JP2654067B2 - Conductive copper paste - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a conductive copper paste used for single-sided and double-sided printed circuit boards called a single-sided multilayer board or a jumper circuit among printed circuit boards.

[Conventional technology]

Printed circuit boards include single-sided boards, double-sided boards and multilayer boards.Paper-reinforced phenolic copper-clad laminates and glass fiber reinforced epoxy resins are required in terms of the functions, reliability and cost required for the electrical equipment to be manufactured. Materials such as copper-clad laminates are properly used. In order to improve the workability of a single-sided board, it is inevitable to increase the cost by changing the material and increasing the number of processing steps. As a method of avoiding this, an insulating ink (undercoat agent) is applied to the circuit portion on the single-sided board except for necessary terminals by screen printing, and a conductive paste is further applied to the circuit portion by screen printing. Is generally connected to the terminal portion of the original circuit, and the whole is further coated with an insulating ink (overcoat agent) to obtain a finished product. The pattern drawn using this conductive paste is called a jumper wire, and the completed printed wiring board is called a single-sided multilayer board.

The conductive paste used here generally uses epoxy resin or phenol resin as a binder, and silver powder as conductive particles. Reliability has come to be required. In other words, fine patterning of circuits is becoming essential in order to realize light and thin electronic devices, but circuits using silver-based
When a direct current is applied under moisture, a so-called "silver transfer phenomenon" occurs, and the circuit is shortened, causing not only destruction of electronic equipment but also various adverse effects.

Various measures have been devised to avoid this.
For example, it is common to replace a part of silver powder with an alloy such as vanadium, or to use a conventional silver paste to increase the number of undercoat and overcoat agent application circuits to suppress the silver transfer phenomenon. It is being done. However, both methods have a limited effect, and cannot cope with higher reliability of electronic devices.

Further, as a method of avoiding the silver migration phenomenon, there is a method in which silver powder is not used for the conductive particles, that is, a method in which conductive particles such as nickel and copper are used instead of silver powder. Nickel and copper are both base metals and are inexpensive compared to silver in terms of price, but those using nickel powder are inferior in conductivity although having excellent aging stability, while those using copper powder are: Although the initial conductivity is satisfactory, the oxidation of the copper powder gradually progresses with the passage of time, and the conductivity decreases, and the long-term reliability is unsatisfactory. The conductive copper paste is
It is necessary to carry out the curing in an atmosphere of an inert gas such as nitrogen, and there are difficulties in handling methods and equipment.

[Problems to be solved by the invention]

The performance required for conductive copper paste for jumper circuits is, of course, low electrical resistance, good screen printability, and high adhesion to the board,
In recent years, as its applications have expanded, high reliability has been required, and in particular, the requirements for resistance stability against insulating coating agents such as undercoating agents and overcoating agents, and resistance stability against heat and humidity have become severe. .

However, the conventional conductive copper paste for jumper circuits uses an epoxy resin or a phenol resin alone, so that the electric resistance value is not so low,
Although excellent in coating film hardness, that is, mechanical strength and solvent resistance, there is a weak point against the impact peculiar to these resins,
There were difficulties in the large change in resistance value when immersed in a solder bath at 0 ° C., and in the electrical and mechanical properties against thermal shock.

In addition, conductive copper paste with low electrical resistance, well-balanced printability, adhesion, insulation coating resistance, solder heat resistance, heat / moisture resistance, thermal shock resistance, etc. has not yet been obtained. It is.

[Means for solving the problem]

The present inventors, in view of such circumstances, as a result of intensive research to obtain a paste without such defects,
By using a modified hydroquinone resin and a modified epoxy resin together as a binder for the conductive copper paste, the electric resistance is low, the adhesion to the base material is improved, the screen printability is good, heat resistance, moisture resistance, solder heat resistance The present inventors have found that a one-pack type conductive copper paste having good thermal shock resistance and no need for curing in an inert atmosphere can be obtained, and the present invention has been completed.

That is, the present invention provides: (1). Conductive powder mainly composed of copper powder, a reducing resin and an epoxy resin as main components, and the modified epoxy resin has an alkyl group having 4 or more carbon atoms in a graft polymer of an epoxy resin and a vinyl polymer. (2) a conductive copper paste, wherein a vinyl polymer mainly composed of an alkyl acrylate is uniformly dispersed with a particle size of 0.5 μm or less; 2. The conductive copper paste according to the above item 1, wherein the reducing resin is a modified hydroquinone resin, (3). 3. The conductive copper paste according to the above item 1 or 2, wherein the conductive powder is copper powder or a composite powder of copper and silver, (4). (5). The conductive copper paste according to any one of (1) to (3) above, wherein the ratio of the reducing resin to the modified epoxy resin is 100: 80 to 100: 10. 5. Any of the above items 1-4, wherein the ratio of the conductive powder to the total of the reducing resin and the modified epoxy resin is conductive powder: (reducing resin + modified epoxy resin) = 400: 100-900: 100. Or a conductive copper paste described in the above.

The modified hydroquinone resin used in the present invention is obtained as follows.

Hydroquinones used in the modified hydroquinone resin include hydroquinone, catechol, and alkyl- or alkenyl-substituted products thereof. These substituents include t-butylhydroquinone, urushiol, laccol, and thiol. Of these, three compounds other than t-butylhydroquinone are the main components of lacquer and are natural products. The purity, composition ratio, etc. of natural lacquer vary slightly depending on the production region, such as Japan, China, Korea, Burma, and Thailand. In these natural lacquers, it is known that the oxidative coupling reaction between urushiol quinone and urushiol is repeated by the catalytic action of the enzyme laccase to form a three-dimensional structure coating film. The enzyme laccase is a copper complex and participates in the redox action between urushiol and urushiolquinone.

Focusing on these redox mechanisms, the present inventors have reduced copper powder that is easily oxidized using hydroquinone and catechol that are industrially manufactured, easily available, and stable in quality. A reducing resin was obtained as follows based on the idea of making a paste.

That is, hydroquinones are dissolved together with phenols in a solvent such as ethylene glycol monomethyl ether and the like, and a condensation reaction is carried out with a formalin aqueous solution of about 37% by weight under an alkali catalyst to obtain a resol type hydroquinone resin.
Phenols used here include phenol,
p-cresol, t-butylphenol and the like. Any alkali catalyst may be used as long as it causes a condensation reaction to generate a resole-type hydroquinone resin, but an aqueous ammonia solution is easily available, inexpensive and preferable.

The modified epoxy resin used in the present invention is obtained as follows.

First, the epoxy resin that can be used in the present invention may be any commonly used polyvalent epoxy resin, and if it is liquid, it is convenient to prepare it into a paste. Novolak epoxy resins such as glycidyl compounds such as phenol novolak and cresol novolak are preferred from the viewpoint of heat resistance and electrical characteristics. Other epoxy resins include a glycidyl-type epoxy resin obtained by reacting a compound having two or more active hydrogens in one molecule with epichlorohydrin or 2-methylepichlorohydrin, butadiene dimer epoxide. And at least one epoxy resin selected from alicyclic epoxy resins such as dicyclopentadiene epoxide and the like.

Here, examples of the compound having two or more active hydrogens in one molecule include polyphenols such as bisphenol A, bishydroxyphenylmethane, resorcinol, bishydroxydiphenyl ether, and tetrabromobisphenol A; Polyhydric alcohols such as pentyl glycol, glycerin, trimethylolpropane, pentaerythritol, triethylene glycol, polypropylene glycol, bisphenol A-ethylene oxide adduct and trishydroxyethyl isocyanate; polyamino compounds such as ethylenediamine and aniline; adipic acid, phthalic acid, And polyvalent carboxyl compounds such as isophthalic acid.

Next, the modified epoxy resin used in the present invention is typically a method in which a vinyl monomer is polymerized in the presence of the above-described epoxy resin, and a graft polymer of the epoxy resin and a vinyl polymer is first produced.

Examples of the vinyl monomer used herein include alkenyl aromatics such as styrene and vinyl toluene; acrylic esters such as methyl methacrylate, dodecyl methacrylate, methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, and trimethylolpropane triacrylate. Acrylic compounds having no ester group such as acrylonitrile, acrylic acid, butoxymethylacrylamide and methacrylamide; non-conjugated vinyl such as vinyl acetate, vinyl laurate, vinyl versatate, vinyl chloride, vinylidene chloride, ethylene and acryl acetate Compounds: conjugated diene compounds such as butadiene, isoprene and chloroprene are typical, and dibutyl fumarate, monomethyl Rate, it is possible to use a polymerizable vinyl compound such as diethyl itaconate.

In order to polymerize the above vinyl monomer into a vinyl polymer, a radical initiator such as lauroyl peroxide, benzoyl peroxide, t-butyl benzoate, dimethylbenzoyl peroxyhexane, t
-Butyl barbirate, ditertiary butyl peroxide, 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane, dimethyl ditertiary butylperoxyhexane, t-cumyl peroxide, cumene hydroperoxide Typically, radical polymerization is performed using an azo compound such as azobismethylvaleronitrile, a peroxide such as t-butylperoxymaleic acid, succinic peroxide, t-butylperoxyisopropyl carbonate, or hydrogen peroxide. is there. If necessary, a so-called redox polymerization may be carried out in combination with a reducing agent, and a polymerization initiator such as hydroquinone and a chain transfer agent such as dodecyl mercaptan may be used.

In order to promote grafting, it is effective to introduce a polymerizable double bond or a graftable chemical bond into the epoxy resin. Examples of the method for introducing a polymerizable double bond include, for example, acrylic acid, acrylamide, methylol acrylamide, butoxymethyl acrylamide, hydroxyethyl methacrylate, maleic anhydride, monoethyl itaconate, monobutyl fumarate, chloromethyl styrene, and phosphoxyethyl. A typical method is to react a compound having a functional group and a polymerizable double bond such as methacrylate, chlorohydroxybutyl methacrylate, parahydroxypropyl methacrylate, parahydroxystyrene, and dimethylaminoethyl methacrylate with an epoxy resin in advance. is there.

In the present invention, the epoxy resin or the vinyl polymer may remain free in the graft polymer without being grafted.

The modified epoxy resin, in the presence of the above-described graft polymer of the epoxy resin and the vinyl polymer, further polymerized a monomer forming a soft vinyl polymer by a conventional method, and the soft vinyl polymer was dispersed as substantially spherical particles. Obtained as a composition.

The soft vinyl polymer used in the present invention includes:
The polymer is preferably polymerized mainly with an acrylate monomer having an alkyl group having 4 or more, preferably 20 or less carbon atoms. With a polymer mainly composed of an alkyl acrylate monomer having less than 4 carbon atoms, the particle size of the obtained soft vinyl polymer exceeds 0.5 μm, and the impact resistance, which is the object of the present invention, cannot be improved.

The soft vinyl polymer obtained by polymerizing mainly an alkyl acrylate monomer having an alkyl group having 4 or more carbon atoms includes, for example, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, dodecyl acrylate, myristyl acrylate, It is a polymer mainly composed of one or more kinds such as cetyl acrylate. It is also possible to copolymerize other monomers copolymerizable with these acrylates, but the proportion used is such that the obtained copolymer is still soft, that is, liquid or rubbery, and the particle size is 0.5. It is preferable that the amount is not more than μm, and specifically, although it depends on the type of the monomer,
It is usually at most 80% by weight based on the total monomers.

These copolymerizable monomers are not particularly limited, and include, for example, acrylates such as methyl methacrylate, ethyl acrylate, and propyl acrylate; alkyl methacrylates having an alkyl group having 1 to 24 carbon atoms; cyclohexyl acrylate, benzyl acrylate, and phenoxyethyl Acrylate, phenoxydiethylene glycol diacrylate, tetrahydrofurfuryl alcohol acrylate, isobornyl acrylate, dicyclopentadienyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl methacrylate, polypropylene glycol diacrylate, trimethylolpropane triacrylate, etc. ) Acrylates; acrylonitrile, acrylic acid, Acrylic compounds having no ester group such as toxicmethylacrylamide and methacrylamide; non-conjugated vinyl compounds such as vinyl acetate, vinyl laurate, vinyl versate, vinyl chloride, vinylidene chloride, ethylene and allyl acetate; butadiene, isoprene, chloroprene And the like, and polymerizable vinyl compounds such as butyl fumarate, monoethyl maleate and diethyl itaconate can be used.

As described above, the modified epoxy resin in the present invention is:
By polymerizing a monomer that forms a soft vinyl polymer in a conventional manner in the presence of a graft polymer of an epoxy resin and a vinyl polymer, a soft vinyl polymer is obtained as a composition in which the soft vinyl polymer is dispersed almost spherically. ,
The particle size of the dispersed particles varies depending on the type of the vinyl polymer and the type of the soft vinyl polymer.
When m exceeds m, the object of the present invention cannot be achieved. In order to improve the impact resistance, which is the object of the present invention, the particle size is preferably 0.5 μm or less. Regarding the particle size control of such a soft vinyl polymer to a desired range, by appropriately selecting the type and amount of the vinyl polymer forming the graft polymer with the epoxy resin, and the monomer composition forming the soft vinyl polymer. Although it can be performed, it can also be controlled by the amount of double bonds introduced into the epoxy resin.

The copper powder used in the present invention may be any of flake-like powder, spherical powder, resin-like powder, and dispersants such as higher fatty acids such as stearic acid, silane coupling agents, titanate coupling agents, aluminum cups. It may be treated with a ring agent or the like. Note that the copper powder may be a composite powder with silver by adding silver powder, but there is an optimum range for the ratio of silver. In other words, when silver powder is used in combination, good results are obtained in conductivity and its retention property, but when the amount exceeds a certain range, disadvantages of silver paste such as increase in price and occurrence of silver migration phenomenon become apparent. This deviates from the original purpose of using the conductive paste. That is, it is necessary to keep the silver ratio within a range that does not significantly affect the cost and does not cause the silver migration phenomenon, and the upper limit is about 20% by weight. These conductive powders may be used alone or in combination.

The solvent used in the paste of the present invention is a good solvent for both the reducing resin and the modified epoxy resin, that is, dissolving both resins together and not causing phase separation of the resin and solvent, during screen printing, It must have a high boiling point that does not significantly change the solid content by volatilization, does not significantly impair the curing rate, and has no odor or toxicity.

As those having all of these conditions, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,
Ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, Ethylene glycol and diethylene glycol derivatives such as diethylene glycol dibutyl ether; butyl acetate, amyl acetate, cyclohexyl acetate, methyl acetoacetate, ethyl acetoacetate, dimethyl adipate, dimethyl glutarate, Esters such as click dimethyl; cyclohexanone, methylcyclohexanone, diisobutyl ketone and isophorone; alpha-terpineol, and the like. These solvents may be used alone or in combination.

Various compounds may be added as long as the properties of the conductive copper paste are not impaired. The compound referred to here is a resin as a binder, a paint additive,
It means an adhesion improver.

Examples of the resin serving as a binder include general epoxy resins, phenol resins, acrylic resins, polyester resins, polyurethane resins, ketone resins, and phenoxy resins. Examples of the paint additive include inorganic substances such as fine particle silica and bentonite used for imparting and optimizing printability, and those obtained by treating these with an organic substance, and silicon-based and fluorine-based ones. Examples of the adhesion improver include a silicon coupling agent, a titanate coupling agent, and an aluminum coupling agent.

 Finally, the amount of each component will be described.

A suitable amount of the modified epoxy resin is 10 to 80 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the reducing resin. If the amount is less than 10 parts by weight, the effect of adding the modified epoxy resin will not be exhibited, and the adhesion, heat and moisture resistance, and solder heat resistance will not be improved. There is a limit to the amount of conductive powder added due to having high viscosity, not only can not express high conductivity,
Difficulties arise in printability and adhesion.

The amount of the conductive powder depends on the type thereof, but is 400 to 90 parts per 100 parts by weight of the total of the reducing resin and the modified epoxy resin.
0 parts by weight, preferably 500-800 parts by weight, are suitable. When the amount is less than 400 parts by weight, high conductivity is not exhibited, and when it exceeds 900 parts by weight, it does not become a paste.

The compounding amount of the solvent for forming the paste of the present invention,
Total amount of conductive powder, reducing resin and modified epoxy resin
It is suitable to add 5 to 25 parts by weight, preferably 12 to 18 parts by weight, per 100 parts by weight. If this amount is less than 5 parts by weight, the paste becomes highly viscous and printing becomes difficult.
If it exceeds 25 parts by weight, the viscosity becomes too low, so that a fine pattern cannot be drawn at the time of screen printing, or the thickness of the transferred pattern is thin and it is necessary to perform printing several times to obtain a predetermined conductivity. Inconvenience occurs.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. These are merely examples, and are not intended to limit the technical scope of the present invention, that is, the present invention is not limited to these examples. Hereinafter, “parts” means parts by weight.

In addition, the obtained conductive paste was evaluated by the following seven types of tests.

(1) Initial electrical resistance: 2 mm of conductive paste on the phenolic surface of the paper-reinforced phenolic copper-clad laminate using a hand-printing press (screen mesh # 225, emulsion thickness 10 μm).
A 5-line pattern having a width of 80 mm and a length was printed, and cured at 150 ° C. for 30 minutes using a hot-air circulating dryer. Thereafter, the temperature was cooled to room temperature, and the electric resistance of each of the five wires was measured using a four-terminal resistance meter (Digital Ohmmeter DR-1000, manufactured by Sanwa Keiki Seisakusho), and the average value was determined.

(2) Adhesion: After printing a rectangular pattern of 50mm x 80mm on the copper foil surface of the paper-reinforced phenolic resin copper-clad laminate in the same manner as in (1), cure it at 150 ° C for 30 minutes with a hot air circulation dryer. Then, make 100 squares of 1 mm x 1 mm with a cutter knife, attach cellophane tape, and peel off vigorously. At this time, the adhesion was evaluated by the number of meshes remaining in the coating film (JIS-K-5
400).

(3) Insulation coating resistance: After printing, curing, and cooling in the same manner as in (1), an insulating coating agent (trade coat TMD-430: trade name, manufactured by Nippon Acheson Co., Ltd.) was applied to both ends of the pattern at 5 mm.
Each of the patterns was printed and cured from above on the cured conductive paste so as to remain, and the electric resistance value of each pattern was measured with a four-terminal resistance meter. The rate of change of the electric resistance value before and after coating with the insulating coating agent was determined and used as a measure of the insulation coating resistance.

(4) Reliability: In the same manner as in (1), after printing, curing, and cooling, and measuring the initial electric resistance value, the following reliability test was performed.

I. Heat resistance: Using a hot air circulating dryer, it was left at a constant temperature of 80 ° C. for 1000 hours. The change rate of the electric resistance value after 1000 hours was determined with respect to the initial electric resistance value, and was used as a measure of heat resistance.

B. Moisture resistance: It was left for 1000 hours in an environment of 40 ° C. and 95% RH using a thermo-hygrostat. The change rate of the electric resistance value after 1000 hours with respect to the initial electric resistance value was determined and used as a measure of the moisture resistance.

(5) Solder heat resistance: After printing, curing, cooling and measuring the initial electric resistance value in the same manner as in (1), 5
Dipped twice for a second. The rate of change of the electrical resistance after immersion was determined with respect to the initial electrical resistance, and used as a measure of the solder heat resistance.

(6) Thermal shock property: After printing, curing, cooling and measuring the initial electric resistance value in the same manner as in (1), leave in a thermostat at 120 ° C. for 1 hour and in a thermostat at −30 ° C. for 1 hour. This operation was repeated 100 times. With respect to the initial electric resistance value, the rate of change of the electric resistance value after 100 operations was determined, and was used as a measure of the thermal shock property.

Example 1 Orthocresol novolak epoxy resin (epoxy equivalent: 217 g / eq) 100 parts, toluene 10 parts and methacrylic acid 1
After reacting for 2 hours at 120 ° -125 ° C. in the presence of trimethylamine, 3.6 parts of butyl acrylate, 0.1 part of glycidyl methacrylate and 0.05 part of t-butylperoxy-2-ethylhexanoate were added. Let react for hours. Further, 30 parts of butyl acrylate, 0.6 part of neopentyl glycol diacrylate, and 1,1-bis- (t
-Butylperoxy) -3,3,5-tricyclohexane 0.1
After reacting for 4 hours while continuously dropping 5 parts, the solvent was removed under reduced pressure, and the modified epoxy resin A (epoxy equivalent 285 g / e
q) got.

On the other hand, 105.6 parts of hydroquinone and 26.4 parts of p-cresol are dissolved in 49.5 parts of diethylene glycol monomethyl ether, and 174.0 parts of 37% by weight formalin is added, followed by heating to 60 ° C. Then, the reaction is carried out at 85 ° C. for 6 hours using 4.5 parts of 28% by weight aqueous ammonia as a catalyst. Further, water generated by the condensation reaction is completely removed under reduced pressure, and the reducing resin solution B (solid content
80% by weight).

Next, 100 parts of the obtained reducing resin solution B (solid content 80
(% By weight), 15 parts of the modified epoxy resin A obtained above was uniformly dissolved, and 700 parts of CE-1110 (trade name, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was added as a copper powder. 100 parts of diethylene glycol monomethyl ether was added as a viscosity adjusting solvent, mixed well, and then kneaded with a three-roll mill to obtain a conductive paste. About the obtained paste,
The results were evaluated in the tests described above, and the results are shown in Table 1.

Example 2 In Example 1, ortho-cresol novolak epoxy resin, which is a raw material of the modified epoxy resin A, was replaced with bisphenol A diglycidyl ether epoxy resin (Epicoat # 1001: trade name, manufactured by Yuka Shell Co.) and butyl acrylate. The procedure was exactly the same except that 2-ethylhexyl acrylate was used instead, to obtain a conductive paste. The obtained paste was evaluated in the above test, and the results are shown in Table 1.

Example 3 In Example 1, p as the raw material of the reducing resin solution B was used.
-Except for replacing cresol with t-butylphenol, the same operation was performed to obtain a conductive paste. The obtained paste was evaluated in the above test, and the results are shown in Table 1.

Example 4 In Example 1, the fine-particle silica Aerosil # 300 was used.
The procedure was exactly the same except that 10 parts (trade name, manufactured by Nippon Aerosil Co., Ltd.) were added to obtain a conductive paste. The obtained paste was evaluated in the above test, and the results are shown in Table 1.

Example 5 In Example 1, copper powder CE-1110 was replaced with copper-silver composite powder Cu-Ag (8%) (trade name, manufactured by Fukuda Metal Foil & Powder Co., Ltd.).
The operation was performed in exactly the same manner as in Example 1, except that the conductive paste was obtained. The obtained paste was evaluated in the above test,
Table 1 shows the results.

Example 6 In Example 1, the aminosilane coupling agent SH was used.
Except for adding 1 part of -6020 (trade name, manufactured by Toray Silicone Co., Ltd.), the same procedure was followed to obtain a conductive paste. The obtained paste was evaluated in the above test, and the results are shown in Table 1.

Comparative Example 1 A conductive paste was obtained in the same manner as in Example 1, except that the reducing resin B was replaced with a phenol resin (Regitop PL-2285: trade name, manufactured by Gunei Chemical Industry Co., Ltd.). The obtained paste was evaluated in the above test,
Table 2 shows the results.

In this case, since the binder has no reducing ability, the initial conductivity is poor, and the reliability is poor.

Comparative Example 2 A conductive paste was obtained in the same manner as in Example 1, except that the modified epoxy resin A was replaced with a urethane-modified epoxy resin (ADEKARESIN EP-4000: trade name, manufactured by Asahi Denka Kogyo KK). The obtained paste was evaluated in the above test, and the results are shown in Table 2.

It is clear that even a modified epoxy resin containing no vinyl polymer gives extremely poor results for all test items.

Comparative Example 3 A conductive paste was obtained in the same manner as in Example 1, except that butyl acrylate as a raw material of the modified epoxy resin A was replaced with ethyl acrylate. The obtained paste was evaluated in the above test, and the results are shown in Table 2.

In this case, the particle size of the vinyl polymer exceeds 0.5 μm, and the particle size is 0.5 μm or less.
It can be seen that the effect of addition is much inferior to the case of (1).

[Effects of the Invention] As is clear from Tables 1 and 2, the conductive copper paste of the present invention is excellent in reliability such as conductivity, printability, adhesion, heat resistance and moisture resistance, and It is inexpensive and suitable for forming various conductive circuits including a jumper substrate.

Claims (5)

(57) [Claims] 1. A modified epoxy resin comprising a conductive powder mainly composed of copper powder, a reducing resin and an epoxy resin as main components, and a modified epoxy resin having a carbon number of 4 in a graft polymer of an epoxy resin and a vinyl polymer. A conductive copper paste characterized in that the vinyl polymer mainly composed of an alkyl acrylate having an alkyl group is uniformly dispersed with a particle diameter of 0.5 μm or less. 2. The conductive copper paste according to claim 1, wherein the reducing resin is a modified hydroquinone resin. 3. The conductive copper paste according to claim 1, wherein the conductive powder is copper powder or a composite powder of copper and silver. 4. The method according to claim 1, wherein the ratio of the reducing resin to the modified epoxy resin is
The conductive copper paste according to any one of claims 1 to 3, wherein a reducing resin: a modified epoxy resin = 100: 80 to 100: 10. 5. The ratio of the conductive powder to the total of the reducing resin and the modified epoxy resin is as follows: conductive powder: (reducing resin + modified epoxy resin) = 400: 100 to 900: 100. ~
5. The conductive copper paste according to any one of 4.