JP7806563B2 - Photosensitive conductive paste, method for manufacturing substrate with conductive pattern, cured film, method for manufacturing fired body, fired body and electronic component - Google Patents

Description

The present invention relates to a photosensitive conductive paste, a method for manufacturing a substrate with a conductive pattern, a cured film, a method for manufacturing a fired body, a fired body, and an electronic component.

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 within it. 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).

Inductor components can be manufactured in two ways: by forming internal electrodes on insulating sheets containing ceramic and resin, and then stacking multiple 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.

Japanese Patent Application Laid-Open No. 2019-215446

However, with 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, posing the problem of voids and bubbles forming between the insulating sheet and insulating layer.

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 manufacturing a substrate with a conductive pattern, a cured film, a method for manufacturing a sintered body, a sintered body, and an electronic component.

The present invention is a photosensitive conductive paste containing conductive powder (A), photosensitive organic component (B), solvent (C), ceramic powder (D), and 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).

The present invention makes it possible to produce a photosensitive conductive paste that can form fine wiring, suppresses shrinkage, and has excellent conductivity, as well as a cured film, a fired body, and electronic components.

Mask pattern of the exposure mask.

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), with the total amount of the ceramic powder (D) and the glass powder (E) being 0.7 to 5.0 parts by mass per 100 parts by mass of the conductive powder (A).

When heated and fired, the conductive powder (A) melts and fuses to form 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. Because the glass powder (E) melts during firing, it has little effect in preventing over-sintering of the conductive particles, but by remaining, it can suppress shrinkage of the wiring electrode.

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, fine patterns can be formed. On the other hand, by setting the total amount of (D) and (E) to 5.0% by mass or less, the proportion of conductive powder in the wiring electrode is reduced, 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 fine patterns. Therefore, the inventors discovered that by combining ceramic powder (D) and glass powder (E), it is possible to prevent disconnection defects due to over-sintering of the conductive powder, suppress shrinkage, and obtain wiring electrodes with excellent conductivity. The total amount of ceramic powder (D) and glass powder (E) is more preferably 0.9 to 3.8 parts by mass per 100 parts by mass of conductive powder (A).

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

The conductive powder (A) melts or fuses when heated and fired, exhibiting electrical conductivity. Examples of 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. Of these, silver, copper, and gold are preferred from the perspective of electrical conductivity, silver and copper are more preferred from the perspective of cost, and silver is even more preferred from the perspective of stability.

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 setting the D50 of the conductive powder (A) to 0.3 μm or more, it is possible to efficiently transmit the exposed light in the exposure and development process described below, allowing for sufficient curing to proceed to the bottom. This is also preferable because it suppresses pattern peeling and allows for the formation of finer patterns. 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 setting the D50 of the conductive powder (A) to 6.0 μm or less, it is possible to suppress pattern rattle after formation and allow for the formation of finer patterns. 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 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.).

The content of conductive powder (A) in the photosensitive conductive paste is preferably 60 to 90% by mass, and more preferably 68 to 85% by mass. A content of conductive powder (A) of 60% by mass or more is preferred because it improves the probability of contact between conductive powders (A) during the firing process described below, thereby preventing pattern breakage. A content of conductive powder (A) of 68% by mass or more is more preferred. On the other hand, a content of conductive powder (A) of 90% by mass or less is preferred because it prevents pattern peeling during the exposure and development process and allows for the formation of finer patterns. A content of conductive powder (A) of 85% by mass or less is more preferred.

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 (e.g., Hitachi High-Tech Science's "PS3520DDII"). Furthermore, if the blending amounts of each component are known, the content can be determined from the blending amounts.

The photosensitive organic component (B) refers to an organic component containing an alkali-soluble resin and a photosensitizer. An alkali-soluble resin refers to a resin having an alkali-soluble group. Examples of alkali-soluble groups include carboxyl groups, phenolic hydroxyl groups, sulfonic acid groups, and thiol groups. Among these, carboxyl groups are preferred due to their high solubility in alkaline developers.

As the alkali-soluble resin, acrylic resin is preferred, and a copolymer of an acrylic monomer having a carbon-carbon double bond with another monomer is preferred. Examples of acrylic monomers 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 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 replacing 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, and acid anhydrides thereof. Two or more of these may be used.

Acrylic resins preferably have carbon-carbon double bonds in the side chains or molecular terminals, which can improve the curing reaction rate during exposure. Examples of structures with carbon-carbon double bonds include vinyl groups, allyl groups, acrylic groups, and methacrylic groups. Two or more of these may be present. Methods for introducing carbon-carbon double bonds into acrylic resins include, for example, reacting a mercapto group, amino group, hydroxyl group, or carboxyl group in the acrylic resin with a compound having a glycidyl group or an isocyanate group and a carbon-carbon double bond, such as acrylic acid chloride, methacrylic acid chloride, or allyl chloride.

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, and Cyclomer (registered trademark) M100 and 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, and methacryloylethyl isocyanate. Two or more of these may be used.

Examples of photosensitizers include photopolymerization initiators and dissolution inhibitors. Photopolymerization initiators are preferred from the perspective of forming thicker conductive patterns.

Photopolymerization initiators absorb short-wavelength light such as ultraviolet light and decompose, or generate radicals through a hydrogen abstraction reaction, imparting photocuring properties and enabling pattern formation using negative-tone 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, and phenylglyoxylic acid methyl ester. Two or more of these may be used.

Dissolution inhibitors increase the solubility of exposed areas in the developer, enabling pattern formation using positive-tone photolithography. Dissolution inhibitors that generate acid upon exposure to light are preferred. Examples include diazodisulfone compounds, triphenylsulfonium compounds, and quinone diazide compounds. Examples of diazodisulfone compounds include bis(cyclohexylsulfonyl)diazomethane, bis(tert-butylsulfonyl)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 quinone diazide compounds include those in which the sulfonic acid of quinone diazide is bonded to a polyhydroxy compound via an ester bond, those in which the sulfonic acid of quinone diazide is bonded to a polyamino compound via a sulfonamide bond, and those in which the sulfonic acid of quinone diazide is bonded to a polyhydroxy polyamino compound via an ester bond and/or a sulfonamide bond. Two or more of these may be used.

Solvent (C) is liquid at room temperature and wets or dissolves the components that make up the photosensitive conductive paste, making it a liquid with excellent coatability. The boiling point of solvent (C) is preferably 180 to 300°C. A boiling point of 300°C or less can improve binder removal during firing. A boiling point of 230°C or less is more preferable, and a boiling point of 230°C or less allows for easy drying in the drying process described below. Furthermore, a boiling point of 180°C or higher can suppress an increase in viscosity during the coating process. Note that the boiling point of the solvent refers to the boiling point at 1013.25 hPa.

Examples of solvents 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, and dipropylene glycol monomethyl ether. Examples of suitable ethers include ethyl ether acetate, 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.

The solvent (C) is preferably contained in the photosensitive conductive paste at 5 to 20% by mass. A content of 5% by mass or more reduces the viscosity of the photosensitive conductive paste, improving its coatability in the coating process described below. A content of 20% by mass or less facilitates drying in the drying process described below, improving productivity.

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, with silica being even more preferred from the standpoint of micromachining ability.

The median diameter (D50) of the particle size distribution (number basis) of ceramic powder (D) is preferably 5 to 100 nm. A diameter of 5 nm or greater improves dispersibility in the photosensitive conductive paste. A diameter of 100 nm or less effectively prevents over-sintering of the conductive powder. The median diameter of ceramic powder (D) can be determined by dynamic light scattering using a Nanotrac Wave II-UZ251 (manufactured by Microtrac BEL).

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.

The softening point of glass powder (E) is 620 to 850°C, and preferably 720 to 850°C. Setting it to 620°C or higher improves binder removal and electrical conductivity. Setting it to 850°C or lower prevents sintering of the conductive powder. The softening point of glass powder (E) can be measured by differential thermal analysis (DTA).

The median diameter (D50) in the particle size distribution (number basis) of glass powder (E) is preferably 0.5 to 5.0 μm, more preferably 0.7 to 3.0 μm. A particle size of 0.5 μm or greater facilitates powder pulverization and classification, allowing for simple production. A particle size of 5.0 μm or less reduces wiring rattle when fine wiring is formed. The particle size (D50) of glass powder (E) can be measured by laser light scattering using a Microtrac HRA (Model No. 9320-X100; manufactured by Nikkiso Co., Ltd.).

The content of 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, per 100 parts by mass of 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 glass powder (E) in the wiring electrode and a decrease in conductivity can be suppressed.

The mass ratio of ceramic powder (D) to glass powder (E) (glass powder (E)/ceramic powder (D)) is preferably 0.5 to 15.0. A ratio of 0.5 or greater can suppress excessive sintering inhibition by ceramic powder (D), improving conductivity. A glass powder (E)/ceramic powder (D) ratio of 15.0 or less reduces the ceramic powder ratio, preventing wire breakage due to over-sintering. A glass powder (E)/ceramic powder (D) ratio of 10.0 or less is more preferable. The mass ratio of ceramic powder (D) to 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., JEOL Ltd.'s "JEM-4000EX"), determining the volume ratio from the area ratio of ceramic powder (D) to glass powder (E), and converting the specific gravity calculated from the composition to a mass ratio. Ceramic powder (D) and glass powder (E) can be separated by compositional analysis such as EDX. Furthermore, if the ceramic powder (D) is nanoparticles, the mass ratio of the glass powder (E) to the conductive powder can be determined in a similar manner, and the mass ratio of the ceramic powder (D) can be calculated from the total amount of ceramic powder (D) and glass powder (E) relative to the aforementioned conductive powder (A). Furthermore, if the blending amounts of each component are known, the blending amount can be used to determine the mass ratio.

The absolute value of the refractive index difference between ceramic powder (D) and glass powder (E) is preferably 0.14 or less. By keeping it 0.14 or less, light scattering is suppressed in the exposure process described below, making it possible to form fine wiring. It is more preferable that the absolute value of the refractive index difference is 0.10 or less. The refractive indexes of ceramic powder (D) and glass powder (E) can be measured using the Becke line detection method. The refractive index here refers to the value at a wavelength of 436 nm (g-line) at 25°C. If the composition of ceramic powder (D) is known, literature values can be used.

The photosensitive conductive paste of the present invention may contain photosensitive monomers, sensitizers, dispersants, plasticizers, leveling agents, surfactants, silane coupling agents, antifoaming agents, stabilizers, etc., to the extent that the desired properties are not impaired.

A 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.

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

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 equipment for mixing and/or dispersing include dispersers such as triple rollers and ball mills, and kneaders.

Next, we will explain the cured film of the present invention. The cured film of the present invention is a film formed by curing the photosensitive conductive paste of the present invention, and preferably has a film thickness of 5 to 30 μm. A cured film thickness of 5 μm or more is preferable because it can further suppress wire breakage during firing. On the other hand, a cured film thickness of 30 μm or less is preferable because it can form finer wiring.

The cured film of the present invention may have a predetermined pattern shape. Examples of pattern shapes include linear shapes and spiral shapes. The minimum width of the pattern shape is preferably 10 to 50 μm. By making the pattern width 10 μm or more, it is possible to suppress wire breakage during firing. On the other hand, by making the pattern width 50 μm or less, the aspect ratio of the pattern increases, making it possible to reduce the sheet resistance of the internal wiring.

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 producing a patterned cured film, the dried film may be exposed to light and developed to form a pattern.

A 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.

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

Drying methods include, for example, heat drying using a heating device such as an oven, hot plate, or infrared heater, 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 volatilized and the tackiness of the dried film can be reduced. On the other hand, by setting the drying temperature to 80°C or lower, warping of the substrate can be reduced. The heating time is preferably 2 to 60 minutes.

Exposure methods include those using a photomask and those without a photomask. Exposure methods without 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 light, ultraviolet light, electron beams, X-rays, and laser light, with ultraviolet light 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.

An example of a development method is alkaline development.

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, and hexamethylenediamine. These aqueous solutions may also contain polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone; alcohols such as methanol, ethanol, and isopropanol; esters such as ethyl lactate and propylene glycol monomethyl ether acetate; cyclopentanone, cyclohexanone, and isobutyl ketone; ketones such as methyl isobutyl ketone; surfactants, and the like.

Examples of development methods include spraying a developer onto a substrate on which a cured film has been formed after exposure while the substrate is left stationary, transported, or rotated; immersing a substrate on which a cured film has been formed after exposure in a developer; and applying ultrasound to a substrate on which a cured film has been formed after exposure while immersing the substrate in a developer.

The cured film obtained by development may be rinsed with a rinse solution. Examples of rinse solutions 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, a step of drying any remaining solvent in the cured film may be included. Drying the remaining solvent can reduce the shrinkage rate in the baking step described below. The same drying equipment as used for the drying method described above can be used for the drying method.

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

Next, we will explain the sintered body of the present invention. The sintered body of the present invention is obtained by sintering the cured film of the present invention, and its shape is not important. 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.

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.

The fired body of the present invention can be obtained, for example, by firing the aforementioned cured film of the present invention or a laminate thereof. Firing methods include, for example, 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.

The manufacturing method for 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 a manufacturing method for the electronic component of the present invention, a method for manufacturing a multilayer chip inductor is described below.

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). Conductors are then embedded in the via holes to form interlayer connection wiring. Examples of via hole formation methods include laser irradiation. If the organic component (G) is a photosensitive organic component, precise vias can be formed by coating, drying, and then exposing and developing the resulting material through a mask with a via shape.

One method for embedding a conductor in a via hole is to embed a conductive paste using screen printing and then dry it. Examples of conductive pastes include pastes containing copper, silver, or silver-palladium alloys. 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.

Internal wiring is formed on the ceramic green sheets 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 is preferably used as the photosensitive conductive paste, as it suppresses shrinkage of the wiring electrodes and provides excellent conductivity. If necessary, a dielectric pattern or an insulator pattern is then formed. Examples of methods for forming the dielectric pattern and the insulator pattern include screen printing.

Next, multiple ceramic green sheets with interlayer connection wiring and internal wiring formed are stacked and thermocompression bonded to obtain a laminate. Examples of stacking methods include stacking ceramic green sheets using guide holes. Examples of thermocompression bonding devices include hydraulic presses. The thermocompression temperature is preferably 90 to 130°C, and the thermocompression pressure is preferably 5 to 20 MPa.

The resulting laminate is diced to the desired chip size, fired, terminal electrodes are applied, and plating is performed to obtain a multilayer chip inductor. Examples of dicing machines include die cutters and laser cutters. Firing methods include, for example, heat treatment at 300-600°C for 5 minutes to several hours, followed by a further heat treatment at 850-900°C for 5 minutes to several hours.

The maximum firing temperature should be 100 to 300°C higher than the softening point of the glass powder (E). Setting the temperature at 100°C or higher improves the fluidity of the glass and prevents it from impairing the conductivity of the electrode. Setting the temperature at 300°C or lower prevents the glass from flowing and becoming separated from the electrode.

Examples of methods for applying terminal electrodes include sputtering and electrolytic plating. Metals used for plating include nickel and tin.

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.

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

Conductive powder (A)
Conductive powder (A-1): Ag powder having a particle size (D50) of 2.1 μm. The particle size (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.).

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

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

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 (Hydrophilic) Microsphere 1.0 μm" (manufactured by Bangs Laboratories), particle size 1.0 μm, refractive index 1.46.

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) of 1.1 μm, glass softening point of 730° C., refractive index of 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) of 1.1 μm, glass softening point of 510° C., refractive index of 1.60. The particle size (D50) of the glass powder (E) 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.). The softening point of the glass powder (E) was measured by differential thermal analysis (DTA), and the refractive index was measured at 25° C. with a wavelength of 436 nm (g-line) by a Becke line detection method.

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.).

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 Floren 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 a photosensitive resin solution.

The resulting 199.0 g of photosensitive resin solution was mixed with 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), and kneaded using three rollers to obtain photosensitive conductive paste P-1.

<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 three rollers to obtain a photosensitive dielectric paste.

<Evaluation of microfabrication>
A photosensitive conductive paste was screen-printed onto an alumina substrate to a dry film thickness of 10 μm, followed by drying at 60°C for 10 minutes. The resulting dried film was subjected to full-line exposure at 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. The substrate was then immersed in a _0.2 % by mass _Na2CO3 solution and 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.).

<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 FIG. 1, with an opening width of 40 μm and a length of 4.0 cm. The obtained substrate with the 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 calculated.
Specific resistance value (μΩ·cm)=Conductive pattern resistance value (μΩ)×line width (cm)×film thickness (cm)÷Conductive pattern length (cm).

<Disconnection probability evaluation>
100 patterns were formed on an alumina substrate in the same manner as in <Conductivity Evaluation>, and the probability of wire breakage was calculated using the following formula.
Probability of breakage = number of breakages (%).

<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. The paste 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 <Microfabrication Evaluation>, except for the substrate. This was then exposed and developed using an exposure mask with a coil pattern having 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 except for the designated vias, forming a second dielectric layer on the first coil pattern. A 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 eleventh 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 produced 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. The 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 the presence of zero voids was evaluated as "good," one void as "passable," and two or more voids as "fail."

(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. Subsequently, the prepared photosensitive conductive pastes were evaluated in the same manner as in Example 1. The results are shown in Table 1.

The photosensitive conductive paste of the present invention can be suitably used for manufacturing internal wiring patterns for electronic components, etc.

L opening width

Claims (10)

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. 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. 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. 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. 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 method for producing a substrate having a conductive pattern, comprising: 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. The method for producing a substrate having a conductive pattern according to claim 5 , wherein the organic component (G) is a photosensitive organic component. A cured film obtained by curing the photosensitive conductive paste according to any one of claims 1 to 4 . 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). A sintered body obtained by sintering the cured film according to claim 7 . An electronic component comprising the fired body according to claim 9 .