JPH05287221A - Photosensitive conductive paste - Google Patents

Abstract

PURPOSE:To provide a photosensitive conductive paste which can form a very fine pattern and gives a low-resistance circuit pattern by compounding a specific conductive powder, a specific acrylic copolymer, a photoreactive compd., a photopolymn. initiator, and a stabilizer. CONSTITUTION:This paste comprises at least one conductive powder selected from Cu and Cu group metals (e.g. Cu powder), an acrylic copolymer having side chains having carboxyl and ethylenically unsatd. groups (e. g. a polymer prepd. from methacrylic acid, methyl methacrylate. styrene, and glycidyl acrylate), a photoreactive compd. (e.g. trimethylolpropane triacrylate), a photopolymn. initiator (e.g. alpha-aminoacetophenone), and a stabilizer (e.g. 1,2,3- benzotriazole.

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 is 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 is capable of 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-3-205462 and JP-A3-1.
As described in Japanese Patent No. 80092, a composition of a conductive paste is studied, a composition in which a photosensitive resin is added, a fine pattern is formed by a photolithography method, and optimization of a particle diameter of a metal powder is examined. However, it is 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 as follows.
(A) a conductive powder containing at least one selected from the group consisting of Cu and Cu-based metals, (b) an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain,
This is achieved by a photosensitive conductive paste containing (c) a photoreactive compound, (d) a photopolymerization initiator, and (e) a stabilizer.

That is, according to the present invention, a conductive paste is provided with photosensitivity. By using this, a thick film conductor circuit pattern can be formed finely and a low resistance conductor film can be efficiently formed by using a photolithography technique. It is possible.

The conductive powder used in the present invention is
It contains at least one selected from the group of Cu and Cu-based metals, and these conductive powders are used alone or as a mixed powder. These conductive powders are
Since it has a low resistance, it is possible to reduce the propagation loss at high frequencies. Specifically, Cu (97-70) -Ag (3-
30), Cu (95-60) -Ni (5-40), Cu
(90-70) -Ag (5-20) -Cr (3-15)
Binary or ternary mixed metal powders such as (the above () indicates weight%) are preferably used. Among the above, Cu-Ag powder is preferable, and among them, a powder in which the surface of Cu is coated with 3 to 30% by weight of Ag is particularly preferable because it can suppress the oxidation of Cu.

The average particle size of the conductive powder is 0.5.
˜7 μm is preferred. If the particle size is smaller than 0.5 μm, the light does not smoothly pass through the film after printing when exposed to ultraviolet rays, and it becomes difficult to form a fine pattern having a conductor line width of 60 μm or less. On the other hand, if the particle size exceeds 7 μm and becomes large, the surface of the circuit pattern after printing becomes rough, the pattern accuracy is lowered, and noise is generated. Further, a conductive powder having a specific surface area of 0.1 to ² 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 2 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 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. When it is spherical, the scattering of ultraviolet rays during exposure is very small, a highly precise pattern can be obtained, and the irradiation energy is small.

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, after the conductor pattern is printed, the light sufficiently penetrates without being scattered at the time of exposure to ultraviolet rays, and effectively works to obtain a fine circuit pattern of 1 to 5 μm. And has a specific surface area of 0.1 to 1.5 m
It is preferably ² / g. More preferably, the particle size is 1 to 5 μm and the specific surface area is 0.1 to 0.8 m ² / g. 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 having a carboxyl group and an ethylenically unsaturated group in the side chain used in the present invention is a polymer binder component (photosensitive polymer) and comprises an unsaturated carboxylic acid and an ethylenically unsaturated compound. It can be produced by adding an ethylenically unsaturated group to the side chain of an acrylic copolymer formed by copolymerizing the above.

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 their acid anhydrides. 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, and n-butyl acrylate. Butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, iso-butyl acrylate, isobutyl methacrylate, tert-butyl acrylate,
tert-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, styrene, p-
Examples include, but are not limited to, 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 a main polymerization component of these acrylic main chain polymers.

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

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. Further, examples of the chloride acrylate compound include chloride acrylate, chloride metaacrylate, and allyl chloride. 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 equivalents are preferable, 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 developer in the unexposed area is reduced. Or the hardness of the coating film becomes low.

The acid value of the acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain (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 amount of ethylenically unsaturated groups increases and the proportion of photosensitive carboxyl groups decreases, so that the solubility of the unexposed area in a developing solution decreases and the hardness of the coating film decreases. Is reduced. On the other hand, when the acid value exceeds 200, the development allowable width is narrow and the pattern edge is not easily cut.

The photosensitive conductive paste of the present invention may contain a photosensitive polymer other than the above acrylic copolymer or a non-photosensitive polymer as a polymer binder component.

The photosensitive polymer includes a photo-insolubilizing type and a photo-solubilizing type. As the photo-insolubilizing type, a functional monomer or oligomer having one or more unsaturated groups in one molecule is used. Mixed with a suitable polymer binder, aromatic diazo compound, aromatic azide compound,
A mixture of a photosensitive compound such as an organic halogen compound with an appropriate polymer binder, a photosensitive polymer obtained by pendant to an existing polymer with a photosensitive group, or a modified one thereof, a dizozo-based amine As a photosolubilizing type such as a so-called diazo resin such as a condensation product with formaldehyde, a mixture of an inorganic salt of a diazo compound and an organic acid, quinonediazide or the like mixed with a suitable polymer binder, and quinonediazos. Combined with a suitable polymer binder,
For example, naphthoquinone of phenol and novolac resin
1,2-diazido-5-sulfonic acid ester and the like can be mentioned. 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 and benzyl acrylate. , Butoxyethyl acrylate, butoxytriethylene glycol acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, 2-ethylhexyl acrylate, glycerol acrylate, glycidyl acrylate, heptadecafluorodecyl acrylate , 2-hydroxyethyl acrylate, isobonyl acrylate, 2-hydroxypropyl acrylate, isodexyl 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, ditrimethylolpropane tetraacrylate, glycerol diacrylate, methoxycyclohexyl diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate,
Examples include polypropylene glycol diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, and those obtained by replacing the above acrylate with methacrylate, γ-methacryloxypropyltrimethoxysilane, and 1-vinyl-2-pyrrolidone. . In the present invention, one or two of these photoreactive compounds are used.
It can be used as a mixture of two or more species. It can also be used as a mixture with a compound other than the above.

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 slurry becomes small and the uniformity of dispersion in the slurry 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.

Specific examples of the photopolymerization initiator used in the present invention include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamino) benzophenone and 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, benzylmethoxyethylacetal, benzoin, benzoinmethyl. 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-budadion-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 Disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, carbon tetrabromide, tribromophenyl sulfone, benzoin peroxide, eosin, methylene blue and other photoreducing dyes and ascorbic acid, reducing agents such as triethanolamine Examples include combinations. In the present invention, these photopolymerization initiators may be used alone or in combination of two or more.

The photopolymerization initiator is usually 0.1 to 30% by weight, more preferably, 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. It is used in an amount of 2 to 20% 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 resolution may decrease.

The stabilizer used in the present invention is to effectively prevent gelation of the photosensitive conductive paste and to obtain good printing characteristics. That is, in the present invention, conductive powder of Cu or a Cu-based metal, Cu oxide powder used as a metal oxide powder described later, metals such as Pb, Bi, Fe, and Mg contained in glass frit and oxides thereof. Since the powder or the like reacts with the carboxyl groups of the photosensitive polymer (acrylic copolymer), the paste gels in a short time and becomes a lump, which makes it impossible to print as a paste. It is presumed that this is an ionic cross-linking reaction between the photosensitive polymer and the above-mentioned metal or oxide powder, but in order to prevent such cross-linking reaction, the photo-sensitive compound, photo-reactive compound, photo It is necessary to prevent the gelation of the paste by adding a compound (stabilizer) that does not adversely affect the polymerization initiator or the plasticizer. That is, it is necessary to stabilize the photosensitive paste by surface-treating the powder with a compound having an effect of complexing with a metal or an oxide powder that causes a gelation reaction, or forming a salt with an acid functional group.

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

The method of surface-treating (stabilizing) a metal or oxide powder 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 the metal and oxide powders are immersed in the solvent. It is preferable to soak these powders for 1 to 24 hours so that they can be sufficiently immersed. After the immersion, the triazole-treated powder can be obtained by naturally drying at 20 to 30 ° C. and evaporating the solvent.

The amount of the stabilizer used in the present invention is 0. 0 with respect to the metal and oxide powder (Cu, Cu-based metal, Cu oxide, components in glass frit, etc.) subjected to the above surface treatment. The amount is preferably 2 to 5% by weight, more preferably 0.4 to 3% by weight. If it is less than 0.2% by weight, there is no effect of preventing the crosslinking reaction of the polymer and gelation occurs in a short time. On the other hand, if it exceeds 5% by weight, the amount of the stabilizer becomes too large, and it becomes difficult to remove the binder such as the polymer binder, the photoreactive compound and the stabilizer during the firing of the paste in the non-oxidizing atmosphere. The characteristics of are degraded.

In the present invention, it is preferable that the photosensitive conductive paste further contains glass frit.
The glass frit has a function as a sintering aid for sintering the conductive powder and an effect of lowering 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 50.
The temperature is preferably 0 ° 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 is 5
A glass frit exceeding 00 ° C. is not preferable because it results in poor adhesion to a ceramic substrate when sintered at a temperature of 800 ° C. or lower.

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 or ZnO
It is preferable to adjust the amount of such as 0.5 to 3% by weight because the thermal expansion coefficient and the melting point can be adjusted more easily. Further, the glass phase contains 0.2% by weight or more of P.
It is preferable not to include bO or CdO. As the particle size of the glass frit, finer particles are preferable because they melt at lower temperatures. Especially, 50% diameter is 0.6-3 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 based on the total amount of the conductive powder, the polymer binder, the photoreactive compound and the glass frit. It is more preferably 3% by weight or less. In particular, in order to reduce the resistance of the conductor film in order to reduce high frequency propagation loss, it is necessary to reduce the amount of glass frit. That is, since the glass frit is electrically insulating, if the content exceeds 5% by weight, the resistance of the conductor film increases, which is not preferable.

When printed on a ceramic green sheet used for a ceramic multilayer substrate and used for a conductor circuit for an inner layer or a power supply layer, the amount of glass frit is 2% by weight or less for the purpose of obtaining a low resistance. preferable. Further, when a strong adhesive force is required for the conductor film on the surface layer of the ceramic substrate, it is preferable to add 1 to 5% by weight as a glass frit. If it is less than 1% by weight, the effect of adding glass frit is small and a strong adhesive strength cannot be obtained. In the present invention, it is preferable to add a metal oxide in addition to the glass frit. The metal oxide effectively acts as a so-called sintering aid, such as avoiding abnormal grain growth of Cu or Cu-based conductive powder during sintering or delaying sintering. As a result, there is an effect of increasing the adhesive force between the conductor film and the ceramic substrate. Specifically, Cr, C
Oxides such as u, Mo, Al, Ni, Au and Pd can be used. Since the metal oxide electrically acts as an insulator, it is better that the amount of the additive is small, and 3% by weight or less based on the total amount of the conductive powder, the polymer binder, the photoreactive compound, the glass frit and the metal oxide. Is preferred. If it exceeds 3% by weight, the resistance of the conductor film increases, which is not preferable.

In the present invention, in the photosensitive conductive paste,
Sensitizer, thermal polymerization inhibitor, plasticizer, antioxidant, dispersant,
It is also preferable to add an organic or inorganic precipitation inhibitor or the like.

As the sensitizer, for example, 2,3-bis (4-diethylaminobenzal) cyclopentanone,
2,6-bis (4-dimethylaminibenzal) 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-dimethylaminocinnamylideneindanone, p-dimethylaminobenzylideneindanone, 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-tolyldiethanolamine, N-phenylethanolamine, dimethylaminobenzoic acid isoamyl, diethylaminobenzoic acid isoamyl, 3-phenyl-5-benzoylthio-tetrazolazole, 1-phenyl-5-ethoxycarbonylthio- And tetrazole. In the present invention, one kind or two or more kinds of these sensitizers can be used. Some sensitizers can also be used as photopolymerization initiators. When the sensitizer is added to the conductive paste of the present invention, the addition amount is usually 0.1 to 30 relative to the sum of the acrylic copolymer having an ethylenically unsaturated group in the side chain and the photoreactive compound. %, More preferably 0.5 to 15% 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.

The thermal polymerization inhibitor is added to improve the thermal stability during storage. Specific examples of the thermal polymerization inhibitor include hydroquinone, N-nitrosodiphenylamine, phenothiazine, pt-butylcatechol, N-.
Phenylnaphthylamine, 2,6-di-t-butyl-p
-Methylphenol, chloranil, pyrogallol and the like. When the thermal polymerization inhibitor is added, the amount added is 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,
Usually, 0.01 to 20% by weight, more preferably 0.0
It is 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. is there.

As the plasticizer, for example, diphtyl phthalate (DBP), dioctyl phthalate (DOP), polyethylene glycol, glycerin and the like are used.

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, 2,2-methylene-bis-
(4-methyl-6-t-butylphenol), 2,2-
Methylene-bis- (4-ethyl-6-t-butylphenol), 4,4-tibis- (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 ascid] glycol ester, dilauryl thiodipropionate, triphenyl phosphite and the like. When an antioxidant is added, its amount is usually based on the total amount of the conductive powder, the acrylic copolymer having an ethylenically unsaturated group in the side chain, the photoreactive compound, the glass frit and the photopolymerization initiator. It is usually 0.01 to 5% by weight, more preferably 0.1 to 1% by weight. 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 area may be too small.

The composition of the photosensitive conductive paste is preferably selected within the following range.

(A) Conductive powder; 75 to 92% by weight based on the sum of (A), (B) and (D) (B) Acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in the side chain Polymer and photoreactive compound; 25 to 8% by weight based on the sum of (A), (B) and (D) (C) Photopolymerization initiator; 2 to 20% by weight based on (B) (D ) Glass frit and metal oxide; 0 to 5% by weight based on the sum of (A), (B) and (D) (E) Stabilizer; 0.2 to 5% by weight based on (A) More preferably, the compositions of (A) and (B) are 80 to 89% by weight and 20 to 11% by weight, respectively. Within this range, ultraviolet rays are well transmitted during exposure, the function of photocuring is sufficiently 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 amount of (B) is in this range, the specific resistance of the conductor film after firing becomes low, and there is no problem that the propagation loss of high frequency decreases. In addition, the film becomes dense and a high-strength film can be obtained.

In the conductive paste of the present invention, an acrylic copolymer having 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 by. If the acrylic copolymer and the photopolymerization initiator having a carboxyl group and an ethylenically unsaturated group in the side chain is not dissolved in the photoreactive compound, or if you want to adjust the viscosity of the solution, the acrylic copolymer, An organic solvent in which the mixed solution of the photopolymerization initiator and the photoreactive compound can be dissolved may be added. The organic solvent used at this time may be one that can dissolve a mixture of an acrylic copolymer having an ethylenically unsaturated group in its side chain, a photopolymerization initiator and a photoreactive compound. For example, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl ethyl ketone, dioxane, acetone, cyclohexanone, cyclopentanone, isobutyl alcohol, isopropyl alcohol, tetrahydrofuran,
Dimethylsulfoxide, γ-butyrolactone, etc., and an organic solvent mixture containing at least one of them are used.

If necessary, an organic solvent, a sensitizer, a thermal polymerization inhibitor, a plasticizer, an antioxidant, a dispersant and an organic or inorganic precipitation inhibitor are added to obtain a mixture slurry. 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 by the composition of the conductive powder, the organic solvent and the glass frit, the plasticizer, the suspending agent and the like, and the range is 200.
It is 0 to 200,000 cps (centimeter poise). For example, when the coating on the substrate is performed by the spin coating method, 2000 to
5000 cps is preferred. Applying once to the sintered ceramics substrate by the screen printing method, the film thickness is 10 to 40 μm.
20,000 to 200,000 cps is preferable to obtain When applied to green sheets, the viscosity is 50,000 to 200,000 cp.
s is preferred. 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 the ceramic green sheet or the sintered ceramic substrate by the screen printing method. The printing thickness can be arbitrarily controlled by adjusting the mesh of the screen and the viscosity of the paste, but is usually 5 to 100 μm. 5μ
It is difficult to uniformly form a film thickness of less than m, and if it exceeds 100 μm, it becomes difficult to transmit the light when exposed to ultraviolet rays, so that the pattern accuracy is deteriorated. In the case of the photosensitive paste of the present invention, the preferable range of thickness that allows fine exposure and development is 5 to 40 μm. If it is less than 5 μm, it becomes difficult to obtain a uniform thickness by the printing method. 40 μm
If it exceeds, the accuracy of the circuit pattern is lowered, and a pattern having a line width / line spacing of 60 μm / 60 μm or less cannot be obtained.

When the photosensitive conductive paste is screen-coated on a glass or ceramic substrate, it is advisable 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 liquid on the substrate with a spinner or the like and then drying at 80 to 140 ° C. for 10 to 60 minutes. Examples of the surface treatment liquid include silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, tris- (2-methoxyethoxy) vinylsilane, γ-glycidoxypropyltrimethoxysilane, γ- (methacryloxy). Propyl) trimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane,
γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane and the like or organic metals such as organic titanium, organic aluminum and organic zirconium. Use a silane coupling agent or an organic metal diluted with an organic solvent such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl alcohol, ethyl alcohol, propyl alcohol or butyl alcohol to a concentration of 0.1 to 5%. You can

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 conductive paste. Although the exposure conditions vary depending on the thickness of the conductor film, the 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 . Examples of the active light source used at this time include ultraviolet rays, electron beams, X-rays, etc. Among them, ultraviolet rays are preferable,
As the light source, for example, a low pressure mercury lamp, a high pressure mercury lamp, a halogen lamp, a germicidal lamp or the like can be used. Among these, the ultra-high pressure mercury lamp is preferable.

Next, a so-called negative type circuit pattern is formed by removing a portion which is not cured by the exposure using a developing solution. Development is performed by a dipping method or a spray method. As the developing solution, an organic solvent in which the mixture of the acrylic copolymer having an ethylenically unsaturated group in the side chain, the photoreactive compound and the photopolymerization initiator can be dissolved 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 alkaline aqueous 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 alkali include tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide,
Examples include 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 area is not removed. If the alkali concentration is too high, the pattern area may be peeled off and the exposed area may be corroded.

The steps of preparing, printing, exposing and developing the photosensitive conductive paste of the present invention must be carried out 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 exposure and development, the coating film is baked in a substantially non-oxidizing atmosphere. The substantially non-oxidizing atmosphere is an atmosphere that can avoid the oxidation of Cu and Cu-based metals, and includes a polymer binder, a photoreactive compound, a stabilizer,
Alternatively, an atmosphere that allows oxidation and evaporation of an organic substance such as a solvent may be used. For example, it can be fired in an atmosphere containing 3 to 100 ppm of oxygen and the balance being neutral gas such as nitrogen or argon or steam controlled. The firing temperature may be any temperature at which the organic binder is completely oxidized and evaporated, and it is preferable that the firing is performed at 600 to 900 ° C. after holding at 400 to 550 ° C. for 1 to 6 hours and baking on the 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
In the case of 0 μm, the line width of the conductor is 10 to 60 μm,
Line spacings between conductors of 10-60 μm are obtained.

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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, the amounts used are all parts by weight unless otherwise specified.

Examples 1 to 17 A. Conductive Powder Conductive Powder 1 (Cu Powder) Spherical, Average Particle Diameter 1.5 μm, Specific Surface Area 0.15 m ² / g Conductive Powder 2 (Cu Powder) Spherical, Average Particle Diameter 3.0 μm, Specific Surface Area 0.32 m ² / g conductive powder 3 (Cu powder) spherical, average particle diameter 4.5 μm, specific surface area 0.30 m ² / g conductive powder 4 (Cu (80) -Ag (20) powder) spherical, average particle diameter 3 0.4 μm, specific surface area 0.35 m ² / g conductive powder 5 (Cu (80) -Ag (20) powder) spherical, average particle diameter 3.6 μm, specific surface area 0.55 m ² / g conductive powder 6 (Cu (90) -Ni (5) -Cr (5) powder) Spherical, average particle diameter 2.5 μm, specific surface area 0.25 m ² / g B.I. Acrylic copolymer having carboxyl group and ethylenically unsaturated group in side chain (hereinafter, abbreviated as polymer binder) Polymer binder 1; 40% methacrylic acid, 30
% Methylmethacrylate and 30% styrene with 0.4 equivalents (corresponding to 40%) of glycidyl acrylate added thereto Polymer binder 2; 30% methacrylic acid, 35
% Ethyl methacrylate and 35% styrene with 0.3 equivalents (corresponding to 30%) of chloride acrylate added thereto.

C. 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. Stabilizer 1,2,3-benzotriazole (Tokyo Chemical Industry Co., Ltd.)
Manufactured by E. Glass frit (component mol%) Glass frit 1; calcium oxide (5.0), zinc oxide (28.1), boron oxide (25.0), silicon dioxide (22.8), sodium oxide (8.8) , Zirconium oxide (4.5), alumina (5.8), glass frit 2; zirconium oxide (39), boron oxide (24), silicon dioxide (21), lithium oxide (10), alumina (3) and Other oxides (3) F. Metal oxide CuO powder G. Solvent γ-butyrolactone H. Photopolymerization Initiator α-aminoacetophenone I. Manufacturing of conductive paste a. Preparation of Organic Vehicle Mix solvent and polymer binder and stir 8
It was heated to 0 ° C. 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. Surface Stabilization Treatment of Conductive Powder After dissolving a predetermined amount of benzotriazole in the conductive powder described in A above in methyl acetate, the conductive powder was immersed in the solution for 12 hours. After the immersion, the powder was dried in a draft at 20 to 25 ° C., the solvent was evaporated, and a triazole-treated conductive powder was produced.

C. Paste Preparation Stabilized conductive powder, monomer, metal oxide, and frit were added to the above organic vehicle so as to have a predetermined composition, and mixed and dispersed by a three-roller to prepare a paste. .. The composition of the paste is shown in Tables 1 to 3.

However, the polymer binder concentration (% by weight)
= Polymer binder / (polymer binder + γ-butyrolactone) × 100, stabilizer (% by weight) =
Stabilizer / conductive powder × 100.

D. Surface Treatment of Alumina Substrate As a surface treatment liquid, a 1 wt% 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.

E. Printing The above paste was placed on an alumina substrate (100 mm square, thickness 0.5 mm) using a 250 mesh screen.
It was solidly printed in a size of 0 mm square, held at 80 ° C. for 40 minutes and dried. The thickness of the coating film after drying is conductive powder,
20 to 3 depending on the type of polymer and monomer
It was 0 μm. Printing was performed in a room protected from ultraviolet rays.

F. Exposure and development The coating film prepared above is 5 μm in the range of 20 to 40 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 0.5% by weight aqueous solution of monoethanolamine maintained at 25 ° C. for development, and then the portion which was not photocured was washed with water using a spray.

G. Firing The coating film printed on the alumina substrate was kept in an atmosphere (the balance: nitrogen) containing 50 ppm of oxygen at 500 ° C. for 4 hours to evaporate the binder, and then sintered at 850 to 1000 ° C. for 0.5 hours. A conductor film was prepared.

H. 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 the line interval at which lines of 20 to 40 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.
Regarding the effect of the stabilizer, after the paste was prepared, the life was judged by the number of days or the time during which the paste could be stored without gelation. The measurement results are shown in Tables 1 to 3.

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[Table 1]

[Table 2]

[Table 3] Comparative Examples 1 and 2 Conductive powders 1 (Comparative Example 1) and 5 (Comparative Example 2) described above.
Was used to prepare a paste under the same conditions as in the above-mentioned example except that the stabilization treatment was not performed in the paste. When the prepared paste was put in a container and sealed and left at room temperature for 1 to 3 hours, all the pastes gelled and printing became impossible, and the paste could not be used.

As shown in Examples and Comparative Examples, when the photosensitive conductive paste of the present invention is used, pattern processing by the photolithography method is possible, and the line width / line spacing is 40 μm / 40 μm or less and is fine. A circuit pattern with low resistance can be obtained.

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According to the present invention, it is possible to surely form a fine pattern, and it is possible to surely prevent the wiring pattern from fading, the vertical difference of the line width, and the sag of the line width.
Also, since the wiring resistance can be reduced, it is possible to reduce the propagation 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 substrate and hybrid IC can be realized.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaya Asano 1-1-1, Sonoyama, Otsu City, Shiga Prefecture Toray Co., Ltd. Shiga Plant

Claims (2)

[Claims] 1. A conductive powder containing at least one selected from the group consisting of Cu and Cu-based metals, and (b) an acrylic copolymer having a carboxyl group and an ethylenically unsaturated group in a side chain. A photosensitive conductive paste comprising (c) a photoreactive compound, (d) a photopolymerization initiator, and (e) a stabilizer. 2. The photosensitive conductive paste according to claim 1, further comprising a glass frit.