Conductive resin composition

Abstract

To provide a conductive resin composition that enables formation of a conductive film, which has low volume resistivity and good conductivity, excellent adhesion to various base materials, good film hardness and flexibility, excellent solder suitability such as solder wettability and solder corrosion property, reduced short circuit failures by elution metal ions and excellent migration property, is excellent in storage stability, facilitates manufacture, does not contain a lead component, and is useful as conductive ink and a circuit connection material.SOLUTION: A conductive resin composition contains (a) silver coat copper powder, (b) an epoxy resin, (c) at least one selected from an amine-based curing agent, an acid anhydride-based curing agent, a thiol-based curing agent and a phenolic curing agent as a curing agent, and (d) a solvent.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive resin composition. Further, the present invention relates to a conductive ink used when forming a circuit or the like on a substrate by printing, and a circuit connection material used when electrically connecting an electronic component to a circuit board or the like.

Background Art

[0002] As conductive resin compositions, those having various compositions are known, and are used in various applications such as forming electronic circuits and adhering electronic components, as conductive pastes, conductive inks, conductive paints, circuit connection materials, conductive adhesives, etc. For example, there is a demand for a conductive ink that is applicable to various printing methods and is useful for manufacturing a flexible plastic substrate or the like having a conductive structure such as interconnection, trace, and electrode. For example, in electronic devices such as computers and mobile phones, there is a demand for a circuit connection material for high-density mounting and high integration of various electronic components such as LED elements, semiconductor elements, and capacitors on the same circuit board.

[0003] However, the films of conventional conductive resin compositions have low adhesion to substrates such as glass and plastic films, poor solder wetting, and there is a risk of solder penetration (a phenomenon in which solder penetrates the film of the conductive resin composition) and migration (a short-circuit failure caused by eluted metal ions). In many cases, sufficient adhesive strength cannot be obtained even when adhering electronic components and circuits, so the reliability of electrical connection is low. In addition, since the surface hardness of the film of the conductive resin composition is low and the flexural resistance is low, there is a risk of disconnection or short-circuit failure during use. Furthermore, the dispersibility of the conductive powder in the conductive resin composition may be insufficient, resulting in a high volume resistivity of the film of the conductive resin composition and insufficient conductivity. Therefore, there is a demand for a conductive resin composition that has excellent film properties, suppresses the occurrence of short-circuit failures, and has high reliability of electrical connection for electronic devices in which the wiring pattern interval is narrowed due to miniaturization of components and high density of circuits.

[0004] To address these needs, Patent Documents 1 to 3 describe conductive resin compositions comprising conductive powder and resin components. However, these conductive resin compositions had shortcomings in one or more of the following areas: adhesion to plastic substrates and glass, hardness, volume resistivity, solderability such as solder wettability and solder erosion resistance, and storage stability. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-162646 [Patent Document 2] International Publication No. 2014 / 104053 [Patent Document 3] Japanese Patent Application Publication No. 10-247419 [Overview of the project] [Problems that the invention aims to solve]

[0006] Until now, no conductive resin composition was known that possessed sufficient adhesion to plastic substrates and glass, sufficient coating hardness, flexibility, and volume resistivity when formed into a coating film, excellent solderability such as solder wettability and solder erosion resistance, and storage stability, while also being free of lead components that have adverse effects on human health and the environment.

[0007] The problem that the present invention aims to solve is to provide a conductive resin composition that can form a conductive film with low volume resistivity and good conductivity, excellent adhesion to various substrates, good film hardness and flexibility, excellent solderability such as solder wettability and solder erosion resistance, excellent migration resistance with reduced short-circuit failure due to dissolved metal ions, excellent storage stability, easy to manufacture, does not contain lead components, and is useful as a conductive ink or circuit connection material. [Means for solving the problem]

[0008] The inventors of the present invention conducted diligent research to solve the above problems and, as a result, discovered that the above problems can be solved by using a conductive resin composition of a specific composition, thus completing the present invention. Specifically, the invention is as follows. Item 1: (a) Silver-coated copper powder, (b) epoxy resin, (c) At least one selected from amine-based curing agents, acid anhydride-based curing agents, thiol-based curing agents and phenol-based curing agents as a curing agent, (d) Solvent, A conductive resin composition containing [a specific component]. Item 2: The conductive resin composition according to Item 1, wherein the curing agent is at least one selected from amine-based curing agents, thiol-based curing agents, and phenol-based curing agents, which are liquid at 25°C. Item 3: The conductive resin composition according to item 1 or 2, wherein the average particle size of the silver-coated copper powder is 1 to 10 μm. Item 4: A conductive resin composition according to any one of items 1 to 3, wherein the curing agent is a phenolic curing agent that is liquid at 25°C. Item 5: A conductive resin composition according to any one of items 1 to 4, wherein the silver-coated copper powder is in the form of flakes. Item 6: The conductive resin composition according to any one of items 1 to 5, wherein the epoxy resin is liquid at 25°C and is at least one selected from bisphenol-type epoxy resins, chelate-modified epoxy resins, and dicyclopentadiene-modified epoxy resins. Item 7: A conductive ink comprising a conductive resin composition as described in any one of items 1 to 6. Item 8: Circuit connection materials, including conductive inks as described in Item 7. [Effects of the Invention]

[0009] The conductive resin composition of the present invention exhibits low volume resistivity and good conductivity, has excellent adhesion to various substrates, good film hardness and flexibility, excellent solderability such as solder wettability and solder erosion resistance, can form a conductive film with excellent migration resistance that reduces short-circuit failures due to dissolved metal ions, has excellent storage stability, is easy to manufacture, does not contain lead components, and is useful as a conductive ink, circuit connection material, etc. The conductive resin composition of the present invention is useful as a printed electronics material and is extremely useful in the mass production of various electronic devices and electronic components such as display devices, vehicle-related parts, IoT devices, mobile communication systems, and sensors. [Modes for carrying out the invention]

[0010] The present invention relates to a conductive resin composition, a conductive ink, and a circuit connection material. These will be described in detail below.

[0011] [Conductive resin composition] The conductive resin composition of the present invention comprises (a) silver-coated copper powder, (b) epoxy resin, (c) at least one curing agent selected from amine-based curing agents, acid anhydride-based curing agents, thiol-based curing agents, and phenol-based curing agents, and (d) a solvent.

[0012] <Silver-coated copper powder> Silver-coated copper powder is not particularly limited as long as the surface of the copper powder is coated with silver. By silver-coating the copper powder, excellent oxidation resistance can be achieved, the volume resistivity can be reduced, and the storage stability of the conductive resin composition can be improved. The shape of the silver-coated copper powder is not particularly limited. Flake, spherical, or dendritic forms can all be used. From the viewpoint of solderability, the flake form is preferred. For example, there are no particular limitations on the method of producing silver-coated copper powder. For instance, silver-coated copper powder produced by silver plating, silver-coated copper powder produced by a copper-silver substitution reaction, or any other type of silver-coated copper powder can be used.

[0013] The average particle diameter of the silver-coated copper powder is preferably 1 μm or more and 10 μm or less for screen printing. Here, the average particle diameter of the silver-coated copper powder in the present invention is the volume cumulative particle diameter D at 50% by volume in the cumulative volume measured by the laser diffraction scattering particle size distribution measurement method 50 is the value of. If the average particle diameter of the silver-coated copper powder is larger than 10 μm, the leveling property of the conductive paste deteriorates, and disconnection of the wiring pattern is likely to occur, making it difficult to form a narrow wiring pattern. Further, if the average particle diameter of the silver-coated copper powder is smaller than 1 μm, the core copper is exposed and copper is oxidized from this portion, and the specific resistance of the wiring pattern may increase over time. In addition, in the case of flaky silver-coated copper powder, its thickness is not particularly limited. For example, it is 0.01 μm or more, preferably 0.05 μm or more, and for example, 1.0 μm or less, preferably 0.5 μm or less.

[0014] Specific examples of the silver-coated copper powder include at least one selected from 10% Ag-coated Cu-HWQ5 μm, 10% Ag-coated FCC-2000, 10% Ag-coated FCC-115, 10% Ag-coated 2L3 (above, manufactured by Fukuda Metal Foil & Powder Co., Ltd.), 1100Y, 1100YP (above, manufactured by Mitsui Mining & Smelting Co., Ltd.), TFM-C02P, TFM-C05P, TFM-C05F, TFM-C15F (above, manufactured by Toyo Aluminum Co., Ltd.), etc.

[0015] The silver content in the silver-coated copper powder is preferably 5% by mass or more and 30% by mass or less. When the silver content is less than 5% by mass, there is a risk that the core copper is exposed, and the specific resistance of the wiring pattern may increase over time. Further, when the silver content is more than 30% by mass, the possibility of ion migration increases. The content of the silver-coated copper powder is preferably 85 to 95% by mass in the dry solid of the conductive resin composition. When the content of the silver-coated copper powder is 85% by mass or more in the dry solid of the conductive resin composition, the thermal conductivity of the obtained conductive film can be improved, and as a result, the heat dissipation property can be improved. When it is 95% by mass or less, the adhesion can be ensured.

[0016] <Epoxy resin> As the epoxy resin, any monomer, oligomer, or polymer having two or more glycidyl groups in one molecule can be used, and its molecular weight and molecular structure are not particularly limited. Examples of epoxy resins used in this embodiment include biphenyl-type epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and tetramethylbisphenol F-type epoxy resin; alkylene oxide-modified bisphenol-type resins; chelate-modified epoxy resins; stilbene-type epoxy resins; novolac-type epoxy resins such as phenol novolac-type epoxy resin and cresol novolac-type epoxy resin; polyfunctional epoxy resins such as triphenolmethane-type epoxy resin and alkyl-modified triphenolmethane-type epoxy resin; aralkyl-type epoxy resins such as phenol aralkyl-type epoxy resin having a phenylene skeleton and phenol aralkyl-type epoxy resin having a biphenylene skeleton; naphthol-type epoxy resins such as dihydroxynaphthalene-type epoxy resin and epoxy resin obtained by glycidyl etherification of a dimer of dihydroxynaphthalene; triazine nucleus-containing epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; and bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type epoxy resin. Furthermore, as epoxy resins, it is also possible to use, for example, bifunctional compounds epoxidized from compounds containing two or more glycidyl groups in one molecule, such as bisphenol compounds like bisphenol A, bisphenol F, and biphenol or their derivatives; diols having an alicyclic structure like hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, and cyclohexanediethanol or their derivatives; aliphatic diols like butanediol, hexanediol, octanediol, nonanediol, and decanediol or their derivatives; and trifunctional compounds having a trihydroxyphenylmethane skeleton or an aminophenol skeleton. The epoxy resin used as a thermosetting resin may be used alone or in combination of two or more types.

[0017] Among these, from the viewpoint of adhesion and solderability of the resulting conductive resin composition, it is preferable to include a bisphenol-type epoxy resin, a chelate-modified epoxy resin, and a dicyclopentadiene-modified epoxy resin. These may be used individually or in combination of two or more types. The epoxy resin may be liquid at room temperature (25°C) or solid. In the conductive resin composition of the present invention, it is more preferable to include a liquid epoxy resin that is liquid at room temperature (25°C) in order to more effectively improve workability, handling, and manufacturability.

[0018] The epoxy resin content is, for example, 1.0% by mass or more, preferably 1.5% by mass or more, more preferably 2.0% by mass or more, and for example, 25.0% by mass or less, preferably 20.0% by mass or less, and more preferably 17.0% by mass or less, based on the total amount of silver-coated copper powder, epoxy resin, and the curing agent described below in the conductive resin composition as 100% by mass.

[0019] <Hardening agent> As a curing agent for curing epoxy resin, at least one selected from amine-based curing agents, acid anhydride-based curing agents, thiol-based curing agents, and phenol-based curing agents can be used. From the viewpoint of more effectively improving workability, handling, and manufacturing suitability, the conductive resin composition of the present invention preferably contains a curing agent that is liquid at room temperature (25°C).

[0020] Examples of amine-based curing agents include diethylenetriamine, triethylenetetramine, diethylaminopropylamine, menthanediamine, isophoronediamine, bis[4-amino-3-methyldicyclohexyl]methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, m-xylylenediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiethyldiphenylmethane, and modified polyamines and polyamidoamines obtained by modifying these through epoxy adducts, Michael addition, Mannich reactions, etc. These may be used individually or in combination of two or more types.

[0021] Examples of acid anhydride-based curing agents include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and succinic anhydride. These may be used individually or in combination of two or more types.

[0022] Examples of phenolic curing agents include bisphenols such as bisphenol A, bisphenol B, bisphenol F, bisphenol AD, and bisphenol S; phenols such as biphenol, hydroxyphenol, and bis(4-hydroxyphenyl) ether; phenol novolacs such as 2,6-bis[(2-hydroxyphenyl)methyl]-phenol; cresol novolacs such as o-cresol novolac, m-cresol novolac, and p-cresol novolac; and alkylphenols. However, phenolic curing agents containing alkoxy are undesirable because they may degrade the properties of the conductive resin composition and its cured coating film. These may be used individually or in combination of two or more types.

[0023] Examples of thiol-based curing agents include trimethylolpropanetris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate), trimethylolpropanetris (3-mercaptobutyrate), and trimethylolethanetris (3-mercaptobutyrate). These may be used individually or in combination of two or more types. In this invention, it is preferable to include a phenolic curing agent that is liquid at room temperature (25°C).

[0024] The amount of hardener used to cure the epoxy resin is not particularly limited. For every equivalent of epoxy groups in the epoxy resin, the amount of groups that react with the epoxy groups in the curing agent (e.g., hydroxyl groups, mercapto groups, amino groups, carboxyl groups) is, for example, 0.7 equivalents or more, preferably 0.8 equivalents or more, more preferably 0.9 equivalents or more, and for example, 1.3 equivalents or less, preferably 1.2 equivalents or less, more preferably 1.1 equivalents or less, and most preferably 1.0 equivalent. If the amount is less than 0.7 equivalents per equivalent of epoxy groups, the curability of the conductive resin composition will decrease, which may result in longer curing times or poor curing of the coating film. If the amount exceeds 1.3 equivalents, poor curing of the coating film may occur due to the influence of excess unreacted curing agent, which may reduce the hardness of the coating film. Furthermore, the amount of curing agent can be, for example, 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 25 parts by mass or more, per 100 parts by mass of epoxy resin, and can be, for example, 250 parts by mass or less, preferably 200 parts by mass or less, more preferably 180 parts by mass or less. If the amount of curing agent used is less than 10 parts by mass per 100 parts by mass of epoxy resin, the curability of the conductive resin composition may decrease, and curing may take a long time. If it exceeds 250 parts by mass, the conductive resin composition may not become solid.

[0025] <Solvent> The solvent can be any one or more selected from the group consisting of water and various organic solvents. Examples of organic solvents include ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl methoxybutanol, α-terpineol, β-terpineol, hexylene glycol, benzyl alcohol, 2-phenylethyl alcohol, isopalmityl alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, etc. Alcohols; Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one), and diisobutyl ketone (2,6-dimethyl-4-heptanone); Ester solvents such as ethyl acetate, butyl acetate, diethyl phthalate, dibutyl phthalate, acetoxyethane, methyl butyrate, methyl hexanoate, methyl octanoate, methyl decanoate, 1,2-diacetoxyethane, and dibasic acid esters; Ether solvents such as tetrahydrofuran, dimethyl ether, diethyl ether, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, ethoxyethyl ether, 1,2-bis(2-diethoxy)ethane, and 1,2-bis(2-methoxyethoxy)ethane;One or more solvents selected from the group consisting of ether ester solvents such as 2-(2-butoxyethoxy)ethane acetate, methyl cellosolve acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and diethylene glycol monoethyl ether acetate; ether alcohol solvents such as 2-(2-methoxyethoxy)ethanol; hydrocarbon solvents such as benzene, toluene, xylene, n-paraffin, isoparaffin, dodecylbenzene, turpentine oil, kerosene, and diesel fuel; nitrile solvents such as acetonitrile and propionitrile; nitrogen-containing polar solvents such as dimethylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone; and silicone oil solvents.

[0026] The solvent is preferably one or more selected from the group consisting of alcohol-based solvents, ether-based solvents, ester-based solvents, ether-ester-based solvents, and ketone-based solvents. More preferably, it is one or more of ether-based solvents, ester-based solvents, and ether-ester-based solvents.

[0027] When using a solvent, the amount used is not particularly limited, and the viscosity of the conductive resin composition should be adjusted as appropriate so that it is viscous enough to be properly coated, printed, etc., onto the substrate and / or viscous enough to be properly impregnated into a porous body.

[0028] <Curing catalyst> The conductive resin composition of the present invention may, if necessary, use a conventionally known curing catalyst to accelerate the curing of the epoxy resin and curing agent. From the viewpoint of more effectively improving workability, handling, and manufacturability, the conductive resin composition of the present invention preferably contains a curing catalyst that is liquid at room temperature (25°C). Specific examples of curing catalysts include tertiary amines such as piperidine, N,N-dimethylpiperazine, triethylenediamine, benzyldimethylamine, 2-(dimethylaminomethyl)phenol, and 2,4,6-tris(dimethylaminomethyl)phenol; and imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and modified imidazole. These may be used individually or in combination of two or more types.

[0029] <Other ingredients> The conductive resin composition of the present invention may optionally contain one or more additives selected from the group consisting of resins other than epoxy resins, lead-free solder particles, organic acid compounds, pigments, fillers, antioxidants, corrosion inhibitors, surfactants, defoamers, dispersants, viscosity modifiers (thixotropy modifiers), adhesion promoters, coupling agents, anti-settling agents, surfactants, pH adjusters (amine compounds), leveling agents, ultraviolet absorbers, antioxidants, flame retardants, etc., to the extent that performance is not impaired.

[0030] <Properties of conductive resin composition> For applications as a conductive ink or circuit connection material, the conductive resin composition of the present invention is preferably in the form of a paste or liquid (varnish) at room temperature (25°C).

[0031] <Characteristics of conductive resin composition and its cured coating film> The cured coating film of the conductive resin composition of the present invention exhibits excellent conductivity. The conductivity of the cured coating film of the conductive resin composition is determined by the volume resistivity of the conductive film obtained by casting or coating the conductive resin composition onto a releaseable substrate, drying it, and then peeling it off, which is 2.0 × 10⁻⁶. -2 It is less than Ω·cm. Preferably, the volume resistivity of the conductive film is 8.0 × 10⁻⁶. -3 Less than Ω·cm, more preferably 7.0 × 10 -3It is less than Ω·cm. Here, the volume resistivity is obtained by the method described in the examples.

[0032] The cured coating film of the conductive resin composition of the present invention exhibits excellent adhesion to various substrates. Adhesion to glass substrates is evaluated by the method described in the examples. The conductive resin composition of the present invention exhibits excellent storage stability. Before and after 60 days of storage, there is no change in viscosity, such as thickening, and no precipitation occurs. The cured coating film of the conductive resin composition of the present invention exhibits excellent solderability. Solderability is evaluated by the method described in the examples. The cured coating film of the conductive resin composition of the present invention exhibits excellent flexural resistance (durability against bending, etc.). Flexural resistance is evaluated by the method described in the examples (mandrel test). The cured coating film of the conductive resin composition of the present invention exhibits excellent migration resistance, thereby reducing the occurrence of short-circuit failures. Migration resistance is evaluated by the method described in the examples. The conductive resin composition of the present invention exhibits excellent manufacturability, and a conductive resin composition free of coarse particles can be easily manufactured in a short time by simple means. Manufacturability is evaluated by the method described in the examples.

[0033] <Method for preparing conductive resin compositions> In preparing the conductive resin composition of the present invention, silver-coated copper powder, epoxy resin, and solvent are used as essential components, and additive components are added to a mixing container in any order and mixed. Then, a curing agent and, if necessary, a curing catalyst are added and stirred to produce the composition. For mixing, methods such as a ball mill, roll mill, bead mill, planetary mixer, tumbler, stirrer, agitator, mechanical homogenizer, ultrasonic homogenizer, high-pressure homogenizer, paint shaker, V-type blender, Nauter mixer, Banbury mixer, rotational mixer, kneading roll, single-screw or twin-screw extruder can be used as appropriate.

[0034] The temperature at which the conductive resin composition is prepared (the temperature at which each component is mixed) is not particularly limited. Heating may be performed as needed, for example, and the temperature can be between 10 and 40°C. The atmosphere used when preparing the conductive resin composition is not particularly limited. It can be carried out in air or under an inert atmosphere.

[0035] <Applications of conductive resin compositions> The conductive resin composition of the present invention can be used to manufacture conductive objects. The conductive object may contain other components in addition to the conductive resin composition. Examples of conductive objects include one or more selected from the group consisting of conductive inks, circuit connection materials, conductive pastes, conductive films, conductive fibers, conductive paints, conductive materials for semiconductor packages, conductive materials for microelectronic devices, antistatic materials, electromagnetic shielding materials, anisotropic conductive adhesives (such as die attachment adhesives), die attach pastes, actuators, sensors, and conductive resin molded products.

[0036] For example, conductive resin compositions can constitute conductive inks, conductive pastes, conductive paints, etc. The viscosity is not particularly limited, and depending on the application, a solvent can be added to create a low-viscosity varnish-like substance or a high-viscosity paste-like substance. For example, a conductive resin composition can be applied to various substrates by methods such as casting, dipping, bar coating, dispenser coating, roll coating, gravure coating, screen printing, flexographic printing, spray coating, spin coating, or inkjet printing, and then heated and dried at a temperature of 300°C or lower to form a conductive film. The drying atmosphere can be one or more selected from the group consisting of air, inert gas, vacuum, reduced pressure, etc. In particular, from the viewpoint of suppressing deterioration of the conductive film (prevention of oxidation of conductive powder, etc.), an inert gas atmosphere such as nitrogen or argon is preferred.

[0037] [Conductive ink] The conductive ink of the present invention can be used as is with the conductive resin composition, or a solvent can be added to achieve the required viscosity. The conductive ink of the present invention contains silver-coated copper powder, epoxy resin, a curing agent, and a solvent as essential components, and, if necessary, to the extent that it does not degrade performance, it contains one or more additive components selected from the group consisting of resins other than epoxy resin, lead-free solder particles, organic acid compounds, pigments, fillers, antioxidants, corrosion inhibitors, surfactants, defoamers, dispersants, viscosity modifiers (thixotropy modifiers), adhesion promoters, coupling agents, anti-settling agents, surfactants, pH adjusters (amine compounds), leveling agents, ultraviolet absorbers, antioxidants, flame retardants, etc.

[0038] The conductive ink is obtained by first placing the components other than the curing agent into a mixing container, then mixing them using one or more mixing machines selected from the group consisting of a ball mill, roll mill, bead mill, planetary mixer, tumbler, stirrer, agitator, mechanical homogenizer, ultrasonic homogenizer, high-pressure homogenizer, paint shaker, etc., to form a varnish-like or paste-like substance, and then adding the curing agent and stirring.

[0039] The conductive ink of the present invention can be used, for example, as a conductive ink for printing to form wiring. The printing method can be one or more selected from the group consisting of screen printing, inkjet printing, flexographic printing, gravure printing, etc. In the present invention, it is preferable to use one or more printing methods selected from the group consisting of screen printing, inkjet printing, etc., because they offer excellent printability and shape retention. Here, the mesh used during screen printing can be selected as appropriate, and it is preferable to use a mesh that does not excessively remove conductive powder from the conductive ink.

[0040] The film thickness of the coated film obtained by applying the conductive ink of the present invention can be set to an appropriate thickness depending on the application. For example, it can be 1 μm or more, preferably 2 μm or more, more preferably 5 μm or more, and for example, 100 μm or less. The conductive ink of the present invention is excellent in one or more properties selected from the group consisting of conductivity, adhesion to various substrates, storage stability, leveling (surface smoothness), printability, etc.

[0041] [Circuit connection materials] The circuit connection material of the present invention is used for conductive connections between various electronic components and circuit boards, as well as for connecting (adhering) electrical and electronic circuits to each other. The shape of the circuit connection material is not particularly limited, but it is preferably in the form of a liquid or film. The liquid circuit connection material can be obtained, for example, by using the conductive resin composition of the present invention as is, or by further mixing it with a solvent such as an organic solvent. A film-like circuit connection material can be obtained, for example, by directly casting or coating the circuit connection material of the present invention onto a release substrate to form a film, drying it to remove the solvent to form a film, and then peeling it off the release substrate. Furthermore, the film-like circuit connection material can be obtained by impregnating a nonwoven fabric or the like, forming it on a release substrate, drying it to remove the solvent, and then peeling it off the release substrate.

[0042] The electrical connection method using the circuit connection material of the present invention is not particularly limited. For example, one method involves providing the circuit connection material between an electrode of an electronic component or circuit and an electrode on a substrate facing it, and then heating and / or pressurizing it as needed to electrically connect the two electrodes and bond them together. The method for providing a circuit connection material between opposing electrodes is not particularly limited. Examples include applying a liquid circuit connection material or sandwiching a film-like circuit connection material between them. Another example is a method for making a conductive connection between a pin on an electronic component and a circuit, where a circuit connection material is provided at the base of the pin and the connection is made by butt-joining the pin.

[0043] The circuit connection material of the present invention can be used as a substantially anisotropic conductive material, and can also be used in an electrode connection method in which a circuit connection material with excellent adhesive properties is formed between opposing electrodes on a substrate, and contact between the two electrodes and adhesion between the substrates are obtained by heating and pressurizing as needed. Applicable substrates for forming the electrodes include inorganic materials such as semiconductors, glass, and ceramics, organic materials such as polyimide and polycarbonate, and various combinations of these such as glass / epoxy. Furthermore, since the circuit connection material of the present invention can form a coating film at low temperatures, conductive connections can be made even at low temperatures, such as 200°C or below. [Examples]

[0044] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%" and "parts" means "parts by mass". Furthermore, all numerical values ​​for the amount of each component in Tables 1 to 4 are in "parts" (parts by mass). The materials used in the examples and comparative examples are as follows:

[0045] Epoxy resin 1: jER828 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, liquid at room temperature (25°C)) Epoxy resin 2: EP-40015 (manufactured by ADEKA, PO-modified bisphenol type epoxy resin, liquid at room temperature (25°C)) Epoxy resin 3: EP-49-23 (manufactured by ADEKA, chelate-modified epoxy resin, liquid at room temperature (25°C)) Epoxy resin 4: EP-4088L (manufactured by ADEKA, dicyclopentadiene-modified phenol-type epoxy resin, liquid at room temperature (25°C)) Epoxy resin 5: EPICLON HP-7200 (manufactured by DIC Corporation, dicyclopentadiene-modified phenol-type epoxy resin, room temperature (25℃)) solid (Condition) Butyral resin: BH-A (manufactured by Sekisui Chemical Co., Ltd., polyvinyl butyral resin, solid at room temperature (25°C)) Phenolic resin: MWF-2620 (manufactured by Meiwa Kasei Co., Ltd., resol-based phenolic resin, liquid at room temperature (25°C))

[0046] Hardener 1: ELP83H (manufactured by Gun-ei Chemical Industry Co., Ltd., phenolic resin-based hardener, liquid at room temperature (25°C)) Hardener 2: MEH-8000H (manufactured by Meiwa Kasei Co., Ltd., phenolic resin-based hardener, liquid at room temperature (25°C)) Hardener 3: MEH-8005 (manufactured by Meiwa Kasei Co., Ltd., phenolic resin-based hardener, liquid at room temperature (25°C)) Hardener 4: KAYAHARD GPH-65 (manufactured by Nippon Kayaku Co., Ltd., phenol resin-based hardener, solid at room temperature (25°C)) Hardener 5: KAYAHARD GPH-103 (manufactured by Nippon Kayaku Co., Ltd., phenol resin-based hardener, solid at room temperature (25°C))

[0047] Curing catalyst 1: EH-2021 (manufactured by ADEKA, imidazole-based, liquid at room temperature (25°C)) Curing catalyst 2:2MZ-H (manufactured by Shikoku Chemicals Co., Ltd., 2-methylimidazole, solid at room temperature (25°C)) Curing catalyst 3: C11Z (manufactured by Shikoku Chemicals Co., Ltd., 2-undecylimidazole, solid at room temperature (25°C)) Curing catalyst 4: C17Z (manufactured by Shikoku Chemicals Co., Ltd., 2-heptadecylimidazole, solid at room temperature (25°C)) Curing catalyst 5:2P4MHZ-PW (manufactured by Shikoku Chemicals Co., Ltd., 2-phenyl-4-methyl-5-hydroxymethylimidazole, solid at room temperature (25°C))

[0048] Solvent 1: Diethylene glycol monoethyl ether acetate Solvent 2: Dipropylene glycol Solvent 3: Ethylene glycol Solvent 4: Diethylene glycol monobutyl ether (butyl carbitol) Solvent 5: Cyclohexanone (anone) Solvent 6: DBE (Dibasic Acid Ester) (Manufactured by Sankyo Chemical Co., Ltd.)

[0049] Silver-coated copper powder: TFM-C05F (manufactured by Toyo Aluminum Co., Ltd., flake form, average particle size 6.0 μm) Silver powder: AgC-A (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., flake form, average particle size 3.5-5.5 μm, surface coated with fatty acid) Copper powder 1: MS-800 (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., flake form, average particle size approximately 40 μm, surface coated with fatty acid) Copper powder 2: CH-0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., granular, average particle size 0.2 μm) Nickel powder: type 255 (manufactured by Nikko Rica Co., Ltd., filamentous form, average particle size 2.25 μm)

[0050] In the examples and comparative examples, the properties of the conductive resin composition ("conductivity," "adhesion," "film hardness," "flexibility," "solder wettability and solder erosion resistance (soldering suitability)," "migration resistance," and "manufacturability") were measured and evaluated by the methods described below. <Conductive> A conductive resin composition was applied to a glass plate by screen printing, dried at 150°C for 2 hours to create a coating with a thickness of 15-35 μm, and then peeled off the glass plate after returning to room temperature. The volume resistivity of the coating at 25°C was measured using a resistivity meter "Loresta GP-MCP T610" (manufactured by Nitto Seikou Analytech Co., Ltd.). In this invention, the volume resistivity of the coating film is 2.0 × 10⁻⁶ -2 A value less than Ω·cm is considered acceptable.

[0051] <Adhesion> A conductive resin composition was applied to a glass plate by screen printing and cured at 150°C for 2 hours to produce a coating film with a thickness of 15 to 35 μm. Afterward, the coating film was allowed to return to room temperature. Six grid-like cuts, spaced 2 mm apart and reaching the substrate, were then made in accordance with the JIS K 5600 cross-cut method. Cellophane tape (registered trademark) was then applied and peeled off, and the degree of film peeling was evaluated according to the following criteria. (Adhesion Evaluation Criteria) S: Classification 0 (The edges of the cut are perfectly smooth, and there is no peeling at any of the grid lines.) A: Classification 1 (Small peeling of the paint film at the intersection of the cuts. The affected area at the cross-cut does not clearly exceed 5%.) B: Classification 2 (The paint film is peeling along the edges of the cuts and / or at the intersections. The affected area in the cross-cut is clearly more than 5%, but not more than 15%.) C: Classification 3 (The paint film is partially or completely peeling along the edges of the cuts, and / or various parts of the grain are partially or completely peeling. The affected area in the cross-cut section is clearly more than 15% but not more than 35%.) D: Classification 4 (The paint film is partially or completely peeling along the edges of the cuts, and / or peeling in several places. The affected area in the cross-cut section does not clearly exceed 35%.) E: Classification 5 (Any type of peeling that cannot be classified as Classification 4.) In this invention, S, A, B, and C are acceptable.

[0052] <Coating film hardness> A conductive resin composition was applied to a glass plate by screen printing and cured at 150°C for 2 hours to produce a coating with a thickness of 15-35 μm. After returning to room temperature, the pencil hardness of the coating surface was measured according to JIS K5600. In this invention, a grade of HB to 10H is considered acceptable.

[0053] <Bending resistance> A conductive resin composition was applied to a PET film (100 μm thick) by screen printing, and cured at 150°C for 2 hours to prepare samples with a film thickness of 15-35 μm on one side of the PET film. The prepared samples were subjected to a mandrel test using a flexural resistance tester (Coating Tester Co., Ltd.) and evaluated according to the following criteria. The operating procedure followed JIS K 5600-5-1. (Bending resistance evaluation criteria) S: When using a mandrel with a diameter of 2 mm, no cracking of the coating or peeling of the coating from the PET film was observed. C: When using a mandrel with a diameter of 2 mm, cracking of the coating and / or peeling of the coating from the PET film were observed. In this invention, S is acceptable.

[0054] <Solder wettability and solder erosion resistance (suitability for soldering)> A conductive resin composition was applied to a glass plate by screen printing and cured at 150°C for 2 hours to create a film with a thickness of 15-35 μm. Solder paste (alloy composition: SnBi) was then applied on top of the film using a metal mask (diameter 3 mm, thickness 100 μm), and the solder was melted for 5 minutes in a heated chamber set at 150°C. The front and back surfaces of the sample were observed, and the solder wettability and solder erosion resistance were evaluated according to the following criteria. (Solder wettability evaluation criteria) S: More than 95% of the area where the solder paste was applied is wet. A: The area where the solder paste was applied is wet, with a surface area of ​​70% to less than 95% being wet. B: The area where the solder paste was applied is wet, with a coverage of 50% to less than 70% of the area. C: The area where solder paste was applied is wet, with a coverage of 30% to less than 50% of the area. D: A state in which 5% to less than 30% of the area where solder paste was applied is wet. E: Less than 5% of the area where the solder paste was applied is wet, or the solder paste is ball-shaped. In this invention, S, A, B, and C are acceptable.

[0055] (Solder corrosion resistance evaluation criteria) S: Solder erosion on the back surface is observed in an area of ​​less than 5%. A: A condition in which solder erosion on the back surface is observed in an area of ​​5% to less than 10%. B: Solder erosion on the back surface is observed in an area of ​​10% to less than 20%. C: Solder erosion on the back surface is observed in an area of ​​20% to less than 80%. D: Solder erosion on the back surface is observed over an area of ​​80% or more. In this invention, S, A, and B are acceptable.

[0056] <Migration resistance> A conductive resin composition was applied to a glass plate in a comb-like pattern (318 μm gaps) by screen printing, and cured at 150°C for 2 hours to create a film with a thickness of 15-35 μm. Deionized water was then dropped onto the film so as to cover the comb-like pattern, and a voltage (5V) was applied for 5 minutes. After removing the water droplets, the sample was observed. Migration properties were evaluated according to the following criteria. (Migration resistance evaluation criteria) S: No migration has occurred, or migration has occurred but the gap is less than 25%. A: Migration is occurring, but the gap is between 25% and 50%. B: Migration is occurring and has reached more than 50% of the gap. In this invention, S and A are acceptable.

[0057] <Manufacturing suitability> After adding all the components of the conductive resin composition, the mixture was stirred using a rotation / revolution mixer (Awatori Rentaro ARV-310P, manufactured by Thinky Co., Ltd.), and uniformity was judged visually. (Manufacturing suitability assessment criteria) S: After stirring at a rotation speed of 2000 rpm for 2 minutes, no coarse particles were observed. A: After stirring at a rotation speed of 2000 rpm for 2 minutes, coarse particles can be observed, but after stirring at a rotation speed of 2000 rpm for 5 minutes, coarse particles cannot be observed. B: After stirring at a rotation speed of 2000 rpm for 5 minutes, coarse particles can be observed.

[0058] [Example 1] 81.63 parts silver-coated copper powder, 1.70 parts epoxy resin 1, 0.56 parts epoxy resin 3, and 12.24 parts solvent 1 were mixed and stirred. Then, 3.85 parts curing agent 1 and 0.02 parts curing catalyst 1 were added and stirred to prepare a conductive resin composition. The obtained conductive resin composition was applied to a substrate to produce a conductive film. The properties of conductive resin compositions and conductive films ("conductivity," "adhesion," "film hardness," "flexural resistance," and "solder wettability and solder erosion resistance (soldering suitability)," "migration resistance," and "manufacturability") were evaluated. The results are shown in Table 1.

[0059] [Examples 2-25] Except for the components and amounts used of the conductive resin composition shown in Tables 1 to 3, a conductive resin composition was prepared in the same manner as in Example 1, and the obtained conductive resin composition was applied to a substrate to produce a conductive film. The properties of the conductive resin composition and conductive film ("conductivity," "adhesion," "film hardness," "flexibility," "solder wettability and solder erosion resistance (soldering suitability)," "migration resistance," and "manufacturability") were evaluated in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[0060] [Comparative Examples 1-4] Except for the components of the conductive resin composition and the amounts used shown in Table 4, a conductive resin composition was prepared in the same manner as in Example 1, and the obtained conductive resin composition was applied to a substrate to produce a conductive film. The properties of the conductive resin composition and conductive film ("conductivity," "adhesion," "film hardness," "flexibility," "solder wettability and solder erosion resistance (soldering suitability)," "migration resistance," and "manufacturability") were evaluated in the same manner as in Example 1. The results are shown in Table 4. In Comparative Example 3, the volume resistivity was too high to measure, and the conductivity was poor, so migration resistance was not confirmed.

[0061] [Comparative Examples 5 and 6] A conductive resin composition was prepared by mixing and stirring the amounts of silver-coated copper powder shown in Table 4, the resin shown in Table 4, and the solvent 1 shown in Table 4. The resulting conductive resin composition was then applied to a substrate to produce a conductive film. The properties of the conductive resin composition ("conductivity," "adhesion," "coating hardness," "flexural resistance," "solder wettability and solder erosion resistance (soldering suitability)," "migration resistance," and "manufacturability") were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] [Table 4]

[0066] Tables 1 to 4 show that the coating obtained from the conductive resin composition according to the present invention exhibits excellent conductivity, adhesion, coating hardness, flexibility, solder wettability, solder corrosion resistance, migration resistance, and manufacturability.

Claims

1. (a) Silver-coated copper powder, (b) epoxy resin, (c) At least one selected from amine-based curing agents, acid anhydride-based curing agents, thiol-based curing agents and phenol-based curing agents, (d) solvent, A conductive resin composition comprising, The conductive resin composition wherein the epoxy resin is liquid at 25°C and contains at least one selected from PO-modified bisphenol-type epoxy resins and dicyclopentadiene-modified epoxy resins.

2. The conductive resin composition according to claim 1, wherein the curing agent is at least one selected from amine-based curing agents, thiol-based curing agents, and phenol-based curing agents, which are liquid at 25°C.

3. The conductive resin composition according to claim 1 or 2, wherein the average particle size of the silver-coated copper powder is 1 to 10 μm.

4. The conductive resin composition according to claim 1 or 2, wherein the curing agent is a phenolic curing agent that is liquid at 25°C.

5. The conductive resin composition according to claim 1 or 2, wherein the silver-coated copper powder is in the shape of flakes.

6. A conductive ink comprising the conductive resin composition according to claim 1 or 2.

7. A circuit connection material comprising the conductive ink described in claim 6.

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