Photosensitive conductive paste, method for manufacturing substrate with conductive pattern, cured film, method for manufacturing fired body, fired body and electronic component

Abstract

To provide a photosensitive conductive paste capable of forming fine wiring which has excellent conductivity and suppresses shrinkage.SOLUTION: The photosensitive conductive paste contains a conductive powder (A), a photosensitive organic component (B), a solvent (C), a ceramic powder (D), and a glass powder (E). The glass powder (E) has a softening point of 620-850°C. The total of the ceramic powder (D) and the glass powder (E) is 0.7-5.0 pts.mass based on 100 pts.mass of the conductive powder (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photosensitive conductive paste, a method for producing a substrate having a conductive pattern, a cured film, a method for producing a fired body, a fired body, and an electronic component. [Background technology]

[0002] In recent years, with the demand for smaller and higher performance electronic components, there has been a demand for finer internal wiring and higher aspect ratios ((axial thickness of coil conductor layer) / (width of coil conductor layer) in a cross section perpendicular to the extension direction of the coil conductor layer). Inductor components include a ceramic insulator and a coil-shaped internal electrode therein. The insulator includes multiple insulating layers, and the internal electrodes are formed in a planar, wire-wound shape on the insulating layers, and these are combined to form a coil. For this reason, a photosensitive conductive paste that enables finer internal wiring has been proposed (see, for example, Patent Document 1).

[0003] Incidentally, inductor components can be manufactured in two ways: by forming internal electrodes on insulating sheets containing ceramic and resin and then stacking these sheets to form a coil; or by forming internal electrodes and insulating layers containing ceramic and resin alternately and repeatedly on insulating sheets containing ceramic and resin to form a coil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-215446 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method using a photosensitive conductive paste described in Patent Document 1, it was not possible to increase the amount of conductive particles contained in the photosensitive conductive paste in order to form fine wiring or electrodes with a high aspect ratio. This is because increasing the amount of conductive particles reduces the light transmittance of the dried film, making pattern formation difficult. On the other hand, if the amount of conductive particles is too small, shrinkage during firing increases, resulting in the problem of voids and bubbles forming between the insulating sheet and insulating layer.

[0006] The present invention aims to provide a photosensitive conductive paste for use in inductor components that can form fine wiring, suppress shrinkage, and have excellent electrical conductivity, a method for producing a substrate with a conductive pattern, a cured film, a method for producing a sintered body, a sintered body, and an electronic component. [Means for solving the problem]

[0007] The present invention provides a photosensitive conductive paste containing a conductive powder (A), a photosensitive organic component (B), a solvent (C), a ceramic powder (D), and a glass powder (E), wherein the softening point of the glass powder (E) is 620 to 850°C, and the total amount of the ceramic powder (D) and the glass powder (E) is 0.7 to 5.0 parts by mass per 100 parts by mass of the conductive powder (A). [Effects of the Invention]

[0008] According to the present invention, a photosensitive conductive paste capable of forming fine wiring, suppressing shrinkage, and having excellent conductivity, as well as a cured film, a fired body, and an electronic component can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] Mask pattern of the exposure mask. DETAILED DESCRIPTION OF THE INVENTION

[0010] The photosensitive conductive paste of the present invention contains a conductive powder (A), a photosensitive organic component (B), a solvent (C), a ceramic powder (D), and a glass powder (E), and the total amount of the ceramic powder (D) and the glass powder (E) is 0.7 to 5.0 parts by mass per 100 parts by mass of the conductive powder (A).

[0011] The conductive powder (A) melts and fuses when heated and fired, becoming a conductive inorganic sintered body. The inclusion of the photosensitive organic component (B) imparts photosensitivity to the dried film of the photosensitive conductive paste, allowing fine wiring to be formed using photolithography. The ceramic powder (D) prevents the conductive powder from breaking due to over-sintering during heating and firing, and since it remains after firing, it can suppress shrinkage of the wiring electrode. The glass powder (E) melts during firing, so it has little effect in preventing over-sintering of the conductive particles, but by remaining, it can suppress shrinkage of the wiring electrode.

[0012] In the present invention, it is important that the total amount of ceramic powder (D) and glass powder (E) is 0.7 to 5.0 parts by mass per 100 parts by mass of conductive powder (A). By setting the total amount of (D) and (E) to 0.7 parts by mass or more, a fine pattern can be formed. On the other hand, by setting the total amount of (D) and (E) to 5.0 mass% or less, the ratio of conductive powder in the wiring electrode is reduced, thereby preventing a decrease in conductivity. When ceramic alone is used, the pattern shrinks significantly during firing, resulting in voids when the wiring electrode is formed. On the other hand, when glass alone is used, the glass softens, causing over-sintering of the conductive powder, resulting in disconnection defects and making it difficult to form a fine pattern. Therefore, the present inventors have discovered that by combining ceramic powder (D) and glass powder (E), disconnection defects due to over-sintering of the conductive powder can be prevented, shrinkage can be suppressed, and a wiring electrode with excellent conductivity can be obtained. The total amount of the ceramic powder (D) and the glass powder (E) is more preferably 0.9 to 3.8 parts by mass per 100 parts by mass of the conductive powder (A).

[0013] The total amount of ceramic powder (D) and glass powder (E) per 100 parts by mass of conductive powder (A) can be determined by removing organic components by firing the photosensitive conductive paste at 850°C for 10 minutes, and then analyzing the paste using an ICP optical emission spectrometer (e.g., Hitachi High-Tech Science's "PS3520DDII"). Furthermore, if the blending amounts of each component are known, the total amount can be determined from the blending amounts.

[0014] The conductive powder (A) melts or fuses when heated and fired, thereby exhibiting conductivity. Examples of the conductive powder (A) include powders of metals such as silver, gold, copper, platinum, palladium, tin, nickel, aluminum, tungsten, molybdenum, ruthenium, chromium, titanium, and indium, as well as alloys and oxides thereof. Two or more of these may be used. Among these, silver, copper, and gold are preferred from the viewpoint of conductivity, silver and copper are more preferred from the viewpoint of cost, and silver is even more preferred from the viewpoint of stability.

[0015] The median diameter (D50) in the particle size distribution (number basis) of the conductive powder (A) is preferably 0.3 to 6.0 μm. By making the D50 of the conductive powder (A) 0.3 μm or more, it is possible to efficiently transmit the exposed light in the exposure and development step described below, and to sufficiently progress curing to the bottom, which is preferable. It is also preferable because it suppresses pattern peeling and enables the formation of a finer pattern. The D50 of the conductive powder (A) is more preferably 0.8 μm or more, and even more preferably 1.3 μm or more. On the other hand, by making the D50 of the conductive powder (A) 6.0 μm or less, it is possible to suppress rattle of the pattern after formation and enables the formation of a finer pattern, which is preferable. The D50 of the conductive powder (A) is more preferably 5.5 μm or less, and even more preferably 5.0 μm or less. The D50 of the conductive powder (A) can be measured by a laser light scattering method using a Microtrac HRA (Model No. 9320-X100; manufactured by Nikkiso Co., Ltd.).

[0016] The content of the conductive powder (A) in the photosensitive conductive paste is preferably 60 to 90% by mass, more preferably 68 to 85% by mass. By making the content of the conductive powder (A) 60% by mass or more, the probability of contact between the conductive powders (A) can be improved and pattern breakage can be suppressed in the firing step described below, which is preferable. The content of the conductive powder (A) is more preferably 68% by mass or more. On the other hand, by making the content of the conductive powder (A) 90% by mass or less, pattern peeling in the exposure and development steps can be suppressed and a finer pattern can be formed, which is preferable. The content of the conductive powder (A) is more preferably 85% by mass or less.

[0017] The content of conductive powder (A) in the photosensitive conductive paste can be determined by calcining the photosensitive conductive paste at 850°C for 10 minutes, calculating the ratio of organic to inorganic components from the change in mass before and after calcination, and then analyzing the remaining inorganic components using an ICP optical emission spectrometer (for example, the "PS3520DDII" manufactured by Hitachi High-Tech Science). Furthermore, if the blending amounts of each component are known, the content can be determined from the blending amounts.

[0018] The photosensitive organic component (B) refers to an organic component containing an alkali-soluble resin and a photosensitizer. The alkali-soluble resin refers to a resin having an alkali-soluble group. Examples of alkali-soluble groups include a carboxyl group, a phenolic hydroxyl group, a sulfonic acid group, and a thiol group. Among these, a carboxyl group is preferred because of its high solubility in an alkaline developer.

[0019] The alkali-soluble resin is preferably an acrylic resin, and more preferably a copolymer of an acrylic monomer having a carbon-carbon double bond with another monomer. Examples of the acrylic monomer having a carbon-carbon double bond include acrylates having a chain aliphatic hydrocarbon group having 1 to 18 carbon atoms, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isodecyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, allyl acrylate, lauryl acrylate, and stearyl acrylate; benzyl acrylate, phenyl acrylate, and the like. Examples of suitable copolymerizable components include acrylates having a cyclic aromatic hydrocarbon group having 6 to 10 carbon atoms, such as acrylate, 1-naphthyl acrylate, and 2-naphthyl acrylate; acrylates having a cyclic aliphatic hydrocarbon group having 6 to 15 carbon atoms, such as cyclohexyl acrylate, dicyclopentanyl acrylate, 4-tert-butylcyclohexyl acrylate, dicyclopentenyl acrylate, dicyclopentadienyl acrylate, isobornyl acrylate, and 3,3,5-trimethylcyclohexyl acrylate, as well as acrylates obtained by substituting these acrylates with methacrylates. Two or more of these may be used. Examples of copolymerizable components other than acrylic monomers include styrenes, such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, chloromethylstyrene, and hydroxymethylstyrene; unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and vinylacetic acid, as well as acid anhydrides thereof. Two or more of these may be used.

[0020] The acrylic resin preferably has a carbon-carbon double bond in the side chain or molecular terminal, which can improve the curing reaction rate during exposure. Examples of structures having a carbon-carbon double bond include a vinyl group, an allyl group, an acrylic group, and a methacrylic group. Two or more of these may be present. Methods for introducing a carbon-carbon double bond into an acrylic resin include, for example, reacting a mercapto group, an amino group, a hydroxyl group, or a carboxyl group in the acrylic resin with a compound having a glycidyl group or an isocyanate group and a carbon-carbon double bond, acrylic acid chloride, methacrylic acid chloride, allyl chloride, or the like.

[0021] Examples of compounds having a glycidyl group and a carbon-carbon double bond include glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, glycidyl ethyl acrylate, crotonyl glycidyl ether, glycidyl crotonate, glycidyl isocrotonate, Cyclomer (registered trademark) M100, A200 (all manufactured by Daicel Chemical Industries, Ltd.). Examples of compounds having an isocyanate group and a carbon-carbon double bond include acryloyl isocyanate, methacryloyl isocyanate, acryloylethyl isocyanate, methacryloylethyl isocyanate, etc. Two or more of these may be used.

[0022] Examples of the photosensitizer include a photopolymerization initiator and a dissolution inhibitor. From the viewpoint of forming a thicker conductive pattern, a photopolymerization initiator is preferred.

[0023] Photopolymerization initiators absorb short-wavelength light such as ultraviolet light and decompose, or generate radicals through a hydrogen abstraction reaction, thereby imparting photocurability and enabling pattern formation by negative photolithography. Examples of the photopolymerization initiator that decomposes upon absorbing light such as ultraviolet light include alkylphenone-based photopolymerization initiators such as 1,2-octanedione, benzophenone, methyl ortho-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4-benzoyl-4'-methyldiphenyl ketone, dibenzyl ketone, 2,2'-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, Michler's ketone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 4-azidobenzalacetophenone, 2,6-bis(p-azidobenzylidene)cyclohexanone, and 6-bis(p-azidobenzylidene)-4-methylcyclohexanone; acylphosphine oxide-based photopolymerization initiators such as phenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and oxime ester-based photopolymerization initiators such as 1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-2(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), 1-phenyl-1,2-butanedione-2-(O-methoxycarbonyl)oxime, 1-phenyl-propanedione-2-(O-ethoxycarbonyl)oxime, 1-phenyl-propanedione-2-(O-benzoyl)oxime, 1,3-diphenyl-propanetrione-2-(O-ethoxycarbonyl)oxime, and 1-phenyl-3-ethoxy-propanetrione-2-(O-benzoyl)oxime. Examples of photopolymerization initiators that generate radicals through a hydrogen abstraction reaction include benzophenone, anthraquinone, thioxanthone, phenylglyoxylic acid methyl ester, etc. Two or more of these may be contained.

[0024] The dissolution inhibitor increases the solubility of exposed areas in the developer, enabling pattern formation by positive photolithography. Dissolution inhibitors that generate acid upon exposure to light are preferred. Examples of dissolution inhibitors include diazodisulfone compounds, triphenylsulfonium compounds, and quinone diazide compounds. Examples of diazodisulfone compounds include bis(cyclohexylsulfonyl)diazomethane, bis(tertiarybutylsulfonyl)diazomethane, and bis(4-methylphenylsulfonyl)diazomethane. Examples of triphenylsulfonium compounds include diphenyl-4-methylphenylsulfonium trifluoromethanesulfonate, diphenyl-2,4,6-trimethylphenylsulfonium p-toluenesulfonate, and diphenyl(4-methoxyphenyl)sulfonium trifluoromethanesulfonate. Examples of the quinone diazide compound include a compound in which the sulfonic acid of quinone diazide is bonded to a polyhydroxy compound via an ester bond, a compound in which the sulfonic acid of quinone diazide is bonded to a polyamino compound via a sulfonamide bond, and a compound in which the sulfonic acid of quinone diazide is bonded to a polyhydroxypolyamino compound via an ester bond and / or a sulfonamide bond. Two or more of these compounds may be used.

[0025] The solvent (C) is a liquid at room temperature and wets or dissolves the components constituting the photosensitive conductive paste, making it a liquid with excellent coatability. The boiling point of the solvent (C) is preferably 180 to 300°C. By setting the boiling point to 300°C or less, it is possible to improve the binder removal property during firing. The boiling point is more preferably 230°C or less, and by setting it to 230°C or less, it is possible to easily dry it in the drying step described below. Furthermore, by setting the boiling point to 180°C or more, it is possible to suppress an increase in viscosity during the coating step. The boiling point of the solvent refers to the boiling point at 1013.25 hPa.

[0026] Examples of the solvent include ethylene glycol hexyl ether, ethylene glycol monobutyl ether acetate, diethylene glycol n-butyl ether, diethylene glycol ethyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol methyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, dipropylene glycol n-butyl ether, dipropylene glycol propyl ether, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether, dipropylene glycol methyl ether acetate, dipropylene glycol monomethyl ether, Examples of suitable ethylene glycol ether acetate include dimethyl imidazolidinone, dimethyl sulfoxide, triethylene glycol dimethyl ether, propylene glycol diacetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, diethylene glycol hexyl ether, diethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, dipropylene glycol phenyl ether, tetraethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, triethylene glycol monobutyl ether, tripropylene glycol butyl ether, tripropylene glycol monobutyl ether, and diethylene glycol dibutyl ether.

[0027] The solvent (C) is preferably contained in the photosensitive conductive paste in an amount of 5 to 20% by mass. By containing the solvent (C) in an amount of 5% by mass or more, the viscosity of the photosensitive conductive paste is reduced, improving the coatability in the coating step described below. By containing the solvent (C) in an amount of 20% by mass or less, drying is facilitated in the drying step described below, improving productivity.

[0028] The ceramic powder (D) preferably contains at least one selected from the group consisting of titania, alumina, silica, cordierite, mullite, spinel, barium titanate, and zirconia. Among these, alumina, titania, and silica are particularly preferred, and silica is more preferred from the viewpoint of micromachining.

[0029] The median diameter (D50) in the particle size distribution (number basis) of the ceramic powder (D) is preferably 5 to 100 nm. By making it 5 nm or more, dispersibility in the photosensitive conductive paste is improved. By making it 100 nm or less, the effect of suppressing over-sintering of the conductive powder is increased. The median diameter of the ceramic powder (D) can be determined by dynamic light scattering using a Nanotrac Wave II-UZ251 (manufactured by MicrotracBEL).

[0030] The content of ceramic powder (D) is preferably 0.2 to 3.1 parts by mass per 100 parts by mass of conductive powder (A). By setting the content of ceramic powder (D) to 0.2 parts by mass or more, over-firing can be further suppressed. By setting the content of ceramic powder (D) to 3.1 parts by mass or less, it is possible to suppress significant sintering inhibition and a decrease in conductivity.

[0031] The glass powder (E) has a softening point of 620 to 850°C, more preferably 720 to 850°C. By setting the softening point to 620°C or higher, it is possible to improve the binder removal property and improve the electrical conductivity. By setting the softening point to 850°C or lower, it is possible to suppress inhibition of sintering of the conductive powder. The softening point of the glass powder (E) can be measured by differential thermal analysis (DTA).

[0032] The median diameter (D50) in the particle size distribution (number basis) of the glass powder (E) is preferably 0.5 to 5.0 μm, more preferably 0.7 to 3.0 μm. By making the diameter 0.5 μm or more, the powder can be easily pulverized and classified, allowing for simple production. By making the diameter 5.0 μm or less, rattle of the wiring can be suppressed when fine wiring is formed. The particle diameter (D50) of the glass powder (E) can be measured by a laser light scattering method using a Microtrac HRA (Model No. 9320-X100; manufactured by Nikkiso Co., Ltd.).

[0033] The content of the glass powder (E) is preferably 0.3 to 5.0 parts by mass, more preferably 0.3 to 1.9 parts by mass, and even more preferably 0.5 to 1.9 parts by mass, relative to 100 parts by mass of the conductive powder (A). By setting the content to 0.3 parts by mass or more, shrinkage of the wiring electrode can be further suppressed. By setting the content to 5.0 parts by mass or less, an increase in the proportion of the glass powder (E) in the wiring electrode can be suppressed, thereby suppressing a decrease in conductivity.

[0034] The mass ratio of the ceramic powder (D) to the glass powder (E) (glass powder (E) / ceramic powder (D)) is preferably 0.5 to 15.0. By setting the ratio to 0.5 or more, excessive sintering inhibition by the ceramic powder (D) can be suppressed, thereby improving the conductivity. By setting the glass powder (E) / ceramic powder (D) ratio to 15.0 or less, the ratio of the ceramic powder decreases, thereby suppressing disconnection due to over-sintering. The glass powder (E) / ceramic powder (D) ratio is more preferably 10.0 or less. The mass ratio of the ceramic powder (D) to the glass powder (E) can be determined by observing a cross section perpendicular to the film surface of a dried film obtained by applying a photosensitive conductive paste, drying it, and removing the solvent, using a transmission electron microscope (e.g., JEM-4000EX manufactured by JEOL Ltd.), determining the volume ratio from the area ratio of the ceramic powder (D) to the glass powder (E), and converting the specific gravity calculated from the composition to the mass ratio. The ceramic powder (D) and the glass powder (E) can be separated by compositional analysis such as EDX. Furthermore, when the ceramic powder (D) is nanoparticles, the mass ratio of the glass powder (E) to the conductive powder is determined in the same manner, and the mass ratio of the ceramic powder (D) can be calculated from the total amount of the ceramic powder (D) and glass powder (E) relative to the conductive powder (A) described above. Furthermore, when the blending amounts of each component are known, the mass ratio can be determined from the blending amounts.

[0035] The absolute value of the refractive index difference between the ceramic powder (D) and the glass powder (E) is preferably 0.14 or less. By setting the refractive index to 0.14 or less, light scattering is suppressed in the exposure step described below, making it possible to form fine wiring. The absolute value of the refractive index difference is more preferably 0.10 or less. The refractive indexes of the ceramic powder (D) and the glass powder (E) can be measured by the Becke line detection method. The refractive index here indicates the value at a wavelength of 436 nm (g-line) at 25°C. Note that if the composition of the ceramic powder (D) is known, literature values ​​can be used.

[0036] The photosensitive conductive paste of the present invention may contain a photosensitive monomer, a sensitizer, a dispersant, a plasticizer, a leveling agent, a surfactant, a silane coupling agent, an antifoaming agent, a stabilizer, etc., within a range that does not impair the desired properties.

[0037] The photosensitive monomer refers to a monomer or oligomer having a carbon-carbon double bond. The structure having a carbon-carbon double bond is as described above.

[0038] The dispersant is a component that disperses and stabilizes one or more selected from the conductive particles (A), ceramic powder (D), and glass powder (E). Examples of the dispersant include amine-based dispersants, and carboxylic acid or carboxylic acid ester-based dispersants.

[0039] The photosensitive conductive paste of the present invention can be obtained, for example, by mixing and / or dispersing the aforementioned components (A) to (E) and, if necessary, other additives. Examples of devices for mixing and / or dispersing include dispersers such as triple rollers and ball mills, and kneaders.

[0040] Next, the cured film of the present invention will be described. The cured film of the present invention is a film obtained by curing the photosensitive conductive paste of the present invention, and preferably has a film thickness of 5 to 30 μm. By making the film thickness of the cured film 5 μm or more, disconnection during firing can be further suppressed, which is preferable. On the other hand, by making the film thickness of the cured film 30 μm or less, finer wiring can be formed, which is preferable.

[0041] The cured film of the present invention may have a predetermined pattern shape. Examples of the pattern shape include a linear shape and a spiral shape. The minimum width of the pattern shape is preferably 10 to 50 μm. By setting the pattern width to 10 μm or more, it is possible to suppress wire breakage during firing. On the other hand, by setting the pattern width to 50 μm or less, the aspect ratio of the pattern becomes large, and the sheet resistance of the internal wiring can be reduced.

[0042] The cured film of the present invention can be obtained, for example, by applying the photosensitive conductive paste of the present invention to a substrate to form a coating film, drying the coating film to form a dry film, and photo-curing the dry film by exposure. When a patterned cured film is produced, the dry film may be exposed to light and developed to form a pattern.

[0043] The coating film using the photosensitive conductive paste of the present invention described above may be formed on a substrate after drying a resin composition containing inorganic particles (F) and an organic component (G) to form a film.

[0044] Examples of the coating method in the coating step include spray coating, roll coating, screen printing, and coating methods using a blade coater, a die coater, a calendar coater, a meniscus coater, a bar coater, etc. The thickness of the coating film can be appropriately selected depending on the coating method, the solids concentration and viscosity of the photosensitive conductive paste, etc.

[0045] Drying methods include, for example, heat drying using a heating device such as an oven, a hot plate, or infrared, and vacuum drying. The heating temperature is preferably 40 to 80°C. By setting the drying temperature to 40°C or higher, the solvent can be efficiently removed by evaporation, and tackiness of the dried film can be suppressed. On the other hand, by setting the drying temperature to 80°C or lower, warping of the substrate can be suppressed. The heating time is preferably 2 to 60 minutes.

[0046] Exposure methods include exposure through a photomask and exposure without using a photomask. Examples of exposure methods without using a photomask include direct writing using laser light, etc. Examples of exposure devices include stepper exposure machines and proximity exposure machines. Examples of actinic rays used for exposure include near-ultraviolet rays, ultraviolet rays, electron beams, X-rays, laser light, etc., with ultraviolet rays being preferred. Examples of ultraviolet light sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, halogen lamps, and germicidal lamps, with ultra-high-pressure mercury lamps being preferred.

[0047] An example of the development is alkaline development.

[0048] Examples of developers for alkaline development include aqueous solutions of tetramethylammonium hydroxide, diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethylamine, dimethylaminoethyl acetate, dimethylaminoethanol, dimethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine, hexamethylenediamine, etc. To these aqueous solutions, polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, etc.; alcohols such as methanol, ethanol, isopropanol, etc.; esters such as ethyl lactate, propylene glycol monomethyl ether acetate, etc.; cyclopentanone, cyclohexanone, isobutyl ketone, ketones such as methyl isobutyl ketone, etc.; surfactants, etc. may be added.

[0049] Examples of the developing method include a method in which a developer is sprayed onto a substrate on which a cured film has been formed after exposure while the substrate is left standing, transported, or rotated; a method in which a substrate on which a cured film has been formed after exposure is immersed in a developer; and a method in which ultrasonic waves are applied to a substrate on which a cured film has been formed after exposure while the substrate is immersed in a developer.

[0050] The cured film obtained by development may be subjected to a rinse treatment using a rinse solution. Examples of the rinse solution include water; aqueous solutions of alcohols such as ethanol and isopropyl alcohol; and aqueous solutions of esters such as ethyl lactate and propylene glycol monomethyl ether acetate. Furthermore, the process may include a step of drying the remaining solvent in the cured film. By drying the remaining solvent, the shrinkage rate can be reduced in the baking step described below. The drying method may use the same drying device as in the drying method described above.

[0051] The cured film of the present invention can also be laminated to form a laminate. The number of laminated layers is preferably 1 to 30. By laminating one or more layers, the thickness of a predetermined pattern can be increased. On the other hand, by laminating 30 or less layers, the influence of misalignment between layers can be reduced.

[0052] Next, the sintered body of the present invention will be described. The sintered body of the present invention is obtained by sintering the cured film of the present invention, and its shape is not limited. The thickness of the sintered body is preferably 2 to 20 μm. By making the thickness of the sintered body 2 μm or more, it is possible to suppress breakage during sintering. On the other hand, by making the thickness of the sintered body 20 μm or less, it is possible to suppress swelling during sintering.

[0053] The line width of the fired body of the present invention is preferably 5 to 40 μm. By making the line width of the fired body 5 μm or more, it is possible to suppress breakage during firing. On the other hand, by making the line width of the fired body 40 μm or less, it is possible to form a conductive pattern with a higher aspect ratio.

[0054] The fired body of the present invention can be obtained, for example, by firing the cured film or laminate thereof described above. Examples of firing methods include a method in which the film is heat-treated at 300 to 600°C for 5 minutes to several hours, and then further heat-treated at 850 to 900°C for 5 minutes to several hours.

[0055] The method for manufacturing the electronic component of the present invention preferably includes the steps of applying a photosensitive conductive paste, drying, and exposing and developing. As an example of the method for manufacturing the electronic component of the present invention, a method for manufacturing a multilayer chip inductor will be described below.

[0056] First, via holes are formed in a substrate (hereinafter referred to as a ceramic green sheet) that has been coated and dried with a resin composition containing inorganic particles (F) and an organic component (G), and conductors are embedded in the via holes to form interlayer connection wiring. For example, laser irradiation can be used as a method for forming via holes. When the organic component (G) is a photosensitive organic component, vias can be formed with high precision by coating, drying, and then exposing and developing the resulting material through a mask with a via shape.

[0057] Examples of methods for embedding a conductor in a via hole include a method of embedding a conductor paste by screen printing and drying it. Examples of the conductor paste include pastes containing copper, silver, or a silver-palladium alloy. The photosensitive conductive paste of the present invention is preferred because it can form interlayer connection wiring and internal wiring at the same time, simplifying the process.

[0058] Internal wiring is formed on the ceramic green sheet on which the interlayer connection wiring has been formed. Examples of methods for forming the internal wiring include photolithography using a photosensitive conductive paste. The photosensitive conductive paste of the present invention described above can be preferably used as the photosensitive conductive paste, from the viewpoint of suppressing shrinkage of the wiring electrode and imparting excellent conductivity. If necessary, a dielectric pattern or an insulator pattern is further formed. Examples of methods for forming the dielectric pattern and the insulator pattern include screen printing.

[0059] Next, a plurality of ceramic green sheets on which interlayer connection wiring and internal wiring have been formed are laminated and thermocompression bonded to obtain a laminate. Examples of lamination methods include stacking ceramic green sheets using guide holes. Examples of thermocompression bonding devices include hydraulic presses. The thermocompression bonding temperature is preferably 90 to 130°C, and the thermocompression bonding pressure is preferably 5 to 20 MPa.

[0060] The resulting laminate is diced into desired chip sizes, fired, coated with terminal electrodes, and plated to obtain a multilayer chip inductor. Examples of dicing machines include a die cutter and a laser cutter. Examples of firing methods include heat treatment at 300 to 600°C for 5 minutes to several hours, followed by a further heat treatment at 850 to 900°C for 5 minutes to several hours.

[0061] The maximum firing temperature is preferably 100 to 300°C higher than the softening point of the glass powder (E). By setting the temperature at 100°C or higher, the fluidity of the glass can be improved and the conductivity of the electrode can be prevented from being impaired. By setting the temperature at 300°C or lower, separation of the glass from the electrode due to the fluidity of the glass can be prevented.

[0062] Examples of methods for applying the terminal electrodes include sputtering, electrolytic plating, etc. Examples of metals used for plating include nickel, tin, etc. [Example]

[0063] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0064] (Photosensitive conductive paste) The raw materials used for the photosensitive conductive paste are as follows:

[0065] Conductive powder (A) Conductive powder (A-1): Ag powder with a particle size (D50) of 2.1 μm The particle diameter (D50) of the conductive powder was measured by a laser light scattering method using a particle size distribution measuring device (Microtrac HRA Model No. 9320-X100; manufactured by Nikkiso Co., Ltd.).

[0066] Photosensitive organic component (B) Alkali-soluble resin: Acrylic resin obtained by addition reaction of 40 moles of glycidyl methacrylate to 100 moles of carboxyl groups in a copolymer of methacrylic acid / methyl methacrylate / styrene = 54 / 23 / 23 (molar ratio) (weight average molecular weight 30,000, glass transition point 110°C, acid value 100 mgKOH / g) Photopolymerization initiator: Adeka Optomer N-1919 (manufactured by ADEKA Corporation).

[0067] Solvent (C) Solvent 1: Ethylene glycol monobutyl ether acetate Solvent 2: Diethylene glycol dibutyl ether.

[0068] Ceramic powder (D) Ceramic powder (D-1): "AEROSIL" 130 (manufactured by Nippon Aerosil Co., Ltd.), particle size 21 nm, refractive index 1.46 Ceramic powder (D-2): "Silica Plain (Hydrophillic) Microsphere 1.0 μm" (manufactured by Bangs Laboratories), particle size 1.0 μm, refractive index 1.46.

[0069] Glass powder (E) Glass powder (E-1): silicon dioxide (75.8% by mass), boron oxide (20.1% by mass), potassium oxide (4.1% by mass), particle size (D50) 1.1 μm, glass softening point 730°C, refractive index 1.52 Glass powder (E-2): Bismuth oxide (48.1% by mass), silicon dioxide (27.5% by mass), boron oxide (14.2% by mass), zinc oxide (2.6% by mass), particle size (D50) 1.1 μm, glass softening point 510°C, refractive index 1.60 The particle size (D50) of the glass powder (E) was measured by a laser light scattering method using a particle size distribution analyzer (Microtrac HRA Model No. 9320-X100; manufactured by Nikkiso Co., Ltd.). The softening point of the glass powder (E) was measured by differential thermal analysis (DTA), and the refractive index was measured at a wavelength of 436 nm (g-line) at 25°C using a Becke line detection method.

[0070] Photosensitive monomer: NK Oligo UA-122P (urethane acrylate containing an ester structure, viscosity 7.0 Pa·s, weight-average molecular weight 1,100, manufactured by Shin-Nakamura Chemical Co., Ltd.) Leveling agent: "Disparlon (registered trademark)" L-1980N (manufactured by Kusumoto Chemicals Co., Ltd.) Dispersant: FLORENE G-700 (manufactured by Kyoeisha Chemical Co., Ltd.).

[0071] Example 1 <Preparation of photosensitive conductive paste> 50.0 g of alkali-soluble resin, 24.0 g of NK Oligo UA-122P (photosensitive monomer), 5.0 g of Adeka Optomer N-1919 (photopolymerization initiator), 1.0 g of Disparlon L-1980N (leveling agent), 1.0 g of Florene G-700 (dispersant), 59.0 g of ethylene glycol monobutyl ether acetate (solvent 1), and 59.0 g of diethylene glycol dibutyl ether (solvent 2) were mixed to obtain 199.0 g of photosensitive resin solution.

[0072] The resulting 199.0 g of photosensitive resin solution, 616.0 g of Ag powder (A-1), 2.5 g of ceramic powder (D-1), and 11.7 g of glass powder (E-1) were mixed and kneaded using three rollers to obtain photosensitive conductive paste P-1.

[0073] <Preparation of photosensitive dielectric paste> A photosensitive resin solution was prepared in the same manner as in <Preparation of Photosensitive Conductive Paste>. 199.0 g of the resulting photosensitive resin solution was mixed with 80.0 g of ceramic powder (D-2) and 120.0 g of glass powder (E-1), and the mixture was kneaded using a three-roller mill to obtain a photosensitive dielectric paste.

[0074] <Microfabrication evaluation> The photosensitive conductive paste was screen-printed onto an alumina substrate so that the film thickness after drying would be 10 μm, and then dried at 60°C for 10 minutes. The resulting dried film was exposed to 300 mJ / cm2 at a wavelength of 365 nm using an exposure device (PEM-6M; manufactured by Union Optical Co., Ltd.) through an exposure mask with openings of 5 to 40 μm in 1 μm increments. 2 After full-line exposure, the substrate was immersed in a 0.2% by mass Na2CO3 solution and then rinsed with ultrapure water. The minimum line width (μm) without breakage or peeling was defined as the resolution limit line width. The line width of the conductive pattern was measured by observation at 1000x magnification using an optical microscope, and the film thickness of the conductive pattern was measured using a stylus-type step profiler (e.g., "Surfcom (registered trademark)" 1400; manufactured by Tokyo Seimitsu Co., Ltd.).

[0075] <Conductivity evaluation> A conductive pattern was formed on an alumina substrate using the same method as in <Evaluation of Microfabrication>. However, the exposure mask was the mask pattern shown in Figure 1, with an opening width of 40 μm and a length of 4.0 cm. The resulting substrate with conductive pattern was fired at 880°C for 10 minutes to obtain a fired conductive pattern. The resistance value R of the fired conductive pattern for resistance measurement was measured using a digital multimeter (CDM-16D; manufactured by Custom). Next, the line width and film thickness of the fired conductive pattern were measured using the same method as above, and the specific resistance value was calculated using the following formula. The pattern was measured at 10 points and the average value was used. Resistivity (μΩ·cm) = Resistance of conductive pattern (μΩ) × Line width (cm) × Film thickness (cm) ÷ Length of conductive pattern (cm).

[0076] <Disconnection probability evaluation> 100 patterns were formed on an alumina substrate using the same method as in <Conductivity Evaluation>, and the probability of disconnection was calculated using the following formula. Probability of breakage = Number of breakages (%).

[0077] <Void evaluation> A photosensitive dielectric paste was screen-printed onto a polyethylene terephthalate (PET) film to a thickness of 10 μm after drying and dried at 60°C for 10 minutes. It was then exposed without a mask. This process was repeated to form a 50 μm first dielectric layer. Next, a dried film of photosensitive conductive paste was formed using the same method as in the microfabrication evaluation, except for the substrate. This was then exposed and developed using an exposure mask with a coil pattern with 25 μm openings, resulting in a first coil pattern. A photosensitive dielectric paste was then printed and dried to a thickness of 10 μm after drying, and the film was exposed and developed using a mask, except for the designated vias. This formed a second dielectric layer on the first coil pattern. The photosensitive conductive paste was then printed, exposed, and developed in the same manner to form a second coil pattern. The first and second coil patterns were connected via the vias formed in the second dielectric layer. This process was repeated alternately to form 10 layers of dielectric layers and coil patterns. An 11th dielectric layer, 200 μm thick, was then formed by repeatedly forming dielectric layers. This laminate was cut into 500 μm square pieces using a laser to form chips. The resulting laminate was sintered at 880°C for 10 minutes to obtain a sintered body with a coil electrode inside. The center of the sintered body was cut perpendicular to the lamination direction, and the presence or absence of voids between the electrode and the dielectric layer was evaluated. Evaluation was performed using a scanning electron microscope (S2400; manufactured by Hitachi, Ltd.) at a magnification of 250x, and the presence of one or more voids of 10 μm or more was evaluated as "voids present." Ten sintered bodies were evaluated, and a score of "good" was given for zero voids, "fair" for one void, and "poor" for two or more voids.

[0078] (Examples 2 to 10, Comparative Examples 1 to 6) Photosensitive conductive pastes P-2 to 10 and R-1 to 6 were prepared in the same manner as in Example 1, except that the conductive powder (A), ceramic powder (D), and glass powder (E) shown in Table 1 were mixed in the ratios shown in Table 1. The prepared photosensitive conductive pastes were then evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0079] [Table 1] [Industrial Applicability]

[0080] The photosensitive conductive paste of the present invention can be suitably used for producing internal wiring patterns for electronic components and the like. [Explanation of symbols]

[0081] L opening width

Claims

1. The electroconductive powder (A), the photosensitive organic component (B), the solvent (C), the ceramic powder (D), and the glass powder (E) are contained, and the softening point of the glass powder (E) is 620 to 850°C, and the total amount of the ceramic powder (D) and the glass powder (E) is 0.7 to 5.0 parts by mass per 100 parts by mass of the electroconductive powder (A), A photosensitive conductive paste in which the glass powder (E) is contained in an amount of 0.3 to 1.9 parts by mass per 100 parts by mass of the conductive powder (A).

2. 2. The photosensitive conductive paste according to claim 1, wherein the absolute value of the difference in refractive index between the ceramic powder (D) and the glass powder (E) is 0.14 or less.

3. 3. The photosensitive conductive paste according to claim 1, wherein the ceramic powder (D) is silica having a particle size of 5 to 100 nm.

4. 4. The photosensitive conductive paste according to claim 1, wherein the mass ratio of the ceramic powder (D) to the glass powder (E) (glass powder (E) / ceramic powder (D)) is 0.5 to 10.

0.

5. A resin composition containing inorganic particles (F) and an organic component (G) is dried on a substrate to form a film, and then A step of applying the photosensitive conductive paste according to any one of claims 1 to 4 to form a coating film; a step of drying the coating film to form a dry film; and a step of exposing and developing the dry film to form a pattern. A method for producing a substrate having a conductive pattern, comprising:

6. The method for producing a substrate having a conductive pattern according to claim 5, wherein the organic component (G) is a photosensitive organic component.

7. A cured film obtained by curing the photosensitive conductive paste according to any one of claims 1 to 4.

8. A method for producing a sintered body, comprising a step of firing the cured film according to claim 7 at a temperature 100 to 300° C. higher than the softening point of the glass powder (E).

9. A sintered body obtained by sintering the cured film according to claim 7.

10. An electronic component comprising the fired body according to claim 9 .

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