JP5047864B2 - Conductive paste and cured film containing fine silver particles - Google Patents

Description

  The present invention relates to a thermosetting conductive paste using nano-order fine silver particles in combination and a cured film using the same.

  Conventionally, conductive pastes containing metals and resins have been widely used for electronic devices. In particular, among various metals, silver, which hardly causes an increase in resistance due to oxidation during heating, is widely used, and as such a conductive paste, a thermosetting resin, its curing agent, silver Those containing powder and solvent are widely used. This conductive paste containing a thermosetting resin is also called a thermosetting conductive paste, and is generally applied to a substrate and then heated at a temperature of 150 ° C. to 200 ° C. for several tens of seconds to several hours. It is hardened and electricity is conducted through the contact portion between the silver particles.

  In addition, a conductor pattern obtained by printing such a conductive paste by various methods such as screen printing and ink jet printing is generally required to have a low electric resistance value. Therefore, the silver powder contained in such a thermosetting conductive paste is required to have a large number of contact portions between the particles after thermosetting, and scaly silver powder taking into account this point is often used. Yes. Depending on the required printing controllability and the electrical resistance value of the conductor pattern, it is also possible to use a single powder with a spherical or agglomerated particle shape, or a combination of spherical, agglomerated or scaly silver powder in various patterns. ing.

  However, as described above, the thermosetting conductive paste heated at a temperature of 150 ° C. to 200 ° C. conducts through the contact portion between the particles, so there are places where the conduction is insufficient, and generally 400 The electrical resistance value is considered to be inferior when compared with a baked conductive paste that is conducted by heating at from 600C to 600C. Furthermore, if it is possible to provide a material that can be sintered as a paste at a low temperature and exhibits low resistance, even a substrate that is vulnerable to heat can be listed as a candidate for selection. .

  In order to satisfy such requirements, it has been studied to mix fine metal particles of nano order. When these fine metal particles are used in combination, nano-order fine metal particles sinter even at a temperature of about 150 ° C. to 200 ° C., which is the curing temperature of the thermosetting conductive paste. This is because it is considered that there is a possibility that the electrical resistance value can be decreased by increasing the particle indirect point.

  From this point of view, various studies have been made on methods for producing nano-order fine metal particles and mixing these nano-order metal particles with conventional thermosetting conductive pastes, and several reports have already been made. Yes.

  First, as a method for producing nano-order metal particles, a gas phase method and a liquid phase method are mainly known. For example, in Patent Document 1, silver ultrafine particles are prepared by a vapor phase method in a vacuum and mixed with an organic solvent, whereby the surfaces of the ultrafine particles are covered with the organic solvent and dispersed individually. It is disclosed that an independent dispersion of ultrafine silver particles can be obtained.

  Patent Document 2 discloses ultrafine particles obtained by a liquid phase method. This technique utilizes the fact that metal fine particles produced by reducing metal ions in the aqueous phase move from the aqueous phase to the more stable organic solvent phase. In other words, the presence of a small amount of protective colloid in an organic solvent in advance causes interphase transfer from the aqueous phase to the organic solvent layer, and the metal fine particles become stable colloid particles, thereby increasing the metal particles in the organic solvent phase. It is disclosed that it is obtained in concentration.

  Patent Document 3 also discloses a production method in a liquid phase. Here, when producing silver nanoparticles by reducing a silver salt in a solvent, silver halide that is insoluble as a silver salt (especially silver chloride or silver bromide) is used instead of the commonly used silver nitrate. Is used, and the reduction is carried out in the presence of a protective agent composed of a compound dissolved in a solvent and having a coordination property to silver. In this method, a monodispersed solution of silver nanoparticles coated and protected with a protective agent and dispersed in a solvent is obtained. A polar solvent is used as the solvent, and a thiol such as thiocholine bromide is used as the protective agent. Is preferred.

  Patent Document 4 also discloses a method for obtaining nano-order silver fine particles monodispersed in a polar solvent by using a liquid phase method. Here, it is disclosed that silver nitrate is used as a starting material for obtaining silver fine particles, and heptanoic acid is used as a protective agent.

Patent Document 5 discloses an example in which nano-sized fine metal particles are mixed with a conventional thermosetting conductive paste. More specifically, a spherical fine silver powder having a particle diameter of 20 nm or less coated with a dispersant having a molecular weight of 1500 to 30000 is mixed with scaly silver powder, whereby the printing characteristics are good and the film after thermosetting A thermosetting conductive paste that improves conductivity is disclosed.
JP 2001-35255 A JP 11-319538 A JP 2003253331 A US2007 / 0144305 A1 Japanese Patent No. 3858902

  There are various methods for producing nano-order fine metal particles as described in Patent Documents 1 to 4, but it is preferable to carry out the liquid phase method from the viewpoint of industrial mass productivity. Further, among the synthesis in the liquid phase, it is preferable that the synthesis can be performed in a polar solvent such as water, and the obtained particles can be easily dispersed in the polar solvent. According to the technique disclosed in Patent Document 3 or 4, such metal particles can be obtained, but there are many unstable portions in which the particle size of the microparticles obtained varies depending on the manufacturing conditions.

  Moreover, in patent document 5, it has succeeded in improving electrical conductivity by mixing the spherical minute silver particle whose particle diameter is 20 nm or less with the thermosetting electroconductive paste of scaly silver particle. However, since the spherical fine silver particles are coated with a polymer compound having a relatively large molecular weight, as the ratio of the spherical fine silver particles / scale-like silver particles increases, the coated polymer In general, high molecular weight compounds have a drawback that they are difficult to remove by heating, and it is preferable that the organic substance to be coated has a simple name structure and a short chain as much as possible. .

  At present, scaly silver particles are widely used as the main metal material of the thermosetting conductive paste. However, when further finer pitch of the conductor pattern is required, it is considered that fine line drawing of the conductor pattern becomes difficult at the time of printing with the conductive paste using the scaly silver particles. For this reason, it has been required to reduce the electrical resistance value when printing is performed also on granular silver particles and aggregated silver particles having relatively good printing controllability.

  The object of the present invention is to enable thermosetting that can improve the electric resistance value of a cured film regardless of the shape of silver particles as a main metal material when nano-order fine silver particles are mixed with a conventional thermosetting conductive paste. It is to provide a mold conductive paste.

  In the present specification, the fine silver particles refer to nano-order silver particles, and the silver particles have a particle size of sub-micron order or larger and have any one of scale-like, aggregated and spherical shapes. Refers to silver particles.

  As a result of intensive studies to achieve such an object, the present inventors have included the above object by including predetermined micro-order silver particles, predetermined nano-order fine silver particles, and a thermosetting resin. Has been found to be achieved, and the present invention has been completed.

In other words, thermosetting conductive paste of the present invention, silver particles having a particle size in the range of less than 50μm more than 0.1 [mu] m, Ri range near less than 100nm particle size 1nm or more, more than 6 straight chain carbon wherein the fine silver particles that have been coated with a fatty acid, to include a thermosetting resin.

  According to the present invention, the electrical resistance value of the formed cured film can be improved by including predetermined micro-order silver particles, predetermined nano-order fine silver particles, and a thermosetting resin.

  Hereinafter, the thermosetting conductive paste of the present invention will be described in detail. In the claims and in the present specification, “%” indicates mass percentage unless otherwise specified.

As described above, the thermosetting conductive paste of the present invention includes a silver particle having a particle diameter in the range of 0.1 μm or more and less than 50 μm, a fine silver particle having a particle diameter in the range of 1 nm or more and less than 100 nm, and thermosetting. Mold resin.
By using such a conductive paste containing fine silver particles, a silver network is easily constructed between silver particles having an arbitrary shape, and the conductivity is improved.

  When the particle diameter of the fine silver particles exceeds 100 nm, the fine silver particles are difficult to sinter at the time of thermosetting, so the electric resistance value of the cured film does not decrease. Moreover, when the particle diameter of the fine silver particles is less than 5 nm, aggregation of the fine silver particles cannot be prevented, and as a result, the electric resistance value of the cured film does not decrease. Therefore, the particle diameter of the fine silver particles used in the present invention is preferably 5 nm or more and less than 50 nm, and more preferably 10 nm or more and less than 30 nm.

  The fine silver particles are preferably coated with a straight chain fatty acid having 6 or less carbon atoms. With such a low molecular weight linear fatty acid, it is possible to simultaneously achieve dispersibility when mixed with a thermosetting conductive paste and ensure conductivity when a film is formed by thermosetting. Here, the linear fatty acid having 6 or less carbon atoms functions as a protective agent. This protective agent is effective in obtaining stable fine silver particles by adhering to the surface of fine silver particles and inhibiting the bonding between the particles. Also, relatively short straight chain fatty acids are preferred from the viewpoint of the curing temperature and conductivity of the coating film.

  The straight-chain fatty acid is not limited as long as it has 6 or less carbon atoms, but is preferably 3 or more, and more preferably 6. Typically, hexanoic acid can be used. When the number of carbon atoms is 7 or more, the reaction becomes unstable, and if mixed with a thermosetting conductive paste, the effects of the present invention may not be obtained.

  In the present invention, the total metal mass contained in the thermosetting conductive paste (total mass of silver particles and fine silver particles having one or more shapes selected from the group consisting of scales, aggregates, and spheres) Can be contained in an amount of 80 to 95% with respect to the mass of the thermosetting conductive paste. In addition, the mixing ratio of the fine silver particles in the present invention may be 0.001 to 99% with respect to the total metal mass, but is preferably 1 to 50%, more preferably 5 to 30%. . When the mixing ratio of the fine silver particles is less than 0.001% with respect to the total metal mass, the amount of the fine silver particles is too small to form a sufficient silver network by sintering. May not be obtained.

  With such a configuration, the resistivity of the cured film is low as compared with the conventional thermosetting conductive paste, and even if the proportion of the fine silver particles in the total metal mass in the thermosetting conductive paste is high, The characteristic that the electric resistance value of the cured film does not increase is obtained.

  The thermosetting conductive paste may contain a curing agent, a viscosity adjusting filler, and a solvent. Moreover, electroconductive substances other than silver may be contained, for example, gold, copper, zinc, aluminum, a conductive resin, etc. may be contained. In this sense, the total metal mass referred to in the present invention may be called not only the total mass of silver particles and fine silver particles but also the total mass of all conductive materials.

  Further, the silver particles are composed of single particles of scale-like, agglomerated, or spherical shapes, or particles formed of those shapes are mixed at an arbitrary ratio, and the above-mentioned arbitrary ratio is particularly There is no limit.

  Here, the scale-like silver particles refer to silver particles having an aspect ratio of 5 or more. Aggregation means a state in which smaller silver particles are solidified into one lump. The spherical shape means particles having a major axis / minor axis ratio of 2 or less. In any case, it is sufficient to read and judge an average value by observation with an electron microscope.

  The fine silver particles typically include a liquid preparation step for adjusting a raw material solution and a reducing solution, a temperature raising step for raising the temperature, a reaction step for adding the raw material solution to the reducing solution to advance the reaction, and a metal in the solution. It can be produced by carrying out an aging step for growing particles (particularly silver particles), a washing step for removing excess organic substances by repeated filtration, washing with water and dispersion, and a drying step for removing water in the liquid by drying.

  In the present invention, it is preferable to perform the reducing liquid preparation step, the silver reaction step, and the washing step as follows. The reducing liquid used in the reducing liquid preparation step includes water, aqueous ammonia, linear fatty acid (in particular, hexanoic acid), and a hydrazine hydrated aqueous solution. In the silver reaction step, an aqueous silver nitrate solution is added to the reducing solution and reacted with the reducing solution. In the washing step, the product obtained in the reaction step is washed with water.

  More specifically, ammonia water is used in the reducing liquid preparation step. This is because ammonia water acts as a stabilizer for dissolving acid in water.

  In the silver reaction step, the temperature in the reaction vessel is preferably raised from 40 ° C. to 80 ° C. for reaction. At this time, the aqueous silver nitrate solution added to the reaction vessel is more preferably kept at the same temperature as the reaction vessel. If the temperature in the reaction vessel is lower than 40 ° C., the degree of supersaturation of the metal increases and nucleation is promoted, so that the number of fine particles tends to increase. Above 80 ° C., nucleation is suppressed, but particle growth and particle aggregation tend to be promoted.

  In the silver reaction step, it is preferable to add the aqueous silver nitrate solution to be added all at once from the viewpoint of realizing a uniform reaction in the solution. If not added all at once, the inside of the solution becomes a heterogeneous system, and nucleation and particle aggregation occur simultaneously. As a result, nonuniform silver particles having a large particle size distribution may be obtained. Therefore, “added all at once” is particularly limited as long as the reaction factor such as the concentration or pH of the reducing agent or the protective agent does not substantially change depending on the addition timing of the aqueous silver nitrate solution. It is not a thing.

  Here, the said hydrazine hydrate should just be a thing which can reduce | restore a metal as a reducing agent. Reducing agent other than hydrazine hydrate, specifically hydrazine, alkali borohydride (NaBH4, etc.), lithium aluminum hydride (LiAlH4), ascorbic acid, primary amine, secondary amine, tertiary amine Etc. can also be used together.

  By mixing the fine silver particles of the present invention obtained by such a process with a thermosetting conductive paste, an effect of lowering the electric resistance value of the cured film is brought about. This effect does not change even if the proportion of the fine silver particles in the total metal mass in the thermosetting conductive paste increases.

  In the method for producing fine silver particles described above, it is preferable to use a reaction vessel having a shape and a structure capable of obtaining uniform stirring. This is because fine silver particles are obtained by a reduction reaction, but the size of the particles to be obtained is very small, and therefore the local concentration and pH distribution greatly affect the particle size distribution.

Next, the thermosetting conductive paste of the present invention is obtained, for example, by mixing the fine silver particles produced by the above-described fine silver particle production method with a conventional thermosetting conductive paste.
The “conventional thermosetting conductive paste” as used herein refers to silver particles, a solvent, a thermosetting resin, and one or more shapes selected from the group consisting of scales, aggregates, and spheres, and It refers to a thermosetting conductive paste made of the curing agent.

  In the mixing of the fine silver particles, there is no particular limitation on the mixing method, and it is possible to mix the fine silver particles and the silver particles in a dry powder state, or to mix the fine silver particles and the silver particles in an appropriate solvent. However, considering that the fine silver particles and the silver particles are more uniformly mixed, it is more preferable to mix the fine silver particles and the silver particles in an appropriate solvent.

  As a method for producing the thermosetting conductive paste, a metal component composed of one or more shapes selected from the group consisting of scales, aggregates, and spheres, and fine silver particles, a solvent, and thermosetting It is obtained by mixing a mold resin and its curing agent and kneading with a stirring defoaming machine, a rotary mill, a three roll or the like.

  Here, examples of the thermosetting resin include epoxy resins. Examples of the epoxy resin that can be used include a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, an alicyclic epoxy resin, an amine type epoxy resin, and an epoxy resin obtained by glycidyl esterification of dimer acid.

Examples of the curing agent include amine curing agents such as dicyandiamide and carboxylic acid hydrazide, urea curing agents such as 3- (3,4-dichlorophenyl) -1,1-dimethylurea, phthalic anhydride, and methyl nadic anhydride. Examples of the epoxy resin include acid anhydride-based curing agents such as acid, pyromellitic anhydride and hexahydrophthalic anhydride, and aromatic amine-based (amine adduct) curing agents such as diaminodiphenylmethane and diaminodiphenylsulfonic acid. The content combined with 5 to 20% of the mass of the thermosetting conductive paste.

  In addition, the said solvent can be suitably added for the viscosity adjustment of the thermosetting conductive paste of this invention, for example, use isopropyl alcohol, terpineol, 2-octanol, butyl carbitol acetate, etc. Can do.

  The thermosetting conductive paste of the present invention described above can be applied to a glass substrate or the like to form a cured film, but the conductivity of the cured film is also better than that of conventional products.

Examples will be described in detail below. In this embodiment, since silver particles and fine silver particles are used as the conductive material, the total metal mass is the total mass of the silver particles and the fine silver particles.
Example 1
(1) Production of particles A 24 L reactor was used as a reactor. In order to ensure the uniformity of stirring, baffle plates were arranged at equal intervals inside the wall surface. For stirring, a stirring rod provided with two turbine blades was installed at the center of the reaction vessel. The reaction vessel was equipped with a thermometer for monitoring the temperature. A nozzle was provided so that nitrogen could be supplied to the solution from below.

  First, 16851 g of water was put in the reaction tank, and nitrogen was flowed from the lower part of the reaction tank at a flow rate of 5000 mL / min for 600 seconds in order to remove residual oxygen. Then, it supplied with the flow volume of 5000 mL / min from the reaction tank upper part, and made the inside of a reaction tank nitrogen atmosphere.

  The rotating speed of the stirring bar was adjusted to 338 rpm. And temperature adjustment was performed so that the solution temperature in a reaction tank might be 60 degreeC.

  Aqueous ammonia (containing 30% as ammonia) (33.9 g) was added to the reaction vessel, and then stirred for 1 minute to make the solution uniform.

  Next, 218.3 g (corresponding to 1.98 equivalents of silver) of hexanoic acid (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added as a protective agent, and the mixture was stirred for 4 minutes to dissolve the protective agent. Thereafter, 114.5 g of a 50% hydrazine hydrate (Otsuka Chemical Co., Ltd.) aqueous solution was added as a reducing agent, and this was used as a reducing solution.

  A silver nitrate aqueous solution in which 162 g of silver nitrate crystals (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 438 g of water was prepared in another container, and this was used as a raw material liquid. The temperature of the aqueous silver nitrate solution was adjusted to 60 ° C., the same as the solution in the reaction vessel.

Thereafter, the raw material solution was added to the reducing solution at once and a reduction reaction was performed. Stirring was performed continuously and aged for 10 minutes in that state. Then, stirring was stopped and a fine silver particle lump was obtained through a washing process and a drying process. When the particles obtained at the end of the cleaning process were observed with a transmission electron microscope (TEM), metal nanoparticles having an average particle size of 14 nm and a relatively uniform particle size were obtained, and no particles of 100 nm or more were present. It was. Moreover, when the specific surface area by BET method was measured, it was 19.7 m < ² > / g and TAP density was 2.07 g / cm < ³ >.

(2) Preparation of thermosetting conductive paste 4.5% of the fine silver particles synthesized in Example 1 (5% with respect to the total metal mass), the average particle size is 0.70 μm, and the smallest particle of particle size distribution An epoxy resin (YD-171) in which the aggregated silver particles having a diameter of 0.1 μm or more are 90% of the total amount of the fine silver particles with respect to the thermosetting conductive paste, and dimer acid is glycidyl esterified. Toto Kasei Co., Ltd.) and amine adduct curing agent (PN-23 Ajinomoto) as the curing agent, 10% in total amount of epoxy resin and curing agent, and butyl carbitol acetate for viscosity adjustment and 3 defoamers Kneading was performed using a roll.

(3) Viscosity measurement of thermosetting conductive paste Viscosity (mPa · sec) of the thermosetting conductive paste prepared above was measured using Rheo Stress RS600 (HAAKE). The rotational speed of the rotor was measured under two conditions of 1 rpm and 10 rpm, the paste viscosity was evaluated by the viscosity at 1 rpm, and the thixotropic property was evaluated by the ratio (no unit) of the measured values at 1 rpm and 10 rpm.

(4) Application of thermosetting conductive paste The thermosetting conductive paste prepared above was applied onto a slide glass using an applicator.

(5) Thermal curing of coating film The coating film applied above was heated on a hot plate whose temperature was adjusted to 200 ° C. for 30 minutes to prepare a cured film.

(6) Measurement of film thickness and volume resistivity of cured film The volume resistivity (Ωcm) of the cured film prepared above was measured by Loresta (registered trademark).

(Comparative Example 1)
In this comparative example, fine silver particles were synthesized in the same manner as in Example 1 except that the hexanoic acid used as the protective agent in Example 1 was changed to PVA (polyvinyl alcohol) having a molecular weight of 8000 to 10,000. Using these fine particles, a thermosetting conductive paste was prepared in the same manner as in Example 1, and viscosity measurement, application of the thermosetting conductive paste, thermosetting of the coating film, film thickness and volume resistance of the cured film were performed. Rate measurements were taken.

(Examples 2 and 3)
The same operation as in Example 1 was carried out except that the amount of fine silver particles in Example 1 was 9 and 18% (10 and 20% with respect to the total metal mass). That is, Examples 2 and 3 are examples of the thermosetting conductive paste of the present invention, and the amount of fine silver particles is larger than that of Example 1.

(Comparative Example 2)
The same operation as in Examples 2 and 3 was performed except that the PVA-coated fine silver particles prepared in Comparative Example 1 were used instead of the fine silver particles in Examples 2 and 3. That is, Comparative Example 2 is a comparative example in which the amount of fine silver particles coated with a protective agent having a large molecular weight is larger than that of Comparative Example 1.

(Comparative Example 3)
The same operation as in Example 1 was performed except that the fine silver particles were not mixed. That is, Comparative Example 3 is a conventional thermosetting conductive paste that does not contain fine silver particles.

Table 1 shows the composition of each thermosetting conductive paste obtained in each example and the value of volume resistivity of the cured film.

  FIG. 1 shows the relationship between the amount of fine silver particles mixed and the volume resistivity of a cured film with respect to the total metal mass of Examples and Comparative Examples. The vertical axis represents volume resistivity (Ωcm), and the horizontal axis represents the amount of fine silver particles mixed (%) with respect to the total metal mass. In the figure, black squares are examples, white triangles are Comparative Examples 1 and 2, and black circles are Comparative Example 3.

  With reference to the white triangle comparative example, the volume resistivity increased about 10 times when the amount of fine silver particles mixed increased from 10% (Comparative Example 1) to 20% (Comparative Example 2). Comparative Example 3 was a cured film made of a paste containing no fine silver particles, but Comparative Example 2 was higher than the volume resistivity of Comparative Example 3.

  On the other hand, Examples 1-3 of the present invention maintained a low resistance value even when the amount of fine silver particles mixed was increased. That is, in the examples, it can be seen that the volume resistivity of the cured film hardly changes even when the amount of fine particles mixed is increased.

  On the contrary, in Comparative Examples 1 and 2, the volume resistivity of the cured film increased when the amount of fine silver particles mixed was increased. This is presumably because, when the amount of fine silver particles mixed is increased, if the coating molecular weight is large, the coating molecules intervene between the particles, thereby inhibiting the conductivity.

  FIG. 2 shows the relationship between the amount of fine silver particles mixed with the total metal mass and the viscosity of the paste. The vertical axis is the viscosity at 25 ° C. and the rotational speed of the rotor is 1 rpm, and the horizontal axis is the amount of fine silver particles mixed (%) with respect to the total metal mass. The examples and comparative examples are represented by black squares, white triangles and black circles as in the case of FIG.

  In both the examples and comparative examples, the viscosity tended to increase as the amount of fine silver particles mixed increased. However, in the examples, the dependence of the viscosity on the amount of fine silver particles mixed is larger.

  FIG. 3 shows the relationship between the amount of fine silver particles mixed with the total metal mass and the thixotropic property of the paste. The vertical axis is the ratio of the viscosity at 25 ° C. when the rotational speed of the rotor is 1 rpm and the viscosity at 10 rpm, and the horizontal axis is the amount of fine silver particles mixed (%) with respect to the total metal mass. The examples and comparative examples are represented by black squares, white triangles and black circles as in the case of FIG.

  Also in this case, as in the case of the viscosity in FIG. 2, the thixotropic property tends to increase as the mixing amount of the fine silver particles increases in both the example and the comparative example, and the thixotropic property with respect to the mixing amount of the fine silver particles in the example. The dependence of was great.

  From the above phenomenon, the thermosetting conductive paste of the present invention is covered with a dispersing agent having a small molecular weight, so that it is likely to interact with each other, and is likely to thicken in the paint state. On the other hand, since the interaction between the metal particles is easily exerted, it is considered that the volume resistivity does not increase even if the mixing amount of the fine silver particles is increased.

The present invention can be used not only for thermosetting conductive pastes but also for heat-fired conductive pastes.

It is a figure which shows the relationship between the fine particle mixing amount and volume resistivity of the Example and comparative example of this invention. It is a figure which shows the relationship of the viscosity at 25 degreeC and 1 rpm of the thermosetting conductive paste of the fine particle mixing amount of the Example and comparative example of this invention. It is a figure which shows the relationship of the thixotropic property (viscosity in 1 rpm / viscosity in 10 rpm) at the time of 25 degreeC of the fine particle mixing amount of the Example and comparative example of this invention at 25 degreeC.

Claims (7)

Silver particles having a particle diameter in the range of 0.1 μm or more and less than 50 μm;
Ri near range particle size of less than 100nm or 1 nm, and fine silver particles that have been coated with more than 6 straight chain fatty acid carbons,
A thermosetting conductive paste containing a thermosetting resin. The thermosetting conductive paste according to claim 1 , wherein the linear fatty acid is hexanoic acid. The ratio with respect to the total metal mass of the said fine silver particle is 0.001 to 50%, The thermosetting conductive paste described in any one of Claims 1-2 . The thermosetting conductive paste according to any one of claims 1 to 3 , wherein the silver particles have at least one shape selected from a scaly shape, an agglomerated shape, and a spherical shape. The thermosetting conductive paste according to any one of claims 1 to 4 , further comprising a curing agent. The fine silver particles are
A step of preparing a reducing solution containing water, aqueous ammonia, hexanoic acid and a hydrazine hydrated aqueous solution;
Adding and reacting an aqueous silver nitrate solution to the reducing solution;
The thermosetting conductive paste according to any one of claims 1 to 5 , which is a fine silver particle produced by a step of washing a product of the reaction step with water. A cured film using the thermosetting conductive paste according to any one of claims 1 to 6 .

Images