JPH037780A - Conductive paste composition - Google Patents

Abstract

PURPOSE:To provide the subject composition having no problem of migration and excellent impact resistance and curable with both electron rays and heat by comprising a paste resin comprising an electron ray-curable resin, an amino resin, etc., and a conductive powder in a specific ratio. CONSTITUTION:The objective composition consists essentially of (A) 5-85 pts.wt., preferably 10-50 pts.wt., of a paste resin comprising (i) 10-90wt.%, preferably 15-50wt.%, of an electron ray-curable resin [preferably an epoxy(meth)acrylate resin] and (ii) 90-10wt.%, preferably 85-50wt.%, of one kind or more of amino resins, phenolic resins, epoxy resins and polyisocyanate resins and (B) 95-15 pts.wt., preferably 90-50 pts.wt. of a conductive powder (preferably copper powder having an average particle size of 1-50mum).

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a conductive paste composition used in the electrical and electronic fields, and more specifically, to a conductive paste composition applied to electronic device parts and printed wiring boards. conductive circuit,
It relates to a paraboloid (base) having functions such as conductive connection such as terminal connection and adhesion.

Further, the paste composition of the present invention is designed to be applied to a method of curing by heating before, during, or after irradiation with an electron beam, and using a combination of electron beam curing and thermosetting.

(Prior art) In recent years, so-called paste-like conductive paints and conductive adhesives (hereinafter referred to as "conductive paints" and "conductive adhesives") have been developed, which are made by blending large amounts of finely divided silver flakes, copper powder, or carbon particles with organic polymer binders and oligomers. (together referred to as conductive paste) have been put into practical use and are widely used.

These conductive pastes are used to form conductor circuits in the manufacturing process of printed wiring boards or hybrid ICs. It is also used as a resistor in circuit formation. Furthermore, this type of paste is used not only for the purpose of circuit formation mentioned above, but also as an adhesive for various electronic parts such as membrane switches and resistors, an adhesive for liquid crystal panels, and an adhesive for liquid crystal panels.
It is also used as an ED adhesive.

Furthermore, as one of the measures to prevent electromagnetic interference, which has recently attracted attention as a social problem, applying conductive paste onto printed wiring circuits has been practiced.

In this method, the conductive paste shields electromagnetic waves generated from inside the circuit and also prevents crosstalk between wiring lines, and is becoming increasingly common.

There are severe requirements for the reliability of these conductive pastes, and for example, conductive pastes that have high heat resistance, adhesiveness, and moisture resistance are desired.

Conventionally developed conductive bases 1- use thermosetting resin as a binder, and although technological improvements such as heat resistance and adhesion are expected, they require a large amount of energy, ■Time for heating,■
This is uneconomical as it requires a large floor space for installing the heating device. In addition, the base material to which conductive paste is applied is often made of synthetic resin, and prolonged heating can cause deterioration and deformation of the base material, which can impair long-term reliability. . Therefore, there is a strong demand for a material that can be cured by heating for a short time, but there is still no satisfactory material.

Therefore, expectations are high for a method of curing conductive paste by irradiation with active energy rays such as ultraviolet rays and electron beams at or near room temperature, or by heating for a short time without causing deterioration of the base material.

However, curing with ultraviolet rays is difficult to apply to coatings containing highly concentrated conductive powder to develop conductivity because ultraviolet rays do not have the ability to penetrate fillers, and it also requires large amounts of photoinitiators and sensitizers. Because it is used for

On the other hand, curing with electron beams does not have the problems of filler limitations and deterioration of the coating film due to initiators as in ultraviolet curing.

However, it has the disadvantage that it is significantly inferior to the heat-curing type in terms of initial conductivity or a decrease in conductivity under high temperature and high humidity environments. Furthermore, there are restrictions on the thickness of the coated material due to its ability to transmit electron beams, and there are also restrictions on the shape of the coated material.

For these drawbacks, for example, Japanese Patent Application Laid-Open No. 56-90590
The publication discloses that a coating film coated with an electron beam curable paint containing a silver filler is heated after being irradiated with an electron beam. The improvement in initial conductivity achieved by this method is remarkable.

Furthermore, Japanese Patent Application Laid-Open No. 62-200703 describes a method of forming resistance circuits having various resistance values by heating an electron beam-curable resistance paste containing a carbon-based filler before, during, or after irradiation with an electron beam. is disclosed. This method was an attempt to improve the performance of the electron beam cured product by supplementarily introducing a heating step.

However, the performance of the coating films obtained using these curing systems is still not at a satisfactory level in terms of the long-term reliability currently required. In particular, when copper, nickel, or the like, which is easily oxidized in the air, is used as the conductive powder, the curing systems of the two publications mentioned above cannot provide sufficient performance.

(Problems to be Solved by the Invention) The present invention has excellent initial conductivity, maintains long-term reliability even under high temperature and high humidity environments, and is cured using a combination of electron beam and heat without migration problems. The present invention provides a type of conductive paste composition.

(Means for Solving the Problems) The present invention provides (A) (a) Electron beam curable resin 10 to
90% by weight, ([)) 5 to 85 parts by weight of a paste resin consisting of 9O-10fi% of one or more resins selected from amino resins, phenolic resins, epoxy resins, and polyisocyanate resins; (B) electrical conductivity; This is a conductive paste composition containing 95 to 15 parts by weight of powder as an essential component.

The coating film obtained from the paste composition of the present invention contains both an electron beam curable resin and one or more resins selected from amine resins, phenol resins, epoxy resins, and polyisocyanate resins, either individually or in combination. Since it contributes to curing, the strength of the coating film is greatly improved compared to systems containing only electron beam curable resin, and the properties such as heat resistance and humidity resistance are greatly improved.

Examples of the electron beam curable resin used in the present invention include resins having an unsaturated group in the molecular chain or in the side chain. Specifically, unsaturated polyester resin, polyester (meth)acrylate resin, epoxy (meth)acrylate resin, polyurethane (meth)acrylate resin, polyether (meth)acrylate resin, polyallyl compound, polyvinyl compound, polyacrylated silicone resin. and polybutadiene. Preferably, it is an epoxy (meth)acrylate resin. These resins can be used alone or in combination.

Also, monomers and oligomers having unsaturated groups for the purpose of reducing viscosity, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. In combination with acrylate, (meth)acrylic acid, dimethyl (aminomethyl) (meth)acrylate, polymethylene glycol polyacrylate, polypropylene glycol polyacrylate, trimethylolpropane triacrylate, triallyl trimellitate, triallyl isocyanurate, etc. Good too.

Examples of the amino resin, phenol resin, epoxy resin, and polyisocyanate resin used in the present invention include the following resins.

Amino resins include resins obtained by addition condensation of formaldehyde and compounds with amine groups, such as urea, melamine, benzoguanamine, and dicyandiamide, and resins obtained by reacting alcohols such as methanol, ethanol, isopropyl alcohol, and butanol. Examples include etherified resins.

A commonly used catalyst may be added to this amino resin, if necessary. Examples of the catalyst include p-toluenesulfonic acid, P-)toluenesulfonic acid amine salt, and the like.

Examples of phenolic resins include resol type resins obtained by addition condensation of phenols such as phenol, cresols, other alkylphenols, or bisphenols, and aldehydes such as formaldehyde and acetaldehyde, and resol type resins obtained by adding and condensing phenols with phenols such as phenol, cresols, other alkylphenols, or bisphenols, and aldehydes such as formaldehyde and acetaldehyde. Examples include resins that are etherified by reacting alcohols such as alcohol and butanol. In some cases, novolanc type resins can also be used.

Epoxy resins have two or more epoxy groups in one molecule, such as glycidyl ethers, glycidyl esters, glycidyl amines, linear aliphatic epoxides, alicyclic epoxides, etc. It will be done. A curing agent or catalyst may be added to this epoxy resin, if necessary.

The polyisocyanate resin has two or more isocyanate groups in one molecule, such as aliphatic polyisocyanate, alicyclic polyisocyanate,
Examples include aromatic polyisocyanates and polymers obtained by reacting these with adducting agents such as alcohols, acids, and water.

This polyisocyanate resin contains a curing agent and
Alternatively, a catalyst may be added.

These four types of resins may be used alone or in combination of two or more types. Preferred are amino resins or phenolic resins. More preferred is a melamine resin in an amine resin.

In the present invention, (a) an electron beam curable resin; (b)
The blending ratio with one or more resins selected from amino resins, phenol resins, epoxy resins, and polyisocyanate resins is 10 to 90% by weight for (a) and 90% by weight for (b).
Fire set at ~10%. When (a) is less than 10% by weight, the time required for the curing reaction is long and the curing temperature becomes high, so that warping and twisting of the coated object cannot be avoided. Also,
If the heating time exceeds 90 times, a coating film with high reliability cannot be obtained in environments such as high temperature and high humidity. Preferably, (a
) is 15 to 50% by weight, and (b+ is 85 to 50% by weight).

Examples of the conductive powder used in the conductive paste composition of the present invention include metal powders such as gold, silver, copper, nickel, chromium, palladium, aluminum, tungsten, molybdenum, and platinum, and inorganic materials coated with these metals. powder,
Or organic powder, metal oxide powder such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide,
Examples include powder coated with these metal oxides, carbon blank, graphite, and the like. These conductive powders may be used alone or in combination of two or more. In addition, the shapes are granular, spherical, flaky, scaly, plate-like,
Examples include dendritic and dice-shaped, and the average particle size is 0.
．． A thickness of 1 μm to 100 μm can be used. The conductive powder is preferably copper or nickel, more preferably one or more types of copper powder selected from dendritic copper powder, scaly copper powder, and spherical copper powder, and has an average particle size of 1 to 50 μm. Note that the average particle size refers to a volume average particle size measured by, for example, a laser diffraction method.

In the present invention, (A) (a) electron beam curable resin, (b) paste resin consisting of one or more resins selected from amino resin, phenol resin, epoxy resin, polyisocyanate resin, and (B) The blending ratio with the conductive powder is 5 to 85 parts by weight of (8) and 95 to 1 part by weight of (B).
5 parts by weight.

If (8) is less than 5 parts by weight, the coating film becomes brittle and
Conductivity decreases. Moreover, if it exceeds 85 parts by weight, conductivity cannot be obtained. Preferably, (8) is 10 to 50 parts by weight, and (B) is 90 to 50 parts by weight.

Organic fatty acids can be added to the conductive paste composition of the present invention in order to improve conductivity. The fatty acid referred to herein is an aliphatic compound having one or more carboxyl groups in one molecule.

Examples include saturated carboxylic acids, unsaturated carboxylic acids, alicyclic carboxylic acids, and the like. As specific examples, saturated carboxylic acids include acetic acid, propionic acid, acetic acid, valeric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oxalic acid, malonic acid, 12 succinic acid, glutaric acid, adipic acid, Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, oleic acid, linoleic acid, linoleic acid, fumaric acid, maleic acid, etc.; Examples of the alicyclic carboxylic acid include cyclohexanecarboxylic acid, hexahydrophthalic acid, and tetrahydrophthalic acid. These can be used alone or in combination. Further, derivatives of these can also be used. Preferred are oleic acid, linoleic acid, and lylunic acid.

The amount of organic fatty acid added is 0.05 to 10% by weight based on 100% by weight of the conductive paste composition of the present invention.

Preferably it is 0.1 to 5% by weight.

A phenolic compound can be added to the conductive paste composition of the present invention in order to improve conductivity.

The phenolic compound here refers to a compound having a phenolic hydroxyl group.

Specific examples include phenol, catechol, pyrocatechol, hydroquinone, pyrogallol, phloroglycin, gallic acid, urushiol, and the like. These can be used alone or in combination, and derivatives thereof can also be used. Preferably,
It is pyrogallol.

The amount of the phenolic compound added is 0.1 to 10% by weight based on 100% by weight of the conductive paste composition of the present invention. Preferably it is 1 to 5% by weight.

A 1,3-dicarbonyl compound can be added to the conductive paste composition of the present invention in order to improve coating film performance. The 1,3-dicarbonyl compound herein refers to a compound in which two carbonyl groups in the molecule are at the 1.3 positions.

Specific examples include acetylacetone, propionylacetone, butyrylacetone, valerylacetone, octanoylacetone, lauroylacetone, acryloylacetone, methacryloylacetone, linolylacetone,
Lylylacetone, 2.4-hexanedione, 3.5-
Examples include hebutanedione, 3,5-octanedione, and the like. These can be used alone or in combination,
Further, derivatives of these can also be used. Preferably it is acetylacetone.

The amount of the 13-dicarbonyl compound added is 0.05 to 10% by weight based on 100% by weight of the conductive paste composition of the present invention.
Weight%. Preferably, it is 01 to 5% by weight.

The fatty acids, phenolic compounds, and 1,3-dicarbonyl compounds may be used alone or in combination. In addition to being added to the conductive paste of the present invention, it may be mixed only with the conductive powder in advance, and then the conductive paste may be produced.

If necessary, dissolve the above three types of compounds in a solvent, add conductive powder into it to perform surface treatment, and then filter or directly remove the solvent to take out the conductive powder. A conductive paste may be prepared using the same method.

A volatile solvent can be added to adjust the workability of the conductive paste composition of the present invention.

Examples of volatile solvents that can be used include ketones, aromatics, alcohols, cellosolves, and esters. Specifically, methyl ethyl ketone, methyl isobutyl ketone, 3-pentanone, 2-heptanone, 3-heptanone, benzene, toluene, xylene, ethanol, propatool, butanol, hexanol, octatool, ethylene glycol, propylene glycol, methyl cellosolve, Ethyl cellosolve, butyl cellosolve, propylene glycol monoethyl ether, propylene glycol monobutyl ether, butyl carpitol, ethyl acetate, butyl acetate, cellosolve acetate, butyl carpitol acetate, etc., or a mixture thereof.

The conductive paste composition of the present invention may further contain fillers and additives, if necessary. For example, fillers include silica, kaolin, titanium oxide,
Palite, talc, mica, clay, etc. may be mentioned, and additives may include fluidity adjusting agents, antifoaming agents, dispersants, dyes, pigments, campling agents, and the like.

The method for preparing the conventional paint can be applied to the method for preparing the conductive paste composition of the present invention. for example,
Mixing using a Miki roll, mixing using a kneader, mixing using a ball mill, etc. can be used, and uniform kneading can be performed using these methods. In particular, the order in which (A) and (B) are mixed is not limited.

Various methods can be used to apply the conductive paste composition of the present invention to a substrate depending on the purpose.

Examples include coating methods such as screen printing, offset printing, gravure printing, letterpress printing, spray coating, roller coating, brush coating, casting, and spin coating.

There are no particular limitations on the substrates to be coated, and the coating can be applied to a wide range of substrates such as paper, phenol substrates, glass and epoxy substrates, plastic molded products, and metal processed products.

As a method for curing the conductive paste composition of the present invention,
After printing and coating the substrate, it is preferable to use both electron beam curing and thermosetting. However, (1) curing only by electron beams and (2) curing only by heat can also be applied.

Electron beam curing is achieved by irradiating the coated article with electron beams in air or an inert gas atmosphere. When the conductive paste composition contains a volatile solvent, the solvent may be removed at room temperature or by heating. If heated during desolvation, it can also be used for pre-irradiation heating, which will be described later. As for the electron beam irradiation method, any method can be used, including non-scanning methods such as curtain type, laminar type, broad beam type, area beam type, and pulse type, as well as low energy and medium energy scanning methods. Irradiation conditions are not particularly limited, but the current is 1 to 100 mA.
, acceleration voltage 150-1,000kV, irradiation dose 1-30
A range of Mr ad is desirable.

Curing by heat causes a reaction by heating to a temperature higher than room temperature, and heating conditions are usually selected at 50 to 250°C for several seconds to several hours.

Examples of the heating method include methods using a medium such as heated air or hot water, and methods using irradiation with infrared rays or far infrared rays, and are not particularly limited.

In addition, a curing method using a combination of electron beam irradiation and thermosetting is
This is achieved by heating before, during, and after electron beam irradiation. By using this method, a sufficient effect can be achieved by heating at a significantly lower temperature and for a shorter time than with a paste composition using a thermosetting resin as a binder.

The conductive paste composition of the present invention can be put to practical use as it is after curing, but if necessary, it can be subjected to heat aging treatment or coated with a paint for protection.

In addition to so-called wiring circuits, it can also be used for the purpose of shielding electromagnetic waves, and in some cases, it can also be used as a paint or adhesive.

Examples of its use include reinforcing screw locks or caulking,
Circuit repair, paint for volume resistors and electrodes, paint for capacitor electrodes, waveguide adhesion, liquid crystal adhesion,
Examples include adhesion of LEDs, adhesion of semiconductor elements, adhesion of potentiometers, adhesion of crystal resonators, and adhesion of micromotor carbon brushes.

(Example) The present invention will be explained in more detail with the following example.
It is not limited to these examples.

(a) Method for preparing conductive paste.

The ingredients shown below were uniformly dispersed using a three-roll mill.

(b) Method for producing a cured coating film.

Using a 200-mesh stainless steel screen plate, conductive paste was applied to a size of 1 cm in length and 1 cm in width on a single-sided copper-clad paper phenol laminate board on which a copper foil electrode part had been made in advance by Esotin lag treatment and polishing treatment. Printed. Next, the conductive paste was cured by heating and electron beam irradiation under predetermined conditions.

Heating was performed using a far-infrared device, and electron beam irradiation was performed using Unitron 200/200 manufactured by Ushio Electric 90 ■ in a CN2 gas atmosphere with an acceleration voltage of 200 kV and an absorption line fi 10 M r a
Irradiate the electron beam under the conditions of d, and the irradiation time is approximately 2
It is 0 seconds. ] was used. A thermosetting solder resist (manufactured by Taiyo Ink Manufacturing Co., Ltd., S-22) was printed on the cured conductive paste and cured at 150°C x 15m1n.

(C) Test method for cured coating film (i) Evaluation of surface condition The surface condition of the solder resist before printing is visually observed, and its smoothness is evaluated.

(11) Solder immersion test The cured coating was soaked in a molten solder bath (60 tin/4 lead) at 260°C.
0) for 10 seconds.

(iii) Moisture resistance test The cured coating film is left at a constant temperature of 60° C. and relative humidity of 90 to 95% for 500 hours.

The rate of change in volume resistivity after the tests (ii) and (iii) was calculated from the following formula.

Rate of change (%) - 1 volume resistivity (Ω·cm) = Paste film pressure (μ) Examples 1 to 7 Table 1 shows the formulation, heating conditions, and evaluation results.

Examples 8 to 13 Table 2 shows the formulations, heating conditions, and evaluation results of Examples 8 to 13.

Examples 14-19 Table 3 shows the formulations, heating conditions, and evaluation results of Examples 14-19.

1) Epoxy acrylate; 3 table 7 No. table 9 Example 20.21 Example 1 Additions shown in Table 4 using the A cured coating film was obtained under thermal conditions.

8 Comparative examples 1 to 4 Table 5 shows the formulations, heating conditions, and The results are shown below.

0 Table 5 (Effects of the Invention) The conductive paste composition of the present invention is a type that can be cured in combination with electron beam and heat without migration problems, and the conductive coating film obtained with the composition is It has excellent long-term reliability and maintains its initial performance without causing paint film defects such as peeling of the paint film, even in severe tests of resistance to thermal shock after moisture resistance tests. can.

Furthermore, damage to the object to be coated can be minimized.

Claims (1)

Scope of Claims: (A) (a) 10 to 90% by weight of an electron beam curable resin; (b) 90 to 10% of one or more resins selected from amino resins, phenol resins, epoxy resins, and polyisocyanate resins; An electrically conductive paste composition comprising, as essential components, 5 to 85 parts by weight of a paste resin consisting of % by weight, and 95 to 15 parts by weight of (B) electrically conductive powder.