Photosensitive dry film laminate, preparation method and circuit board

Abstract

The present invention discloses a photosensitive dry film laminate, the photosensitive dry film laminate comprises a substrate layer and a photosensitive layer, the photosensitive layer comprises a first photosensitive layer and a second photosensitive layer, the first photosensitive layer and the second photosensitive layer are located on the same side of the substrate layer and the second photosensitive layer is arranged away from the substrate layer; the energy required for the samples made of the first photosensitive layer and the second photosensitive layer when the exposure grid number of the stouffer21-step exposure ruler is 7 steps is recorded as A and B; wherein 50mJ≤A‑B≤700mJ, 50mJ≤A≤900mJ, 50mJ≤B≤200mJ. The present invention also discloses a preparation method and a circuit board of the above-mentioned laminate. The photosensitive dry film laminate of the present invention has good gold resistance, storage stability, and analytical properties, simple process, and is suitable for industrial promotion.

Description

Technical Field

[0001] The invention relates to the technical field of photoresists, and in particular to a photosensitive dry film laminate, a preparation method and a circuit board. Background Art

[0002] When installing electronic devices on printed circuit boards for electronic equipment, in order to prevent solder from falling on other areas, solder resist is often used to form a solder resist layer on the circuit board to cover it. The solder resist layer can also protect the circuit board in an environment with high temperature, humidity, pollutants or corrosive gases. At present, the mainstream solder resist is solder resist ink; when used, the ink needs to be applied to the circuit board to solidify into a film. In addition, dry film solder resist has also been proposed; the solder resist is applied to the substrate to form a photosensitive dry film, and the photosensitive dry film is directly attached to the circuit board during the circuit board manufacturing process. The latter can omit the process of curing the film, and the solder resist layer formed is smoother.

[0003] In the circuit board structure, the chemical nickel-gold layer has many functions such as solderability, conduction, heat dissipation, and flat coating, which conforms to the trend of increasingly complex circuit design of electronic equipment. Therefore, the chemical nickel-gold process is widely used in circuit board manufacturing. However, after chemical nickel-gold deposition, the solder mask on the circuit board is very easy to turn white or even peel off, resulting in short circuits and electrochemical corrosion between conductors due to moisture, chemicals, etc., and tinning during production and assembly, losing insulation and protection. Improving the resistance of the solder mask to gold is a powerful measure to eliminate the phenomenon of circuit solder mask peeling.

[0004] In order to improve the resistance of solder mask to metal oxide, people have made a lot of efforts. Patent CN103145988B uses a polyimide oligomer with a specific structure as the main resin to prepare a liquid photosensitive solder mask ink, which has excellent resistance to metal oxide; however, the resin itself is difficult to prepare, the use of liquid photosensitive solder mask ink is cumbersome and inconvenient, and the surface of the formed solder mask layer is not smooth enough. Patent CN1088526C adds nano-level intercalated clay, and because it can be dispersed to the nanometer scale, it can make the ink film more solid, thereby increasing its resistance to metal oxide, but the cost is high.

[0005] In summary, how to provide a photosensitive dry film with excellent chemical resistance and other properties that meet the requirements is an urgent problem to be solved. Summary of the invention

[0006] The object of the present invention is to solve the above-mentioned problems and provide a photosensitive dry film laminate having excellent chemical resistance.

[0007] To achieve the above purpose, the technical method adopted by the present invention is as follows:

[0008] A photosensitive dry film laminate, the photosensitive dry film laminate comprising a substrate layer and a photosensitive layer, the photosensitive layer comprising a first photosensitive layer and a second photosensitive layer, the first photosensitive layer and the second photosensitive layer being located on the same side of the substrate layer and the second photosensitive layer being arranged away from the substrate layer; the first photosensitive layer and the second photosensitive layer satisfy the following requirements: a first photosensitive layer of 30 cm×20 cm×10 um is arranged on a PET film of 30 cm×20 cm×15 um to form a laminate 1, the laminate 1 is laminated to a copper clad laminate of 30 cm×20 cm with the first photosensitive layer close to the copper surface of the copper clad laminate at 70°C and a pressure of 4 kg to form a sample 1, the sample ... The energy required when the exposure number of the 21-step exposure ruler (Stouffer Company, USA) is 7 steps is recorded as A; a second photosensitive layer of 30cm×20cm×10um is set on another 30cm×20cm×15um PET film to form a laminate 2, and the laminate 2 is laminated to a 30cm×20cm copper clad laminate with the second photosensitive layer close to the copper surface of the copper clad laminate at 70°C and 4 kg pressure to form a sample 2. The energy required when the exposure number of the sample 2 is 7 steps on the Stouffer 21-step exposure ruler is recorded as B; wherein, 50mJ≤AB≤700mJ, 50mJ≤A≤900mJ, 50mJ≤B≤200mJ.

[0009] Furthermore, the first photosensitive layer and the second photosensitive layer are formed by curing a first photosensitive resin composition and a second photosensitive resin composition, respectively, wherein the first photosensitive resin composition includes (A1) a main resin, (B1) an initiator, (C1) a curing agent, and (D1) a filler; the second photosensitive resin composition includes (A2) a main resin, (B2) an initiator, (C2) a curing agent, and (D2) a filler, and the mass ratio of the filler (D2) to the filler (D1) is 0 to 0.7.

[0010] Furthermore, the first photosensitive resin composition and the second photosensitive resin composition further include (E1) reactive monomers and (E2) reactive monomers, respectively, wherein the double bond equivalent of the (E1) reactive monomers is 100 to 600 g / mol, and the double bond equivalent of the (E2) reactive monomers is 100 to 600 g / mol.

[0011] Furthermore, the double bond equivalent in the reactive monomer (E1) is recorded as M, and the double bond equivalent in the reactive monomer (E2) is recorded as N, and -0.1≤(MN) / (M+N)≤0.1.

[0012] Furthermore, in terms of parts by mass, the first photosensitive resin composition comprises 100 parts by mass of a main resin (A1), 0 to 5 parts by mass of an initiator (B1), 5 to 20 parts by mass of a curing agent (C1), 5 to 20 parts by mass of a filler (D1), and 10 to 50 parts by mass of a reactive monomer (E1); and the second photosensitive resin composition comprises 100 parts by mass of a main resin (A2), 0 to 5 parts by mass of an initiator (B2), 5 to 20 parts by mass of a curing agent (C2), 0 to 5 parts by mass of a filler (D2), and 10 to 50 parts by mass of a reactive monomer (E2).

[0013] Furthermore, the L value of the first photosensitive layer is 92 to 99, the a value is -2 to 2, and the b value is -2 to 5; the L value of the second photosensitive layer is 70 to 100, the a value is -2.5 to -0.5, and the b value is -6.0 to -2.5.

[0014] Furthermore, the CTE value of the first photosensitive layer is 50-70 ppm / °C, and the CTE value of the second photosensitive layer is 80-120 ppm / °C.

[0015] Another object of the present invention is to provide a method for preparing the above-mentioned photosensitive dry film laminate, comprising the steps of:

[0016] (1) providing a substrate layer, coating a first photosensitive resin composition on one side of the substrate layer, and then drying the substrate layer to form a first photosensitive layer;

[0017] (2) coating a second photosensitive resin composition on a side of the first photosensitive layer away from the substrate layer, and then drying the first photosensitive layer to form a second photosensitive layer; and obtaining the photosensitive dry film laminate.

[0018] Furthermore, the temperature for drying the first photosensitive resin composition is 65-85°C, and the time is 1-10 min; preferably, the solvent content of the first photosensitive layer after drying is 2wt%-5wt%; further, the temperature for drying the second photosensitive resin composition is 80-100°C, and the time is 10-20 min; preferably, the solvent content of the second photosensitive layer after drying is 0.1wt%-0.3wt%.

[0019] Another object of the present invention is to provide a circuit board, which includes an insulating base film layer, a metal foil layer and a photosensitive layer after the above-mentioned photosensitive dry film laminate is peeled off the substrate layer, or a photosensitive layer obtained after the photosensitive dry film laminate prepared according to the above-mentioned preparation method is peeled off the substrate layer.

[0020] The beneficial effects produced by the technical solution of the present invention include:

[0021] The present invention provides a photosensitive dry film laminate, a preparation method and a circuit board. Different from the single-layer photosensitive layer in the prior art, the photosensitive layer of the present invention includes a multi-layer structure, and photosensitive sublayers with exposure energy differences within a certain range and photosensitivity differences are superimposed, which improves the close fitting effect between the photosensitive layer and the circuit board while ensuring storage stability, and improves the resistance to nickel-gold solution by reducing the possibility of infiltration. DETAILED DESCRIPTION

[0022] 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 further described in detail below in conjunction with specific embodiments.

[0023] Unless otherwise defined, technical or scientific terms used in the disclosure of the present invention should have the common meanings that can be understood by those skilled in the art in the field to which the present invention belongs.

[0024] As analyzed in the background technology, the solder mask on the circuit board is very easy to turn white or even peel off after chemical nickel-gold deposition, which leads to short circuits and electrochemical corrosion between conductors due to moisture, chemicals, etc., and tinning during production and assembly, and loss of insulation and protection. Improving the resistance to chemical gold is to improve the chemical stability of the solder mask and prevent it from participating in chemical reactions, and to improve the closeness between the solder mask and the circuit board and prevent the infiltration of chemical gold solution on the other hand. In addition, the solder mask needs to have a certain storage stability during transportation and storage. The existing technology cannot take into account storage stability and chemical gold resistance while meeting the basic requirements of the industrialization process for simple process and low cost. To solve this problem, the present invention provides a photosensitive dry film laminate, a preparation method and a circuit board containing it.

[0025] In a typical embodiment of the present application, a photosensitive dry film laminate is provided, the photosensitive dry film laminate comprising a substrate layer and a photosensitive layer, the photosensitive layer comprising a first photosensitive layer and a second photosensitive layer, the first photosensitive layer and the second photosensitive layer are located on the same side of the substrate layer and the second photosensitive layer is arranged away from the substrate layer; the first photosensitive layer and the second photosensitive layer meet the following requirements: a first photosensitive layer of 30 cm×20 cm×10 um is arranged on a 30 cm×20 cm×15 um PET film to form a laminate 1, the laminate 1 is laminated to a 30 cm×20 cm copper clad laminate with the first photosensitive layer close to the copper surface of the copper clad laminate at 70°C and 4 kg pressure to form a sample 1, the sample 1 is placed on a stouffer The energy required when the exposure grid number of the 21-step exposure ruler is 7 is recorded as A; a second photosensitive layer of 30cm×20cm×10um is set on another 30cm×20cm×15um PET film to form a laminate 2, and the laminate 2 is laminated to a 30cm×20cm copper clad laminate with the second photosensitive layer close to the copper surface of the copper clad laminate at 70°C and a pressure of 4 kg to form a sample 2. The energy required when the exposure grid number of the stouffer 21-step exposure ruler is 7 is recorded as B; wherein, 50mJ≤AB≤700mJ, 50mJ≤A≤900mJ, and 50mJ≤B≤200mJ.

[0026] Furthermore, the photosensitive dry film laminate may further include a protective layer on a side of the photosensitive layer away from the substrate layer.

[0027] During the use of the photosensitive dry film laminate, it is necessary to first peel off the protective layer, then use a hot pressing roller or a vacuum laminator to bond the exposed side of the photosensitive layer to the circuit board, then expose the photosensitive layer from the substrate layer side, remove the substrate layer and immerse the remaining part in alkaline solution for development; or remove the substrate layer first and then perform exposure and development. The photosensitive layer is formed by stacking two photosensitive sublayers with different photosensitivity, and the photosensitive sublayer (second photosensitive layer) with better photosensitivity, that is, the photosensitive sublayer that meets the energy requirement of 50-200 mJ when the exposure grid number of sample 2 is 7 on the stouffer 21-step exposure scale, is located on the side far away from the substrate layer. When exposed, the photosensitive sublayer (second photosensitive layer) with better photosensitivity is farther away from the energy source, while the photosensitive sublayer with slightly worse photosensitivity is closer to the energy source, which makes up for the disadvantage of the photosensitive layer farther away from the energy source that receives less total energy to a certain extent, and the reaction degree of the light-induced cross-linking reaction is higher and the reaction is more complete, so the overall photosensitive layer has a better sealing effect with the circuit board, which can reduce or even avoid the infiltration of the chemical gold resistance solution, thereby improving the chemical gold resistance. At the same time, the photosensitivity of the photosensitive layer (first photosensitive layer) close to the substrate layer is slightly poor. The energy required for sample 1 when the exposure grid number is 7 on the stouffer 21-step exposure ruler is 50-900 mJ, which reduces the possibility of premature cross-linking reaction or even failure caused by light or heat during storage, and prevents the resolution from being affected during use. Therefore, the photosensitive dry film laminate of the present invention has better flatness and uniformity than solder mask ink, and can take into account the metal resistance, storage stability and better resolution.

[0028] In addition, the difference in energy required for Sample 1 and Sample 2 when the exposure grid number is 7 on the stouffer 21-step exposure scale is limited to a range of 50 to 700 mJ, that is, the difference in photosensitivity between the two is limited to a certain limit, which can prevent the following situations from occurring: (1) under the same energy source and the same exposure time, the second photosensitive layer has been fully exposed but the first photosensitive layer has not yet fully undergone a cross-linking reaction. If the exposure is stopped at this time, the surface hardness of the upper layer is insufficient, and the pattern part will also react with the developer and be removed during development; (2) under the same energy source and the same exposure time, in order to ensure that the first photosensitive layer is fully exposed, the time required for the entire photosensitive layer to be fully exposed is too long, affecting production efficiency; or the degree of cross-linking of the second photosensitive layer is too large, and the non-pattern part is difficult to remove, resulting in poor resolution.

[0029] Furthermore, the difference in energy required for the sample 1 and the sample 2 when the exposure number is 7 on the stouffer 21-step exposure scale is between 100 and 650 mJ, more preferably between 150 and 600 mJ, 200 and 550 mJ, and 250 and 500 mJ.

[0030] Furthermore, when the number of exposure grids of the stouffer 21-step exposure scale is 7, the energy A required for the sample 1 is between 200 and 850 mJ, more preferably between 250 and 800 mJ, 300 and 750 mJ, and 350 and 700 mJ. When the number of exposure grids of the stouffer 21-step exposure scale is 7, the energy B required for the sample 2 is between 50 and 180 mJ, more preferably between 55 and 170 mJ, 60 and 160 mJ, 65 and 150 mJ, and 25 and 140 mJ.

[0031] Furthermore, the photosensitive layer includes but is not limited to a first photosensitive layer and a second photosensitive layer. The photosensitive layer of the present invention may include two or more photosensitive sublayers, and the closer the photosensitive sublayer is to the substrate layer in the thickness direction of the photosensitive layer, the worse the photosensitivity of the photosensitive sublayer gradually becomes. Furthermore, the energy required for all samples made of the photosensitive sublayer when the exposure grid number of the stouffer 21-step exposure scale is 7 levels is between 50 and 800 mJ.

[0032] Furthermore, the difference in energy required for the samples made of adjacent photosensitive sublayers when the exposure grid number of the Stouffer 21-step exposure scale is 7 is between 50 and 500 mJ.

[0033] Furthermore, the thickness of the substrate layer is 15-40 microns, and the thickness of the photosensitive layer is 25-60 microns.

[0034] Furthermore, the thickness of the first photosensitive layer is 10-45 microns, and the thickness of the second photosensitive layer is 5-10 microns.

[0035] Furthermore, the thickness of the protective layer is 15 to 40 microns.

[0036] Furthermore, the substrate layer and the protective layer are respectively selected from one or more of PET film, PP film, PE film, and release paper.

[0037] Furthermore, the first photosensitive layer and the second photosensitive layer are formed by curing a first photosensitive resin composition and a second photosensitive resin composition, respectively, wherein the first photosensitive resin composition includes (A1) a main resin, (B1) an initiator, (C1) a curing agent, and (D1) a filler; the second photosensitive resin composition includes (A2) a main resin, (B2) an initiator, (C2) a curing agent, and (D2) a filler, and the mass ratio of the filler (D2) to the filler (D1) is 0 to 0.7.

[0038] Fillers can change the propagation direction of incident light. If the filler content of the second photosensitive layer is too much, it will affect the total amount of light received by the second photosensitive layer, and further affect the degree of cross-linking of the second photosensitive layer. Limiting the filler content of the second photosensitive layer to less than 70% of the first photosensitive layer can ensure the degree of light reaction of the second photosensitive layer while meeting the overall physical strength and appearance requirements of the photosensitive layer.

[0039] Furthermore, the mass ratio of the (D2) filler to the (D1) filler is 0.3 to 0.6.

[0040] Further, the filler includes a colored filler. Specifically, the filler is selected from organic or inorganic fillers, including but not limited to: red fillers, such as monoazo series, disazo series, azo lake series, benzimidazolone series, perylene series, diketopyrrolopyrrole series, condensed azo series, anthraquinone series, quinacridone series, etc.; blue fillers, such as phthalocyanine series, anthraquinone series, etc.; yellow fillers, such as monoazo series, disazo series, condensed azo series, benzimidazolone series, isoindoline series, anthraquinone series, etc.; black fillers, such as carbon black series, graphite series, iron oxide series, titanium black, iron oxide, anthraquinone series, cobalt oxide series, copper oxide series, manganese series, antimony oxide series, nickel oxide series, perylene series, aniline series, molybdenum sulfide, bismuth sulfide, etc.; white fillers, such as rutile or anatase titanium oxide, barium sulfate, etc.; orange, green, purple fillers, etc. can also be added as needed.

[0041] Furthermore, in order to improve the strength of the photosensitive layer, a system filler may be added, such as one or more of silicon dioxide, talcum powder, barium sulfate, calcium carbonate, and zinc oxide.

[0042] Furthermore, the main resin is an alkali-soluble resin, especially a carboxyl-containing resin. It can be selected from conventional alkali-soluble resins in the prior art, including acrylic resins and / or alkali-soluble polyimide resins. The acrylic resins include the following:

[0043] (1) A carboxylic acid-containing photosensitive resin obtained by adding an ethylenically unsaturated group as a side chain to a copolymer of an unsaturated carboxylic acid and a compound having an unsaturated double bond other than an epoxy group or (meth)acryloyl chloride;

[0044] (2) a photosensitive carboxylic acid-containing copolymer resin obtained by reacting a copolymer of a compound having an epoxy group and an unsaturated double bond and another compound having an unsaturated double bond with an unsaturated carboxylic acid, and reacting the generated secondary hydroxyl group with a polyacid anhydride;

[0045] (3) a carboxylic acid-containing photosensitive resin obtained by reacting a copolymer of an acid anhydride having an unsaturated double bond and a compound having an unsaturated double bond other than an acid anhydride with a compound having a hydroxyl group and an unsaturated double bond;

[0046] (4) a carboxylic acid-containing photosensitive resin obtained by reacting a polyfunctional epoxy compound with an unsaturated monocarboxylic acid and reacting the generated hydroxyl group with a saturated or unsaturated polyacid anhydride;

[0047] (5) A photosensitive resin containing a hydroxyl group and a carboxylic acid obtained by reacting a hydroxyl group-containing polymer with a saturated or unsaturated polyacid anhydride, and then reacting the resulting carboxylic acid with a compound having an epoxy group and an unsaturated double bond in one molecule;

[0048] (6) a carboxylic acid-containing photosensitive resin obtained by reacting a reaction product of a polyfunctional epoxy compound, an unsaturated monocarboxylic acid, and a compound having at least one alcoholic hydroxyl group and one reactive group other than the alcoholic hydroxyl group that reacts with an epoxy group in one molecule with a saturated or unsaturated polybasic acid anhydride;

[0049] (7) a carboxylic acid-containing photosensitive resin obtained by reacting a polyfunctional oxetane compound having at least two oxetane rings in one molecule with an unsaturated monocarboxylic acid, and reacting the primary hydroxyl group in the resulting modified oxetane resin with a saturated or unsaturated polybasic acid anhydride;

[0050] (8) A carboxylic acid-containing photosensitive resin obtained by reacting a polyfunctional epoxy resin with an unsaturated monocarboxylic acid, and then reacting the resin with a polyacid anhydride to obtain a carboxylic acid-containing resin, and then reacting the carboxylic acid-containing resin with a compound having one oxirane ring and one or more ethylenically unsaturated groups in the molecule.

[0051] Furthermore, the acid value of the main resin is 10 to 120 mgKOH / g. When the acid value is lower than 10 mgKOH / 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 120 mgKOH / g, the pattern is easily peeled off during the development process, resulting in development defects. Preferably, the acid value is 50 to 100 mgKOH / g.

[0052] Furthermore, the weight average molecular weight of the main resin is 2000 to 80000. When the weight average molecular weight is greater than 80000, the resolution of the photosensitive layer after exposure and development becomes poor; when the weight average molecular weight is less than 2000, 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 photosensitive layer and to improve the adhesion of the pattern obtained after development as much as possible, the weight average molecular weight is preferably 5000 to 35000.

[0053] The molar ratio of the initiator (B1) to the initiator (B2) is 0.3 to 2. The initiator content is an important factor affecting the photosensitivity of the photosensitive layer. Under the same other conditions, the higher the initiator content, the faster the photoreaction rate, and the higher the degree of curing reaction in the same time. If the initiator content of the second photosensitive layer is greater than or equal to the initiator content of the first photosensitive layer, the photosensitivity of the second photosensitive layer is better than that of the first photosensitive layer or is the same as that of the first photosensitive layer.

[0054] Further, the initiator is selected from conventional photopolymerization initiators and photosensitizers, such as ferrocene series, acetophenone series, oxime ester series, phosphine oxide series, anthrone series, benzoin ether, benzophenone series, anthraquinone series, thioxanthone compounds, hexaarylbisimidazole compounds, acridine compounds, etc., including but not limited to 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, 2-(acetoxyiminomethyl)thioxanthene-9-one, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetyl oxime), 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, One or more of 1-[4-(2-hydroxy)-phenyl]-3-hydroxy-2-methyl-1-propanone-1-one, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, 2-methyl-1-(4-methylthiophenyl)-2-morphinyl-1-propanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2,4-oxalic acid diethyl ester, 2,4-diethylthiazolone, 2-isopropylthioxanthone, 2-ethylanthraquinone, 2,4-diethylthioxanthone, and benzophenone.

[0055] Furthermore, the curing agent is selected from one or more of epoxy resins, isocyanates or isocyanurate compounds or triazine compounds; the epoxy resin is selected from bisphenol epoxy resins, biphenyl epoxy resins, novolac epoxy resins, epoxy resins containing naphthalene rings, and alicyclic epoxy resins; the bisphenol epoxy resin is selected from bisphenol A epoxy resins, bisphenol F epoxy resins, and bisphenol S epoxy resins; the novolac epoxy resin is selected from phenol novolac epoxy resins and novolac epoxy resins.

[0056] Furthermore, the epoxy equivalent of the epoxy resin is 50 to 350 g / eq., more preferably 50 to 300 g / eq., and even more preferably 100 to 200 g / eq. The epoxy equivalent of the epoxy resin is within a specific range, and from the viewpoint of cross-linking and densification, stress generated by heat during use can be reduced, thereby reducing the possibility of thermal cracking.

[0057] Furthermore, the softening point of the epoxy resin is 40 to 200° C., more preferably 50 to 100° C., where the softening point refers to a value measured according to the method described in JIS K 7234. Limiting the epoxy resin to the above range is conducive to further improving the heat resistance and crack resistance of the photosensitive layer, improving the compatibility and miscibility of the inorganic filler in the photosensitive resin composition system, and improving the bonding strength between the photosensitive layer and the circuit board.

[0058] Furthermore, the first photosensitive resin composition and the second photosensitive resin composition further include (E1) reactive monomers and (E2) reactive monomers, respectively, wherein the double bond equivalent in the (E1) reactive monomer is 100-600 g / mol, and the double bond equivalent in the (E2) reactive monomer is 100-600 g / mol. It is further preferred that the double bond equivalent in the (E1) reactive monomer is 200-500 g / mol, 300-400 g / mol, and the double bond equivalent in the (E2) reactive monomer is 200-500 g / mol, 300-400 g / mol. The main group participating in the photopolymerization reaction in the reactive monomer is the double bond. The more double bonds per unit mass, the higher the photoreaction efficiency, and the higher the degree of crosslinking and curing reaction at the same exposure time. However, too high a double bond content will affect the storage stability of the photosensitive dry film product. Furthermore, for the consideration of resistance to gold deposition, the double bond equivalent in the reactive monomer (E1) is recorded as M, and the double bond equivalent in the reactive monomer (E2) is recorded as N, -0.1≤(MN) / (M+N)≤0.1. Studies have found that limiting the double bond equivalents of the reactive monomers in the first and second photosensitive resin compositions to the above ratio range can ensure a better curing effect of the second photosensitive layer, thereby fully fitting with the circuit board and reducing the penetration of the gold deposition solution. It is further preferred that 0≤(MN) / (M+N)≤0.1.

[0059] Further, the reactive monomer can be selected from conventional photopolymerizable monomers, including but not limited to monofunctional (meth)acrylates, difunctional (meth)acrylates, trifunctional (meth)acrylates or multifunctional (meth)acrylates, specifically, (ethoxy)phenol (meth)acrylate, stearic acid acrylate, ethoxy (propoxy) nonylphenol (meth)acrylate, ethoxy (propoxy) tetrahydrofurfuryl (meth)acrylate, 1,6-hexanediol diacrylate, trifunctional (meth)acrylate or polyfunctional (meth)acrylate. Any one or more of cyclohexanedimethanol diacrylate, dioxanediol diacrylate, ethoxylated (propoxylated) bisphenol A di(meth)acrylate, polyethylene glycol (400) diacrylate, polypropylene glycol (600) diacrylate, ethoxylated (propoxylated) trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, dipentaerythritol hexaacrylate, ethoxylated pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

[0060] Furthermore, the (E2) reactive monomer is preferably a difunctional (meth)acrylate, a trifunctional (meth)acrylate or a multifunctional (meth)acrylate.

[0061] Furthermore, in terms of parts by mass, the first photosensitive resin composition comprises 100 parts by mass of a main resin (A1), 0 to 5 parts by mass of an initiator (B1), 5 to 20 parts by mass of a curing agent (C1), 5 to 20 parts by mass of a filler (D1), and 10 to 50 parts by mass of a reactive monomer (E1); and the second photosensitive resin composition comprises 100 parts by mass of a main resin (A2), 0 to 5 parts by mass of an initiator (B2), 5 to 20 parts by mass of a curing agent (C2), 0 to 5 parts by mass of a filler (D2), and 10 to 50 parts by mass of a reactive monomer (E2).

[0062] Furthermore, the L value of the first photosensitive layer is 92 to 99, the a value is -2 to 2, and the b value is -2 to 5. The L value of the second photosensitive layer is 70 to 100, the a value is -2.5 to -0.5, and the b value is -6.0 to -2.5. Setting the color value range of the first photosensitive layer and the second photosensitive layer can not only ensure that the overall appearance of the photosensitive layer presents the required color without causing overall inhomogeneity due to the different colors of the two photosensitive layers, but also ensure the light reflectivity of the photosensitive layer and improve the light utilization rate of the light-emitting device.

[0063] Furthermore, the CTE value of the first photosensitive layer is 50-70 ppm / °C, and the CTE value of the second photosensitive layer is 80-120 ppm / °C. The CTE values ​​of the first photosensitive layer and the second photosensitive layer are limited to a certain limit and the difference is small to prevent delamination or peeling from the circuit board due to heat and size changes during use.

[0064] In another typical embodiment of the present application, a method for preparing the above-mentioned photosensitive dry film laminate is provided, comprising the steps of:

[0065] (1) providing a substrate layer, coating a first photosensitive resin composition on one side of the substrate layer, and then drying the substrate layer to form a first photosensitive layer;

[0066] (2) coating a second photosensitive resin composition on a side of the first photosensitive layer away from the substrate layer, and then drying the first photosensitive layer to form a second photosensitive layer; and obtaining the photosensitive dry film laminate.

[0067] Furthermore, the temperature of the drying treatment of the first photosensitive resin composition is 65-85°C, and the time is 1-10 minutes; preferably, the solvent content of the first photosensitive layer after the drying treatment is 2wt%-5wt%; preferably, the temperature of the drying treatment of the second photosensitive resin composition is 80-100°C, and the time is 10-20 minutes; preferably, the solvent content of the second photosensitive layer after the drying treatment is 0.1wt%-0.3wt%. The second photosensitive layer is dried and the first photosensitive layer is dried again, that is, the first photosensitive layer is dried twice, so that the solvent content of the first photosensitive layer after the first drying treatment is controlled to be relatively large, which can form a film and satisfy that the solvent content is still kept within a certain limit after the second drying.

[0068] Furthermore, the preparation method further comprises the step (3) of laminating a protective film on the second photosensitive layer to obtain the photosensitive dry film laminate.

[0069] In another typical embodiment of the present application, a circuit board is provided, which includes an insulating base film layer, a metal foil layer, and a photosensitive layer after the above-mentioned photosensitive dry film laminate is peeled off the substrate layer, or a photosensitive layer obtained after the substrate layer is peeled off from the photosensitive dry film laminate prepared according to the above-mentioned preparation method.

[0070] Furthermore, the photosensitive resin composition further comprises other additives (F). The additives (F) are any one or more of a developer, a plasticizer, a defoamer, an inhibitor, and an antioxidant.

[0071] Furthermore, the developer is selected from any one or more of amyl bromide, ethylene dibromide, benzyl bromide, dibromomethane, tribromomethylphenyl sulfone, trichloroacetamide, amyl iodide, and dichloroethane.

[0072] Furthermore, 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, and p-toluenesulfonamide.

[0073] Furthermore, the defoamer is selected from one or more of a non-silicon defoamer, a polyether defoamer, a silicone defoamer, and a polyether-modified silicone defoamer.

[0074] Furthermore, the polymerization inhibitor is selected from any one or more of p-methoxyphenol, hydroquinone, pyrogallol, tert-butylcatechol, and N-nitrosophenylhydroxylamine aluminum salt.

[0075] Furthermore, the antioxidant is selected from any one or more of amine antioxidants, phenolic antioxidants, thioester auxiliary antioxidants, phosphite auxiliary antioxidants, and thioether auxiliary antioxidants.

[0076] The beneficial effects of the present application will be further illustrated below in combination with embodiments and comparative examples.

[0077] 1. Prepare the photosensitive resin composition

[0078] According to Table 1, the first photosensitive resin composition and the second photosensitive resin composition were prepared.

[0079] Table 1: Photosensitive resin composition ratio table (by mass fraction)

[0080]

[0081]

[0082] illustrate:

[0083] A-1: acid-modified epoxy acrylate resin (Nippon Kayaku ZFR-1401H, bisphenol F type, solid content 60%, acid value 98 mgKOH / g);

[0084] A-2: acrylate resin (Daichol CYCLOMER P (ACA) Z250, solid content 45%, acid value 70 mgKOH / g); B-1: 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-diimidazole (Changzhou Qiangli Electronics);

[0085] B-2: 9-phenylacridine (Shanghai TCI Chemical Co., Ltd.);

[0086] C-1: cresol novolac type epoxy resin (DIC EPICLON N-660, epoxy equivalent 202-212 g / eq);

[0087] C-2: bisphenol A type epoxy resin (Japanese epoxy resin jER828, epoxy equivalent 184-194g / eq);

[0088] D-1: Chloro-process rutile titanium oxide (DuPont R931);

[0089] D-2: rutile titanium oxide produced by the sulfuric acid method (Sakai Chemical R-7E);

[0090] D-3: Barium sulfate (Sakai Chemical BARIACE B-30);

[0091] E-1: stearic acid acrylate (Osaka Organic Chemical, double bond equivalent is 325 g / mol);

[0092] E-2: ethoxy nonylphenol acrylate (Kedi Chemical LM158, double bond equivalent 450g / mol);

[0093] E-3: poly(propylene glycol) diacrylate (McLean, double bond equivalent weight 527 g / mol);

[0094] E-4: propoxylated triethylolpropane tri(propyl)acrylate (Sartomer, double bond equivalent 213 g / mol); G: dipropylene glycol methyl ether (Dow Chemical).

[0095] 2. Preparation of photosensitive dry film laminate

[0096] On the production line, the first photosensitive resin composition glue is evenly coated on the substrate layer PET (15 μm thick), and dried through a channel at a temperature of 80°C to form a first photosensitive layer; then the second photosensitive resin composition glue is coated on the side of the first photosensitive layer away from the substrate layer, and dried through a channel at a temperature of 90°C to form a second photosensitive layer. A PE film (20 μm) is attached as a protective layer on the side of the photosensitive layer away from the substrate layer to form a photosensitive dry film laminate.

[0097] Table 2: Examples and Comparative Examples

[0098]

[0099]

[0100]

[0101] Hereinafter, the sample preparation method (including film lamination, exposure, and development) and the sample evaluation method and evaluation results of the examples and comparative examples will be described.

[0102]

Film

[0103] 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, the conveying speed was 1.5m / min, and the heat lamination was performed under standard pressure.

[0104]

exposure

[0105] The exposure was performed using a ZS Technology M-522 exposure machine, and the photosensitivity test was performed using a stouffer 21-step exposure ruler.

[0106]

development

[0107] The line width / line spacing of the film selected for development gradually increased from 10μm to 100μm; the developer was a 1%wt sodium carbonate aqueous solution, the development temperature was 30°C, the development pressure was 1.8bar, the development speed was 1.5m / min, and the developer model was Yuansu Technology XY-430. The minimum time required for the photosensitive layer of the unexposed part to be completely dissolved was taken as the minimum development time.

[0108]

CTE value evaluation

[0109] The first photosensitive layer adhesive and the second photosensitive layer adhesive were coated on the substrate layer respectively and dried in a hot air circulation drying furnace at 80°C for 10 minutes, cut into 3mm×10mm strips, and the substrate layer was peeled off; under a Hitachi TMA7100 thermal mechanical analyzer, the temperature was increased from room temperature at a rate of 10°C / min, and the strip size change curve was measured with the temperature to obtain the CTE value.

[0110]

Color value evaluation

[0111] The first photosensitive layer adhesive and the second photosensitive layer adhesive were coated on the substrate layer respectively and dried in a hot air circulation drying oven at 80°C for 10 minutes. A Konica Minolta CM-2600d spectrocolorimeter was used, and the color system used was CIEL*a*b*.

[0112]

Evaluation of solvent content

[0113] A photosensitive dry film laminate is prepared according to the above-mentioned coating and drying methods, and the total mass is measured before and after the first drying treatment and before and after the second drying treatment. The difference each time, that is, the mass of the reduced solvent, is calculated. Solvent content = (mass of the initially added solvent - mass of the reduced solvent) × 100% / (mass of the photosensitive layer glue - mass of the reduced solvent).

[0114] [Analytical evaluation]

[0115] The photosensitive layer is laminated on the copper-clad laminate using a heated pressure roller. Here, exposure is performed using a mask with a wiring pattern having a width of 1:1 (10-100 μm) between the exposed and unexposed parts. After development for 1.5 times the development removal time, the pattern is observed using a magnifying glass. The resolution is evaluated by the minimum value of the line width that can completely remove the unexposed part and remain without distortion or defects in the line. The smaller the value, the better the resolution.

[0116]

Evaluation of chemical resistance

[0117] Take a photosensitive dry film laminate and a copper clad laminate with a size of 10 cm×10 cm respectively, and place the second photosensitive layer of the laminate facing the copper surface of the copper clad laminate, and laminate it with the copper clad laminate at 70°C and 4 kg pressure, and perform exposure, development and heat curing, and remove the substrate layer to form a test sample; immerse the test sample in a gold solution at a temperature of 85°C for 30 seconds, and use a grid knife to scratch the surface of the first photosensitive layer of the test sample to form 10×10 square grids with a size of 1 mm×1 mm, and the copper surface is completely exposed in the grid gaps, and the debris in the grid area is removed with a brush; 3M No. 600 tape is pasted to the grid area and pressed to remove bubbles between the tape and the grid; the tape and the test sample are pulled off basically vertically, and the number of squares n that are peeled off is recorded.

[0118]

Glue overflow rate evaluation

[0119] Cut several square PET films of about 10cm×10cm for use, and cut the photosensitive dry film laminate to be tested into 2.54cm×2.54cm (1inch×1inch) squares. Tear off the PE film (protective layer) of the cut photosensitive dry film laminate, and stick the exposed photosensitive layer tightly to the central part of the inner side of the cut PET film (keep the four sides of the photosensitive layer parallel to the four sides of the PET), and cover the substrate layer of the photosensitive dry film laminate with another PET film. Use a flat vulcanizer, set the lamination temperature to 40℃ and the pressure to 10MPa, and after the temperature stabilizes for 1h, place the sample in the middle of the laminating board for lamination, and the lamination time is 5min. Observe the overflow width of the sample on each side under the 2D optical image measuring instrument, and measure the overflow width of each side and the actual width of the sample. The overflow width of each side is divided by the actual width of the photosensitive dry film laminate before lamination, which is the glue overflow rate of the side. The average value of each side is calculated, and the average value of 3 samples is taken as the glue overflow rate of the sample (the reading needs to be observed within 1 hour after the sample is pressed out by the press). The smaller the glue overflow rate value, the less likely it is to overflow.

[0120]

Storage stability evaluation

[0121] The photosensitive dry film laminate was placed in a constant temperature and humidity aging box at room temperature (5-25°C) and 50°C, respectively. The relative humidity of both boxes was controlled between 40% and 70%. After a period of time, the glue overflow on the side of the photosensitive dry film laminate was observed.

[0122] When stored at room temperature:

[0123] 1: No glue flow after 6 months of placement;

[0124] 2: Slight glue flow occurs after 6 months of storage;

[0125] 3: Slight glue flow occurs after 3 months of storage;

[0126] 4: Severe glue flow occurs after 3 months of placement;

[0127] When stored at 50°C:

[0128] 1: No glue flow after 1 month of placement;

[0129] 2: Slight glue flow occurs after 1 month of storage;

[0130] 3: Slight glue flow occurs after 2 weeks of storage;

[0131] 4: Severe glue flow occurs after 2 weeks of placement;

[0132]

Evaluation results

[0133] The evaluation results of the embodiments and comparative examples are shown in Table 3. All data were measured under the condition of 7 exposure frames.

[0134] Table 3: Evaluation results of examples and comparative examples

[0135]

[0136] As shown in Table 3, the comprehensive performance of Examples 1-10 in storage stability and chemical resistance is better than that of Comparative Examples 1-5, and the resolvability is good and the overflow phenomenon is significantly suppressed. The present invention uses a double-layer or multi-layer photosensitive sublayer to stack to form a photosensitive layer, and limits the curing difference between the layers, which can improve the closeness between the photosensitive layer and the circuit board and thus improve the chemical resistance. At the same time, the storage stability is good and the resolvability is good. Specifically, in Examples 7-9, the second photosensitive layer formula is the same and the first photosensitive layer formula is different. Since Example 8 has more fillers in the first photosensitive layer, which affects the second photosensitive layer from receiving light energy, its chemical resistance is slightly poor. In Examples 3-6, the first photosensitive layer formula is the same and the second photosensitive layer formula is different. In Example 5, the second photosensitive layer has too little initiator content and a large amount of monomer addition, and its storage stability and resolvability are poor.

[0137] In summary, the photosensitive dry film laminate using the solution of the present invention is beneficial for improving the chemical resistance of gold and has good industrial applicability.

[0138] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A photosensitive dry film laminate, characterized in that: The photosensitive dry film laminate comprises a substrate layer and a photosensitive layer, wherein the photosensitive layer comprises a first photosensitive layer and a second photosensitive layer, wherein the first photosensitive layer and the second photosensitive layer are located on the same side of the substrate layer and the second photosensitive layer is arranged away from the substrate layer; the first photosensitive layer and the second photosensitive layer satisfy: a first photosensitive layer of 30 cm×20 cm×10 um is arranged on a 30 cm×20 cm×15 um PET film to form a laminate 1, the laminate 1 is laminated to a 30 cm×20 cm copper clad laminate with the first photosensitive layer close to the copper surface of the copper clad laminate at 70° C. and a pressure of 4 kg to form a sample 1, and the sample 1 is placed on a stouffer The energy required when the exposure grid number of the 21-step exposure ruler is 7 is recorded as A; a second photosensitive layer of 30cm×20cm×10um is set on another 30cm×20cm×15um PET film to form a laminate 2, and the laminate 2 is laminated to a 30cm×20cm copper clad laminate with the second photosensitive layer close to the copper surface of the copper clad laminate at 70°C and a pressure of 4 kg to form a sample 2. The energy required when the exposure grid number of the stouffer 21-step exposure ruler is 7 is recorded as B; wherein, 50mJ≤AB≤700mJ, 50mJ≤A≤900mJ, and 50mJ≤B≤200mJ.

2. A photosensitive dry film laminate according to claim 1, characterized in that: The first photosensitive layer and the second photosensitive layer are formed by curing a first photosensitive resin composition and a second photosensitive resin composition, respectively. The first photosensitive layer is formed by the first photosensitive resin composition, and the second photosensitive layer is formed by the second photosensitive resin composition. The first photosensitive resin composition includes (A1) a main resin, (B1) an initiator, (C1) a curing agent, and (D1) a filler. The second photosensitive resin composition includes (A2) a main resin, (B2) an initiator, (C2) a curing agent, and (D2) a filler. The mass ratio of the filler (D2) to the filler (D1) is 0 to 0.

7. The (A1) main resin and the (A2) main resin are alkali-soluble resins; The initiator (B1) and the initiator (B2) are selected from photopolymerization initiators and photosensitizers, and the photopolymerization initiators and photosensitizers include one or more of ferrocene-based compounds, acetophenone-based compounds, oxime ester-based compounds, phosphine oxide-based compounds, anthrone-based compounds, benzoin ethers, benzophenone-based compounds, anthraquinone-based compounds, thioxanthone compounds, hexaarylbisimidazole-based compounds, and acridine-based compounds; The (C1) curing agent and the (C2) curing agent include one or more of epoxy resin, isocyanate or isocyanurate compound or triazine compound; The (D1) filler and (D2) filler include colored fillers.

3. A photosensitive dry film laminate according to claim 2, characterized in that: The first photosensitive resin composition and the second photosensitive resin composition further include (E1) reactive monomers and (E2) reactive monomers, respectively, wherein the double bond equivalent of the (E1) reactive monomers is 100 to 600 g / mol, and the double bond equivalent of the (E2) reactive monomers is 100 to 600 g / mol; the (E1) reactive monomers and (E2) reactive monomers include one or more of monofunctional (meth)acrylates, difunctional (meth)acrylates, trifunctional (meth)acrylates or multifunctional (meth)acrylates.

4. A photosensitive dry film laminate according to claim 3, characterized in that: The double bond equivalent in the reactive monomer (E1) is denoted as M, and the double bond equivalent in the reactive monomer (E2) is denoted as N, wherein -0.1≤(MN) / (M+N)≤0.

1.

5. A photosensitive dry film laminate according to any one of claims 2 to 4, characterized in that: In terms of parts by mass, the first photosensitive resin composition comprises 100 parts by mass of a main resin (A1), 0-5 parts by mass of an initiator (B1), 5-20 parts by mass of a curing agent (C1), 5-20 parts by mass of a filler (D1), and 10-50 parts by mass of a reactive monomer (E1); and the second photosensitive resin composition comprises 100 parts by mass of a main resin (A2), 0-5 parts by mass of an initiator (B2), 5-20 parts by mass of a curing agent (C2), 0-5 parts by mass of a filler (D2), and 10-50 parts by mass of a reactive monomer (E2).

6. The photosensitive dry film laminate according to claim 1, characterized in that: The L value of the first photosensitive layer is 92 to 99, the a value is -2 to 2, and the b value is -2 to 5. The L value of the second photosensitive layer is 70 to 100, the a value is -2.5 to -0.5, and the b value is -6.0 to -2.

5.

7. The photosensitive dry film laminate according to claim 1, characterized in that: The CTE value of the first photosensitive layer is 50-70 ppm / ° C., and the CTE value of the second photosensitive layer is 80-120 ppm / ° C.

8. The method for preparing a photosensitive dry film laminate according to any one of claims 1 to 7, characterized in that: Includes steps: (1) providing a substrate layer, coating a first photosensitive resin composition on one side of the substrate layer, and then drying the substrate layer to form a first photosensitive layer; (2) coating a second photosensitive resin composition on a side of the first photosensitive layer away from the substrate layer, and then drying the layer to form a second photosensitive layer; and obtaining the photosensitive dry film laminate.

9. The method for preparing a photosensitive dry film laminate according to claim 8, characterized in that: The first photosensitive resin composition is dried at a temperature of 65 to 85° C. for 1 to 10 min; after drying, the solvent content of the first photosensitive layer is 2wt% to 5wt%; the second photosensitive resin composition is dried at a temperature of 80 to 100° C. for 10 to 20 min; after drying, the solvent content of the second photosensitive layer is 0.1wt% to 0.3wt%.

10. A circuit board, characterized in that: The circuit board comprises an insulating base film layer, a metal foil layer and the photosensitive layer according to any one of claims 1 to 7 or a photosensitive layer obtained by peeling off the base material layer from a photosensitive dry film laminate prepared by the preparation method according to any one of claims 8 to 9.

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