JPS63154773A - Photo-curable electrically conductive fired paste - Google Patents

Abstract

PURPOSE:To obtain a photo-curable electrically conductive fired paste having improved dispersibility, by forming a fired paste contg. an electrically conductive fine powder, glass frit, a metal oxide, a photo-curable resin compsn. and a specified reaction product. CONSTITUTION:Fired paste contains electrically conductive fine powder (A), glass frit (B), a metal oxide (C), a photo-curable resin compsn. (D) and further a reaction product (E) of an aliph. monocarboxylic acid having an unsaturated double bond with maleic anhydride. The compsn. (D) is a compsn. contg. a polymer or copolymer of a (meth)acrylic ester, a photo-curable monomer and a photo-polymerization initiator as essential ingredients. The reaction product (E) is used in an amount of 0.05-10wt% based on that of the paste. When the amount is less than 0.05wt%, the electrically conductive fine powder and the resin compsn. are poorly dispersed, while when the amount is more than 10wt%, the photo-curability is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a photocurable conductive firing paste using a photocurable resin composition as a binder.

<Prior art> Conventionally, the method of forming a conductive circuit on a ceramic substrate is to use a conductive circuit made of conductive fine powder such as colored silver, molybdenum, tungsten or palladium, a low-melting glass frit, a metal oxide, an organic vehicle, etc. A common method is to print a circuit pattern directly on a ceramic substrate such as alumina with a firing paste, dry it, and then fire it.

<Problems to be solved by the invention> However, since such firing pastes contain high-boiling point solvents, (1) drying time is long, (2) pinholes and other problems occur due to clogging of the screen plate. It has many problems such as easy line width distortion, (3) significant pollution of the workplace environment, and (4) difficulty in continuous printing due to large changes in the viscosity of the paste over time.

In addition, in order to solve these problems, for example,
4-41491 etc., it has been proposed to use a photocurable resin composition as a binder; however, (1) the thermal decomposition temperature of the cured binder is high and the sinterability is not good;
2) Therefore, poor conductors are likely to be formed due to pinholes, curls, or carbon residue that occur during firing, (3)
(4) Poor dispersibility between the conductive fine powder and the photocurable resin composition, resulting in poor storage stability; (4) Poor dispersibility between the conductive fine powder and the photocurable resin composition, resulting in poor printing and baking Another problem is that the adhesive strength between the ceramic substrate and the conductor is low.

Means for Solving the Problems> A binder with good thermal decomposition properties has already been proposed by some of the inventors (Japanese Patent Laid-Open No. 152993/1983).
. However, subsequent tests revealed that this proposal did not necessarily provide sufficient dispersibility of the conductive fine powder.

In order to overcome this drawback, the present inventors conducted extensive research and found that a compound obtained by adding an aliphatic monocarboxylic acid having one or more unsaturated double bonds in the molecule and maleic anhydride. The present invention was achieved based on the discovery that the dispersibility was greatly improved.

That is, the present invention provides a photocurable conductive baking paste containing a conductive fine powder (A), a glassy frit (B), a metal oxide (C), and a photocurable resin composition (D), further comprising: The paste is a photocurable conductive fired paste characterized in that the paste contains a reaction product (E) of an aliphatic monocarboxylic acid having one or more unsaturated double bonds in the molecule and maleic anhydride. . The conductive fine powder (A) used in the present invention includes, for example, noble metal powder such as gold, silver, palladium, and platinum, and base metal powder such as copper, tungsten, molybdenum, nickel, and aluminum. Its content is 40-90% by weight of the fired paste of the invention. If the content is less than 40% by weight, the conductivity of the formed circuit will decrease and it will be difficult to form a stable circuit;
If it exceeds % by weight, the viscosity of the fired paste of the present invention becomes extremely high, making printing difficult.

The vitreous material (B) used in the present invention includes, for example, lead oxide, boron oxide, silicon oxide, sodium oxide,
Calcium oxide, etc., and its content is 0.1 to 15% by weight of the fired paste of the present invention. Its content is 0
．． If it is less than 1% by weight, the conductor circuit will have poor adhesion to the ceramic substrate, while if it exceeds 15% by weight, the solder wettability will be poor.

- Sumo wrestlers LJ 0.1~ of baking paste
It is 15% by weight. If the content is less than 0.1% by weight, the adhesion of the conductor circuit to the ceramic substrate will be poor, while if it exceeds 15% by weight, the solder wettability and conductivity will be reduced.

Next, the photocurable resin composition (D) used in the present invention contains as essential components a polymer or copolymer of methacrylic ester or/and acrylic ester, a photocurable upper layer, and a photoinitiator. It contains. Examples of polymers or copolymers of Nisdel methacrylate and/or acrylic ester include methyl (meth)acrylate (indicated by acrylic acid methyl ester and methacrylic acid methyl ester, hereinafter similarly abbreviated), (
Meta) Acrylic! ! :% chill, (meth)acrylic acid-
(meth)acrylic acid alkyl esters such as n-butyl; (meth)acrylic acid alkyl esters such as cyclohexyl (meth)acrylate;
It is a polymer or copolymer of (meth)acrylic acid aralkyl esters such as acrylic acid cycloalkyl esters and (meth)acrylic acid benzyl esters. The copolymer component may contain a small amount of a polymerizable monomer other than (meth)acrylic ester.

Photocurable monomers include (1) styrene compounds such as styrene and α-methylstyrene, (2) methyl (meth)
acrylate, mono(meth)acrylate compounds such as ethyl(meth)acrylate, and tetrahydrofurfuryl(meth)acrylate; (3) ethylene glycol di(
meth)acrylate, alkylene glycol di(meth)acrylate compounds such as 1,6-hexanethiol di(meth)acrylate, (4) polyhydric compounds such as trimethylolprobant IJ (meth)acrylate, pentaerythritol tetra(meth)acrylate, etc. (meth)acrylate compounds, etc.

The photoinitiator is a photoinitiator such as a benzoin compound, a benzophenone compound, or a thioxanthone compound.

The amount of the (meth)acrylic powder ester polymer or copolymer in the photocurable resin composition is 5 to 50% by weight JB7.
The amount of photocurable monomer is preferably 95 to 50% by weight. The amount of the photoinitiator is preferably 1 to 10% by weight in the photocurable resin composition.

The content of the photocurable resin composition (D) is 5 to 50% by weight of the fired paste of the present invention. The content rate is 51i! If it is less than %, the viscosity of the paste will become high and printing will be difficult, while if it exceeds SOZ %, it will be difficult to obtain a circuit with good conductivity.

Known thermal polymerization inhibitors, leveling agents, antifoaming agents, thickeners, thixotropic agents, etc. are added to the photocurable resin composition (D) to adjust viscosity, storage stability, printability, etc. It is commonly used.

Next, the core of the present invention lies in the addition of a compound (E) between an aliphatic moacarboxylic acid having one or more unsaturated double bonds in the molecule and maleic anhydride. Examples of aliphatic monocarboxylic acids having one unsaturated double bond in the molecule include:
1) Acrylic acid, methacrylic acid, butenoic acid, rotonic acid, vinyl acetic acid, tiglic acid, oleic acid, etc.

Examples of aliphatic monocarboxylic acids having two unsaturated double bonds in the molecule include 11) 2,4-pentadiene, diallylic acid p, i, a-dodecadienoic acid, and linoleic acid. Examples of aliphatic monocarboxylic acids having three or more unsaturated double bonds in the molecule include 1it)2
, 4.6-octatrienoic acid, lylunic acid, arachitic acid, etc.

Friendship product (E) of an aliphatic monocarboxylic acid having one or more unsaturated double bonds in the molecule of the present invention and maleic anhydride
The content of the fired paste of the present invention is 0.05 to 10!
fi%. If the content is less than O,OS weight percent, the dispersibility of the conductive fine powder and the photocurable resin composition will be poor, while if it exceeds 10 weight percent, the photocurability will be poor.

In the present invention, the conductive fine powder (A), the glassy frit (B), the gold jI oxide (C), and the photocurable resin composition (D
) and a reaction product (E
) is used as an essential component to print a circuit on a ceramic substrate such as alumina, and after photo-curing, it is fired to obtain a conductive circuit.

In the present invention, since the firing paste used for printing is a photo-curable conductive firing paste, it does not contain any solvent and therefore does not cause pinholes or line width distortion due to clogging of the screen plate. Further, since the conductive fine powder (4) has good dispersibility, it has the great feature that it can be used stably for a long period of time.

Regarding the fired paste of the present invention, there are no particular limitations on the conditions for photocuring. The light source used for light irradiation is sunlight,
Chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, etc. are used. As the substrate, an alumina substrate, a hollow substrate, a beryllia substrate, an aluminum nitride substrate, a silicon carbide substrate, etc. are used.

<Effects of the Invention> The excellent effects of the photocurable conductive firing paste of the present invention include the following points.

(1) Since the firing paste used is a photocurable conductive firing paste, it does not contain any solvent, and no pinholes or line width distortions occur due to clogging of the screen plate.

(2) Therefore, continuous printing of precise patterns is possible.

(3) Good storage stability due to good dispersibility with conductive fine powder.

(4) Because the conductive fine powder has good dispersibility, printing and
After firing, the adhesive strength between the ceramic substrate and the conductor is excellent.

<Examples> Examples will be given to explain the present invention in more detail, but
The present invention is not limited in any way by these Examples. In the examples, parts or % indicate parts by weight or % by weight, respectively.

Measurements for performance evaluation were performed using the following method.

Printability: Circuit pattern shown in Figure 1 (vertical 3.5αx
aa, o cm) was printed using a 400-mesh stainless steel screen plate, and the printability was measured by the number of prints until the stainless steel screen plate became clogged or the fine lines burned.

Conductivity: The resistance value of the circuit shown in FIG. 1 formed on a ceramic substrate was measured.

Firing properties: After printing the circuit pattern shown in Figure 1, the ceramic substrate was heated to 850°C for 15 minutes, held at 850°C for 10 minutes, and then cooled to room temperature for 10 minutes to eliminate pinholes and circuit caulking wires. The presence or absence was determined.

Storage stability: The photocurable conductive baking paste 50 was placed in a polyethylene container (100m7) and left in a dark place at 25°C for one month to examine storage stability.

Adhesive strength: formed on a ceramic substrate! On the square pad (2ta x 2m+) shown in Figure 1, a diameter of 0.6
A 5 m tin-plated copper wire was soldered with eutectic solder, and the tin-plated copper wire was stretched perpendicularly to the ceramic substrate by σ1, and the bonding strength at P was measured.

Production Example 1 Methyl methacrylate (MMA) with an average molecular weight of 75,000
)-n-butyl methacrylate (n-BMA) copolymer (M M A / n -H M A = 40 / 6
0, weight ratio) 30 parts, tetrahydrofurfuryl acrylate 50 parts, lauryl acrylate 5 parts, polypropylene glycol (adduct of 9 moles of propylene oxide)
7 parts of diacrylate, 2 parts of benzyl dimethyl ketal and 2 parts of 2-dithylanthraquinone as photoinitiators, and 4 parts of a linoleic acid-maleic anhydride reaction product were mixed and dissolved at room temperature to form a photocurable resin composition (I). I got it. Similarly, photocurable resin compositions (If) and (m) containing copolymers and photocurable monomers as shown in Table 1 were obtained. As the photoinitiator, the same compound and the same amount as in (I) were used.

Next, 75% fine silver powder and glass frit [ASF-
1380 (manufactured by Asahi Glass Co., Ltd.), 6% bismuth oxide, and 15% of the photocurable resin composition (I) were thoroughly kneaded using a three-roll ceramic roll to obtain a photocurable conductive baking paste (I). ) was obtained. Similarly, photocurable conductive firing pastes (■ and (■')) were prepared using the photocurable resin compositions (■) and (11), respectively.

Table 1 (*2) Tetrahydrofurfuryl acrylate (*3)
Lauryl acrylate reference production example 1 30 parts of methyl methacrylate-n-butyl methacrylate copolymer (mentioned above) having an average molecular weight of 75,000, 50 parts of tetrahydrofurfuryl acrylate), 5 parts of lauryl acrylate, polypropylene glycol ( Adduct of 9 moles of propylene oxide) 7 parts of diacrylate, 2 parts of benzyl dimethyl ketal and 2 parts of 2-dithylanthraquinone as photoinitiators, and 4 parts of sodium dodecylbenzenesulfone were mixed and dissolved at room temperature to form a photocurable resin composition. (I
V) was obtained. Similarly, a photocurable resin composition (IV
) and (Vl) were obtained. As the photoinitiator, the same compound and the same amount as in (IV) were used.

Next, 75% fine silver powder and glass frit [ASF-
1380 (manufactured by Asahi Glass Co., Ltd.), 6% bismuth oxide, and 1 s% of photocurable resin composition (IV) were thoroughly kneaded using a three-roll ceramic roll to form a photocurable conductive firing paste (■ Similarly, using photocurable resin compositions (V) and (■), photocurable conductive pastes) (V and (■) were obtained.Reference Production Example 2 Average molecular weight: 175, 000 methyl methacrylate-n-butyl methacrylate copolymer (mentioned above), 30 parts, solvent (terpineol/toluene = 7 o/a O.

A solvent-type resin composition (■) was obtained by mixing and dissolving 70 parts of the mixture at room temperature. Next, 75% silver fine powder, 4% glassy frit CASF-1380 (manufactured by Asahi Glass Co., Ltd.), 6% bismuth oxide, and a solvent-based resin composition (~'ll) 1
s% was thoroughly kneaded using a three-roll ceramic roll to obtain one solvent-type conductive fired paste (~).

Table 2 *6) Tetrahydrofurfuryl acrylate *7) Lauryl acrylate *8) Polypropylene glyfur [(propylene oxide (po) adduct)] diacrylate *9) Terpineol/toluene - 70/30 (weight ratio) Examples 1 Alumina substrate (alumina content 96%, vertical 5α x horizontal 5
cm x thickness 0.6 m), use a stainless steel screen plate to make a circuit pattern using photocurable conductive firing paste (I'). Continuous stamping. In this case, even if the number of printed sheets exceeded 500, no clogging of the screen plate or fine line burning occurred. This printed alumina substrate is 5゜6
The fired paste was cured by irradiation for 10 seconds at a distance of 15G under a KW water-cooled high-pressure mercury lamp. Next, this aluminum-deficient substrate was fired under the above-mentioned firing conditions, and then the firing properties, conductivity, and adhesive strength were measured. The results are shown in Table 3. Separately, the storage stability of this photocurable conductive firing paste (1) was investigated.The results are also shown in the third column.

Example 2 Photocurable conductive baking paste in Example 1 (photocurable conductive baking paste instead of ■) (II and (
A conductive circuit was formed on an alumina substrate using the following materials. The results are shown in Table 3.

Comparative Example 1 A circuit pattern was continuously printed on the alumina substrate of Actual Foil Example 1 using a photocurable conductive firing paste (IV'l) using a stainless steel screen plate.The printed alumina substrate was
．． 6 Under KW water-cooled high-pressure mercury lamp, 1 at a distance of 15 crn
It was cured by irradiation for 0 seconds. Next, the printed alumina substrate was fired under the above-mentioned firing conditions, and then the firing properties, conductivity, and adhesive strength were measured.

The storage stability of a separately used photocurable conductive hooding paste (1V) was investigated.The results are shown in Section 4.

Comparative Example 2 Solvent-based firing paste (W) on the alumina substrate of Example 1
The circuit pattern was printed continuously using This printed alumina substrate was dried at 150° C. for 20 minutes. Next, the printed alumina substrate was fired under the above-mentioned firing conditions, and then the firing properties, conductivity, and adhesive strength were measured. Separately, the storage stability of the solvent-based conductive firing paste (■') used was investigated.

The results are shown in Table 4.

[Brief explanation of the drawing]

FIG. 1 shows a printed circuit pattern. Patent applicant: Toyobo Co., Ltd. Akira lI! l

Claims (1)

[Claims] In the photocurable conductive firing paste containing conductive fine powder (A), glassy frit (B), metal oxide (C), and photocurable resin composition (D), the paste further contains 1. A photocurable conductive baking paste characterized by containing a reaction product (E) of an aliphatic monocarboxylic acid having one or more unsaturated double bonds and maleic anhydride.