JP2967117B2 - Electron beam-curable conductive paste composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electron beam-curable conductive paste composition used in the fields of electricity and electronics, and more particularly, to electronic device parts and printed wiring boards. The present invention relates to an electron beam-curable conductive paste composition having a function such as a conductive circuit applied to a conductive circuit, a conductive connection such as terminal connection, and an adhesive.

In addition, the electron beam-curable conductive paste composition of the present invention is designed to be applied to a method of heating before, during or after irradiation with an electron beam, and curing by using both electron beam curing and heat curing. It is.

(Prior Art) In recent years, so-called paste-like conductive paints and conductive adhesives (hereinafter, referred to as “each paste”) in which a large amount of fine silver flakes, copper powder, or carbon particles are blended with an organic polymer binder or oligomer. Are referred to as a conductive paste) and are widely used.

These conductive pastes are used for forming a conductive circuit in a manufacturing process of a printed wiring board or a hybrid IC. It is also used as a resistor in circuit formation. Furthermore, this kind of paste can be used for adhesives for various electronic components such as membrane switches and resistors, adhesives for liquid phase panels,
Also used as D adhesive.

Further, as one of the measures to prevent electromagnetic interference which has recently attracted attention as a social problem, a conductive paste is applied to a printed wiring circuit. This is because the conductive paste shields electromagnetic waves generated from inside the circuit and prevents crosstalk between wirings, and is becoming increasingly popular.

There are severe demands on the reliability of these conductive pastes. For example, conductive pastes having high heat resistance, adhesives, and moisture resistance have been desired.

Conventionally developed conductive pastes use thermosetting resins as binders, and although technical improvements such as heat resistance and adhesiveness are expected, they require a great deal of energy and heating to cure. time of,
It is uneconomical because it requires a large floor area for installing the heating device. In addition, the base material to which the conductive paste is applied is often a synthetic resin, and long-time heating causes deterioration or deformation of the base material, which may impair long-term reliability. . Therefore, there is a strong demand for a material that can be cured by heating for a short time, but it has not been satisfactory yet.

Therefore, a technique for curing a conductive paste by irradiation with an active energy ray such as an ultraviolet ray or an electron beam at room temperature, a temperature close to the room temperature, or a short time that does not cause deterioration of the base material is expected.

However, curing by ultraviolet light is difficult to apply a high-concentration conductive powder-containing coating film for expressing conductivity because ultraviolet light has no ability to transmit a filler.
Since a large amount of a photoinitiator or a sensitizer is used, the coating film may be deteriorated. On the other hand, curing by an electron beam has no problems such as restriction of fillers and deterioration of a coating film due to an initiator as in ultraviolet curing.

However, there is a drawback that the initial conductivity or the conductivity under an environment of high temperature and high humidity is remarkably inferior to that of the thermosetting type. Further, the thickness of the coating material is limited in terms of the electron beam transmission ability, and the shape of the coating material is also limited.

To cope with these drawbacks, for example, JP-A-56-90590 discloses that a coating film coated with a silver filler-containing electron beam-curable coating is heated after irradiation with an electron beam. There are significant improvements in initial conductivity by this method.

JP-A-62-200703 discloses a method of forming a resistance circuit 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
An attempt was made to improve the performance of the electron beam cured product by additionally introducing a heating step.

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

(Problems to be Solved by the Invention) The present invention has excellent initial conductivity, retains long-term reliability even in an environment of high temperature and high humidity, and uses a combination of electronic heat and heat without migration problem. An electron beam-curable conductive paste composition is provided.

(Means for Solving the Problems) As a result of various studies on the above problems, the present inventor has found that by using an electron beam-curable resin and a specific thermosetting resin together, the initial conductivity is excellent, and The present inventors have found that it is possible to provide an electron beam-curable conductive paste composition which can maintain the reliability of electric characteristics even in a high-temperature and high-humidity environment and has no migration problem, and completed the present invention.

That is, the present invention provides: (A) (a) 10 to 90% by weight of an electron beam-curable resin;
(B) Paste resin 5 comprising 90 to 10% by weight of one or more resins selected from amino resins, phenol resins, epoxy resins having no unsaturated groups, and polyisocyanate resins.
An electron beam-curable conductive paste composition comprising, as essential components, 8585 parts by weight and (B) 95-15 parts by weight of conductive powder.

The coating film obtained from the paste composition of the present invention has both an electronic thermosetting resin and an amino resin, a phenol resin, an epoxy resin having no unsaturated group, and one or more resins selected from polyisocyanate resins. , Or combined to contribute to curing, the strength of the coating film is significantly improved compared to the electron beam curable resin alone system,
Performance such as heat resistance and moisture resistance is greatly improved.

Examples of the electron beam-curable resin used in the present invention include a resin having an unsaturated group in a molecular chain or in a side chain. Specifically, unsaturated polyester resin,
Examples include 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.

Further, monomers or oligomers having an unsaturated group 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, dimethyl (aminomethyl) (meth) acrylate, polymethylene glycol polyacrylate, polypropylene Glycol polyacrylate, trimethylolpropane triacrylate, triallyl trimellitate, triallyl isocyanurate and the like may be used in combination.

Examples of the amino resin, phenol resin, epoxy resin having no unsaturated group, and polyisocyanate resin used in the present invention include the following resins.

As the amino resin, urea, melamine, benzoguanamine, dicyandiamide and the like, a resin obtained by addition condensation of a compound having an amino group and formaldehyde,
Resins borrowed with ether by reacting alcohols such as methanol, ethanol, isopropyl alcohol, and butanol with this are exemplified.

If necessary, a commonly used catalyst may be added to this amino resin. Examples of the catalyst include p-toluenesulfonic acid, p-toluenesulfonic acid amino salt and the like.

Examples of the phenol resin include phenol, cresols, other alkyl phenols or phenols such as bisphenols, resol type resins obtained by addition condensation with aldehydes such as formaldehyde and acetaldehyde, and methanol, ethanol, isopropyl Examples include resins which are etherified by reacting alcohols such as alcohol and butanol. In some cases, a novolak resin can also be used.

Examples of the epoxy resin having no unsaturated group include those having two or more epoxy groups in one molecule. Examples thereof include glycidyl ethers, glycidyl esters, glycidylamines, linear aliphatic epoxides, and alicyclic rings. Formula epoxides and the like can be mentioned. If necessary, a curing agent or a catalyst may be added to this epoxy resin.

The polyisocyanate resin has two or more isocyanate groups in one molecule, for example, aliphatic polyisocyanate, alicyclic polyisocyanate,
Examples thereof include aromatic polyisocyanates and polymers obtained by reacting them with adduct agents such as alcohols, acids, and water. If necessary, a curing agent or a catalyst may be added to the polyisocyanate resin.

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

In the present invention, (a) an electron beam-curable resin;
(B) The mixing ratio of one or more resins selected from an amino resin, a phenol resin, an epoxy resin having no unsaturated group, and a polyisocyanate resin is such that (a) is 10 to 90.
% By weight and (b) 90 to 10% by weight. If (a) is less than 10% by weight, the time required for the curing reaction is long, and the curing temperature is high, so that the object to be coated cannot be warped or twisted. On the other hand, if the content exceeds 90% by weight, a highly reliable coating film cannot be obtained in an environment 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 electron beam-curable conductive paste composition of the present invention include metal powders such as gold, silver, copper, nickel, chromium, palladium, aluminum, tungsten, molybdenum, and platinum; Inorganic powder or organic powder, metal oxide powder such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, powder coated with these metal oxides, or carbon black, graphite, etc. Can be These conductive powders are used alone or in combination of two or more. Examples of the shape include a granular shape, a spherical shape, a flake shape, a flake shape, a plate shape, a tree shape, a dice shape, and the like, and those having an average particle size of 0.1 μm to 100 μm can be used. The conductive powder is preferably copper or nickel, and more preferably one or more copper powders selected from dendritic copper powder, scaly copper powder, and spherical copper powder, and has an average particle size of 1 to 50 μm. . The average particle diameter refers to, for example, a volume average particle diameter measured by a laser diffraction method.

In the present invention, a paste resin comprising (A) (a) an electron beam-curable resin and (b) one or more resins selected from an amino resin, a phenol resin, an epoxy resin having no unsaturated group, and a polyisocyanate resin. And (B)
(A) is 5 to 85 parts by weight,
(B) is 95 to 15 parts by weight.

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

An organic fatty acid can be added to the electron beam-curable conductive paste composition of the present invention in order to improve conductivity. Here, the organic fatty acid is an aliphatic compound having one or more carboxyl groups in one molecule.

For example, saturated carboxylic acids, unsaturated carboxylic acids, alicyclic carboxylic acids and the like can be mentioned. 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, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like; unsaturated carboxylic acids are acrylic acid, methacrylic acid, crotonic acid, oleic acid, linoleic acid Acids, linolenic acid, fumaric acid, maleic acid and the like; alicyclic carboxylic acids include cyclohexane carboxylic acid, hexahydrophthalic acid, tetrahydrophthalic acid and the like. These can be used alone or in combination. In addition, these derivatives can also be used. Preferred are oleic acid, linoleic acid and linolenic acid.

The amount of the organic fatty acid to be 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 electron beam-curable conductive paste composition of the present invention in order to improve conductivity. Here, the phenolic compound refers to a compound having a phenolic hydroxyl group.

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

The amount of the phenolic compound to be 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 electron beam-curable conductive paste composition of the present invention in order to improve coating film performance. Here, the 1,3-dicarbonyl compound refers to a compound in which two carbonyl groups in a molecule are located at positions 1,3.

As specific examples, acetylacetone, propionylacetone, butyrylacetone, valerylacetone, octanoylacetone, lauroylacetone, acryloylacetone, methacryloylacetone, linoleylacetone, linoleylacetone, 2,4-hexynesandione, 3, Five
-Heptanedione, 3,5-octanedione and the like. These can be used alone or in combination,
These derivatives can also be used. Preferably, it is acetylacetone.

The amount of the 1,3-dicarbonyl compound is 0.05 to 10% by weight based on 100% by weight of the conductive paste composition of the present invention.
It is. Preferably, it is 0.1 to 5% by weight.

Organic fatty acids, phenolic compounds, and 1,3-dicarbonyl compounds may be used alone or as a mixture. In addition to the addition to the conductive paste of the present invention, the conductive paste may be mixed in advance with only the conductive powder, and then the conductive paste may be prepared. If necessary, the above three kinds of compounds are dissolved in a solvent, and a conductive powder is put into the solvent to perform a surface treatment. Then, the solvent is filtered or directly removed to take out the conductive powder. The conductive paste may be used to produce the conductive paste.

In order to adjust the workability of the electron beam-curable conductive paste composition of the present invention, a volatile solvent can be added.

As the volatile solvent, for example, ketones, aromatics, alcohols, cellosolves, esters and the like can be used. Specifically, methyl ethyl ketone, methyl isobutyl ketone, 3-pentanone, 2-heptanone, 3-heptanone, benzene, toluene, xylene, ethanol, propanol, butanol, hexanol, octanol, ethylene glycol, propylene glycol, methyl cellosolve, ethyl cellosolve , Butyl cellosolve,
Propylene glycol monoethyl ether, propylene glycol monobutyl ether, butyl carbitol,
Ethyl acetate, butyl acetate, cellosolve acetate, butyl carbitol acetate and the like, or a mixture thereof.

The electron beam-curable conductive paste composition of the present invention may further contain, if necessary, a filler and an additive. For example, as the filler, silica, kaolin, titanium oxide, barite, talc, mica, clay, and the like, and as an additive, a flow regulator, an antifoaming agent, a dispersant, a dye, a pigment, a coupling agent, and the like. No.

As a method for preparing the electron beam-curable conductive paste composition of the present invention, a method for preparing a coating material can be generally applied. For example, mixing with a three-roll mill, mixing with a kneader, mixing with a ball mill, and the like can be mentioned. Especially,
The mixing order of (A) and (B) is not limited.

Various methods are used for applying the electron beam-curable conductive paste composition of the present invention to a substrate, depending on the purpose. For example, screen printing, offset printing, gravure printing, letterpress printing or spray coating, roller coating,
Coating methods such as brush coating, casting, and spin coating are exemplified.

The substrate to be applied is not particularly limited, and can be widely applied to substrates such as paper / phenolic substrates, glass / epoxy substrates, plastic molded products, and metal processed products.

As a method for curing the electron beam-curable conductive paste composition of the present invention, it is preferable to use both electron beam curing and heat curing after printing and coating on a substrate. However, curing using only an electron beam or curing using only heat can be applied.

Electron beam curing is achieved by irradiating the coating with an electron beam in air or in an inert gas atmosphere. When the conductive paste composition contains a volatile solvent, the solvent may be removed at room temperature or by heating. During solvent removal,
When heated, it can also serve as pre-irradiation heating described below. As the electron beam irradiation method, any method such as a non-scanning method such as a curtain type, a laminar type, a broad beam type, an area beam type, and a pulse type, and a low energy and medium energy scanning method can be used. Irradiation conditions are not particularly limited, a current of 1 to 100 mA,
An acceleration voltage of 150 to 1,000 kV and an irradiation dose of 1 to 30 Mrad are desirable.

Curing by heat is one that causes a reaction by heating to a temperature of room temperature or higher, usually at 50 to 250 ° C. for several seconds to
A heating condition of several hours is chosen. Examples of the heating method include a method using a medium such as heated air or hot water, a method using irradiation of infrared rays or far infrared rays, and the like, and are not particularly limited.

In addition, a curing method using both electron beam irradiation and thermal curing is achieved by heating before, during, and after electron beam irradiation. By using this method, a sufficient effect can be obtained by heating at a remarkably low temperature for a short time as compared with a paste composition using only a thermosetting resin as a binder.

The electron beam-curable conductive paste composition of the present invention can be practically used as it is after curing, but may be subjected to a heat aging treatment if necessary, or may be coated with a protective coating or the like. It is possible.

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

Examples of its use include screw lock or caulking reinforcement, circuit repair, volume resistor and electrode paint, capacitor electrode paint, waveguide bonding, liquid crystal bonding, LED bonding, and semiconductor element bonding. , A potentiometer, a quartz oscillator, and a micromotor carbon brush.

(Examples) The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

(A) A method for preparing a conductive paste.

The components shown in the following table were uniformly dispersed and prepared using three rolls.

(B) A method for forming a cured coating film.

The conductive paste is 1 cm long and 1 cm wide on a single-sided copper-clad paper phenolic laminate with a copper foil electrode part formed by etching and polishing in advance using a 200 mesh stainless steel screen plate. Printed on. Next, heating and electron heat irradiation were performed under predetermined conditions to cure the conductive paste.

Heating is performed by a far-infrared ray device, and electron heat irradiation is performed by Ushio Electric Co., Ltd., using an electron beam under the conditions of a Unitron 200/200 [acceleration voltage of 200 kV and an absorbed dose of 10 Mrad in an N ₂ gas atmosphere.
The irradiation time at this time is about 20 seconds. ], A thermosetting solder register (manufactured by Taiyo Ink Mfg. Co., Ltd., S-22) is printed on the cured conductive paste, and the temperature is 150 ° C. × 15 m
In cured.

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

(Ii) Solder immersion test The cured coating was placed in a 260 ° C molten solder bath (tin 60 / lead 40).
Immerse for 2 seconds.

(Iii) Moisture resistance test The cured coating film was placed in a thermo-hygrostat at 60 ° C and 90-95% relative humidity.
Leave for 0 hours.

The rate of change of the specific volume resistance after the tests (ii) and (iii) was calculated by the following equation.

Examples 1 to 7 Table 1 shows the formulations, 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 to 19 Table 3 shows the formulations, heating conditions, and evaluation results of Examples 14 to 19.

Examples 20 and 21 Using the paste formulation of Example 1, cured coating films were obtained under the heating conditions shown in Table 4.

Comparative Examples 1-4 Table 5 shows the formulations, heating conditions, and results of Comparative Examples 1-4.

(Effects of the Invention) The electron beam-curable conductive paste composition of the present invention is a combination-curable type of electron beam and heat having no migration problem, and a conductive coating film obtained by the composition. Has excellent long-term reliability.After a moisture resistance test, even in a severe test of withstanding thermal shock resistance, it does not cause coating defects such as peeling of the coating film and can maintain the initial performance. it can.

Further, it is possible to minimize damage to the object to be coated.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-133079 (JP, A) JP-A-63-248883 (JP, A) JP-A-61-14275 (JP, A) JP-A-58-1983 160372 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 11/00-11/20

Claims (1)

(57) [Claims] (A) (a) 10 to 90% by weight of an electron beam-curable resin, and (b) at least one kind selected from an amino resin, a phenol resin, an epoxy resin having no unsaturated group, and a polyisocyanate resin. Paste resin 5 consisting of 90 to 10% by weight of resin
An electron beam-curable conductive paste composition comprising, as essential components, up to 58 parts by weight and (B) 95 to 15 parts by weight of a conductive powder.