface.

[0034] In the existing dry film resist during the exposure process, by using external energies such as ultraviolet light and laser, the photosensitive substances contained therein undergo a photochemical reaction to generate a crosslinked structure, so as to achieve the effect of selective local complete curing, and at this time the crosslinking degree is relatively high; while before the exposure process or before the dry film resist product is used, the photosensitive substances in the resist layer do not undergo a photochemical reaction and the crosslinking degree is 0, that is, it is in an uncured state. We call the resist layer that is actively subjected to light treatment on the resist layer and undergoes a certain degree of crosslinking reaction and presents a semi-cured state before the exposure process or during the preparation of the dry film resist laminate a pre-crosslinked resist layer, and the above-mentioned method of subjecting the resist layer to light treatment to make it present a semi-cured state is called a crosslinking treatment method.

[0035] During the use of the dry film resist laminate, first, the protective layer is peeled off, the exposed first surface is adhered to the circuit board substrate, and the resist is exposed from the side of the second surface. Performing pre-crosslinking treatment on the resist layer can, to a certain extent, reduce its fluidity and avoid problems such as uneven thickness and bleeding of the dry film resist laminate caused by local flow of the resist layer under pressure during transportation or storage, and improve storage stability; however, the decrease in fluidity will inevitably lead to a decrease in followability and filling ability, and the resist layer cannot fully fill the pits on the substrate. Performing pre-crosslinking treatment on the resist layer and simultaneously limiting the pre-crosslinking degree of the first surface facing the protective layer to be less than that of the second surface can not only improve the storage stability of the dry film resist layer, but also prevent poor followability and filling ability caused by excessive pre-crosslinking degree of the first surface, and achieve a balance between storage and followability.

[0036] Furthermore, the pre-crosslinking degree increases in the extending direction of the resist layer from the first surface to the second surface.

[0037] In order to ensure the followability of the resist layer and not affect the requirements for resolution and resolution in subsequent patterning use, it is preferably that the pre-crosslinking degree of the resist layer is not greater than 20%.

[0038] Furthermore, the part with a pre-crosslinking degree of 0 - 5% of the resist layer is a low pre-crosslinking degree part, and the part with a pre-crosslinking degree of 5% - 20% is a high pre-crosslinking degree part; the thickness of the low pre-crosslinking degree part is 50% - 90% of the thickness of the resist layer, and the thickness of the high pre-crosslinking degree part is 10% - 50% of the thickness of the resist layer.

[0039] In order to further ensure the sufficient followability of the resist layer and the resolution and adhesion performance after exposure and development, it is preferably that the thickness of the above-mentioned low pre-crosslinking degree part is 70% - 90% of the thickness of the pre-crosslinked resist layer, and the thickness of the high pre-crosslinking degree part is 10% - 30% of the thickness of the pre-crosslinked resist layer.

[0040] Further, the resist layer is a single-layer structure or a multi-layer structure. When the resist layer is a single-layer structure, the pre-crosslinking degree increases in the extending direction from the first surface to the second surface; when the resist layer is a multi-layer structure, the pre-crosslinking degrees of different layers are different.

[0041] Further, the thickness of the resist layer is 15 - 60 μm.

[0042] In another typical embodiment of the present application, a resin composition is provided. The resin composition is used to prepare the resist layer of any one of the above dry film resist laminates. The resin composition includes the following components: 30 - 70 parts by mass of an alkali-soluble resin, 30 - 50 parts by mass of an ethylenically photopolymerizable unsaturated monomer, 0.1 - 5 parts by mass of an initiator, and 0.1 - 5 parts by mass of an additive.

[0043] Further, the alkali-soluble resin can be selected from conventional alkali-soluble resins in the prior art. In order to control the cost of the alkali-soluble resin in the present application, it is preferred that the alkali-soluble resin is prepared by copolymerizing one or more first copolymer unit monomers containing carboxyl groups with one or more second copolymer unit monomers without carboxyl groups.

[0044] Further, the first copolymer unit monomer is selected from any one or more of itaconic acid, crotonic acid, acrylic acid, methacrylic acid, maleic acid semi-ester, maleic acid, fumaric acid, vinylacetic acid and its anhydride; the second copolymer unit monomer is selected from any one or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, (meth)acrylonitrile, glycidyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminopropyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N,N-diethylaminobutyl (meth)acrylate, (meth)acrylamide, N-hydroxymethylacrylamide, N-butoxymethylacrylamide, styrene, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, (alkoxylated) nonylphenol (meth)acrylate.

[0045] Furthermore, the acid value of the alkali-soluble resin is in the range of 90-300 mg KOH / g. When the acid value is lower than 90 mg KOH / g, it is difficult to develop, and it is difficult to obtain a pattern with good appearance under conventional development conditions; when the acid value exceeds 300 mg KOH / g, the pattern is easily peeled off during the development process, resulting in development defects. Preferably, the acid value is 115-175 mg KOH / g.

[0046] Furthermore, the weight average molecular weight of the alkali-soluble resin is 50,000 to 200,000. When the weight average molecular weight is greater than 200,000, the resolution of the resist layer after exposure and development deteriorates; when the weight average molecular weight is less than 50,000, the development operation window becomes narrower, and the adhesion of the pattern to the substrate after development is reduced. In order to further control the fluidity of the resist layer and to improve the adhesion of the pattern obtained after development as much as possible, the weight average molecular weight is preferably 70,000 to 120,000.

[0047] Further, the olefinic photopolymerizable unsaturated monomer can also be selected from conventional photopolymerizable monomers in the prior art, preferably any one or more of (meth)acrylates containing bisphenol A structure, polyethylene glycol di(meth)acrylates, polypropylene glycol di(meth)acrylates, polyethylene oxide propylene oxide di(meth)acrylates, (meth)acrylate alkyl esters, trimethylolpropane tri(meth)acrylates, alkoxylated trimethylolpropane triacrylates, pentaerythritol tri(meth)acrylates, alkoxylated pentaerythritol tri(meth)acrylates, pentaerythritol tetra(meth)acrylates, alkoxylated pentaerythritol tetra(meth)acrylates, dipentaerythritol tetra(meth)acrylates, alkoxylated dipentaerythritol tetra(meth)acrylates, nonylphenol (meth)acrylates, alkoxylated nonylphenol (meth)acrylates, phenoxyethyl (meth)acrylates, and alkoxylated phenoxyethyl (meth)acrylates.

[0048] Further, the photoinitiator can also be selected from the photoinitiators commonly used in the prior art, preferably any one or more of benzoin ethers, benzophenones and their derivatives, thioxanthone compounds, anthraquinones and their derivatives, thioxanthone compounds, hexaarylbiimidazole compounds, acridine compounds in any ratio combination; preferably, the photoinitiator is selected from benzoin ethers, benzophenone, thioxanthone, anthraquinone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, 2-ethylanthraquinone, phenanthraquinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, 2,3-dimethylanthraquinone, benzoin methyl ether, benzoin ethyl ether, benzoin phenyl ether, benzil dimethyl ketal, benzoin dimethyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin phenyl ether, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, benzophenone, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), 4,4'-bis(diethylamino)benzophenone, isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-tert-butylanthraquinone, N,N-diethylbenzoate, dimethylaminoethyl benzoate, N,N-dimethylethanolamine, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-diimidazole, 2,2'-bis(2-bromo-5-methoxyphenyl)-4,4',5,5'-tetraphenyldiimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyldiimidazole, 9-phenylacridine, 9-p-phenylacridine, 9-m-tolylacridine, 9-o-tolylacridine, 9-p-chlorophenylacridine, 1,7-bis(9-acridinyl)heptane, etc. Any one or more of them.

[0049] Further, the additive is any one or more of a dye, a developer, a plasticizer, an antifoaming agent, a polymerization inhibitor, and an antioxidant.

[0050] Further, the dye is any one or more of phthalocyanine green, malachite green, bright green, methyl violet, crystal violet, methyl green, Victoria blue B, basic green, rhodamine B, methyl orange.

[0051] Further, the developer is selected from any one or more of amyl bromide, ethylene dibromide, benzyl bromide, dibromomethane, tribromomethyl phenyl sulfone, trichloroacetamide, amyl iodide, hexachloroethane.

[0052] Further, the plasticizer is selected from phthalic acid compounds or sulfonamide compounds; preferably, the plasticizer is selected from any one or more of diethyl phthalate, diphenyl phthalate, p-toluenesulfonamide.

[0053] Furthermore, the inhibitor is selected from any one or more of p-methoxyphenol, hydroquinone, pyrogallol, tert-butylcatechol, and aluminum N-nitroso benzhydroxamate.

[0054] In another typical embodiment of the present application, a method for preparing any one of the above dry film resist laminates is provided, including the steps of:

[0055] (1) Dissolve all components of the resist layer in an organic solvent and disperse evenly to form a mixture with a solid content of 35%-50%;

[0056] (2) Provide a support layer, coat the mixture on one side of the support layer and then perform a drying treatment to obtain a resist preparation layer;

[0057] (3) Crosslink the resist preparation layer from one side of the support layer or / and from the side away from the support layer to obtain a resist layer;

[0058] (4) Attach a protective layer to the side of the resist layer away from the support layer to obtain the dry film resist laminate;

[0059] Or,

[0060] (1) Dissolve all components of the resist layer in an organic solvent and disperse evenly to form a mixture with a solid content of 35%-50%;

[0061] (2) Provide a support layer, coat the mixture on one side of the support layer and then perform a drying treatment to obtain a resist preparation layer;

[0062] (3) Attach a protective layer to the side of the resist preparation layer away from the support layer to obtain a laminate preparation;

[0063] (4) Crosslink the laminate preparation from one side of the support layer or / and from the side away from the support layer to obtain the dry film resist laminate.

[0064] The resist layer has a certain thickness, which will affect the light transmission, light scattering, and energy transfer of light. When the resist layer is a single-layer structure, crosslinking treatment is carried out on one side of the self-supporting layer. The light intensity received from the second surface to the first surface of the resist layer gradually weakens. Or crosslinking treatment is carried out simultaneously from both sides and the energy received by the second surface is controlled to be greater than that of the first surface, so that the pre-crosslinking degree of the first surface is less than that of the second surface. When the resist layer is a multi-layer structure, the steps (2) and (3) of the first preparation method need to be repeated, that is, multiple coating and multiple crosslinking treatments; multiple crosslinking treatments can be carried out on one side of the self-supporting layer or multiple crosslinking treatments can be carried out on the side far from the supporting layer and the energy of each crosslinking treatment is controlled to weaken in turn; if crosslinking treatment is carried out simultaneously from both sides, it is necessary to control the energy received by the resist layer on the side close to the supporting layer to be greater than that of the resist layer far from the supporting layer.

[0065] Further, the crosslinking treatment methods include laser crosslinking and ultraviolet crosslinking. Among them, for ultraviolet crosslinking, an ultraviolet lamp with a wavelength range of 200 - 410nm can be selected, such as a high-pressure mercury lamp, a UV-LED lamp; laser crosslinking can be used to achieve pre-crosslinking through an excimer laser or a semiconductor laser, such as KrF excimer laser, Ar ion laser, YAG laser, etc.

[0066] Further, the energy of the crosslinking treatment is 0.1 - 18mJ.

[0067] Further, the energy of the crosslinking treatment can be selected according to the exposure energy of the resist layer. Under a UV exposure machine, using a 41-step exposure scale at 20ST - 23ST, for a dry film resist laminate with an exposure energy of 30 - 60mJ required for the resist layer, it is a common dry film resist laminate; for a dry film resist laminate with an exposure energy of 3 - 15mJ required for the resist layer, it is a high-sensitivity dry film resist laminate; for a dry film resist laminate with an exposure energy of 15 - 30mJ required for the resist layer, it is a semi-high-sensitivity dry film resist laminate. When the dry film resist laminate is a common dry film resist laminate, the energy of the crosslinking treatment is 1 - 18mJ, and further preferably 2 - 10mJ; when the dry film resist laminate is a high-sensitivity dry film resist laminate, the energy of the crosslinking treatment is 0.1 - 2mJ, and further preferably 0.1 - 1mJ; when the dry film resist laminate is a semi-high-sensitivity dry film resist laminate, the energy of the crosslinking treatment is 0.3 - 7mJ, and further preferably 0.5 - 3mJ.

[0068] If the energy of the cross-linking treatment is too low, the resist layer cannot reach a certain degree of pre-cross-linking, thus failing to reduce the risk of bleeding. If the energy of the cross-linking treatment is too high, the resist layer will be over-cross-linked, posing an exposure risk, with the flexibility of the dry film deteriorating, the followability decreasing, and the resolution and adhesion significantly decreasing after exposure and development.

[0069] Further, the solvent is any one or more of methanol, ethanol, n-butanol, methyl ethyl ketone, acetone, toluene, and xylene.

[0070] Further, in order to achieve a better coating effect, the viscosity of the mixture at 25 °C is 1000 - 8000 mPa·s.

[0071] The beneficial effects of the present application will be further described below in conjunction with examples and comparative examples.

[0072] 1. Synthesis of alkali-soluble copolymer resin A

[0073] Prepared by free radical solution polymerization, including the following steps:

[0074] Mix methacrylic acid (MAA), methyl methacrylate (MMA), butyl acrylate (BA), and styrene (ST) evenly according to a certain mass ratio, add initiator AIBN and methyl ethyl ketone, stir and dissolve, and add about 35% by mass of the mixed solution to a three-necked flask protected by nitrogen and equipped with a condensing reflux device through a peristaltic pump. Heat the oil bath to 80 °C, stir and react for 1 h, then slowly add the remaining mixed solution within 3 h. Continue to keep the temperature for reaction for 4 h, then raise the temperature to 90 °C, add the methyl ethyl ketone solution dissolved with a small amount of initiator in two portions, with an interval of 1 h between the two additions. After the addition is completed, keep stirring at a constant temperature for 3 h to end the reaction, and obtain alkali-soluble copolymer resin A.

[0075] Different alkali-soluble copolymer resins A-1 and A-2 and their corresponding dry resins with different properties (the dry resin is the resin after deducting the solvent) are obtained according to different mass ratios of MAA, MMA, BA, and ST, as shown in Table 1:

[0076] Table 1: Alkali-soluble copolymer resins A-1 and A-2 and their corresponding property table

[0077] 2. Preparation of the resist layer coating solution (mixture)

[0078] According to the mass ratio scheme in Table 2 below, mix each component according to the ratio, add methyl ethyl ketone and ethanol, and stir at high speed with a high-speed disperser to fully mix and dissolve each component to prepare a resist layer coating solution with a solid content of 37%.

[0079] Table 2: Resist layer coating solution ratio table (by mass parts)

[0080] Description:

[0081] B-1 is ethoxylated trimethylolpropane triacrylate (Sartomer monomer SR454, with 3 ethoxy units);

[0082] B-2 is polyethylene oxide - polypropylene oxide dimethacrylate (Changzhou Qiangli New Materials TM2203, with a total of 6 ethoxy repeating units and 12 propoxy repeating units);

[0083] B-3 is ethoxylated bisphenol A diacrylate (Sartomer monomer SR602, with 10 ethoxy units);

[0084] B-4 is ethoxylated phenol acrylate (Changzhou Qiangli New Materials, with 8 ethoxy groups);

[0085] The above C-1 and C-2 components together form component (C), where:

[0086] C-1 is 2,2’,4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4’,5’-diphenyl-1,1’-diimidazole (Changzhou Qiangli Electronics);

[0087] C-2 is 9-phenylacridine (Shanghai TCI Chemical Industry);

[0088] The above D-1, D-2, D-3, and D-4 components together form component (D), where:

[0089] D-1 is malachite green (Shanghai TCI Chemical Industry);

[0090] D-2 is tribromomethylphenyl sulfone (Shanghai TCI Chemical Industry);

[0091] D-3 is p-toluenesulfonamide (Shanghai TCI Chemical Industry);

[0092] D-4 is hydroquinone (J&K Chemical);

[0093] 3. Preparation of dry film resist laminate

[0094] The above-mentioned resist layer coating solution is evenly coated on the support layer PET (15 μm thick) on the production line and dried through a channel at 80 °C to form a resist preparatory layer with a certain thickness, which appears green under a yellow light; then it passes through an ultraviolet light irradiation area or a laser irradiation area. When the resist layer is a single-layer structure, irradiation is carried out from the side of the support layer, and then a PE film (20 μm) as a protective layer is laminated on the side far from the support layer, thereby forming a dry film resist laminate in which the pre-crosslinking degree of the first side of the resist layer is less than that of the second side; or the protective layer is laminated first and then crosslinked. When the resist layer is a multi-layer structure, multiple coating, drying, and crosslinking treatments are carried out, and finally the protective layer is laminated; each time a layer is coated and dried, a crosslinking treatment is carried out from the side far from the support layer, and the energy of each crosslinking treatment is controlled to decrease in turn, and the pre-crosslinking degree between layers of the finally formed resist layer increases in turn in the extending direction from the first side to the second side.

[0095] It is wound up with a 6-inch reel, the winding length is 3000 m, and the winding width is 1260 mm. Finally, the master roll is slit into dry film rolls with a length of 200 m and a width of 248 mm.

[0096] Hereinafter, the sample production methods (including film lamination, exposure, and development), sample evaluation methods, and evaluation results of the examples and comparative examples will be described.

[0097]

Film Lamination

[0098] The copper surface of the copper clad laminate is polished by a grinding machine, washed with water, and dried to obtain a bright and fresh copper surface. The temperature of the pressure roller of the film laminator is set at 110 °C, the conveying speed is 1.5 m / min, and hot lamination is carried out under standard pressure.

[0099]

Exposure

[0100] Exposure is carried out using a M-522 type exposure machine of Zhisheng Technology, and a stouffer 41-step exposure ruler is used for photosensitivity testing.

[0101]

Development

[0102] The line width / line pitch of the selected film for development gradually increases from 10 μm to 100 μm; the developer is a 1%wt sodium carbonate aqueous solution, the development temperature is 30 °C, the development pressure is 1.8 bar, the development speed is 1.5 m / min, and the model of the developing machine is Yuansu Technology XY-430. The minimum time required to completely dissolve the unexposed part of the resist layer is taken as the minimum development time.

[0103]

Crosslinking Degree Evaluation

[0104] The crosslinking degree of the resist layer is monitored by on-line infrared. The infrared spectrum of the resist layer is tested before illumination. Subsequently, the dry film is placed under an ultraviolet lamp for illumination with a certain energy and duration. At appropriate time intervals, an infrared spectrometer is used to track and test the curing degree of the surface layer of the resist layer. The crosslinking degree is calculated according to the following formula:

[0105]

[0106] Where: A C=C,0 , A C=C,t is the out-of-plane bending vibration absorption peak area of the =CH bond at 810 cm -1 after irradiation for 0, t seconds. A C=O,0 , A C=O,t is the vibration absorption peak area of the C=O bond at 1730 cm -1 after irradiation for 0, t seconds.

[0107]

Resolution evaluation

[0108] The resist layer is laminated on a copper plate using a heated pressure roller. Here, exposure is carried out using a mask with a wiring pattern having a width ratio of exposed part to unexposed part of 1:1 (10 - 100 μm). After development for 1.5 times the development removal time, the resist pattern is observed using a magnifying glass. The resolution is evaluated by the minimum line width that can completely remove the unexposed part and where the lines do not show distortion or defect and remain. The smaller this value, the better the resolution.

[0109]

Adhesion evaluation

[0110] Exposure and development are carried out using a photomask with equal line spacing and different line widths of Line / Space = n / 400 μm (n ranges from 15 to 51, increasing by 3 each time). After washing with water and drying, the resist pattern is observed using a magnifying glass. The adhesion is evaluated by the minimum line width that can completely remove the unexposed part and where the lines do not show distortion or defect and remain. The smaller this value, the better the adhesion.

[0111]

Resist overflow rate evaluation

[0112] Cut several square PET films with a size of about 10 cm × 10 cm for standby. Cut the dry film resist laminate to be measured into squares with a size of 2.54 cm × 2.54 cm (1 inch × 1 inch). Tear off the PE film (protective layer) of the cut dry film resist laminate, and tightly attach the exposed resist surface to the central part inside the cut PET film (the four sides of the resist layer should be parallel to the four sides of the PET). Cover another PET film on the support film of the dry film resist laminate. Use a flat vulcanizer, set the lamination temperature to 40 °C and the pressure to 10 MPa. After the temperature stabilizes for 1 h, place the sample in the middle position of the laminating plate for lamination, and the lamination time is 5 min. Observe the overflow width of the sample on each side under a 2D optical image measuring instrument, and measure the overflow width of each side and the actual width of the sample. Divide the overflow width of each side by the actual width of the dry film resist laminate on that side before lamination, and take the value as the glue overflow rate of that side. Calculate the average value of each side, and take the average value of 3 samples as the glue overflow rate of this sample (the reading should observe the sample within 1 hour after being pressed out by the press). The smaller the glue overflow rate value, the less likely it is to overflow glue.

[0113]

Evaluation of storage stability

[0114] Place the cut dry film rolls in a constant temperature and humidity aging oven at room temperature (5 - 25 °C) and 50 °C respectively, and control the relative humidity of both to be between 40% - 70%. Observe the glue overflow situation on the side of the dry film roll after a period of time.

[0115] When stored at room temperature:

[0116] 1: No glue flow after 6 months of storage;

[0117] 2: Slight glue flow appears after 6 months of storage;

[0118] 3: Slight glue flow appears after 3 months of storage;

[0119] 4: Severe glue flow appears after 3 months of storage;

[0120] When stored at 50 °C:

[0121] 1: No glue flow after 1 month of storage;

[0122] 2: Slight glue flow appears after 1 month of storage;

[0123] 3: Slight glue flow appears after 2 weeks of storage;

[0124] 4: Severe glue flow appears after 2 weeks of storage;

[0125]

Evaluation of filling property

[0126] Preparation of Filled Substrate: Cut a suitable dry film resist laminate sample according to the size of the copper clad laminate. Laminate the cut dry film resist laminate, and let it stand still under backlight for 15 minutes. Then select a film negative of the desired pit shape for exposure (exposure grid: 20 - 23 ST / 41-step exposure ruler) and development. Pretreatment: Micro-etching is carried out to thin the copper to obtain pits. The copper thickness is thinned by 0.5 - 1.5 μm in one pass, and the pit depth is controlled by controlling the number of micro-etching times. The common depth range is 6 - 15 μm. Stripping: The stripping solution is 3% sodium hydroxide. Immerse it in the stripping solution for stripping, then wash with water and dry. Thickness measurement: Use a surface roughness meter to measure the copper plating thickness, that is, the pit depth.

[0127] Preparation of Filled Sample: Cut a dry film resist laminate sample according to the size of the copper clad laminate, laminate the film, expose it, develop it, and finally observe the dry film filling situation with a scanning electron microscope (SEM). Select a straight pit with a line width and pitch of 3 mil. If the dry film can completely fill an 8-μm deep pit (without voids at the corners) but cannot fill a 10-μm deep pit, it means the filling ability of the dry film is 8 μm.

[0128]

Evaluation Results

[0129] The evaluation results of the examples and comparative examples are shown in Table 3. All the resolution, adhesion, and filling properties are measured under the condition of 23 exposure grids.

[0130] Table 3: Evaluation Results Table of Examples and Comparative Examples

[0131] As shown in Table 3, by comparing Examples 1 - 12 with Comparative Examples 1 - 3, it can be seen that for the dry film resist laminate with cross-linking treatment and the pre-crosslinking degree of the first side being less than that of the second side, the bleeding rate decreases and the storage stability improves, while the resolution, adhesion, and filling properties can still meet the usage requirements. This shows that the resist layer is a pre-crosslinked resist layer, and for the dry film resist laminate with the pre-crosslinking degree of the first side being less than that of the second side, the bleeding phenomenon is significantly reduced, and it has excellent storage stability while taking into account the filling property and followability. Specifically, by comparing Example 4 with Examples 8 and 9, it can be seen that if the cross-linking treatment energy is too high and the pre-crosslinking degree is too large, it will affect the usage performance of the resist layer, such as resolution, adhesion, and filling properties, etc.; in Example 7, the thickness of the second layer is greater than that of the first layer, that is, the proportion of the high pre-crosslinking degree part is too large, and its usage performance is slightly worse than that of Example 1; from Examples 1, 5, and 6, it can be seen that the thickness of the resist layer will also affect the storage stability and usage performance. Being too thin is not conducive to filling, and being too thick will increase the bleeding phenomenon, and the resolution and adhesion will deteriorate.

[0132] In summary, the photosensitive resin composition and the dry film resist laminate using the solution of the present invention are beneficial to improving the product yield and production efficiency in the manufacture of printed circuit boards, and have good industrial applicability.

[0133] The foregoing are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A dry film resist laminate, characterized in that, The laminate includes a resist layer, a support layer on one side of the resist layer, and a protective layer on the other side of the resist layer. The resist layer has a first surface facing the protective layer and a second surface opposite to the first surface. The resist layer is a pre-crosslinked resist layer, and the pre-crosslinking degree of the first surface is less than that of the second surface.

2. The dry film resist laminate according to claim 1, characterized in that, The pre-crosslinking degree of the resist layer increases in the extending direction from the first surface to the second surface.

3. The dry film resist laminate according to claim 1, wherein The pre-crosslinking degree of the resist layer is not greater than 20%.

4. The dry film resist laminate according to claim 3, wherein The part of the resist layer with a pre-crosslinking degree of 0 - 5% is the low pre-crosslinking degree part, and the part with a pre-crosslinking degree of 5% - 20% is the high pre-crosslinking degree part. The thickness of the low pre-crosslinking degree part is 50% - 90% of the thickness of the resist layer, and the thickness of the high pre-crosslinking degree part is 10% - 50% of the thickness of the resist layer.

5. The dry film resist laminate according to claim 4, characterized in that, The thickness of the low pre-crosslinking degree part is 70% - 90% of the thickness of the pre-crosslinked resist layer, and the thickness of the high pre-crosslinking degree part is 10% - 30% of the thickness of the pre-crosslinked resist layer.

6. The dry film resist laminate according to claim 1, wherein The resist layer is a single-layer structure or a multi-layer structure.

7. A dry film resist laminate according to claim 1, characterized in that, The thickness of the resist layer is 15 - 60 μm.

8. The dry film resist laminate according to claim 1, characterized in that, The resist layer of the dry film resist laminate is made from a resin composition, and the resin composition includes the following components: 30 - 70 parts by mass of an alkali-soluble resin, 30 - 50 parts by mass of an ethylenically photopolymerizable unsaturated monomer, 0.1 - 5 parts by mass of an initiator, and 0.1 - 5 parts by mass of an additive.

9. The preparation method of a dry film resist laminate according to any one of claims 1-8, characterized in that, Including steps: Dissolve all components of the resist layer in an organic solvent and disperse evenly to form a mixture with a solid content of 35% - 50%. Provide a support layer, coat the mixture on one side of the support layer and then perform a drying treatment to obtain a resist preparatory layer. Perform a crosslinking treatment on the resist preparatory layer from one side of the support layer or / and from the side away from the support layer to obtain a resist layer. Attach a protective layer on the side of the resist layer away from the support layer to obtain the dry film resist laminate. Or, Dissolve all components of the resist layer in an organic solvent and disperse evenly to form a mixture with a solid content of 35% - 50%. Provide a support layer, coat the mixture on one side of the support layer and then perform a drying treatment to obtain a resist preparatory layer. Attach a protective layer on the side of the resist preparatory layer away from the support layer to obtain a laminate preparatory body. Perform a crosslinking treatment on the laminate preparatory body from one side of the support layer or / and from the side away from the support layer to obtain the dry film resist laminate.

10. The preparation method of a dry film resist laminate according to claim 9, characterized in that, The crosslinking treatment methods include laser crosslinking and ultraviolet crosslinking.

11. The preparation method of a dry film resist laminate according to claim 10, characterized in that, The energy of the crosslinking treatment is 0.1 - 18 mJ.

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