JP7371321B2 - Curable resin composition, cured product, and printed wiring board - Google Patents

Description

The present invention relates to a curable resin composition, a cured product, and a printed wiring board.

Electronic devices such as smartphones and personal computers use printed wiring boards equipped with electronic elements having various functions. In such printed wiring boards, circuits for electrically connecting electronic elements are formed on an insulating base material. Generally, such a circuit is made of copper, and its thickness is, for example, about 18 μm. As electronic devices become smaller, this circuit is designed to be thinner.

For such circuits, in order to prevent short circuits between the circuits, it is common practice to apply an insulating material called solder resist ink to the surface of the printed wiring board to form an insulating layer. ing.

By the way, circuits with a thickness exceeding 50 μm are sometimes used in printed wiring boards to which large currents or large voltages are applied, which are used in communication servers, electric vehicles, and the like. In such a case, it is difficult to apply solder resist ink to the side surfaces of the circuit, etc. because the level difference (that is, height difference) between the surface of the circuit on the printed wiring board and the surface of the base material of the printed wiring board becomes large. As a result, there is a problem in that it becomes difficult to flatten the surface of the solder resist layer.

Therefore, in order to flatten the surface of the solder resist layer, it has been proposed to use a solder resist film made of solder resist ink in the form of a film in advance. As an example of a solder resist film, Patent Document 1 discloses that a 1.6 mm thick FR-4 copper clad laminate having a 35 μm thick copper foil on the entire surface is polished once with buff polishing #600 and then #1000. , the resist layer has a resist layer whose spectral reflectance measured every 10 nm at wavelengths of 430 to 700 nm is 65% or more when measured in reflection mode with a color difference meter after laminating the solder resist film with a vacuum laminator. , from a photosensitive resin composition in which the resist layer contains a base polymer (A), an ethylenically unsaturated compound (B), a photopolymerization initiator (C), a white pigment (D), and a solvent (E). A solder resist film is disclosed in which the photopolymerization initiator (C) contains an acylphosphine oxide photopolymerization initiator (C1) and an alkylphenone photopolymerization initiator (C2). .

JP2010-020264

However, even if a film-type material is used like the solder resist film described in Patent Document 1, there is still room for improvement in flattening the surface of the cured product.

An object of the present invention is to provide a curable resin composition, a cured product, and a printed wiring board that can facilitate polishing of a cured product and flatten the surface thereof.

As a result of various experiments on combinations of curable resin compositions, cured products, and printed wiring boards, the present inventors have found that warping that occurs due to shrinkage of curable resin compositions during curing can be easily avoided during polishing work. found that it has an impact. Furthermore, as a result of intensive research, the present inventors have found that when the cured product of the curable resin composition exhibits predetermined characteristics regarding stress, elastic storage modulus, and viscosity, the problem of warping can be solved, and the polishing of the cured product can be performed easily. We have obtained the knowledge that it can be made easier.

That is, one aspect of the present invention is a curable resin composition, wherein the curable resin composition has a rotor rotation rate of 25° C. as measured by a cone-plate rotational viscometer in accordance with JIS-Z8803:2011. The viscosity of the 30 second value measured at a speed of 5.0 rpm is 200 dPa·s or more and 3000 dPa·s or less, and the cured product of the curable resin composition has the following properties (1) to (2). A curable resin composition comprising:
(1) Stress is 0.5N or more and less than 1.3N;
(2) Storage modulus at 30°C is less than 8.8 GPa.

Another aspect of the present invention is that the cured product of the curable resin composition preferably has the following characteristic (3):
(3) Glass transition temperature is 120°C or higher.

Another aspect of the present invention is that the curable resin composition comprises:
(A) an epoxy resin having a liquid bisphenol skeleton;
(B) a curing agent; and (C) an inorganic filler.

Another aspect of the present invention is that the curable resin composition comprises:
(D) It further contains a polybutadiene epoxy resin.

Another aspect of the present invention is a cured product obtained by curing a curable resin composition.

Another aspect of the present invention is a printed wiring board having the cured product.

According to the present invention, it is possible to provide a curable resin composition, a cured product, and a printed wiring board that can facilitate polishing of a cured product and flatten the surface thereof.

Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

The curable resin composition, cured product, and printed wiring board according to this embodiment will be described below.

<Curable resin composition>
The curable resin composition according to this embodiment includes a curable resin, a curing agent, and an inorganic filler.

==Curing resin==
The curable resin used in the present invention is a thermosetting resin or a photocurable resin, and may be a mixture thereof, but a thermosetting resin is preferable because it has excellent deep curability and heat resistance. It is preferable. In this specification, the term "liquid" refers to a liquid or semi-liquid state (paste state) that has fluidity at at least one of 20°C and 45°C.

(thermosetting resin)
The thermosetting resin may be any resin that hardens upon heating and exhibits electrical insulation properties. Specific examples of thermosetting resins include novolak-type phenolic resins such as phenol novolak resin, cresol novolak resin, bisphenol A novolak resin, and triazine skeleton-containing phenol novolak resin; unmodified resol phenolic resin, tung oil, linseed oil, and walnut oil. Phenolic resins such as resol type phenolic resins such as oil-modified resol phenolic resins modified with etc.; bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy resin, Bisphenol type epoxy resins such as bisphenol P type epoxy resin and bisphenol Z type epoxy resin; Novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolak type epoxy resin; biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, aryl alkylene type Epoxy resins such as epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, phenoxy type epoxy resin, dicyclopentadiene type epoxy resin, norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin; urea resin, Resins with triazine rings such as melamine resins; unsaturated polyester resins; maleimide resins such as bismaleimide compounds; polyurethane resins; diallyl phthalate resins; benzoxazine resins; polyimide resins; polyamideimide resins; benzocyclobutene resins, novolac-type cyanate resins , cyanate ester resins such as bisphenol cyanate resins such as bisphenol A cyanate resin, bisphenol E cyanate resin, and tetramethylbisphenol F cyanate resin; and silicone resins. These can be used alone or in combination of two or more.

(photocurable resin)
Examples of the photocurable resin include curable resins that can be cured by radical addition polymerization reaction with active energy rays. Specific examples of radical addition polymerization reactive components having one or more ethylenically unsaturated groups in the molecule include polyester (meth)acrylate, polyether (meth)acrylate, urethane (meth)acrylate, and carbonate (meth)acrylate. ) acrylate, epoxy (meth)acrylate, etc. Specifically, glycol diacrylates such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; ; Aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; Polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tris-hydroxyethyl isocyanurate or polyvalent acrylates such as ethylene oxide adducts, propylene oxide adducts, or ε-caprolactone adducts; phenoxy acrylate, bisphenol A diacrylate, and ethylene oxide or propylene oxide adducts of these phenols, etc. Polyvalent acrylates of glycidyl ether such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, triglycidyl isocyanurate; Not limited to the above, polyether polyol, polycarbonate diol, hydroxyl group Examples include acrylates obtained by direct acrylation of polyols such as terminal polybutadiene and polyester polyols or urethane acrylates via diisocyanates, melamine acrylates, and at least one of methacrylates corresponding to the acrylates. Note that in this specification, (meth)acrylate is a term that collectively refers to acrylate, methacrylate, and mixtures thereof, and the same applies to other similar expressions. It is preferable that the photocurable resin described above is liquid.

(Alkali-soluble resin)
The curable resin composition can contain an alkali-soluble resin. Examples of the alkali-soluble resin include carboxyl group-containing resins and phenol resins. It is preferable to use a carboxyl group-containing resin from the viewpoint of developability. The carboxyl group-containing resin may be a carboxyl group-containing photosensitive resin having an ethylenically unsaturated group, and may or may not have an aromatic ring.

The curable resin according to this embodiment is preferably (A) an epoxy resin having a liquid bisphenol skeleton.

((A) Liquid epoxy resin having a bisphenol skeleton)
Examples of liquid bisphenol skeleton epoxy resins include bisphenol A epoxy resins and their hydrogenated products, bisphenol F epoxy resins and their hydrogenated products, and bisphenol S epoxy resins and their hydrogenated products that meet the above-mentioned "liquid" conditions. Hydrogenated products, bisphenol AD type epoxy resins and their hydrogenated products, bisphenol E type epoxy resins and their hydrogenated products, bisphenol E type epoxy resins and their hydrogenated products, bisphenol AP type epoxy resins and their hydrogenated products, bisphenol AF type epoxy resin and its hydrogenated product, bisphenol B type epoxy resin and its hydrogenated product, bisphenol BP type epoxy resin and its hydrogenated product, bisphenol C type epoxy resin and its hydrogenated product, bisphenol G type epoxy resin and its water Additives, bisphenol M type epoxy resin and its hydrogenated product, bisphenol P type epoxy resin and its hydrogenated product, bisphenol PH type epoxy resin and its hydrogenated product, bisphenol TMC type epoxy resin and its hydrogenated product, bisphenol Z type Epoxy resins and hydrogenated products thereof are used. Further, one type of these may be used alone, or two or more types may be used in combination. Particularly preferably, bisphenol A epoxy resins and hydrogenated products thereof, and bisphenol F epoxy resins and hydrogenated products thereof can be used.

Commercially available liquid bisphenol skeleton epoxy resins include, for example, jER828 manufactured by Mitsubishi Chemical Corporation, YD-127 and YD-128 manufactured by Nippon Steel Chemical & Materials Co., Ltd., and Araldite GY240 and Araldite manufactured by Huntsman Japan Co., Ltd. Bisphenol A epoxy resins such as GY250, Araldite GY260, Araldite GY261, Araldite GY266, Araldite GY2600 (all trade names), Epiclon 840 and Epiclon 850 (all trade names) manufactured by DIC Corporation; Nippon Steel Chemical & Materials Co., Ltd. Hydrogenated bisphenol F-type epoxy resins such as YDF-170 and YDF-175 (all trade names) manufactured by the company; Epiclon 830, Epiclon 830-S, and Epiclon 835 manufactured by DIC Corporation, and Epiclon 835 manufactured by Mitsubishi Chemical Corporation. Bisphenol F type epoxy resin such as JER807 (all product names); Hydrogenated bisphenol A type epoxy resin ST-3000 (product name) manufactured by Nippon Steel Chemical & Materials Co., Ltd.; EPOX-MK R710 manufactured by Printec Co., Ltd. There are bisphenol E type epoxy resins such as

(A) The amount of liquid epoxy resin having a bisphenol skeleton is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, based on the total amount of epoxy resin, in terms of solid content. preferable.

==(B) Curing agent==
(B) The curing agent cures the thermosetting resin. Examples of curing agents include amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, imidazole latent curing agents such as imidazole adducts, and polymers containing these functional groups. A plurality of these may be used. Examples of amines include dicyandiamide and diaminodiphenylmethane. Examples of imidazoles include alkyl-substituted imidazole and benzimidazole. Examples of polyfunctional phenols include hydroquinone, resorcinol, bisphenol A, and its halogen compounds, as well as novolacs, which are condensates of these with aldehydes, resol resins, and the like. Examples of the acid anhydride include phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, and benzophenonetetracarboxylic acid. Isocyanates include tolylene diisocyanate and isophorone diisocyanate, and these isocyanates may be masked with phenols or the like.

Amines and imidazoles can be preferably used from the viewpoints of adhesion between the insulating portion of electronic components such as printed wiring boards and conductor wiring circuits, storage stability, and heat resistance. Adduct compounds of aliphatic polyamines such as alkylene diamines having 2 to 6 carbon atoms, polyalkylene polyamines having 2 to 6 carbon atoms, aromatic ring-containing aliphatic polyamines having 8 to 15 carbon atoms, or isophorone diamine, 1,3-bis Preferably, the main component is an adduct compound of an alicyclic polyamine such as (aminomethyl)cyclohexane, or a mixture of an adduct compound of the aliphatic polyamine and an adduct compound of the alicyclic polyamine. Particularly preferred is a curing agent whose main component is an adduct compound of xylylene diamine or isophorone diamine.

The adduct compound of an aliphatic polyamine is preferably one obtained by subjecting the aliphatic polyamine to an addition reaction with an aryl glycidyl ether (particularly phenyl glycidyl ether or tolyl glycidyl ether) or an alkyl glycidyl ether. The adduct compound of the alicyclic polyamine is preferably one obtained by subjecting the alicyclic polyamine to an addition reaction with n-butyl glycidyl ether, bisphenol A diglycidyl ether, or the like.

Examples of aliphatic polyamines include alkylene diamines having 2 to 6 carbon atoms such as ethylenediamine and propylene diamine, polyalkylene polyamines having 2 to 6 carbon atoms such as diethylenetriamine and triethylenetriamine, and aromatic ring-containing aliphatic compounds having 8 to 15 carbon atoms such as xylylene diamine. Examples include polyamines of the group polyamines. Examples of commercially available modified aliphatic polyamines include FXE-1000 or FXR-1020, FujiCure FXR-1030, FujiCure FXR-1080, FXR-1090M2 (all trade names, manufactured by T&K TOKA Co., Ltd.), Ancamine 2089K, Examples include Sunmide P-117, Sunmide X-4150, Ancamine 2422, Surwet R, Sunmide TX-3000, and Sunmide A-100 (all trade names, manufactured by Evonik Japan Co., Ltd.).

Examples of the alicyclic polyamine include isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, and laromine. Commercially available modified alicyclic polyamines include, for example, Ancamine 1618, Ancamine 2074, Ancamine 2596, Ancamine 2199, Sanmide IM-544, Sanmide I-544, Ancamine 2075, Ancamine 2280, Ancamine 1934, and Ancamine 2228 (all trade names). , manufactured by Evonik Japan Co., Ltd.), Daitoclar F-5197, Daitoclar B-1616 (all product names, manufactured by Daito Sangyo Co., Ltd.), FujiCure FXD-821, FujiCure 4233 (all product names, manufactured by T&K TOKA Co., Ltd.) ), jER Cure 113 (trade name, manufactured by Mitsubishi Chemical Corporation), and Laromine C-260 (trade name, manufactured by BASF Japan Corporation). Other polyamine type curing agents include EH-5015S (trade name, manufactured by ADEKA Co., Ltd.).

Examples of imidazoles include reaction products of epoxy resin and imidazole. For example, 2-methylimidazole, 4-methyl-2-ethylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 1 -cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole and the like. Commercially available imidazoles include, for example, imidazoles such as 2E4MZ, C11Z, C17Z, and 2PZ (all trade names; these are reaction products of epoxy resin and imidazole), 2MZ-A, 2E4MZ-A, and 2MZA-PW ( 2MZ-OK, 2PZ-OK (all trade names, these are isocyanurates of imidazole), 2PHZ, 2P4MHZ (all trade names, these are imidazole) hydroxymethyl form) (all of the above are manufactured by Shikoku Kasei Kogyo Co., Ltd.), and the like. Examples of commercially available imidazole-type latent curing agents include Cureduct P-0505 (trade name, manufactured by Shikoku Kasei Kogyo Co., Ltd.). The curing agent used in combination with imidazoles is preferably a modified aliphatic polyamine, a polyamine type curing agent, or an imidazole type latent curing agent.

Note that these curing agents may be used alone or in combination of two or more. When two or more kinds are used together, one of them may be imidazoles.

In the curable resin composition of the present embodiment, the blending amount of the curing agent (B) is preferably 1 to 20 parts by mass, and 3 to 10 parts by mass, based on 100 parts by mass of the epoxy resin, in terms of solid content. It is more preferable to contain 1%.

==(C) Inorganic filler==
The inorganic filler not only relieves stress due to curing shrinkage and adjusts the linear expansion coefficient, but also increases the physical strength of the cured product. As the inorganic filler, known inorganic fillers used in general resin compositions can be used. Specifically, nonmetals such as silica, barium sulfate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, mica, talc, and organic bentonite Examples include fillers and metal fillers such as copper, gold, silver, palladium, and silicone. One type of these inorganic fillers may be used alone, or two or more types may be used in combination.

Among these inorganic fillers, calcium carbonate, silica, barium sulfate, and aluminum oxide, which are excellent in low hygroscopicity and low volume expansion, are preferably used, and among them, silica and calcium carbonate are more preferably used. The silica may be either amorphous or crystalline, or a mixture thereof. Particularly preferred is amorphous (fused) silica. Further, the calcium carbonate may be either natural heavy calcium carbonate or synthetic precipitated calcium carbonate.

The shape of the inorganic filler is not particularly limited, and examples include spherical, acicular, plate-like, scale-like, hollow, irregular, hexagonal, cubic, and flaky shapes, but a high amount of inorganic filler can be incorporated. From this point of view, a spherical shape is preferable.

The amount of the inorganic filler (C) in the curable resin composition of the present invention is preferably 20 to 150 parts by mass, and preferably 30 to 120 parts by mass, based on 100 parts by mass of the epoxy resin, in terms of solid content. It is more preferable to do so.

==(D) Polybutadiene epoxy resin==
Furthermore, the curable resin composition according to the present embodiment preferably contains (D) a polybutadiene epoxy resin in that it can further suppress warpage of the cured product.

Polybutadiene epoxy resin has a double bond in the polymer residue, and a portion of the double bond is epoxidized. For example, epoxidized products of copolymerized polyenes having a butadiene structure can be mentioned. Among them, epoxidized polybutadiene is preferred. Specific examples of such resins include PB3600 and PB4700 manufactured by Daicel Corporation, JP-100 and JP-200 manufactured by Nippon Soda Corporation, BF-1000 manufactured by ADEKA Corporation, and YX7400 series manufactured by Mitsubishi Chemical Corporation. can be mentioned.

The amount of the polybutadiene epoxy resin (D) in the curable resin composition of the present invention is preferably 5 to 40% by mass, and preferably 5 to 30% by mass, based on the total amount of epoxy resin, in terms of solid content. It is more preferable to do so.

The curable resin composition of the present embodiment is preferable because it does not contain a solvent (that is, it is a solvent-free system), so that the bubble release property is further improved, and as a result, the heat resistance is also further improved. Note that the curable resin composition of this embodiment does not exclude anything other than a liquid resin component (for example, a resin component in a solid or semi-solid state). That is, if the curable resin composition is in a liquid state with fluidity at at least one of 20°C and 45°C, the resin component, which is other than a liquid at at least one of 20°C and 45°C, can be used alone. May contain.

<Other additive ingredients>
The curable resin composition of the present invention may further contain a photopolymerization initiator, a photoacid generator, a photobase generator, a photoinitiation aid, a cyanate compound, an elastomer, a mercapto compound, a urethanization catalyst, a thixotropic Thickening agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper inhibitors, antioxidants, rust inhibitors, thickeners such as organic bentonite and montmorillonite, silicone-based, fluorine-based, and highly At least one kind of antifoaming agent and leveling agent such as molecular type, silane coupling agent such as imidazole type, thiazole type, triazole type, flame retardant such as phosphorus compound such as phosphinate, phosphate ester derivative, phosphazene compound etc. Components such as the following can be blended. As these materials, those known in the field of electronic materials can be used.

Examples of the photoacid generator include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, p-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, 4 -Chlorphenyldiphenylsulfonium hexafluorophosphate, 4-chlorphenyldiphenylsulfonium hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate, bis[4-(diphenylsulfonio)phenyl] Examples include sulfide bishexafluoroantimonate, (2,4-cyclopentadien-1-yl)[(1-methylethyl)benzene]-Fe-hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and the like.

Examples of photobase generators include oxime ester compounds, α-aminoacetophenone compounds, acyloxyimino groups, N-formylated aromatic amino groups, N-acylated aromatic amino groups, nitrobenzyl carbamate groups, and alkoxybenzyl carbamates. Examples include compounds having substituents such as groups.

The curable resin composition according to the present embodiment includes a thermosetting resin composition, a photocurable resin composition, and a photocurable thermosetting resin composition, and a cured product can be easily produced, and Thermosetting resin compositions are preferred in terms of their excellent curability and heat resistance.

<Cured product>
The cured product according to this embodiment is obtained by curing the above-mentioned curable resin composition.

In the present embodiment, the cured product of the curable resin composition means, when the curable resin composition is used as a thermosetting resin composition, a differential scanning calorimeter (DSC) measured before and after curing the curable resin composition. 5°C/min. The reaction rate calculated from the ratio of each measured calorific value is 80% or more when measured at a heating rate of 20 to 250°C. Examples of the measuring device include differential scanning calorimeter DSC8500 manufactured by PerkinElmer.

On the other hand, when the curable resin composition of the present invention is used as a photocurable resin composition, the curable resin composition is exposed to an integrated light amount of 1000 mJ/cm ² using an ultraviolet exposure machine equipped with a high-pressure mercury lamp. refers to something that

Furthermore, when the curable resin composition of the present invention is used as a photocurable thermosetting resin composition, the curable resin composition is dried at 80°C for 30 minutes in a hot air circulation drying oven, and then dried with a high-pressure mercury lamp. Exposure is performed using an ultraviolet exposure machine equipped with a lamp at an integrated light intensity of 1000 mJ/cm ² , and the product is further cured at 180° C. for 60 minutes in a hot air circulation drying oven.

The cured product of the curable resin composition of this embodiment has the following characteristics (1) and (2).
(1) Stress is 0.5N or more and less than 1.3N.
(2) Storage modulus at 30°C is less than 8.8 GPa.

The storage modulus in this embodiment is measured as follows.
That is, a curable resin composition was applied to the glossy surface of a 18 μm copper foil (GTS-MP foil (manufactured by Furukawa Electric Co., Ltd.)) so that the coating thickness after curing would be 100 ± 50 μm. Apply by screen printing. Thereafter, the curable resin composition is thermally cured at 150° C. for 60 minutes to produce a cured product. The prepared cured product is peeled off from the copper foil and cut into pieces of 5±0.3 mm×50±5 mm.

Cutting was performed using a viscoelasticity measuring device (RSA-G2 manufactured by TA Instruments) under the conditions of a measurement temperature of 25 to 300 °C, a heating rate of 5 °C/min, a loading gap of 10 mm, a frequency of 1 Hz, and an axial force of 0.05 N. The storage modulus of the piece was measured. At this time, the storage elastic modulus at 30° C. in the measurement is taken as the measured value.

Note that the storage modulus in this embodiment is preferably 6.0 GPa or less at 30°C.

Moreover, the stress measurement in this embodiment is as follows.
That is, in the measurement of the storage modulus described above, the value obtained by subtracting the minimum value from the maximum value of Axial force is defined as the stress value (that is, the stress applied during reflow).

The stress in this embodiment is preferably 0.5N or more and 1.2N or less.

Furthermore, the viscosity of the curable resin composition in this embodiment is measured as follows.
That is, in accordance with JIS-Z8803:2011, specifically JIS-Z8803:2011 10 "Method of measuring viscosity using a conical-flat rotary viscometer", a conical-flat rotary viscometer (cone-plate type) ( The viscosity was measured using a TVE-33H (manufactured by Toki Sangyo Co., Ltd., rotor 3° x R9.7) at 25° C. and a rotor rotation speed of 5.0 rpm for 30 seconds.

The viscosity in this embodiment is preferably 400 dPa·s or more and 1200 dPa·s or less in a 30 second value measured at 25° C. and a rotor rotation speed of 5.0 rpm.

The reason why it becomes easier to polish the cured product of the curable resin composition and to flatten its surface by satisfying (1) and (2) above is surmised as follows. . That is, the cured product of the curable resin composition has a storage modulus in the range (1), so that it has a hardness suitable for polishing work. Further, by setting the stress in the range (2), warpage of the cured product (or warpage of a printed wiring board coated with the cured product) can be suppressed. That is, the cured product of such a curable resin composition has appropriate hardness and is suppressed from warping, so that it is in a suitable state for polishing work. As a result, polishing of the cured product can be easily performed. Therefore, a smooth solder resist layer can be formed on the printed circuit board. Furthermore, since the viscosity is in the range of 200 dPa・s to 3000 dPa・s in the 30 second value measured under the conditions of 25° C. and a rotor rotation speed of 5.0 rpm, in the defoaming process performed before curing, Good bubble release properties
become. Therefore, it is presumed that it can be suitably used as a filler for printed wiring boards. Note that the explanation of the above reason does not negate other reasons.

The stress and storage modulus of the cured product of the curable resin composition can be adjusted to 0.5 N or more and less than 1.3 N, respectively, by appropriately adjusting the types and amounts of each component contained in the curable resin composition. and less than 8.8 GPa. For example, even if the resin component contains a component that tends to generate stress, it can be adjusted to the desired range by adjusting at least one of the inorganic filler and the curing agent. .

Furthermore, the viscosity of the cured product of the curable resin composition can be set to 200 dPa·s or more and 3000 dPa·s or less by appropriately adjusting the types and blending amounts of each component of the curable resin composition. For example, even if the size of the inorganic filler is small and the viscosity tends to increase, the viscosity can be maintained within this range by appropriately adjusting at least one of the resin and curing agent components, the manufacturing method, etc. be able to.

Examples of the cured product of the curable resin composition include a cured film obtained by applying the curable resin composition to an object to be coated and curing it. The object to be coated is not particularly limited, and may be any object on which a cured film can be provided.

The method of applying the curable resin composition is not particularly limited, and may include dip coating, flow coating, roll coating, bar coater, screen printing, curtain coating, inkjet coating, dispensing, etc. Various methods can be applied. Among these, screen printing is preferred.

<Printed wiring board>
The curable resin composition according to this embodiment can be used to fill in depressions formed between copper circuits of a predetermined thickness arranged on a printed wiring board. For example, after applying the curable resin composition according to the present embodiment to a copper circuit (e.g., a step with a printed wiring board, a side surface of a copper circuit), and filling a depression formed between the copper circuits, , by at least one of heating and light irradiation. This curable resin composition can be suitably used for printed wiring boards in which the thickness of the copper circuit exceeds 50 μm. In particular, it is preferable to use it when the thickness of the copper circuit is in the range of 50 μm to 600 μm.

The viscosity suitable for coating the curable resin composition on a printed wiring board is, for example, 200 dPa·s or more and 3000 dPa·s or less (measured with a cone-plate rotational viscometer in accordance with JIS-Z8803:2011. .0 rpm).

When the curable resin composition is a thermosetting resin composition, the curable resin composition in the printed wiring board can be cured by heating at 60 to 220°C for 20 to 240 minutes, and by hot air circulation. Using a drying oven, IR oven, hot plate, convection oven, etc. equipped with a steam-based air heating heat source, hot air in the dryer is brought into countercurrent contact or is blown onto the support from a nozzle. be able to. In addition, when the thermosetting resin composition contains a photobase generator, for example, by irradiating it with light before the heating step, the generated base can be made into a liquid form, such as a thermosetting resin such as an epoxy resin having a bisphenol skeleton. By performing an addition reaction on the resin, the coating film of the curable resin composition can be cured to a deeper part.

On the other hand, when the curable resin composition is a photocurable resin composition, curing of the curable resin composition in the printed wiring board is performed using an ultraviolet exposure machine equipped with a high-pressure mercury lamp, for example, at approximately 500 to 2000 mJ/cm ² . By performing exposure (light irradiation) with an integrated light amount of , the exposed portion (the portion irradiated with light) is cured, so that it can be cured.

Further, when the curable resin composition is a photocurable thermosetting resin composition, curing of the curable resin composition in the printed wiring board is carried out by drying the solvent at a temperature of about 80 to 100°C in a hot air circulation drying oven, for example. For example, by exposing (light irradiating) the resin layer obtained after heating to a temperature and volatilizing it to dryness using an ultraviolet exposure machine equipped with a high-pressure mercury lamp with an integrated light intensity of about 500 to 2000 mJ/cm ² . , the exposed area (portion irradiated with light) is cured. Specifically, using a contact or non-contact method, selective exposure to active energy rays is performed through a patterned photomask, or direct pattern exposure is performed using a laser direct exposure machine, and the unexposed areas are exposed to a dilute alkaline aqueous solution ( For example, a resist pattern is formed by developing with a 0.3 to 3 mass % sodium carbonate aqueous solution). Further, for example, it can be cured by heating to a temperature of about 100 to 180° C. for thermal curing (post-curing).

The obtained cured product is then polished. Specifically, the polishing is performed using a buffing machine using a high-cut buff or the like until the copper surface of the copper circuit is exposed.

[Example]
Next, a description will be given of tests conducted by the present inventor regarding a curable resin composition and a cured product thereof.

<Preparation of curable resin composition>
The components listed in Tables 1 and 2 were blended, stirred, and kneaded and dispersed in a three-roll mill to obtain curable resin compositions of Examples 1 to 9 and Comparative Examples 1 to 7.

Note that *1 to *25 in Tables 1 and 2 indicate the following contents.
*1: jER-807 (Mitsubishi Chemical Corporation), epoxy resin with liquid bisphenol skeleton (bisphenol F type epoxy resin)
*2: jER-828 (Mitsubishi Chemical Corporation), epoxy resin with liquid bisphenol skeleton (bisphenol A type epoxy resin)
*3: jER-152 (Mitsubishi Chemical Corporation), phenol novolak epoxy resin *4: TEPIC-PAS B22 (Nissan Chemical Industries, Ltd.), triglycidyl isocyanurate *5: ED-505 (ADEKA Corporation), triglycidyl isocyanurate Methylolpropane type epoxy resin *6: YX-8800 (Mitsubishi Chemical Corporation), epoxy resin with anthracene skeleton *7: Celoxide 2021P (Daicel Corporation), alicyclic epoxy resin *8: NC-3000H (Nippon Kayaku ), biphenyl skeleton epoxy resin *9: JP-100 (Nippon Soda Co., Ltd.), epoxidized polybutadiene (polybutadiene epoxy resin), viscosity: 220 dPa・s/45°C
*10: JP-200 (Nippon Soda Co., Ltd.), epoxidized polybutadiene (polybutadiene epoxy)
resin), viscosity: 1000dPa・s/45℃
*11: PB3600 (Daicel Corporation), epoxidized polybutadiene (polybutadiene epoxy resin), viscosity: 200 to 700 dPa・s/45°C
*12: PB4700 (Daicel Corporation), epoxidized polybutadiene (polybutadiene epoxy resin), viscosity: 20 to 120 dPa・s/45°C
*13: MX-965 (Kaneka Corporation), silicone rubber dispersed in bisphenol F-type epoxy resin *14: SH-203 (Dow Toray Industries, Inc.), alkyl-modified silicone oil *15: KBM-403 ( Shin-Etsu Chemical Co., Ltd.), silane coupling agent *16: KS-66 (Shin-Etsu Chemical Co., Ltd.), silicone resin *17: Rikacid MH-700 (Shin Nippon Chemical Co., Ltd.), acid anhydride *18: MEHC- 7851H (Meiwa Kasei Co., Ltd.), phenolic resin *19:2MZA-PW (Shikoku Kasei Co., Ltd.), curing agent (imidazole curing agent)
*20: Tetraphenylphosphonium tetraphenylborate (Tokyo Kasei Kogyo Co., Ltd.), phosphonium salt type curing accelerator *21: Softon 2600 (Bihoku Funka Kogyo Co., Ltd.), inorganic filler (calcium carbonate) *22: Softon 1800 ( Bihoku Funka Kogyo Co., Ltd.), inorganic filler (calcium carbonate) *23: FB-74 (Denka Co., Ltd.), inorganic filler (silica)
*24: SO-E2 (Admatex Co., Ltd.), inorganic filler (silica)
*25: Shinano Random GP#1200 (Shinano Electric Smelting Co., Ltd.), inorganic filler (silicon carbide)

<Measurement of physical property values and evaluation of characteristics>
Physical property values and characteristics of the prepared curable resin compositions of Examples and Comparative Examples were measured and evaluated as follows.

(Measurement of physical property values)
The viscosity, storage modulus, glass transition temperature, and stress of the curable resin composition were measured by the following methods.

・Viscosity JIS-Z8803:2011, specifically JIS-Z8803:2011 10 "Viscosity measurement method using a conical-flat plate rotational viscometer" (cone-plate rotational viscometer (cone plate type)) The viscosity was measured using a TVE-33H (manufactured by Toki Sangyo Co., Ltd., rotor 3° x R9.7) at 25° C. and a rotor rotation speed of 5.0 rpm for 30 seconds.

- A curable resin composition was applied to the glossy surface of a copper foil (GTS-MP foil (manufactured by Furukawa Electric Co., Ltd.)) with a storage modulus of 18 μm to a coating thickness of 100 ± 50 μm after curing. It was applied by screen printing. Thereafter, the curable resin composition was thermally cured at 150° C. for 60 minutes to produce a cured product. The produced cured product was peeled off from the copper foil and cut into pieces of 5±0.3 mm×50±5 mm.

The measurement temperature was 25 to 300°C, heating rate was 5°C/min, loading gap was 10mm, frequency was 1Hz, and Axial force was 0.05N using a viscoelasticity measurement device (RSA-G2 manufactured by TA Instruments). The storage modulus of the pieces was measured. At this time, the storage elastic modulus at 30°C in the measurement was taken as the measured value.

-Glass transition temperature In measuring the storage modulus, the loss tangent tan δ at each temperature was calculated, and the temperature at which tan δ reached its peak was defined as the glass transition temperature.

- Stress In measuring the storage modulus, the value obtained by subtracting the minimum value from the maximum value of Axial force was defined as the stress value (that is, the stress applied during reflow).

For the curable resin compositions that have been cured, the curable resin compositions were measured using a differential scanning calorimeter (manufactured by PerkinElmer, DSC8500) at 5°C/min. before and after curing. The reaction rate was calculated from the ratio of each measured calorific value, and it was confirmed that the reaction rate was 80% or more.

(Evaluation of characteristics)
The curable resin compositions of Examples and Comparative Examples were evaluated in terms of characteristics such as debubbling properties, polishing properties, heat resistance, and warpage using the following methods.

・Bubble removal property As a pre-treatment, one surface of a double-sided printed circuit board with a straight pattern with copper thickness of 105 μm, L (line: wiring width)/S (space: interval width) of 400 μm/300 μm, and circuit length of 2 cm was applied as a pre-treatment. After polishing with a buff roll, it was washed with water and dried.

The curable resin composition was applied to the entire surface of the dried substrate by screen printing in a direction parallel to the pattern so that the coating thickness after curing was 120 μm. After being left at 20°C for 10 minutes, the curable resin composition was thermally cured at 150°C for 60 minutes. While irradiating the substrate side of the double-sided printed circuit board with transmitted illumination, the side to which the curable resin composition was applied was observed at 20x magnification using an optical microscope (Digital Microscope VHX-6000 manufactured by Keyence Corporation), and the circuits and circuits were observed. The number of bubbles between the two was counted. The bubble release property was evaluated as follows based on the number of bubbles.

"◎": 5 or less bubbles of 100 μm or more.
"○": More than 5 bubbles of 100 μm or more and 10 or less.
"x": More than 10 bubbles of 100 μm or more.
"XX": The curable resin composition could not be applied to the substrate.

In addition, when the bubble release property was "XX", it was assumed that the cured product of the curable resin composition did not have the minimum characteristics, and the heat resistance and warpage described below were not evaluated.

・Polishability A substrate similar to the substrate on which the bubble release properties were evaluated was prepared, and one surface of the substrate was subjected to CZ roughening at an etching rate of 1.0 μm using CZ-8101B (manufactured by MEC Co., Ltd.) as a chemical solution. After the chemical treatment, it was washed with water and dried. The curable resin composition was applied to the entire surface of the dried substrate by screen printing in a direction parallel to the pattern so that the coating thickness after curing was 120 μm. Thereafter, the applied curable resin composition was thermally cured by heating the substrate coated with the curable resin composition at 150° C. for 60 minutes. Thereafter, the substrate composition was applied and the cured surface was polished to remove the cured material on the copper circuit. The cured product was polished using a buffing machine (manufactured by Ishii Johaku Co., Ltd.) using a high-cut buff #320 (manufactured by Sumitomo 3M Co., Ltd.) until the copper surface of the copper circuit was exposed, thereby producing an evaluation board.

Then, the cross sections of the center and both ends of the evaluation board were observed using an optical microscope, and the thickness of the copper circuit at these three points was measured. The polishability was evaluated as follows based on the difference in thickness.

"○": The difference in thickness is less than 30 μm.
“×”: The difference in thickness is 30 μm or more.

- Heat Resistance A substrate similar to the substrate on which the bubble removal performance was evaluated was prepared, and one surface of the substrate was pretreated by polishing with a buff roll, then washed with water and dried. The curable resin composition was applied to the entire surface of the dried substrate by screen printing in a direction parallel to the pattern so that the coating thickness after curing was 120 μm. After thermosetting the curable resin composition at 150° C. for 30 minutes, the resulting printed circuit board (ie, evaluation board) was left to warm to room temperature and was subjected to the following treatments.

First, an evaluation board coated with rosin-based flux was immersed in a solder bath preset at 260°C, and after cleaning the flux with denatured alcohol, the cured resin layer was visually observed for swelling and peeling. The heat resistance was evaluated as follows.
"◎": No peeling was observed even after immersion for 30 seconds once.
"○": Slight peeling after one 30-second immersion, but no overall effect.
"x": Swelling and peeling after one 30 second immersion.
"-": Not evaluated because the bubble release property is "XX".

- Warpage A curable resin composition was applied onto a 300 mm x 150 mm copper foil with a thickness of 35 μm so that the coating thickness after curing was 100±50 μm. The curable resin composition was thermally cured at 150° C. for 60 minutes.
The copper foil on which the cured product had been formed was cut out into a piece of 70 mm x 70 mm, and placed on a predetermined flat plate. Then, each distance from the flat plate surface to each vertex of the piece was measured as the "amount of warpage" with a ruler, and evaluated as follows.

"○": The distance is less than 10 mm.
"×": Distance is 10 mm or more.
"-": Not evaluated because the bubble release property is "XX".

In the evaluation of warpage, the film thickness after curing, the curing conditions, and the cut-out area were varied, but these widths were set within a range that did not change the evaluation of warpage.

<Consideration>
Table 1 shows the results of evaluating the physical property values and characteristics of the cured products of the curable resin compositions according to the examples. Furthermore, Table 2 shows the results of evaluating the physical property values and characteristics of the cured product of the curable resin composition according to the comparative example.

In the cured product of the curable resin composition according to Comparative Example 1-7, all evaluations of polishability and warpage were "x" or "-". On the other hand, the polishability and warpage of the cured products of the curable resin compositions according to Examples 1-9 were all evaluated as "○".

That is, from the viewpoint of evaluating polishability and warping, the characteristics of the cured product of the curable resin composition are that the stress is 0.5 N or more and less than 1.3 N, and the storage modulus at 30° C. is less than 8.8 GPa. It was confirmed that the viscosity is preferably 200 dPa·s or more and 3000 dPa·s or less.

Note that the curable resin compositions according to Examples 1-8 are solvent-free. Therefore, it is considered that bubbles (that is, voids) are difficult to generate in the first place, and the performance as a filling material is excellent.

Next, the heat resistance of the cured product of the curable resin composition according to Examples 1-9 was "◎" or "○", and the glass transition temperature was 120° C. or higher. Therefore, it can be said that a printed wiring board using a cured product having such a glass transition temperature has excellent heat resistance.

Furthermore, as shown in Table 1, in addition to the liquid epoxy resin having a bisphenol skeleton, Examples 1-4 and 6-9 used a polybutadiene epoxy resin. It was found that warping of the cured product could be suppressed compared to Comparative Example 1 in which no polybutadiene epoxy resin was added.

In addition, from the viewpoint of bubble release properties, it was confirmed that the viscosity of the curable resin composition is preferably 300 dPa·s or more and 1200 dPa·s or less.

Although the embodiments for carrying out the present invention have been specifically described above, the present invention is not limited thereto and can be modified in various ways without departing from the gist thereof.

Claims (4)

A curable resin composition,
The curable resin composition is
(A) liquid epoxy resin having a bisphenol skeleton;
(B) a curing agent;
(C) an inorganic filler, and
(D) Polybutadiene epoxy resin
including;
The blending amount of the component (D) is 5 to 40% by mass, in terms of solid content, based on the total amount of epoxy resin contained in the curable resin composition,
The curable resin composition has a viscosity of 200 dPa at a 30 second value measured at 25° C. and a rotor rotational speed of 5.0 rpm using a cone-plate rotational viscometer in accordance with JIS-Z8803:2011. s or more and 3000 dPa/s or less, and the cured product of the curable resin composition has the following characteristics (1) to (2):
(1) Initial measurement using a viscoelasticity measurement device (RSA-G2 manufactured by TA Instruments) at a temperature of 25 to 300°C, a heating rate of 5°C/min, a loading gap of 10mm, a frequency of 1Hz, and an Axial Force of 0.05N. In measuring the storage modulus of a 5±0.3 mm x 50±5 mm piece of the cured product of the curable composition under the following conditions, the stress value obtained by subtracting the minimum value from the maximum value of Axial force was 0.5N . or more and less than 1.3N;
(2) Storage modulus at 30°C is less than 8.8 GPa. The curable resin composition according to claim 1, wherein the cured product has the following property (3):
(3) Glass transition temperature is 120°C or higher. A cured product obtained by curing the curable resin composition according to claim 1 or 2 . A printed wiring board comprising the cured product according to claim 3 .