JPH047369A - Electron beam curing conductive paste composition - Google Patents

Abstract

PURPOSE:To obtain an electron beam-curing conductive paste composition which hardly migrates and is improved in initial conductivity and long-term reliability under high temperature and high humidity conditions by incorporating, as essential ingredients, a compound that consists of a specific amount of Cu-based fine powder and/or Ni-based fine powder and a specific amount of an electron beam-curing resin, a specific amount of an organic fatty acid and a specific amount of a phenol compound. CONSTITUTION:A compound that consists of 60-90wt.% Cu-based fine powder and/of Ni-based fine powder (e.g. resinous Cu powder) and 40-10wt.% electron beam-curing resin (e.g. an epoxy acrylate resin); 0.05-10wt.%, based on the amount of the compound, organic fatty acid (e.g. linoleic acid); and 0.1-10wt.%, based on the amount of the compound, a phenol compound (e.g. catechol) are incorporated as essential ingredients.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an electron beam curable conductive paste composition.

More specifically, the present invention relates to a conductive paste that is cured by irradiating electron beams after being painted or printed on base materials such as electronic device parts and printed wiring boards.

(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 fine particulate silver flakes, copper powder, or carbon particles with organic polymer binders and oligomers. (abbreviated as conductive paste)
has been put into practical use and is used for a wide range of purposes.

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 above-mentioned purpose of circuit formation, but also as an adhesive for various electronic parts such as membrane switches and resistors, as an adhesive for liquid crystal panels, and as an adhesive for LEDs.

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 pastes use thermosetting resin as a binder, and although technological improvements such as heat resistance and adhesiveness are expected, they require a large amount of energy and heat to harden. It is uneconomical because it requires time, heating, and a large floor space for installing heating equipment.

Not only that, but 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 trust. . 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 at or near room temperature by irradiation with active energy rays such as ultraviolet rays and electron beams.

However, curing with ultraviolet rays is difficult to apply to highly concentrated metal-containing coatings to develop conductivity because ultraviolet rays do not have the ability to penetrate metal parts, and it also requires large amounts of photoinitiators and sensitizers. Due to its use, the paint film may deteriorate.

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.

For these drawbacks, for example, Japanese Patent Application Laid-Open No. 5690590
The publication proposes heating a coating film coated with an electron beam curable paint containing a silver filler after irradiating it with an electron beam. Although the initial conductivity is significantly improved by this method, since silver is used as a filler, there is a problem of migration, and long-term reliability is still unsatisfactory.

(Problems to be Solved by the Invention) The present invention provides an electron beam-curable conductive material that has excellent initial conductivity, maintains long-term reliability even in high-temperature and high-humidity environments, and has no migration problem. A paste composition is provided.

(Means for Solving the Problems) The present invention includes: (A) 60 to 90% by weight of copper-based and/or nickel-based fine powder;
(C) an organic fatty acid blended in a proportion ranging from 0.05 to 10% by weight based on the total amount of the formulation; (D) 0.1 to 10% by weight based on the total amount of the formulation; This is an electron beam curable conductive paste composition characterized by containing as an essential component a phenolic compound blended in a proportion within the range of .

Furthermore, the present invention will be specifically explained.

The copper-based and/or nickel-based fine powder (A) used in the present invention includes dendritic copper powder, flaky copper powder, spherical copper powder, silver-plated copper powder, silver-copper composite powder, and silver-copper alloy. powder, amorphous copper powder, carbonyl nickel powder, nickel-silver composite powder, silver-coated nickel powder, flaky nickel powder, etc.

These can be used alone or in combination. Preferably, the copper powder is one or more selected from dendritic copper powder, flaky copper powder, and spherical copper powder.

The average particle diameter of the fine powder used is 0.1 to 100 μm. Preferably, the average particle size is 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.

As the electron beam curable resin (B) used in the present invention,
Examples include resins having unsaturated groups within their molecular chains or in their side chains. Specifically, unsaturated polyester resin, polyester (meth)acrylate resin, epoxy (
meth)acrylate resin, polyurethane (meth)acrylate resin, polyether (meth)acrylate resin,
Examples include polyallyl compounds, polyvinyl compounds, polyacrylated silicone resins, and polybutadiene. Preferably, it is an epoxy (meth)acrylate resin. These resins can be used alone or in combination.

In addition, 7mers and oligomers with unsaturated groups for the purpose of reducing viscosity, such as methyl (meth)acrylate, (meth)
Ethyl acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, dimethylaminomethyl (meth)acrylate, poly (methylene glycol) polyacrylate, poly( Propylene glycol) polyacrylate, trimethylolpropane triacrylate, triallyl trimellitate, triallyl isocyanurate, etc. may be used in combination.

The organic fatty acid (C) used in the present invention is an aliphatic compound having one or more carboxyl groups in the 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, butyric acid, valeric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimeline. Unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, oleic acid, linoleic acid, linoleic acid, fumaric acid, maleic acid, etc. Alicyclic carboxylic acids include
Examples include cyclohexanecarboxylic acid, hexahydrophthalic acid, and tetrahydrophthalic acid. These can be used alone or in combination, and derivatives thereof can also be used.

Preferred are oleic acid, linoleic acid, and lylunic acid.

The phenolic compound (D) used in the present invention 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.

In the present invention, the blending ratio of (A) copper-based and/or nickel-based fine powder, and (B) a compound having a ray-reactive group is 60 to 90% by weight for (A) and 40 to 10% by weight for (B). % by weight, (C) organic fatty acid is 0.05 to 10% by weight, and (D) phenolic compound is 0.05% by weight based on the total amount of (A) and (B). It ranges from 1 to 10% by weight.

When (A) is less than 60% by weight, the conductivity is insufficient, and when it exceeds 90% by weight, the coating film becomes brittle and the conductivity decreases. When (B) exceeds 40% by weight, conductivity cannot be obtained, and when it is less than 10% by weight, the coating film becomes fragile.

(^) , (C) is 0.0 for the component consisting of (B)
If it is less than 5% by weight, conductivity cannot be obtained, and 1
If the content is 0% by weight, the coating film becomes brittle and (D) is 0.1
If it is less than 10% by weight, conductivity cannot be obtained;
If it exceeds this, the coating film becomes brittle.

Preferably, (A) is 70 to 90% by weight and (B) is 30% by weight.
-10% by weight, C) is 0.1-5% by weight, and (0) is 1-5% by weight relative to the components (A) and (B).

A 1,3-dicarbonyl compound can be added to the conductive paste 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 heptanedione and 3.5-octanedione. These can be used alone or in combination, and derivatives thereof can also be used. Preferably it is acetylacetone.

A volatile solvent can be added to adjust the workability of the conductive paste of the present invention. As a volatile solvent,
For example, ketones, aromatics, alcohols, cellosolves, esters, etc. can be used.

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 motuptyl ether, butyl carpitol, ethyl acetate, butyl acetate, cellosolve acetate, butyl carpitol acetate, etc., or a mixture thereof. be.

The conductive paste of the present invention may further contain fillers and additives, if necessary.

For example, fillers include gold, silver, carbon, silica, kaolin, titanium, halides, talc, mica, clay, etc., and additives include flow regulators, antifoaming agents, dispersants, dyes, pigments, Coupling agents and the like can be mentioned.

The method for preparing the conventional paint can be applied to the method for preparing the conductive paste of the present invention.

For example, mixing using three rolls, mixing using a kneader,
Examples include mixing using a ball mill, which allows uniform kneading and preparation.

In particular, the mixing order of the components (A), (B), (C), and (D) is not limited.

Various methods can be used to apply the conductive paste of the present invention to a base material depending on the purpose. Examples include screen printing, offset printing, gravure printing, letterpress printing, and coating methods such as spray coating, roller coating, spacing coating, casting, and spin coating.

The substrate to be coated is not particularly limited, and can be applied to a wide range of substrates such as paper, phenol substrates, glass/epoxy substrates, plastic molded products, and metal processed products.

The conductive paste of the present invention may contain a thermosetting resin in addition to the electron beam curable resin, if necessary. Examples include epoxy resin, urethane resin, phenol resin, melamine resin, urea resin, benzoguanamine resin, diallyl phthalate resin, thermosetting silicone resin,
Mention may be made of maleimide resins. Among these resins, epoxy resins and urethane resins require the combined use of a curing agent or catalyst.

The conductive paste of the present invention is printed or painted on a base material, and if it contains a volatile solvent, the volatile solvent is removed at room temperature or by heating as necessary, and then the paste is exposed to air or an inert gas. It can be cured by irradiating it with an electron beam in an atmosphere.

Further, after removing the volatile solvent, heating may be further performed, and then electron beam irradiation may be performed.

Regarding electron beam irradiation methods, curtain type, laminar type, broad beam type, area beam type,
Any method can be used, such as a non-scanning method such as a pulse type, or a low energy or medium energy scanning method. The irradiation conditions are not particularly limited, but the current is 1 to 100 mA, the acceleration voltage is 150 to 1.0 OOkV, and the irradiation dose is 1 to 30 Mra.
A range of d is desirable.

Further, the conductive paste of the present invention may be heated during electron beam irradiation.

The conductive paste of the present invention can be put to practical use as it is after being cured by electron beam irradiation, but it may also be subjected to heat aging treatment or coated with a protective coating if necessary. It is possible.

In the composition of the present invention, there are no particular restrictions on the means of heating performed before, during or after electron beam irradiation, and widely used methods such as heating with hot air, dielectric heating, far infrared rays, etc. heating can be used.

The heating time and temperature vary depending on the paste composition used, and conditions may be selected to maximize the electrical conductivity and properties of the coating film. For example:
50"C for 15 minutes or 270'C/20 seconds. Preferably, the temperature is 100 to 250°C for 30 minutes to 15 seconds.
More preferably, the heating time is 120 to 220°C for 15 minutes to 30 seconds. Note that the heating temperature here indicates the surface temperature of the object to be coated.

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 screw locks, reinforcing caulking, circuit repair, volume resistance and electrode paint, capacitor electrode paint, waveguide adhesion, liquid crystal adhesion, and LE.
Examples include adhesion of D, semiconductor element adhesion, potentiometer adhesion, crystal resonator adhesion, and micromotor carbon brush adhesion.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.
It is not limited to these examples.

(a) Method for preparing conductive paste: The various components shown in the table below were uniformly dispersed using a three-roll roll.

(b) Preparation of cured coating film: Using a 200-mesh stainless steel screen plate, apply the conductive paste vertically onto a single-sided copper-clad paper phenol laminate on which copper foil electrodes have been made by etching and polishing. I printed it in a size of 1c1111 x 11.

Next, after removing the solvent with a far-infrared dryer at 200°C
0/200) at an accelerating voltage of 20 in a N gas atmosphere.
The conductive paste was cured by irradiation with an electron beam under the conditions of 0 kV and Ill radiation absorption of 10 Mrad. Furthermore, a thermosetting solder resist (
Print S-22) made by Taiyo Ink Seisakusho and heat at 150°C.
It was cured in 15 minutes.

(C) Test method for cured coating film; (1) Surface condition evaluation: The surface condition before printing the solder resist is visually observed and its smoothness is evaluated.

(ii) High temperature storage test: The cured coating film was left in a dryer at 100°C for 1,000 hours.

(ii) 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 (11) and (ii) was calculated using the following formula.

Rate of change (%) = Volume resistivity value (Ω·cm) = Paste film thickness (μ) Examples 1 to 8 Table 1 shows the formulations of Examples 1 to 8 and their evaluation results.

Examples 9-12 Table 2 shows the formulations of Examples 9 to 12, and its reviews The results are shown below.

Table 2 Example 13 When obtaining the cured coating film of Example 1, 180' at the time of electron beam irradiation
Heating was performed for approximately 20 seconds.

As a result, the volume resistivity value was 7×10 −Ω·1, the surface condition was smooth, the rate of change in the high temperature storage test was -14%, and the rate of change in the humidity test was -6%.

Example 14 The cured coating film of Example 1 was post-heated at 160° C. for 4 minutes.

As a result, the volume resistivity value was 8 x 10-'Ω·1, the surface condition was smooth, the rate of change in the high temperature storage test was -18%, and the rate of change in the humidity test was -7%.

Comparative Examples 1 to 4 Table 3 shows the formulations of Comparative Examples 1 to 4 and their evaluation results.

(Effects of the Invention) In the present invention, organic fatty acids and phenolic compounds are blended into the copper-based or nickel-based conductive paste, so there is no migration problem unlike the silver thread conductive paste, and the initial conductivity An electron beam-curable conductive paste that has excellent properties and maintains long-term reliability even under harsh environments can be obtained.

(1 other person) Table 3

Claims (1)

[Claims] (A) Copper-based and/or nickel-based fine powder 60-90
% by weight, (B) a compound consisting of 40 to 10% by weight of electron beam curable resin, and (C) 0.05 to 0.05 to the total amount of the compound.
Organic fatty acids, (D
) An electron beam curable conductive paste composition characterized in that it contains as an essential component a phenolic compound blended in a proportion ranging from 0.1 to 10% by weight based on the total amount of the blend.