Curable resin composition, curable resin film, and printed wiring board

Abstract

A curable resin composition containing a curable resin, wherein the metal content is 200 mass ppm or less based on the total solid content of the curable resin composition.

Description

Curable resin composition, curable resin film, and printed circuit board

[0001] This disclosure relates to a curable resin composition, a curable resin film, and a printed circuit board.

[0002] In the field of printed circuit boards (PCBs), permanent resist is formed on the PCBs. Permanent resist plays a role in preventing corrosion of the conductor layer and maintaining electrical insulation between conductor layers during the use of the PCB. In recent years, permanent resist has also taken on the role of a solder resist film in processes such as flip-chip mounting and wire bonding mounting of semiconductor elements onto PCBs via solder, preventing solder from adhering to unwanted areas of the conductor layer on the PCB.

[0003] Conventionally, permanent resists have been produced by screen printing using a thermosetting resin composition or by photographic methods using a photosensitive resin composition. For example, in flexible wiring boards using mounting methods such as FC (Flip Chip), TAB (Tape Automated Bonding), and COF (Chip On Film), a thermosetting resin paste is screen printed and heat-cured to form a permanent resist, except for the wiring patterns that connect to IC chips, electronic components, or LCD (liquid crystal display) panels (see, for example, Patent Document 1).

[0004] In semiconductor package substrates such as BGA (Ball Grid Array) and CSP (Chip Size Package) mounted on electronic components, it is necessary to remove the permanent resist from the bonding area for the following reasons: (1) to flip-chip mounting of semiconductor elements on the semiconductor package substrate via solder, (2) to wire-bond the semiconductor elements to the semiconductor package substrate, and (3) to solder the semiconductor package substrate to the motherboard substrate. For image formation of the permanent resist, a photographic method is used in which a photosensitive resin composition is applied, dried, and then selectively irradiated with active light such as ultraviolet light to cure it, and only the unirradiated areas are removed by development to form the image. Because the photographic method is suitable for mass production due to its ease of work, it is widely used in the electronic materials industry for image formation of photosensitive materials (see, for example, Patent Document 2).

[0005] Japanese Patent Publication No. 2003-198105 Japanese Patent Publication No. 2011-133851

[0006] In recent years, with the improvement of semiconductor package performance, cooling technologies that dissipate the heat generated from semiconductor packages have attracted attention. Until now, air cooling using heat sinks was the mainstream method for cooling semiconductor packages, but a new technology called liquid immersion cooling, which cools semiconductor packages by directly immersing them in a coolant, has emerged and is becoming widespread. Currently, fluorocarbon inert solutions are widely used as coolants for liquid immersion cooling, but from an environmental perspective, a switch to synthetic oils is being considered. However, synthetic oils degrade more easily than fluorocarbon inert solutions, and there is a problem that discoloration of the synthetic oil is likely to occur when semiconductor packages mounted on printed circuit boards are immersed in synthetic oil.

[0007] This disclosure has been made in view of the problems of the above-mentioned prior art, and aims to provide a curable resin composition that can produce a cured product that does not easily cause discoloration of synthetic oil even when immersed in synthetic oil used for liquid immersion cooling, a curable resin film using the same, and a printed circuit board.

[0008] As a result of diligent research to solve the above problems, the inventors discovered that when a printed circuit board containing a cured product of a curable resin composition contains metal (mainly pigment), and the printed circuit board is immersed in synthetic oil together with a semiconductor package mounted on the printed circuit board, metal ions leach from the cured product, accelerating the degradation of the synthetic oil. The inventors then discovered that the degradation of the synthetic oil can be suppressed by reducing the metal content of the curable resin composition, and thus completed the present invention.

[0009] This disclosure provides the following curable resin compositions, curable resin films, and printed circuit boards.

[0010] [1] A curable resin composition containing a curable resin, wherein the metal content is 200 ppm by mass or less based on the total solid content of the curable resin composition. [2] The curable resin composition according to [1], further containing a pigment. [3] The curable resin composition according to [1] or [2], containing an acid-modified vinyl group-containing resin, a thermosetting resin, a photopolymerizable compound, a photopolymerization initiator, an inorganic filler, and a pigment. [4] The curable resin composition according to [2] or [3], wherein the pigment is an organic pigment. [5] The curable resin composition according to any one of [2] to [4], wherein the pigment is at least one selected from the group consisting of azo pigments, indanthrene pigments, and hydrogenated phthalocyanines. [6] A curable resin film comprising a support film and a curable resin layer formed on the support film, wherein the curable resin layer contains the curable resin composition according to any one of [1] to [5]. [7] A printed circuit board comprising a permanent resist containing a cured product of any of the curable resin compositions described in [1] to [5] above.

[0011] According to this disclosure, it is possible to provide a curable resin composition that can produce a cured product that does not easily cause discoloration of the synthetic oil even when immersed in the synthetic oil used for liquid immersion cooling, as well as a curable resin film and a printed circuit board using the same.

[0012] This is a schematic cross-sectional view showing a curable resin film according to this embodiment.

[0013] The present disclosure is described in detail below. In this specification, the term "process" includes not only independent processes but also processes that are indistinguishable from other processes as long as the intended function of the process is achieved. The term "layer" includes not only structures that are formed on the entire surface when viewed as a plan view, but also structures that are formed on only a part of the surface. Numerical ranges indicated using "~" indicate a range that includes the numbers written before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step may be replaced with the upper or lower limit of a numerical range in another step. In numerical ranges described in this specification, the upper or lower limit of a numerical range may be replaced with the values ​​shown in the examples.

[0014] In this specification, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple substances present in the composition.

[0015] In this specification, "(meth)acrylate" means at least one of "acrylate" and its corresponding "methacrylate," and the same applies to other similar expressions such as (meth)acrylic acid and (meth)acryloyl. In this specification, "solids" refers to the non-volatile components of a curable resin composition excluding volatile substances (water, solvents, etc.), and includes components that are liquid, syrup-like, or waxy at room temperature (around 25°C).

[0016] [Curable Resin Composition] The curable resin composition according to this embodiment is a curable resin composition containing a curable resin, wherein the metal content is 200 ppm by mass or less based on the total amount of solids in the curable resin composition. According to the curable resin composition according to this embodiment, by keeping the metal content within the above range, it is possible to obtain a cured product that does not easily cause discoloration of the synthetic oil even when immersed in the synthetic oil used for liquid immersion cooling.

[0017] The curable resin composition according to this embodiment may further contain a pigment. Further, the curable resin composition according to this embodiment may be a photosensitive resin composition containing an acid-modified vinyl group-containing resin (hereinafter sometimes referred to as "(A) component") as the above-mentioned curable resin, a thermosetting resin (hereinafter sometimes referred to as "(B) component") as the above-mentioned curable resin, a photopolymerizable compound (hereinafter sometimes referred to as "(C) component"), a photopolymerization initiator (hereinafter sometimes referred to as "(D) component"), an inorganic filler (hereinafter sometimes referred to as "(E) component"), and a pigment (hereinafter sometimes referred to as "(F) component"). The above photosensitive resin composition is a negative-type photosensitive resin composition.

[0018] Further, the curable resin composition according to this embodiment may be a thermosetting resin composition containing a thermosetting resin ((B) component) as the above-mentioned curable resin, an inorganic filler ((E) component), and the above pigment ((F) component).

[0019] The cured product (cured film) of the curable resin composition according to this embodiment can be suitably used as a permanent resist. Hereinafter, each component used in the curable resin composition of this embodiment will be described in more detail.

[0020] ((A) component: acid-modified vinyl group-containing resin) The curable resin composition according to this embodiment may contain an acid-modified vinyl group-containing resin as the (A) component. The acid-modified vinyl group-containing resin is not particularly limited as long as it has a vinyl bond which is a photopolymerizable ethylenically unsaturated bond and an alkali-soluble acidic group.

[0021] Examples of the group having an ethylenically unsaturated bond possessed by the (A) component include a vinyl group, an allyl group, a propargyl group, a butenyl group, an ethynyl group, a phenylethynyl group, a maleimide group, a nadimide group, and a (meth)acryloyl group. Among these, from the viewpoints of reactivity and resolution, the (meth)acryloyl group is preferable. Examples of the acidic group possessed by the (A) component include a carboxy group, a sulfo group, and a phenolic hydroxyl group. Among these, from the viewpoint of resolution, the carboxy group is preferable.

[0022] Examples of component (A) include (A1) an acid-modified vinyl group-containing epoxy derivative (hereinafter sometimes referred to as "component (A1)") and (A2) an acid-modified vinyl group-containing phenol derivative (hereinafter sometimes referred to as "component (A2)"), etc. These may be oligomers or polymers. Component (A1): An acid-modified vinyl group-containing epoxy derivative obtained by reacting a resin (A1') obtained by reacting (a1) an epoxy resin (hereinafter sometimes referred to as "component (a1)") with (b1) an ethylenically unsaturated group-containing organic acid (hereinafter sometimes referred to as "component (b1)") with (c1) a saturated or unsaturated group-containing polybasic acid anhydride (hereinafter sometimes referred to as "component (c1)"). (A2) Component: A resin (A2') obtained by reacting (a2) a compound having two or more phenolic hydroxyl groups in one molecule (hereinafter sometimes referred to as "component (a2)") with (d2) an alkylene oxide (hereinafter sometimes referred to as "component (d2)"), and then reacting the resulting resin (A2'') with (c2) a polybasic acid anhydride containing a saturated or unsaturated group (hereinafter sometimes referred to as "component (c2)") to obtain an acid-modified vinyl group-containing phenol derivative.

[0023] ((A1) Acid-modified vinyl group-containing epoxy derivative) (A1) An example of an acid-modified vinyl group-containing epoxy derivative is acid-modified epoxy (meth)acrylate. Acid-modified epoxy (meth)acrylate is a resin obtained by acid-modifying epoxy (meth)acrylate, which is a reaction product of component (a1) and component (b1), with component (c1). As acid-modified epoxy (meth)acrylate, for example, an addition product obtained by adding a saturated or unsaturated polybasic acid anhydride to an esterified product obtained by reacting an epoxy resin with a vinyl group-containing monocarboxylic acid can be used.

[0024] ((a1) epoxy resin) As the component (a1), for example, bisphenol novolak type epoxy resin, novolak type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, triphenol methane type epoxy resin, and biphenyl type epoxy resin can be mentioned. From the viewpoint of excellent resolution and heat shock resistance, the component (a1) may contain bisphenol novolak type epoxy resin and novolak type epoxy resin.

[0025] As the bisphenol novolak type epoxy resin, for example, epoxy resins having structural units represented by the following formula (I) or (II) can be mentioned.

[0026]

[0027] In formula (I), R １１ represents a hydrogen atom or a methyl group, and a plurality of R １１ may be the same or different. Y １ and Y ２ each independently represent a hydrogen atom or a glycidyl group, but at least one of Y １ and Y ２ is a glycidyl group. From the viewpoint of suppressing the generation of undercuts and improving the linearity and resolution of the resist pattern profile, R １１ is preferably a hydrogen atom, and from the viewpoint of further improving heat shock resistance, Y １ and Y ２ are preferably glycidyl groups.

[0028] The number of structural units represented by formula (I) in the bisphenol novolak type epoxy resin (hereinafter, also referred to as "the number of structural units") is 1 or more, and may be 10 to 100, 15 to 80, or 15 to 70. When the number of structural units is within the above range, it becomes easier to improve the linearity of the resist pattern profile, the adhesion to the copper substrate, heat resistance, and electrical insulation. Here, the number of structural units indicates an integer value in a single molecule and a rational number that is an average value in an aggregate of multiple types of molecules. The same applies to the number of structural units hereinafter.

[0029]

[0030] In formula (II), R １２ R represents a hydrogen atom or a methyl group, and there are multiple R １２ They may be the same or different. Y ３ and Y ４ Each of these independently represents a hydrogen atom or a glycidyl group, but Y ３ and Y ４ At least one of them is a glycidyl group. From the viewpoint of suppressing the occurrence of undercuts and improving the linearity and resolution of the resist pattern contour, R １２ It is preferably a hydrogen atom, and from the viewpoint of further improving thermal shock resistance, Y ３ and Y ４ It is preferable that it is a glycidyl group.

[0031] The number of structural units represented by formula (II) in the bisphenol novolac type epoxy resin is 1 or more, and may be 10 to 100, 15 to 80, or 15 to 70. When the number of structural units is within the above range, it becomes easier to improve the linearity of the resist pattern contour, adhesion to the copper substrate, and heat resistance.

[0032] In equation (II), R １２ Y is a hydrogen atom, ３ and Y ４ Epoxy resins in which the group is a glycidyl group are sold as the EXA-7376 series (manufactured by DIC Corporation, product name), and also as R １２ The group is a methyl group, Y ３ and Y ４ Epoxy resins with a glycidyl group are commercially available as the EPON SU8 series (manufactured by Westlake, trade name).

[0033] As a novolac-type epoxy resin, for example, a novolac-type epoxy resin having a structural unit represented by the following formula (III) is preferred. Examples of novolac-type epoxy resins having such a structural unit include a novolac-type epoxy resin represented by the following formula (III').

[0034]

[0035] In equations (III) and (III'), R １３ Y represents a hydrogen atom or a methyl group.５ Y represents a hydrogen atom or a glycidyl group, ５ At least one of them is a glycidyl group. In formula (III'), n １ is a number greater than or equal to 1, and there are multiple R １３ and Y ５ These may be the same or different. From the viewpoint of suppressing the occurrence of undercuts and improving the linearity and resolution of the resist pattern contour, R １３ It is preferable that it be a hydrogen atom.

[0036] In formula (III'), Y is a hydrogen atom. ５ and the glycidyl group Y ５ The molar ratio may be 0 / 100 to 30 / 70 or 0 / 100 to 10 / 90, from the viewpoint of suppressing the occurrence of undercuts and improving the linearity and resolution of the resist pattern contour. １ n is 1 or greater, but may be 10-200, 30-150, or 30-100. １ When the values ​​are within the above range, the linearity of the resist pattern contour, adhesion to the copper substrate, and heat resistance tend to improve.

[0037] Examples of novolac-type epoxy resins represented by formula (III') include phenol novolac-type epoxy resins and cresol novolac-type epoxy resins. These novolac-type epoxy resins can be obtained, for example, by reacting a phenol novolac resin or a cresol novolac resin with epichlorohydrin using a known method.

[0038] Examples of commercially available phenol novolac type epoxy resins or cresol novolac type epoxy resins represented by formula (III') include YDCN-700-7, YDCN-700-10, YDCN-704, YDCN-704A, YDPN-638 (all manufactured by Nippon Steel Chemical & Material Co., Ltd., trade names), EOCN-102S, EOCN-103S, EOCN-104S, EOCN-1012, EOCN-1027, BREN-S (all manufactured by Nippon Kayaku Co., Ltd., trade names), N-740, N-770, N-665, N-673 (all manufactured by DIC Corporation, trade names).

[0039] (b1) Organic acids containing ethylenically unsaturated groups. Examples of component (b1) include acrylic acid derivatives such as acrylic acid, acrylic acid dimers, methacrylic acid, β-furfurylacrylic acid, β-styrylacrylic acid, cinnamic acid, crotonic acid, and α-cyanocinnamic acid; semi-ester compounds which are reaction products of hydroxyl group-containing (meth)acrylates and dibasic acid anhydrides; and semi-ester compounds which are reaction products of vinyl group-containing monoglycidyl ethers or vinyl group-containing monoglycidyl esters and dibasic acid anhydrides. Component (b1) may be used individually or in combination of two or more.

[0040] Semi-ester compounds can be obtained, for example, by reacting a hydroxyl group-containing (meth)acrylate, a vinyl group-containing monoglycidyl ether, or a vinyl group-containing monoglycidyl ester with a dibasic acid anhydride.

[0041] Examples of hydroxyl group-containing (meth)acrylates, vinyl group-containing monoglycidyl ethers, and vinyl group-containing monoglycidyl esters include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, trimethylolpropanedi(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and glycidyl (meth)acrylate.

[0042] Examples of dibasic acid anhydrides include succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, methyltetrahydrophthalic anhydride, ethyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, ethylhexahydrophthalic anhydride, and itaconic anhydride.

[0043] In the reaction between component (a1) and component (b1), it is preferable to react them in a ratio of 0.6 to 1.05 equivalents of component (b1) per equivalent of 1 equivalent of epoxy group of component (a1), and more preferably in a ratio of 0.8 to 1.0 equivalents. Reacting in such a ratio tends to increase photosensitivity and improve the linearity of the resist pattern contour.

[0044] A polymerization inhibitor may be used in the reaction between component (a1) and component (b1) to prevent polymerization during the reaction. Examples of polymerization inhibitors include hydroquinone, methylhydroquinone, hydroquinone monomethyl ether, catechol, and pyrogallol. A single polymerization inhibitor or a combination of two or more may be used.

[0045] From the viewpoint of improving stability, the amount of polymerization inhibitor used may be 0.01 to 1 part by mass, 0.02 to 0.8 parts by mass, or 0.04 to 0.5 parts by mass per 100 parts by mass of the total of components (a1) and (b1).

[0046] Component (A1'), obtained by reacting component (a1) and component (b1), has a hydroxyl group formed by a ring-opening addition reaction between the epoxy group of component (a1) and the carboxyl group of component (b1). By further reacting component (A1') with component (c1), an acid-modified vinyl group-containing resin is obtained in which the hydroxyl groups of component (A1') (including the hydroxyl groups originally present in component (a1)) and the acid anhydride group of component (c1) are semi-esterified.

[0047] (c1) Polybasic acid anhydride containing saturated or unsaturated groups. Examples of component (c1) include succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, methyltetrahydrophthalic anhydride, ethyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, ethylhexahydrophthalic anhydride, and itaconic anhydride. Among these, tetrahydrophthalic anhydride is preferred from the viewpoint of resolution. Component (c1) may be used alone or in combination of two or more.

[0048] In the reaction between component (A1') and component (c1), for example, the acid value of component (A1) can be adjusted by reacting 0.1 to 1.0 equivalents of component (c1) with 1 equivalent of hydroxyl group in component (A1').

[0049] If necessary, hydrogenated bisphenol A epoxy resin may be partially used as component (a1), and styrene-maleic acid resins such as hydroxyethyl (meth)acrylate modified styrene-maleic anhydride copolymers may also be partially used.

[0050] ((A2) Acid-modified vinyl group-containing phenol derivative) (A2) Acid-modified vinyl group-containing phenol derivative is a resin obtained by reacting (a2) a compound having two or more phenolic hydroxyl groups in one molecule with (d2) an alkylene oxide, and then reacting (b2) an organic acid containing an ethylenically unsaturated group with the hydroxyl group of the oxyalkyl group in the side chain of the resin (A2'), and then reacting the resulting resin (A2'') with (c2) a polybasic acid anhydride containing a saturated or unsaturated group.

[0051] (a2) Compounds having two or more phenolic hydroxyl groups in one molecule. Examples of component (a2) include condensates of phenols and ketones, condensates of phenols and aldehydes, condensates of phenols and aromatic aldehydes having phenolic hydroxyl groups, poly-p-hydroxystyrene, naphthol-type novolac resins, trisphenolmethane-type resins, etc. These may be used individually or in combination of two or more.

[0052] (d2) Alkylene oxides (d2) Examples of components include ethylene oxide, propylene oxide, trimethylene oxide, etc.

[0053] ((b2) Organic acid containing an ethylenically unsaturated group) The same compounds as those described above for component (b1) can be used for component (b2). Component (b2) can be used alone or in combination of two or more.

[0054] ((c2) Polybasic acid anhydride containing saturated or unsaturated groups) The (c2) component can be the same compound as the (c1) component described above. The (c2) component can be used alone or in combination of two or more types.

[0055] In the reaction between component (A2'') and component (c2), for example, the acid value of component (A2) can be adjusted by reacting 0.1 to 1.0 equivalents of component (c2) with 1 equivalent of hydroxyl group in component (A2'').

[0056] Component (A) preferably contains component (A1) from the viewpoint of suppressing the occurrence of undercuts and further improving adhesion to the copper substrate, thermal shock resistance, and resolution. Component (A) may also contain component (A2), or an acid-modified vinyl group-containing resin other than components (A1) and (A2), from the viewpoint of improving adhesion strength.

[0057] (A) The acid value of component (A) is not particularly limited. From the viewpoint of improving the solubility of the unexposed portion in the alkaline aqueous solution, the acid value of component (A) may be 30 mg KOH / g or more, 40 mg KOH / g or more, or 50 mg KOH / g or more. From the viewpoint of improving the electrical properties of the cured film, the acid value of component (A) may be 150 mg KOH / g or less, 120 mg KOH / g or less, or 100 mg KOH / g or less.

[0058] The weight-average molecular weight (Mw) of component (A) varies depending on the resin skeleton, but is not particularly limited. From the viewpoint of improving the adhesion of the cured film, the Mw of component (A) may be 3000 or more, 4000 or more, or 5000 or more. From the viewpoint of improving the resolution of the curable resin layer, the Mw of component (A) may be 30000 or less, 25000 or less, or 18000 or less.

[0059] Mw can be measured by gel permeation chromatography (GPC). For example, Mw can be measured under the GPC conditions described below, and the value converted using a calibration curve for standard polystyrene can be used as the Mw value. A set of five samples ("PStQuick MP-H" and "PStQuick B," manufactured by Tosoh Corporation) can be used as the standard polystyrene to create the calibration curve. GPC instrument: High-speed GPC instrument "HCL-8320GPC" (manufactured by Tosoh Corporation) Detector: Differential refractometer or UV detector (manufactured by Tosoh Corporation) Column: TSKgel SuperMultipore HZ-H column (column length: 15 cm, column inner diameter: 4.6 mm) (manufactured by Tosoh Corporation) Eluent: Tetrahydrofuran (THF) Measurement temperature: 40°C Flow rate: 0.35 mL / min Sample concentration: 10 mg / THF 5 mL Injection volume: 20 μL

[0060] The content of component (A) in the curable resin composition may be 20 to 70% by mass, 25 to 60% by mass, or 30 to 50% by mass, based on the total solid content of the curable resin composition, from the viewpoint of improving the heat resistance, electrical properties, and chemical resistance of the permanent resist.

[0061] (Component (B): Thermosetting resin) The curable resin composition according to this embodiment may contain a thermosetting resin as component (B). By using component (B), the heat resistance, adhesion, and chemical resistance of the cured film (permanent resist) formed from the curable resin composition can be improved. Component (B) may be used alone or in combination of two or more types.

[0062] Examples of component (B) include epoxy resins, phenolic resins, unsaturated imide resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins.

[0063] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, hydantoin type epoxy resin, triglycidyl isocyanurate, and bixylenol type epoxy resin.

[0064] The content of component (B) may be 2 to 30% by mass, 5 to 25% by mass, or 8 to 20% by mass, based on the total solid content of the curable resin composition. When the content of component (B) is within the above range, the heat resistance of the formed cured film can be further improved while maintaining good developability.

[0065] (Component (C): Photopolymerizable compound) Component (C) is not particularly limited as long as it is a compound having a functional group that exhibits photopolymerization. Component (C) may be a photopolymerizable compound having an ethylenically unsaturated group that does not have an acidic group. Component (C) preferably comprises at least one selected from the group consisting of (Ci) a monofunctional vinyl monomer having one polymerizable ethylenically unsaturated group, (Cii) a difunctional vinyl monomer having two polymerizable ethylenically unsaturated groups, and (Ciii) a polyfunctional vinyl monomer having at least three polymerizable ethylenically unsaturated groups, and more preferably comprises at least the above-mentioned (Ciii) component. Components (Ci) to (Ciii) are preferably those with a molecular weight of 1000 or less.

[0066] ((Ci) Monofunctional vinyl monomer) Examples of the monofunctional vinyl monomer having one polymerizable ethylenically unsaturated group include (meth)acrylic acid and alkyl (meth)acrylate. Examples of alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and hydroxyethyl (meth)acrylate. The (Ci) component may be used alone or in combination of two or more.

[0067] ((Cii) Difunctional vinyl monomer) Examples of the above two polymerizable ethylenically unsaturated difunctional vinyl monomers include polyethylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2,2-bis(4-(meth)acryloxypolyethoxypolypropoxyphenyl)propane, bisphenol A diglycidyl ether di(meth)acrylate, etc. The (Cii) component may be used alone or in combination of two or more.

[0068] ((Ciii) polyfunctional vinyl monomer) Examples of polyfunctional vinyl monomers having at least three polymerizable ethylenically unsaturated groups include (meth)acrylate compounds having a trimethylolpropane-derived skeleton such as trimethylolpropane tri(meth)acrylate; (meth)acrylate compounds having a tetramethylolmethane-derived skeleton such as tetramethylolmethane tri(meth)acrylate and tetramethylolmethane tetra(meth)acrylate; (meth)acrylate compounds having a pentaerythritol-derived skeleton such as pentaerythritol tri(meth)acrylate and pentaerythritol tetra(meth)acrylate; (meth)acrylate compounds having a dipentaerythritol-derived skeleton such as dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate; (meth)acrylate compounds having a ditrimethylolpropane-derived skeleton such as ditrimethylolpropane tetra(meth)acrylate; and (meth)acrylate compounds having a diglycerin-derived skeleton. Among these, (meth)acrylate compounds having a dipentaerythritol-derived skeleton are preferred, and dipentaerythritol hexa(meth)acrylate is more preferred, from the viewpoint of improving chemical resistance after curing (exposure) and increasing the difference in developer resistance between the exposed and unexposed areas. Component (Ciii) may be used alone or in combination of two or more.

[0069] The content of component (C) in the curable resin composition is not particularly limited, but may be 0.2 to 15% by mass, 0.5 to 10% by mass, or 1 to 10% by mass, based on the total solid content of the curable resin composition.

[0070] (Component (D): Photopolymerization initiator) The photopolymerization initiator, which is component (D), is not particularly limited as long as it can polymerize components (A) and (C). Component (D) may be used alone or in combination of two or more types.

[0071] (D) Component includes, for example, acetophenone compounds such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, N,N-dimethylaminoacetophenone; anthraquinone compounds such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, 2-aminoanthraquinone; benzophenone, methylbenzophenone, 4,4'-dichloroben Examples include benzophenone compounds such as zophenone, 4,4'-bis(diethylamino)benzophenone, Michlaz ketone, and 4-benzoyl-4'-methyldiphenyl sulfide; acridine compounds such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane; acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide; and oxime ester compounds such as 1,2-octanedione-1-[4-(phenylthio)phenyl]-2-(O-benzoyl oxime), 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone-1-(O-acetyl oxime), and 1-phenyl-1,2-propanedione-2-[O-(ethoxycarbonyl) oxime].

[0072] The content of component (D) in the curable resin composition is not particularly limited, but may be 0.2 to 15% by mass, 0.5 to 10% by mass, or 1 to 5% by mass, based on the total solid content of the curable resin composition.

[0073] (Component (E): Inorganic Filler) The curable resin composition according to this embodiment may further contain an inorganic filler as component (E). By including component (E), the adhesive strength and hardness of the permanent resist can be improved. Component (E) may be used alone or in combination of two or more types.

[0074] Examples of inorganic filler materials include silica, alumina, titania, tantalum oxide, zirconia, silicon nitride, barium titanate, barium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, lead titanate, lead zirconate titanate, lead lanthanum zirconate titanate, gallium oxide, spinel, mullite, cordierite, talc, aluminum titanate, yttria-containing zirconia, barium silicate, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, zinc oxide, magnesium titanate, hydrotalcite, mica, calcined kaolin, and carbon.

[0075] Component (E) may contain silica filler from the viewpoint of improving the heat resistance of the permanent resist, and may contain barium sulfate filler from the viewpoint of improving the heat resistance and adhesive strength of the permanent resist, or may contain both silica filler and barium sulfate filler. Furthermore, from the viewpoint of further improving heat dissipation, component (E) may contain inorganic oxide filler or silica filler. From the viewpoint of improving the dispersibility of the inorganic filler, inorganic filler that has been surface-treated with alumina or an organosilane compound beforehand may be used.

[0076] The shape of component (E) is not particularly limited, but it may be spherical from the viewpoint of further improving crack resistance.

[0077] The average particle size of component (E) may be 0.01 to 5.0 μm, 0.05 to 3.0 μm, 0.1 to 2.0 μm, or 0.15 to 1.0 μm, from the viewpoint of resolution.

[0078] The average particle size of component (E) is the average particle size of the inorganic filler dispersed in the curable resin composition, and is the value obtained by measurement as follows: First, the curable resin composition is diluted 1000 times with methyl ethyl ketone, and then the particles dispersed in the solvent are measured using a submicron particle analyzer (Beckman Coulter, Inc., product name "N5") in accordance with the international standard ISO 13321, with a refractive index of 1.38, and the particle diameter at 50% of the cumulative value (by volume) in the particle size distribution is taken as the average particle size.

[0079] The content of component (E) may be 5 to 80% by mass, 5 to 70% by mass, 6 to 60% by mass, or 10 to 50% by mass, based on the total solid content of the curable resin composition. When the content of component (E) is within the above range, the low coefficient of thermal expansion, heat resistance, and film strength can be further improved.

[0080] (Component (F): Pigment) The curable resin composition according to this embodiment may further contain a pigment as component (F) from the viewpoint of improving the identifiability or appearance of the manufacturing apparatus. As component (F), a coloring agent that produces a desired color when concealing wiring (conductor patterns) can be used. Component (F) may be used alone or in combination of two or more types.

[0081] Component (F) is preferably an organic pigment, and more preferably an organic pigment that is substantially free of metal elements. Examples of metal elements include transition metal elements, alkali metal elements, and alkaline earth metal elements. In this disclosure, metalloid elements such as silicon are not considered metal elements.

[0082] Examples of component (F) include azo pigments, indanthrene pigments, hydrogenated phthalocyanine, and indigo. Among these, azo pigments, indanthrene pigments, and hydrogenated phthalocyanine are preferred from the viewpoint of further suppressing the deterioration of synthetic oil and obtaining high heat resistance. Component (F) may consist of only at least one selected from the group consisting of azo pigments, indanthrene pigments, and hydrogenated phthalocyanine.

[0083] (F) The content of component (F) may be 0.01 to 5.0% by mass, 0.03 to 3.0% by mass, or 0.05 to 2.0% by mass, based on the total amount of solids in the curable resin composition, from the viewpoint of making the manufacturing equipment easier to identify and better concealing the wiring.

[0084] (Component (G): Photosensitizer) The curable resin composition of this embodiment may further contain a photosensitizer as component (G). By containing component (G) in the curable resin composition, the absorption wavelength of the active light used for exposure can be effectively utilized.

[0085] Examples of photosensitizers that are component (G) include thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; phosphine compounds such as triphenylphosphine; toluidine compounds such as N,N-dimethyltoluidine; anthracene compounds such as 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, and 2-ethyl-9,10-diethoxyanthracene; perylene compounds; coumarin compounds; pyrarisone compounds; oxazole compounds; benzoxazole compounds; thiazole compounds; triazole compounds; stilbene compounds; triazine compounds; thiophene compounds; naphthalimide compounds; and triarylamine compounds.

[0086] From the viewpoint of maintaining good via shape, the photosensitizer is preferably 2,4-dimethylthioxanthone or 2,4-diethylthioxanthone, and more preferably 2,4-diethylthioxanthone. Using 2,4-diethylthioxanthone tends to reduce scattered light to unexposed areas, and as a result, good via shape can be maintained.

[0087] The content of component (G) is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, even more preferably 0.1 to 2% by mass, and particularly preferably 0.3 to 1.5% by mass, based on the total solid content of the curable resin composition.

[0088] (Other components) The curable resin composition according to this embodiment may further contain various additives as needed. Examples of additives include polymerization inhibitors such as hydroquinone, methyl hydroquinone, hydroquinone monomethyl ether, catechol, and pyrogallol; silicone-based, fluorine-based, and vinyl resin-based defoaming agents; silane coupling agents; and flame retardants such as phosphate compounds, aromatic condensed phosphate esters, and halogen-containing condensed phosphate esters.

[0089] The curable resin composition according to this embodiment may contain organic fillers such as resin fillers, but may not contain them from the viewpoint of resolution. The content of organic fillers in the curable resin composition may be 1% by mass or less, or 0% by mass, based on the total amount of solids in the curable resin composition.

[0090] (Solvent) The curable resin composition according to this embodiment contains a solvent to dissolve and disperse each component, thereby facilitating application to a substrate and forming a coating film of uniform thickness.

[0091] Examples of solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; and esters such as ethyl acetate, butyl acetate, butyl cellosolve acetate, and carbitol acetate. The solvent may be used individually or in combination of two or more.

[0092] The amount of solvent added is not particularly limited, but the proportion of solvent in the curable resin composition may be 10 to 50% by mass, 20 to 40% by mass, or 25 to 35% by mass.

[0093] The curable resin composition of this embodiment can be prepared by uniformly mixing the above-mentioned components using a roll mill, bead mill, or the like.

[0094] (Metal Content) The curable resin composition of this embodiment has a metal content of 200 ppm by mass or less, based on the total amount of solids in the curable resin composition. By keeping the metal content within the above range, it is possible to obtain a cured product that does not easily cause discoloration or off-odor in the synthetic oil used for liquid immersion cooling. From the viewpoint of obtaining this effect more fully, the metal content is preferably 100 ppm by mass or less, and more preferably 20 ppm by mass or less. The lower limit of the metal content is not particularly limited and may be 0 ppm by mass.

[0095] The metal content of a curable resin composition can be measured by the following method: after dissolving the sample in an organic solvent (methyl ethyl ketone), the metal content can be determined by analyzing the elemental species and their concentrations using inductively coupled plasma mass spectrometry (ICP-MS).

[0096] [Curable Resin Film] The curable resin film according to this embodiment comprises a support film and a curable resin layer containing the curable resin composition described above. Figure 1 is a schematic cross-sectional view showing the curable resin film according to this embodiment. As shown in Figure 1, the curable resin film 1 comprises a support film 10 and a curable resin layer 20 formed on the support film 10. The curable resin film 1 may also be a photosensitive element comprising a photosensitive layer containing a photosensitive resin composition.

[0097] The curable resin film 1 can be produced by applying the curable resin composition according to this embodiment onto a support film 10 using a known method such as reverse roll coating, gravure roll coating, comma coating, or curtain coating, and then drying the coating to form a curable resin layer 20.

[0098] Examples of support films include polyester films such as polyethylene terephthalate and polybutylene terephthalate, and polyolefin films such as polypropylene and polyethylene. The thickness of the support film may be, for example, 5 to 100 μm. The thickness of the curable resin layer may be, for example, 5 to 50 μm, 5 to 40 μm, 10 to 30 μm, 15 to 30 μm, 20 to 30 μm, or 25 to 30 μm. The surface roughness of the support film is not particularly limited, but the arithmetic mean roughness (Ra) may be 1000 nm or less, 500 nm or less, or 250 nm or less.

[0099] The coating film can be dried using hot air drying, far-infrared radiation, or near-infrared radiation. The drying temperature may be 60-120°C, 70-110°C, or 80-100°C. The drying time may be 1-60 minutes, 2-30 minutes, or 5-20 minutes.

[0100] The curable resin layer 20 may further include a protective film 30 covering the curable resin layer 20. The curable resin film 1 may also have the protective film 30 laminated on the side of the curable resin layer 20 opposite to the side in contact with the support film 10. As the protective film 30, for example, a polymer film such as polyethylene or polypropylene may be used.

[0101] The range of solid content of each component other than volatile substances (components (A) to (G) and other components) in the curable resin layer 20 may be the same as the range of solid content of each component in the curable resin composition.

[0102] The metal content of the curable resin layer 20 may be the same as the range of metal content in the curable resin composition based on the total amount of solids in the curable resin composition.

[0103] [Printed Wiring Board] The printed wiring board according to this embodiment comprises a permanent resist containing a cured product of the curable resin composition according to this embodiment.

[0104] When the curable resin composition and curable resin film are a photosensitive resin composition and a photosensitive element, the method for manufacturing a printed circuit board according to this embodiment comprises the steps of: forming a photosensitive layer on a substrate using the above-mentioned photosensitive resin composition or photosensitive element; exposing and developing the photosensitive layer to form a resist pattern; and curing the resist pattern to form a permanent resist. An example of each step will be described below.

[0105] First, a substrate such as a copper-clad laminate is prepared, and a photosensitive layer is formed on the substrate. The photosensitive layer may be formed by coating a photosensitive resin composition onto the substrate and drying it. Examples of methods for coating the photosensitive resin composition include screen printing, spraying, roll coating, curtain coating, and electrostatic coating. The drying temperature may be 60 to 120°C, 70 to 110°C, or 80 to 100°C. The drying time may be 1 to 60 minutes, 2 to 30 minutes, or 3 to 20 minutes.

[0106] The photosensitive layer may be formed on a substrate by peeling off a protective film from a photosensitive element and laminating the photosensitive layer onto it. One method for laminating the photosensitive layer is to use a laminator for thermal lamination.

[0107] Next, the negative film is brought into direct contact with the photosensitive layer or into contact with it via a support film, and exposed by irradiation with active light. Examples of active light include electron beams, ultraviolet rays, and X-rays, with ultraviolet rays being preferred. As a light source, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, halogen lamps, etc., can be used. The exposure amount is 10 to 2000 mJ / cm². ２ , 100-1500mJ / cm ２ , or 300-1000 mJ / cm ２ That's fine.

[0108] After exposure, the unexposed areas are removed with a developer to form a resist pattern. Examples of development methods include dipping and spraying. Suitable developers include alkaline aqueous solutions such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, and tetramethylammonium hydroxide.

[0109] A pattern-cured film (permanent resist) can be formed on a resist pattern by performing at least one of the following treatments: post-exposure and post-heating. The exposure dose for post-exposure is 100 to 5000 mJ / cm². ２ , 500-2000mJ / cm ２ , or 700-1500 mJ / cm² ２ The heating temperature for the post-heating may be 100-200°C, 120-180°C, or 135-165°C. The heating time for the post-heating may be 5 minutes to 6 hours, 10 minutes to 3 hours, or 30 minutes to 2 hours.

[0110] The permanent resist may have vias with a diameter of 25 to 200 μm, or vias with a diameter of 25 to 100 μm. Furthermore, the permanent resist may have both large-diameter vias with a diameter of 70 μm or more and small-diameter vias with a diameter of 35 μm or less.

[0111] The permanent resist according to this embodiment can be used as an interlayer insulating layer or surface protective layer of a semiconductor element. A semiconductor element having an interlayer insulating layer or surface protective layer formed from a cured film of the above-described curable resin composition, and an electronic device including the semiconductor element, can be manufactured. The semiconductor element may be, for example, a memory, package, etc., having a multilayer wiring structure, a rewiring structure, etc. Examples of electronic devices include mobile phones, smartphones, tablet terminals, personal computers, and hard disk suspensions. By providing a patterned cured film formed from the curable resin composition according to this embodiment, highly reliable semiconductor elements and electronic devices can be provided.

[0112] The printed circuit board according to this embodiment can be used for immersion cooling of a semiconductor package by immersing it together with the semiconductor package in synthetic oil while the package is mounted on it. Even when such immersion cooling is performed, the deterioration of the synthetic oil can be suppressed, and discoloration of the synthetic oil can be suppressed. Furthermore, even if the synthetic oil is exposed to high temperatures (e.g., 60 to 100°C) for a long period of time (e.g., 200 hours) during immersion cooling, the printed circuit board according to this embodiment can suppress the deterioration of the synthetic oil (discoloration).

[0113] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0114] (Synthesis Example 1) Bisphenol F novolac type epoxy resin (manufactured by DIC Corporation, trade name "EXA-7376", in formula (II), Y ３ and Y ４ is a glycidyl group, R １２ 350 parts by mass of bisphenol F novolac-type epoxy resin having a structural unit of a hydrogen atom (epoxy equivalent: 186), 70 parts by mass of acrylic acid, 0.5 parts by mass of methylhydroquinone, and 120 parts by mass of carbitol acetate were charged and heated to 90°C and stirred to dissolve the mixture. Next, the obtained solution was cooled to 60°C, 2 parts by mass of triphenylphosphine were added, and the mixture was heated to 100°C and reacted until the acid value of the solution was 1 mg KOH / g or less. To the reacted solution, 98 parts by mass of tetrahydrophthalic anhydride (THPAC) and 85 parts by mass of carbitol acetate were added, and the mixture was heated to 80°C and reacted for 6 hours. After that, the solution was cooled to room temperature to obtain a solution of acid-modified vinyl group-containing resin (A-1) (acid-modified bisphenol F novolac-type epoxy acrylate) as component (A) with a solid content concentration of 73% by mass.

[0115] (Synthesis Example 2) In an autoclave equipped with a thermometer, a nitrogen introduction device / alkylene oxide introduction device, and a stirring device, 119.4 parts by mass of novolac-type cresol resin (manufactured by Aica Kogyo Co., Ltd., trade name "Shounol CRG951", OH equivalent: 119.4 g / eq.), 1.19 parts by mass of potassium hydroxide, and 119.4 parts by mass of toluene were charged, and the system was heated and the temperature increased while stirring and purging with nitrogen. Next, 63.8 parts by mass of propylene oxide were gradually introduced, and the temperature was raised to 125-132°C and 0-4.8 kg / cm³. ２ The reaction was carried out for 16 hours. After cooling to room temperature, 1.56 parts by mass of 89% phosphoric acid was added to the reaction solution and mixed to neutralize the potassium hydroxide, yielding a propylene oxide reaction solution of novolac-type cresol resin with a non-volatile content of 62.1% by mass and a hydroxyl value of 182.2 mg KOH / g. This solution contained an average of 1.08 moles of propylene oxide per equivalent of phenolic hydroxyl groups.

[0116] Next, 293.0 parts by mass of the obtained novolac-type cresol resin propylene oxide reaction solution, 43.2 parts by mass of acrylic acid, 11.53 parts by mass of methanesulfonic acid, 0.18 parts by mass of methylhydroquinone, and 252.9 parts by mass of toluene were charged into a reactor equipped with a stirrer, thermometer, and air blowing tube, and the reaction was carried out at 110°C for 12 hours while stirring and blowing air at a rate of 10 ml / min. Of the water produced by the reaction, 12.6 parts by mass of water was distilled off as an azeotropic mixture with toluene. After that, the solution was cooled to room temperature, neutralized with 35.35 parts by mass of a 15% by mass sodium hydroxide aqueous solution, and then washed with water. Subsequently, toluene was removed by distillation in an evaporator while substituting with 118.1 parts by mass of diethylene glycol monoethyl ether acetate (carbitol acetate) to obtain a novolac-type acrylate resin solution.

[0117] Next, 332.5 parts by mass of the obtained novolac-type acrylate resin solution and 1.22 parts by mass of triphenylphosphine were charged into a reactor equipped with a stirrer, thermometer, and air blowing tube. While stirring and blowing air at a rate of 10 ml / min, 60.8 parts by mass of tetrahydrophthalic anhydride (THPAC) were gradually added, and the reaction was carried out at 95-101°C for 6 hours. By cooling the reaction solution, a solution of acid-modified vinyl group-containing resin (A-2) (acid-modified novolac-type acrylate) as component (A) was obtained, with a solid acid value of 88 mg KOH / g and a solid content concentration of 70.9% by mass.

[0118] The following materials were prepared as components (B) to (F). B-1: Phenol novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name "RE-306") B-2: Tetramethyl biphenol type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name "YX4000") C-1: Mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name "KAYARAD DPHA") D-1: 2-methyl-[4-(methylthio)phenyl]morpholino-1-propanone (manufactured by IGM Resins B.V., trade name "Omnirad 907") D-2: 2,4-diethylthioxanthone (manufactured by Nagase & Co., Ltd., trade name "SB-PI799") E-1: Spherical silica filler (manufactured by Admatex, trade name "AdmaFine", particle size: 0.1-5.0 μm) F-1: Azo pigment (yellow organic pigment, manufactured by Sanyo Pigment Co., Ltd., product name "A1212") F-2: Indanthrene (blue organic pigment, manufactured by Sanyo Pigment Co., Ltd.) F-3: Hydrogenated phthalocyanine (blue organic pigment, manufactured by Sanyo Pigment Co., Ltd.) F-4: Ultramarine (blue inorganic pigment, manufactured by Tokyo Chemical Industry Co., Ltd.) F-5: Copper phthalocyanine (blue organic-inorganic complex, manufactured by Sanyo Pigment Co., Ltd., product name "A1225") F-6: Cobalt phthalocyanine (blue organic-inorganic complex, manufactured by Tokyo Chemical Industry Co., Ltd.) F-7: Iron(II) phthalocyanine (blue organic-inorganic complex, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0119] [Examples 1-6 and Comparative Examples 1-4] <Photosensitive Resin Compositions> Each component was blended in the amounts (parts by mass, equivalent to solid content) shown in Table 1 and kneaded in a three-roll mill. Then, carbitol acetate was added to achieve a solid content concentration of 70% by mass to prepare a photosensitive resin composition (curable resin composition).

[0120] <Photosensitive Element> A polyethylene terephthalate film with a thickness of 25 μm (manufactured by Toyobo Co., Ltd., product name "G2-25") was prepared as a support film. A solution of the photosensitive resin composition diluted with methyl ethyl ketone was applied to the support film so that the thickness after drying would be 20 μm, and dried at 75°C for 15 minutes using a hot air convection dryer to form a photosensitive layer (curable resin layer). Next, a polyethylene film (manufactured by Tamapoly Co., Ltd., product name "NF-15") was laminated as a protective film onto the surface opposite to the side of the photosensitive layer that is in contact with the support film to obtain a photosensitive element (curable resin film).

[0121] [Measurement of Metal Content] The metal content of the photosensitive resin composition was measured based on the total solid content using the following method. Specifically, the photosensitive resin composition was dissolved in methyl ethyl ketone, and then the elemental species and their concentrations were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the metal content. The results are shown in Table 1.

[0122] [Evaluation of Synthetic Oil Degradation] A 0.6 mm thick copper-clad laminate substrate (manufactured by Resonac Co., Ltd., product name "MCL-E-679") was prepared by laminating copper foil on both sides of a glass epoxy substrate. The copper foil on both sides of the copper-clad laminate substrate was removed with an aqueous solution of APS (ammonium persulfate) to obtain the glass epoxy substrate. The protective film was peeled off from the photosensitive elements produced in each example and comparative example, and the exposed photosensitive layer was placed on the glass epoxy substrate. Then, a laminate was obtained by laminating it using a press-type vacuum laminator (manufactured by Meiki Seisakusho Co., Ltd., product name "MVLP-500") under predetermined lamination conditions (vacuuming time: 25 seconds, atmospheric pressure: 4 kPa or less, lamination press time: 25 seconds, compression pressure: 0.4 MPa, press hot plate temperature: 80°C).

[0123] Next, the laminate is exposed to ultraviolet light at a rate of 300 mJ / cm² using an ultraviolet exposure apparatus. ２ After exposure with the specified exposure dose, the support film was peeled off. Furthermore, using an ultraviolet exposure apparatus, the laminate after the support film had been removed was exposed to 2000 mJ / cm². ２ After exposure with the specified exposure dose, the photosensitive layer was cured by heat treatment at 170°C for 1 hour using a drying oven. This resulted in a cured laminate having a cured photosensitive layer.

[0124] The obtained cured laminate was divided into 3 cm x 3 cm pieces, and each piece of cured laminate was completely immersed in 30 g of poly-α-olefin synthetic oil (PAO6, manufactured by Chevron Phillips Chemical), and heated in an oven at 125°C for 100 hours.

[0125] The poly-alpha-olefin synthetic oil, after heating as described above, was taken out with a dropper, and its degree of discoloration was quantitatively evaluated using an ultraviolet-visible spectrophotometer (Hitachi High-Tech Corporation, product name "U-3500"). The absorbance in the absorption wavelength range of 300-400 nm was measured, and the presence or absence of discoloration of the synthetic oil was evaluated based on the following evaluation criteria. If the evaluation result is "A", it can be determined that the discoloration of the synthetic oil has been suppressed. The results are shown in Table 1.

[0126] <Criteria for evaluating discoloration> A: No absorption was detected in the absorption wavelength range of 300-400 nm (peak absorption ≤ 0.1). B: Absorption was detected in the absorption wavelength range of 300-400 nm (peak absorption > 0.1).

[0127]

[0128] 1...Cureable resin film, 10...Support film, 20...Cureable resin layer, 30...Protective film.

Claims

1. A curable resin composition containing a curable resin, wherein the metal content is 200 ppm by mass or less based on the total solid content of the curable resin composition.

2. The curable resin composition according to claim 1, further containing a pigment.

3. The curable resin composition according to claim 1, comprising an acid-modified vinyl group-containing resin, a thermosetting resin, a photopolymerizable compound, a photopolymerization initiator, an inorganic filler, and a pigment.

4. The curable resin composition according to claim 2, wherein the pigment is an organic pigment.

5. The curable resin composition according to claim 2, wherein the pigment is at least one selected from the group consisting of azo pigments, indanthrene pigments, and hydrogenated phthalocyanines.

6. A curable resin film comprising a support film and a curable resin layer formed on the support film, wherein the curable resin layer contains the curable resin composition according to any one of claims 1 to 5.

7. A printed circuit board comprising a permanent resist containing a cured product of a curable resin composition according to any one of claims 1 to 5.

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