JP2000305259A - Photosensitive conductor paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive conductor paste having good electric conductivity after firing without using a scaly or fine powder by using a metal powder, a photosensitive resin and a metallic compound soluble in an organic solvent. SOLUTION: The photosensitive conductor paste contains a metal powder, a photosensitive resin and a metallic compound soluble in an organic solvent. The metallic compound does not shield light in exposure for patterning the paste because of the dissolved state and does not adversely affect the patterning. When the paste is fired, the metallic compound is decomposed to deposit the metal and this metal is filled into the voids in the metal powder in the paste to attain high electric conductivity. A polymer in the photosensitive resin is not particularly limited but is preferably an alkali-soluble polymer because the photosensitive resin containing the alkali-soluble polymer is patterned by development using an aqueous alkali solution in place of an organic solvent.

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 fine wiring patterns on a ceramic substrate or a glass substrate, and a photosensitive insulating paste for forming fine through holes in an insulating layer. .

[0002]

2. Description of the Related Art In recent years, multi-chip modules mounted on personal computers and PC cards, chip-size packages, or high-frequency filters for mobile communication devices such as mobile phones, chip inductors, multilayer capacitors, and other electronic components or ceramic multilayers. There is an increasing demand for smaller, higher density, higher definition, and higher reliability substrates. In addition, as the definition of a display device such as a plasma display has become higher, the demand for finer electrodes has also increased. To meet these requirements, various methods for forming a fine conductive film have been proposed.

Typical methods include a thin film method, a plating method, and a thick film printing method. In the thin film method, patterning with a resolution of L / S = 20/20 μm or more is possible by a photolithography technique after forming a film by sputtering, vapor deposition or the like. However, there is a drawback that only a thin film can be obtained because of having a long time to make the film thick, and as a result, the impedance as a 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 a firing step.

On the other hand, in a thick film printing method in which a paste made of a conductor powder and a resin is printed by screen printing and then baked to form a conductor, a thick conductor film is formed, and passive elements such as resistors are simultaneously formed. On the other hand, on the other hand, it is difficult to form a line of a fixed width with a resolution of L / S = 50/50 μm or less, and it is difficult to design an electric characteristic surface because the cross-sectional shape is on a kamaboko. There was a problem.

As a method for improving the resolution and the sectional shape of the thick film printing method, there is a photosensitive paste method. In this method, a high-resolution thick-film conductor pattern can be formed by using a photosensitive paste as a conductive paste for thick-film printing and performing a mask exposure and development process after printing. As the photosensitive paste, a mixture of a metal powder and a photocurable resin is often used.

[0006] Although the photosensitive paste method is an excellent method as described above, the design of the material is restricted as compared with the non-photosensitive paste. As one of them, there are restrictions on the shape and size of the metal powder. In the non-photosensitive conductor paste used in the conventional thick film printing method, for the purpose of improving the sinterability of the conductor, using a scale-like metal powder, or very small size, specifically 0.1μm Inventions have been made such as using a metal powder having an average particle diameter of less than, that is, so-called ultrafine metal particles. Since flaky metal powder and ultrafine metal particles are easily sintered, a conductor having a small specific resistance after firing and having excellent electric conductivity can be obtained.

[0007]

However, it is difficult to use any of these powders in a photosensitive paste. When exposing the photosensitive paste, a light beam needs to pass through the paste. At this time, the light beam passes through a gap between the conductive powders. The scale-like powder tends to be oriented parallel to the substrate when printed, so that it becomes a form that covers the substrate surface without any gaps and blocks light rays. Further, as the conductor powder becomes finer, the gap between the powders becomes smaller, and it becomes difficult to transmit light rays. For this reason, the photosensitive conductor paste improves the light transmittance,
In order to improve the pattern workability, the conductor powder must be spherical or massive, and the size cannot be extremely small. There was a drawback that it became inferior to the conductor paste. This disadvantage is particularly problematic when the firing temperature is low. In display applications, it is necessary to form a conductor on a glass substrate, and since the heat-resistant temperature of glass is lower than that of ceramics, it is necessary to lower the firing temperature. Therefore, the disadvantage that the electrical conductivity of the photosensitive paste is poor is a significant problem particularly in display applications.

It is an object of the present invention to provide a photosensitive conductive paste having good electric conductivity after firing without using scaly or fine powder.

[0009]

The present invention is a photosensitive conductor paste containing metal powder and a photosensitive resin as essential components,
A photosensitive conductor paste containing an organic solvent-soluble metal compound.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The present invention does not use scale-like or fine powder, so that pattern processing is good, and even though these powders are not used, a photosensitive conductor paste having good electric conductivity after firing is obtained. This is achieved by a photosensitive conductive paste comprising a metal powder, a photosensitive resin, and a metal compound soluble in an organic solvent.

A known example of adding a metal compound soluble in an organic solvent to a conductor paste is disclosed in JP-A-6-5718.
No. 3, there is an effect of improving the adhesive strength to a substrate by adding a metal resinate to a conductive paste. However, there is no mention of a specific resistance value, and a more effective configuration is described. , The metal powder is copper, and the resinate is zinc, copper, titanium, aluminum, magnesium, palladium, iridium, chromium,
The combination is limited to only the combination of manganese, and is limited to only the combination having the effect of improving the adhesive strength, and the effect of reducing the resistance by the resinate has not been considered at all.

In the present invention, since the organic solvent-soluble metal compound is dissolved in the paste at the time of exposure for pattern processing of the paste, it does not block the light beam and does not adversely affect the pattern processability. In addition, when firing is performed, the metal compound is decomposed to precipitate a metal, which is filled in the voids of the metal powder in the paste, thereby achieving high electrical conductivity.

The photosensitive resin in the present invention is a photosensitive resin comprising a polymer, a polyfunctional monomer having two or more carbon-carbon double bonds in one molecule, and a photopolymerization initiator as essential components. Organic components that are responsible for the photosensitivity of

The polymer in the photosensitive resin is not particularly limited, but is preferably an alkali-soluble polymer because the patterning of the photosensitive resin can be performed by an aqueous alkali solution development instead of an organic solvent. Examples of the alkali-soluble polymer include an acrylic copolymer. The acrylic copolymer is a copolymer containing at least an acrylic monomer in a copolymer component, and specific examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, and isopropyl acrylate. , N-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, tert
-Butyl acrylate, n-pentyl acrylate, allyl acrylate, 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, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluoro Acrylics such as ethyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylate, acrylamide, aminoethyl acrylate, phenyl acrylate, phenoxyethyl acrylate, 1-naphthyl acrylate, 2-naphthyl acrylate, thiophenol acrylate, and benzyl mercaptan acrylate Monomers and those obtained by replacing these acrylates with methacrylates are exemplified. As the copolymerization component other than the acrylic monomer, all compounds having a carbon-carbon double bond can be used.
-Methylstyrene, o-methylstyrene, m-methylstyrene, α-methylstyrene, chloromethylstyrene,
Styrenes such as hydroxymethylstyrene, γ-methacryloxypropyltrimethoxysilane, 1-vinyl-
2-pyrrolidone and the like. Desirably, by containing an alkyl acrylate or an alkyl methacrylate, more preferably at least methyl methacrylate, a polymer having good thermal decomposability can be obtained. Since the polymer has alkali solubility, an alkali aqueous solution can be used as a developer instead of an organic solvent having environmental problems. In order to impart alkali solubility to the acrylic copolymer, it is achieved by adding an unsaturated acid such as an unsaturated carboxylic acid as a monomer. Specific examples of the unsaturated acid include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetate, and acid anhydrides thereof. By adding these, the acid value of the polymer is from 80 to 14 from the viewpoint of developability.
It is preferably in the range of 0.

In order to improve the curing rate, it is preferable that at least a part of the polymer has a carbon-carbon double bond in a side chain or a molecular terminal. Examples of the group having a carbon-carbon double bond include a vinyl group, an allyl group, an acryl group, and a methacryl group. In order to add such a functional group to the polymer, a compound having a glycidyl group or an isocyanate group and a carbon-carbon double bond with respect to a mercapto group, an amino group, a hydroxyl group, and a carboxyl group in the polymer, acrylic acid chloride, There is a method in which methacrylic acid chloride or allyl chloride is produced by an addition reaction.

Examples of the compound having a glycidyl group and a carbon-carbon double bond include glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, glycidyl ethyl acrylate, crotonyl glycidyl ether, glycidyl crotonate, and glycidyl isocrotonate. Examples of the compound having an isocyanate group and a carbon-carbon double bond include acryloyl isocyanate, methacryloyl isocyanate, acryloylethyl isocyanate, and methacryloylethyl isocyanate.

As the polyfunctional monomer, a compound having two or more carbon-carbon double bonds in one molecule is used, and specific examples thereof include allylated cyclohexyl diacrylate and 1,4-butanediol diacrylate. 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, methoxylated cyclohexyl diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate, polypropylene glycol diacrylate , Triglycerol diacrylate, trimethylolpropane triacrylate, bisphenol A
Examples include diacrylate, diacrylate of a bisphenol A-ethylene oxide adduct, diacrylate of a bisphenol A-propylene oxide adduct, and a compound in which one or all of the acryl group of the above compound is replaced with a methacryl group.

As the photopolymerization initiator, a commercially available photoradical initiator can be suitably used. For example, 2-benzyl-2
-Dimethylamino-1- (4-morpholinophenyl)
-Butanone-1, or bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2
Examples of 2,4-diethylthioxanthone and the like for -methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one include photopolymerization initiator systems which can be used in the present invention. However, the present invention is not limited to this.

The shape of the metal powder used in the present invention is desirably monodisperse, non-agglomerated, spherical or granular. In this case, the spherical shape preferably has a sphericity of 80% by number or more. For the measurement of the spherical ratio, the powder was photographed with an optical microscope at a magnification of 300 times and counted, and the ratio of the spherical particles was expressed.
If it is spherical, light scattering will be very small during exposure,
Light is easily transmitted to the inside of the film.

The metal powder used in the present invention includes:
Examples include gold, silver, copper, nickel, tungsten, and molybdenum, but are not particularly limited thereto. In consideration of the purpose of obtaining a low-resistance conductor by low-temperature sintering of the present invention, a metal having a relatively low melting point and a low specific resistance is preferable, and gold, silver, and copper are preferable. Furthermore, silver is the most suitable because gold is very expensive and copper is easily oxidized and cannot be fired in air.

The average particle size of the metal powder is 1 μm or more,
It is desirable that the thickness be in the range of μm or less. Average particle size is 1
When the particle size is less than μm, when the same volume of metal powder is added to the resin, the surface area of the powder becomes large, and since there are fewer voids, more light is blocked and the light transmittance into the paste is reduced. Let it. If it is larger than 6 μm, the surface roughness when applied is large, and the pattern accuracy and dimensional accuracy are undesirably reduced.

As a method for measuring the particle size distribution and the average particle size of the metal powder, a light scattering method is preferably used. In the light scattering method, a particle size distribution can be obtained.
The average particle diameter is defined as the particle diameter corresponding to the 0% amount, so-called D50 particle diameter.

The organic solvent-soluble metal compound used in the present invention is not particularly limited.
Metal organic acid salts, metal sulfide compounds, metal alkoxides and the like can be mentioned.

Examples of the organometallic compound include an alkylmetal compound, an arylmetal compound, a Grignard compound, an organometallic complex compound, a metallocene compound, a chelate compound and a metal carbonyl compound. Examples of the organic acid metal salt include a metal naphthenate, octylate, phenoxy salt and 2-ethylhexanoate. Examples of the organic sulfur metal compound include sulfonic acid metal salts such as p-toluenesulfonic acid salt, metal mercaptides such as dodecylthioalcoholate, and balsam sulfide. Examples of the metal alkoxide include an alkoxy or benzoxy metal compound.

Of these metal compounds, those which are soluble in the photosensitive resin used in the photosensitive paste and the solvent, and which decompose quickly upon baking to volatilize the organic component to give a metal are desirable.

The kind of the metal contained in the organic solvent-soluble metal compound is not particularly limited, but for the purpose of improving the sinterability at the time of low-temperature firing, a metal of the same kind as the metal powder contained in the photosensitive paste is used. It is preferable to select a metal corresponding to one of the following: a metal having a lower melting point than the metal of the metal powder; or a metal forming an alloy having a lower melting point with the metal of the metal powder.

For example, when the metal powder contained in the photosensitive paste is silver, the metal contained in the organic solvent-soluble metal compound is the same silver, or has a lower melting point than silver and silver. It is preferable to use tin which can form an alloy having a low melting point.

The amount of the metal compound added is 0.1% or more in terms of metal relative to the amount of metal powder in the photosensitive paste.
Desirably, it is 0% or less. When the content is 0.1% or less, the improvement in sinterability and the improvement in electric conductivity are not sufficient, and the addition of 10% or more lowers the pattern processability of the paste.

Next, an example of forming a pattern using the photosensitive paste according to the present invention will be described, but the present invention is not limited to this.

A paste is applied by screen printing on an alumina substrate, a glass substrate, or the like, and dried. 70 ° C-10
After drying by heating at 0 ° C. for a few minutes to 1 hour. Exposure is through a mask. A negative type mask is used for a desired electrode shape. Exposure is performed using a high-pressure mercury lamp or the like, and the amount of exposure is, for example, 10 to 3 as measured by i-line (365 nm).
It is performed at 00 mJ / cm ² . After exposure, development is performed using an alkaline aqueous solution as a developer. The alkaline aqueous solution is preferably an organic alkali such as tetramethylammonium hydroxide or ethanolamine in order to prevent residual metal components. After developing with a developer for a predetermined time, washing is performed with water. These development and washing can be carried out by dipping, spraying, paddle, etc., but spray development is preferred because a higher resolution is obtained and a pattern is obtained. The spraying time of the developing solution is 20 seconds to 200 seconds, and the washing with water is also performed by spraying for 10 seconds to 60 seconds. It is preferable to rotate the substrate during spraying from the viewpoint of uniformity of development. The rotation speed is preferably 100 to 1000 rpm. After washing with water
Turn up to shake off excess water and dry. The rotation speed at this time is 1000 to 4000 rotations. If necessary, completely remove the water with an oven, etc.
The conductor film or the insulating layer can be formed by baking in a belt furnace or the like to volatilize the organic components and sinter the metal powder. The firing is performed in the air or in a nitrogen atmosphere. When the metal powder is a metal such as copper which is easily oxidized, the metal powder is heated at 800 to 1000 ° C. in a nitrogen atmosphere or a hydrogen atmosphere containing 10 to 100 ppm of oxygen.
Hold for ~ 60 minutes and bake to create a pattern.

With this configuration, a photosensitive paste having good storage stability and excellent pattern processability can be obtained.

The pattern formed by the photosensitive paste of the present invention is particularly effective when fired at a low temperature, and thus is suitable for forming a conductor on a glass substrate having a lower heat resistance than a ceramic substrate. Yes, especially suitable for display applications, but not only electrodes on MCM (multi-chip module) substrates and CSP (chip size package) substrates mounted on notebook computers and mobile phones, but also chip inductors and chip capacitors Such as chip component electrodes, module substrate electrodes, etc.
The present invention is also applicable to a case where a conductor is formed on a ceramics or glass ceramics substrate.

[0033]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited by these examples. For each composition shown in Table 1, the paste was adjusted in the manner described below, and a pattern workability test was performed. The raw materials used are shown below. A. Metal powder a. Silver powder Monodisperse granular Average particle diameter 3.6 μm Specific surface area 1.0 (m ² / g) Tap density 4.5 (g / c)
m ³ ) (Datong special steel) Polymer (in photosensitive organic component) Glycidyl methacrylate-modified methacrylic acid-methyl methacrylate copolymer a. Acid value 84 Weight average molecular weight 10,000 (Gel permeation chromatography (GPC)
In terms of polystyrene) C.I. Polyfunctional monomer Propylene oxide-modified trimethylolpropane triacrylate Trifunctional monomer Double bond equivalent 157 g / mol T
PA-330 (Nippon Kayaku).

D. Photoinitiator 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (Irgacure 369 of Ciba Specialty Chemicals: hereinafter referred to as IC369). E. FIG. Solvent γ-butyrolactone F. Dispersant Dispersant a: “NOPCOSPARSE 092” (manufactured by San Nopco) Leveling agent LC-951 (Kusumoto Kasei) (effective concentration is 10% by weight, the remainder is solvent) Organic Solvent Soluble Metal Compound a. Balsam silver sulfide (silver content 10%) b. Tin 2-ethylhexanoate (Tin content 29%) c. Tetrabutyltin (34% tin content) Developer Tetraethylammonium hydroxide 0.1% by weight
Aqueous solution.

The following operations were all performed under yellow light. Preparation of paste (1) A polymer and a solvent were mixed and heated at 60 ° C. for 3 hours to be dissolved. (2) The polymer solution was cooled to room temperature, the other organic composition, the metal powder, and the organic solvent-soluble metal compound were mixed, and uniformly mixed at 200 rpm for 30 minutes at room temperature using a motor and a stirring blade. (3) The obtained slurry was rolled with three rolls (EXACT
Model 50) to obtain a paste.

Pattern processing (1) The paste was applied on the entire surface of a 96% alumina substrate of 7.5 cm square (manufactured by Nikko) by screen printing.

The screen used was SUS # 325 mesh. (2) The printed substrate was dried in a hot air oven at 80 ° C. for 40 minutes. The film thickness after drying was 15 μm. (3) Using a high-pressure mercury lamp (15 mW / cm ² ), the paste was exposed through a pattern mask. As the pattern mask, a meandering pattern having a length of 374.4 mm and a width of 0.3 mm was used. (4) The exposed substrate was immersed in an alkali developing solution (0.1% TMAH aqueous solution), developed by shaking, and then rinsed with a water shower.

Firing (1) The substrate on which the meander pattern after development was formed was placed in an electric furnace and heated to 580 ° C. in the air for 2 hours. (2) Hold at 580 ° C. for 20 minutes. (3) The heating was stopped and the product was naturally cooled.

Evaluation of conductivity (1) A stylus type step meter (Surfcom 1500 manufactured by Tokyo Seimitsu)
Using A), the thickness of the meander pattern after firing was measured. (2) The electric resistance between both ends of the meander pattern was measured using a tester. (3) The specific resistance of the conductor was measured using the following equation.

Rs = R ÷ l × w × h × 100 Rs: Specific resistance of conductor (μΩ · cm) R: Resistance of conductor (Ω) l: Length of conductor (mm) Here, 374.4 m
m w: width of conductor (mm) where 0.3 mm h: thickness of conductor (μm).

The results are all shown in Table 1. Note 1 in the table shows the weight% of the metal contained in the organic solvent-soluble metal compound relative to the silver powder.

[0042]

[Table 1]

The results shown in Examples 1 to 5 are examples in which a silver compound and a tin compound each soluble in an organic solvent are added to the photosensitive silver paste. Compared to Comparative Example 1 in which no organic solvent-soluble metal compound was used,
In each case, the specific resistance of the conductor after firing is reduced,
It was shown that the conductivity was improved.

[0044]

According to the present invention, the sinterability of the photosensitive paste is improved by having the above-described structure,
It is possible to obtain a paste capable of forming a conductor having good conductivity at a low temperature of less than.

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Claims (13)

[Claims] 1. A photosensitive conductor paste comprising a metal powder and a photosensitive resin as essential components, comprising a metal compound soluble in an organic solvent. 2. The photosensitive conductor according to claim 1, wherein at least a part of the metal contained in the organic solvent-soluble metal compound is the same kind of metal as the metal powder contained in the photosensitive conductor paste. paste. 3. The photosensitive material according to claim 1, wherein at least a part of the metal contained in the organic solvent-soluble metal compound is a metal having a lower melting point than the metal powder contained in the photosensitive conductive paste. Conductive paste. 4. A metal contained in an organic solvent-soluble metal compound, at least a part of which is alloyed with a metal powder contained in a photosensitive conductor paste to form an alloy having a lower melting point than the metal of the metal powder. 2. The method according to claim 1, wherein
The photosensitive conductor paste as described in the above. 5. The photosensitive conductor paste according to claim 1, wherein at least a part of the organic solvent-soluble metal compound is an organic metal compound. 6. The photosensitive conductor paste according to claim 1, wherein at least a part of the organic solvent-soluble metal compound is an organic acid metal salt. 7. The photosensitive conductor paste according to claim 1, wherein at least a part of the organic solvent-soluble metal compound is an organic sulfur metal compound. 8. The photosensitive conductor paste according to claim 1, wherein at least a part of the metal powder is silver powder. 9. The photosensitive conductor paste according to claim 1, wherein the photosensitive resin contains at least an alkali-soluble polymer, a polyfunctional monomer, and a photoinitiator. 10. The photosensitive conductor paste according to claim 4, wherein the alkali-soluble polymer is an alkali-soluble acrylic copolymer. 11. An alkali-soluble acrylic copolymer,
6. The photosensitive conductive paste according to claim 5, having a carbon-carbon double bond in a side chain. 12. The photosensitive conductive paste according to claim 1, wherein the metal powder is spherical or granular. 13. The metal powder has an average particle diameter of 1 μm or more and 6 μm or more.
The photosensitive conductor paste according to claim 1, wherein m is equal to or less than m.