JP2000332379A - Formation of conductor pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve use efficiency of paste since paste applied to a part excepting a conductor pattern is removed by developer in a conductor pattern formation method by photosensitive conductor paste. SOLUTION: In a conductor pattern formation method wherein photosensitive conductor paste is used, after a pattern which is larger than a desired pattern is formed by partially applying photosensitive conductor paste on a substrate wherein a pattern is formed, exposure and development are carried out by using a photomask of a desired pattern and a desired pattern is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a conductive pattern.

[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, in the plating method, a plating speed becomes a problem in forming a sufficiently thick film, and a waste of a plating solution containing a large amount of metal becomes a problem.

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. This uses a photosensitive paste as a conductive paste for thick film printing, and after printing over the entire surface of the substrate, is subjected to a mask exposure and development process, whereby a high-resolution thick film conductive pattern can be formed. . 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, it has a problem in material efficiency as compared with a non-photosensitive paste. That is, in the case of a non-photosensitive paste, the paste is applied by screen printing only to a desired conductor pattern portion on the substrate, whereas in the case of a photosensitive paste, the paste is first applied to the entire surface of the substrate. Then, the paste applied to unnecessary portions other than the desired conductor pattern by exposure and development is removed. Usually, the removed paste becomes a waste liquid mixed with the developer used for the removal, and cannot be reused. Therefore, many pastes do not contribute to the formation of the electrodes and are wasted. This problem is even more pronounced when the conductor contained in the paste is a noble metal such as gold or silver. In recent years, a large screen of a 50-inch class has been developed for a plasma display, and a large amount of paste is used because a very large substrate is used. In proportion thereto, a large amount of paste is wasted during the development. Furthermore, since the width of the stripe pattern of the display electrode of the plasma display is much larger than the width of the electrode, most of the applied photosensitive conductive paste is removed by development. The efficiency was less than half.

An object of the present invention is to improve the use efficiency of a photosensitive paste in a conductive pattern forming method using a photosensitive conductive paste.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for forming a conductive pattern using a photosensitive conductive paste, wherein a photosensitive conductive paste is partially applied onto a substrate on which a pattern is to be formed, so that a desired pattern can be obtained. This is a method for forming a conductor pattern, wherein after forming a large pattern, exposure and development are performed using a photomask of a desired pattern to form a desired pattern.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below.

The present invention relates to a method for forming a conductive pattern using a photosensitive conductive paste, comprising forming a pattern larger than a desired pattern by partially applying a photosensitive conductive paste on a substrate on which the pattern is to be formed. By performing exposure and development using a photomask of a desired pattern to form a desired pattern,
This is a method for forming a conductive pattern, characterized by improving the use efficiency of a photosensitive conductive paste.

The use efficiency of the photosensitive conductive paste in the present invention is represented by a ratio of a paste amount remaining as a desired conductive pattern to a paste amount applied on a substrate. This ratio is the same whether it is defined by the paste weight or the paste volume, and when the coating film thickness is uniform and the film thickness after development is also the same, the photosensitive coating applied to the substrate For conductor paste area,
It is the same even if a desired conductor pattern area ratio is used.

The photosensitive conductor paste used in the present invention is not particularly limited, but a paste obtained by dispersing a metal powder with a photosensitive resin as a binder is preferably used.

The photosensitive resin is not particularly limited, but a photo-curable resin is preferably used. As the photo-curable resin, a polymer and two or more carbon-carbon It is preferable to use an organic component that is responsible for photosensitivity in the photosensitive paste and has a polyfunctional monomer having a heavy bond and a photopolymerization initiator as essential components.

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. Among these, gold, silver, and copper are more preferable because a metal having a low specific resistance is suitable. 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
If it is less than μm, when the same volume of conductive 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.

The method of partially applying the photosensitive conductor paste is not particularly limited, but screen printing is preferred. Screen printing has a proven track record of being used when forming patterns with non-photosensitive thick film conductor paste, and is a method suitable for forming coating films with a thickness of several μm to several tens of μm. is there.

When the film thickness is several μm, printing methods other than screen printing, such as intaglio printing, letterpress printing, planographic printing, and offset printing thereof, can be applied.

It is also possible to perform partial application by a coating method such as a bar coater, a roll coater, or a curtain coater, or to apply a partial paste by discharging a paste from a fine nozzle.

After coating, the coated film is heated at 70 ° C. to 100 ° C. for several minutes to 1 hour to dry the coated film.

The shape and size of a pattern formed by partial coating are determined by the shape and size of a desired pattern and the resolution of a method for performing partial coating.

When the area of the desired pattern is 50% or less of the area of the substrate, the effect of reducing the amount of the paste used according to the present invention becomes remarkable. Further, by setting the area of the pattern formed by the partial coating to be 100% or more and 200% or less of the area of the desired pattern, the use efficiency of the paste can be effectively improved.

When a stripe pattern is formed, a high-precision stripe cannot be formed by partial coating such as screen printing, so that a thin stripe may have wavy edges. If the width of the stripe formed by partial coating is not sufficiently large compared to the stripe width of the desired pattern, this waving remains even after exposure and development, and the accuracy of the finally obtained pattern is reduced. Therefore, the width of the stripe formed by the partial coating is preferably 120% or more, more preferably 150% or more of the desired stripe pattern width. If the width of the stripe formed by the partial application is not sufficiently small compared to the pitch of the desired stripe pattern, the paste is applied to a large area of the substrate by the partial application, and the amount of the paste used Cannot be reduced effectively. Therefore, the width of the stripe formed by the partial coating is preferably less than 80% of the desired stripe pattern pitch, and more preferably less than 60%.

When exposing the photosensitive conductive paste pattern partially applied, a mask having a desired pattern shape is aligned. The exposure is performed by a high-pressure mercury lamp or the like, and the exposure amount is, for example, 10 to 500 mJ / cm ^{2 as} measured by i-line (365 nm).

After the exposure, the unexposed portion of the photosensitive conductor paste is removed with a developing solution and washed with water to obtain a desired conductor pattern. These development and washing can be carried out by dipping, spraying, paddle, etc., but spray development is preferred because a pattern with higher resolution can be 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. According to the present invention, the amount of the paste removed by the developer at this time can be significantly smaller than the amount of the paste removed by the conventional method of forming a conductive pattern using a photosensitive paste.

Thereafter, firing is performed in an electric furnace, a belt furnace, or the like to volatilize organic components and sinter inorganic powder to form a conductor. The firing is performed in the air or in a nitrogen atmosphere. When the conductor powder is a metal that is easily oxidized such as copper, oxygen is added in an amount of 10 to 100 p.
800-1 in nitrogen atmosphere, hydrogen atmosphere, etc.
A pattern is created by holding at a temperature of 000 ° C. for 1 to 60 minutes and firing.

The pattern formed by the photosensitive paste of the present invention is particularly effective when the substrate is large, so that it is suitable for display use, particularly for forming display electrodes of a plasma display. MCM (multi-chip module) substrate electrodes mounted on telephones, CSP (chip size package)
The present invention is also applicable to a case where a conductor is formed on a relatively small ceramic or glass ceramic substrate, such as an electrode of a substrate for use, an electrode of a chip component such as a chip inductor or a chip capacitor, or an electrode of a module 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. The paste was adjusted as described below.

A. Silver powder 88 parts by weight Monodisperse granular Average particle size 2.0 μm Specific surface area 1.2 (m ² / g) Tap density 4.0 (g / cm ³ ) (Daido Special Steel) Polymer (in the photosensitive organic component) 8 parts by weight Glycidyl methacrylate-modified methacrylic acid-methyl methacrylate copolymer Acid value 110 Weight average molecular weight 10,000 (converted to polystyrene by gel permeation chromatography (GPC)) B. Polyfunctional monomer 4 parts by weight Propylene oxide-modified trimethylolpropane triacrylate Trifunctional monomer Double bond equivalent 157 g / mol TPA-330 (Nippon Kayaku) 1.2 parts by weight of a photoinitiator 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (Irgacure 369 of Ciba Specialty Chemicals: hereinafter referred to as IC369).

E. Solvent 10 parts by weight γ-butyrolactone F. Dispersant 0.88 parts by weight Dispersant a: "NOPCOSPARS 092" (manufactured by San Nopco) Leveling agent 2 parts by weight LC-951 (Kusumoto Kasei) (effective concentration is 10% by weight, the remainder is solvent) Glass frit 3 parts by weight Glass transition point 461 ° C .; Glass softening point 510 ° C .; Average particle size 0.9 μm; 90% particle size 1.7 μm; Top size 3.3 μm Developer 0.1% by weight aqueous solution of tetraethylammonium hydroxide.

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) Cool the polymer solution to room temperature, mix the other organic composition and metal powder, and use a motor and a stirring blade to
The mixture was uniformly mixed at room temperature at 0 rpm for 30 minutes. (3) The obtained slurry was rolled with three rolls (EXACT
Model 50) to obtain a paste.

Pattern processing The purpose was to form a stripe pattern having a width of 50 μm and a pitch of 140 μm. (1) Paste the glass substrate (12
0mm square, 1.2mm thick)
m, stripe pattern with a pitch of 140 μm (length 10
0 mm) using a screen mask (SUS # 325 mesh) and dried at 80 ° C. for 40 minutes. The thickness after drying was 10 μm. (3) The paste was exposed for 10 seconds through a pattern mask using a high-pressure mercury lamp (15 mW / cm ² ).
The pattern mask has a length pattern width of 50 μm and a pitch of 14
A negative mask having a stripe pattern of 0 μm and a length of 100 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.

In each case of the screen mask, the percentage of the ratio of the paste amount remaining as a conductor pattern after development to the paste amount applied to the substrate was defined as the paste use efficiency. Further, using each screen mask, the pattern shape after exposure and development was evaluated.

The results are all shown in Table 1.

[0040]

[Table 1]

Comparative Example 1 is a case where exposure development was performed after solid printing. In the first embodiment, a screen mask having a stripe pattern of 55 μm width was used. The undulation of the pattern during screen printing also affected after exposure and development, and the pattern shape was slightly inferior, but the paste use efficiency was as high as 91%.

In Example 2, a screen mask having a width of 60 μm was used. The pattern width was wavy at the time of screen printing, and the pattern accuracy was slightly inferior to that of Comparative Example 1 formed by solid printing because of slight influence even after exposure and development, but generally a good pattern was obtained. .

In the third embodiment, a screen mask having a width of 80 μm was used. Although a slight undulation of the pattern width was observed during screen printing, when exposure and development were performed to form a pattern having a width of 50 μm, there was no effect, and the same good pattern as in solid printing of Comparative Example 1 was obtained.

In Example 4, a screen mask having a width of 100 μm was used. There was almost no pattern undulation during screen printing, and a good pattern was obtained after exposure and development. However, the paste use efficiency was 50% as compared with the solid printing comparative example 1, and the effect of saving the paste was slightly reduced. became.

In Example 5, a screen mask having a stripe pattern of 120 μm width was used. Although the obtained pattern was good, the use efficiency of the paste was slightly low at 42%, but improved compared with the use efficiency of 35% in Comparative Example 1 for solid printing.

[0046]

According to the present invention having the above-described structure, when a conductive pattern is formed using a photosensitive conductive paste, the amount of the paste used can be effectively reduced without impairing the pattern accuracy.

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Claims (11)

[Claims] In a method for forming a conductor pattern using a photosensitive conductor paste, after a pattern larger than a desired pattern is formed by partially applying a photosensitive conductor paste on a substrate on which a pattern is to be formed, a desired pattern is formed. A method for forming a conductive pattern, comprising: performing exposure and development using a photomask having a desired pattern to form a desired pattern. 2. The method according to claim 1, wherein the area of the desired conductor pattern is 50% or less of the total area of the substrate. 3. The area of a conductor pattern formed by partial coating is 100% of the area of a desired conductor pattern.
2. The method for forming a conductive pattern according to claim 1, wherein the concentration is not less than 200% and not more than 200%. 4. A conductive pattern formed by partially applying a photosensitive conductive paste and a desired conductive pattern formed by exposure and development are both striped. Of forming a conductive pattern. 5. The conductor pattern forming method according to claim 2, wherein a desired stripe shape of the conductor pattern is such that the pitch of the stripes is at least twice the stripe width. 6. A stripe pattern formed by partially applying a photosensitive conductive paste has a width of 120% or more of a desired stripe pattern width, and is formed by partially applying the photosensitive conductor paste. The pitch of the desired stripe pattern is 80 times the pitch of the desired stripe pattern.
4. The method according to claim 3, wherein the amount is less than 0.1%. 7. A stripe pattern formed by partially applying a photosensitive conductor paste has a width of 150% or more of a desired stripe pattern width, and is formed by partially applying the photosensitive conductor paste. The pitch of the desired stripe pattern is 60 times the pitch of the desired stripe pattern.
4. The method according to claim 3, wherein the amount is less than 0.1%. 8. The method according to claim 1, wherein the use efficiency of the photosensitive conductive paste is 50% or more. 9. The method according to claim 1, wherein the method of partially applying the photosensitive conductive paste is screen printing.
The method for forming a conductor pattern according to the above. 10. The method according to claim 1, wherein at least a part of the conductor contains silver. 11. The method according to claim 1, wherein the conductive pattern is a plasma display electrode.