KR20210025003A - Conductive paste for vacuum printing - Google Patents

Abstract

The following conductive paste for vacuum printing is provided. In this conductive paste for vacuum printing, the solvent is less likely to be volatilized in a reduced pressure atmosphere during vacuum printing, the increase in the viscosity of the conductive paste is suppressed, and the printability in vacuum printing can be maintained satisfactorily. In addition, during heat curing, the solvent is sufficiently volatilized, and excellent adhesion to the object to be printed is exhibited. The conductive paste for vacuum printing contains (A) a conductive filler, (B) a thermosetting resin, (C) a curing agent, and (D) a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C.

Description

Conductive paste for vacuum printing

The present disclosure relates to a conductive paste for vacuum printing.

In accordance with the demand for high-speed and high-functionalization of electronic devices, high-density mounting is also required for electronic devices. As a technology for realizing high-density mounting, a three-dimensional mounting technology for stacking and mounting a plurality of substrates as described below has been developed. In this technique, while forming fine grooves and through holes in the substrate, electrodes and wirings are formed in these grooves and through holes.

A conductive paste containing a conductive material and a resin is filled and cured in the fine grooves and through holes of the substrate used for the electronic component. In this regard, it is not preferable that voids remain in the cured product from the viewpoint of reliability of the electronic device. Accordingly, in order to reduce voids in the conductive paste filled in fine grooves and through holes, the following vacuum printing method is employed. In this method, a conductive paste is applied or filled on a substrate in a reduced pressure atmosphere.

In the vacuum printing method, a conductive paste or the like is applied or filled on a substrate, which is an object to be printed, using a squeegee or the like of a printing apparatus under reduced pressure or vacuum, which is lower than atmospheric pressure. Here, the atmospheric pressure is a standard atmospheric pressure of 101.325 kPa. In the present specification, vacuum printing refers to applying, attaching, or filling a paste to a printed object in a pressure atmosphere of 50 kPa or less (hereinafter, also referred to as “pressure-sensitive atmosphere” or “vacuum atmosphere”) lower than atmospheric pressure.

However, in the case of applying or filling the paste to a printed object such as a substrate by the vacuum printing method, since the atmosphere is a reduced pressure atmosphere of 50 kPa or less, the solvent in the paste is liable to volatilize. For this reason, the viscosity of the paste increases, and the printability decreases. For example, in Patent Document 1, a conductive paste for through holes or via holes is disclosed. This conductive paste may contain ketones having a low vapor pressure as a solvent. In addition, in Patent Document 2, a conductive adhesive for prolonging the tack-free time is disclosed. This conductive adhesive contains a conductive powder, an epoxy resin, and a diluent. The diluent is an organic compound having a vapor pressure at 20°C of 150 Pa (1.5 hPa) or less and a vapor pressure at 170°C of 1500 Pa (15 hPa) or less. Further, Patent Document 3 discloses an ink for forming an adhesive layer for printing for the purpose of improving the adhesion to a substrate even in a step or curved surface. This ink for forming an adhesive layer for printing contains conductive particles, a curable resin, a dispersant, and a solvent, and the vapor pressure of the solvent is less than 1.34×103 Pa (25° C.).

Japanese Unexamined Patent Publication No. 2006-147378 Japanese Unexamined Patent Publication No. 2007-197498 Japanese Patent Application Laid-Open No. 2013-175559

However, in Patent Document 1, the vapor pressure of the solvent used for the conductive paste is not specifically described, and ketones are also exemplified as the solvent. For example, the vapor pressure of acetone, one kind of ketones, at 20°C is 24×103 Pa (181 mmHg (20°C)). Therefore, in a reduced pressure atmosphere lower than atmospheric pressure, the solvent in the conductive paste volatilizes, the viscosity of the conductive paste increases, and in vacuum printing, the printability decreases.

Specifically, the vapor pressure at 20°C of the diluent contained in the conductive adhesive disclosed in Patent Document 2 is from 80 Pa (0.8 hPa) to 700 Pa (7.0 hPa). Therefore, in a pressure-sensitive atmosphere of 50 kPa or less during vacuum printing, the diluent in the conductive adhesive volatilizes, the viscosity of the conductive adhesive increases, and printability decreases.

In addition, in the printing adhesive layer-forming ink disclosed in Patent Document 3, a solvent having a vapor pressure of less than 1.34×103 Pa (25°C), specifically, γ-butyrolactone (1.5 mmHg (1.5 mmHg ( 20℃)) is being used. Therefore, under a pressure-sensitive atmosphere of 50 kPa or less during vacuum printing, the solvent in the printing adhesive layer forming ink volatilizes, the viscosity of the conductive adhesive increases, and the printability decreases.

Accordingly, one object of an aspect of the present disclosure is to provide a conductive paste for vacuum printing as described below. In this conductive paste for vacuum printing, in a reduced pressure atmosphere of 50 kPa or less at the time of vacuum printing, the solvent is less likely to volatilize, the increase in the viscosity of the conductive paste is suppressed, and the printability in vacuum printing can be maintained satisfactorily. In addition, in this conductive paste for vacuum printing, the solvent is sufficiently volatilized during heat curing, and voids are less likely to remain in fine grooves and through holes, and excellent adhesion to a printed object is exhibited.

One aspect of the means for achieving the above object is as follows. The present disclosure includes the following aspects.

[1] A conductive paste for vacuum printing according to an aspect of the present disclosure includes (A) a conductive filler, (B) a thermosetting resin, (C) a curing agent, and (D) a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C. Includes.

[2] In the conductive paste for vacuum printing described in [1], the boiling point of the solvent (D) in a pressure atmosphere of 101.325 kPa may be 180 to 290°C.

[3] The conductive paste for vacuum printing described in [1] or [2] may further contain (E) a reactive diluent.

[4] In the conductive paste for vacuum printing according to any one of [1] to [3], the (A) conductive filler is a metal powder composed of a metal selected from silver, nickel, copper, and alloys thereof, and a metal coating. At least one selected from the group consisting of conductive powder may be included.

[5] In the conductive paste for vacuum printing according to any one of [1] to [4], the (B) thermosetting resin is at least one selected from the group consisting of an epoxy resin, a (meth)acrylic resin, and a phenol resin. It may be resin.

[6] In the conductive paste for vacuum printing according to any one of [1] to [5], the (C) curing agent may be a phenol curing agent and an imidazole curing agent.

[7] In the conductive paste for vacuum printing according to any one of [1] to [6], the solvent (D) is selected from alcohols, glycol ethers, cyclic esters, glycol ether esters, and mixtures thereof. May be.

[8] In the conductive paste for vacuum printing according to any one of [1] to [7], the solvent (D) is butyl carbitol, benzyl alcohol, 2-phenoxyethanol, diethylene glycol monohexyl ether, and dimethyl phthalate. , At least one selected from the group consisting of diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate.

[9] The conductive paste for vacuum printing according to any one of [1] to [8] above may further contain an elastomer (F).

[10] The conductive paste for vacuum printing according to any one of [1] to [9] above may further contain a coupling agent (G).

[11] In the conductive paste for vacuum printing according to any one of [1] to [10], the content of the thermosetting resin (B) may be 1 to 15 parts by mass per 100 parts by mass of the (A) conductive filler.

[12] In the conductive paste for vacuum printing according to any one of [1] to [11], the content of the solvent (D) may be 1 to 30 parts by mass per 100 parts by mass of the (A) conductive filler.

According to one aspect of the present disclosure, the following conductive paste for vacuum printing is provided. In this conductive paste for vacuum printing, in a reduced pressure atmosphere of 50 kPa or less at the time of vacuum printing, the solvent is less likely to volatilize, the increase in the viscosity of the conductive paste is suppressed, and the printability in vacuum printing can be maintained satisfactorily. In addition, in this conductive paste for vacuum printing, the solvent is sufficiently volatilized during heat curing, and voids are less likely to remain in fine grooves and through holes, and excellent adhesion to a printed object is exhibited.

Hereinafter, the conductive paste for vacuum printing according to the present disclosure will be described based on the embodiment. However, the embodiment shown below is an example for embracing the technical idea of this disclosure. The technique of the present disclosure is not limited to the following conductive pastes for vacuum printing.

The conductive paste for vacuum printing according to the first embodiment of the present disclosure contains (A) a conductive filler, (B) a thermosetting resin, (C) a curing agent, and (D) a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C. .

The conductive paste for vacuum printing according to the first embodiment of the present disclosure contains (D) a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C. Therefore, in a reduced pressure atmosphere of 50 kPa or less during vacuum printing, the (D) solvent in the conductive paste is less likely to be volatilized, and an increase in the viscosity of the conductive paste is suppressed. For this reason, the said electroconductive paste can maintain printability in vacuum printing satisfactorily. The conductive paste is printed on an object to be printed and then heat-cured. During heat curing, the solvent (D) is sufficiently volatilized, so that voids are difficult to remain in the fine grooves and through holes, and excellent adhesion to the object to be printed is exhibited. Vacuum printing means printing in a reduced pressure atmosphere of 50 kPa or less lower than atmospheric pressure (standard atmospheric pressure 101.325 kPa). Specifically, the reduced pressure atmosphere refers to an atmosphere in which the pressure is 50 kPa or less, and may be, for example, a vacuum atmosphere of 0 Pa. The pressure of the atmosphere in which vacuum printing is performed may be, for example, 1 Pa or more, 5 Pa or more, or 10 Pa or more.

(A) The conductive filler imparts conductivity to the cured product after curing. (A) The conductive filler contains at least one selected from the group consisting of a metal powder made of a metal selected from the group consisting of silver, nickel, copper, and alloys thereof, and a metal coated conductive powder in order to impart good conductivity. It is desirable to do it. Examples of the metal-coated conductive powder include silver-coated nickel powder or silver-coated copper powder. The silver-coated nickel powder is preferably obtained by, for example, a silver-coated nickel powder disclosed in Japanese Patent No. 5764294 or a method for producing the same.

(A) When the conductive filler contains a metal-coated conductive powder, and the metal-coated conductive powder is at least one selected from silver-coated nickel powder and silver-coated copper powder, the amount of silver coated is 100 parts by mass in total of silver and nickel, or With respect to 100 parts by mass in total of silver and copper, it is preferably 6 to 15 parts by mass, more preferably 7 to 12 parts by mass, and still more preferably 8 to 11.5 parts by mass. The thickness of the coated silver is preferably 0.1 to 0.3 µm, more preferably 0.15 to 0.2 µm. The thickness of the coated silver can be measured by observing the cross section of the silver-coated nickel powder with a Scanning Electron Microscope (SEM).

(A) The shape of the conductive filler is not particularly limited. As the shape of the conductive filler, shapes such as a rod shape, a flake shape (a scale shape), and a spherical shape may be mentioned. (A) Regarding the size of the conductive filler, when the filler has a spherical shape, the volume average particle diameter (D50) is preferably 0.1 to 30 µm. This volume average particle diameter (D50) is a value measured by a laser diffraction scattering method using a particle diameter distribution measuring apparatus (for example, a brand name: Microtrac MT300 II, manufactured by Microtrac Bell Co., Ltd.).

(A) When the conductive filler has a spherical shape, if the volume average particle diameter (D50) of the conductive filler is 0.1 to 30 µm, for example, a conductive paste is applied to fine grooves and through holes of a printed object such as a three-dimensional mounting substrate. It is easy to apply or fill. (A) When the conductive filler has a spherical shape, the volume average particle diameter (D50) of the conductive filler is more preferably 0.2 to 20 µm, further preferably 0.5 to 15 µm.

(A) When the conductive filler has a rod shape or a flake shape, the average thickness (or short diameter) (T) measured by observation with a scanning electron microscope (SEM) is preferably 0.1 to 30 µm. Further, it is preferable that the aspect ratio (T/D50) of the average thickness (T) to the volume average particle diameter (D50) is 0.01 to 1.0. (A) When the shape of the conductive filler is a rod shape or a flake shape, when the average thickness (T) of the conductive filler is 0.1 to 30 μm and the aspect ratio (T/D50) is 0.01 to 1.0, fine grooves of the printed object And the conductive paste is easily filled in the through hole. (A) When the conductive filler has a rod shape or a flake shape, the average thickness (T) of the conductive filler is more preferably 0.2 to 20 μm, and the aspect ratio (T/D50) is more preferably 0.02 to 0.9. .

(B) The thermosetting resin imparts adhesiveness and curability to the conductive paste. (B) The thermosetting resin is excellent in adhesion to a printed object such as a three-dimensional mounting substrate. For this reason, it is preferable that the thermosetting resin is at least one resin selected from the group consisting of an epoxy resin, a (meth)acrylic resin, and a phenol resin.

(B) The epoxy resin used as the thermosetting resin is preferably liquid at room temperature in order to improve the printability of the conductive paste, but may be solid at room temperature. The epoxy resin, which is solid at room temperature, can be used as a liquid by diluting with a liquid epoxy resin or (D) a solvent or a diluent.

(B) It is preferable that the epoxy resin used as a thermosetting resin has at least one epoxy group or a glycidyl group in a molecule, and a weight average molecular weight is 370-6000. Here, the weight average molecular weight means a value measured by gel permeation chromatography (GPC) using a calibration curve using standard polystyrene.

(B) The epoxy resin used as the thermosetting resin preferably does not contain a (meth)acrylic resin having at least one epoxy group or glycidyl group in the molecule and a phenol resin having at least one epoxy group or glycidyl group in the molecule. Does not.

The epoxy resin used as the (B) thermosetting resin preferably does not contain a compound containing an epoxy group used as the (E) reactive diluent described later. Specifically, this epoxy resin does not contain a compound having an epoxy group or glycidyl group having a molecular weight or weight average molecular weight of 350 or less, preferably used as (E) a reactive diluent.

(B) As the epoxy resin used as the thermosetting resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and derivatives thereof (eg, alkylene oxide adducts), hydrogenated bisphenol A type Epoxy resin, hydrogenated bisphenol F type epoxy resin, brominated bisphenol A type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, C6-C36 alkyl glycidyl ether, alkylphenyl glycidyl ether, alkenyl Glycidyl ether type epoxy resins such as glycidyl ether, alkynyl glycidyl ether, and phenyl glycidyl ether, alkyl glycidyl esters having 6 to 36 carbon atoms, alkenyl glycidyl esters, phenyl glycidyl And glycidyl ester-type epoxy resins such as esters, and silicone epoxy resins. For these resins, one type of resin may be used alone, or two or more types of resin may be used in combination.

(B) It is preferable that the thermosetting resin is an epoxy resin from the viewpoint of adhesiveness and curability. Moreover, it is preferable that the epoxy resin is at least 1 type selected from a bisphenol A type epoxy resin and a bisphenol F type epoxy resin. In the present specification, when the resin used as the thermosetting resin has both an epoxy group or a glycidyl group and a (meth)acryloyl group in the molecule, this resin is not described as an epoxy resin but as a (meth)acrylic resin. .

(B) It is preferable that the (meth)acrylic resin used as the thermosetting resin is excellent in adhesiveness, has little thermosetting shrinkage after thermosetting, and is a liquid resin at room temperature. The (meth)acrylic resin is a compound having a (meth)acryloyl group in the molecule. By using a (meth)acrylic resin, a (meth)acryloyl group reacts to form a three-dimensional network structure. Thereby, a cured product with less thermal curing shrinkage can be obtained.

(B) As the (meth)acrylic resin used as the thermosetting resin, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (Meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth) Acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, other alkyl (meth)acrylates, cyclohexyl (meth)acrylate, tert-butyl Cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, glycidyl (meth)acrylic Rate, trimethylolpropane tri(meth)acrylate, zinc mono(meth)acrylate, zinc di(meth)acrylate, dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, neopentyl glycol (Meth)acrylate, trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 2,2,3,3,4,4-hexafluorobutyl (Meth)acrylate, perfluorooctyl(meth)acrylate, perfluorooctylethyl(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol Di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, 1,9-nonanedioldi(meth)acrylate, 1,3-butanedioldi(meth)acrylate, 1,10-decane Dioldi(meth)acrylate, tetramethylene glycol di(meth)acrylate, methoxyethyl(meth)acrylate, butoxyethyl(meth)acrylate, ethoxydiethylene glycol(meth)acrylate, methoxypolyalkyl Ene glycol mono(meth)acrylate, octoxypolyalkylene glycol mono(meth)acrylate, lauroyloxypolyalkylene glycol mono(meth)acrylate, stearyloxypolyalkylene glycol mono(meth)acrylate , Allyloxypolyalkylene glycol mono(meth)acrylate, nonylphenoxypolyalkyl Len glycol mono(meth)acrylate, di(meth)acryloyloxymethyltricyclodecane, N-(meth)acryloyloxy ethylmaleimide, N-(meth)acryloyloxyethylhexahydrophthalimide , And N-(meth)acryloyloxyethylphthalimide. As the (meth)acrylic resin, (meth) such as N,N'-methylenebis(meth)acrylamide, N,N'-ethylenebis(meth)acrylamide, and 1,2-di(meth)acrylamide ethylene glycol ) Acrylamide can also be used. As the (meth)acrylic resin, it is also possible to use vinyl compounds such as n-vinyl-2-pyrrolidone, styrene derivative, and a-methylstyrene derivative.

(B) As the (meth)acrylic resin used as the thermosetting resin, poly(meth)acrylate can be used. The poly(meth)acrylate is preferably a copolymer of (meth)acrylic acid and (meth)acrylate, or a copolymer of (meth)acrylate having a hydroxyl group and (meth)acrylate not having a polar group, and the like.

(B) As (meth)acrylic resin used as a thermosetting resin, a (meth)acrylate which has a hydroxyl group is mentioned, for example. Examples of the (meth)acrylate having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2- Hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,2-cyclohexanediol mono (meth)acrylate, 1,3-cyclo Hexanediol mono(meth)acrylate, 1,4-cyclohexanediol mono(meth)acrylate, 1,2-cyclohexanedimethanol mono(meth)acrylate, 1,3-cyclohexanedimethanol mono(meth) Acrylate, 1,4-cyclohexanedimethanol mono (meth)acrylate, 1,2-cyclohexanediethanol mono (meth)acrylate, 1,3-cyclohexanediethanol mono (meth)acrylate, 1, 4-cyclohexanediethanol mono(meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane mono(meth)acrylate, trimethylolpropanedi(meth)acrylate, penta Erythritol mono(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and neopentyl glycol mono(meth)acrylate.

Alternatively, as the (meth)acrylic resin, a (meth)acrylate or the like having a carboxyl group may be used. The (meth)acrylate having a carboxyl group is obtained by reacting the (meth)acrylate having the above hydroxyl group with a dicarboxylic acid or a derivative thereof. Examples of dicarboxylic acids usable here include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, tetra Hydrophthalic acid, hexahydrophthalic acid, and derivatives thereof.

(B) The phenolic resin used as the thermosetting resin is preferably a resol-type phenolic resin from the viewpoint of excellent adhesion and less thermosetting shrinkage after thermosetting. It is preferable that the resol-type phenol resin has a weight average molecular weight of 30000 or less. Here, the weight average molecular weight means a value measured by gel permeation chromatography (GPC) using a calibration curve using standard polystyrene. (B) The phenolic resin used as the thermosetting resin preferably does not contain a phenolic curing agent used as the (C) curing agent. (B) The phenol resin used as the thermosetting resin is preferably, specifically (C) a phenol novolak resin used as a curing agent, and an alkylate or allylated product thereof, a cresol novolak resin, a phenol aralkyl (phenylene, biphenyl). (Including a ren skeleton) resin, naphthol aralkyl resin, triphenolmethane resin, and dicyclopentadiene-type phenol resin are not included.

(C) Curing agent is used to cure (B) thermosetting resin. As the (C) curing agent, an appropriate curing agent according to the type of (B) thermosetting resin can be used. (B) When the thermosetting resin is an epoxy resin, (C) the curing agent is at least selected from the group consisting of a phenolic curing agent, an imidazole curing agent, an acid anhydride curing agent, an amine curing agent, and a carboxylic acid dihydrazide curing agent. One type of hardener can be used. (C) As a curing agent, two or more types of curing agents may be used in combination. (C) As the curing agent, from the viewpoint of adhesiveness, a phenolic curing agent is preferably used, and from the viewpoint of moisture resistance, an imidazole curing agent is preferably used. (C) As a curing agent, it is more preferable to use a phenol type curing agent and an imidazole type curing agent. (B) When the thermosetting resin is a (meth)acrylic resin, a polymerization initiator such as a thermal radical polymerization initiator can be used as the curing agent.

A phenolic curing agent refers to a monomer, an oligomer, and an overall polymer having a phenolic hydroxyl group. As a phenolic curing agent, for example, a phenol novolak resin and its alkyl or allylated product, a cresol novolak resin, a phenol aralkyl (including a phenylene or biphenylene skeleton) resin, a naphthol aralkyl resin, a tree A phenolmethane resin and a dicyclopentadiene-type phenol resin. It is preferable that the phenolic curing agent is a phenol novolak resin.

Examples of the imidazole-based curing agent include imidazole compounds. The imidazole compound is, for example, 2-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4 -Methylimidazole, 1-cyanoethyl-2-ethyl-4-imidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole. Among them, as an imidazole compound, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-imidazole, 2, 4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4- Methyl-5-hydroxymethylimidazole, and 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, and the like. The imidazole-based curing agent is also used as a curing accelerator.

As an acid anhydride-based curing agent, tetrahydro phthalic anhydride, hexahydro phthalic anhydride, methyl tetrahydro phthalic anhydride, methyl hexahydro phthalic anhydride, methyl najic anhydride, hydrogenated methyl najic anhydride, trialkyl tetrahydro phthalic anhydride, methylcyclohexene Tetracarboxylic dianhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic dianhydride, ethylene glycol bis anhydro trimellitate, glycerin bis (anhydro trimellitate) monoacetate, dode Senyl succinic anhydride, aliphatic dibasic acid polyanhydride, chlorendic anhydride, methylbutenyltetrahydrophthalic anhydride, alkylated tetrahydrophthalic anhydride, methylhymic acid anhydride, succinic anhydride substituted with an alkenyl group, and glutaric anhydride. I can.

Examples of the amine curing agent include chain aliphatic amines, cyclic aliphatic amines, aliphatic aromatic amines, and aromatic amines. Examples of the carboxylic acid dihydrazide curing agent include adipic acid dihydrazide, isophthalic acid dihydrazide, sebacic acid dihydrazide, and dodecanoic acid dihydrazide.

When (B) a (meth)acrylic resin is used as the thermosetting resin and a polymerization initiator is used as the (C) curing agent, a known polymerization initiator can be used. Specific examples of the thermal radical polymerization initiator include methyl ethyl ketone peroxide, methyl cyclohexanone peroxide, methyl acetoacetate peroxide, acetylacetone peroxide, 1,1-bis(t-butylperoxy)3,3,5 -Trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t- Butylperoxy)cyclohexane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)cyclododecane, n-butyl4, 4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)-2-methylcyclohexane, t-butylhydro Loperoxide, P-mentane hydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, t-hexylhydroperoxide, dicumylperoxide, 2,5-dimethyl-2,5-bis(t- Butylperoxy)hexane, a,a'-bis(t-butylperoxy)diisopropylbenzene, t-butylcumylperoxide, di-t-butylperoxide, 2,5-dimethyl-2,5-bis (t-butylperoxy)hexine-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, laurolyl peroxide, cinnamic acid peroxide, m-toluoyl peroxide, Benzoyl peroxide, diisopropylperoxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-3-methoxybutylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, di-sec- Butylperoxydicarbonate, di(3-methyl-3-methoxybutyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, a,a'-bis(neodecanoylperoxy)diiso Propylbenzene, cumylperoxyneodecanoate, 1,1,3,3,-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylper Oxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylper Oxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylper Oxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, t-butylperoxylaurate, t-butyl Peroxy-3,5,5-trimethylhexanoate, t-butylperoxy isopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, 2,5-dimethyl-2,5-bis (benzoyl Peroxy)hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxy-m-toluoylbenzoate, t-butylperoxybenzoate, bis(t-butylperoxy)iso Phthalate, t-butylperoxyallyl monocarbonate, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and the like. As a thermal radical polymerization initiator, one type of the compounds may be used alone, or two or more types of compounds may be used in combination.

(D) When a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C is used, in a reduced pressure atmosphere of 50 kPa or less during vacuum printing, the (D) solvent in the conductive paste is less likely to volatilize, and the viscosity of the conductive paste Is suppressed. For this reason, printability in a reduced pressure atmosphere of 50 kPa or less in which vacuum printing is performed can be maintained satisfactorily. A solvent having a vapor pressure of more than 15 Pa at 20°C is likely to volatilize in a reduced pressure atmosphere of 50 kPa or less in which vacuum printing is performed. For this reason, when this solvent is used, the viscosity of the conductive paste increases, and the printability in a reduced pressure atmosphere decreases. A solvent having a vapor pressure of less than 0.8 Pa at 20° C. is less likely to volatilize even by heat when curing the (B) thermosetting resin in the conductive paste, thereby suppressing the curing reaction of the thermosetting resin. For this reason, the adhesiveness of the electroconductive paste is deteriorated. (D) The solvent is preferably a solvent having a vapor pressure of 0.8 to 14 Pa at 20°C, and more preferably a solvent having a vapor pressure of 0.8 to 13.5 Pa at 20°C.

(D) The solvent having a vapor pressure of 0.8 to 15 Pa at 20°C is preferably a solvent having a boiling point of 180 to 290°C in an atmospheric pressure atmosphere of 101.325 kPa, and a boiling point of 200 to 285°C at 101.325 kPa. It is more preferable that it is a solvent. (D) When the boiling point of a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C is 180 to 290°C at an atmospheric pressure (standard atmospheric pressure of 101.325 kPa), for example, the conductive paste is a printed object such as a three-dimensional mounting substrate. Even when filled in the fine grooves and through holes of (B) at the curing temperature of the thermosetting resin (D), the solvent is easily volatilized, and the adhesiveness of the conductive paste can be improved.

(D) The solvent having a vapor pressure of 0.8 to 15 Pa at 20°C is selected from alcohols, glycol ethers, cyclic esters, glycol ether esters, and mixtures thereof having a vapor pressure of 0.8 to 15 Pa at 20°C. It is desirable to be. Examples of alcohols include butyl carbitol, benzyl alcohol, and 2-phenoxyethanol. Examples of glycol ethers include diethylene glycol monohexyl ether and diethylene glycol monobutyl ether. As cyclic esters, dimethyl phthalate is mentioned. Examples of glycol ether esters include diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate. (D) Solvents with a vapor pressure of 0.8 to 15 Pa at 20°C include butyl carbitol, benzyl alcohol, 2-phenoxyethanol, diethylene glycol monohexyl ether, dimethyl phthalate, diethylene glycol monobutyl ether acetate, and diethylene glycol. It is preferably at least one selected from the group consisting of monoethyl ether acetate and 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate.

The conductive paste for vacuum printing according to the first embodiment of the present disclosure may further contain (E) a reactive diluent. (E) The reactive diluent is, for example, a compound having a functional group such as an epoxy group or a glycidyl group in the molecule. (E) It is preferable that the compound which has an epoxy group or a glycidyl group used as a reactive diluent is a compound whose molecular weight is 350 or less. (E) The reactive diluent has a viscosity higher than that of the solvent (D) having a vapor pressure of 0.8 to 15 Pa at 20°C, and the viscosity of the conductive paste can be adjusted to a viscosity suitable for printing.

(E) As a reactive diluent, 1,2-epoxy-4-(2-methyloxiranyl)-1-methylcyclohexane, 4-tert-butylphenylglycidyl ether, 1,3-bis(3-gly Cydoxypropyl)-1,1,3,3-tetramethyldisiloxane, neodecanoic acid glycidyl ester, and at least one selected from the group consisting of glycidyl ethers of mixed alcohols having 12 to 13 carbon atoms Can be lifted.

The conductive paste for vacuum printing according to the first embodiment of the present disclosure may further contain (F) an elastomer. When the conductive paste further contains (F) an elastomer, the elastic modulus and stress of the cured product after curing the conductive paste can be adjusted. For example, when the thickness of the substrate proceeds, the substrate may be warped due to shrinkage when the conductive paste filled in the fine grooves and through holes formed in the substrate is cured. When warping occurs in the substrate, the accuracy of position detection and the like when mounting the substrate is deteriorated. When the conductive paste contains the (F) elastomer, it is possible to reduce the warpage of the substrate by adjusting the elastic modulus and stress after curing. This enables high-precision three-dimensional mounting.

(F) As an elastomer, silicone rubber, urethane rubber, acrylic rubber, vinyl alkyl ether rubber, polyvinyl alcohol rubber, polyvinylpyrrolidone rubber, polyacrylamide rubber, cellulose rubber, carboxy-terminated acrylonitrile-butadiene rubber ( CTBN), natural rubber, butadiene rubber, chloroprene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), styrene-ethylene-butadiene-styrene rubber, styrene-isoprene-styrene rubber, styrene-isobutyl Synthetic acrylic rubber obtained by polymerization of monomers containing rene rubber, isoprene rubber, polyisobutylene rubber, butyl rubber, alkyl (meth)acrylate, styrene-butadiene block copolymer (SBS), styrene-ethylene/butylene -Styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), polybutadiene (PB), styrene-(ethylene-ethylene/propylene)-styrene block copolymer (SEEPS), ethylene-unsaturated carboxyl Acid copolymers (e.g., ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, etc.), ethylene-unsaturated carboxylic acid ester copolymers (e.g., ethylene-ethylacrylate copolymers, ethylene-ethylmetha) Acrylate copolymers, etc.), and at least one selected from the group consisting of modified products of carboxylic anhydride (for example, modified products of maleic anhydride). (F) As the elastomer, one type of the compounds may be used alone, or two or more types of compounds may be used in combination.

The conductive paste for vacuum printing according to the first embodiment of the present disclosure may further contain (G) a coupling agent. When the conductive paste contains (G) a coupling agent, the adhesive strength between the inorganic material and the organic material can be increased. For example, it is possible to increase the adhesive strength between the inorganic material (A) the conductive filler and the object to be printed, and the organic material (B) the thermosetting resin.

(G) As a coupling agent, a titanium coupling agent and a silane coupling agent which are titanic acid esters, such as isopropyl tristearoyl titanate, are mentioned. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent and an amino group-containing silane coupling agent. Examples of the epoxy group-containing silane coupling agent include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3- And glycidoxypropyl triethoxysilane. Examples of the amino group-containing silane coupling agent include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and N-2-(amino Ethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene) Hydrochloride salts of propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, etc. are mentioned.

The conductive paste for vacuum printing according to the first embodiment of the present disclosure may contain components other than the components (A) to (G) as necessary. Specific examples of such components include flux agents, antifoaming agents, surface modifiers, rheology modifiers, colorants, plasticizers, and dispersants.

In the conductive paste for vacuum printing according to the first embodiment of the present disclosure, (A) conductive filler, based on 100 parts by mass of the total amount of (A) conductive filler, (B) thermosetting resin, (C) curing agent, and (D) solvent. The content of is preferably 70 to 98 parts by mass, more preferably 75 to 97 parts by mass, still more preferably 78 to 96 parts by mass, and even more preferably 85 to 95 parts by mass. If the content of the conductive filler (A) in the conductive paste is 70 to 98 parts by mass with respect to the total amount of the components (A) to (D), by curing the conductive paste, a cured product having low electrical efficiency and excellent conductivity will be obtained. I can. When the conductive paste for vacuum printing contains two or more types of (A) conductive fillers, the content of (A) conductive fillers means the total amount of two or more types of (A) conductive fillers.

In the conductive paste for vacuum printing according to the first embodiment of the present disclosure, the content of the (B) thermosetting resin is preferably 1 to 15 parts by mass, more preferably 1.5 to 100 parts by mass of the (A) conductive filler. It is 12 mass parts, More preferably, it is 2-10 mass parts. If the content of the (B) thermosetting resin relative to 100 parts by mass of the (A) conductive filler in the conductive paste is 1 to 15 parts by mass, a conductive paste excellent in adhesion can be obtained. When the conductive paste for vacuum printing contains two or more (B) thermosetting resins, the content of (B) thermosetting resin means the total amount of two or more (B) thermosetting resins.

In the conductive paste for vacuum printing according to the first embodiment of the present disclosure, the content of the curing agent (C) is preferably 1 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the (A) conductive filler. It is a mass part. If the content of the (C) curing agent relative to 100 parts by mass of the (A) conductive filler in the conductive paste is 1 to 10 parts by mass, (B) a conductive paste having good reactivity with a thermosetting resin and excellent in adhesion can be obtained. . When the conductive paste for vacuum printing contains two or more types of (C) curing agents, the content of the (C) curing agent means the total amount of the two or more types of (C) curing agents. Hereinafter, when the conductive paste for vacuum printing contains two or more kinds of each component (D), (E), (F), and (G), the content of each component means the total amount of two or more kinds of each component.

In the conductive paste for vacuum printing according to the first embodiment of the present disclosure, (D) the content of the solvent in which the vapor pressure at 20°C is 0.8 to 15 Pa per 100 parts by mass of the conductive filler is preferably 1 to 30. It is a mass part, More preferably, it is 1.5 to 28 mass parts, More preferably, it is 2.0 to 25 mass parts. If the content of the (D) solvent relative to 100 parts by mass of the (A) conductive filler in the conductive paste is 1 to 30 parts by mass, the solvent is less likely to be volatilized in a reduced pressure atmosphere of 50 kPa or less in which vacuum printing is performed. For this reason, the viscosity of the conductive paste can be maintained in a range suitable for printing. As a result, printability can be maintained satisfactorily. In addition, if the content of the (D) solvent relative to 100 parts by mass of the (A) conductive filler in the conductive paste is 1 to 30 parts by mass, the solvent will be volatilized by heat when curing the (B) thermosetting resin in the conductive paste. easy. For this reason, a cured product in which voids are difficult to remain can be obtained. Thereby, a cured product having a low electrical resistivity and high adhesive strength can be obtained.

The content of the (E) reactive diluent in the conductive paste for vacuum printing according to the first embodiment of the present disclosure is preferably 1 to 10% by mass, and more preferably 1 to 10% by mass with respect to 100% by mass of the total amount of the conductive paste. It is 6% by mass. When the content of the (E) reactive diluent contained in the conductive paste is 1 to 10% by mass, the viscosity of the conductive paste can be adjusted to a viscosity suitable for printing. Thereby, even after curing, a cured product having a sufficiently low electrical resistivity and excellent in conductivity can be obtained.

The content of the elastomer (F) in the conductive paste for vacuum printing according to the first embodiment of the present disclosure is preferably 0.1 to 5% by mass, and more preferably 0.3 to 3% with respect to 100% by mass of the total amount of the conductive paste. It is mass%. When the content of the (F) elastomer contained in the conductive paste is 0.1 to 5% by mass, the elastic modulus and stress of the cured product after curing the conductive paste can be adjusted.

The content of the coupling agent (G) in the conductive paste for vacuum printing according to the first embodiment of the present disclosure is preferably 0.03 to 10 mass%, more preferably 0.04 to 100 mass% of the total amount of the conductive paste. It is 5% by mass. When the content of the coupling agent (G) contained in the conductive paste is 0.03 to 10% by mass, a conductive paste excellent in adhesion can be obtained.

The method for producing the conductive paste for vacuum printing according to the first embodiment of the present disclosure is not particularly limited. A conductive paste for vacuum printing can be prepared by mixing each component in a predetermined blend in a mixer such as a planetary stirrer, a dissolver, a bead mill, a thunderbolt, a pot mill, a three roll mill, a rotary mixer, and a twin-screw mixer. I can.

The conductive paste for vacuum printing according to the first embodiment of the present disclosure is used in a reduced pressure atmosphere of less than atmospheric pressure, more specifically, in a reduced pressure atmosphere of 50 kPa or less or a vacuum atmosphere, using a squeegee and/or a screen, to be printed, such as a substrate. After coating or filling by printing, a cured product can be obtained by heating to a predetermined temperature. The obtained cured product may be in the form of a film. The heating temperature for curing the conductive paste after printing may be 100 to 300°C, preferably 120 to 250°C, and more preferably 150 to 200°C. The heating time can be appropriately changed according to the heating temperature. The heating time can be, for example, 15 to 120 minutes, preferably 30 to 90 minutes. Heating can be done in an atmosphere of atmospheric pressure (standard atmospheric pressure 101.325 kPa). As an apparatus for heating, a well-known electric furnace, a blow dryer, a belt furnace, etc. are mentioned.

The cured product obtained by using the conductive paste for vacuum printing according to the first embodiment of the present disclosure is excellent in adhesion, has sufficient shear strength (for example, 1.0 kN/cm 2 or more), and is excellent in terms of reliability. . Further, the cured product obtained by using the conductive paste for vacuum printing according to the first embodiment of the present disclosure has a low electrical resistivity (for example, 0.8 × 10 ^-3 Ω·cm or less) and has sufficient conductivity. The conductive paste for vacuum printing according to the first embodiment of the present disclosure can be preferably used as a conductive paste for vacuum printing. Accordingly, this conductive paste for vacuum printing can be used for forming a conductive circuit on a printed circuit board and an electrode of a capacitor. In particular, this conductive paste for vacuum printing can be suitably used for bonding between components of a semiconductor device in three-dimensional mounting, and bonding of substrates and components, and the like.

Example

Hereinafter, embodiments of the present disclosure will be described more specifically using examples. The technique of the present disclosure is not limited to these embodiments.

Examples 1 to 15 and Comparative Examples 1 to 2

Conductive pastes for vacuum printing were prepared by mixing and dispersing each raw material using a three roll mill so that the blending ratios shown in Tables 1 and 2 below may be obtained. Numerical values for each composition in Tables 1 and 2 represent parts by mass. The raw materials (each component) used in the adjustment of the conductive paste are as follows.

(A) conductive filler

(A1) Silver-coated nickel powder (manufactured by Namics Co., Ltd., volume average particle diameter (D50): 5 µm). In this silver-coated nickel powder, the amount of silver was 10 parts by mass with respect to 100 parts by mass in total of silver and nickel powder (nickel purity: 99.9% by mass). This silver-coated nickel powder was produced by the production method described in Japanese Patent No. 5764294.

(A2) Flaky silver powder (trade name: FA2, manufactured by DOWA Electronics, Inc., average thickness (T): 0.3 μm, volume average particle diameter (D50): 6 μm, aspect ratio (T/D50): 0.05)

(A3) Silver-coated copper powder (trade name: atomized silver powder HWQ 5 µm, manufactured by Fukuda Metal Foil Powder Co., Ltd., volume average particle diameter (D50): 5 µm). In this silver-coated copper powder, the amount of silver was 10 parts by mass with respect to 100 parts by mass in total of silver and copper.

(B) thermosetting resin

(B1) Bisphenol F type epoxy resin and bisphenol A type epoxy resin mixture (trade name: Epiclon EXA835LV, manufactured by DIC Corporation)

(B2) Bisphenol A type epoxy resin (trade name: AER6072, manufactured by Asahi Kasei Ematerials, AER6072)

(C) hardener

(C1) novolac-type phenolic resin (trade name: Tamanol 758, manufactured by Arakawa Chemical Industry Co., Ltd.)

(C2) 1-cyanoethyl-2-undecylimidazole (trade name: Curesol C11Z-CN, manufactured by Shikoku Chemical Co., Ltd.)

(C3) 2-phenyl-4-methyl-5-hydroxymethylimidazole (trade name: Curesol 2P4MHZ-PW, manufactured by Shikoku Chemical Industry Co., Ltd.)

(D) solvent

(D1) Diethylene glycol mono-n-butyl ether acetate (manufactured by Yoneyama Pharmaceutical Co., Ltd., boiling point: 246.7°C, vapor pressure: 5.3 Pa (20°C))

(D2) Dimethylphthalate (trade name: DMP, manufactured by Daihachi Chemical Industries, Ltd., boiling point: 282°C, vapor pressure: 0.8Pa (20°C))

(D3) Diethylene glycol monohexyl ether (trade name: Kyowanol HX20, manufactured by KH Neochem, Inc., boiling point: 260°C, vapor pressure: less than 1.3Pa (<1.3Pa) (20°C)). As the vapor pressure, the value described in the catalog or safety data sheet (SDS) was described.

(D4) 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate (trade name: Texanol, manufactured by Nagase Industries, Ltd., boiling point: 255°C to 261.5°C, vapor pressure: 1.3 Pa (20°C)). As the boiling point, the values described in the catalog or safety data sheet (SDS) were described.

(D5) Butylcarbitol (manufactured by Daishin Chemical Co., Ltd., boiling point: 231°C, vapor pressure: 13 Pa (20°C))

(D6) 2-phenoxyethanol (trade name: Hisolve EPH, manufactured by Toho Chemical Co., Ltd., boiling point: 245°C, vapor pressure: 1.3Pa (20°C))

(D7) Benzyl alcohol (manufactured by Fujifilm Wako Pure Chemical Co., Ltd., boiling point: 205°C, vapor pressure: 13.2 Pa (20°C))

(D8) Diethylene glycol monoethyl ether acetate (trade name: ECA, manufactured by Daicel Chemical Industries, Ltd., boiling point: 218.5°C, vapor pressure: 13.3 Pa (20°C))

(D9) 2-(2-ethoxyethoxy)ethanol (trade name: JCT-EDG, manufactured by Japan Chemtech Co., Ltd., boiling point: 210.9°C, vapor pressure: 15.6Pa (20°C))

(D10) 1,3-butylene glycol diacetate (manufactured by Daicel Chemical Industries, Ltd., boiling point: 232°C, vapor pressure: 0.0026 Pa (20°C)). The boiling point of each solvent is the boiling point in 101.325 kPa, and the vapor pressure of each solvent is the vapor pressure in 20 degreeC.

(E) reactive diluent

(E1) 1,2-epoxy-4-(2-methyloxiranyl)-1-methylcyclohexane (trade name: Celoxide 3000, manufactured by Daicel Chemical Industries, Ltd.)

(E2) Glycidyl ether of mixed alcohol having 12 to 13 carbon atoms (trade name: Epogose EN, manufactured by Yokkaichi Synthesis Co., Ltd.)

(F) elastomer

(F1) Silicone rubber (trade name: silicone compound powder KMP-605, manufactured by Shin-Etsu Chemical Industries, Ltd.)

(F2) Carboxyl-terminated acrylonitrile-butadiene rubber (trade name: Hycar-CTBN1300×13, manufactured by Ube Hungsan Co., Ltd.)

(G) coupling agent

(G1) Silane coupling agent (3-glycidoxypropyltrimethoxysilane) (trade name: KBM-403, manufactured by Shin-Etsu Chemical Industries, Ltd.)

Volume average particle diameter (D50) by laser diffraction scattering method

By laser diffraction scattering method, using a particle diameter distribution measuring device (trade name: Microtrac MT3000 II, manufactured by Microtrac Bell Corporation), the volume average particle diameter of the conductive fillers (A1) to (A3) (median diameter: D50) Was measured. (A2) The flake-shaped silver powder was observed using a scanning electron microscope, and the average thickness (T) of 20 silver powders was measured, and the aspect ratio T/D50) was calculated.

Electrical resistivity (resistivity value)

Using a mesh screen mask having an opening of a wiring pattern of 1 mm x 71 mm, the conductive pastes of each of the Examples and Comparative Examples were applied by screen printing on an alumina substrate under atmospheric pressure (approximately 101.325 kPa of standard atmospheric pressure). A cured product was obtained by curing the applied wiring pattern at 160°C for 30 minutes. The thickness of the obtained cured product was measured using a surface roughness and contour shape integrated measuring device (trade name: Surfcom 1300SD-2, manufactured by Tokyo Precision Co., Ltd.). The electric resistance value of the obtained cured product was measured using a digital multimeter (trade name: Keithley 2001, manufactured by TFF Keithley Instruments Co., Ltd.). ^{The electrical resistivity (resistivity value) (10 -3} Ω·cm) was measured from the thickness of the cured product and the electrical resistance value. The measurement results are shown in Tables 1 and 2.

Shear strength

Using a mesh screen mask having a width of 1.5 mm × 25 openings, under atmospheric pressure (standard atmospheric pressure of about 101.325 kPa), conductive pastes of each of the Examples and Comparative Examples were applied by screen printing on an alumina substrate having a width of 20 mm. did. An alumina chip having a size of 3.2 mm x 1.5 mm was mounted in each of 10 locations among 25 block-shaped printing patterns. A test piece was obtained by curing the printed pattern on which the alumina chip was mounted at 200° C. for 30 minutes. Using a strength tester (product number: Model 1605HTP, manufactured by Aiko Engineering Co., Ltd.), the shear strength of each test piece at a weighting speed of 12 mm/min was measured. The measurement results are shown in Tables 1 and 2.

Viscosity change rate by vacuum printing

Using a vacuum printer (product number: LS-100VC, manufactured by Neuron Precision Industries, Ltd.), the conductive pastes of each of the Examples and Comparative Examples were screen-printed over 1000 times on an alumina substrate in a reduced pressure atmosphere of 50 kPa or less. The viscosity of the conductive pastes of Examples and Comparative Examples before screen printing and the viscosity of the conductive pastes of Examples and Comparative Examples after 1000 screen printing were measured using a Brookfield viscometer (product number: HBDV-1, manufactured by Brookfield Corporation). , It measured at 10 rpm using a No. 14 rotor at 25 degreeC. As shown in the following equation (1), the viscosity before printing was subtracted from the viscosity after printing, and the ratio of the value divided by the viscosity before printing was measured as the rate of change in viscosity by vacuum printing. The measurement results are shown in Tables 1 and 2.

In the conductive paste of Example 1, the viscosity before printing was 156 Pa·s, the viscosity after printing was 171 Pa·s, and the viscosity change rate by vacuum printing was 10%. In the conductive paste of Example 2, the viscosity before printing was 468 Pa·s, the viscosity after printing was 540 Pa·s, and the viscosity change rate by vacuum printing was 15%. In the conductive paste of Example 3, the viscosity before printing was 12 Pa·s, the viscosity after printing was 14 Pa·s, and the viscosity change rate by vacuum printing was 17%.

(1) Viscosity change rate (%) = [Viscosity of conductive paste after printing (Pa·s)-viscosity of conductive paste before printing (Pa·s)] ÷ viscosity of conductive paste before printing (Pa·s)×100

As shown in Tables 1 and 2, in the conductive pastes of Examples 1 to 15 containing a solvent (D) having a vapor pressure of 0.8 to 15 Pa at 20°C, vacuum printing in a reduced pressure atmosphere of 50 kPa or less was performed. The rate of change in viscosity is less than 20%. For this reason, even in a reduced pressure atmosphere of 50 kPa or less at the time of performing vacuum printing, the solvent is less likely to be volatilized, and an increase in the viscosity of the conductive paste is suppressed. Thereby, printability in vacuum printing can be maintained satisfactorily.

In addition, in the conductive pastes of Examples 1 to 15, the shear strength is 1.0 kN/cm 2 or more, and the solvent is sufficiently volatilized at the time of heat curing. For this reason, these electroconductive pastes are excellent in adhesion to the object to be printed. In addition, in the conductive pastes of Examples 1 to 15, the electrical resistivity after curing is 1.0 × 10 ^-3 Ω·cm or less, more specifically 0.8 × 10 ^-3 Ω·cm or less. That is, the cured product of these conductive pastes has low electrical resistivity and excellent conductivity.

On the other hand, as shown in Tables 1 and 2, in the conductive paste of Comparative Example 1 containing a solvent having a vapor pressure of 15 Pa or more at 20°C, the viscosity change rate by vacuum printing in a reduced pressure atmosphere of 50 kPa or less was 20%. It is large enough to exceed For this reason, in a reduced pressure atmosphere of 50 kPa or less when performing vacuum printing, the solvent volatilizes, the viscosity increases, and the printability in vacuum printing is deteriorated.

In addition, as shown in Tables 1 and 2, in the conductive paste of Comparative Example 2 containing a solvent having a vapor pressure of less than 0.8 Pa at 20°C, the shear strength is as low as less than 1.0 kN/cm 2. For this reason, the solvent does not volatilize even by heat at the time of curing and remains in the cured product, and the adhesiveness of the obtained cured product is deteriorated. In the conductive paste of Comparative Example 2 containing a solvent having a vapor pressure of less than 0.8 Pa at 20°C, the solvent does not volatilize even by heat during curing and remains in the cured product. For this reason, the electrical resistivity of the conductive paste of Comparative Example 2 is 0.9×10 ⁻³ Ω·cm, which is higher than that of the example, and the conductivity of the conductive paste of Comparative Example 2 is also lowered.

The conductive paste according to the first embodiment of the present disclosure can be preferably used as a conductive paste for vacuum printing. Further, this conductive paste can be used for formation of a conductive circuit on a printed circuit board and an electrode of a capacitor. In particular, the conductive paste according to the first embodiment of the present disclosure can be preferably used for bonding between semiconductor device components and substrates and components in three-dimensional mounting.

Claims (12)

A conductive paste for vacuum printing containing (A) a conductive filler, (B) a thermosetting resin, (C) a curing agent, and (D) a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C. The method of claim 1,
The conductive paste for vacuum printing of the above (D) solvent having a boiling point of 180 to 290°C in a pressure atmosphere of 101.325 kPa. The method according to claim 1 or 2,
Further (E) a conductive paste for vacuum printing containing a reactive diluent. The method according to any one of claims 1 to 3,
A conductive paste for vacuum printing, wherein the (A) conductive filler contains at least one selected from the group consisting of a metal powder made of a metal selected from the group consisting of silver, nickel, copper, and alloys thereof, and a metal-coated conductive powder. The method according to any one of claims 1 to 4,
The (B) thermosetting resin is at least one resin selected from the group consisting of an epoxy resin, a (meth)acrylic resin, and a phenol resin. The method according to any one of claims 1 to 5,
The (C) curing agent is a phenol-based curing agent and an imidazole-based curing agent, a conductive paste for vacuum printing. The method according to any one of claims 1 to 6,
The conductive paste for vacuum printing in which the solvent (D) is selected from alcohols, glycol ethers, cyclic esters, glycol ether esters, and mixtures thereof. The method according to any one of claims 1 to 7,
The solvent (D) is butyl carbitol, benzyl alcohol, 2-phenoxyethanol, diethylene glycol monohexyl ether, dimethyl phthalate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and 2,2, Conductive paste for vacuum printing, which is at least one selected from the group consisting of 4-trimethyl-1,3-pentadiol monoisobutyrate. The method according to any one of claims 1 to 8,
Further (F) a conductive paste for vacuum printing containing an elastomer. The method according to any one of claims 1 to 9,
Further (G) a conductive paste for vacuum printing containing a coupling agent. The method according to any one of claims 1 to 10,
The conductive paste for vacuum printing in which the content of the (B) thermosetting resin is 1 to 15 parts by mass per 100 parts by mass of the (A) conductive filler. The method according to any one of claims 1 to 11,
The conductive paste for vacuum printing in which the content of the solvent (D) is 1 to 30 parts by mass based on 100 parts by mass of the (A) conductive filler.