TW202000809A - Vacuum-printing conductive paste - Google Patents

Abstract

Provided is a vacuum-printing conductive paste as described below. With a vacuum-printing conductive paste according to the present invention, in a reduced-pressure atmosphere during vacuum printing, a solvent is not easily volatilized, and an increase in the viscosity of the conductive paste is suppressed, thus making it possible to maintain favorable printing performance during vacuum printing. Furthermore, during heating and curing, the solvent is sufficiently volatilized, achieving excellent adhesiveness to a printed material. The vacuum-printing conductive paste contains (A) a conductive filler, (B) a thermosetting resin, (C) a curing agent, and (D) a solvent having a vapor pressure of 0.8-15 Pa at 20 DEG C.

Description

Conductive paste for vacuum printing

This case is about a conductive paste for vacuum printing.

With the requirement of high speed and high performance of electronic equipment, electronic devices also require high-density installation. As a technology for realizing high-density mounting, someone has developed a three-dimensional mounting technology for laminating and mounting multiple substrates as follows. In this technique, fine grooves and through holes are provided in the substrate, and electrodes and wiring are provided in the grooves and through holes at the same time. The fine grooves and through holes of the substrate for electronic parts are filled with a conductive paste containing a conductive material and resin and hardened. Regarding this, from the viewpoint of reliability of electronic equipment, it is less desirable to leave voids in the hardened material. Therefore, in order to reduce voids filled in the conductive paste of the fine grooves and through holes, the following vacuum printing method is adopted. In this method, the conductive paste is applied or filled on the substrate under a reduced pressure environment.

In the vacuum printing method, the substrate to be printed is coated or filled with a conductive paste under reduced pressure or vacuum under a pressure lower than atmospheric pressure using a doctor blade of a printing device. Here, the atmospheric pressure is the standard atmospheric pressure of 101.325 kPa. "Vacuum printing" in this manual refers to coating, filling, or applying paste to the printed matter under a pressure environment below 50 kPa below atmospheric pressure (hereinafter also referred to as "decompression environment" or "vacuum environment"). The material is attached to the printed matter.

However, when applying or filling a paste with a vacuum printing method on a printed object such as a substrate, the solvent in the paste is easily volatilized due to the reduced-pressure environment where the environment is 50 kPa or less. Therefore, the viscosity of the paste will increase, resulting in poor printability. For example, Patent Document 1 discloses a conductive paste for through holes or through holes. The conductive paste may also contain ketones with a low vapor pressure as a solvent. In addition, Patent Document 2 discloses a conductive adhesive for increasing the viscosity-free time. The conductive adhesive includes conductive powder, epoxy resin and 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. In addition, Patent Document 3 discloses an ink for forming an adhesive layer for printing, the purpose of which is to improve the adhesion to a substrate even with a step or a curved surface. The ink layer forming ink for printing contains conductive particles, a curable resin, a dispersant, and a solvent, and the vapor pressure of the solvent is less than 1.34×10 ³ Pa (25° C.). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2006-147378 [Patent Document 2] Japanese Patent Laid-Open No. 2007-197498 [Patent Document 2] Japanese Patent Laid-Open No. 2013-175559

[Problems to be solved by the invention]

However, Patent Document 1 does not specifically describe the vapor pressure of the solvent used for the conductive paste, and ketones are also exemplified as the solvent. For example, acetone, a ketone, has a vapor pressure of 24×10 ³ Pa (181 mmHg (20°C)) at 20°C. Therefore, in a reduced-pressure environment below atmospheric pressure, the solvent in the conductive paste evaporates, resulting in an increase in the viscosity of the conductive paste, and the printability deteriorates in vacuum printing. The vapor pressure of the diluent contained in the conductive adhesive disclosed in Patent Document 2 at 20°C is specifically 80 Pa (0.8 hPa) to 700 Pa (7.0 hPa). Therefore, under a reduced pressure environment of 50 kPa or less during vacuum printing, the diluent in the conductive adhesive will volatilize, resulting in an increase in the viscosity of the conductive adhesive and poor printability. In addition, the ink for forming an adhesive layer for printing disclosed in Patent Document 3 uses a solvent that does not reach 1.34×10 ³ Pa (25° C.), specifically, γ-butyrolactone having a vapor pressure of about 200 Pa at 20° C. (1.5 mmHg(20℃)). Therefore, under a reduced pressure environment of 50 kPa or less at the time of vacuum printing, the solvent in the ink for forming the printing agent layer evaporates, resulting in an increase in the viscosity of the conductive adhesive and deterioration in printability. Therefore, one of the purposes of the same attitude in this case is to provide a conductive paste for vacuum printing as follows. This conductive paste for vacuum printing has a low pressure environment of 50 kPa or less during vacuum printing, the solvent is not easily volatilized, and the viscosity increase of the conductive paste can be suppressed, and the printability during vacuum printing can be maintained well. In addition, this conductive paste for vacuum printing can fully evaporate the solvent during heating and curing, and the gap is not likely to remain in the fine grooves and through holes, and can exhibit excellent adhesion to the printed matter. [Means to solve the problem]

The same is true of the means used to achieve the aforementioned objectives. The case includes the following forms:

[1] The same conductive paste for vacuum printing in this case contains: (A) conductive filler; (B) thermosetting resin; (C) hardener; and (D) the vapor pressure at 20℃ is 0.8～ 15Pa solvent. [2] In the conductive paste for vacuum printing of the aforementioned [1], the boiling point of the (D) solvent under a pressure environment of 101.325 kPa is 180 to 290°C. [3] The conductive paste for vacuum printing of the aforementioned [1] or [2] may further contain (E) a reactive diluent. [4] In the conductive paste for vacuum printing according to any one of the above [1] to [3], the (A) conductive filler may further include a material selected from the group consisting of silver, nickel, copper, and the like At least one kind of metal powder composed of a group of metals formed by alloys and a group of metal coated conductive powders. [5] In the conductive paste for vacuum printing according to any one of the above [1] to [4], the (B) thermosetting resin may be selected from the group consisting of epoxy resin, (meth)acrylic resin and At least one resin in a group of phenol resins. [6] In the conductive paste for vacuum printing according to any one of the above [1] to [5], the (C) curing agent may be a phenolic curing agent and an imidazole curing agent. [7] In the conductive paste for vacuum printing according to any one of [1] to [6], the (D) solvent may also be selected from alcohols, glycol ethers, cyclic esters, and glycols Ether esters and their mixtures. [8] In the conductive paste for vacuum printing according to any one of [1] to [7], the (D) solvent may be selected from the group consisting of butyl carbitol, benzyl alcohol, and 2-phenoxy Ethanol, diethylene glycol monohexyl ether, dimethyl phthalate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate and 2,2,4-trimethyl-1 , 3-pentanediol monoisobutyrate at least one group. [9] The conductive paste for vacuum printing according to any one of the above [1] to [8] may further contain (F) an elastomer. [10] The conductive paste for vacuum printing according to any one of the above [1] to [9] may further contain (G) a coupling agent. [11] In the conductive paste for vacuum printing according to any one of the above [1] to [10], the content of the (B) thermosetting resin is also relative to 100 parts by mass of the (A) conductive filler. It can be 1 to 15 parts by mass. [12] In the conductive paste for vacuum printing according to any one of the above [1] to [11], the content of the (D) solvent may be 1 with respect to 100 parts by mass of the (A) conductive filler. ~30 parts by mass. [Effect of invention]

According to the same situation in this case, a conductive paste for vacuum printing as follows is provided. In this vacuum printing conductive paste, the solvent is not easily volatilized under a reduced pressure environment of 50 kPa or less when vacuum printing is performed, the viscosity increase of the conductive paste can be suppressed, and the printability during vacuum printing can be maintained well. In addition, this conductive paste for vacuum printing can fully evaporate the solvent during heating and curing, and the gap is not likely to remain in the fine grooves and through holes, and can exhibit excellent adhesion to the printed matter.

[Forms for carrying out the invention]

Hereinafter, the conductive paste for vacuum printing of this case will be described based on the embodiments. However, the embodiments shown below are only examples for embodying the technical ideas of this case. The technology in this case is not limited to the following conductive paste for vacuum printing.

The conductive paste for vacuum printing in the first embodiment of the present case includes: (A) conductive filler; (B) thermosetting resin; (C) hardener and (D) vapor pressure at 20°C is 0.8-15 Pa Of solvent.

The conductive paste for vacuum printing in the first embodiment of the present case contains (D) a solvent having a vapor pressure of 0.8 to 15 Pa at 20°C. Therefore, under a reduced pressure environment of 50 kPa or less when vacuum printing is performed, the aforementioned (D) solvent in the conductive paste is not easily volatilized, and the increase in the viscosity of the conductive paste can be suppressed. Therefore, the conductive paste can maintain the printability during vacuum printing satisfactorily. The aforementioned conductive paste is hardened by heating after being printed on the object to be printed. During heat curing, the (D) solvent can be sufficiently volatilized, and the voids do not easily remain in the fine grooves and through holes, and can exhibit excellent adhesion to the printed matter. Vacuum printing refers to printing under reduced pressure below 50kPa below atmospheric pressure (standard pressure 101.325 kPa). Specifically, the reduced pressure environment refers to an environment with a pressure of 50 kPa or less, and may also be a vacuum environment of 0 Pa, for example. The pressure of the environment in which vacuum printing is performed is, 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. The (A) conductive filler preferably contains metal powder selected from the group consisting of metals selected from the group consisting of silver, nickel, copper, and these alloys, and metal-coated conductive powder in order to impart good conductivity. At least one of the group. 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 based on, for example, the silver-coated nickel powder disclosed in Japanese Patent No. 5764294 or a manufacturing method thereof. When (A) 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, relative to 100 parts by mass of silver and nickel or silver and copper A total of 100 parts by mass, the coating amount of silver is preferably 6 to 15 parts by mass, more preferably 7 to 12 parts by mass, and even more preferably 8 to 11.5 parts by mass. The thickness of the coated silver is preferably 0.1 to 0.3 μm, and 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 (Scanning Electron Microscope; SEM).

(A) The shape of the conductive filler is not particularly limited. Examples of the shape of the conductive filler include rod shapes, flake shapes (scaly shapes), and spherical shapes. Regarding the size of the (A) conductive filler, when the shape of the filler is spherical, the volume average particle diameter (D50) is preferably 0.1 to 30 μm. This volume average particle diameter (D50) is a value measured using a particle size distribution measuring device (for example, trade name: Microtrac MT300II, manufactured by MicrotracBEL Co., Ltd.) according to the laser diffraction scattering method. When the (A) conductive filler is spherical, if the volume average particle diameter (D50) of the conductive filler is 0.1 to 30 μm, for example, it is easy to apply or fill a conductive paste on a substrate for three-dimensional mounting, etc. In the fine grooves and through holes of the printed matter. When the (A) conductive filler is spherical, the volume average particle diameter (D50) of the conductive filler is more preferably 0.2 to 20 μm, and still more preferably 0.5 to 15 μm. When the (A) conductive filler is rod-shaped or sheet-shaped, the average thickness (or short diameter) T measured by observation with a scanning electron microscope (SEM) is preferably 0.1 to 30 μm. Furthermore, the aspect ratio (T/D50) of the average thickness T to the volume average particle diameter D50 is preferably 0.01 to 1.0. When the shape of the (A) conductive filler is a rod shape or a sheet shape, if the average thickness of the conductive filler is T0.1 to 30 μm and the aspect ratio (T/D50) is 0.01 to 1.0, it is easy to change the conductive paste The material is filled in the fine grooves and through holes of the printed matter. When (A) the conductive filler is rod-shaped or sheet-shaped, 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 system imparts adhesiveness and curability to the conductive paste. (B) The thermosetting resin has excellent adhesion to printed matter such as a substrate for three-dimensional mounting. Therefore, the thermosetting resin is preferably at least one resin selected from the group consisting of epoxy resin, (meth)acrylic resin, and phenol resin.

The epoxy resin used as the (B) thermosetting resin is preferably a liquid at ordinary temperature in order to improve the printability of the conductive paste, but it may also be a solid at ordinary temperature. The epoxy resin which is solid at normal temperature can be used after being diluted with a liquid epoxy resin or (D) solvent or diluent and adjusted to a liquid state. The epoxy resin used as the (B) thermosetting resin preferably has at least one epoxy group or epoxypropyl group in the molecule and has a weight average molecular weight of 370 to 6000. Here, the weight average molecular weight refers to a value measured using a calibration curve using standard polystyrene according to gel permeation chromatography (GPC). The epoxy resin used as the (B) thermosetting resin preferably does not include (meth)acrylic resin having at least one epoxy group or epoxypropyl group in the molecule and has at least one epoxy group or Epoxy phenol resin. The epoxy resin used as (B) thermosetting resin preferably does not contain an epoxy group-containing compound used as a reactive diluent (E) described later. Specifically, the epoxy resin preferably does not contain a compound having an epoxy group or a glycidyl group with a molecular weight or weight average molecular weight of 350 or less used as the reactive diluent (E).

Examples of the epoxy resin used as the (B) thermosetting resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin and these derivatives (such as alkylene oxide adducts), hydrogenation Bisphenol A epoxy resin, hydrogenated bisphenol F epoxy resin, brominated bisphenol A epoxy resin, biphenyl epoxy resin, naphthalene epoxy resin, alkyl ring with 6 to 36 carbon atoms Oxypropyl ether, alkylphenyl epoxypropyl ether, alkenyl epoxypropyl ether, alkynyl epoxypropyl ether, phenyl epoxypropyl ether and other epoxypropyl ether type epoxy resin, carbon Epoxy epoxide-type epoxy resins such as alkyl epoxy propyl esters, alkenyl epoxy propyl esters, phenyl epoxy propyl esters, and polysiloxane epoxy resins having a number of 6 to 36. For these resins, one kind of resin may be used alone, or two or more kinds of resins may be used in combination. From the viewpoint of adhesiveness and curability, (B) the thermosetting resin is preferably an epoxy resin. Furthermore, the epoxy resin is preferably at least one selected from bisphenol A type epoxy resin and bisphenol F type epoxy resin. In this specification, when a resin used as a thermosetting resin has both an epoxy group, an epoxypropyl group, and a (meth)acryloyl group in the molecule, this resin is described as a (meth)acrylic resin Not epoxy resin.

The (meth)acrylic resin used as the (B) thermosetting resin is preferably a resin that is excellent in adhesiveness, has little thermosetting shrinkage after thermosetting, and is liquid at ordinary temperature. The (meth)acrylic resin-based compound has a (meth)acryloyl group in the molecule. By using (meth)acrylic resin, a (meth)acryloyl group reacts to form a three-dimensional mesh structure. Thereby, a hardened product with less thermosetting shrinkage can be obtained.

Examples of the (meth)acrylic resin used as the (B) thermosetting resin include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, (meth)acrylic acid Isobutyl ester, third butyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, Stearyl (meth)acrylate, isoamyl (meth)acrylate, isostearyl (meth)acrylate, behenate (meth)acrylate, 2-ethylhexyl (meth)acrylate, others Of alkyl (meth)acrylate, cyclohexyl (meth)acrylate, tert-butyl cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, ( Phenoxyethyl methacrylate, isobornyl (meth)acrylate, glycidyl (meth)acrylate, trimethylolpropane tri(meth)acrylate, zinc mono(meth)acrylate, dimethacrylate Zinc (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, neopentyl glycol (meth)acrylate, trifluoroethyl (meth)acrylate Ester, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 2,2,3,3,4,4-hexafluorobutyl (meth)acrylate, perfluorooctyl (meth)acrylate Ester, perfluorooctyl ethyl (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1 ,6-Hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,10-decane Alcohol di(meth)acrylate, tetramethylene glycol di(meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethyl Glycol (meth)acrylate, methoxy polyalkylene glycol mono (meth) acrylate, octoxy polyalkylene glycol mono (meth) acrylate, lauryl oxy polyalkylene glycol mono (meth) Group) acrylate, stearyl polyalkylene glycol mono (meth) acrylate, allyloxy polyalkylene glycol mono (meth) acrylate, nonylphenoxy polyalkylene glycol mono (meth) ) Acrylic acid ester, di(meth)acryloxymethyltricyclodecane, N-(meth)acryloyloxyethylmaleimide, N-(meth)acryloyloxy Ethylethyl hexahydrophthalimide and N- (meth) propenyloxyethyl phthalimide. As the (meth)acrylic resin, N,N'-methylenebis(meth)acrylamide, N,N'-ethylidenebis(meth)acrylamide and 1,2-bis (Meth)acrylamide ethylene glycol and other (meth)acrylamide. As the (meth)acrylic resin, vinyl compounds such as n-vinyl-2-pyrrolidone, styrene derivatives, and α-methylstyrene derivatives can also be used.

As the (meth)acrylic resin used as the (B) 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 copolymerization of a (meth)acrylate having a hydroxyl group and a (meth)acrylate having no polar group Things.

The (meth)acrylic resin used as the (B) thermosetting resin includes, for example, a (meth)acrylate having a hydroxyl group. Examples of (meth)acrylates having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth) Group) 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,2-cyclohexanediol mono(meth)acrylate, 1, 3-cyclohexanediol mono(meth)acrylate, 1,4-cyclohexanediol mono(meth)acrylate, 1,2-cyclohexanedimethanol mono(meth)acrylate, 1 ,3-cyclohexane dimethanol mono(meth)acrylate, 1,4-cyclohexane dimethanol mono(meth)acrylate, 1,2-cyclohexane diethanol mono(meth)acrylate, 1,3-cyclohexanediethanol mono(meth)acrylate, 1,4-cyclohexanediethanol mono(meth)acrylate, glycerol mono(meth)acrylate, glycerol di(meth)acrylic acid Ester, trimethylolpropane mono(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol mono(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth) Base) acrylate and neopentyl glycol mono (meth) acrylate. Alternatively, as the (meth)acrylic resin, (meth)acrylate having a carboxyl group or the like can be used. The (meth)acrylate having a carboxyl group can be obtained by reacting the above-mentioned (meth)acrylate having a hydroxyl group with a dicarboxylic acid or its derivative. Examples of the dicarboxylic acid that can be used here include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and maleic acid. , Fumaric acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid and derivatives thereof.

The phenol resin used as the (B) thermosetting resin is preferably a resol-type phenol resin because it has excellent adhesiveness and less thermosetting shrinkage after thermosetting. The resol-type phenol resin preferably has a weight average molecular weight of 30,000 or less. Here, the weight average molecular weight refers to a value measured using a calibration curve using standard polystyrene according to gel permeation chromatography (GPC). The phenol resin used as the (B) thermosetting resin preferably does not contain the phenol-based hardener used as the (C) hardener. Specifically, the phenol resin used as the (B) thermosetting resin preferably does not contain the phenol novolak resin and its alkylate or allyl compound used as the (C) hardener, cresol novolak resin, Phenol aralkyl (including phenylene, biphenylene skeleton) resin, naphthol aralkyl resin, triphenol methane resin, and dicyclopentadiene type phenol resin.

(C) Hardener is used to harden (B) thermosetting resin. As the (C) curing agent, an appropriate curing agent can be used according to the type of (B) thermosetting resin. When (B) the thermosetting resin is an epoxy resin, as the (C) curing agent, a phenolic curing agent, an imidazole curing agent, an anhydride curing agent, an amine curing agent, and a carboxylic acid dihydrazide can be used. At least one hardener in a group of hardeners. As for the (C) hardener, two or more hardeners may be used in combination. As the (C) hardener, from the viewpoint of adhesiveness, a phenol-based hardener is preferably used; from the viewpoint of moisture resistance, an imidazole-based hardener is preferably used. As the (C) hardener, phenol-based hardeners and imidazole-based hardeners are more preferably used. When the (B) thermosetting resin is (meth)acrylic resin, as the hardener, a polymerization initiator such as a thermal radical polymerization initiator can be used.

Phenolic hardener refers to all monomers, oligomers and polymers with phenolic hydroxyl groups. Examples of phenolic hardeners include phenol novolak resins and their alkylates or allylates, cresol novolak resins, phenol aralkyl (including phenylene and biphenylene skeletons) resins, and naphthalene. Phenol aralkyl resin, triphenol methane resin and dicyclopentadiene phenol resin. The phenolic hardener is preferably phenol novolak resin.

Examples of the imidazole-based hardener include imidazole compounds. The imidazole compound system includes, 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 the 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 etc. Imidazole-based hardeners can also be used as hardening accelerators.

Examples of the acid anhydride-based hardener include tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methyl nadic anhydride , Hydrogenated methyl nadic anhydride, trialkyl tetrahydrophthalic anhydride, methylcyclohexene tetracarboxylic dianhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid Dianhydride, ethylene glycol bis-dehydrated trimellitate, glycerol bis(dehydrated trimellitate) monoacetate, dodecenyl succinic anhydride, aliphatic dibasic acid polyanhydride, chloroacid anhydride, methyl Butenyl tetrahydrophthalic anhydride, alkylated tetrahydrophthalic anhydride, methyl humic anhydride, succinic anhydride and glutaric anhydride substituted with alkenyl, etc.

Examples of the amine-based hardener include chain aliphatic amines, cyclic aliphatic amines, aliphatic aromatic amines, and aromatic amines. Examples of carboxylic acid dihydrazide hardeners include adipic acid dihydrazide, isophthalic acid dihydrazide, sebacic acid dihydrazide, and dodecanoic acid dihydrazide.

When (meth)acrylic resin is used as (B) thermosetting resin and polymerization initiator is used as (C) hardener, as the polymerization initiator, a known one can be used. Specific examples of the thermal radical polymerization initiator include methyl ethyl ketone peroxide, methyl cyclohexanone peroxide, methyl acetoacetate peroxide, and acetone acetone peroxide. Compounds, 1,1-bis(third butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis(third hexylperoxy)cyclohexane, 1,1- Bis(third hexylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis(third butylperoxy)cyclohexane, 2,2-bis(4,4- Di-tert-butylperoxycyclohexyl)propane, 1,1-bis(tert-butylperoxy)cyclododecane, 4,4-bis(tert-butylperoxy)pentanoate Butyl ester, 2,2-bis(tert-butylperoxy)butane, 1,1-bis(tert-butylperoxy)-2-methylcyclohexane, tert-butylhydroperoxide , P-menthane hydrogen peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, third hexyl hydroperoxide, dicumyl peroxide, 2,5-dimethyl- 2,5-bis(tert-butylperoxy)hexane, α,α'-bis(tert-butylperoxy)diisopropylbenzene, tert-butylcumyl peroxide, Di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3, isobutylamide peroxide, 3,5,5-tri Methylhexyl peroxide, octyl peroxide, lauryl peroxide, cinnamic acid peroxide, m-toluoyl peroxide, benzoyl peroxide, diisopropyl peroxide Dicarbonate, bis(4-third butylcyclohexyl) peroxydicarbonate, di-3-methoxybutylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, di -Second butyl peroxydicarbonate, bis(3-methyl-3-methoxybutyl) peroxydicarbonate, di(4-third butylcyclohexyl)peroxydicarbonate, α ,α'-bis(neodecanoyl peroxy) diisopropylbenzene, cumyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate , 1-cyclohexyl-1-methylethyl peroxyneodecanoate, third hexyl peroxyneodecanoate, third butyl peroxyneodecanoate, third hexyl peroxypivalate, Third butyl peroxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexylperoxy) hexane, 1,1,3,3-tetramethyl butyrate Peroxy-2-ethylhexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, third hexylperoxy-2-ethylhexanoate , Third butyl peroxy-2-ethylhexanoate, third butyl peroxy isobutyrate, third butyl peroxy maleic acid, third butyl peroxy laurate , Third butylperoxy-3,5,5-trimethylhexanoate, third butylperoxyisopropyl monocarbonate, third butylperoxy-2-ethylhexyl mono Carbonate, 2,5-dimethyl-2,5-bis(benzyl peroxy) hexane, third butyl peroxy acetate, third hexyl peroxy benzoate, Third butyl peroxy-m-toluoyl benzoate, third butyl peroxy benzoate, bis (third butyl peroxy) m-benzene Diformate, third butylperoxy allyl monocarbonate, 3,3',4,4'-tetrakis (third butylperoxycarbonyl) benzophenone, etc. As the thermal radical polymerization initiator, one of the above compounds may be used alone, or two or more compounds may be used in combination.

When (D) a solvent with a vapor pressure of 0.8 to 15 Pa at 20°C is used, under reduced pressure of 50 kPa or less when performing vacuum printing, the (D) solvent in the conductive paste is not likely to volatilize, and conductivity can be suppressed The viscosity of the paste increases. Therefore, the printability under a reduced pressure environment of 50 kPa or less for vacuum printing can be maintained well. A solvent whose vapor pressure exceeds 20 Pa at 20°C is easily volatilized under a reduced pressure environment of 50 kPa or less under vacuum printing. Therefore, if this solvent is used, the viscosity of the conductive paste will increase, resulting in poor printability under reduced pressure. A solvent having a vapor pressure of less than 0.8 Pa at 20°C is not easily volatilized due to the heat when (B) the thermosetting resin in the conductive paste is cured, which suppresses the curing reaction of the thermosetting resin. Therefore, the adhesiveness of the conductive paste will deteriorate. (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 under an atmospheric pressure environment of 101.325 kPa, and more preferably a solvent having a boiling point of 200 to 285°C at 101.325 kPa. (D) If the boiling point of a solvent with a vapor pressure of 0.8 to 15 Pa at 20° C. at atmospheric pressure (standard pressure 101.325 kPa) is 180 to 290° C., for example, a conductive paste is filled on a printed object such as a substrate for three-dimensional mounting In the fine grooves and through holes, (D) the solvent is easily volatile at the curing temperature of (B) thermosetting resin, and the adhesion of the conductive paste can be improved.

(D) The solvent having a vapor pressure of 0.8 to 15 Pa at 20°C is preferably selected from alcohols, glycol ethers, cyclic esters, glycol ether esters and other substances having a vapor pressure of 0.8 to 15 Pa at 20°C. Wait for the mixture. 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. Examples of cyclic esters include dimethyl phthalate. Examples of glycol ether esters include diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, and 2,2,4-trimethyl-1,3-pentanediol monoiso Butyrate. (D) The solvent having a vapor pressure of 0.8 to 15 Pa at 20°C is preferably selected from the group consisting of butyl carbitol, benzyl alcohol, 2-phenoxyethanol, diethylene glycol monohexyl ether, and dimethyl phthalate Ester, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate At least one.

The conductive paste for vacuum printing in the first embodiment of the present case may further contain (E) a reactive diluent. (E) A reactive diluent is, for example, a compound having a functional group such as epoxy group or epoxypropyl group in the molecule. The compound having an epoxy group or glycidyl group used as the reactive diluent (E) is preferably a compound having a molecular weight of 350 or less. (E) The reactive diluent system has a higher viscosity than (D) the solvent 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.

As the (E) reactive diluent, there can be mentioned selected from 1,2-epoxy-4-(2-methyloxiranyl)-1-methylcyclohexane, 4-tert-butylbenzene Glycidyl ether, 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisilaxane, glycidyl neodecanoate and carbon At least one of the groups consisting of glycidyl ethers of 12 to 13 mixed alcohols.

The conductive paste for vacuum printing in the first embodiment of the present case may further contain (F) an elastomer. By further including (F) an elastomer, the conductive paste can adjust the elastic modulus and stress of the cured product after hardening the conductive paste. For example, when the substrate becomes thinner, the conductive paste filled in the fine grooves and through-holes formed in the substrate shrinks when hardened, causing the substrate to warp. Once the substrate warps, the accuracy of position detection when the substrate is mounted will deteriorate. Since the conductive paste contains (F) elastomer, the elastic modulus and stress after hardening can be adjusted to reduce the warpage of the substrate. With this, three-dimensional installation with high accuracy can be achieved.

Examples of the (F) elastomer include silicone rubber, urethane rubber, acrylic rubber, vinyl alkyl ether rubber, polyvinyl alcohol rubber, polyvinylpyrrolidone rubber, and polypropylene amide. Rubber, cellulose rubber, carboxyl terminal acrylonitrile-butadiene rubber (CTBN), natural rubber, butadiene rubber, chloroprene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber Rubber (NBR), styrene-ethylene-butadiene-styrene rubber, styrene-isoprene-styrene rubber, styrene-isobutylene rubber, isoprene rubber, polyisobutylene rubber, butyl rubber, Synthetic acrylic rubber, styrene-butadiene block copolymer (SBS), styrene-ethylene/butene-styrene block copolymer obtained by polymerizing monomers containing alkyl (meth)acrylate (SEBS), styrene-isoprene-styrene block copolymer (SIS), polybutadiene (PB), styrene-(ethylene-ethylene/propylene)-styrene block copolymer (SEEPS) ), ethylene-unsaturated carboxylic acid copolymer (for example, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, etc.), ethylene-unsaturated carboxylic acid ester copolymer (for example, ethylene-ethyl acrylate copolymer, ethylene-methacrylate At least one of the group consisting of ethyl acrylate copolymer, etc.) and these modified carboxylic anhydrides (for example, modified maleic anhydride). For the (F) elastomer, one of the above compounds may be used alone, or two or more compounds may be used in combination.

The conductive paste for vacuum printing in the first embodiment of the present case may further contain (G) a coupling agent. By including the (G) coupling agent, the conductive paste can improve the bonding strength between the inorganic material and the organic material. For example, the bonding strength between the inorganic material (A) conductive filler and the object to be printed and the organic material (B) thermosetting resin can be improved.

Examples of the (G) coupling agent include titanium coupling agents such as isopropyl ginsyl stearyl titanate and silane coupling agents. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent and an amine group-containing silane coupling agent. Examples of epoxy group-containing silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-epoxy Propoxypropylmethyl diethoxysilane and 3-glycidoxypropyltriethoxysilane etc. Examples of amine group-containing silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane and N-2-(aminoethyl)-3- Aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriamine Ethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane and N- (Vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, etc.

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

In the conductive paste for vacuum printing of the first embodiment of the present case, 100 parts by mass relative to the total amount of (A) conductive filler, (B) thermosetting resin, (C) hardener and (D) solvent, (A) The content of the conductive filler 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 still more preferably 85 to 95 parts by mass. With respect to the total amount of the components (A) to (D), if the content of the (A) conductive filler in the conductive paste is 70 to 98 parts by mass, it can be obtained by curing the conductive paste A hardened product with low electrical efficiency and excellent conductivity. When the conductive paste for vacuum printing contains two or more types of (A) conductive fillers, the content of (A) conductive fillers refers to the total amount of two or more types of (A) conductive fillers.

In the conductive paste for vacuum printing of the first embodiment of the present invention, the content of (B) thermosetting resin is preferably 1 to 15 parts by mass, more preferably 1.5, with respect to (A) 100 parts by mass of the conductive filler. ~12 parts by mass, even more preferably 2-10 parts by mass. If the content of (B) thermosetting resin in 100 parts by mass of (A) conductive filler in the conductive paste is 1 to 15 parts by mass, a conductive paste having excellent adhesiveness can be obtained. When the conductive paste for vacuum printing contains two or more types of (B) thermosetting resins, the content of (B) thermosetting resins refers to the total amount of two or more types of (B) thermosetting resins.

In the conductive paste for vacuum printing of the first embodiment of the present case, the content of (C) hardener is preferably 1 to 10 parts by mass, more preferably 2 to 5 with respect to (A) 100 parts by mass of the conductive filler. Quality parts. If the content of the (C) hardener is 1 to 10 parts by mass relative to (A) 100 parts by mass of the conductive filler in the conductive paste, good reactivity with (B) thermosetting resin can be obtained and A conductive paste with excellent adhesion. When the conductive paste for vacuum printing contains two or more kinds of (C) hardeners, the content of (C) hardener means the total amount of two or more kinds of (C) hardeners. Hereinafter, when the conductive paste for vacuum printing contains two or more components (D), (E), (F), and (G), the content of each component refers to the total amount of the two or more components.

In the conductive paste for vacuum printing according to the first embodiment of the present invention, the content of the solvent having a vapor pressure of 0.8 to 15 Pa at 20° C. is preferably 1 to 100 parts by mass of (A) conductive filler. 30 parts by mass, more preferably 1.5 to 28 parts by mass, and still more preferably 2.0 to 25 parts by mass. If the content of the (D) solvent in 100 parts by mass of the (A) conductive filler in the conductive paste is 1 to 30 parts by mass, the solvent is not easily volatilized under a reduced pressure environment of 50 kPa or less under vacuum printing. Therefore, the viscosity of the conductive paste can be maintained within a range suitable for printing. As a result, printability can be maintained well. In addition, if the content of (D) solvent is 1 to 30 parts by mass with respect to (A) 100 parts by mass of the conductive filler in the conductive paste, the (B) thermosetting property in the conductive paste The heat during resin curing makes the solvent easily volatilized. Therefore, it is possible to obtain a hardened product in which voids do not easily remain. Thereby, a hardened product with low resistivity and high strength can be obtained.

The content of the (E) reactive diluent in the conductive paste for vacuum printing in the first embodiment of the present invention is preferably 1 to 10% by mass, more preferably 1% relative to the total amount of the conductive paste of 100% by mass ~6% by mass. If 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. As a result, a cured product with excellent conductivity having extremely low resistivity even after curing can be obtained.

The content of the (F) elastomer in the conductive paste for vacuum printing according to the first embodiment of the present invention is preferably 0.1 to 5% by mass, more preferably 0.3 to 3 with respect to the total amount of the conductive paste of 100% by mass. quality%. If 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 (G) coupling agent in the conductive paste for vacuum printing in the first embodiment of the present invention is preferably 0.03 to 10% by mass, more preferably 0.04 to 5 with respect to the total amount of the conductive paste of 100% by mass quality%. If the content of the (G) coupling agent contained in the conductive paste is 0.03 to 10% by mass, a conductive paste having excellent adhesiveness can be obtained.

The method of manufacturing the conductive paste for vacuum printing in the first embodiment of the present case is not particularly limited. It can be added by pouring the ingredients into a meteor mixer, dissolver, bead mill, squeezer, ball mill, three-roll mill, rotary mixer, and twin shaft mixer at a predetermined blending amount. Mixing to produce a conductive paste for vacuum printing.

By using the conductive paste for vacuum printing according to the first embodiment of the present invention under a reduced-pressure environment of less than atmospheric pressure, more specifically, under a reduced-pressure environment or vacuum environment of 50 kPa or less, a squeegee and/or mesh is used After printing, the plate is coated or filled on a printed object such as a substrate, and then heated to a predetermined temperature to obtain a cured product. The resulting hardened product may also be in the form of a film. The heating temperature for hardening 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 may be, for example, 15 to 120 minutes, preferably 30 to 90 minutes. Heating can be carried out under atmospheric pressure (standard pressure 101.325kPa) environment. Examples of the heating device include a well-known electric furnace, air dryer, and belt furnace.

The cured product obtained by using the conductive paste for vacuum printing according to the first embodiment of the present invention has excellent adhesiveness, has sufficient shear strength (for example, 1.0 kN/cm ² or more), and is excellent in reliability. In addition, the cured product obtained by using the conductive paste for vacuum printing according to the first embodiment of the present invention 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 in the first embodiment of the present case can be suitably used as a conductive paste for vacuum printing. Therefore, this conductive paste for vacuum printing can be used to form conductive circuits on printed circuit boards, electrodes of capacitors, and the like. This conductive paste for vacuum printing is particularly suitable for joining parts of semiconductor devices, substrates, parts, etc. during three-dimensional mounting. [Example]

In the following, the embodiment will be described more specifically using examples. The technology in this case is not limited by these embodiments.

Examples 1 to 15 and Comparative Examples 1 to 2 Each raw material was mixed and dispersed using a three-roll mill to adjust the blending ratio shown in Tables 1 and 2 below, to prepare a conductive paste for vacuum printing. The numerical values related to each composition in Table 1 and Table 2 represent parts by mass. The raw materials (components) used in the preparation of the aforementioned conductive paste are as follows.

(A) conductive filler (A1) Silver-coated nickel powder (manufactured by NAMICS Corporation, volume average particle diameter D50: 5 μm). In this regard, the silver-coated nickel powder is 10 parts by mass relative to 100 parts by mass in total of silver and nickel powder (purity of nickel: 99.9% by mass). This silver-coated nickel powder is manufactured according to the manufacturing method described in Japanese Patent No. 5764294. (A2) Flake silver powder (trade name: FA2, manufactured by DOWA Electronics Materials Co., Ltd., 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 Foton Metal Foil Industry Co., Ltd., volume average particle diameter D50: 5 μm). As for the silver-coated copper powder, the amount of silver was 10 parts by mass with respect to the total of 100 parts by mass 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 epoxy resin (trade name: AER6072, manufactured by ASAHI KASEI E-materials Co., Ltd., AER6072)

(C) Hardener (C1) Novolac type phenol resin (trade name: TAMANOL 758, manufactured by Arakawa Chemical Industry Co., Ltd.) (C2) 1-cyanoethyl-2-undecylimidazole (trade name: Curezol C11Z-CN, manufactured by Shikoku Chemicals Co., Ltd.) (C3) 2-phenyl-4-methyl-5-hydroxymethylimidazole (trade name: Curezol 2P4MHZ-PW, manufactured by Shikoku Chemical Industry Co., Ltd.)

(D) Solvent (D1) Diethylene glycol mono-n-butyl ether acetate (made by Mishan Pharmaceutical Industry Co., Ltd., boiling point: 246.7°C, vapor pressure: 5.3Pa (20°C)) (D2) Dimethyl phthalate (trade name: DMP, manufactured by Da Ba Chemical Industry Co., Ltd., boiling point: 282°C, vapor pressure: 0.8 Pa (20°C)) (D3) Diethylene glycol monohexyl ether (trade name: KYOWANOL HX20, manufactured by KH Neochem Co., Ltd., boiling point: 260°C, vapor pressure: less than 1.3Pa (<1.3Pa) (20°C)). The vapor pressure is the value stated in the catalog or safety data sheet (SDS). (D4) 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (trade name: Texanol, manufactured by Nagase Industries Co., Ltd., boiling point: 255°C to 261.5°C, vapor pressure: 1.3Pa (20℃)). The boiling point is the value stated in the catalog or safety data sheet (SDS). (D5) Butyl carbitol (made by Daishin Chemical Co., Ltd., boiling point: 231°C, vapor pressure: 13Pa (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 (made by FUJIFILM Wako Pure Chemical Industries, Ltd., boiling point: 205°C, vapor pressure: 13.2Pa (20°C) (D8) Diethylene glycol monoethyl ether acetate (trade name: manufactured by ECA, DAICEL Chemical Industry Co., Ltd., boiling point: 218.5°C, vapor pressure: 13.3Pa (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-Butanediol diacetate (made by DAICEL Chemical Industry Co., Ltd., boiling point: 232°C, vapor pressure: 0.0026 Pa (20°C)). The boiling point of each solvent is the boiling point at 101.325 kPa, and the vapor pressure of each solvent is the vapor pressure at 20°C.

(E) reactive diluent (E1) 1,2-epoxy-4-(2-methyloxiranyl)-1-methylcyclohexane (trade name: CELLOXIDE 3000, manufactured by DAICEL Chemical Industry Co., Ltd.) (E2) Epoxypropyl ethers of mixed alcohols with carbon numbers 12 to 13 (trade name: EPOGOSEY EN, manufactured by Yokkaichi Synthesis Co., Ltd.)

(F) Elastomer (F1) Silicone rubber (trade name: Silicone composite powder KMP-605, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) (F2) Carboxyl-terminal acrylonitrile-butadiene rubber (trade name: Hycar-CTBN1300×13, manufactured by Ube Kosei Co., Ltd.)

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

Volume average particle diameter D50 according to laser diffraction scattering method The volume average particle size (median diameter: (A1) to (A3) of the conductive filler (A1) to (A3)) is measured by a laser diffraction scattering method using a particle size distribution measuring device (trade name: Microtrac MT3000II, manufactured by MicrotracBEL Corporation) D50). (A2) The flaky silver powder was observed using a scanning electron microscope, the average thickness T of 20 silver powders was measured, and the aspect ratio T/D50 was calculated).

Resistivity (specific resistance value) Use a screen mask with an opening of a wiring pattern of 1 mm × 71 mm, and conduct electroconductivity of each example and comparative example by screen printing at atmospheric pressure (standard air pressure of about 101.325 kPa) The sexual paste is coated on the alumina substrate. The coated wiring pattern was cured at 160°C for 30 minutes to obtain a cured product. The thickness of the obtained hardened product was measured using a surface roughness and contour shape measuring machine (trade name: Surfcom 1300SD-2, manufactured by Tokyo Precision Co., Ltd.). The resistance value of the obtained hardened product was measured using a digital multimeter (trade name: Keithley 2001, manufactured by TFF Keithley Instruments Co., Ltd.). The resistivity (specific resistance value) (10 ^-3 Ω·cm) was measured from the thickness and resistance value of the cured product. The measurement results are shown in Table 1 and Table 2.

Shear strength Using a screen mask with openings of 1.5 mm square × 25 openings, the conductive paste of each example and comparative example was applied to 20 mm square by screen printing under atmospheric pressure (standard air pressure of about 101.325 kPa). On an alumina substrate. Alumina wafers with a size of 3.2 mm×1.5 mm were mounted on 10 of each 25 block-shaped printing patterns. The printed pattern on which the alumina wafer was mounted was hardened at 200° C. for 30 minutes to obtain a test piece. Using a strength tester (model: Model1605HTP, manufactured by Aikoh 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 Table 1 and Table 2.

Viscosity change rate of vacuum printing Using a vacuum printing machine (model: LS-100VC, manufactured by NEWLONG Precision Industry Co., Ltd.), the conductive paste of each example and comparative example was screen printed on alumina with 1000 screens under a reduced pressure environment of 50 kPa or less On the substrate. The viscosity of the conductive paste of each example and comparative example before screen printing and the viscosity of the conductive paste of each example and comparative example after 1000 screen printing were made using Brookfield viscometer (model: HBDV- 1. Made by Brookfield), using a No. 14 rotor at 25°C and measuring at 10 rpm. As shown in the following formula (1), the ratio of the value obtained by subtracting the viscosity before printing and dividing the viscosity before printing by the viscosity before printing divided by the viscosity before printing was determined as the viscosity change rate of vacuum printing. The measurement results are shown in Table 1 and Table 2. For 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 of vacuum printing was 10%. For 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 of vacuum printing was 15%. For 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 of vacuum printing was 17%. (1) Viscosity change rate (%) = [Viscosity of conductive paste after printing (Pa·s)-Viscosity of conductive paste before printing (Pa·s)] ÷ Conductive paste before printing Viscosity (Pa・s)×100

As shown in Tables 1 and 2, the conductive pastes of Examples 1 to 15 containing the (D) solvent having a vapor pressure of 0.8 to 15 Pa at 20° C. are vacuum printed under a reduced pressure environment of 50 kPa or less The viscosity change rate is less than 20%. Therefore, under a reduced pressure environment of 50 kPa or less during vacuum printing, the solvent is not easily volatilized, and the increase in viscosity of the conductive paste can be suppressed. With this, the printability during vacuum printing can be maintained well. In addition, for the conductive pastes of Examples 1 to 15, the shear strength is 1.0 kN/cm ² or more, and the solvent can be sufficiently volatilized during heat curing. Therefore, these conductive pastes have excellent adhesion to the printed matter. In addition, the conductive pastes of Examples 1 to 15 have a resistivity after curing of 1.0×10 ^-3 Ω·cm or less, more specifically 0.8×10 ^-3 Ω·cm or less. That is, the hardened products of these conductive pastes have low electrical resistivity and excellent conductivity.

On the other hand, as shown in Tables 1 and 2, the conductive paste of Comparative Example 1 including a solvent having a vapor pressure of 20 Pa or more at 20° C. has a viscosity of vacuum printing under a reduced pressure environment of 50 kPa or less. The rate of change is greater than 20%. Therefore, when the vacuum printing is performed under a reduced pressure of 50 kPa or less, the solvent volatilizes, resulting in an increase in viscosity and poor printability during vacuum printing. In addition, as shown in Tables 1 and 2, the conductive paste of Comparative Example 2 including a solvent having a vapor pressure of less than 0.8 Pa at 20°C had a shear strength of less than 1.0 kN/cm ² and was low. . Therefore, due to heat during curing, the solvent is not volatilized and remains in the cured product, resulting in poor adhesion of the resulting cured product. 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 was not volatilized due to heat during curing, and remained in the cured product. Therefore, the 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 also becomes worse. [Industry availability]

The conductive paste of the first embodiment of this case can be suitably used as a conductive paste for vacuum printing. Furthermore, this conductive paste can be used to form conductive circuits on printed circuit boards, electrodes of capacitors, and the like. The conductive paste of the first embodiment of the present invention is particularly suitable for joining parts of a semiconductor device, substrates, parts, etc. during three-dimensional mounting.

Claims (12)

A conductive paste for vacuum printing, which comprises: (A) conductive filler; (B) thermosetting resin; (C) hardener; and (D) solvent with a vapor pressure of 0.8-15 Pa at 20°C . The conductive paste for vacuum printing according to claim 1, wherein the boiling point of the aforementioned (D) solvent under a pressure environment of 101.325 kPa is 180 to 290°C. The conductive paste for vacuum printing according to claim 1 or 2 further contains (E) a reactive diluent. The conductive paste for vacuum printing according to any one of claims 1 to 3, wherein the aforementioned (A) conductive filler comprises a metal selected from the group consisting of silver, nickel, copper, and alloys thereof At least one of the formed metal powder and the metal-coated conductive powder. The conductive paste for vacuum printing according to any one of claims 1 to 4, wherein the (B) thermosetting resin is at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, and phenol resin A resin. The conductive paste for vacuum printing according to any one of claims 1 to 5, wherein the (C) curing agent is a phenolic curing agent and an imidazole curing agent. The conductive paste for vacuum printing according to any one of claims 1 to 6, wherein the aforementioned (D) solvent is selected from alcohols, glycol ethers, cyclic esters, glycol ether esters and the like mixture. The conductive paste for vacuum printing according to any one of claims 1 to 7, wherein the aforementioned (D) solvent is selected from the group consisting of butyl carbitol, benzyl alcohol, 2-phenoxyethanol, and diethylene glycol monohexane Ether, dimethyl phthalate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate and 2,2,4-trimethyl-1,3-pentanediol monoiso At least one of the groups of butyrate. The conductive paste for vacuum printing according to any one of claims 1 to 8, further comprising (F) an elastomer. The conductive paste for vacuum printing according to any one of claims 1 to 9, which further contains (G) a coupling agent. The conductive paste for vacuum printing according to any one of claims 1 to 10, wherein the content of the (B) thermosetting resin is 1 to 15 parts by mass relative to 100 parts by mass of the (A) conductive filler. The conductive paste for vacuum printing according to any one of claims 1 to 11, wherein the content of the (D) solvent is 1 to 30 parts by mass with respect to 100 parts by mass of the (A) conductive filler.