JP5683202B2 - Thermosetting conductive paste - Google Patents

Description

  The present invention relates to a conductive paste, and relates to a thermosetting conductive paste that can be suitably used for electrodes and circuit patterns of electronic components, external electrodes of solar cells, and the like.

  In order to form electrodes and circuit patterns of electronic parts, external electrodes of solar cells, and the like, a conductive paste containing a conductive filler such as silver fine particles is used.

  In recent years, it has been desired to form dense and precise electrodes and circuit patterns in response to demands for downsizing and high lamination of electronic components. Recently, in a combination of a substrate and a conductive paste, a type of conductive paste that is cured at a relatively low temperature of 100 to 300 ° C. is more suitable than a type of conductive paste that is baked at a high temperature of 500 ° C. or higher. is there. In addition, in the combination of the substrate and the conductive paste, when the surface state of the substrate changes, the resin component contained in the conductive paste printed for the circuit pattern or electrode exudes to the substrate, and the conductive component together with this resin. However, there is a case in which a so-called bleed-out phenomenon that oozes out on the substrate occurs, and a dense and precise electrode or circuit pattern cannot be formed.

  For example, (a) an acrylic ester or methacrylic ester compound which is a thermosetting resin, (b) a radical initiator, (c) an organic titanium compound containing a phosphorus atom in the molecule, and (d) a filler, c) A resin paste composition for a die bonding material that improves the affinity between a resin and a filler and suppresses bleed-out by an organic titanium compound containing a phosphorus atom in the molecule has been proposed (Patent Document 1).

JP 2008-283199 A

  As described in Patent Document 1 above, the resin paste for die bonding material has been improved to suppress bleed out. However, in addition to the use of the die bonding material, there is a demand for an improvement that suppresses bleed out in thermosetting conductive pastes used for electrodes and circuit patterns of electronic components, external electrodes of solar cells, and the like.

  The present invention is a thermosetting conductive paste that can be cured at a relatively low temperature of about 100 to 300 ° C., is excellent in thixotropic properties, has good coating suitability, and is formed by a thermosetting conductive paste. It is an object of the present invention to provide a thermosetting conductive paste that can suppress bleed-out while maintaining a low specific resistance value of an electrode or the like.

  As a result of repeated studies to solve the above problems, the present inventors have excellent thixotropy by including a specific amount of cellulose resin in a thermosetting conductive paste that can be cured at a relatively low temperature, It has good applicability, can suppress so-called bleed out that the conductive filler oozes out with the resin in the conductive paste, and can form electrodes and circuit patterns that maintain a low specific resistance value I found out that

That is, the present invention is a thermosetting conductive paste containing (A) a conductive filler, (B) a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer in some cases. And (B) a thermosetting resin and a curing agent resin in a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer included in the thermosetting conductive paste. The total amount of the polymer is 1 to 10% by mass, (B) a thermosetting resin and a curing agent in the thermosetting binder, (C) a cellulose resin, and (D) acrylonitrile butadiene optionally included The content of (C) cellulose resin in the total amount with a copolymer is 2-60 mass%, It is related with the thermosetting conductive paste characterized by the above-mentioned.
The present invention relates to (C) the thermosetting conductive paste, wherein the cellulose resin is ethyl cellulose.
The present invention relates to (B) the thermosetting conductive paste, wherein the thermosetting binder contains an epoxy resin, and the epoxy resin further contains 50% by mass or more of a trifunctional or higher functional epoxy resin.
The present invention relates to the thermosetting conductive paste, wherein (A) the conductive filler may be made of silver or an alloy containing silver, and (F) may further contain a solvent.

  The present invention is a thermosetting capable of suppressing bleed-out while maintaining a low specific resistance value such as an electrode formed of a thermosetting conductive paste that can be cured at a relatively low temperature of about 100 to 300 ° C. Type conductive paste can be provided.

It is a figure explaining the schematic structure of the end surface of the chip inductor used for a coating aptitude test. It is a 20 times CCD photograph which shows the state which screen-printed the thermosetting conductive paste (Example 7) of this invention so that line | wire width might be set to 100 micrometers. It is a 20 times CCD photograph which shows the state which screen-printed the thermosetting conductive paste (Example 8) of this invention so that line | wire width might be 100 micrometers. It is a 20 times as many CCD photograph which shows the state which screen-printed the thermosetting conductive paste (Example 9) of this invention so that line | wire width might be set to 100 micrometers. It is a 20 times CCD photograph which shows the state which screen-printed the thermosetting conductive paste (Example 10) of this invention so that line | wire width might be set to 100 micrometers. It is a 20 times CCD photograph which shows the state which screen-printed the thermosetting conductive paste (Example 14) of this invention so that line | wire width might be set to 100 micrometers.

  The present invention is a thermosetting conductive paste comprising (A) a conductive filler, (B) a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer in some cases. (B) a thermosetting resin and a curing agent resin in a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer optionally contained in the thermosetting conductive paste And (C) the content of the cellulose resin in the total amount is 2 to 60% by mass.

  The (A) conductive filler contained in the thermosetting conductive paste provides conductivity after curing. The component (A) is not particularly limited, and metal fine powder such as silver (Ag), gold (Au), copper (Cu), nickel (Ni), palladium (Pd), tin (Sn), and alloys thereof, Examples thereof include inorganic fillers coated with gold, silver, and palladium, and silver or an alloy containing silver is preferable. These shapes are not particularly limited, and examples thereof include a spherical shape and a flake shape. Preferably, a flake shape can be used, and an average particle diameter of 5 to 15 μm is preferable. As the component (A), a single component may be used, or two or more types may be used in combination. In addition, the average particle diameter in this specification means the volume-based median diameter measured by the laser diffraction method irrespective of the shape of the metal fine powder.

  The content of the conductive filler (A) in the thermosetting conductive paste is preferably 90 to 99% by mass, more preferably 93 to 99% by mass, and still more preferably 96 to 98% by mass. When the content of the conductive filler (A) in the thermosetting conductive paste is within the above range, an electrode formed by a thermosetting conductive paste that can be cured at a relatively low temperature of 100 to 300 ° C. A low specific resistance value can be maintained.

  The (B) thermosetting binder contained in the thermosetting conductive paste contains a thermosetting resin and a curing agent if necessary, and can be cured at a low temperature of 100 to 300 ° C. It is preferable.

  (B) Examples of the thermosetting resin in the thermosetting binder include epoxy resins such as bisphenol A type, bisphenol F type, phenol novolac type, and alicyclic type; oxetane resins; phenol resins such as resol type and novolac type Etc. These resins may be used alone or in combination of two or more. Of these, epoxy resins and phenol resins are preferred.

  (B) The epoxy resin contained in the thermosetting binder includes bisphenol A type, bisphenol F type, phenol novolac type, tetrakis (hydroxyphenyl) ethane type or tris (hydroxyphenyl) which is a polyfunctional type having many benzene rings. ) Epoxy resins such as methane type, biphenyl type, triphenolmethane type, naphthalene type, orthonovolak type, dicyclopentadiene type, aminophenol type, and alicyclic type, and silicone epoxy resin. These resins may be used alone or in combination of two or more. Among them, bisphenol A type epoxy resin such as bisphenol A type diglycidyl ether, branched polyfunctional bisphenol A type epoxy resin such as p-glycidoxyphenyldimethyltolyl bisphenol A diglycidyl ether, α-2,3-epoxy Propoxyphenyl-ω-hydropoly (n = 1-7) [2- (2,3-epoxypropoxy) benzylidene-2,3-epoxypropoxyphenylene], a triphenolmethane type epoxy resin, tris (hydroxyphenyl) methane Type epoxy resins and modified epoxy resins are preferred.

  The epoxy resin preferably contains a trifunctional or higher functional epoxy resin because the resistance can be relatively reduced by volume shrinkage. (B) The trifunctional or higher functional among 100 mass% of the epoxy resin contained in the thermosetting binder. The epoxy resin content is preferably 50% by mass or more. Here, the trifunctional or higher functional epoxy resin refers to an epoxy resin having three or more epoxy groups. (B) Content of the epoxy resin more than trifunctional in an epoxy resin becomes like this. More preferably, it is 55 mass% or more, More preferably, it is 60-100 mass% or more. (B) When the content of the trifunctional or higher functional epoxy resin is 50% by mass or more with respect to 100% by mass of the epoxy resin contained in the thermosetting binder, the resistance can be relatively reduced by volume shrinkage. Examples of the tri- or higher functional epoxy resin include tris (hydroxyphenyl) methane type solid epoxy resin (epoxy equivalent 169 to 179 g / eq), p-aminophenol type liquid epoxy resin (epoxy equivalent 90 to 150 g / eq), 1,1 , 2,2-Tetrakis (hydroxyphenyl) ethane type epoxy resin (epoxy equivalent 169 g / eq), α-2,3-epoxypropoxyphenyl-ω-hydropoly (n = 1-7) [2- (2,3- Epoxypropoxy) benzylidene-2,3-epoxypropoxyphenylene], orthocresol novolac type epoxy resin (for example, “Epiclon N-665-EXP” manufactured by DIC, epoxy equivalent of 198 to 208 g / eq), and the like.

  As a curing mechanism of the epoxy resin, it is preferable to make the phenol resin function as a curing agent for the epoxy resin, and a curing accelerator such as amines or imidazoles may be used.

  The phenol resin may be an initial phenol resin condensate that is usually used as a curing agent for epoxy resins, and may be a resol type or a novolac type, but 50% by mass or more thereof is an alkyl resol type, an alkyl novolak type, an aralkyl novolak type. Phenol resin, xylene resin or allylphenol resin is preferred. In the case of an alkylresole type phenol resin, the average molecular weight is preferably 2,000 or more in order to obtain excellent coating suitability. In these alkylresole type or alkyl novolac type phenol resins, alkyl groups having 1 to 18 carbon atoms can be used, and carbons such as ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl and decyl can be used. The thing of several 2-10 is preferable.

  (B) The number of moles of the phenolic hydroxyl group of the phenol resin in the thermosetting binder / number of moles of the epoxy group of the epoxy resin is preferably 0.7 to 1.3, more preferably 0.8 to 1.2. More preferably, it is 0.9-1.1. (B) It is preferable if the number of moles of phenolic hydroxyl groups / number of moles of epoxy groups in the thermosetting binder is within the above range, since unreacted materials can be reduced.

  Although it does not specifically limit as a hardening accelerator, Although a well-known thing can be used, It is preferable to use an amine type hardening accelerator and / or a modified imidazole type hardening accelerator. A hardening accelerator may be used individually by 1 type, and may use 2 or more types together.

  Examples of the amine curing accelerator include 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2. Imidazole compounds such as undecylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, tris (dimethylaminomethyl) phenol, benzyldimethylamine, 1,8 -Tertiary amines such as diazabicyclo (5,4,0) undensen-7. Specifically, 2-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, benzyldimethylamine and the like are preferable.

  An epoxy-imidazole adduct compound or an acrylate-imidazole adduct compound can be used as the modified imidazole accelerator. As commercially available epoxy-imidazole adduct compounds, for example, Ajinomoto Fine Techno Co., Ltd., “Amicure PN-23”, the company “Amicure PN-40”, Asahi Kasei Co., Ltd., “Novacure HX-3721”, or “Fujicure FX-1000” manufactured by Fuji Kasei Kogyo Co., Ltd. Moreover, what is marketed as an acrylate-imidazole adduct type compound includes, for example, “EH2021” manufactured by ADEKA.

  (B) For thermosetting binders, the thermosetting conductivity depends on the type and amount of the thermosetting resin and curing agent, and also considers the printability and applicability to elements and substrates, filling in details, etc. A solvent may be included for viscosity adjustment so that the adhesive paste has an appropriate viscosity. Examples of the solvent include alcohols (eg terpineol, α-terpineol, β-terpineol etc.), ethers (eg ethyl carbitol, butyl carbitol etc.), esters (eg hydroxy group-containing esters, 2,2,4- Trimethyl-1,3-pentanediol monoisobutyrate, butyl carbitol acetate, etc.). For example, when applied to screen printing, a solvent is added using a Brookfield B-type viscometer (10 rpm) so that the viscosity of the thermosetting conductive paste at 20 ° C. is 200 to 300 Pa · s. In the case of dip coating, it is preferable to add a solvent so that the thermosetting conductive paste at 20 ° C. has a viscosity of 25 to 40 Pa · s.

The thermosetting conductive paste of the present invention may further contain (D) an acrylonitrile-butadiene copolymer in some cases. By containing an acrylonitrile-butadiene copolymer, the stress of the cured film can be relaxed and the adhesiveness can be improved. The acrylonitrile-butadiene copolymer has a general formula R [(CH ₂ CH═CHCH ₂ ) _X {CH ₂ CH (CN)} _Y ] _Z R (wherein R represents a carboxyl group) having carboxyl groups at both ends. And x is 1 to 8, y is 1 to 5, and z is 1 to 15. The terminal carboxyl group acrylonitrile-butadiene copolymer is preferable, and is also preferable from the viewpoint of compatibility of the elastomer. . The terminal carboxyl group acrylonitrile / butadiene copolymer has a number average molecular weight of 3,000 to 5,000 and an acrylonitrile content of 0 to 30% by mass relative to the total amount of the acrylonitrile / butadiene copolymer. This is preferable from the viewpoint of viscosity and stress relaxation characteristics of the curable conductive paste. The number average molecular weight is a value using a standard polystyrene calibration curve by gel permeation chromatography (GPC).

  The content of acrylonitrile-butadiene copolymer in the thermosetting conductive paste is preferably 0 to 0.8% by mass, more preferably 0.1 to 0.7% by mass, and particularly preferably 0.3 to 0%. .6% by mass. When the content of the acrylonitrile / butadiene copolymer in the thermosetting conductive paste is within the above range, the stress of the cured film can be relaxed and the adhesiveness of the thermosetting conductive paste can be improved.

  The thermosetting conductive paste contains (C) a cellulose resin. (C) Examples of the cellulose resin include methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose hydroxypropyl cellulose, hydroxybutyl cellulose, and acetyl cellulose. Of these, ethyl cellulose is preferable. The ethyl cellulose may be ethyl cellulose having a viscosity of 5 to 20 mPa · s (low viscosity ethyl cellulose), or may be ethyl cellulose having a viscosity of 100 to 300 mPa · s (high viscosity ethyl cellulose). In addition, the viscosity of ethyl cellulose is the value which measured the solution which melt | dissolved ethyl cellulose in the liquid mixture whose ratio of toluene: ethanol is 80:20 so that it may become 5 mass% based on ASTMD914.

  Total amount of (B) thermosetting resin and curing agent in thermosetting binder, (C) cellulose resin, and (D) acrylonitrile-butadiene copolymer optionally contained in thermosetting conductive paste Is 1 to 10% by mass.

  Total amount of (B) thermosetting resin and curing agent in thermosetting binder, (C) cellulose resin, and (D) acrylonitrile-butadiene copolymer optionally contained in thermosetting conductive paste Is more preferably 1 to 8% by mass, further preferably 1 to 7% by mass, and particularly preferably 1 to 5% by mass. When the total amount is less than 1% by mass, the strength of the cured film is reduced, and when it exceeds 10% by mass, it is difficult to maintain a low resistance value of an electrode or the like formed from a thermosetting conductive paste. Become.

  The content of (C) the cellulose resin is as follows: (B) the thermosetting resin and the curing agent in the thermosetting binder, (C) the cellulose resin, and (D) the acrylonitrile-butadiene copolymer optionally contained. It is 2-60 mass% with respect to 100 mass% of total amounts, More preferably, it is 5-60 mass%, More preferably, it is 10-55 mass%. (C) When the content of the cellulose resin is less than 2% by mass with respect to the total amount of 100% by mass, the coating suitability is lowered, and when it exceeds 60% by mass, the thermosetting conductive paste is formed. It becomes difficult to maintain a low specific resistance value of an electrode or the like.

  In order to make the coating suitability better, (B) a thermosetting resin and a curing agent in a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer optionally contained The content of (C) the cellulose resin is preferably 2 to 60% by mass, and more preferably 5 to 50% by mass with respect to the total amount of 100% by mass. (C) It is excellent in thixotropic property and application | coating suitability as content of a cellulose resin is in the said range. Here, the thixotropic property indicates that good dispersibility of the conductive filler (A) in the thermosetting conductive paste is maintained and that it has an appropriate thixotropic property, and the thixotropic index value is preferably as small as possible.

  In order to further suppress bleed out, (B) a thermosetting resin and a curing agent in a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer optionally contained The content of the (C) cellulose resin is preferably 15 to 60% by mass, more preferably 20 to 50% by mass, and further preferably 30 to 45% by mass with respect to the total amount of 100% by mass. (C) If the content of the cellulose resin is within the above range, bleed out while maintaining good coating suitability and maintaining a low specific resistance value such as an electrode formed of a thermosetting conductive paste. Can be suppressed.

  The thermosetting conductive paste of the present invention may further contain a coupling agent, an additive and the like as (E) other components.

  By incorporating a coupling agent into the thermosetting conductive paste, the dispersibility of the conductive filler can be improved. A silane coupling agent can be used as the coupling agent. The silane coupling agent is not particularly limited, and vinyl group-containing silanes such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycid Epoxy group-containing silanes such as xylpropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, styryl group-containing silanes such as p-styryltrimethoxysilane, 3-methacryloxy Alkoxy group-containing silanes such as propylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3- (meth) acryloxypropi (Meth) acryloyl group-containing silane such as trimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2 -(Aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, An amino group-containing silane such as N-phenyl-3-aminopropyltrimethoxysilane can be used. Among them, those not containing an aromatic ring are preferable, and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycol. Glycidyl group-containing silanes such as sidoxypropyltriethoxysilane can be preferably used. In addition, (d) silane coupling agents may be used alone or in combination of two or more.

  From the viewpoint of dispersibility of the conductive filler, the content of the coupling agent in the thermosetting conductive paste is preferably 0.05 to 0.5 mass%, more preferably 0.1 to 0.1%, based on the conductive filler amount. 0.3% by mass.

  If necessary, the thermosetting conductive paste of the present invention may further contain a plasticizer, an antifoaming agent, a dispersant, a leveling agent, a stabilizer, an adhesion promoter, and the like as additives.

  The thermosetting conductive paste of the present invention can be prepared by uniformly mixing the compounding components by mixing means such as a raking machine, a propeller stirrer, a kneader, a roll, a pot mill and the like. Preparation temperature is not specifically limited, For example, it can prepare at 10-40 degreeC.

  The thermosetting conductive paste of the present invention can be printed or applied to a substrate by any method such as screen printing, gravure printing, dispensing, dipping and the like. When a solvent is used for the thermosetting conductive paste, it is preferable to volatilize the solvent after printing or coating at room temperature or by heating. Further, depending on the type of resin, curing agent and curing catalyst contained in the thermosetting conductive paste, it is usually 70 to 250 ° C., for example, in the case of an epoxy resin using a phenol resin as a curing agent, 2 at 150 to 200 ° C. It can be heated and cured for ˜30 minutes to form a conductive circuit in a necessary portion of the substrate surface.

  Examples of the substrate on which the thermosetting conductive paste of the present invention is printed or applied include a silicon substrate, a polyimide film, a PET film, and an FR4 substrate. A substrate having an ITO film on the surface is likely to cause bleed out of the conductive paste. Since the thermosetting conductive paste of the present invention can suppress bleed out, it is preferably applied to, for example, a substrate having an ITO film on the surface.

  Since the thermosetting conductive paste of the present invention can suppress bleed-out of the paste applied on the substrate, it can be suitably used for solar cell electrodes, chip component external electrodes, die bonding agents, and the like. it can.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

The following components were used for the components constituting the thermosetting conductive paste.
(A) Conductive filler flaky silver (Ag) powder, average particle size 10 μm
(B) Thermosetting binder
[Thermosetting resin (epoxy resin)]
Bisphenol A type diglycidyl ether epoxy resin, epoxy equivalent 910-970 g / eq
Modified epoxy resin (manufactured by Dainippon Ink and Chemicals, trade name: EPICLON EXA-4850-150), epoxy equivalent of 350 to 550 g / eq
[Thermosetting resin (epoxy resin with 3 or more functions)]
Polyfunctional epoxy resin 1: α-2,3-epoxypropoxyphenyl-ω-hydropoly (n = 1-7) [2- (2,3-epoxypropoxy) benzylidene-2,3-epoxypropoxyphenylene], epoxy equivalent 160-180 g / eq
Multifunctional epoxy resin 2: Tris (hydroxyphenyl) methane type solid epoxy resin, epoxy equivalent of 169 to 179 g / eq
[Curing agent]
Phenolic resin, softening point 98-102 ° C., hydroxyl group (OH) equivalent 104-106 g / eq
[Curing accelerator]
2-Phenyl-4-methyl-5-hydroxymethylimidazole
[solvent]
Diethylene glycol monobutyl ether (C) cellulose resin High-viscosity ethyl cellulose, viscosity: 150 to 250 mPa · s
Low viscosity ethyl cellulose, viscosity: 8-11 mPa · s
The viscosity of ethyl cellulose was measured according to ASTM D914 by dissolving a solution of ethyl cellulose in a mixed solution having a toluene: ethanol ratio of 80:20 so that the amount of ethyl cellulose was 5% by mass.
(D) Acrylonitrile-butadiene copolymer Carboxy-terminated acrylonitrile-butadiene copolymer, number average molecular weight: 10,000
(E) Other
[Coupling agent]
3-glycidoxypropyltriethoxysilane

(Examples 1-5, Comparative Examples 1-2)
The compositions shown in Table 1 were kneaded at 150 ° C. using a three roll mill to prepare thermosetting conductive pastes of Examples 1 to 5 and Comparative Examples 1 and 2.

[Applicability test]
As shown in FIG. 1, on the end face of the chip inductor 1 (copper internal electrode), a Paloma printing machine (model number: MODEL2001) manufactured by esi Co., Ltd. has a thickness after curing of about 30 μm (distance A). After uniformly dip-coating the thermosetting conductive paste having the composition shown in FIG. 1, the unevenness of the coated surface 2 was observed 10 times with an optical microscope. The case where the distance B from the top of the convex portion to the bottom point of the concave portion was less than 1 μm was marked as “◯”, the case where it was 1 to 3 μm was Δ, and the case where it exceeded 3 μm was marked as “X”. The results are shown in Table 1.

[Measuring method of the fluctuation index]
The viscosity of the thermosetting conductive paste was measured at 20 ° C. using a Brookfield B-type viscometer. The ratio of the measured values at 5 rpm and 50 rpm (5 rpm / 50 rpm) was used as the throttling index.

[Measurement method of specific resistance]
Using a screen of a thermosetting conductive paste on a silicon substrate having an ITO-treated surface, a screen of a stainless steel 290 mesh, emulsion thickness 20 μm, clearance 1.5 mm, printing pressure 0.32 MPa, squeegee angle A pattern of 0.1 × 150 mm was printed at 70 ° and a squeegee speed of 150 mm / sec. This printed pattern was cured at 200 ° C. for 30 minutes using a hot air dryer. The specific resistance value of the linear pattern after curing is measured by a four-terminal method using an LCR meter, and the cross-sectional area of the linear pattern after curing is measured using a three-dimensional shape measuring apparatus (manufactured by MITANI CORPORATION). did.

[Measurement method of viscosity]
The viscosity of the thermosetting conductive paste was measured at 20 ° C. using a Brookfield B-type viscometer (10 rpm). The results are shown in Table 1.

  As shown in Table 1, Examples 1 to 5 have moderate thixotropy with a throttling index of 5.0 or less, and were confirmed to have good coating suitability. In addition, as shown in Comparative Examples 1 and 2, when a specific amount of cellulose resin was not contained, the coating suitability was inferior to that of Examples 1 to 5.

(Examples 6-15, Comparative Examples 3-4)
The compositions shown in Table 2 were kneaded at 150 ° C. using a three-roll mill to prepare thermosetting conductive pastes of Examples 6 to 15 and Comparative Examples 3 to 4. The solvent was added so that the thermosetting conductive paste had a viscosity of 200 to 300 Pa · s. The viscosity was measured at 20 ° C. using a Brookfield B-type viscometer (10 rpm).
A printed pattern was formed from the thermosetting conductive paste in the same manner as the specific resistance measurement method, and the printed pattern was cured at 200 ° C. for 30 minutes using a hot air dryer. The pattern formed using each thermosetting conductive paste after curing was photographed 20 times using a CCD image sensor (Charge Coupled Device Image Sensor). Examples 7 to 10 and 14 of FIGS. 2 to 6 are shown in FIGS. 2 to 6, respectively, among photographs of linear patterns formed using the thermosetting conductive paste. In addition, the specific resistance value of the linear pattern after curing was measured in the same manner as the specific resistance value measurement method. The results are shown in Table 2.

[Measurement method of bleed width]
The bleed width was measured from the CCD photograph. The results are shown in FIGS.

[Printability test]
The printability was measured using a three-dimensional shape measuring device (manufactured by MITANI CORPOATION) for the distance from the top of the convex portion to the bottom of the concave portion of the three-dimensional irregularities on the surface of the screen-printed cured film. The results are shown in Table 2.

As shown in Table 2, Examples 6 to 15 maintain good printability and maintain a low specific resistance value of 1.27 × 10 ⁻⁵ (Ω · m) or less. The bleed width could be reduced. In particular, as shown in Examples 6 to 11, (C) cellulose resin with respect to 100% by mass of the total amount of (B) thermosetting binder, (C) cellulose resin, and (D) acrylonitrile-butadiene copolymer. The bleed width can be reduced to 82 μm or less when the content of the resin is within the range of 15 to 60% by mass, and the bleed when the content of the cellulose resin is within the range of 20 to 50% by mass. The width could be further reduced to 33 μm or less, and bleeding out could be suppressed. As shown in Examples 6-9 and 14, even when low-viscosity ethyl cellulose is used as the cellulose resin, high-viscosity ethyl cellulose is used as shown in Examples 10-12 and 15, However, bleed out could be suppressed. As shown in Examples 6 and 15, when the content of the tri- or higher functional epoxy resin contained in the epoxy resin was less than 50% by mass, the specific resistance value was slightly increased.
On the other hand, as shown in Comparative Examples 3 and 4, if the content of the cellulose resin in the resin of the thermosetting conductive paste is outside the range of 2 to 60% by mass, even if a low specific resistance value can be maintained, Even if the bleed out could not be suppressed and the bleed out could be suppressed, a low specific resistance value could not be maintained.

  Since the thermosetting conductive paste of the present invention can suppress bleed-out while maintaining a low resistance value, it is a terminal for chip electronic components such as a solar cell electrode, a chip capacitor, a chip inductor, and a chip resistor. It can be suitably used for electrodes, die bonding agents and the like.

Claims (4)

(A) a conductive filler, (B) a thermosetting resin, a curing agent, optionally a solvent, and optionally a thermosetting binder comprising a curing accelerator , (C) a cellulose resin, and (D) optionally an acrylonitrile. A thermosetting conductive paste containing a butadiene copolymer,
(B) a thermosetting resin and a curing agent in a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer optionally contained in the thermosetting conductive paste. The total amount is 1 to 10% by mass, (B) a thermosetting resin and a curing agent in the thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile-butadiene copolymer optionally included. The thermosetting conductive paste, wherein the content of (C) the cellulose resin in the total amount of is 5 to 55 % by mass.   (C) The thermosetting conductive paste according to claim 1, wherein the cellulose resin is ethyl cellulose.   (B) The thermosetting conductive paste according to claim 1 or 2, wherein the thermosetting binder contains an epoxy resin and the epoxy resin further contains 50% by mass or more of a trifunctional or higher functional epoxy resin.   (A) The thermosetting conductive paste according to any one of claims 1 to 3, wherein the conductive filler is made of silver or an alloy containing silver.