Dry film resist and photosensitive dry film

Abstract

The present invention provides a dry film resist and a photosensitive dry film. The dry film resist comprises: 45 to 60 parts by weight of an alkali-soluble resin, 35 to 50 parts by weight of a photopolymerizable monomer, 2.5 to 5 parts by weight of a photoinitiator, and 0.05 to 0.5 parts by weight of a photosensitizer. The monomer containing an aromatic group in the alkali-soluble resin accounts for more than 40% of the total amount of the alkali-soluble resin. The photopolymerizable monomer comprises a compound having a structure shown in structural formula I: #imgabs0# wherein R1 is selected from a hydrogen atom, a methyl group, a hydroxymethyl group, and an ethyl group; X is C2H4 or C3H6, m1 is an integer of 0 to 5; and R2 is independently selected from a hydrogen atom and a methyl group. By applying the technical solution of the present invention, a specific photopolymerizable monomer is used, and the resist layer can obtain a sufficient three-dimensional network cross-linked structure after laser irradiation, so that the dry film resist has a shorter residual foot during the development process, which is conducive to the dimensional stability of the conductor circuit.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic materials, and in particular to a dry film resist and a photosensitive dry film. Background Art

[0002] In the manufacturing process of printed circuit boards (PCBs), lead frames (LFs), and semiconductor package (IC) substrates, photosensitive resin compositions are widely used as resist materials for etching or plating.

[0003] As electronic devices continue to develop towards lighter and thinner, the corresponding requirements are that PCB circuits develop more refined and high-density. In the technical field of semiconductor packaging substrates, the circuit size has even reached less than 10μm. The semi-additive process (SAP) process directly forms an anti-etching pattern on thin copper, then increases the thickness of the conductor copper through pattern electroplating, then removes the anti-etching pattern, and then quickly etches to remove the exposed bottom copper to form a circuit. Because the bottom copper is thin, the etching time of the bottom copper is short, the side etching of the circuit is light, and fine circuits with a line width and line spacing of less than 25μm can be easily produced.

[0004] Laser direct imaging (LDI) has excellent alignment accuracy and can efficiently form fine resist patterns, and is widely used in the production of high-density packaging substrates. However, compared with the photomask exposure method, which exposes the entire plate at one time, the laser direct imaging method uses a point light source or a matrix light source to gradually scan out the resist pattern, which consumes more exposure time. Therefore, in order to shorten the exposure time and improve production efficiency, the photosensitivity of the photosensitive resin composition must be improved.

[0005] The continuous development of printed circuit board technology and semiconductor packaging technology promotes the development of electronic circuits towards ultra-high density and miniaturization. The circuit design of the packaging substrate can reach 5um or even below. The existing laser direct imaging (LDI) technology can form fine anti-etching patterns with a line width and line spacing of 6um, but the production efficiency is not sufficient. Photosensitizers have a direct impact on photosensitivity and resolution, and are one of the cores of the photosensitive resin composition for packaging substrates. In order to improve photosensitivity, it is usually necessary to add a suitable photosensitizer to the photosensitive resin composition. Anthracene compounds such as 9,10-dibutoxyanthracene and pyrazoline compounds are often added as photosensitizers to dry film resists used for the production of packaging substrates. For example, patent CN104111583A uses a photosensitive resin composition with a class of styrylpyrazoline as a sensitizer, which has good resolution, but its photosensitivity still has room for improvement, and the resolution cannot meet the requirements of the packaging substrate circuit. Patent CN108375874A mentions that a photosensitive resin composition with excellent resolution is obtained by adding a photosensitizer including a pyrazoline compound, anthracene compound, a triarylamine compound and an oxazole compound and an ethoxylated and propoxylated acrylate monomer to the formula. However, judging from the results of its embodiments, its photosensitivity is still insufficient.

[0006] Sometimes, in order to improve photosensitivity, the amount of photosensitizer is increased. Although this method can improve photosensitivity, it will bring about problems such as insufficient dissolution, migration and precipitation, and increased development sediments. On the other hand, when paying attention to high resolution, it is also necessary to pay attention to the bottom residual feet of the anti-etching circuit, that is, there is residual glue at the bottom of the anti-etching circuit after development. The residual feet at the bottom of the resist are caused by the swelling and expansion of the bottom of the resist during the development process, and are related to the development resistance and the degree of cross-linking at the bottom of the resist layer. The elongation of the residual feet will increase the contact area between the resist layer and the substrate, widen the actual circuit size, reduce the effective resolution, and make it difficult to ensure the dimensional stability of the resist layer. Therefore, it is of great significance to develop photosensitive resin compositions that have both high photosensitivity and high resolution, especially those with short residual feet. Summary of the invention

[0007] The main purpose of the present invention is to provide a dry film resist and a photosensitive dry film to solve the problem of long dry film resist residue in the prior art.

[0008] In order to achieve the above object, according to one aspect of the present invention, a dry film resist is provided, which comprises: 45 to 60 parts by weight of an alkali-soluble resin, 35 to 50 parts by weight of a photopolymerizable monomer, 2.5 to 5 parts by weight of a photoinitiator, and 0.05 to 0.5 parts by weight of a photosensitizer, wherein the monomer containing an aromatic group in the alkali-soluble resin accounts for more than 40% of the total amount of the alkali-soluble resin, and the photopolymerizable monomer comprises a compound having a structure shown in structural formula I.

[0009]

[0010] In the formula, R1 is selected from hydrogen atom, methyl, hydroxymethyl, ethyl; X is C2H4 or C3H6, m1 is an integer from 0 to 5; R2 is independently selected from hydrogen atom and methyl.

[0011] Furthermore, the content of the compound having the structure represented by structural formula I in the photopolymerizable monomer is 1 to 5 parts by weight, and m1 is an integer of 1 to 3.

[0012] Furthermore, the photopolymerizable monomer also includes any one or more selected from ethoxylated nonylphenol acrylate, propoxylated nonylphenol acrylate, bisphenol A dimethacrylate, ethoxylated bisphenol A dimethacrylate, propoxylated bisphenol A dimethacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate; preferably, the photopolymerizable monomer also includes ethoxylated bisphenol A dimethacrylate.

[0013] Furthermore, the alkali-soluble resin is copolymerized with (meth)acrylic acid and a copolymerization unit, and the copolymerization unit is selected from one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, benzyl (meth)acrylate, hydroxyethyl (meth)acrylate, and styrene; preferably, the copolymerization monomers of the alkali-soluble resin include methacrylic acid, methyl methacrylate, hydroxyethyl methacrylate, benzyl methacrylate, and styrene.

[0014] Furthermore, the monomer containing an aromatic group accounts for 40% to 65% of the total amount of the alkali-soluble resin.

[0015] Furthermore, the alkali-soluble resin has a weight average molecular weight of 30,000 to 80,000, an acid value of 150 to 220 mg KOH / g, and a molecular weight distribution index of 1.0 to 3.0.

[0016] Further, the photoinitiator is a triaryl imidazole dimer derivative, and the photoinitiator is preferably selected from any one or more of 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole, preferably 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer.

[0017] Furthermore, the photosensitizer includes a compound having a structure shown in structural formula II,

[0018]

[0019] In structural formula II, R is the structure shown in structural formula III:

[0020]

[0021] In structural formula III, A is selected from any one of a nitrogen atom, an oxygen atom, and a sulfur atom; R3 is a substituent, and R3 is selected from any one of hydrogen, Cl, Br, and a C1-C4 alkyl group; the content of the compound having the structure shown in structural formula II is preferably 0.05-0.5 parts by weight.

[0022] Furthermore, the dry film resist further comprises additives, and the additives comprise any one or more of dyes, colorants, plasticizers, defoamers, leveling agents, and polymerization inhibitors, and the additive content is preferably 0.5 to 5.0 parts by weight.

[0023] According to another aspect of the present invention, a photosensitive dry film is provided, comprising: a dry film resist layer and a support layer and a protective layer located on both sides of the dry film resist layer, wherein the dry film resist layer comprises any one of the above dry film resists.

[0024] By applying the technical solution of the present invention, a specific photopolymerizable monomer is used, and the resist layer can obtain a sufficient three-dimensional network cross-linked structure after laser irradiation, so that the dry film resist has a shorter residual foot during the development process, which is helpful for the dimensional stability of the conductor circuit; and the dry film resist of a special composition is used, so that the comprehensive properties of the dry film resist of the present application, such as photosensitivity, resolution, adhesion, etc., are relatively excellent, and can be widely used in the manufacturing process of printed circuit boards (PCBs), lead frames (LFs), and semiconductor packaging (IC) substrates, which helps to improve production efficiency and yield rate. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0026] As analyzed in the background technology of the present application, there is a problem in the prior art that the dry film resist has a long residual foot. In order to solve this problem, the present application provides a dry film resist and a photosensitive dry film.

[0027] In a typical embodiment of the present application, a dry film resist is provided, which includes 45 to 60 parts by weight of an alkali-soluble resin, 35 to 50 parts by weight of a photopolymerizable monomer, 2.5 to 5 parts by weight of a photoinitiator, and 0.05 to 0.5 parts by weight of a photosensitizer, wherein the monomer containing an aromatic group in the alkali-soluble resin accounts for more than 40% of the total amount of the alkali-soluble resin, and the photopolymerizable monomer includes a compound having a structure shown in structural formula I.

[0028]

[0029] In the formula, R1 is selected from hydrogen atom, methyl, hydroxymethyl, ethyl; X is C2H4 or C3H6, m1 is an integer from 0 to 5; R2 is independently selected from hydrogen atom and methyl.

[0030] Since the present application adopts a specific photopolymerizable monomer, the resist layer can obtain a sufficient three-dimensional network cross-linked structure after laser irradiation, so that the dry film resist has a shorter residual foot during the development process, which is helpful for the dimensional stability of the conductor line; and the dry film resist of the present application adopts a special composition, so that the comprehensive properties such as photosensitivity, resolution, adhesion, etc. of the dry film resist are relatively excellent, and can be widely used in the manufacturing process of printed circuit boards (PCBs), lead frames (LFs), and semiconductor packaging (IC) substrates, which helps to improve production efficiency and yield rate.

[0031] Examples of the compound having the structure represented by formula I include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated (3) trimethylolpropane triacrylate, propoxylated (3) trimethylolpropane triacrylate, ethoxylated (3) trimethylolpropane trimethacrylate, propoxylated (3) trimethylolpropane trimethacrylate, ethoxylated (6) trimethylolpropane triacrylate, propoxylated (6) trimethylolpropane triacrylate, ethoxylated (6) trimethylolpropane trimethacrylate, propoxylated (6) trimethylolpropane trimethacrylate, ethoxylated (9) trimethylolpropane triacrylate, propoxylated (9) trimethylolpropane triacrylate, ethoxylated (9) trimethylolpropane trimethacrylate, propoxylated (9) trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, Ethoxylated (3) pentaerythritol triacrylate, ethoxylated (3) pentaerythritol trimethacrylate, propoxylated (3) pentaerythritol triacrylate, propoxylated (3) pentaerythritol trimethacrylate, ethoxylated (6) pentaerythritol triacrylate, ethoxylated (6) pentaerythritol trimethacrylate, propoxylated (6) pentaerythritol triacrylate, propoxylated (6) pentaerythritol trimethacrylate, ethoxylated (9) pentaerythritol alcohol triacrylate, ethoxylated (9) pentaerythritol trimethacrylate, propoxylated (9) pentaerythritol triacrylate, propoxylated (9) pentaerythritol trimethacrylate, ethoxylated (15) trimethylolpropane triacrylate, etc., wherein, when ethoxylated (3) trimethylolpropane triacrylate is represented by structural formula I, R1 is ethyl, m1 is 1, R2 is hydrogen, and other compounds are named according to conventional naming methods, which are not described one by one here. In some embodiments of the present application, in order to further enhance the inhibitory effect of the dry film resist on the bottom residual foot and increase its stripping speed, R1 in structural formula I is selected from hydrogen atom, methyl, hydroxymethyl, X is C2H4, and preferably, m1 is an integer of 1 to 3.

[0032] In addition to the compound shown in structural formula I, the above-mentioned photopolymerizable monomers may also include other types of photopolymerizable monomers selected from the prior art. In some preferred embodiments of the present application, the content of the compound having the structure shown in structural formula I in the photopolymerizable monomer is 1 to 5 parts by weight. If its content is too low, the inhibitory effect on the bottom residual foot of the dry film resist layer is not obvious; if its content is too high, the stripping time of the resist layer will be prolonged.

[0033] The above-mentioned photopolymerizable monomers may also include other ethylenically unsaturated double-bond monomers, such as any one or more of ethoxylated nonylphenol acrylate, propoxylated nonylphenol acrylate, bisphenol A dimethacrylate, ethoxylated bisphenol A dimethacrylate, propoxylated bisphenol A dimethacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate. In some preferred embodiments of the present application, in order to further improve the resolution of the dry film resist, the photopolymerizable monomers also include ethoxylated bisphenol A dimethacrylate.

[0034] The total weight of the above-mentioned photopolymerizable monomers is 35 to 50. If the weight of the photopolymerizable monomers is less than 35, the photosensitive resin composition is prone to low sensitivity and low resolution. If the weight is higher than 50, the photosensitive layer is prone to overflow, resulting in a shortened effective period of the resist.

[0035] The above-mentioned alkali-soluble resin can be selected from the prior art. In some embodiments of the present application, the alkali-soluble resin is copolymerized with (meth) acrylic acid and a copolymerization unit, and the copolymerization unit is selected from methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, benzyl (meth) acrylate, hydroxyethyl (meth) acrylate, and styrene. For example, the alkali-soluble resin is copolymerized with acrylic acid and methyl acrylate, methyl methacrylate, butyl acrylate, benzyl acrylate, and hydroxyethyl methacrylate. In some preferred embodiments of the present application, the alkali-soluble resin is copolymerized with methacrylic acid, methyl methacrylate, hydroxyethyl (meth) acrylate, benzyl methacrylate, and styrene. The dry film resist using the alkali-soluble resin of this combination has better performance, not only has a better effect of suppressing the bottom residual foot, but also has better resolution and adhesion.

[0036] In some preferred embodiments of the present application, the copolymerized units are monomers containing aromatic groups, preferably the monomers containing aromatic groups account for 40% to 65% of the total amount of the alkali-soluble resin, and the alkali-soluble resin having such a composition has a better comprehensive effect in terms of improving the resolution and adhesion of the dry film resist, as well as inhibiting the bottom residual foot and improving the film stripping effect. Preferably, the copolymerized units containing aromatic groups in the alkali-soluble resin account for 42% to 60% of the total amount of the alkali-soluble resin, such as 45%, 50%, or 55%.

[0037] In some embodiments of the present application, the weight average molecular weight of the alkali-soluble resin is 30,000 to 80,000, the acid value is 150 to 220 mg KOH / g, and the molecular weight distribution index is 1.0 to 3.0. The alkali-soluble resin meeting the above indicators has further improved development resistance, resolution and bottom residual foot suppression performance. In particular, when the molecular weight distribution index of the resin exceeds 3.0, there is a risk of decreased resolution and longer bottom residual feet.

[0038] The above-mentioned photoinitiator can be selected from the prior art, for example, from triaryl imidazole dimer derivatives. Preferably, the photoinitiator is selected from any one or more of 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole, and preferably the photoinitiator is 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer.

[0039] The above-mentioned photosensitizer can also be selected from the prior art. In some embodiments of the present application, the photosensitizer includes a compound having a structure shown in structural formula II,

[0040]

[0041] In the above structural formula II, R is the structure shown in structural formula III, in which A is selected from any one of nitrogen atom, oxygen atom and sulfur atom; R3 is a substituent, and R3 is selected from any one of hydrogen, Cl, Br and C1-C4 alkyl; the binding position of imidazole in structural formula II and structural formula I can be on the benzene ring of the structure shown in structural formula II or on its heterocyclic ring. In some preferred embodiments of the present application, in structural formula II, A is selected from any one of nitrogen atom, oxygen atom and sulfur atom; R3 is selected from any one of Cl and Br; the binding position of imidazole in structural formula II and structural formula I is located on the heterocyclic ring of structural formula II. When the photoinitiator is the above structure, the developing performance and photosensitivity of the formed photosensitive resin composition are more excellent.

[0042] The photosensitizer compound having the structure shown in the structural formula II can be exemplified by 2-(2-indole)-4,5-diphenylimidazole dimer, 2-(3-indole)-4,5-diphenylimidazole dimer, 2-(6-indole)-4,5-diphenylimidazole dimer, 2-(7-indole)-4,5-diphenylimidazole dimer, 2-(5-chloro-2-indole)-4,5-diphenylimidazole dimer, 2-(5-bromo-2-indole)-4,5-diphenylimidazole dimer, 2-(1-chloro-3-indole)-4,5-diphenylimidazole dimer, 2-(2-chloro-3-indole)-4,5-diphenylimidazole dimer, 2-(4-chloro-3-indole)-4,5-diphenylimidazole dimer 2-(5-chloro-3-indole)-4,5-diphenylimidazole dimer, 2-(6-chloro-3-indole)-4,5-diphenylimidazole dimer, 2-(7-chloro-3-indole)-4,5-diphenylimidazole dimer, 2-(5-bromo-3-indole)-4,5-diphenylimidazole dimer, 2-(7-bromo-3-indole)-4,5-diphenylimidazole dimer, 2-(3-benzofuran)-4,5-diphenylimidazole dimer, 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole dimer, 2-(7-methyl-2-benzofuran)-4,5-diphenylimidazole dimer, 2-(3-benzofuran)-4,5-diphenylimidazole dimer, 2-(2 2-(6-Benzofuran)-4,5-diphenylimidazole dimer, 2-(6-methyl-7-benzofuran)-4,5-diphenylimidazole dimer, 2-(2-benzothiophene)-4,5-diphenylimidazole dimer, 2-(3-methyl-2-benzothiophene)-4,5-diphenylimidazole dimer, 2-(3-chloro-2-benzothiophene)-4,5-diphenylimidazole dimer, 2-(5-chloro-2-benzothiophene)-4,5-diphenylimidazole dimer, -(7-bromo-2-benzothiophene)-4,5-diphenylimidazole dimer, 2-(3-benzothiophene)-4,5-diphenylimidazole dimer, 2-(2-methyl-3-benzothiophene)-4,5-diphenylimidazole dimer, 2-(2-ethyl-3-benzothiophene)-4,5-diphenylimidazole dimer, 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole dimer, 2-(5-bromo-3-benzothiophene)-4,5-diphenylimidazole dimer, 2-(5-chloro-3-benzothiophene)-4,5-diphenylimidazole dimer, 2-(4-benzothiophene)-4,5-diphenylimidazole dimer, 2-(6-benzothiophene)-4,5-diphenylimidazole dimer, and the like.Preferably, the content of the compound having the structure represented by structural formula II is 0.05 to 0.5 parts by weight. If the content of the photosensitizer having the structure is too high, there is a risk of poor resolution of the dry film resist layer and longer bottom residual feet.

[0043] For the convenience of production, the dry film resist may further include additives, including any one or more of dyes, colorants, plasticizers, defoamers, leveling agents, and inhibitors, and the additive content is preferably 0.5 to 5.0 parts by weight.

[0044] According to another typical embodiment of the present application, a photosensitive dry film is provided, which includes: a dry film resist layer and a support layer and a protective layer located on both sides of the dry film resist layer, wherein the dry film resist layer includes any one of the dry film resists.

[0045] The photosensitive dry film of the present invention has a short residual foot size, and has relatively excellent comprehensive properties such as photosensitivity, resolution, and adhesion. It can be widely used in the manufacturing process of printed circuit boards (PCBs), lead frames (LFs), and semiconductor packaging (IC) substrates, and helps to improve production efficiency and yield rate.

[0046] The beneficial effects of the present application will be further illustrated below with reference to examples and comparative examples.

[0047] (1) Synthesis of photosensitizer 2-(5-bromo-2-indole)-4,5-diphenylimidazole dimer (D-1)

[0048] The raw materials, benzil (McLean) and 5-bromoindole-2-carboxaldehyde (McLean), were purchased from the market.

[0049] First, benzil (31.5, 0.15 mol), 5-bromoindole-2-carboxaldehyde (40.3 g, 0.18 mol), ammonium acetate (67.5 g, 0.88 mol), and glacial acetic acid (160 mL) were added to a 500 mL flask equipped with stirring, reflux cooling, and nitrogen protection. The reaction mixture was refluxed for 12 h under nitrogen protection and cooled to room temperature. The reaction mixture was poured into 5% potassium hydrogen sulfate solution (200 mL) to obtain a white precipitate, which was filtered. The solid was first washed with 5% NaOH solution and then washed with water until neutral. After drying, the intermediate 2-(5-bromo-2-indole)-4,5-diphenylimidazole (61 g, purity 95%) was obtained.

[0050] Into a 500mL flask equipped with stirring, reflux cooling and nitrogen protection, add 2-(5-bromo-2-indole)-4,5-diphenylimidazole (20.0g), 30% NaOH (24.0g), tetrabutylammonium bromide (1.0g) and toluene (150mL), heat and stir, add 10% sodium hypochlorite solution (32.0g) dropwise at a temperature of 60-65°C for 20min. After the addition is completed, maintain the reaction at 60-65°C for 5h, take samples and monitor the reaction by HPLC and LCMS, and stop the reaction when the content of the raw material 2-(5-bromo-2-indole)-4,5-diphenylimidazole is less than 1%. After the reaction is completed, the suspension obtained by the reaction is centrifuged, washed with water, centrifuged, washed with methanol, centrifuged, and dried to obtain the product 2-(5-bromo-2-indole)-4,5-diphenylimidazole dimer D-1 (16 g, purity 97%).

[0051] (2) Synthesis of photosensitizer 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole dimer (D-2)

[0052] The raw materials, benzil (McLean) and 5-bromo-1-benzofuran-2-carboxaldehyde (Shanghai Aladdin), were purchased from the market.

[0053] First, benzil (21.0 g, 0.1 mol), 5-bromo-1-benzofuran-2-carboxaldehyde (27.0 g, 0.12 mol), ammonium acetate (45 g, 0.58 mol), and glacial acetic acid (100 mL) were added to a 500 mL flask equipped with stirring, reflux cooling, and nitrogen protection. The reaction mixture was refluxed for 12 h under nitrogen protection and cooled to room temperature. The reaction mixture was poured into 5% potassium hydrogen sulfate solution (150 mL) to obtain a white precipitate, which was filtered. The solid was first washed with 5% NaOH solution and then washed with water until neutral. After drying, the intermediate 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole (39 g, purity 96%) was obtained.

[0054] Into a 500mL flask equipped with stirring, reflux cooling and nitrogen protection, add 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole (20.0g), 30% NaOH (25.0g), tetrabutylammonium bromide (1.0g) and toluene (150mL), heat and stir, add 10% sodium hypochlorite solution (40.0g) dropwise at a temperature of 60-65°C for 30min. After the addition is completed, maintain the reaction at 60-65°C for 5h, take samples and monitor the reaction by HPLC and LCMS, and stop the reaction when the content of the raw material 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole is less than 1%. After the reaction is completed, the suspension obtained by the reaction is centrifuged, washed with water, centrifuged, washed with methanol, centrifuged, and dried to obtain the product 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole dimer D-2 (17 g, purity 97%).

[0055] (3) Synthesis of photosensitizer 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole dimer (D-3)

[0056] The raw materials, benzil (McLean) and 2-bromobenzothiophenol-3-carboxaldehyde (Foshan Haer Biotechnology) were purchased from the market.

[0057] First, add benzil (10.5g, 0.050mol), 2-bromobenzothiophene-3-carboxaldehyde (14.5g, 0.06mol), ammonium acetate (22g, 0.29mol), and glacial acetic acid (50mL) to a 500mL flask equipped with stirring, reflux cooling, and nitrogen protection. The reaction mixture is refluxed for 12h under nitrogen protection and cooled to room temperature. The reaction mixture is poured into 5% potassium hydrogen sulfate solution (100mL) to obtain a white precipitate, which is filtered. The solid is first washed with 5% NaOH solution and then washed with water until neutral. After drying, the intermediate 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole (17g, purity 94%) is obtained.

[0058] Into a 500mL flask equipped with stirring, reflux cooling and nitrogen protection, add 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole (10.0g), 30% NaOH (15.0g), tetrabutylammonium bromide (0.5g) and toluene (100mL), heat and stir, add 10% sodium hypochlorite solution (20.0g) dropwise at a temperature of 60-65°C for 15min. After the addition is completed, maintain the reaction at 60-65°C for 5h, take samples and monitor the reaction by HPLC and LCMS, and stop the reaction when the content of the raw material 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole is less than 1%. After the reaction is completed, the suspension obtained by the reaction is centrifuged, washed with water, centrifuged, washed with methanol, centrifuged, and dried to obtain the product 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole dimer D-3 (8.6 g, purity 98%).

[0059] According to the formula of Table 1 and Table 2 (Example and Comparative Example), the components are mixed in proportion, 60 parts by weight of acetone is added, and then stirred until completely dissolved to prepare a resin composition solution with a solid content of 40%. It is evenly coated on the surface of a PET support film with a thickness of 15um using a coating machine, and placed in a 95℃ oven for 6 minutes to form a dry film resist layer with a thickness of 25um, which appears blue-green under a yellow light. Then, a polyethylene film protective layer with a thickness of 20um is attached to its surface to obtain a photosensitive dry film with a 3-layer structure.

[0060] Table 1

[0061]

[0062]

[0063] Table 2

[0064]

[0065] In the table, the alkali-soluble resin, photopolymerization monomer, photoinitiator, photosensitizer and additives are as follows:

[0066] Alkali soluble resins are prepared by solution polymerization:

[0067] A-1: main components: methacrylic acid / methyl methacrylate / hydroxyethyl methacrylate / benzyl methacrylate / styrene = 30 / 5 / 5 / 25 / 35 (weight average molecular weight 45,000, acid value 195.7 mg KOH / g, molecular weight distribution index 1.9);

[0068] A-2: main components: methacrylic acid / methyl methacrylate / hydroxyethyl methacrylate / benzyl methacrylate / styrene = 25 / 20 / 7 / 20 / 28 (weight average molecular weight 65,000, acid value 163.1 mg KOH / g, molecular weight distribution index 2.2);

[0069] A-3: main components: methacrylic acid / methyl methacrylate / hydroxyethyl methacrylate / benzyl methacrylate / styrene = 23 / 40 / 5 / 10 / 22 (weight average molecular weight 50,000, acid value 150.0 mg KOH / g, molecular weight distribution index 2.1);

[0070] A-4: main components: methacrylic acid / hydroxyethyl methacrylate / benzyl methacrylate / styrene = 28 / 2 / 20 / 50 (weight average molecular weight 49,000, acid value 182.7 mg KOH / g, molecular weight distribution index 2.3).

[0071] Photopolymerizable monomers:

[0072] B-1: (4) Ethoxylated bisphenol A dimethacrylate, molecular weight 540 (Meiyuan Chemical)

[0073] B-2: (10) Ethoxylated bisphenol A dimethacrylate, molecular weight 804 (Meiyuan Chemical)

[0074] B-3: (9) Ethoxylated dimethacrylate, molecular weight 598 (Sartomer)

[0075] B-4: (4) Ethoxylated nonylphenol acrylate, 450 molecular weight (Meiyuan Chemical)

[0076] B-5: Ethoxylated (3) trimethylolpropane triacrylate, molecular weight 428 (Sartomer)

[0077] B-6: Ethoxylated (9) trimethylolpropane triacrylate, molecular weight 693 (Sartomer)

[0078] B-7: Ethoxylated (15) trimethylolpropane triacrylate, molecular weight 956 (Sartomer)

[0079] B-8: propoxylated (3) pentaerythritol triacrylate, molecular weight 472 (Sartomer)

[0080] Photoinitiator:

[0081] C-1: 2-(2-chlorophenyl)-4,5-diphenylimidazole dimer (Changzhou Qiangli Electronic Materials)

[0082] Photosensitizer:

[0083] D-1: 2-(5-bromo-2-indole)-4,5-diphenylimidazole dimer, as shown in Synthesis Example D-1.

[0084] D-2: 2-(5-bromo-2-benzofuran)-4,5-diphenylimidazole dimer, as synthesized in Example D-2.

[0085] D-3: 2-(2-bromo-3-benzothiophene)-4,5-diphenylimidazole dimer, as shown in Synthesis Example D-3.

[0086] D-4: 9,10-Dibutoxyanthracene (Shanghai Diweigao)

[0087] additive:

[0088] E-1 (dye): Malachite green (Shanghai Bailingwei Chemical Technology Co., Ltd.)

[0089] E-2 (color former): Leuco crystal violet (Shanghai Bailingwei Chemical Technology Co., Ltd.)

[0090] E-3 (stabilizer): 4-tert-butylcatechol (Shanghai Bailingwei Chemical Technology Co., Ltd.)

[0091] E-4 (plasticizer): p-Toluenesulfonamide (Shanghai TCI Chemical)

[0092] The following describes the sample preparation method (including film application, exposure, development, and film stripping), sample evaluation method, and evaluation results of the embodiments and comparative examples.

[0093]

Film

[0094] The copper surface of the copper clad laminate was polished by a grinder, washed with water, and dried to obtain a bright and fresh copper surface. The laminating machine roller temperature was set to 110°C and the conveying speed was 1.5 m / min. After removing the PE protective film on the surface of the photosensitive dry film obtained in the above embodiment and comparative example, it was thermally laminated to the copper clad laminate under standard pressure to obtain a laminated sample.

[0095]

exposure

[0096] After film application, the sample was left to stand for more than 15 minutes and then exposed using an Adtec IP-6 exposure machine with 13-17 exposure grids to obtain the exposed sample.

[0097]

development

[0098] After exposure, the sample was left to stand for more than 15 minutes, the developing temperature was 30°C, and the pressure was 1.2Kg / cm 2The developer is a 1%wt sodium carbonate aqueous solution, and the developing time is 1.5-2.0 times the minimum developing time. After developing, the resist layer of the unexposed part is washed and dried. The minimum developing time is the time required for the resist layer of the unexposed part to be completely dissolved through the developing tank section.

[0099]

Removal of film

[0100] The stripping solution is a NaOH aqueous solution with a concentration of 3.0wt%, a temperature of 50°C, and a developing pressure of 1.2Kg / cm 2 .

[0101]

Evaluation of photosensitivity

[0102] After lamination, the sample was left to stand for more than 15 minutes, and then exposed using an Adtec IP-6 exposure machine. The sensitivity test was performed using a stouffer 41-step exposure ruler. After exposure, the sample was left to stand for more than 15 minutes, and then sprayed with a 1%wt sodium carbonate aqueous solution at 30°C. The development time was 2.0 times the minimum development time, thereby removing the unexposed part. After this operation, a cured film formed by the cured product of the photosensitive resin composition was formed on the copper surface of the substrate. The exposure amount (mJ / cm 2 ), the photosensitivity of the photosensitive resin composition was evaluated. The smaller the value, the better the photosensitivity.

[0103] Judgment basis

[0104] ○: 20-30mJ / cm 2

[0105] △: 30-40mJ / cm 2

[0106] ×:>40mJ / cm 2

[0107] [Evaluation of resolution]

[0108] Exposure is performed using a mask having a wiring pattern with an exposed portion and an unexposed portion having a width of n:n (n is 5 to 25 μm). After development for 2.0 times the minimum development time, the minimum mask width at which a cured resist line is normally formed is taken as the resolution value and observed using a magnifying glass.

[0109]

Evaluation of residual foot size

[0110] A photosensitive dry film resist is laminated on a copper plate by hot pressing, and exposed using a mask having a wiring pattern with an exposed portion and an unexposed portion having a width of 15:400 (μm). After development with 2.0 times the minimum development time, a sample of the circuit formed by the cured resist line is cut, and then a scanning electron microscope (SEM) is used to measure the length of the residual foot at the bottom of the resist circuit. The shorter the length, the better the resolution effect.

[0111] The basis for judging whether the residual foot is good or bad

[0112] ○:0-0.5um

[0113] △: 0.6-0.9um

[0114] ×: 1.0um or more

[0115]

Evaluation of adhesion

[0116] A photosensitive dry film resist was laminated on a copper plate by hot pressing, and exposure was performed using a mask having a wiring pattern with a width of n:400 (n is 5 to 25 μm) between the exposed and unexposed parts. After development for 2.0 times the minimum development time, the minimum mask width at which a cured resist line was normally formed was used as the adhesion value and observed using a magnifying glass.

[0117]

Evaluation of film stripping speed

[0118] Take a substrate after filming, exposure and development, cut it into a 4*5cm square, put it into a beaker containing 100mL of film stripping solution (concentration 3wt%, temperature 50℃), stir it with magnetic force for 1min, and record the time when the dry film is completely detached. The film stripping speed is evaluated by testing the film stripping time. The shorter the film stripping time, the faster the film stripping speed.

[0119] Table 3

[0120]

[0121] Table 4

[0122]

[0123] Through the examples and comparative examples, it can be found that examples 1-8 all obtained photosensitive resin compositions with excellent performance in terms of photosensitivity, resolution, adhesion, and residual foot size. In example 9, the copolymerization ratio of the aromatic copolymerization unit in the alkali-soluble resin is higher than 65% relative to the total mass of all monomers, and the adhesion performance and resolution are excellent, but the film stripping time is long, which will affect the production efficiency; although a trifunctional photopolymerization monomer with a specific structure is added in example 10, due to its large number of hydrophilic ethoxylated units, it is easy to cause excessive water absorption of the anti-etching pattern, expansion and deformation of the circuit, and a tendency to reduce the resolution; in example 12, an excessive amount of a trifunctional photopolymerization monomer with a specific structure is added, although the resolution, residual foot and other properties are excellent, the film stripping time is long; in example 14, although a large amount of commonly used anthracene photosensitizers are added, the photosensitivity is still insufficient; in example 15, the amount of modified triaryl imidazole dimer is large, and the photosensitivity is excellent, but due to insufficient curing of the bottom of the dry film resist layer, it is easy to cause the resolution and adhesion to decrease, and the residual foot becomes longer.

[0124] The copolymerization ratio of the aromatic copolymer units in the alkali-soluble resin in Comparative Example 1 is less than 40% relative to the total mass of all monomers, and the adhesion and resolution are obviously insufficient; in Comparative Example 2, no trifunctional monomer with a specific structure is added, and the residual foot size is long, which can easily cause inaccurate resolution and affect the dimensional stability of the conductor line.

[0125] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: due to the use of specific photopolymerizable monomers, the anti-etching layer can obtain a sufficient three-dimensional network cross-linked structure after laser irradiation, so that the dry film resist has a shorter residual foot during the development process, which is helpful for the dimensional stability of the conductor line; and the use of a special composition of dry film resist makes the photosensitivity, resolution, adhesion and other comprehensive properties of the dry film resist of the present application relatively excellent, and can be widely used in the manufacturing process of printed circuit boards (PCBs), lead frames (LFs), and semiconductor packaging (IC) substrates, which helps to improve production efficiency and yield rate.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dry film resist, characterized in that: include: 45-60 parts by weight of an alkali-soluble resin, 35-50 parts by weight of a photopolymerizable monomer, 2.5-5 parts by weight of a photoinitiator, and 0.05-0.5 parts by weight of a photosensitizer, wherein the monomer containing an aromatic group in the alkali-soluble resin accounts for more than 40% of the total amount of the alkali-soluble resin, and the photopolymerizable monomer includes a compound having a structure shown in structural formula I, In the formula, R1 is selected from hydrogen atom, methyl, hydroxymethyl, ethyl; X is C2H4 or C3H6, m1 is an integer of 0 to 5; R2 is independently selected from hydrogen atom, methyl; The photosensitizer includes a compound having a structure shown in structural formula II, In the structural formula II, R is the structure shown in the structural formula III: In the structural formula III, A is selected from any one of a nitrogen atom, an oxygen atom, and a sulfur atom; R3 is a substituent, and R3 is selected from any one of hydrogen, Cl, Br, and a C1-C4 alkyl group.

2. The dry film resist according to claim 1, characterized in that The content of the compound having the structure shown in structural formula I in the photopolymerizable monomer is 1 to 5 parts by weight.

3. The dry film resist according to claim 2, characterized in that: The m1 is an integer of 1-3.

4. The dry film resist according to claim 2, characterized in that: The photopolymerizable monomers also include any one or more selected from ethoxylated nonylphenol acrylate, propoxylated nonylphenol acrylate, bisphenol A dimethacrylate, ethoxylated bisphenol A dimethacrylate, propoxylated bisphenol A dimethacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate.

5. The dry film resist according to claim 4, characterized in that: The photopolymerizable monomer further includes ethoxylated bisphenol A dimethacrylate.

6. The dry film resist according to claim 1, characterized in that: The alkali-soluble resin is copolymerized with (meth)acrylic acid and copolymerization units, and the copolymerization units are selected from one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, benzyl (meth)acrylate, hydroxyethyl (meth)acrylate, and styrene.

7. The dry film resist according to claim 6, characterized in that: The comonomers of the alkali-soluble resin include methacrylic acid, methyl methacrylate, hydroxyethyl methacrylate, benzyl methacrylate and styrene.

8. The dry film resist according to claim 6, characterized in that: The monomer containing aromatic groups accounts for 40% to 65% of the total amount of the alkali-soluble resin.

9. The dry film resist according to claim 8, characterized in that: The alkali-soluble resin has a weight average molecular weight of 30,000 to 80,000, an acid value of 150 to 220 mg KOH / g, and a molecular weight distribution index of 1.0 to 3.

0.

10. The dry film resist according to claim 1, characterized in that: The photoinitiator is a triaryl imidazole dimer derivative.

11. The dry film resist according to claim 10, characterized in that: The photoinitiator is selected from any one or more of 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, and 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-biimidazole.

12. The dry film resist according to claim 11, characterized in that: The photoinitiator is 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer.

13. The dry film resist according to claim 1, characterized in that: The content of the compound having the structure represented by structural formula II is 0.05 to 0.5 parts by weight.

14. The dry film resist according to any one of claims 1 to 13, characterized in that: The dry film resist further comprises additives, and the additives comprise any one or more of dyes, colorants, plasticizers, defoamers, leveling agents, and inhibitors.

15. The dry film resist according to claim 14, characterized in that: The content of the additive is 0.5 to 5.0 parts by weight.

16. A photosensitive dry film, characterized in that: The photosensitive dry film comprises: a dry film resist layer and a support layer and a protective layer located on both sides of the dry film resist layer, wherein the dry film resist layer comprises the dry film resist according to any one of claims 1 to 15.

Images