JPH10330168A - Ceramic green sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic green sheet capable of forming a via hole readily in high precision and surely making a fine hole as a photomask pattern. SOLUTION: This ceramic green sheet comprises inorganic particles and a photosensitive organic component and has >=30% total light transmittance. The inorganic filter is a raw material mixture comprising 40-60 wt.% of a glass composition composed of >=95 wt.% of the total of 30-70 wt.% of SiO2 , 5-25 wt.% of Al2 O3 , 5-25 wt.% of CaO and 3-50 wt.% of B2 O3 and one or more kinds of organic filler powder selected from the group consisting of alumina, zirconia, magnesia, beryllia mullite, cordierite, spinel, forsterite, anorthosite, celsian, silica and aluminum nitride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic green sheet suitably used for forming a fired ceramic substrate and the like. A ceramic green sheet is a fired ceramic substrate that is suitably used for high-density mounting, etc., on which semiconductor elements are mounted and interconnected with each other,
In particular, it refers to a green sheet made of ceramic suitably used for a multilayer ceramic substrate.

[0002]

2. Description of the Related Art In recent years, as electronic components have been operated at higher speeds, higher frequencies, and smaller sizes, it has been required to form fine via holes at a high density in a ceramic substrate for mounting them.

As described in JP-A-1-232797 and JP-A-2-141458, conventional ceramic green sheets are usually prepared by appropriately adding a ceramic powder, an organic binder, a plasticizer, a solvent and, if necessary, a dispersant. After mixing and mixing to form a slurry, the obtained slurry is formed into a sheet by a known method such as a doctor blade method.

[0004] Furthermore, a conventional method for forming a via hole in a green sheet is a via hole or a through hole (hereinafter, referred to as a via hole) by punching using a punching die (punch) made of carbide. Is formed.

In a conventional method of forming a via hole in a green sheet using a punching die (punch) made of a carbide, it is difficult to produce a punch having a small diameter because the strength of the carbide is low. When punching with the above-mentioned punch, there is a problem in that punching residue remains in the via hole, and the yield after processing is extremely low.

Further, JP-A-63-64953 and JP-A-2-204356 disclose that a composition containing a ceramic raw material, an ultraviolet-curable liquid compound and a photopolymerization initiator is cured by irradiating it with ultraviolet rays. Ceramic
A green sheet containing a bisazide compound in a green sheet or a glass ceramic green sheet has been proposed. In the green sheet, a so-called photolithography method is used in which the sheet is exposed and developed to form a via hole.

[0007]

However, there is no description about the cross-sectional shape of the via hole, which becomes a problem when the conductor paste is embedded in the via hole. When a via hole is formed by photolithography, light scattering generally occurs due to a difference in the refractive index between the ceramic powder and the photosensitive resin composition. For this reason, scattering occurs in a portion that becomes a via hole that is shielded from light by the photomask, and there is a problem that the via hole does not penetrate during development or the via hole has a shape smaller than the photomask pattern. In the green sheet having such a via hole shape, the conductor is not sufficiently filled when the via hole is filled with the conductor hole, resulting in poor conductivity.

The present invention solves the above-mentioned drawbacks of the prior art, and provides a ceramic green sheet capable of forming via holes very easily and accurately and capable of forming fine holes exactly according to a photomask pattern. To provide.

[0009]

Means for Solving the Problems As a result of diligent research, the present inventors have determined that the total light transmittance of the ceramic green sheet is set to 30% or more, or the regular transmittance is set to 2% or more. The inventors have found that the object of the invention can be achieved and completed the present invention.

That is, the present invention provides a ceramic green sheet containing inorganic particles and a photosensitive organic component, and having a total light transmittance of 30% or more.
Further, the present invention comprises inorganic particles and a photosensitive organic component,
Provided is a ceramic green sheet having a regular transmittance of 2% or more.

That is, in the present invention, it is important to impart photosensitivity to the green sheet itself made of ceramic, whereby via holes and through holes can be formed easily and accurately using photolithography technology, and fine A simple hole can be efficiently formed at low cost. Further, this method is for forming a via hole without a via barrel by making the shape of the via hole no difference in upper and lower hole diameters as in the shape of the photomask.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A ceramic green sheet of the present invention is composed of inorganic particles and a photosensitive organic component, and is baked after forming a via pattern using photolithography to form a via hole (also referred to as a via or through hole). To obtain a ceramic fired substrate on which is formed.

In the present invention, the content of the inorganic particles in the green sheet is 60 to 90% by weight, the content of the photosensitive organic component is 10 to 40% by weight, and the content of the inorganic particles is 70 to 90% by weight. %, And the photosensitive organic component is preferably 10 to 30% by weight, since the shrinkage ratio after firing can be reduced to 15 to 25% and the shape change due to firing can be reduced.

The inorganic component used in the present invention includes ceramic powder alone, glass-ceramic composite system, crystallized glass, amorphous glass and the like.

Examples of using ceramic powder alone include alumina (Al ₂ O ₃ ), zirconia (ZrO
_2), magnesia (MgO), beryllia (BeO), mullite _{(3 Al 2 O 3 · 2} SiO 2), cordierite _{(5 SiO 2 · 2 Al 2} O 3 · 2 MgO), spinel (MgO · Al ₂ O ₃ ) Forsterite (2MgO
.SiO ₂ ), anorthite (CaO.Al ₂ O ₃ .2)
SiO ₂ ), Celsian (BaO.Al ₂ O ₃ .2Si)
Powders such as O ₂ ), silica (SiO ₂ ), clinoenstatite (MgO.SiO ₂ ), and aluminum nitride (AlN), or low-temperature fired ceramic powders.

Examples of the glass-ceramics powder composite system include, for example, SiO ₂ , Al ₂ O ₃ , CaO, B ₂ O ₃
And a glass composition powder containing MgO and TiO ₂ as necessary, and alumina, zirconia, magnesia,
A raw material mixture with at least one inorganic filler powder selected from the group consisting of beryllia, mullite, cordierite, spinel, forsterite, anorthite, Celsian, silica and aluminum nitride can be used. In SiO ₂ 30 to 70 wt% Al ₂ O ₃ 5 to 25 wt% CaO 5 to 25 wt% B ₂ O ₃ 3 to 50% by weight of the composition range and more preferably ceramic powder in terms of oxide notation total amount 95 At least one selected from the group consisting of alumina, zirconia, magnesia, beryllia, mullite, cordierite, spinel, forsterite, anorthite, cellian, silica and aluminum nitride. And a raw material mixture with 60 to 40% by weight of the inorganic filler powder. That is, SiO ₂ , Al ₂ O ₃ , CaO, B ₂
The composition range of O ₃ , MgO and TiO ₂ is the ratio in the glass composition powder, and it is preferable that these components have a total amount of 95% by weight or more in the glass composition powder. The remaining 5% by weight is Na ₂ O, K ₂ O, BaO, PbO, Fe ₂ O
₃ , Mn oxide, Cr oxide, NiO, Co oxide and the like. Particularly preferably, the ceramic powder is expressed in terms of oxide as SiO ₂ 25 to 70% by weight Al ₂ O ₃ 15 to 50% by weight B ₂ O ₃ 5 to 20% by weight CaO 3 to 10% by weight MgO 3 to 10% by weight BaO In a composition range of 3 to 10% by weight of TiO _{2 and} 1 to 5% by weight, 40% by weight or more of glass composition particles having a total amount of 95% by weight or more; It is a raw material mixture with at least one kind of inorganic filler powder of 60% by weight or less selected from the group consisting of stellite, anorthite, Celsian, silica and aluminum nitride.

Specific examples of the glass-ceramic composite system include SiO ₂ —B ₂ O ₃ glass, PbO—SiO ₂
-Al ₂ O ₃ -B ₂ O ₃ based glass, CaO-SiO ₂ -
Examples thereof include those obtained by adding ceramic components such as Al ₂ O ₃ , quartz (SiO ₂ ), ZrO ₂ , and cordierite to an Al ₂ O ₃ —B ₂ O ₃ system glass or the like.

SiO ₂ in the glass composition powder is 30 to 70
It is preferably in the range of 30% by weight. If the amount is less than 30% by weight, the strength and stability of the glass layer are reduced, and the dielectric constant and the coefficient of thermal expansion are increased, so that the glass layer tends to deviate from desired values. 7
If it exceeds 0% by weight, the coefficient of thermal expansion of the fired substrate becomes high, and it becomes difficult to fire at 1000 ° C. or less.

It is preferable that Al ₂ O ₃ is blended in a range of 5 to 25% by weight. If it is less than 5% by weight, the strength in the glass phase is reduced, and baking at 1000 ° C. or lower becomes difficult. If it exceeds 25% by weight, the temperature at which the glass composition is fritted becomes too high.

It is preferable that CaO is blended in the range of 5 to 25% by weight. If the amount is less than 5% by weight, a desired coefficient of thermal expansion cannot be obtained, and baking at 1000 ° C. or lower becomes difficult. If it exceeds 25% by weight, the dielectric constant and the coefficient of thermal expansion increase, which is not preferable.

B ₂ O ₃ has a glass frit of 1300-1.
For melting at a temperature around 450 ° C., and for Al ₂ O ₃
In order to control the ceramic firing temperature in the range of 800 to 1000 ° C so that the electrical, mechanical and thermal properties such as dielectric constant, strength, coefficient of thermal expansion, sintering density, etc. are not impaired even when the amount is large. And the amount is preferably in the range of 3 to 50% by weight. If the content is less than 3% by weight, the strength of the ceramic tends to decrease if the content of B ₂ O ₃ is too large, and if the content exceeds 50% by weight, the stabilization of the glass is reduced, and the glass is regenerated by the reaction between the inorganic filler (crystal) and the glass. Crystallization is accelerated, and when a multi-layer substrate is formed, a phenomenon in which a glass phase oozes out is not preferable.

The inorganic filler powder is effective for improving the mechanical strength of the substrate and controlling the coefficient of thermal expansion. In particular, alumina, zirconia, mullite, cordierite, and anorthite have excellent effects. If the proportion of the inorganic filler exceeds 60% by weight, sintering becomes difficult, and sintering at 1000 ° C. or lower becomes difficult. If it is less than 40% by weight, it becomes difficult to control the thermal expansion coefficient and obtain a substrate having a low dielectric constant. Therefore, by setting the inorganic filler powder in this range, the firing temperature of the ceramic is set to 800 to 1000 ° C., and the strength, the dielectric constant, the thermal expansion coefficient, the sintered density, and the volume resistivity shrinkage can be set to desired characteristics. .

In the present invention, MgO may be blended in the range of 0 to 10% by weight to control the glass melting temperature. If it exceeds 10% by weight, the obtained substrate has a high coefficient of thermal expansion.

In the present invention, TiO ₂ is contained in an amount of 0 to 15% by weight as a nucleating substance effective in producing crystallized glass.
You may mix | blend in the range of. Before firing, the low-temperature fired ceramic substrate of the present invention is a mixture of amorphous glass and an inorganic filler, but depending on the type of filler, becomes a partially crystallized ceramic of amorphous glass, ceramic, and crystallized glass. It is estimated that there is.

In the inorganic filler powder used in the present invention,
Na ₂ O, K ₂ O, B up to 0 to 5% by weight as impurities
aO, PbO, Fe ₂ O ₃ , Mn oxide, Cr oxide,
NiO, Co oxide and the like can be contained.

As a method for producing the glass composition powder, for example, raw materials such as SiO ₂ , Al ₂ O ₃ , CaO, and B ₂ O ₃
, MgO, after melting and TiO _2, and quenched, there is a method by grinding after the glass frit and fine powder of 0.5 to 3 [mu] m. As a raw material, a high-purity carbonate, oxide, hydroxide or the like can be used. In addition, depending on the type and composition of the glass powder, an ultra-high purity alkoxide or organometallic raw material of 99.99% or more is used. This is preferable because a high-strength ceramic substrate can be obtained.

Specific examples of the crystallized glass include MgO—
Al ₂ O ₃ —SiO ₂ or Li ₂ O—Al ₂ O ₃ —Si
O ₂ -based crystallized glass or the like is used. Crystallized glass is obtained by adding B ₂ O ₃ and a nucleating substance to MgO—Al ₂ O ₃ —SiO ₂ , firing at 900 to 1000 ° C., and precipitating cordierite crystals to increase strength, L
_{i 2 O-Al 2 O 3} -SiO 2 in B ₂ O ₃ and nucleating agent was added, to precipitate a spodumene, it is also used similarly those aimed at strengthening.

The particle size and specific surface area of the inorganic particles used in the above are selected in consideration of the thickness of the green sheet to be produced and the shrinkage ratio after firing, and the average particle size is 50% by volume particle size (D50). ) Is 1 to 6 μm, the maximum particle size is 30 μm or less, and the specific surface area is 1.5 to ⁴ m ² /
g is preferable. More preferably, 10 volume% particle diameter (D10) 0.4 to 2 μm, 50 volume% particle diameter (D
50) 1.5 to 5 μm, 90% by volume particle size (D90):
A range of 4-15 .mu.m, the maximum particle diameter size is 25μm or less, a specific surface area 1.5~3.5m ² / g, more preferably D50 is 2～3.5Myuemu, specific surface area 1.5~3m ² / g
It is.

Here, D10, D50, and D90 are the particle diameters of the inorganic particles of 10% by volume, 50% by volume, and 90% by volume, respectively, from the small-sized inorganic particles.

By using the inorganic particles having the above particle size distribution, the filling property of the powder is improved, and even if the ratio of the powder in the green sheet is increased, air bubbles are reduced and extra light scattering is caused. Is small, the light transmittance can be increased. When the particle size of the inorganic particles is smaller than the above range, the specific surface area is increased, so that the cohesiveness of the powder is increased, and the dispersibility in the organic component is reduced, so that bubbles are easily entrained. Therefore, light scattering increases and light transmittance decreases. Even when the particle size of the inorganic particles is larger than the above range, the bulk density of the powder is reduced, so that the filling property is reduced, the amount of the photosensitive organic component is insufficient, bubbles are easily entrapped, and light scattering is apt to occur. Further, when the particle size distribution of the inorganic particles is in the above range, the powder filling ratio is high, so that the firing shrinkage ratio is low, and the via pattern shape is not easily collapsed during firing. If the ratio is out of the above range, the shrinkage after firing becomes large, and a green sheet with high accuracy cannot be obtained. The shape of the powder is preferably spherical, and a sharp particle size distribution is preferable because the influence of scattering at the time of exposure to ultraviolet light can be suppressed low. In particular, it is preferable to use cordierite or silica having a sphericity of 80% by number or more as the inorganic particles.

Although there is no particular limitation on the method for measuring the particle size, it is preferable to use a laser diffraction / scattering method because it can be measured easily. For example, the measurement conditions when the particle size distribution analyzer HRA9320-X100 manufactured by Microtrac Co., Ltd. is used are as follows. Sample amount: 1 g Dispersion conditions: Ultrasonic dispersion in purified water for 1 to 1.5 minutes. If dispersion is difficult, perform in a 0.2% aqueous sodium hexametaphosphate solution. Particle refractive index: changed depending on the type of inorganic particles Solvent refractive index: 1.33 Number of measurements: 2 times

As the photosensitive organic component used in the ceramic green sheet of the present invention, a conventionally known photosensitive resin can be used. The photosensitive layer made of such a photosensitive resin is a layer that is insolubilized or solubilized by irradiating an active light beam. Examples of the photoinsolubilized photosensitive substance include (1) a mixture of a functional monomer or oligomer having one or more unsaturated groups or the like in one molecule with an appropriate polymer binder, (2) an aromatic diazo compound, (3) a mixture of a photosensitive compound such as an aromatic diad compound or an organic halogen compound with an appropriate polymer binder;
A photosensitive polymer obtained by pending a photosensitive group to an existing polymer or a modified one thereof,
(4) So-called diazo resins, such as condensates of diazo-based amines and formaldehyde, and the like.

Examples of the photo-soluble photosensitive material include:
(1) A complex of an inorganic salt or an organic acid of a diazo compound, a quinonediazo compound mixed with an appropriate polymer binder, and (2) a quinonediazo compound combined with an appropriate polymer binder, for example, naphthoquinone of phenol or novolak resin 1,2-diazide-sulfonic acid ester, and the like.

A particularly preferred photosensitive resin composition is an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in a side chain, and is formed by copolymerizing an unsaturated carboxylic acid and an ethylenically unsaturated group. The acrylic copolymer can be produced by adding an ethylenically unsaturated group to a side difference.

Specific examples of the unsaturated carboxylic acid include:
Acrylic acid, methacrylic acid, itaconic acid, crotonic acid,
Maleic acid, fumaric acid, vinyl acetic acid, acid anhydrides thereof, and the like. On the other hand, specific examples of the ethylenically unsaturated compound include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, iso-butyl acrylate, isobutyl methacrylate, tert-butyl acrylate, te
Examples include, but are not limited to, rt-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, styrene, p-methylstyrene, o-methylstyrene, m-methylstyrene. By including at least methyl methacrylate among the above ethylenically unsaturated compounds as the main polymerization component of these acrylic main chain polymers, a copolymer having good thermal decomposability can be obtained.

Examples of the ethylenically unsaturated group in the side chain include vinyl, allyl, acryl and methacryl groups. As a method of adding such a side chain to an acrylic copolymer, there is a method of adding an ethylenically unsaturated compound having a glycidyl group to a carboxyl group in an acrylic copolymer or an acrylic acid chloride to carry out an addition reaction. .

Examples of the ethylenically unsaturated compound having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, glycidyl ethyl acrylate, crotonyl glycidyl ether, glycidyl ether crotonate, and glycidyl ether isocrotonic acid. . In addition, examples of the acrylic chloride compound include acrylic chloride, methacrylic chloride, and allyl chloride. The addition amount of these ethylenically unsaturated compounds or acrylic acid chloride is preferably from 0.05 to 1 mol equivalent, more preferably from 0.1 to 0.8 mol, per carboxyl group in the acrylic copolymer. Is equivalent. If the added amount is less than 0.05 molar equivalent, the photosensitive characteristics become poor, and it becomes difficult to form a pattern. On the other hand, when the added amount is larger than 1 molar equivalent, the development solubility of the unexposed portion is lowered and the hardness of the coating film is undesirably lowered.

These photosensitive resins function as a polymer binder, but may also contain a non-photosensitive polymer as a polymer binder component. Specific examples include polyvinyl alcohol, polyvinyl butyral, methacrylate polymer, acrylate polymer, acrylate-methacrylate copolymer, α-methylstyrene polymer, and butyl methacrylate resin.

Specific examples of the photopolymerization initiator used in the present invention include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamino) benzophenone,
4,4-dichlorobenzophenone, 4-benzoyl-4
-Methylphenylketone, dibenzylketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenyl-2-phenylacetone, 2-
Hydroxy-2-methylpropiophenone, pt-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-
Isopropylthioxanthone, diethylthioxanthone, benzyl, benzyldimethylketanol, benzyl-methoxyethylacetal, benzoin, benzoinmethylether, benzoinbutylether, anthraquinone, 2-t-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benz Anthrone, dibenzazosuberone, methyleneanthrone, 4-azidobenzalacetophenone, 2,
6-bis (p-azidobenzylidene) cyclohexanone, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-dibutadione-2- (o-methoxycarbonyl) oxime,
-Phenyl-propanedione-2- (o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-
Phenyl-3-ethoxy-propanetrione-2- (o
-Benzoyl) oxime, Michler's ketone, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone, naphthalenesulfonyl chloride,
Quinoline sulfonyl chloride, N-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzothiazole disulfide, triphenylphosphine, camphorquinone, carbon tetrabromide, tribromophenyl sulfone, benzoin peroxide,
Examples include a combination of a photoreducing dye such as eosin and methylene blue and a reducing agent such as ascorbic acid and triethanolamine. In the present invention, one or more of these can be used.

The photopolymerization initiator is added in an amount of 0.5 to 50% by weight based on the sum of the acrylic copolymer having a carbonyl group and an ethylenically unsaturated group in the side chain and the photoreactive compound. More preferably, it is 2 to 25% by weight. If the amount of the photopolymerization initiator is too small, the photosensitivity becomes poor, and if the amount of the photopolymerization initiator is too large, the residual ratio of the exposed portion may be too small.

As the photosensitive organic component, styrene,
It is also preferable to use an oligomer or polymer containing 10% by weight or more of at least one of halogenated styrene, α-methylstyrene, and halogenated α-methylstyrene. It is also preferable to use, as the photosensitive organic component, a monomer containing 10% by weight or more of a (meth) acrylate containing a benzene ring, or an oligomer or polymer obtained by polymerizing a composition containing 10% by weight or more of the monomer. Further, it is also preferable to use, as the photosensitive organic component, a monomer, oligomer or polymer containing 10% by weight or more of a (meth) acrylate containing a benzene ring substituted with a chlorine or bromine atom. Furthermore, as a photosensitive organic component, a sulfur atom,
It is preferable to use a photosensitive organic component having a total content of chlorine atoms and bromine atoms of 5% by weight or more.

In the present invention, it is preferable to add an ultraviolet (UV) light absorber to the photosensitive resin and the ceramic powder for forming a via hole in the green sheet. High resolution can be obtained by adding a light absorbing agent having a high ultraviolet absorbing effect. That is, usually, the ceramic powder alone hardens light to an unnecessary part, and it becomes impossible to form a via hole even if developed, or the roundness is greatly reduced. This is because the scattered ultraviolet light is absorbed or weakened and reaches the light-shielded portion by the exposure mask. Therefore, the addition of the ultraviolet light absorber substantially prevents the scattered light from wrapping around, prevents the photosensitive resin from being hardened in the mask portion, and forms a pattern corresponding to an exposure mask.

350 to 450 nm as an ultraviolet absorber
Inorganic powders or organic pigments having a high UV absorption coefficient in the above wavelength range are preferably used. As the inorganic powder, cobalt oxide Co ₂ O ₃ , CoO, iron oxide Fe ₂ O
₃ , oxides such as chromium oxide Cr ₂ O ₃ , manganese oxide MnO ₂ , copper oxide Cu ₂ O, CuO, titanium oxide TiO ₂ , titanium carbide TiC, tungsten carbide WC, zirconium carbide ZrC, silicon carbide SiC, niobium carbide NbC Such as carbide, titanium boride TiB ₂ , zirconium boride ZrB _2, etc., titanium nitride Ti
N, nitrides such as zircon nitride ZrN and tantalum nitride TaN, and carbon (C). Of these, preferred inorganic powders are carbon and carbide, which can form a sharp pattern without bleeding, and can form a via hole finely without a difference in upper and lower diameters. In particular, when carbon is fired in an oxygen-containing atmosphere, carbon is volatilized as a carbonized gas, so that deterioration of insulation and dielectric properties as a ceramic substrate can be minimized, which is preferable.

These inorganic powders can be used as a composite powder of two or more of oxides, nitrides, and carbides, but are selected within a range that does not degrade the insulating and dielectric properties of the ceramic substrate. Is preferred.
The addition amount of the inorganic powder is preferably 0.01 to 5% by weight. If the amount is less than 0.01% by weight, the effect of adding the ultraviolet absorbent is reduced, and if it exceeds 5% by weight, the substrate characteristics are undesirably deteriorated. More preferably, it is 0.05 to 1% by weight.

As the organic pigment, various pigments having a high absorption light coefficient can be preferably used. Specifically, azo dyes, quinoline dyes, aminoketone dyes, anthraquinone dyes and the like can be used. The addition amount is 0.01 to 5 for the same reason as in the case of the inorganic powder.
A range of weight% is preferred. Since the organic pigment does not remain in the ceramic substrate after firing like carbon, the deterioration of the substrate characteristics due to the light absorbing agent can be reduced. More preferably, 0.
It is 0.5 to 2% by weight.

In the present invention, Pb, Bi, Fe, Ni, M contained in the ceramic powder or the ultraviolet absorber are used.
In some cases, metals such as n, Co, and Mg and oxides thereof react with carboxyl groups of the photosensitive polymer contained in the paste, causing the paste to gel in a short time and become a lump and cannot be printed as a paste. This is presumed to be an ionic cross-linking reaction between the photosensitive polymer and the above-mentioned metal or oxide powder. In order to prevent such a cross-linking reaction, not only the photosensitive polymer but also a photopolymerization initiator or a plasticizer is used. It is preferable to add a compound (stabilizer) that does not adversely affect the gelation to prevent gelation. That is, it is preferable to stabilize the ceramic green sheet by subjecting the powder to a surface treatment with a compound having an effect of forming a complex with a metal or oxide powder causing a gelling reaction or forming a salt with an acid functional group.

As a stabilizer satisfying the above requirements, a triazole compound can be preferably used. Among the triazole compounds, benzotriazole works particularly effectively. Hexamethylenetetraamine, lithium naphthenate (Li), and the like are also effective in suppressing gelation.

The method of surface-treating a metal powder and a metal oxide powder in a ceramic powder or an ultraviolet absorber using benzotriazole is as follows. That is, a predetermined amount of benzotriazole is dissolved in an organic solvent such as methyl acetate, ethyl acetate, ethyl alcohol, and methyl alcohol, and immersed in a solution for 1 to 24 hours so that these powders can be sufficiently immersed. Is preferred. After immersion, the powder is preferably air-dried, preferably at 20 to 30 ° C., and the solvent is evaporated to obtain a powder which has been subjected to a triazole treatment.

The ratio of the stabilizer used in the present invention (stabilizer / metal and metal oxide in ceramic powder or ultraviolet absorber) is preferably 0.2% to 4% by weight.
Further, the content is preferably 0.4 to 3% by weight. 0.2
When the amount is less than the weight%, there is no effect in preventing the crosslinking reaction of the polymer, and the polymer is easily gelled in a short time. On the other hand, if the content exceeds 4% by weight, the amount of the stabilizer becomes too large, and it becomes difficult to remove the binder such as the polymer binder and the stabilizer during firing of the green sheet in a non-oxidizing atmosphere, and the characteristics of the substrate deteriorate. .

In the present invention, it is also preferable to add a photoreactive compound, a sensitizer, a thermal polymerization inhibitor, a plasticizer, an antioxidant, a dispersant, an organic or inorganic precipitation inhibitor to the ceramic green sheet. Done.

The photoreactive compound is added to improve the sensitivity. The photoreactive compound used in the present invention may be a compound having a photoreactive carbon-carbon unsaturated bond, and specific examples thereof include allyl acrylate, benzyl acrylate, butoxy acrylate,
Butoxyethyl acrylate, butoxytriethylene glycol acrylate, cyclohexyl acrylate,
Dicyclopentenyl acrylate, dicyclopentenyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, heptadecafluorodecyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate,
Isodecyl acrylate, isooctyl acrylate,
Lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluoropentyl acrylate, phenoxyethyl acrylate,
Stearyl acrylate, trifluoroethyl acrylate, allyl cyclohexyl diacrylate, bisphenol A diacrylate, 1,4-butanediol acrylate, 1,3-butylene glycol diacrylate,
Ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylolpropane tetraacrylate, glycerol diacrylate, methoxycyclohexyl diacrylate, neo Pentyl glycol diacrylate, propylene glycol diacrylate, polypropylene glycol diacrylate, triglycerol diacrylate,
Trimethylolpropane triacrylate and the above acrylate converted to methacrylate, γ-methacryloxypropyltrimethoxysilane, 1-vinyl-
In the present invention, one or more of these photoreactive compounds can be used.

The acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain is usually used in an amount of 0.1 to 10 times by weight based on the photoreactive compound. If the amount of the acrylic copolymer is too small, the viscosity of the slurry becomes low, and the uniformity of dispersion in the slurry may be reduced. On the other hand, if the amount of the acrylic copolymer is too large, the solubility of the developer in the unexposed portions becomes poor.

A sensitizer is added to improve high sensitivity. Specific examples of the sensitizer include 2,3-bis (4-
Diethylaminobenzal) cyclopentanone), 2,6
-Bis (dimethylaminobenzal) cyclohexanone,
2,6-bis (4-dimethylaminobenzal) -4-methylcyclohexanone, Michler's ketone, 4,4-bis (diethylamino) -benzophenone, 4,4-bis (dimethylamino) chalcone, 4,4-bis (diethylamino) ) Chalcone, p-dimethylaminocinnamylidene indanone, p-dimethylaminobenzylidene indanone, 2- (p-dimethylaminophenylenevinylene)-
Isonaphthol, 1,3-bis (4-dimethylaminobenzal) acetone, 1,3-carbonyl-bis (4-diethylaminobenzal) acetone, 3,3-carbonyl-bis (7-diethylaminocoumarin), N- Phenyl-N-ethylethanolamine, N-phenylethanolamine, N-tolyldiethanolamine, N-phenylethanolamine, isoamyl dimethylaminobenzoate, isoamyl diethylaminobenzoate, 3-phenyl-5-benzoylthio-tetrazole, 1-phenyl −
5-ethoxycarbonylthio-tetrazole and the like. In the present invention, one or more of these can be used. Some sensitizers can also be used as photopolymerization initiators. When a sensitizer is added to the ceramic green sheet of the present invention, the addition amount is usually 0.1 to 60% by weight based on an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in a side chain. More preferably, it is 0.5 to 30% by weight. If the amount of the sensitizer is small, the effect of improving the photosensitivity is not exhibited, and if the amount of the sensitizer is too large, the residual ratio of the exposed portion may be too small.

The thermal polymerization inhibitor is added to improve the thermal stability during storage. Specific examples of the thermal polymerization inhibitor include hydroquinone, N-nitrodiphenylamine,
Examples include phenothiazine, pt-butylcatechol, N-phenylnaphthylamine, 2,6-di-t-butyl-p-methylphenol, chloranil, pyrogallol, and the like. When a thermal polymerization inhibitor is added, the addition amount is usually 0.1 to 20% by weight, more preferably 0.5 to 20% by weight, based on the acrylic copolymer having an ethylenically unsaturated group in a side chain. 10% by weight. If the amount of the thermal polymerization inhibitor is small, the effect of improving the thermal stability during storage is not exhibited, and if the amount of the thermal polymerization inhibitor is too large, the residual ratio of the exposed portion may be too small. .

Specific examples of the plasticizer include dibutyl phthalate, dioctyl phthalate, polyethylene glycol, glycerin and the like.

The antioxidant is added to prevent oxidation of the acrylic copolymer during storage. Specific examples of the antioxidant include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-4-ethylphenol, and 2,2-methylene-bis. -(4-methyl-6-t-butylphenol), 2,2
-Methylene-bis- (4-ethyl-6-t-butylphenol), 4,4-bis- (3-methyl-6-t-butylphenol), 1,1,3-tris- (2-methyl-
6-t-butylphenol), 1,1,3-tris-
(2-methyl-4-hydroxy-t-butylphenyl)
Butane, bis [3,3-bis- (4-hydroxy-3-
[t-butylphenyl) butyric acid] glycol ester, dilaurylthiodipropionate, triphenylphosphite, and the like. When the antioxidant is added, the amount of the antioxidant is usually 0.0% with respect to the total of the ceramic powder, the acrylic copolymer having an ethylenically unsaturated group in the side chain, the glass frit and the photopolymerization initiator.
It is 1 to 5% by weight, more preferably 0.1 to 1% by weight. If the amount of the antioxidant is small, the effect of preventing oxidation of the acrylic copolymer during storage cannot be obtained, and if the amount of the antioxidant is too large, the residual ratio of the exposed portion may be too small.

The preferred composition of the slurry for forming a ceramic green sheet of the present invention is preferably selected in the following range. (a) ceramic powder; 70 to 95% by weight (b) photosensitive resin; 25 to 10% by weight (c) UV absorber: 0 to 5% by weight (preferably 0.05 to 5% by weight)

Also, the ceramic green sheet is
Ceramic powder, UV absorber, acrylic copolymer having carboxyl group and ethylenically unsaturated group in side chain,
When a photopolymerization initiator is contained, it is preferable to select a preferred composition of the slurry for forming a ceramic green sheet in the following range. (A) ceramic powder; 70 to 95% by weight; (b) an acrylic copolymer (and a photoreactive compound) having a carboxyl group and an ethylenically unsaturated group in a side chain;
0 to 5% by weight (c) Photopolymerization initiator; 2 to 25% by weight with respect to (b) (d) UV absorber; 0.01 to with respect to (a)
5% by weight

When each component is in the above-mentioned range, ultraviolet rays are well transmitted at the time of exposure, the function of photo-curing is sufficiently exhibited, and the occurrence of a residual film at the unexposed portion during subsequent development can be almost eliminated. Via holes having roundness can be formed. In particular, by setting the acrylic copolymer (and the total amount thereof when a photoreactive compound is used) as the component (b) within this range, the sintered body after firing becomes dense and has a high strength. There is an advantage that a ceramic substrate can be obtained.

The slurry for forming a ceramic green sheet of the present invention can be produced by dissolving a photosensitive resin in an organic solvent and dispersing a ceramic powder and an ultraviolet absorber in this solution. When the ceramic green sheet contains a ceramic powder, an ultraviolet absorber, an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain, and a photopolymerization initiator, the carboxyl group is added to the side chain. And an acrylic copolymer having an ethylenically unsaturated group and a photoinitiator are dissolved in an organic solvent, and a ceramic powder and an ultraviolet absorber are dispersed in this solution. The organic solvent used at this time may be any as long as it can dissolve a mixture of a photosensitive resin or an acrylic copolymer having an ethylenically unsaturated group in a side chain and a photopolymerization initiator. For example, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl ethyl ketone, dioxane, acetone, cyclohexanone, cyclopentanone, isobutyl alcohol, isopropyl alcohol, tetrahydrofuran, dimethyl sulfoxide, γ-butyrolactone, toluene, trichlorethylene, methyl isobutyl Ketone, isophorone and the like and an organic solvent mixture containing at least one of them are used. Further, when the photoreactive compound is used, the photoreactive compound can dissolve a mixture of a photosensitive resin or an acrylic copolymer having an ethylenically unsaturated group in a side chain and a photopolymerization initiator. In the case of the above, each of the above components may be dissolved in the photoreactive compound instead of the above organic solvent. In this case, the above-mentioned organic solvent can also be added for adjusting the viscosity.

As a method of adding the ultraviolet light absorber, the ceramic powder and the ultraviolet light absorber are wet-mixed in an aqueous solution, and then mixed.
There is a method of drying. More preferably, a method of uniformly mixing and dispersing ceramic powder in an aqueous solution of an inorganic salt so as to have a predetermined addition amount, followed by drying and firing to prepare a mixed powder. By this method, a so-called capsule-like powder in which the surface of each ceramic powder is coated with an inorganic film or a fine powder can be produced. For example, when adding iron oxide or cobalt oxide as an ultraviolet absorber, after dispersing the ceramic powder in an aqueous solution of iron chloride or cobalt chloride, the mixture is dried with stirring, and dried at 400 to 8%.
By performing heat treatment at 00 ° C., a film of iron oxide or cobalt oxide can be formed on the surface of the ceramic powder. CVD when adding carbon as UV absorber
It is more preferable to form a uniform carbon film on the surface of the ceramic powder by a (chemical vapor deposition) method or the like. Also,
When an organic pigment is added as an ultraviolet absorber, the ceramic powder is homogeneously mixed and dispersed in a solution in which the organic pigment is dissolved, and then dried to form an organic pigment film on the surface of each particle of the ceramic powder. The effect of the agent is further enhanced.

Further, if necessary, an organic solvent, a stabilizer, a sensitizer, a thermal polymerization inhibitor, a plasticizer, an antioxidant, a dispersant, an organic or inorganic suspending agent, and the like are added, and a ball mill or an atomizer is added. The mixture is ground and mixed with a lighter for, for example, 12 to 48 hours to prepare a slurry.

Further, the above-mentioned organic solvent is added as needed to adjust the viscosity of the slurry. The preferred viscosity is 1500 to 20,000 cps (centipoise), and within this range, the thickness of the sheet can be adjusted uniformly. Using a doctor blade obtained slurry continuously on a film such as a polyester film to a thickness of 0.01 to
Formed to 0.5 mm. Then, the mixture is heated at a temperature of 80 to 120 ° C. for 10 minutes to 3 hours to evaporate the solvents to form a ceramic green sheet. This sheet is cut into a predetermined shape.

The thickness of the ceramic green sheet of the present invention is usually in the range of 5 to 500 μm, preferably 30 to 300 μm. If it exceeds 500 μm, it will not transmit sufficiently to exposure to ultraviolet light, and the effect of photocuring will be weakened.
If the thickness is less than 5 μm, it becomes difficult to handle the green sheet.

The ceramic green sheet is exposed using a usual photomask method. As the active light source used at this time, for example, ultraviolet rays, electron beams, X-rays and the like can be mentioned, and among them, ultraviolet rays are preferable, and as the light source, for example, low pressure mercury lamp, high pressure mercury lamp, halogen lamp, germicidal lamp, etc. Can be used. Among these, an ultra-high pressure mercury lamp is preferable. Exposure conditions vary depending on the thickness of the green sheet and the like, but it is preferable to perform exposure for 1 to 30 minutes using an ultra-high pressure mercury lamp having an output of 5 to 100 mW / cm ² . As a method of exposing both sides of the sheet, there is a method of simultaneously exposing from both upper and lower surfaces of the sheet, or a method of exposing one side of the sheet and then inverting the front and back of the sheet and exposing the opposite side in the same manner.

After exposure, development is carried out using a developing solution to remove portions that have not been photocured, to form a so-called negative pattern, and to form a via hole having a diameter of, for example, 0.005 to 0.2 m.
m is a via hole pitch, for example, 0.01 to 5.0 mm.
At intervals. As a developing method, an immersion method or a spray method can be used. As the developer, an organic solvent in which a mixture of the acrylic copolymer having an ethylenically unsaturated group in the side chain, a photoreactive compound, and a photopolymerization initiator can be used. In addition, water may be added to the organic solvent as long as the dissolving power is not lost. When a carboxyl group is present in the side chain of the acrylic copolymer, development can be performed with an aqueous alkali solution. As the alkali aqueous solution, a metal alkali aqueous solution such as a sodium hydroxide or calcium hydroxide aqueous solution can be used, but it is preferable to use an organic alkali aqueous solution since the alkali component can be easily removed during firing. Specific examples of the organic alkali include tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, monoethanolamine,
And diethanolamine. The concentration of the alkaline aqueous solution is usually 0.01 to 10% by weight, more preferably 0.1 to 5% by weight. If the alkali concentration is too low, the unexposed portions are not removed, and if the alkali concentration is too high, the exposed portions may be peeled off and corroded, which is not preferable.

Next, the green sheet is fired in a firing furnace. The firing atmosphere and temperature vary depending on the type of the green sheet, but firing is performed in air, nitrogen, hydrogen, or the like. As the firing furnace, a batch-type firing furnace or a belt-type continuous furnace can be used. The firing temperature is usually from 800 to 1600C.

In the ceramic green sheet of the present invention, it has been found that a via hole can be formed with high accuracy by setting the total light transmittance to 30% or more. More preferably, it is 40% or more, and still more preferably 50% or more.
If the total light transmittance is less than 30%, it becomes difficult to form fine holes according to the photomask pattern.

In the ceramic green sheet of the second invention of the present application, it has been found that by setting the regular transmittance to 2% or more, via holes can be formed with high accuracy.
More preferably, it is at least 5%, most preferably at least 50%. If the regular transmittance is less than 2%, the hole diameter difference of the via hole in the film thickness direction becomes large, and it becomes difficult to form a straight via hole.

The total light transmittance and the normal transmittance vary depending on the kind of organic components and inorganic particles used, the mixing ratio, and other additives. To increase the total light transmittance, the total light transmittance is required. It is effective to use an organic component and an inorganic component having a high content. Further, in order to increase the straight transmissivity, it is necessary that each component in the organic component is more uniformly dispersed. As for the inorganic particles, it is important that the total light transmittance of the inorganic particles is high, the composition inside the powder is uniform, and it is important that there is no composition unevenness such as bubbles.

Further, it is preferable to match the average refractive index of the glass fine particles used as the inorganic particles with the average refractive index of the organic component, because the total light transmittance and the normal transmittance are improved. Using glass fine particles having an average refractive index of 1.55 to 1.8, a photoreactive monomer having a refractive index of 1.55 to 1.8 is contained as an organic component, and the average refractive index is set to the average refractive index of the inorganic particles. It is effective to approach.

[0072]

The present invention will be described below in detail with reference to examples. In the following description, the amounts used and the mixing ratios are all expressed in weight%.

Examples 1 to 5 A. Ceramic component (a) Alumina powder; refractive index 1.776, granular, average particle size (D50) 2.5 μm (b) High melting point glass powder; refractive index 1.584, sphere ratio 80 number%, average particle size ( D50) 2.5 μm, 10% by volume particle diameter (D10) 1.3 μm, 90% by volume particle diameter (D
90) 5.0 μm, maximum particle size 13.1 μm, specific surface area 2.41 m ² / g, glass transition point 652 ° C., softening point 74
6 ° C. spherical powder. The composition is Al ₂ O ₃ : 34.5, SiO
_{2: 38.2, B 2 O 3} : 9.2, BaO: 5.1, M
gO: 4.8, CaO: 4.4, TiO 2: 2.1 wt% (c) mixed powder of alumina powder 75 parts by weight of a high melting point glass frit 25 parts by weight of (b) in (a), the refractive The same composition as the high melting point glass powder having a ratio of 1.729 (d) and (b), D50 is 2.6 μm, D10 is 0.9 μm, and D90 is 7.4 μm.
m, a non-spherical powder having a maximum particle size of 22 μm and a specific surface area of 2.32 m ² / g. (e) The same composition as the high melting point glass powder of (b), D50 is 2.
Spherical powder having a particle size of 1 μm, D10 of 1.0 μm, D90 of 3.4 μm, maximum particle diameter of 7.8 μm, specific surface area of 3.32 m ² / g and tap density of 1.1 g / cc. (f) Average particle size (D50) is 2.3 μm and refractive index is 1.56
Cordierite powder.

B. UV absorber Organic pigment; Azo-based dye: Sudan IV, chemical formula: C ₂₄ H ₂₀ N ₄ O, molecular weight: 380.45

C. Polymer binder (a) 0.4 equivalent to a copolymer consisting of 40 mol% of methacrylic acid, 30 mol% of methyl methacrylate and 30 mol% of styrene (40 equivalents to methacrylic acid)
(Corresponding to mol%) of glycidyl acrylate. The acid value of the polymer was 95. The number average molecular weight ((Mn)) of the polymer is 120.
00, the weight average molecular weight (Mw) is 33,000, and the Z average molecular weight (Mz) is 65,000, which indicates the degree of dispersion (Mw
/ Mz) ratio was 2.75. (b) a weight-average molecular weight of 30,000 obtained by adding 0.4 equivalent of glycidyl methacrylate to a copolymer composed of 40 mol% of methacrylic acid, 40 mol% of methyl methacrylate and 20 mol% of styrene; A photosensitive polymer having a value of 101.

D. Photoreactive compound (photosensitive monomer) (a) trimethylol propane triacrylate _{(b) MGP400: X 2 H} -CH (CH 3) -CH 2 - (OCH 2 CH (CH 3)) n -N
X ₂ where _{X = -CH 2 CH (OH)} -CH 2 O-CO-C (CH 3) = CH 2 n = 2~10

E. Photopolymerization initiator (a) 2-Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (b) IC-369 Irgacure369 (manufactured by Ciba Geigy) 2-benzyl-2-dimethylamino- 1- (4-morpholinophenyl) butanone-1

F. Sensitizer I; 2,4-diethylthioxanthone Sensitizer II; ethyl p-dimethylaminoaminobenzoate

G. Solvent 9: 1 mixed solvent of methyl ethyl ketone and n-butyl alcohol

H. Plasticizer dibutyl phthalate

I. A cationic dispersant or "florene" (G-700, maleic acid partial ester type) was added in an amount of 1.5% by weight with respect to the inorganic particles.

<Preparation and Evaluation of Green Sheet> a. Preparation of UV Absorbent Additive Powder A predetermined amount (based on ceramic powder) of an ultraviolet absorber is weighed, and a 50% solution of a cationic dispersant (solvent is IPA) is added to a solution dissolved in isopropyl alcohol (IPA). The mixture was stirred homogeneously with a homogenizer. Next, a predetermined amount of the ceramic powder was added to this solution, and while the mixture was homogeneously dispersed and mixed, 150 parts were added using a rotary evaporator.
Dry at ℃ and evaporate the IPA. In this way, a powder was obtained in which the surface of the ceramic powder was uniformly coated (capsulated) with the organic dye film. The coating thickness was 0.5 nm.

B. Preparation of Organic Vehicle The solvent and polymer binder were mixed and heated at 60 ° C. with stirring to dissolve all polymers. Then, the solution was cooled to room temperature, and a photopolymerization initiator, a photoreactive compound, a sensitizer, and a plasticizer were added and dissolved. Thereafter, the solution was vacuum degassed by a stirrer and then filtered through a 250-mesh filter to prepare an organic vehicle.

C. Preparation of Slurry To prepare a slurry, the above organic vehicle was mixed with a ceramic powder treated with a light absorbing agent, and wet-mixed with a ball mill for 20 hours to prepare a slurry. Table 1 shows the prepared compositions.

D. Preparation of Green Sheet Molding was performed by a doctor blade method at a molding speed of 0.2 m / min with a spacing between the polyester carrier film and the blade of 0.1 to 0.8 mm in a room shielded from ultraviolet rays. Table 1 shows the thickness of the obtained green sheet.

E. Measurement of total light transmittance and normal light transmittance The light transmittance was measured using a spectrophotometer (UV) manufactured by Shimadzu Corporation.
-3101PC). The measurement conditions are as follows.

Sample thickness: 40 μm Sample cell: quartz Slit width: 7.5 nm Measurement speed: SLOW (about 100 nm / min) Light source: halogen lamp Measurement wavelength: 360 to 850 nm White plate: BaSO ₄ (sample side) Secondary white plate: BaSO ₄ (Reference side) Injection: 0 ^o Sample room: Multipurpose large sample room unit (Shimadzu MPC-3100) Integrating sphere: 60φ integrating sphere Detector: Photomal and PbS cell

After the photosensitive paste is applied on the quartz cell so as to have a thickness of 40 μm after drying, the quartz cell is placed on the sample to prepare a measurement sample.

After measuring the total light transmittance Tt (%) under the above-mentioned specifications and conditions, the portion for measuring the straight light of the integrating sphere (white plate: the portion attached to the exit window) is removed, and the light of the straight light is removed. Is not detected, and the diffuse transmittance Td
(%) (Diffuse transmittance, which is a ratio of light transmitted without going straight due to scattering or the like) was measured. Further, the normal transmittance Tn (%) was calculated by the following equation.

[0090]

## EQU1 ## Tn = (Tt-Td) / Ttx100

G. Exposure / Development The green sheet produced above was cut into 100 mm squares, dried at a temperature of 80 ° C. for 1 hour, and the solvent was evaporated.
Next, the mask via diameter is 120 μm and the via hole pitch is 0.3.
6.3 mm from both sides of the sheet using a chrome mask
Ultraviolet light exposure was performed using an ultra-high pressure mercury lamp having an output of mW / cm ² .
Next, development was carried out with a 0.5% by weight aqueous solution of monoethanolamine kept at 25 ° C., and the via holes that were not photocured were washed with water using a spray. Table 1 shows the exposure amount at this time.

H. Observation of cross section of via hole The cross section of the via hole formed above was observed with a scanning electron microscope. Table 1 shows the obtained via hole diameter d ₁ on the sheet surface and the via hole diameter d _{2 at} which the difference in the hole diameter in the sheet thickness direction is maximized.

The cross-sectional shapes of the formed via holes were all straight with a difference in hole diameter of 20% or less.

[0094]

[Table 1]

[0095]

According to the ceramic green sheet of the present invention, via holes and through holes can be formed very easily, accurately and uniformly, and fine holes can be surely formed at low cost. Further, by using the present invention to make the via hole diameter 0.1 mm or less, preferably 0.05 mm or less, printing of the conductor paste in the via hole becomes easy, and insufficient filling or dropout is prevented.

Claims (10)

[Claims] 1. A ceramic green sheet containing inorganic particles and a photosensitive organic component, and having a total light transmittance of 30% or more. 2. The ceramic green sheet according to claim 1, wherein the total light transmittance is 40% or more. 3. The ceramic green sheet according to claim 2, having a total light transmittance of 50% or more. 4. A ceramic green sheet containing inorganic particles and a photosensitive organic component and having a regular transmittance of 2% or more. 5. The ceramic green sheet according to claim 4, wherein the regular transmittance is 5% or more. 6. The ceramic green sheet according to claim 1, comprising 60 to 90% by weight of inorganic particles and 10 to 40% by weight of a photosensitive organic component. 7. The method according to claim 1, wherein the inorganic particles are at least one selected from the group consisting of alumina, zirconia, magnesia, beryllia, mullite, cordierite, spinel, forsterite, anorthite, cellian, silica and aluminum nitride. 7. The ceramic green sheet according to any one of items 6 to 6. 8. The composition according to claim 1, wherein the inorganic particles have a composition range of 30 to 70% by weight of SiO _2, 5 to 25% by weight of Al ₂ O _3, 5 to 25% by weight of CaO, and _{3 to} 50% by weight of B ₂ O _{3 in} terms of oxide. Selected from the group consisting of alumina, zirconia, magnesia, beryllia, mullite, cordierite, spinel, forsterite, anorthite, celsian, silica, and aluminum nitride. 7. The ceramic green sheet according to claim 1, which is a raw material mixture with at least one kind of inorganic filler powder obtained. 9. The inorganic particles having an average refractive index of 1.55.
The ceramic green sheet according to any one of claims 6 to 8, wherein the ceramic green sheet is an inorganic particle having a particle size of from 1.8 to 1.8. 10. The ceramic green sheet according to claim 1, comprising 0.05 to 5% by weight of an ultraviolet absorber.