CONDUCTING COMPOSITION AND THE CONDUCTOR BOARD USING IT

Abstract

Leading composition, which includes: Silver nanoparticles with an average particle diameter of 350 nm to 600 nm, Silver particles with an average particle diameter that is larger than that of the silver nanoparticles, a thermosetting synthetic resin that has an oxirane ring in one molecule, a hardening agent, and a cellulose resin wherein the ratio of the thermosetting resin to the curing agent is 1:1 to 3:1 by mass, the specific resistance of a conductor formed by applying and calcining the conductive composition on a substrate is 5.0 × 10 -6 Ω · cm or less and the conductor does not detach from the substrate when an adhesive tape with an adhesive strength of 3.9 N / 10 mm to 39 N / 10 mm is pressed against the conductor and pulled off.

Description

Technical field

[0001] The present invention relates to a conductive composition and a printed circuit board using it. In particular, the present invention relates to a conductive composition with which a conductor can be obtained that has a specific resistance corresponding to that of raw silver and excellent adhesion to a substrate, and to a printed circuit board using the conductive composition.

[0002] In recent years, the need for flexible printed circuit boards (PCBs) that allow for miniaturization, thinning, three-dimensionalization, and similar modifications of wiring harnesses and their peripheral components has increased due to the shrinking of wiring space in vehicles. In particular, a map light positioned near a rearview mirror in the center of a vehicle's interior should be thin. In other words, with the development of automatic braking and autonomous driving vehicles, the integration of cameras and sensor modules is progressing, requiring these modules to be mounted on the back of the map light. Therefore, a thinner map light is crucial. Consequently, there is a need for a flexible PCB with the properties described above to enable this thinner design.

[0003] Flexible printed circuit boards (FPCs) are known as flexible printed circuit boards that meet the requirements for miniaturization, thinning, three-dimensionalization, and similar applications. In FPCs, an electrical circuit is formed on a substrate obtained by bonding a thin, soft, and electrically insulating base film to a conductive metal, such as copper foil. The FPC circuit is typically produced using a subtractive method. For example, a circuit can be produced by bonding a metal foil, such as copper, to a polyimide film and etching the metal foil. Such subtractive methods require complex and very time-consuming processes, such as photolithography, etching, or vapor deposition, resulting in extremely low throughput.Furthermore, processes such as photolithography, etching, or vapor deposition are problematic with regard to the environment because the waste liquids generated during the processes are problematic.

[0004] To solve the problems described above, an additive method was investigated, in which a conductor pattern is formed on an insulating board in reverse to the subtractive method. Various additive methods exist, including, for example, plating and printing a conductive composition, applying metal to a corresponding part of a substrate, wiring a polyimide-coated cable, and bonding a previously formed pattern to a substrate.

[0005] Of these additive manufacturing methods, printing offers the highest throughput. In printing, an electrical circuit is created using a film as a substrate, a conductive ink or composition is used as the conductive wire material, and this is combined with an insulating film, a coating, or similar material. Such a conductive ink or composition is formed from a metal component, an organic solvent, a reducing agent, an adhesive, or similar substances, and a conductor is formed after coating by calcination to enable conductivity.

[0006] For example, patent document 1 specifies a conductive composition comprising a thermoplastic resin and a thermosetting resin as a binder, a curing agent, and metal particles. Patent document 2 specifies a metal paste obtained by kneading a solid fraction consisting of silver particles and a solvent. Patent document 2 specifies a metal paste containing a predetermined amount of silver particles with a particle diameter of 100 to 200 nm, the average particle diameter of the total silver particles being 60 to 800 nm, and high molecular weight ethylcellulose with an average molecular weight within a predetermined range.

[0007] Patent literature 3 states that a silver compound and a predetermined amine mixture are mixed to form a complex compound containing the silver compound and the amine, and that the complex compound is heated and thermally decomposed to form silver nanoparticles. Patent literature 3 also states a silver coating composition containing the silver nanoparticles and an organic solvent. Patent literature 4 states a curable conductive paste containing an epoxy resin, a curing agent, a conductive powder, and a solvent. Patent literature 5 states a thermosetting conductive paste containing (A) a conductive filler, (B) a thermosetting binder, (C) a cellulose resin, and (D) an acrylonitrile butadiene copolymer, if required.

[0008] Furthermore, JP2011-238596A, US2015 / 0252224A1, and US2009 / 0146117A1 concern leading compositions. Reference list patent literature Patent Literature 1: JP 2013-134914 A Patent literature 2: WO 2017 / 033911 A Patent Literature 3: JP 2013-142173 A Patent Literature 4: JP 2000-239636 A Patent Literature 5: JP 2012-84440 A Summary of the invention

[0009] If a resin component and an adhesive are not added to a conductive composition in a certain quantity, adhesion of the conductor to a substrate cannot be achieved. Conversely, if the resin component or the adhesive is added to the conductive composition in a certain quantity, the contact point of the metal particles is reduced, thereby increasing the resistivity of the conductor. Therefore, even when using the conductive compositions described in patent literature 1 to 5, it is difficult to obtain a conductive composition that produces a conductor with a resistivity comparable to that of raw silver and with excellent adhesion to a substrate.Therefore, it is difficult to obtain a printed circuit board for a motor vehicle that meets the adhesion requirements for a flexible printed circuit board and has a sufficiently low specific resistance.

[0010] The present invention addresses problems from the prior art. It is an object of the present invention to provide a conductive composition with which a conductor with a specific resistance corresponding to that of raw silver and with excellent adhesion to a substrate can be obtained, and furthermore, a printed circuit board using the conductive composition.

[0011] According to the invention, a conductive composition is provided comprising silver nanoparticles with an average particle diameter of 350 nm to 600 nm, silver particles having an average particle diameter larger than that of the nanoparticles, a thermosetting resin having an oxirane ring in one molecule, a curing agent, and a cellulose resin, wherein the specific resistance of a conductor obtained by applying and calcining the conductive composition with hot air at 140°C for 30 minutes on a substrate is 5.0 × 10 -6 Ω · cm or less and the conductor does not detach from the substrate when an adhesive tape with an adhesive strength of 3.9 N / 10 mm to 39 N / 10 mm is pressed against and pulled away from the conductor, wherein the ratio of the thermosetting resin to the curing agent is 1:1 to 3:1 by mass.

[0012] According to a second aspect of the present invention, the thermosetting resin in the leading composition is selected from the group comprising a bisphenol A-type epoxy resin, a bisphenol F-type epoxy resin, a novolac-type epoxy resin, a glycidylamine-type epoxy resin and an aliphatic-type epoxy resin.

[0013] According to another aspect of the present invention, the curing agent in the leading composition is a 5-membered heterocyclic aromatic compound containing nitrogen.

[0014] According to another aspect of the present invention, the proportion of cellulose resin in the conductive composition is 0.1% to 4% by mass in relation to the total conductive composition.

[0015] According to another aspect of the present invention, the total proportion of the thermosetting resin and the curing agent in the conductive composition is 0.1% to 6% by mass in relation to the total conductive composition.

[0016] According to another aspect of the present invention, the total proportion of the thermosetting resin and the curing agent in the conductive composition is 0.1% to 5% by mass in relation to the total conductive composition.

[0017] According to another aspect of the present invention, the total proportion of the thermosetting resin and the curing agent in the conductive composition is 0.1% to 2% by mass in relation to the total conductive composition.

[0018] According to another aspect of the present invention, the average particle diameter of the silver particles in the conductive composition is 1 µm to 5 µm.

[0019] According to a further aspect of the present invention, a printed circuit board is provided which contains a conductor obtained from the conductive composition according to the invention. Description of embodiments [conducting composition]

[0020] The leading composition of the invention comprises silver nanoparticles, silver particles, a thermosetting resin, a curing agent, and a cellulose resin, each within the specifications and proportions of claim 1. The configuration is described in detail below.

[0021] The conductive composition contains silver nanoparticles with an average particle diameter of 350 nm to 600 nm. A metal's melting point typically decreases because the number of metal atoms present on the particle surface increases with the particle diameter. Therefore, a conductor can be formed at a relatively low temperature using such silver nanoparticles in the conductive composition. Furthermore, with an average particle diameter of 350 nm to 600 nm, the spaces between the silver particles can be filled with these nanoparticles. Because the silver nanoparticles and the silver particles are sintered to form a dense sintered body, the conductivity of the conductor obtained through calcination of the conductive composition can be increased.In the present description, the average particle diameter of the silver nanoparticles is understood to be a mean diameter (50% diameter, D50) measured by a light scattering method.

[0022] Using such silver nanoparticles, a fine wiring structure can be formed. Furthermore, the specific resistance of the conductor can be reduced after calcination, and the surface smoothness of the conductor can be improved. Silver is used because it can be easily reduced by calcining the conductive composition to form a dense sintered body and thus reduce the specific resistance of the resulting conductor.

[0023] The conductive composition according to this embodiment contains silver particles with an average particle diameter larger than that of the silver nanoparticles, in addition to the silver nanoparticles mentioned above. Using such silver particles, the conductor can be densified after calcination, and its resistivity can be reduced.

[0024] The average particle diameter of the silver particles is preferably 1 µm to 5 µm. If the average particle diameter of the silver particles is within this range, the conductivity of the conductor can be increased. Furthermore, as described below, even when the conductive composition is applied to an insulating substrate using a screen-printing method, a fine circuit can be efficiently formed because the silver particles are unlikely to clog the screen-printing mesh. It should be noted that in this description, the average particle diameter of the silver particles refers to a mean diameter (50% diameter, D50) measured by a light scattering method.

[0025] By using silver particles, the resistance of the conductor can be reduced after calcination, and the surface smoothness of the conductor can be improved. Silver is used because it can be easily reduced by calcining the conductive composition to form a dense sintered body and thus reduce the specific resistance of the resulting conductor.

[0026] In the conductive composition of this embodiment, no specific requirements are placed on the ratio of silver nanoparticles to silver particles, which is preferably, for example, 1:9 to 9:1 by mass. If the ratio of silver nanoparticles to silver particles is within this range, a conductor formed from a dense sintered body with improved conductivity can be obtained. Furthermore, if the ratio of silver nanoparticles is smaller than this range, it may be difficult to achieve the desired specific resistance of the conductor. Conversely, if the ratio of silver nanoparticles is higher than this range, the viscosity of the conductive composition is reduced, and the operational efficiency may be impaired.

[0027] The conductive composition according to this embodiment contains a thermosetting resin that includes an oxirane ring in its molecule. Oxirane, also known as ethylene oxide, is a three-membered ring ether. When a conductor is formed using such a thermosetting resin by applying and drying the conductive composition onto a substrate, the adhesion between the substrate and the conductor can be improved.

[0028] With regard to the thermosetting resin having an oxirane ring in the molecule, no special requirements are specified here, wherein it is preferably at least one selected from the group comprising a bisphenol-A type epoxy resin, a bisphenol-F type epoxy resin, a novolac type epoxy resin, a glycidylamine type epoxy resin and an aliphatic type epoxy resin.

[0029] No specific requirements are given regarding the curing agent, as long as the thermosetting resin contained in the conductive composition can be cured. For example, an imidazole curing agent, an amide curing agent, a phenol curing agent, an amine curing agent, an acid anhydride curing agent, or similar can be used. The curing agent can be used alone or in a combination of two or more different curing agents.

[0030] Examples of the imidazole curing agent are imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 1-cyanothethyl-2-undecylimidazole, 1-cyano-2-phenylimidazole, 1-cyanoethyl-2-undecyimidazole trimellitate and 1-cyanoethyl-2-phenylimidazole trimellitate.

[0031] An example of the amide curing agent is dicyandiamide.

[0032] An example of a phenolic hardening agent is a phenolic resin.

[0033] Examples of amine curing agents include aliphatic amines such as diethylenetriamine, triethylenetetramine, tetraethylenpentamine and N-aminoethylpiperazine, and aromatic amines such as toluenediamine, xylenediamine, diaminodiphenylmethane, phenylenediamine and diaminodiphenylsulfone.

[0034] Examples of acid anhydrite curing agents include phthalic anhydride, trimetellitic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, and nadic anhydride.

[0035] The curing agent is preferably a 5-membered heterocyclic aromatic compound containing nitrogen. This 5-membered heterocyclic aromatic compound is a heterocyclic compound containing carbon and nitrogen, exhibiting a 5-membered ring and aromaticity. Because such a curing agent generally has a curing start temperature of 100°C or less, even when a conductive composition is prepared and applied to a substrate or similar, curing does not simply start at room temperature and can be initiated directly after calcination. Therefore, for example, when manufacturing a printed circuit board, the conductive composition can be easily handled. For example, an imidazole curing agent can be used as the curing agent for the 5-membered heterocyclic aromatic compound containing nitrogen.

[0036] According to the invention, the ratio of the thermosetting resin to the curing agent is 1:1 to 3:1 by mass. By setting the ratio of the thermosetting resin to the curing agent within the aforementioned range, the reactivity between the thermosetting resin and the curing agent is further improved, thus promoting the curing of the conductive composition.

[0037] The conductive composition of this embodiment contains a cellulose resin. Uniform dispersion of the cellulose resin within the conductive composition prevents any increase in the conductive composition's flowability and any impairment of its compressive strength. Furthermore, because the thermosetting resin and the curing agent are interlinked by the uniform dispersion of the cellulose resin within the conductive composition, the adhesion between the conductor formed by calcining the conductive composition and the substrate is improved.

[0038] Examples of cellulose resin include cellulose ethers, cellulose esters, and cellulose ether esters, with cellulose ether being the preferred choice. Examples of cellulose ethers include a simple cellulose ether in which one type of ether group is bonded to cellulose, and a mixed cellulose ether in which two or more types of ether groups are bonded to cellulose. Specific examples of simple cellulose ethers are methylcellulose, ethylcellulose, propylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose. Specific examples of mixed cellulose ethers are methylethylcellulose, methylpropylcellulose, ethylpropylcellulose, hydroxymethylethylcellulose, hydroxypropylmethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, or similar compounds. The cellulose ether can be used alone or in combination with two or more types.It should be noted that the cellulose resin is preferably ethylcellulose.

[0039] No specific requirements are given here regarding the proportion of cellulose resin in the conductive composition, although it is preferably provided in such a way as to enhance the compressibility of the conductive composition. In particular, the proportion of cellulose resin is preferably 0.1% to 4% by mass of the total conductive composition. If the proportion of cellulose resin is 0.1% by mass or more, the adhesion between the conductor formed by calcining the conductive composition and the substrate can be further improved. And if the proportion of cellulose resin is 4% by mass or less, an excessive increase in the flowability of the conductive composition can be prevented, and the compressibility of the conductive composition can be improved.And if the proportion of cellulose resin is 4% by mass or less, the proportion of the relative metal component in the conductor increases, thereby improving the conductor's conductivity. The proportion of cellulose resin is preferably 0.1% to 2% by mass of the total conductive composition.

[0040] The conductive composition of this embodiment may contain an organic solvent for the uniform dispersion of the silver nanoparticles, the silver particles, a thermosetting resin, a curing agent, and a cellulose resin. No specific requirements are made regarding the organic solvent, as long as it can strongly disperse the silver particles and dissolve the thermosetting resin, the curing agent, and the cellulose resin.

[0041] Preferably, the organic solvent used is an organic solvent with a total of 8 to 16 carbon atoms, a hydroxyl group, and a boiling point of 280°C or lower. In particular, at least one of the following may be used as the organic solvent: diethylene glycol monoethyl ether acetate (C8, boiling point of 218°C), terpineol (C10, boiling point of 219°C), dihydroterpineol (C10, boiling point of 220°C), texanol (C12, boiling point of 260°C), 2,4-dimethyl-1,5-pentadiol (C9, boiling point of 150°C), and butylcarbitol (C8, boiling point of 230°C). Furthermore, at least one of the following organic solvents can be used: isophorone (boiling point of 215°C), ethylene glycol (boiling point of 197°C), butylcarbitol acetate (boiling point of 247°C) and 2,2-4-trimethyl-1,3-pentanediol diisoburyrate (C16, boiling point of 280°C).

[0042] No specific requirements are given regarding the additional amount of organic solvent in the conductive composition; however, a viscosity is preferably provided that allows the conductive composition to be applied by a screen printing method or similar technique. In particular, the proportion of organic solvent is preferably 10% to 25% by mass of the total conductive composition.

[0043] The conductive composition may contain additives to improve printing and conductivity properties, such as a defoamer, surfactant, rheology additive, or similar substances, provided that the dispersion stability of the paste and the conductor's performance after calcination are not affected.

[0044] In the conductive composition of the invention, the specific resistance of a conductor formed by applying and calcining the conductive composition on a substrate is 5.0 × 10 -6 Ω or less. By setting the conductor's resistivity to such a value, the conductor's resistivity can be made equal to that of raw silver. The conductor's resistivity can be measured according to JIS K7194 (Resistance Test Method for Conductive Plastics Using a Four-Sensor Method). In particular, the conductor's resistivity can be measured using a four-sensor resistance measuring instrument.

[0045] In the conductive composition of the invention, the conductor does not detach from the substrate when an adhesive tape with an adhesive strength of 3.9 N / 10 mm to 39 N / 10 mm is pressed against and removed from the conductor. "The conductor does not detach from the substrate" means that when the adhesive tape is pressed against and removed from the conductor, no detachment of the conductor from the substrate is visible on the adhesive tape side, nor is any detachment of the conductor visible on the printed circuit board side. If the conductor formed by applying and calcining the conductive composition on the substrate exhibits such properties, the conductor has sufficient adhesion to the substrate, allowing the printed circuit board to be made smaller, thinner, and three-dimensional.The adhesive strength of the adhesive tape is preferably 4.3 N / 10 mm or more and 39 N / 10 mm or less, and even better 5.3 N / 10 mm or more and 38 N / 10 mm or less.

[0046] As described above, the conductive composition consists of a metal component, i.e., silver nanoparticles and silver particles, and a resin component, i.e., the specific thermosetting resin mentioned above, a curing agent, and a cellulose resin. The conductor is then formed by a specific calcination process after the conductive composition has been applied to a substrate. Preferably, a certain amount of the resin component is added to the conductive composition to improve the adhesion between the resulting conductor and the substrate.

[0047] Solder can bond easily to metal, but is difficult to bond to resin. For this reason, the resin component can reduce the wettability between the conductor and the solder during assembly, making it difficult to form a concave shape or a solder ball. In this case, sufficient bond strength between the conductor and the mounted component may not be achieved.

[0048] For this reason, the total proportion of the thermosetting resin and the curing agent is preferably between 0.1% and 6% by mass of the total conductive composition. If the total proportion is 0.1% by mass or more, the adhesion between the conductor formed by the calcination of the conductive composition and the substrate can be improved. And if the total proportion is 6% by mass or less, the proportion of the relative metal component is increased, which can improve the conductivity of the conductor.

[0049] Furthermore, the total proportion of the thermosetting resin and the curing agent is preferably 0.1% to 5% by mass, even better 0.1% to 4% by mass, and particularly preferably 0.1% to 2% by mass of the total conductive composition. By setting the total proportion of the thermosetting resin and the curing agent within this range, the resin component in the resulting conductor is reduced, thus improving the wettability of the solder to the conductor. Therefore, by reducing the resin component in the overall conductive composition, the silver nanoparticles and the silver particles are easily brought into contact with each other, promoting sintering, thereby reducing the pore size and obtaining a conductor with a high metal concentration.Such a conductor makes it possible to achieve seemingly contradictory properties simultaneously, such as adhesion to a substrate and solder wettability. And because such a conductor exhibits a low flux density on its surface after calcination, excellent solder wettability can be maintained.

[0050] As described above, the conductive composition of this embodiment contains silver nanoparticles with an average particle diameter of 350 nm to 600 nm, silver particles with an average particle diameter larger than that of the silver nanoparticles, a thermosetting resin having an oxirane ring in the molecule, a curing agent, and a cellulose resin. According to the invention, the specific resistance of the conductor formed by applying and calcining the conductive composition on the substrate is 5.0 × 10⁻⁶. -6Ω·cm or less. And the conductor does not detach from the substrate when adhesive tape with a strength of 3.9 N / 10 mm to 39 N / 10 mm is pressed against and removed from the conductor. Therefore, a conductor with a resistivity comparable to that of raw silver and excellent adhesion to the substrate can be obtained. Accordingly, it can be used for a printed circuit board in a motor vehicle.

[0051] Furthermore, the conductor formed by calcining the conductive composition of this embodiment exhibits excellent solder wettability. Therefore, when a component is mounted on a conductor using solder, sufficient mounting strength can be achieved. [Circuit board]

[0052] The printed circuit board according to this embodiment contains a conductor obtained from the conductive composition described above. As further described above, the conductor obtained from the conductive composition of the present invention has a specific resistance of 5.0 × 10⁻⁶. -6 Ω·cm or less and excellent adhesion (good results are achieved with an adhesive tape with an adhesive strength of 3.9 N / 10 mm to 39 N / mm). Because the circuit board exhibits adhesion that withstands long-term use and can increase the amount of current flowing through the conductor, it is suitable for use in motor vehicles.

[0053] The printed circuit board of the present embodiment is obtained by calcining the conductive composition after it has been applied to the substrate in a desired shape. No specific requirements are made here regarding the substrate that can be used for the printed circuit board; an electrically insulating film or a sheet material may be used. Such a substrate is flexible and can be bent, etc., depending on its position. No specific requirements are made here regarding the material of the substrate; for example, at least one material from the group comprising polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polypropylene (PP), and polybutylene terephthalate (PBT) may be used.

[0054] No specific requirements are given regarding the method for applying the conductive composition to the substrate; any known method such as flexographic printing, engraved printing, engraved offset printing, offset printing, screen printing or rotary printing may be used.

[0055] According to the invention, the substrate coated with the conductive composition is exposed to hot air at 140°C for 30 minutes for calcination. Because the organic solvent or similar substance is removed from the conductive composition and the silver nanoparticles and silver particles are sintered, a highly conductive conductor can be obtained.

[0056] The printed circuit board with the conductor obtained from the conductive composition can include an insulating cover material for covering and protecting the conductor's surface. An insulating film or a covering agent can be used as the insulating cover material. Preferably, the insulating cover material is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polypropylene (PP), polybutylene terephthalate (PBT), polyurethane (PU), or a similar material with an adhesive on one side. Furthermore, the covering agent is preferably a thermosetting or UV-curable covering agent, and particularly preferably an epoxy or urethane covering agent.

[0057] The present embodiment will now be described in detail with reference to examples and comparative examples, although the present invention is not limited to these examples. Example 1 [Preparation of a leading committee]

[0058] First, a conductive composition for each example was prepared by stirring silver nanoparticles, silver particles, a thermosetting resin, a curing agent, a resin, and an organic solvent in a mixing ratio specified in Tables 1 to 5 using a rotary stirrer. The materials used as raw materials for the conductive composition for each example are listed below. (Silver nanoparticles)

[0059] Silver nanoparticles with average particle diameters of 25 nm, 30 nm, 70 nm, 350 nm, 600 nm and 700 nm. (Silver particles)

[0060] Silver particles with average particle diameters of 1.0 µm, 3.0 µm, 5.0 µm and 6.0 µm. (Heat-curing synthetic resin) • Bisphenol A type epoxy resin, jER (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation. • Bisphenol F-type epoxy resin, EPICLON (registered trademark) 830, manufactured by DIC Corporation. • Aliphatic epoxy resin, PG-207GS (polypropylene glycol diglycidyl ether), manufactured by NIPPON STEEL Chemical & Material Co., Ltd. • Novolak-type epoxy resin, YPDPN-638 (Phenol-Novolak-type epoxy resin), manufactured by NIPPON STEEL Chemical & Material Co., Ltd. • Phenolic resin, PS-2608, manufactured by Gun Ei Chemical Industry Co., Ltd. • Urethane resin, UREARNO (registered trademark) KL-422, manufactured by Arakawa Chemical Industries, Ltd. (Curing agent) • Dicyandiamide, DICY7, manufactured by Mitsubishi Chemical Corporation. • Imidazole, NISSOCURE (registered trademark) TIC-188, manufactured by Nippon Soda Co., Ltd. • Hexamethylenetetramine, manufactured by Mitsubishi Gas Chemical Company, Inc. • Polyisocyanate, BURNOCK (registered trademark) D-750, manufactured by DIC Corporation. (Synthetic resin component) • Hydroxyethylmethylcellulose, METOLOSE (registered trademark) SEB04T, manufactured by Shin-Etsu Chemical Co., Ltd. • Ethyl cellulose, ETHOCEL (registered trademark) STD4, prepared by The Dow Chemical Company. • Ethyl cellulose acrylic polymer, ACRIT (registered trademark) KWE-250T, prepared by Taisei Fine Chemical Co., Ltd. • Polyamide, F-915, prepared by Tokyo Printing Ink Mfg.Co., Ltd. • Acrylic resin, ACRYDIC (registered trademark) 52-204, manufactured by DIC Corporation. (Organic solvent) • Terpineol, manufactured by Tokyo Chemical Industry Co., Ltd. • Dieethylene glycol monoethyl ether acetate, manufactured by Tokyo Chemical Industry Co., Ltd. • Texanol (2,2,4-Trimethylpentane-1,3-diolmonisobutyrate), manufactured by Eastman Chemical Company NYSE: EMN. [Evaluation]

[0061] The leading composition of each example was evaluated as follows. The results are given in Tables 1 to 5. (Specific resistance of the conductor)

[0062] The specific resistance of the conductor was measured according to JIS K7194. A four-probe resistance meter (Sigma-5+ resistance meter, manufactured by NPS Corporation) was used for this purpose.

[0063] Specifically, a circuit using the conductive composition obtained in each example was first printed onto a polyimide film using a screen printer, so that after calcination the width was 1 mm, the length 10 cm, and the thickness 30 µm. The polyimide film with the printed circuit was then left to stand at room temperature for 30 minutes and calcined with hot air at 140°C for 30 minutes to produce a printed circuit board.

[0064] The surface resistance of the resulting silver thin film on the circuit board was then measured at three points: 1 cm sections at both ends and a 5 cm section in the middle. It should be noted that the surface resistance was measured with the needle positioned parallel to the circuit. (Liability 1)

[0065] The adhesion of the conductive composition to the polyimide film was evaluated by a peel test using an adhesive tape with an adhesive strength of 3.9 N / 10 mm to 5.7 N / 10 mm.

[0066] Specifically, a circuit using the conductive composition obtained in each example was first printed onto a polyimide film using a screen printer, so that after calcination the width was 1 mm, the length 10 cm, and the thickness 30 µm. The polyimide film with the printed circuit was then left at room temperature for 30 minutes and calcined with hot air at 140°C for 30 minutes to produce a printed circuit board.

[0067] The adhesive side of the tape was then pressed against the printed circuit board with the fingers to ensure no bubbles remained. After approximately 10 seconds, the tape was quickly peeled back in a direction perpendicular to the printed surface. The tape used was aluminum tape No. 950, manufactured by Nichiban Co., Ltd., with an adhesive strength of 5.30 N / 10 mm. • Criteria ◯: No pressure delamination is visible (no detached circuitry is visible on the adhesive tape side, and no circuit delamination is visible on the printed circuit board side) ×: Pressure delamination is visible (a detached circuit is visible on the side of the adhesive tape, or a delamination of the circuit is visible on the side of the printed circuit board) (Bleeding out)

[0068] Bleeding from the printed circuit was evaluated as follows. First, a circuit using the conductive composition obtained in each example was printed onto a polyimide film using a screen printer. After calcination, the film was 1 mm wide, 10 cm long, and 30 µm thick. The polyimide film with the printed circuit was then left at room temperature for 30 minutes and subsequently calcined with hot air at 140°C for 30 minutes to create a printed circuit board. The circuit board was then checked for visible bleed. • Criteria ◯: No bleeding is visible ×: Bleeding is visible (Get lost)

[0069] Printing runout was evaluated as follows. First, a circuit diagram was printed onto a polyimide film using the conductive composition obtained in each example, using a screen printer. After calcination, the film was printed to a width of 1 mm, a length of 10 cm, and a thickness of 30 µm. The polyimide film with the printed circuit was then left to stand at room temperature for 10 minutes. Subsequently, the presence of runout at the printing boundary was checked under a microscope and evaluated. • Criteria ◯: No fading is visible ×: A fading effect is visible (Sagging)

[0070] Print sag was assessed as follows. First, a circuit was printed onto a polyimide film using the conductive composition obtained in each example, using a screen printer. After calcination, the film was 1 mm wide, 10 cm long, and 30 µm thick. The polyimide film with the printed circuit was then left at room temperature for 10 minutes. Subsequently, a microscope was used to check whether a printed part corresponded to a transfer shape provided by a screen-printed mask, and any sag was evaluated. • Criteria ◯: No sagging is visible ×: A sag is visible (tissue print)

[0071] A tissue impression was evaluated as follows. First, a circuit using the conductive composition obtained in each example was printed onto a polyimide film using a screen printer, so that after calcination the width was 1 mm, the length 10 cm, and the thickness 30 µm. The polyimide film with the printed circuit was then left at room temperature for 10 minutes. Subsequently, a microscopic examination was performed to check for a visible tissue impression on the surface of the printed part, and the tissue impression was evaluated. • Criteria ◯: No tissue imprint is visible ×: A tissue imprint is visible (Squeegee retention properties)

[0072] The squeegee adhesion properties during printing were evaluated as follows. First, three layers of the circuit, using the conductive composition obtained in each example, were printed onto a polyimide film using a screen printer. After calcination, the layers were 1 mm wide, 10 cm long, and 30 µm thick. The squeegee was then lifted after printing, and the adhesion of the conductive composition to the squeegee was assessed. • Criteria ⊚: A heavy conductive compound adheres to the squeegee. ◯: A heavy conductive composition adheres to the squeegee but falls off within 5 seconds. ×: A heavy conductive composition adheres to the squeegee and does not detach. [Table 1] According to the invention, only those compositions are those that have silver nanoparticles with an average particle diameter of 350 nm to 600 nm. material Material specification Example 1-1 Example 1-2 Examples 1-3 Examples 1-4 Examples 1-5 Silver nanoparticles (mass fractions) 25 nm - - - - - 30 nm - - - - - 70 nm 40 - - 20 - 350 nm - 40 - - 30 600 nm - - 40 - - 700 nm - - - - - Silver particles (mass fractions) 1,0 µm 40 - - 60 - 3,0 µm - 40 - - 50 5,0 µm - - 40 - - 6,0 µm - - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin 0,1 - - - - Bisphenol F-type epoxy resin - 3 - - - aliphatic epoxy resin - - 3,2 - - Novolak-type epoxy resin - - - 1,5 2,4 Phenolic resin - - - - - Urethane resin - - - - - Curing agent (bulk parts) Dicyandiamide 0,1 - 0,8 - - Imidazol - 1 - 0,75 0,8 Hexamethylenetetramine - - - - - Polyisocyanat - - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose 0,1 - 4 - - Ethyl cellulose - 2 - - 3 Ethyl cellulose acrylic polymer - - - 2 - polyamide - - - - - acrylic resin - - - - - Terpineol 19,7 - - 15,75 - Organic solvent (bulk) Diethylene glycol monoethyl ether acetate - 14 - - 13,8 Texanol - - 12 - - Characteristics specific resistance (Ω · cm) 3,1 ×10 -6 4,5 ×10 -6 4,2 ×10 -6 4,2 ×10 -6 4,9 ×10 -6 Liability 1 ◯ ◯ ◯ ◯ ◯ Printing properties Bleeding out ◯ ◯ ◯ ◯ ◯ Get lost ◯ ◯ ◯ ◯ ◯ Sagging ◯ ◯ ◯ ◯ ◯ Tissue print ◯ ◯ ◯ ◯ ◯ Squeegee firm-holding properties ⊚ ⊚ ◯ ⊚ ◯ [Table 2] According to the invention, only those compositions are those that have silver nanoparticles with an average particle diameter of 350 nm to 600 nm. material Material specification Examples 1-6 Example 1-7 Examples 1-8 Examples 1-9 Example 1-10 Silver nanoparticles (mass fractions) 25 nm - - - - - 30 nm - - - 10 35 70 nm - 55 - - - 350 nm - - 65 - - 600 nm 50 - - - - 700 nm - - - - - Silver particles (mass fractions) 1,0 µm - - 20 70 45 3,0 µm - 20 - - - 5,0 µm 30 - - - - 6,0 µm - - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - 0,5 - - Bisphenol F-type epoxy resin - 2 - 0,1 - aliphatic epoxy resin 1 - - - - Novolak-type epoxy resin - - - - 0,1 Phenolic resin - - - - - Urethane resin - - - - - Curing agent (bulk parts) Dicyandiamide - 1 0,5 - - Imidazol 1 - - 0,1 0,1 Hexamethylenetetramine - - - - - Polyisocyanat - - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose - - - - - Ethyl cellulose - - 2 1 1 Ethyl cellulose acrylic polymer 1,5 1 1 - - polyamide - - - - - acrylic resin - - - - - Organic solvent (bulk) Terpineol - 21 11 - - Diethylene glycol monoethyl ether acetate - - - - - Texanol 16,5 - - 18,8 18,8 Characteristics specific resistance (Ω · cm) 3,5 ×10 -6 4,5 ×10 -6 3,5 ×10 -6 3,8 ×10 -6 4,1 ×10 -6 Liability 1 ◯ ◯ ◯ ◯ ◯ Printing properties Bleeding out ◯ ◯ ◯ ◯ ◯ Get lost ◯ ◯ ◯ ◯ ◯ Sagging ◯ ◯ ◯ ◯ ◯ Tissue print ◯ ◯ ◯ ◯ ◯ Squeegee firm-holding properties ⊚ ◯ ◯ ◯ ◯ [Table 3] material Material specification Comparison example 1-1 Comparison example 1-2 Comparison example 1-3 Comparison example 1-4 Silver nanoparticles (mass fractions) 25 nm - - - - 30 nm - - - - 70 nm - - 50 40 350 nm - 60 - - 600 nm 60 - - - 700 nm - - - - Silver particles (mass fractions) 1,0 µm - - 30 40 3,0 µm 20 20 - - 5,0 µm - - - - 6,0 µm - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - - - Bisphenol F-type epoxy resin - - - - aliphatic epoxy resin 4 2 1 1 Novolak-type epoxy resin - - - - Phenolic resin - - - - Urethane resin - - - - Curing agent (bulk parts) Dicyandiamide - - - - Imidazol 1 0,3 0,25 0,25 Hexamethylenetetramine - - - - Polyisocyanat - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose - - - - Ethyl cellulose 1 1 0,05 4,5 Ethyl cellulose acrylic polymer - - - - polyamide - - - - acrylic resin - - - - Organic solvent (bulk) Terpineol - - - - Diethylene glycol monoethyl ether acetate - - 18,75 18,75 Texanol 15 17,7 - - Characteristics specific resistance (Ω · cm) 9,0 × 10 -6 4,4 × 10 -6 3,9 × 10 -6 1,1 × 10 -5 Liability 1 ◯ × × × Printing properties Bleeding out ◯ ◯ ◯ ◯ Get lost ◯ × × ◯ Sagging ◯ ◯ × ◯ Tissue print ◯ ◯ ◯ ◯ Squeegee firm-holding properties ◯ ◯ × × [Table 4] material Material specification Comparison example 1-5 Comparison example 1-6 Comparison example 1-7 Comparison example 1-8 Comparison example 1-9 Silver nanoparticles (mass fractions) 25 nm - 20 - - - 30 nm - - - - - 70 nm - - 50 40 - 350 nm - - - - 20 600 nm - - - - - 700 nm 20 - - - - Silver particles (mass fractions) 1,0 µm 60 60 - 40 - 3,0 µm - - - - 60 5,0 µm - - - - - 6,0 µm - - 30 - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - - - - Bisphenol F-type epoxy resin - - - - - aliphatic epoxy resin 1 1 3 - - Novolak-type epoxy resin - - - - - Phenolic resin - - - 2 - Urethane resin - - - - 2 Curing agent (bulk parts) Dicyandiamide - - - - - Imidazol 0,25 0,25 0,2 - - Hexamethylenetetramine - - - 2 - Polyisocyanat - - - - 2 Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose 1 1 - 1 - Ethyl cellulose - - 1,5 - 1 Ethyl cellulose acrylic polymer - - - - - polyamide - - - - - acrylic resin - - - - - Organic solvent (bulk) Terpineol - - - - - Diethylene glycol monoethyl ether acetate 18,75 18,75 16,8 16 - Texanol - - - - 16 Characteristics specific resistance (Ω · cm) 2,1 ×10 -5 1,6 ×10 -5 4,5 ×10 -5 3,9 ×10 -5 3,4 ×10 -5 Liability 1 × ◯ ◯ × ◯ Printing properties Bleeding out ◯ × × ◯ ◯ Get lost ◯ ◯ × ◯ ◯ Sagging ◯ ◯ × ◯ × Tissue print ◯ ◯ × ◯ ◯ Squeegee firm-holding properties ◯ × ◯ ◯ ◯ [Table 5] material Material specification Comparison example 1-10 Comparison example 1-11 Comparison example 1-12 Comparative example 1-13 Silver nanoparticles (mass fractions) 25 nm - - - - 30 nm - - - - 70 nm - - - - 350 nm 30 30 - - 600 nm - - 40 40 700 nm - - - - Silver particles (mass fractions) 1,0 µm - - - - 3,0 µm - - - - 5,0 µm 50 50 40 40 6,0 µm - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - - - Bisphenol F-type epoxy resin - - - - aliphatic epoxy resin 2 2 2 2 Novolak-type epoxy resin - - - - Phenolic resin - - - - Urethane resin - - - - Curing agent (bulk parts) Dicyandiamide - - - - Imidazol 1 1 1 1 Hexamethylenetetramine - - - - Polyisocyanat - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose - - - - Ethyl cellulose - - - - Ethyl cellulose acrylic polymer - - - - polyamide 3 1 - - acrylic resin - - 3 1 Organic solvent (bulk) Terpineol - - - - Diethylene glycol monoethyl ether acetate 17 17 - - Texanol - - 17 17 Characteristics specific resistance (Ω · cm) 7,7 × 10 -5 8,1 × 10 -6 5,6 × 10 -5 7,7 × 10 -6 Liability 1 ◯ × ◯ ◯ Printing properties Bleeding out × × × ◯ Get lost × × × × Sagging × × × × Tissue print × ◯ ◯ ◯ Squeegee firm-holding properties × × × ◯

[0073] As shown in Tables 1 and 2, in printed circuit boards made from the conductive compositions of Examples 1-1 to 1-10, the conductor's resistivity is low and its adhesion to the substrate is excellent. In contrast, as shown in Tables 3 to 5, in printed circuit boards made from the conductive compositions of Comparative Examples 1-1 to 1-13, the conductor's resistivity is high or its adhesion to the substrate is not excellent. Example 2 [Preparation of the leading composition]

[0074] First, a conductive composition of each example was prepared by stirring silver nanoparticles, silver particles, a thermosetting resin, a curing agent, a resin, and an organic solvent in a mixing ratio specified in Tables 6 to 10 using a rotary stirrer. The same material as in Example 1 was used as the raw material for the conductive composition in each example. The conductive compositions of comparison examples 2-2, 2-4 to 2-6, and 2-8 to 2-13 had the same compositions as comparison examples 1-2, 1-4 to 1-6, and 1-8 to 1-13. [Table 6] According to the invention, only those compositions are those that have silver nanoparticles with an average particle diameter of 350 nm to 600 nm. material Material specification Example 2-1 Example 2-2 Example 2-3 Example 2-4 Example 2-5 Silver nanoparticles (mass fractions) 25 nm - - - - - 30 nm - - - - - 70 nm 40 - - 20 - 350 nm - 40 - - 30 600 nm - - 40 - - 700 nm - - - - - Silver particles (mass fractions) 1,0 µm 40 - - 60 - 3,0 µm - 40 - - 50 5,0 µm - - 40 - - 6,0 µm - - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin 0,05 - - - - Bisphenol F-type epoxy resin - 4,5 - - - aliphatic epoxy resin - - 4,8 - - Novolak-type epoxy resin - - - 2,7 4,1 Phenolic resin - - - - - Urethane resin - - - - - Curing agent (bulk parts) Dicyandiamide - - 1,2 - - Imidazol 0,05 1,5 - 1,3 1,4 Hexamethylenetetramine - - - - - Polyisocyanat - - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose 0,1 - 4 - - Ethyl cellulose - 2 - - 3 Ethyl cellulose acrylic polymer - - - 2 - polyamide - - - - - acrylic resin - - - - - Organic solvent (bulk) Terpineol 19,9 - - 16 - Diethylene glycol monoethyl ether acetate - 12 - - 11,5 Texanol - - 10 - - Characteristics specific resistance (Ω · cm) 2,5 ×10 -6 4,9 ×10 -6 4,5 ×10 -6 4,9 ×10 -6 4,1 ×10 -6 Liability 1 ◯ ◯ ◯ ◯ ◯ Liability 2 ◯ ◯ ◯ ◯ ◯ Printing properties Bleeding out ◯ ◯ ◯ ◯ ◯ Get lost ◯ ◯ ◯ ◯ ◯ Sagging ◯ ◯ ◯ ◯ ◯ Tissue print ◯ ◯ ◯ ◯ ◯ Squeegee firm-holding properties ⊚ ⊚ ◯ ⊚ ◯ Mounting properties solder wettability ◯ ◯ ◯ ◯ ◯ Assembly strength ⊚ ◯ ◯ ⊚ ◯ [Table 7] According to the invention, only those compositions are those that have silver nanoparticles with an average particle diameter of 350 nm to 600 nm. material Material specification Example 2-6 Example 2-7 Example 2-8 Example 2-9 Example 2-10 Silver nanoparticles (mass fractions) 25 nm - - - - - 30 nm - - - 10 35 70 nm - 55 - - - 350 nm - - 65 - - 600 nm 50 - - - - 700 nm - - - - - Silver particles (mass fractions) 1,0 µm - - 20 70 45 3,0 µm - 20 - - - 5,0 µm 30 - - - - 6,0 µm - - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - 1 - - Bisphenol F-type epoxy resin - 3,3 - 0,15 - aliphatic epoxy resin 2 - - - - Novolak-type epoxy resin - - - - 0,5 Phenolic resin - - - - - Urethane resin - - - - - Dicyandiamide - 1,7 1 - - Curing agent (bulk parts) Imidazol 2 - - 0,15 0,5 Hexamethylenetetramine - - - - - Polyisocyanat - - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose - - - - - Ethyl cellulose - - 2 1 1 Ethyl cellulose acrylic polymer 1,5 1 1 - - polyamide - - - - - acrylic resin - - - - - Organic solvent (bulk) Terpineol - 19 10 - - Diethylene glycol monoethyl ether acetate - - - - - Texanol 14,5 - - 18,7 18 Characteristics specific resistance (Ω · cm) 4,1 ×10 -6 4,5 ×10 -6 3,5 ×10 -6 3,2 ×10 -6 3,1 ×10 -6 Liability 1 ◯ ◯ ◯ ◯ ◯ Liability 2 ◯ ◯ ◯ ◯ ◯ Printing properties Bleeding out ◯ ◯ ◯ ◯ ◯ Get lost ◯ ◯ ◯ ◯ ◯ Sagging ◯ ◯ ◯ ◯ ◯ Tissue print ◯ ◯ ◯ ◯ ◯ Squeegee firm-holding properties ⊚ ◯ ◯ ◯ ◯ Mounting properties solder wettability ◯ ◯ ◯ ◯ ◯ Assembly strength ⊚ ⊚ ⊚ ⊚ ⊚ [Table 8] material Material specification Comparative example 2-1 Comparative example 2-2 Comparative example 2-3 Comparison example 2-4 25 nm - - - - Silver nanoparticles (mass fractions) 30 nm - - - - 70 nm - - 50 40 350 nm - 60 - - 600 nm 60 - - - 700 nm - - - - Silver particles (mass fractions) 1,0 µm - - 30 40 3,0 µm 20 20 - - 5,0 µm - - - - 6,0 µm - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - - - Bisphenol F-type epoxy resin - - - - aliphatic epoxy resin 5,6 2 5,5 1 Novolak-type epoxy resin - - - - Phenolic resin - - - - Urethane resin - - - - Curing agent (bulk parts) Dicyandiamide - - - - Imidazol 1,4 0,3 1,3 0,25 Hexamethylenetetramine - - - - Polyisocyanat - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose - - - - Ethyl cellulose 1 1 0,05 4,5 Ethyl cellulose acrylic polymer - - - - polyamide - - - - acrylic resin - - - - Organic solvent (bulk) Terpineol - - - - Diethylene glycol monoethyl ether acetate - - 13,2 18,75 Texanol 13 17,7 - - Characteristics specific resistance (Ω · cm) 9,0 × 10 -5 4,4 × 10 -6 7,9 × 10 -5 1,1 × 10 -5 Liability 1 ◯ × ◯ × Liability 2 ◯ × ◯ × Printing properties Bleeding out ◯ ◯ ◯ × Get lost ◯ × × ◯ Sagging ◯ ◯ × ◯ Tissue print ◯ ◯ ◯ ◯ Squeegee firm-holding properties ◯ ◯ × × Mounting properties solder wettability × ◯ × ◯ Assembly strength × - × - [Table 9] material Material specification Comparison example 2-5 Comparison example 2-6 Comparison example 2-7 Comparative example 2-8 Comparison example 2-9 Silver nanoparticles (mass fractions) 25 nm - 20 - - - 30 nm - - - - - 70 nm - - 50 40 - 350 nm - - - - 20 600 nm - - - - - 700 nm 20 - - - - Silver particles (mass fractions) 1,0 µm 60 60 - 40 - 3,0 µm - - - - 60 5,0 µm - - - - - 6,0 µm - - 30 - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - - - - Bisphenol F-type epoxy resin - - - - - aliphatic epoxy resin 1 1 5,1 - - Novolak-type epoxy resin - - - - - Phenolic resin - - - 2 - Urethane resin - - - - 2 Curing agent (bulk parts) Dicyandiamide - - - - - Imidazol 0,25 0,25 0,34 - - Hexamethylenetetramine - - - 2 - Polyisocyanat - - - - 2 Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose 1 1 - 1 - Ethyl cellulose - - 1,5 - 1 Ethyl cellulose acrylic polymer - - - - - polyamide - - - - - acrylic resin - - - - - Organic solvent (bulk) Terpineol - - - - - Diethylene glycol monoethyl ether acetate 18,75 18,75 14,56 16 - Texanol - - - - 16 Characteristics specific resistance (Ω · cm) 2,1 ×10 -5 1,6 ×10 -5 8,2 ×10 -5 3,9 ×10 -5 3,4 ×10 -5 Liability 1 × ◯ ◯ × ◯ Liability 2 × × ◯ × × Printing properties Bleeding out ◯ × x ◯ ◯ Get lost ◯ ◯ × ◯ ◯ Sagging ◯ ◯ × ◯ × Tissue print ◯ ◯ × ◯ ◯ Squeegee firm-holding properties ◯ × ◯ ◯ ◯ Mounting properties solder wettability ◯ ◯ ◯ ◯ ◯ Assembly strength - ⊚ ◯ - ◯ [Table 10] material Material specification Comparison example 2-10 Comparative example 2-11 Comparative example 2-12 Comparative example 2-13 Silver nanoparticles (mass fractions) 25 nm - - - - 30 nm - - - - 70 nm - . - - 350 nm 30 30 - - 600 nm - - 40 40 700 nm - - - - Silver particles (mass fractions) 1,0 µm - - - - 3,0 µm - - - - 5,0 µm 50 50 40 40 6,0 µm - - - - Heat-curing synthetic resin (mass-produced parts) Bisphenol A type epoxy resin - - - - Bisphenol F-type epoxy resin - - - - aliphatic epoxy resin 2 2 2 2 Novolak-type epoxy resin - - - - Phenolic resin - - - - Urethane resin - - - - Curing agent (bulk parts) Dicyandiamide - - - - Imidazol 1 1 1 1 Hexamethylenetetramine - - - - Polyisocyanat - - - - Synthetic resin component (mass-produced parts) Hydroxyethylmethylcellulose - - - - Ethyl cellulose - - - - Ethyl cellulose acrylic polymer - - - - polyamide 3 1 - - acrylic resin - - 3 1 Organic solvent (bulk) Terpineol - - - - Diethylene glycol monoethyl ether acetate 17 17 - - Texanol - - 17 17 Characteristics specific resistance (Ω · cm) 7,7 × 10 -5 8,1 × 10 -6 5,6 × 10 -5 7,7 × 10 -6 Liability 1 ◯ × ◯ ◯ Liability 2 ◯ × ◯ × Printing properties Bleeding out × × × ◯ Get lost × × × × Sagging × × × × Tissue print × ◯ ◯ ◯ Squeegee firm-holding properties × × × ◯ Mounting properties solder wettability ◯ ◯ ◯ ◯ Assembly strength ⊚ - ⊚ ⊚ [Evaluation]

[0075] For the conductive composition of each example, assessments were performed for "conductor specific resistance", "adhesion 1", "bleeding", "running", "sagging", "fabric imprint", and "setting properties", as in Example 1. Furthermore, the following assessment was also performed for the conductive composition of each example. The results are given in Tables 6 to 10. (Liability 2)

[0076] First, a circuit using the conductive composition obtained in each example was printed onto a polyimide film using a screen printer, so that after calcination the width was 1 mm, the length 10 cm, and the thickness 30 µm. The polyimide film with the printed circuit was then left at room temperature for 30 minutes and subsequently calcined with hot air at 140°C for 30 minutes to create a printed circuit board.

[0077] The adhesive side of a strip of tape was then pressed against the printed circuit board with the fingers, ensuring no air bubbles remained. After approximately 10 seconds, the tape was quickly peeled off in a direction perpendicular to the printed surface. The tape used was an ultra-strong, low-VOC VHB double-sided tape, product number Y-4825K-08 from 3M, with an adhesive strength of 38 N / 10 mm. • Criteria ◯: No pressure delamination is visible (no detached circuitry is visible on the adhesive tape side, and no circuit delamination is visible on the printed circuit board side) ×: Pressure delamination is visible (a detached circuit is visible on the side of the adhesive tape, or a delamination of the circuit is visible on the side of the printed circuit board) (Lift wettability)

[0078] First, a circuit using the conductive composition obtained in each example was printed onto a polyimide film using a screen printer, so that after calcination the width was 1 mm, the length 10 cm, and the thickness 30 µm. The polyimide film with the printed circuit was then left at room temperature for 30 minutes and subsequently calcined with hot air at 140°C for 30 minutes to create a printed circuit board.

[0079] A low-temperature tin-bi solder was then applied to a thin silver film on the resulting printed circuit board and heated. The solder wettability was subsequently evaluated. Specifically, the contact angle of the solder on the silver film was measured using a θ / 2 method with a contact angle meter. A CONTACT-ANGLE METER FACE TYPE01 from Kyowa Interface Science Co., Ltd. was used as the contact angle meter. • Criteria ◯: Contact angle θ < 90° ×: Contact angle θ ≥ 90° (Assembly strength)

[0080] First, a circuit using the conductive composition obtained in each example was printed onto a polyimide film using a screen printer, so that after calcination the width was 1 mm, the length 10 cm, and the thickness 30 µm. The polyimide film with the printed circuit was then left at room temperature for 30 minutes and subsequently calcined with hot air at 140°C for 30 minutes to create a printed circuit board.

[0081] A 0 Ω resistor, size 3216, was then soldered onto an Ag thin film on the resulting circuit board using a low-temperature Sn-Bi solder. The shear strength of the resulting circuit was then measured using a bond tester (SERIES4000 from Nordson Dage). • Criteria ⊚: The shear strength is 50 N or more ◯: The shear strength is 20 N or more and less than 50 N ×: The shear strength is less than 20 N -: Shear strength cannot be measured

[0082] As shown in Tables 6 and 7, the printed circuit boards made from the conductive compositions of Examples 2-1 to 2-10 exhibit low conductor resistance and excellent adhesion to the substrate. Furthermore, the conductors of these examples demonstrate excellent solder wettability, assembly strength, and assembly properties.

[0083] In contrast, as shown in Tables 8 to 10, the specific resistance of the conductor is high or the adhesion of the conductor to the substrate is not excellent in the printed circuit boards made from the conductive compositions of comparison examples 2-1 to 2-13. In particular, because the conductive compositions of comparison examples 2-1 and 2-3 contain many synthetic resin components, the conductors made with these synthetic resin components exhibit insufficient solder wettability and assembly strength, and thus poorer assembly properties.

[0084] The entire contents of Japanese priority application No. 2017-179961 (filing date: 20 September 2017) and Japanese priority application No. 2018-114377 (filing date: 15 June 2018) are included herein by reference. Industrial applicability

[0085] According to the invention, a conductive composition with which a conductor can be obtained which has a specific resistance corresponding to that of raw silver and excellent adhesion to a substrate, and a printed circuit board using the conductive composition can be provided.

Claims

[1] Leading composition comprising: Silver nanoparticles with an average particle diameter of 350 nm to 600 nm, Silver particles with an average particle diameter that is larger than that of the silver nanoparticles, a thermosetting synthetic resin that has an oxirane ring in one molecule, a hardening agent, and a cellulose resin wherein the ratio of the thermosetting resin to the curing agent is 1:1 to 3:1 by mass, the specific resistance of a conductor formed by applying and calcining the conductive composition on a substrate is 5.0 × 10 -6 Ω · cm or less and the conductor does not detach from the substrate when an adhesive tape with an adhesive strength of 3.9 N / 10 mm to 39 N / 10 mm is pressed against the conductor and pulled off. [2] Conductive composition according to claim 1, wherein the thermosetting resin is selected from the group comprising a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a novolac type epoxy resin, a glycidylamine type epoxy resin and an aliphatic type epoxy resin. [3] Conductive composition according to claim 1 or 2, wherein the curing agent is a 5-membered heterocyclic aromatic compound containing nitrogen. [4] Conductive composition according to any one of claims 1 to 3, wherein the proportion of cellulose resin is 0.1% to 4% by mass in relation to the total conductive composition. [5] Conductive composition according to any one of claims 1 to 4, wherein the total proportion of the thermosetting resin and the curing agent is 0.1% to 6% by mass in relation to the total conductive composition. [6] Conductive composition according to any one of claims 1 to 5, wherein the total proportion of the thermosetting resin and the curing agent is 0.1% to 5% by mass in relation to the total conductive composition. [7] Conductive composition according to any one of claims 1 to 6, wherein the total proportion of the thermosetting resin and the curing agent is 0.1% to 2% by mass in relation to the total conductive composition. [8] Conductive composition according to any one of claims 1 to 7, wherein the average particle diameter of the silver particles is 1 µm to 5 µm. [9] Printed circuit board comprising: a conductor obtained from the conductive composition according to any one of claims 1 to 8.