JP3405199B2 - Photoconductive paste - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive conductive paste for forming a conductor pattern on a ceramic circuit board.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for miniaturization, high density, high definition and high reliability in a multilayer substrate for mounting a large number of highly integrated LSIs and various electronic components. In particular, various methods have been proposed as miniaturization of a conductor circuit pattern (including a signal layer and a power supply layer) is essential for miniaturization and high density.

Typical methods include a thin film method, a plating method and a thick film method. The thin film method enables high definition up to 20 μm resolution by applying photolithography technology by forming by sputtering, vapor deposition, etc., but the conductor film by this method requires a long time to increase the film thickness. Since there is a limit such as that, only a thin film can be obtained, and as a result, the impedance of the circuit becomes high. Further, the plating method has a problem that it is difficult to form a thick film passive element such as a resistor in the firing process.

On the other hand, in the thick film method, a film is formed by a screen printing method. However, in the printing method, even if the screen performance, squeeze hardness, printing speed, dispersibility, etc. are optimized, the width of the conductor pattern can only be reduced to about 100 μm, and there is a limit to fine patterning.

Under these circumstances, in order to improve the drawbacks of the printing method, JP-A-63-292504 and JP-A-2-2688 are proposed.
70, JP-A-3-171690 and JP-A3-1.
As described in JP-A-80092, the composition of the conductor paste was studied, the photosensitive resin was added, and a fine pattern was formed by the photolithography method, and optimization of the particle diameter of the metal powder was examined. However, it was not sufficient to satisfy both formation of a fine pattern and reduction of resistance at the same time.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photosensitive conductive paste capable of forming a fine pattern and providing a circuit pattern having a low resistance.

[0007]

The object of the present invention is (a)
Conductive powder containing at least one selected from the group consisting of Au, Ag, Pd and Pt, (b) acrylic copolymer having an acid value of 40 to 200, (c) photoreactive compound , ( d) photopolymerization. Initiator and (e) glass transition point 300-500
Achieved by a photosensitive conductive paste characterized by containing a glass frit of ° C.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, according to the present invention, a conductive paste is provided with photosensitivity. When this is used, a thick film conductor circuit pattern is finely formed by using a photolithography technique and a low resistance conductor film is formed. Can be formed efficiently.

The conductive powder used in the present invention is A
A conductor powder containing at least one selected from the group consisting of u, Ag, Pd and Pt, and having a low resistance is used to reduce transmission loss at high frequencies. Au, Ag, Pd and Pt can each be used alone or as a mixed powder. For example, Ag (30-80) -Pd (70-2
0), Ag (40-70) -Pd (60-10) -Pt.
(5-20), Ag (30-80) -Pd (60-1
0) -Cr (5-15), Pt (20-40) -Au
(60-40) -Pd (20), Au (75-80)-
Pt (25-20), Au (60-80) -Pd (40
-20), Ag (40-95) -Pt (60-5), P
A binary or ternary mixed noble metal powder such as t (60-90) -Rh (40-10) (the above () represents weight%) is used. Among the above, those to which Cr or Rh is added are preferable because the high temperature characteristics can be improved.

The average particle diameter of these noble metal conductive powders is preferably 0.5 to 5 μm. If the particle size is less than 0.5 m, the light does not smoothly pass through the printed film during exposure to ultraviolet light, making it difficult to form a fine pattern having a conductor line width of 60 μm or less. On the other hand, if the particle diameter exceeds 5 μm and becomes large, the surface of the printed circuit pattern becomes rough, the pattern accuracy is lowered, and noise is generated. Further, a conductive powder having a specific surface area of 0.1 to ³ m ² / g is preferably used. If the specific surface area is less than 0.1 m ² / g, the accuracy of the circuit pattern will decrease. On the other hand, if it exceeds 3 m ² / g, the surface area of the powder becomes too large and the ultraviolet rays are scattered, so that the exposure is not sufficiently performed and the pattern accuracy is lowered.

The noble metal conductive powder may have a flake (plate, cone, rod) shape or a spherical shape, but a spherical shape is preferable from the viewpoint of no aggregation. The spherical shape reduces the scattering of ultraviolet rays at the time of exposure, so that a highly accurate pattern can be obtained and the irradiation energy can be reduced.

There is a range of conductive powder that is more preferable for satisfying formation of a fine pattern and reduction of resistance. That is, in order to obtain a fine circuit pattern of 10 to 40 μm after the development of the conductive pattern, the light is sufficiently scattered without being scattered at the time of exposure to ultraviolet rays, and the fine particle pattern is 10 to 40 μm after development. 4 μm and specific surface area of 0.1 to 1.5 m ²
/ G is preferable. More preferably, the particle size is 0.8 to 4 μm, and the specific surface area is 0.15 to 0.8 m ² / g.
Is. Within this range, no residual film of the conductor film is generated in the unexposed portion during development, and a highly accurate circuit pattern can be obtained.

The acrylic copolymer used in the present invention is a polymer binder component and can be produced by copolymerizing an unsaturated carboxylic acid and an ethylenically unsaturated compound.

Specific examples of unsaturated carboxylic acids include:
Examples thereof include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinylacetic acid, and acid anhydrides thereof. 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,
Examples thereof include, but are not limited to, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, styrene, p-methylstyrene, o-methylstyrene, m-methylstyrene and the like. A copolymer having good thermal decomposability can be obtained by including at least methyl methacrylate from the above ethylenically unsaturated compounds as the main polymerization component of these acrylic main chain polymers.

By adding an ethylenically unsaturated group to the side chain of the polymer binder shown above, it can be used as a photosensitive polymer. Examples of the side chain ethylenically unsaturated group include a vinyl group, an allyl group, an acryl group and a methacryl group. As a method of adding such a side chain to the acrylic copolymer, a method of making an addition reaction of an ethylenically unsaturated compound or a chloride acrylate compound having a glycidyl group with a carboxyl group in the acrylic copolymer is available. is there.

Examples of the ethylenically unsaturated compound having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, α-glycidyl ethyl acrylate, crotonyl glycidyl ether, crotonic acid glycidyl ether, and isocrotonic acid glycidyl ether. Examples of the chloride acrylate compound include chloride acrylate, chloride methacrylate, allyl chloride and the like. Further, as the addition amount of these ethylenically unsaturated compounds or chloride acrylate compounds,
0.0 with respect to the carboxyl group in the acrylic copolymer
5 to 0.8 molar equivalent is desirable, and more preferably 0.
It is 1 to 0.6 molar equivalent. If the addition amount is less than 0.05 molar equivalent, the development allowance is narrow, and the edge of the pattern tends to be poor. If the addition amount is greater than 0.8 molar equivalent, the solubility of the unexposed area in the developing solution decreases. Or the hardness of the coating film becomes low.

The acid value (A
V) is preferably 40 to 200, more preferably 60 to
160. More preferably, it is in the range of 80 to 140. When the acid value is less than 40, the solubility of the unexposed area in the developing solution is lowered and the hardness of the coating film is lowered. On the other hand, when the acid value exceeds 200, the development allowable width is narrow and the cutting of the pattern edge becomes poor.

The photosensitive conductive paste in the present invention may contain a photosensitive polymer other than the above acrylic copolymer or a non-photosensitive polymer as a polymer binder component. Photosensitive polymers include photo-insolubilizing type and photo-solubilizing type. As the photo-insolubilizing type, a suitable polymer is a functional monomer or oligomer having at least one unsaturated group in one molecule. Mixed with a binder, mixed with a photosensitive compound such as an aromatic diazo compound, an aromatic azide compound, or an organic halogen compound with a suitable polymer binder, or obtained by pendant to an existing polymer with a photosensitive group. As a photosolubilizing type, such as a so-called diazo resin such as a photosensitive polymer or a modified one thereof, a condensation product of a diazo amine and formaldehyde, a complex with an inorganic salt of a diazo compound or an organic acid, Mixing quinonediazides with a suitable polymer binder, quinonediazos with a suitable polymer binder Zehnder and allowed to bind, such as phenol, etc. naphthoquinone-1,2-diazide-5-sulfonic acid ester of a novolak resin. The proportion of the acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain contained in the photosensitive polymer binder component is preferably at least 5% by weight, more preferably 20% by weight or more. When the content of the acrylic copolymer is less than 5% by weight, the effect of expanding the development allowable width is small, and the developability is liable to be lowered, which makes it difficult to form a sharp edge portion pattern, which is not preferable.

As the non-photosensitive polymer, polyvinyl alcohol, polyvinyl butyral, methacrylic acid ester polymer, acrylic acid ester polymer, acrylic acid ester-methacrylic acid ester copolymer, α-methylstyrene polymer, butyl methacrylate resin, etc. Can be given.

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 and butoxy. Ethyl acrylate, butoxytriethylene glycol acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, 2-ethylhexyl acrylate, glycerol acrylate, glycidyl acrylate, heptadecafluorodecyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, isodecyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxyethyl acrylate Methoxy ethylene glycol acrylate, methoxy diethylene glycol acrylate, octa fluorosilicone pentyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylate, allylated cyclohexyl diacrylate, bisphenol A diacrylate, 1,4
Butanediol diacrylate, 1,3-butylene glycol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylol Propane tetraacrylate, glycerol diacrylate, methoxycyclohexyl diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate,
Examples thereof include polypropylene glycol diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, those obtained by replacing the above acrylate with methacrylate, γ-methacryloxypropyltrimethoxysilane, and 1-vinyl-2-pyrrolidone. In the present invention, these are one kind or a mixture of two or more kinds,
Alternatively, a mixture with other compounds can be used.

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,
α-amino acetophenone, 4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenyl-2-phenyl Acetophenone, 2-hydroxy-2
-Methylpropiophenone, pt-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyl, benzyldimethylketanol, benzyl-methoxyethylacetal, benzoin, benzoin Methyl ether,
Benzoin butyl ether, anthraquinone, 2-t-
Butyl anthraquinone, 2-amyl anthraquinone, β
-Chloranthraquinone, anthrone, benzanthrone, dibenzosuberone, methyleneanthrone, 4-azidobenzalacetophenone, 2,6-bis (p-azidobenzylidene) cyclohexanone, 2,6-bis (p-
Azidobenzylidene) -4-methylcyclohexanone,
2-Phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-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, quinolinesulfonyl chloride, N-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl Combination of photo-reducing dyes such as disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, carbon tetrabromide, tribromophenyl sulfone, benzoin peroxide, eosin and methylene blue with reducing agents such as ascorbic acid and triethanolamine. And so on. In the present invention, one kind or two or more kinds of these photopolymerization initiators can be used.

The acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in its side chain is preferably used in a weight ratio of 0.1 to 5 times that of the photoreactive compound. More preferably, the amount is 0.3 to 3 times. If the amount of the acrylic copolymer is too small, the viscosity of the paste becomes small, and the uniformity of dispersion in the paste may deteriorate. On the other hand, if the amount of the acrylic copolymer is too large, the solubility of the unexposed area in the developer becomes poor.

Further, the photopolymerization initiator is usually 0.1 to 30% by weight, based on the sum of the acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain and the photoreactive compound. Preferably, 2 to 25% by weight is used. When the amount of the photopolymerization initiator is too small, the photosensitivity becomes poor,
If the amount of the photopolymerization initiator is too large, the residual rate of the exposed area may be too small.

In the present invention, it is necessary that the photosensitive conductive paste further contains glass frit.
It The glass frit acts as a sintering aid for sintering the conductive powder and has the effect of reducing the conductor resistance. The glass transition temperature (Tg) and the glass softening point (Ts) of the glass frit are preferably low, and each is 300 to
The temperature is preferably 500 ° C and 350 to 450 ° C. More preferably, Tg is 350 to 450 ° C. If the Tg is too low, sintering starts before the organic components such as the polymer binder and the monomer evaporate, which is not preferable. Tg
A glass frit having a temperature of more than 500 ° C. is not preferable because it results in poor adhesion to a ceramic substrate when sintered at a temperature of 800 ° C. or less.

As the glass frit, glass type or crystallized glass can be used, but the composition of the frit is Si.
O ₂ , ZrO ₂ , B ₂ O ₃ and LiO ₂ are each 1
˜50% by weight, in addition to these, Al ₂ O ₃ , Ca
_{O, K 2 O, MgO,} Na 2 O, BaO, is that TiO ₂ or ZnO and moderated in the range of 0.5 to 3 wt%, it is possible to more easily adjust the thermal expansion coefficient and the melting point Therefore, it is preferable. More preferably, SiO ₂ is 1
0-40% by weight, 2-25% by weight of ZrO ₂ , B ₂ O ₃
20-40% by weight, BaO 1-40% by weight and L
i ₂ O is contained in an amount of 1 to 10% by weight, and by adopting this composition, the coefficient of thermal expansion and the melting point can be adjusted more easily. Further, it is preferable that the glass phase does not contain 0.2% by weight or more of PbO and CdO.
As the particle size of the glass frit, finer particles are preferable because they melt at a lower temperature. In particular, those having a 50% diameter in the range of 0.6 to 3 μm and a 90% diameter in the range of 1 to 4 μm are preferable because they melt at low temperature and adhere firmly to the ceramic substrate.

The content of the glass frit in the photosensitive conductive paste is preferably 5% by weight or less with respect to the sum of the conductive powder, the polymer binder and the monomer. It is more preferably 3.5% by weight or less. In particular, in order to reduce the resistance of the conductor film in order to reduce high frequency transmission loss, it is necessary to reduce the amount of glass frit. That is, since the glass frit is electrically insulating, its content is 5
If it exceeds 5% by weight, the resistance of the conductor film increases, which is not preferable.

When the ceramic green sheet used for the ceramic multilayer substrate is printed and used for the inner conductor circuit or the power supply layer, the amount of glass frit is preferably 2% by weight or less for the purpose of obtaining a low resistance. Further, when a strong adhesive force is required for the conductor film in the surface layer of the ceramic substrate, it is preferable to add 1 to 5% by weight of glass frit. If it is less than 1% by weight, the effect of adding glass frit is small and it is difficult to obtain a strong adhesive strength.

In the present invention, it is also preferable to add a metal oxide in addition to the above glass frit.
The metal oxide effectively acts as a so-called sintering aid, such as preventing abnormal particle growth of the conductive powder during sintering or delaying the sintering, and as a result, the adhesive force between the conductor film and the ceramic substrate. It has the effect of raising. Specifically, a metal oxide of a metal such as Cu, Cr, Mo, Al or Ni can be used. Since the metal oxide electrically acts as an insulator, it is better to add a small amount, and the total amount of the conductive powder, the polymer binder, the monomer, the glass frit and the metal oxide (both of them are called an inorganic binder) is added. It is preferably 3% by weight or less. If it exceeds 3% by weight, the electric resistance of the conductor film increases, which is not preferable. It is also preferable to use a metal oxide and a metal together.

Examples of the sensitizer usable in the present invention include 2,3-bis (4-diethylaminobenzal) cyclopentanone, 2,6-bis (4-dimethylaminobenzal) cyclohexanone, 2,3 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-dimethylaminophenylvinylene) -isonaphthothiazole,
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-
Examples thereof include trilyldiethanolamine, N-phenylethanolamine, dimethylaminobenzoic acid isoamyl, diethylaminobenzoic acid isoamyl, 3-phenyl-5-benzoylthio-tetrazole, 1-phenyl-5-ethoxycarbonylthio-tetrazole and the like. In the present invention, these may be used alone or in combination of two or more. Some sensitizers can also be used as photopolymerization initiators.

When the sensitizer is added to the conductive paste of the present invention, the amount added is based on the total amount of the acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain and the photoreactive compound. It is usually 0.1 to 20% by weight, more preferably 0.5 to 10% by weight. If the amount of the sensitizer is too 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 area may be too small.

In order to improve the thermal stability during storage in the conductive paste of the present invention, it is advisable to add a thermal polymerization inhibitor. Specific examples of the thermal polymerization inhibitor include hydroquinone, N-nitrosodiphenylamine, phenothiazine,
p-t-butylcatechol, N-phenylnaphthylamine, 2,6-di-t-butyl-p-methylphenol,
Examples include chloranil and pyrogallol. When the thermal polymerization inhibitor is added, the addition amount is usually 0.1 to the total of the acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain and the photoreactive polymerizable compound.
It is 20% by weight, more preferably 0.5 to 10% by weight. If the amount of the thermal polymerization inhibitor is too small, the effect of improving the thermal stability during storage will not be exhibited, and if the amount of the thermal polymerization inhibitor is too large, the residual rate of the exposed portion may be too small. There is.

As the plasticizer, for example, dibutyl phthalate, dioctyl phthalate, polyethylene glycol and glycerin are used.

An antioxidant may be added to the conductive paste of the present invention in order to prevent oxidation of the acrylic copolymer during storage. 2,6 as specific examples of antioxidants
-Di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-4-ethylphenol, 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 can be mentioned. When an antioxidant is added, its amount is usually a conductive powder, an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in its side chain, a photoreactive polymerizable compound, a glass frit and a photopolymerization initiator. 0.01 to 5% by weight, more preferably 0.1 to 1% by weight, based on the total
Is. If the amount of the antioxidant is small, the effect of preventing the 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 composition of the photosensitive conductive paste is preferably selected within the following range.

(A) Conductive powder; 75-92% by weight (B) Acrylic copolymer having carboxyl group and ethylenically unsaturated group in side chain and photoreactive compound; 25-
8% by weight (C) photopolymerization initiator; 2 to 25% by weight based on the total of the components (B) (D) glass frit and metal oxide; 0 to the total of (A) to (D) 5 wt% In the above, more preferably, the composition of the conductive powder and the component (B) is 80 to 89 wt% and 20 to 11 respectively.
% By weight. Within this range, ultraviolet rays are well transmitted during exposure, the photo-curing function is fully exerted, and the film strength of the exposed portion during development is increased. As a result, the reliability of the circuit pattern is further improved. Further, when the amounts of the polymer and the monomer are within this range, the specific resistance of the conductor film after firing becomes low, and the problem that the transmission loss of high frequency is reduced is eliminated. Further, the film becomes dense and a high-strength film can be obtained.

In the conductive paste of the present invention, an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in its side chain and a photopolymerization initiator are dissolved in a photoreactive compound, and a conductive powder is dispersed in this solution. Can be manufactured. When the acrylic copolymer and the photopolymerization initiator are not dissolved in the photoreactive compound, or when it is desired to adjust the viscosity of the solution, a mixed solution of the acrylic copolymer, the photopolymerization initiator and the photoreactive compound You may add the organic solvent which can melt | dissolve. Examples of the organic solvent used at this time include methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl ethyl ketone, dioxane, acetone, cyclohexanone, cyclopentanone, isobutyl alcohol, isopropyl alcohol, tetrahydrofuran, dimethyl sulfoxide, γ-butyrolactone and the like. To be These organic solvents may be used alone or in combination of two or more.

If necessary, a sensitizer, a thermal polymerization inhibitor, a plasticizer, an antioxidant, a dispersant, a stabilizer and an organic or inorganic precipitation inhibitor are added to obtain a slurry of the mixture. A slurry prepared to have a predetermined composition is uniformly dispersed by a three-roller or a kneader to prepare a paste.

The viscosity of the paste is appropriately adjusted depending on the composition of the conductive powder, the organic solvent and the glass frit, the addition ratio of the plasticizer, the suspending agent and the like, but the range is usually 2000 to 200,000 cps (centimeter. Poise). For example, when the substrate is coated by the spin coating method, 2000 to 5000 cps is preferable. 20,000 to 200,000 cps is preferable in order to obtain a film thickness of 10 to 40 μm by coating the sintered ceramics substrate once by the screen printing method. When applied to a green sheet, the viscosity is 5
10,000 to 200,000 cps is preferable. This is because if the viscosity is low, it is difficult to obtain the fine pattern of the present invention because the conductive powder penetrates into the green sheet during development after printing and exposing the paste on the green sheet.

Next, a method of forming a circuit pattern using a photosensitive conductive paste will be described.

First, the photosensitive conductive paste is applied to a ceramic green sheet, heat resistant glass at 600 ° C. or higher, or a ceramic substrate after sintering by a screen printing method. The printing thickness can be controlled arbitrarily by adjusting the screen mesh and the viscosity of the paste.
˜150 μm. It is difficult to uniformly form a film thickness of less than 5 μm, and when it exceeds 150 μm, it becomes difficult to transmit the film in ultraviolet exposure, so that pattern accuracy is deteriorated. In the case of the photosensitive conductive paste of the present invention, the preferable thickness range that allows fine exposure and development is 8 to 40 μm. If it is less than 8 μm, it becomes difficult to obtain a uniform thickness by the printing method. On the other hand, if it exceeds 40 μm, the accuracy of the circuit pattern decreases, and it becomes difficult to obtain a pattern having a line width / line spacing of 60 μm / 60 μm or less.

When the conductive paste is applied on a glass or ceramic substrate, it is preferable to perform a surface treatment on the substrate in order to enhance the adhesion between the substrate and the coating film. The surface treatment can be easily performed by uniformly applying the surface treatment solution onto the substrate with a spinner or the like and then drying at 80 to 140 ° C. for 10 to 60 minutes. As the surface treatment liquid, a silane coupling agent such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, tris- (2-methoxyethoxy) vinylsilane, γ-glycidoxypropyltrimethoxysilane, γ
-(Methacryloxypropyl) trimethoxysilane, γ
(2-Aminoethyl) aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc., or organic metals such as organic titanium, organic aluminum, organic zirconium Such as an organic solvent, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl alcohol, ethyl alcohol, propyl alcohol,
It is possible to use one diluted with butyl alcohol or the like to a concentration of 0.1 to 5% by weight.

Next, the paste film applied on the substrate is dried. Usually, it is carried out by heating at 70 to 120 ° C. for several minutes to 1 hour to evaporate the solvents.

After drying, by photolithography,
A film having a circuit pattern or a mask such as a chrome mask is used to irradiate with ultraviolet rays for exposure to cure the photosensitive paste. Although the exposure conditions vary depending on the thickness of the conductor film and the like, exposure is usually performed for 1 to 30 minutes using an ultrahigh pressure mercury lamp with an output of 5 to 100 mW / cm ² . The active light source used at this time includes, for example, ultraviolet rays, electron beams, X-rays and the like. Among these, ultraviolet rays are preferable, and as the light source, for example, a low pressure mercury lamp, a high pressure mercury lamp, a halogen lamp, a germicidal lamp, etc. can be used. . Of these, an ultra-high pressure mercury lamp is suitable.

Next, a portion which is not cured by exposure is removed using a developing solution to form a so-called negative type circuit pattern. Development is performed by a dipping method or a spray method. As the developing solution, an organic solvent capable of dissolving the mixture of the acrylic copolymer having an ethylenically unsaturated group in the side chain, the photoreactive compound and the photopolymerization initiator can be used. Further, water may be added to the organic solvent within the range in which the dissolving power is not lost. When the side chain of the acrylic copolymer has a carboxyl group, it can be developed with an aqueous alkali solution. As the alkaline aqueous solution, a metallic alkaline aqueous solution such as sodium hydroxide or calcium hydroxide aqueous solution can be used, but it is preferable to use the organic alkaline aqueous solution because the alkaline component can be easily removed during firing. Specific examples of the organic alkaline aqueous solution include tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide,
Examples include monoethanolamine and diethanolamine. The concentration of the alkaline aqueous solution is usually 0.5 to 10% by weight, more preferably 0.1 to 5% by weight. If the alkali concentration is too low, the unexposed area is not removed. If the alkali concentration is too high, the exposed area may be corroded, which is not good.

In the process of preparing, printing, exposing and developing the photosensitive conductive paste of the present invention, it is necessary to perform it at a place where ultraviolet rays can be blocked. If the ultraviolet rays are not blocked, the paste or the coating film is photo-cured by the ultraviolet rays, and the conductor film that can exert the effect of the present invention cannot be obtained.

After development, the coating film is baked in air. The firing conditions are not particularly limited, but an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain,
A preferable condition under which the photoreactive compound or the organic matter such as the solvent is completely oxidized and evaporated is 400 to 550 ° C.
After holding for 3 hours, it is preferable to bake at 600 to 1000 ° C. and bake on a ceramic substrate.

When a circuit pattern is formed using the photosensitive conductive paste of the present invention, for example, the conductor film has a thickness of 5 to 6
At 0 μm, a line width of the conductor is 10 to 60 μm, and a line interval between the conductors is 10 to 60 μm.

[0048]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto. In the following examples, all concentrations are expressed in parts by weight unless otherwise specified.

Examples 1-20 A. Conductive powder Conductive powder 1 (Ag powder) Spherical, average particle size 1.5 μm, specific surface area 0.15 m ² /
g Conductive Powder 2 (Ag Powder) Spherical, Average Particle Diameter 3.0 μm, Specific Surface Area 0.32 m ² /
g Conductive powder 3 (Ag powder) spherical, average particle diameter 4.0 μm, specific surface area 0.20 m ² /
g Conductive Powder 4 (Ag Powder) Spherical, Average Particle Diameter 1.5 μm, Specific Surface Area 0.28 m ² /
g Conductive Powder 5 (Ag (80) -Pd (20) Powder) Spherical, Average Particle Diameter 2.0 μm, Specific Surface Area 1.40 m ² /
g Conductive powder 6 (Pd powder) spherical, average particle diameter 1.0 μm, specific surface area 1.60 m ² /
g Conductive Powder 7 (Au (75) -Pd (25) Powder) Spherical, Average Particle Diameter 0.8 μm, Specific Surface Area 3.50 m ² /
g Conductive Powder 8 (Au (80) -Pt (20) Powder) Spherical, Average Particle Diameter 1.0 μm, Specific Surface Area 3.00 m ² /
g Conductive powder 9 (Pt (40) -Pd (20) -Au (4
0) Powder) Spherical, average particle size 0.9 μm, specific surface area 2.5 m ² / g B.I. Acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in its side chain (hereinafter abbreviated as polymer binder) Polymer binder 1; 40% methacrylic acid, 30
% Methylmethacrylate and 30% styrene copolymer with 0.4 equivalents (corresponding to 40%) of glycidyl acrylate added and reacted, acid value 150 mg KOH / g polymer binder 2; 30% Methacrylic acid, 35
% Ethyl methacrylate and 35% styrene copolymer, 0.3 equivalent of chloride acrylate was added and reacted with an acid value of 70 mgKOH / g C.I. Photoreactive compound (hereinafter abbreviated as monomer) Monomer 1; trimethylol propane triacrylate monomer 2; 2-hydroxyethyl acrylate: propylene glycol diacrylate mixed in a ratio of 1: 2.

D. Glass frit Glass frit 1 (component mol%); calcium oxide (5.0), zinc oxide (28.1), boron oxide (2)
5.0), silicon dioxide (22.8), sodium oxide (8.8), zirconium oxide (4.5), alumina (5.8) glass frit 2 (component weight%); zirconium oxide (42), Boron oxide (24), silicon dioxide (2
1), lithium oxide (7), alumina (4) and other oxides (2) E. Metal oxide Metal oxide 1; CuO Metal oxide 2; NiO F. Mixed solution of solvent γ-butyrolactone and ethyl cellosolve G. Photopolymerization initiator α-aminoacetophenone H. Production of photosensitive conductive paste a. Preparation of Organic Vehicle The solvent and the polymer binder were mixed and heated to 80 ° C. with stirring to uniformly dissolve all the polymer binders. Then, the solution was cooled to room temperature, and a photopolymerization initiator was added and dissolved. The solution was then passed through a 400 mesh filter and filtered. The amount of the solvent used at this time was such that the viscosity of the obtained paste was in the range of 20,000 to 50,000 cps.

B. Preparation of Paste A conductive powder, a monomer, a metal oxide powder, and a glass frit were added to the above organic vehicle so as to have a predetermined composition, and mixed and dispersed with three rollers to prepare a paste. The composition of the paste is shown in Tables 1 to 3.

C. Surface Treatment of Alumina Substrate As a surface treatment liquid, a 1% by weight solution of (2-aminoethyl) aminopropyltrimethoxysilane in isopropyl alcohol is used. Next, 1.5 ml of this solution was dropped on an alumina substrate and spun at a rotation speed of 3000 rpm for 10 minutes.
After applying for 2 seconds, the surface treatment was performed by holding at 100 ° C. for 30 minutes and drying.

D. Printing The above paste using a 250 mesh screen,
Solid-print 70 mm square on a surface-treated alumina substrate (100 mm square, thickness 0.5 mm),
It was dried at 80 ° C. for 40 minutes. The thickness of the coating film after drying varied depending on the types of the conductive powder, the polymer binder, and the monomer, but was 12 to 20 μm.

E. Exposure and development The coating film prepared above is 5 μm in the range of 10 to 60 μm.
Using a chrome mask on which fine patterns of intervals were formed, ultraviolet exposure was performed from the upper surface with an ultrahigh pressure mercury lamp with an output of 50 mW / cm ² . Next, it was immersed in a 1% by weight aqueous solution of monoethanolamine maintained at 25 ° C. for development, and then the photo-cured via holes were washed with water using a spray.

F. The coating film printed on the calcined alumina substrate was debindered and calcined in air at 500 ° C. for 1 hour to evaporate the polymer binder, the monomer, the photopolymerization initiator and the solvent, and then at 850 to 1000 ° C. The conductor film was produced by sintering for 5 hours. The firing temperatures are shown in Tables 1-3.

G. Evaluation The film thickness, resolution and specific resistance of the conductor film after firing were measured and evaluated. The film thickness was measured with a micrometer. The resolution was determined by observing the conductor film with a microscope and determining a line interval at which lines of 10 to 60 μm do not overlap with each other in a straight line and reproducibility is obtained as the finest line interval. The specific resistance was determined by measuring the electromotive force under a current of 30 mA by the 4-terminal method.
These measured values are shown in Tables 1-3.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

As described above, since a circuit pattern having a line width / line spacing of 60 μm / 60 μm or less and a low resistance and a circuit pattern having a low resistance can be obtained by a photolithography method using a conductive paste containing a photocurable resin, a ceramic is particularly preferable. This is advantageous for miniaturization and high density of multilayer substrates and hybrid ICs.

Comparative Examples 1 to 8 Polymer binders 3 and 4 were used as polymer binders.
The same procedure as in Example was performed except that was used. Table 4 shows the composition of the paste and the evaluation results. Acid value 210mgKOH /
In the case of g, it was difficult to control the development and the coating film was peeled off from the substrate. Also, acid value 30 mgKOH /
In the case of g, the unexposed area was not sufficiently dissolved, resulting in poor development.

Polymer binder 3; polymer obtained by addition-reacting a copolymer of 40% methacrylic acid, 30% methyl methacrylate and 30% styrene with 0.1 equivalent of glycidyl methacrylate, acid value 210 mg
KOH / g polymer binder 4; 10% methacrylic acid, 90%
A polymer obtained by addition-reacting 0.8 equivalent of glycidyl methacrylate with respect to the copolymer of methyl methacrylate of
Acid value is 30mgKOH / g

[Table 4]

[0063]

Since the present invention is constructed as described above, it is possible to surely form a fine pattern, and it is also possible to surely prevent the faint wiring pattern, the line width difference between the upper and lower sides, and the line width sag. Further, since the wiring resistance can be reduced, it is possible to reduce the transmission loss at high frequencies of a communication device or the like.
As a result, high reliability can be obtained, and miniaturization and high density of the high-density ceramic multilayer wiring board and hybrid IC are possible.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI G03F 7/038 G03F 7/038 H05K 1/09 H05K 1/09 D Z (56) Reference JP-A-3-171690 (JP, A) JP-A-5-271576 (JP, A) JP-A-62-220541 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 1/22 H01B 1/20 H05K 1 / 09

Claims (2)

(57) [Claims] 1. A conductive powder containing at least one selected from the group consisting of Au, Ag, Pd and Pt, (b) an acrylic copolymer having an acid value of 40 to 200, and (c) a photoreaction. Compounds , ( d) photopolymerization initiator and (e) glass transition
A photosensitive conductive paste comprising a glass frit having points of 300 to 500 ° C. 2. Whether the conductive powder is a group of Ag, Pd and Pt
The photosensitive conductive paste according to claim 1 , comprising at least one selected from the group consisting of: