JP5547570B2 - Conductive paste - Google Patents

Description

  The present invention relates to a conductive paste, and more particularly to a conductive paste for forming a circuit or the like on a substrate.

  Conventionally, a thermosetting type in which metal particles such as silver particles are mixed with a binder resin and a solvent to form a circuit made of metal conductive film by drawing wiring on a substrate of an electronic device. A method is known in which a conductive paste is used to draw a wiring on a substrate, and the binder resin is cured by heating at a temperature of 150 to 200 ° C., thereby conducting electrical conduction at a contact portion between metal particles. In this method, since the wiring of the metal conductive film is formed by heating at a low temperature of 150 to 200 ° C., it is possible to use a substrate that is not so high in heat resistance, so that it is flexible like a polyimide (PI) substrate. A simple substrate can also be used.

  In recent years, with the miniaturization of electronic devices, it is desired to form finer wiring as wiring to be drawn on a substrate. However, in the method using the thermosetting conductive paste, since the heating is performed at a temperature of 150 to 200 ° C. lower than the melting point of the metal particles, the contact between the metal particles becomes insufficient and the electric resistance value becomes high. As a result, the conductivity may be inferior.

  In order to solve such a problem, as the metal component of the thermosetting conductive paste, the average particle size is less than 100 nm (silver fine particles or the like) together with metal particles (such as silver particles) having an average particle size of 0.1 μm or more. A method using metal fine particles (metal nanoparticles) has been proposed. Thus, by using metal nanoparticles together with metal particles as a metal component, sufficient contact between the metal particles is ensured to reduce the electrical resistance value, and even when forming a fine wiring, it has excellent conductivity. Wiring can be formed.

  For example, as a conductive paste having good conductivity and adhesion even when the circuit is miniaturized, silver particles (A) having an average particle size of 0.5 to 20 μm and spherical silver particles having an average primary particle size of 50 nm or less A silver powder containing (B) as a main component, a binder resin, and a solvent, and the mixing ratio of silver particles (A) and spherical silver particles (B) is (A) :( B) = 99.1. The volume resistivity of the cured film obtained by heating at 150 ° C. for 30 minutes in the range of 80:20, the blending ratio of silver powder and binder resin being silver powder: binder resin = 85: 15 to 95: 5. Has been proposed (see, for example, Patent Document 1).

  In addition, silver particles having a particle diameter in the range of 0.1 μm to less than 50 μm, fine silver particles having a particle diameter in the range of 1 nm to less than 100 nm, and a thermosetting resin, the silver particles and the fine silver particles A thermosetting conductive paste having a total amount of 80 to 95% by mass and having a volume resistivity of 63 μΩ · cm or more of a cured film obtained by heating at 200 ° C. for 60 minutes has been proposed (for example, Patent Documents). 2).

  In the conductive pastes proposed in these Patent Documents 1 and 2, the fluidity of the conductive paste is lowered, and the adhesion (cohesive force) between the resin and silver powder (silver particles and fine silver particles) is weakened. In order to prevent deterioration in adhesion and printability to the substrate, the total amount of silver powder (silver particles and fine silver particles) is 95% by mass or less.

Japanese Patent Laying-Open No. 2005-294254 (paragraph numbers 0006-0018) JP 2009-252507 A (paragraph numbers 0022-0026)

  In order to form the conductive film wiring using the conductive paste of Patent Document 1, it is necessary to heat at 150 ° C. for 30 minutes. The conductive paste of Patent Document 2 is used to form the conductive film wiring. In order to do so, it is necessary to heat at 200 ° C. for 60 minutes. However, if the wiring of the conductive film can be formed by heating at a lower temperature, the use of the conductive paste is expected to further expand.

  Moreover, as described above, the volume resistivity of the cured film obtained by heating at 150 ° C. for 30 minutes using the conductive paste of Patent Document 1 is about 20 μΩ · cm, and the conductive paste of Patent Document 2 is used. The volume resistivity of the cured film obtained by heating at 200 ° C. for 60 minutes using is a 63 μΩ · cm or more, and a conductive paste that can further reduce the volume resistivity is desired.

  On the other hand, in order to further reduce the volume resistivity of the conductive film wiring using the conductive paste, it is conceivable to increase the total amount of silver powder (silver particles and fine silver particles) in the conductive paste. As described above, in the conductive pastes proposed in Patent Documents 1 and 2, when the total amount of silver powder in the conductive paste is more than 95% by mass, the fluidity of the conductive paste decreases, and the resin and silver powder There is a problem in that the adhesion (cohesive force) becomes weak and the adhesion to the substrate and the printability are lowered.

  Therefore, in view of such a conventional problem, the present invention can form conductive film wiring even when heated at a lower temperature than the conventional conductive paste, and has a volume resistivity higher than that of the conventional conductive paste. An object of the present invention is to provide a conductive paste which can form a conductive film having a low thickness and has excellent adhesion to a substrate and printability.

  As a result of intensive studies to solve the above problems, the present inventors have found that silver particles containing a metal component, a binder resin or a binder resin and a curing agent, and a solvent, the metal component having an average particle size of 0.5 μm or more. If the dispersibility of the silver fine particles is improved by adding a dispersant or the like in the conductive paste consisting of silver fine particles having an average primary particle size of 10 to 200 nm, the metal component and the binder resin (or binder) in the conductive paste Even if the ratio of the metal component to the total amount of the resin and the curing agent is greater than 95% by mass, the adhesion to the substrate is reduced due to the decrease in the fluidity of the conductive paste and the decrease in the adhesion (cohesion) between the resin and the metal component. It has been found that deterioration of printability and printability can be prevented. Also, a conductive material comprising a metal component, a binder resin or a binder resin and a curing agent, and a solvent, the metal component comprising silver particles having an average particle size of 0.5 μm or more and silver fine particles having an average primary particle size of 10 to 200 nm. In the paste, the ratio of the metal component to the total amount of the metal component and the binder resin (or the binder resin and the curing agent) (hereinafter referred to as “F value”) is more than 95% by mass, so that the temperature is lower than that of the conventional conductive paste. It is possible to form a conductive film wiring even when heated by heating, to form a conductive film wiring having a volume resistivity lower than that of a conventional conductive paste, and to have excellent adhesion and printability to a substrate. The inventors have found that a conductive paste can be produced, and have completed the present invention.

  That is, the conductive paste according to the present invention includes a metal component, a binder resin or a binder resin and a curing agent, and a solvent, and the metal component has silver particles having an average particle size of 0.5 μm or more and an average primary particle size of 10 to 200 nm. The silver component is more than 95% by mass with respect to the total amount of the metal component and the binder resin or the binder resin and the curing agent.

  In this conductive paste, it is preferable to use a solvent to which a dispersant is added. Further, it is preferably a conductive paste having a volume resistivity of 10 μΩ · cm or less after the binder resin is cured by heating at 200 ° C. for 60 minutes. Moreover, it is preferable that the average particle diameter of a silver particle is 0.5-10 micrometers, and it is preferable that the addition amount of the silver fine particle in a metal component is 1-70 mass%. The silver fine particles are preferably coated with an organic compound. In this case, the organic compound is preferably a fatty acid, more preferably a carboxylic acid such as sorbic acid. The binder resin is preferably a phenol resin or an epoxy resin. In the case of an epoxy resin, the conductive paste preferably further contains a curing agent. The solvent is preferably a polar solvent.

  According to the present invention, a conductive film wiring can be formed even when heated at a lower temperature than a conventional conductive paste, and a conductive film wiring having a lower volume resistivity than a conventional conductive paste is formed. In addition, it is possible to manufacture a conductive paste that is excellent in adhesion to the substrate and printability.

It is a figure which shows the state in which there is no blur and blur in the wiring drawn on the board | substrate using the electrically conductive paste. It is a figure which shows the state which has a faint in the wiring drawn on the board | substrate using the electrically conductive paste. It is a figure which shows the state which has a blur in the wiring drawn on the board | substrate using the electrically conductive paste. It is a figure which shows the state in which the wiring drawn on the board | substrate using the electrically conductive paste is disconnected.

  The embodiment of the conductive paste according to the present invention includes a metal component, a binder resin or a binder resin and a curing agent, and a solvent, and the metal component has silver particles having an average particle size of 0.5 μm or more and an average primary particle size of 10 It consists of silver fine particles of ˜200 nm, and the ratio (F value) of the metal component to the total amount of the metal component and the binder resin (or binder resin and curing agent) is more than 95% by mass. In this conductive paste, it is preferable to use a solvent to which a dispersant is added. The volume resistivity after the conductive paste is heated at 200 ° C. for 60 minutes to cure the binder resin is preferably 10 μΩ · cm or less.

  As the silver fine particles, silver fine particles (silver nanoparticles) having an average primary particle diameter measured from a transmission electron micrograph of 10 to 200 nm, preferably 10 to 150 nm, and more preferably 10 to 100 nm are used. As silver fine particles, a plurality of silver fine particles having different average primary particle diameters may be mixed and used. By using silver fine particles with such a particle size, a conductive paste with good conductivity after thermosetting can be obtained even when heat-treated in a low temperature environment that does not affect the substrate with low heat resistance. Can do.

  Silver fine particles have a very high activity on the surface of the particles. If the surface of the particles is exposed, adjacent particles may sinter or may be violently oxidized in the air. In order to suppress such sintering and oxidation so that the particles can be stored independently in a stable state, it is known to coat the surface of the silver fine particles with an organic compound. However, if the molecular weight of the organic compound covering the surface of the silver fine particles is too large, the silver fine particles are difficult to decompose or evaporate even when heated slightly when used as a bonding material for silver particles in the conductive paste. On the other hand, if the molecular weight is too small, the silver fine particles are difficult to stably exist, which is inconvenient to handle. Therefore, the molecular weight of the organic compound covering the surface of the silver fine particles needs to be an appropriate molecular weight, and in order to sinter at a low temperature, it is necessary to use an organic compound having an appropriately short molecular chain. As such an organic compound, it is preferable to use a low-carbon fatty acid having 3 to 8 carbon atoms, and it is preferable to use a carboxylic acid such as acetic acid, lactic acid, hexanoic acid or sorbic acid as the fatty acid. When an unsaturated fatty acid is used as this fatty acid, it has at least one unsaturated bond in its structure, and the unsaturated bond may be either a double bond or a triple bond, and an aromatic ring You may have. In particular, if the organic compound that covers the surface of the silver fine particles is hexanoic acid that is a saturated fatty acid or sorbic acid that is an unsaturated fatty acid, the silver fine particles can be obtained in a stable powder state. Alternatively, silver fine particles whose surfaces are coated with different types of organic compounds may be used. For example, silver fine particles whose surfaces are coated with unsaturated fatty acids and silver fine particles whose surfaces are coated with saturated fatty acids may be mixed and used.

  As the silver particles of the metal component, silver particles having an average particle diameter of 0.5 μm or more are used. In order to form fine wiring with the conductive paste, even if the amount of silver fine particles filling the gaps between the silver particles is reduced, the silver particles are joined to each other when the silver fine particles are sintered to further increase the conductivity. It is preferable that the average particle diameter of the silver particles is 10 μm or less. In the case of spherical silver particles, the average particle size is preferably 0.5 to 1.0 μm, and more preferably 0.5 to 0.8 μm. In the case of flaky silver particles, the average particle size is preferably 0.5 to 5.0 μm, more preferably 0.5 to 3.5 μm.

  The addition amount of silver fine particles in the metal component is preferably 1 to 70% by mass, more preferably 5 to 70% by mass, and most preferably 20 to 70% by mass.

  The binder resin is added to the conductive paste in order to sufficiently secure the adhesion to the substrate and the strength and conductivity after thermosetting. As the binder resin, a phenol resin, an epoxy resin, a polyester resin, a polyurethane resin, an acrylic resin, a melamine resin, a polyimide resin, a polyamideimide resin, or the like can be used, and it is preferable to use a phenol resin or an epoxy resin. In addition, when using an epoxy resin, it is preferable to add a curing agent. As this curing agent, an amine curing agent, a urea curing agent, an aromatic (amine adduct) curing agent, or the like is used. be able to. The total amount of the binder resin and the curing agent is preferably 5% by mass or less, more preferably 4% by mass or less, with respect to the components excluding the solvent (metal component, binder resin and curing agent). % Is most preferred. When the total amount of the binder resin and the curing agent is more than 5% by mass, it is not preferable because the influence of the excess binder resin on the conductivity is increased. On the other hand, if the total amount of the binder resin and the curing agent is too small, the adhesion to the substrate and the strength after thermosetting cannot be ensured sufficiently, so the total amount of the binder resin and the curing agent is at least about 2% by mass. is necessary.

  As the solvent, a polar solvent is mainly used. This solvent is not only an organic or inorganic solvent used for paste viscosity adjustment or volatilization prevention, but also leveling agents, viscosity modifiers, rheology control agents, antifoaming agents, anti-sagging agents, etc. that improve paste properties The additive may be included.

  In addition, there is no problem if a solvent compatible with the binder resin is used, but it is preferable to use an organic solvent such as ester, ether, ketone, ether ester, alcohol, hydrocarbon, or amine. . In addition, since the conductive paste is generally used to form a circuit by printing, it is preferable to use a high boiling point solvent having low volatility during printing, such as terpineol, butyl carbitol acetate, or octanediol. More preferably, diols are used. A plurality of types of solvents may be used in combination. The amount of the solvent is preferably 30% by mass or less, and more preferably 20% by mass or less, based on the total amount of the binder resin and the metal component.

  In order to improve the dispersibility of the silver fine particles, it is preferable to add one or more dispersants to the solvent in the conductive paste. Any dispersing agent may be used as long as it has an affinity for the surface of the silver fine particles and also has an affinity for the solvent.

  Examples of dispersants having such properties include fatty acid salts (soap), α-sulfo fatty acid ester salts (MES), alkylbenzene sulfonates (ABS), linear alkylbenzene sulfonates (LAS), alkyl sulfates ( AS), alkyl ether sulfate (AES), low molecular weight anionic (anionic) compounds such as alkyl sulfate triethanol, fatty acid ethanolamide, polyoxyethylene alkyl ether (AE), polyoxyethylene alkyl phenyl ether ( APE), low molecular weight nonionic compounds such as sorbitol and sorbitan, low molecular weight cationic (cationic) compounds such as alkyltrimethylammonium salt, dialkyldimethylammonium chloride and alkylpyridinium chloride, and alkylcarboxyl Low molecular amphoteric compounds such as tin, sulfobetaine, lecithin, formalin condensate of naphthalene sulfonate, polystyrene sulfonate, polyacrylate, copolymer salt of vinyl compound and carboxylic acid monomer, carboxy Polymer aqueous dispersants such as methylcellulose and polyvinyl alcohol, polymer non-aqueous dispersants such as polyacrylic acid partial alkyl esters and polyalkylene polyamines, and polymer cationic dispersants such as polyethyleneimine and aminoalkyl methacrylate copolymers Etc.

  A commercially available dispersing agent can be used as said dispersing agent. For example, Viewlight LCA-H and LCA-25NH manufactured by Sanyo Kasei Co., Ltd., Floren DOPA-15B manufactured by Kyoeisha Chemical Co., Ltd., Solplus AX5 manufactured by Nippon Lubrizol Co., Ltd., Solsperse 9000, Sol Six 250, Fuka Addy Dives EFKA4008 manufactured by Ajinomoto Co., Ltd., Ajisper PA111 manufactured by Ajinomoto Fine Techno Co., Ltd., TEXAPHOR-UV21 manufactured by Cognics Japan Co., Ltd. Neos FTX-207S and Footage 212P, Toagosei Co., Ltd. AS-1100, Kao Co., Ltd. Kaosela 2000, KDH-154, MX 2045L, Homogenol L-18, Rheodor SP-010V, Epan U103 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Cyanol DC902B, Neugen EA-167, Prisurf A219B, MegaFuck F-477 manufactured by DIC Corporation, Nissin Chemical Industry Commercially available dispersants such as Silface SAG503A and Dinol 604 manufactured by Sanyo Co., Ltd., SN Spurs 2180 and SN Leveler S-906 manufactured by Sannopco, and S-386 manufactured by AGC Seimi Chemical Co., Ltd. can be used.

  The addition amount of the dispersant is preferably 5% by mass or less, more preferably 3% by mass or less, and most preferably 2% by mass or less based on the metal component. When the amount of the dispersant added is more than 5% by mass, it is not preferable because the dispersant cannot be sufficiently removed during heating and the influence on the conductivity after thermosetting becomes large. On the other hand, if the amount of the dispersant added is too small, the silver fine particles will aggregate and the dispersion in the paste will not be complete, making it difficult for the silver fine particles to exist in the gaps between the silver particles, and heat curing. Since the volume resistivity later increases, it is not appropriate. Therefore, it is preferable to add at least about 0.5% by mass of the dispersant.

  Further, in order to disperse the metal component in the binder resin and the solvent, an appropriate mechanical dispersion treatment may be performed. In this mechanical dispersion treatment, ultrasonic dispersion, disperser, three-roll mill, ball mill, bead mill, twin-screw kneader, self-revolving stirrer, etc. are used alone or in combination under the condition that there is no significant modification of particles. Can be used.

  When silver fine particles or silver particles are coated with an organic compound, the weight of the silver fine particles or silver particles (silver fine particles coated with the organic compound or the weight of silver in the silver particles) is covered with the organic compound. It is obtained by multiplying the weight of the silver fine particles or silver particles (silver powder) by a value (coefficient) indicating the ratio of silver in the silver fine particles or silver particles coated with the organic compound. These coefficients indicate that when the silver fine particles or silver particles coated with the organic compound are heated in the atmosphere at 500 ° C., the weight of the organic compound is reduced and finally the silver fine particles or silver particles not coated with the organic compound As a result, the weight after heating 10 g of silver fine particles or silver particles (silver powder) coated with an organic compound at 500 ° C. until no weight loss occurs in the air is measured. By dividing, it is obtained as the weight of silver fine particles or silver particles per gram of silver fine particles or silver particles coated with an organic compound.

  Further, when the binder resin contains other than the solid content, the weight of the binder resin is the weight of the solid content in the binder resin, and the weight of the binder resin including the solid content and the other includes the solid content and the other. It is obtained by multiplying the value (coefficient) indicating the ratio of the solid content in the binder resin to be included.

  Hereinafter, the Example of the electrically conductive paste by this invention is described in detail.

[Example 1]
16.7 g of terpineol (isomer mixture) as an organic solvent, 1.67 g of epoxy resin (828XA manufactured by Japan Epoxy Resin Co., Ltd., coefficient 1.0) as a binder resin, and tertiary amine as a curing agent 0.33 g (MY-24 manufactured by Ajinomoto Fine Techno Co., Ltd.) and 0.20 g dispersant (polymer pigment dispersant Ajisper PA111 manufactured by Ajinomoto Fine Techno Co., Ltd.) were dissolved. 49.5 g of silver fine particles (coefficient 0.969) having an average primary particle diameter of 14 nm coated with hexanoic acid (straight fatty acid having 6 carbon atoms) as an organic compound was added to the solution thus obtained (47. 97 g) and stirring for 10 minutes to mix, and then adding 49.5 g (49.31 g as silver) of flaky silver particles having an average particle size of 2.8 μm (manufactured by DOWA Electronics, coefficient 0.9962) The mixture was further stirred for 10 minutes. After confirming that this solution had no color unevenness or lump of powder, this solution was passed through a three-roll mill and kneaded and defoamed to produce a conductive paste. The F value of this conductive paste is 99.99.

  Evaluation of the printability and adhesion of the wiring in which the wiring was drawn using the conductive paste thus produced was performed as follows, and the volume resistivity of the wiring was calculated as follows. In addition, the measurement of the average primary particle diameter of the silver fine particles used for preparation of the conductive paste and the average particle diameter of the silver particles, and the calculation of the silver content in the silver fine particles coated with the organic compound were performed as follows. .

(Measurement of average primary particle size of silver fine particles)
The average primary particle diameter of the silver fine particles was measured as follows based on a transmission electron micrograph (TEM image).

  First, 2% by mass of silver fine particles were added to a mixed solution of 96% by mass of cyclohexane and 2% by mass of oleic acid, and dispersed by ultrasonic waves. The dispersion solution was dropped on a Cu microgrid with a support film and dried to prepare a sample for TEM measurement. Using the transmission electron microscope (JEM-100CXMark-II type, manufactured by JEOL Ltd.) and accelerating voltage of 100 kV, an image obtained by observing silver fine particles in a bright field is magnified. Taken at 300,000 times.

  Based on the 300,000-fold TEM image obtained in this way, the average primary particle diameter of the silver fine particles was measured using image analysis software (A image-kun (registered trademark) manufactured by Asahi Kasei Engineering Co., Ltd.). . This image analysis software identifies individual particles by color shading. For a 300,000-fold TEM image, the “particle brightness” is “dark” and the “noise removal filter” is “present”. The average primary particle size was measured by performing circular particle analysis under the condition that the “circular threshold” was “20” and the “overlapping degree” was “50”. In addition, when there were many condensed particles and irregular shaped particles in the TEM image, it was determined that measurement was impossible.

(Calculation of silver content in silver fine particles coated with organic compounds)
The silver content in the silver fine particles coated with the organic compound was measured by weighing 0.5 g or more of the sample (silver fine particles coated with the organic compound) in an ash measuring ashtray, and a muffle furnace (FO310 manufactured by Yamato Scientific Co., Ltd.). The temperature is raised to 700 ° C. at a rate of about 10 ° C./min to remove the organic compound present on the surface of the silver fine particles, and then the ashtray is removed when the temperature in the furnace becomes 500 ° C. or lower by natural cooling. The sample was taken out, cooled to room temperature in a desiccator, and calculated by comparing the weight of the sample after cooling with the weight before heat treatment.

(Measurement of average particle diameter of silver particles)
The average particle size of the silver particles was measured based on the laser diffraction method as follows. That is, 0.3 g of a silver particle sample was put in 50 mL of isopropyl alcohol, dispersed for 5 minutes with an ultrasonic cleaner with an output of 50 W, and then laser diffraction was performed by a microtrack particle size distribution measuring device (Honeywell-Nikkiso 9320-X100). The value of D ₅₀ (cumulative 50% by mass particle size) when measured by the method was defined as the average particle size.

(Evaluation of printability of wiring)
Wiring by a screen printer (MT-320T manufactured by Microtech Co., Ltd.) was drawn using the produced conductive paste. In this wiring drawing, a wiring screen plate made of stainless steel (250 mesh, emulsion thickness 10 μm, manufactured by Sonocom Co., Ltd.) was used, wiring with a line width of 300 μm and a line length of 42 mm, and wiring with a line width of 80 μm and a line length of 20 mm. Drawing on a glass substrate and evaluating the printability of the wiring.

  In the evaluation of the printability of the wiring, the wiring drawn on the substrate is enlarged with a digital microscope (VHX-900 manufactured by Keyence Corporation), and the printability of the wiring without blurring or blurring is obtained as shown in FIG. 1A. Evaluated as good, evaluated the printability of the wiring that is not disconnected but blurred as shown in FIG. 1B, and the wiring that is not disconnected but blurred as shown in FIG. As shown in 1D, the printability of the disconnected wiring was evaluated as poor. As a result, in this example, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability.

(Evaluation of wiring adhesion)
Using the produced conductive paste, a substrate on which a wiring having a line width of 300 μm was drawn in the same manner as described above was subjected to an oven (DKM400 manufactured by Yamato Scientific Co., Ltd.) in the atmosphere at 200 ° C. for 30 minutes and 60 minutes, respectively. A sample was prepared by heating, and the adhesion of the wiring was evaluated.

  In this wiring adhesion evaluation, a cellophane tape (made by Nichiban Co., Ltd.) with a width of 24 mm is attached to the wiring formed on the substrate, and after applying a load of about 5 kg, bubbles between the wiring and the cellophane tape are formed. By rubbing the weight so that it disappears, the bubbles are removed and the cellophane tape and the substrate are brought into close contact with each other. Then, the substrate is fixed and the cellophane tape is lifted, taking care that the angle between the substrate and the tape is about 90 degrees. Peel off at a speed of about 0.6 seconds, evaluate that the adhesion is good when there is no wiring peeling on the tape, and if only a part of the edge is peeling, the adhesion is It was evaluated that it was not good, and it was evaluated that the adhesion was poor when it was disconnected and peeled so that the line resistance could not be measured. As a result, in this example, the adhesion of the wiring was good.

(Calculation of volume resistivity of wiring)
Using the produced conductive paste, a substrate on which wiring having a line width of 300 μm was drawn in the same manner as described above was subjected to an oven (DKM400 manufactured by Yamato Scientific Co., Ltd.) in the atmosphere at 120 ° C. for 10 minutes and 60 minutes, respectively. Samples heated for 10 minutes and samples heated at 200 ° C. for 10 minutes and 60 minutes, respectively, were prepared, and the volume resistivity of the wiring was calculated using these samples.

  For the calculation of the volume resistivity of the wiring, the wiring resistance of the wiring formed on the substrate is a digital multimeter (Miliohm Hitester manufactured by Hioki Electric Co., Ltd.), and the width of the wiring is a digital microscope (VHX manufactured by Keyence Corporation). 900), and measuring the thickness of the wiring with a surface roughness meter (Surfcom 1500D manufactured by Tokyo Seimitsu Co., Ltd.).

  As a result, the sample heated at 120 ° C. for 10 minutes has a wiring thickness of 9.1 μm and a volume resistivity of 82.7 μΩ · cm, and exhibits conductivity even when heated at such a low temperature for a short time. I understood. In the sample heated at 120 ° C. for 60 minutes, the wiring had a thickness of 9.7 μm and a volume resistivity of 89.9 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the wiring thickness was 10.1 μm and the volume resistivity was 26.2 μΩ · cm. Further, in the sample heated at 200 ° C. for 60 minutes, the thickness of the wiring was 10.2 μm and the volume resistivity was 7.0 μΩ · cm, and a highly conductive wiring was obtained.

[Example 2]
A conductive paste was produced in the same manner as in Example 1 except that the amount of the organic solvent was 16.4 g and the amount of the dispersant was 0.48 g. The F value of this conductive paste is 99.99.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  In addition, the sample heated at 120 ° C. for 10 minutes has a wiring thickness of 12.3 μm and a volume resistivity of 119.1 μΩ · cm. Even if it is heated for a short time at such a low temperature, it exhibits conductivity. all right. In the sample heated at 120 ° C. for 60 minutes, the wiring had a thickness of 9.8 μm and a volume resistivity of 86.4 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the wiring thickness was 8.0 μm and the volume resistivity was 14.2 μΩ · cm. In the sample heated at 200 ° C. for 60 minutes, the wiring had a thickness of 9.3 μm and a volume resistivity of 6.1 μΩ · cm, and a highly conductive wiring was obtained.

[Example 3]
A conductive paste was produced in the same manner as in Example 1 except that the amount of the organic solvent was 11.8 g and the amount of the dispersant was 0.96 g. The F value of this conductive paste is 99.99.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  In addition, the sample heated at 120 ° C. for 10 minutes has a wiring thickness of 13.3 μm and a volume resistivity of 129.8 μΩ · cm, and even when heated at such a low temperature for a short time, it exhibits conductivity. all right. In the sample heated at 120 ° C. for 60 minutes, the wiring had a thickness of 12.4 μm and a volume resistivity of 93.1 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the wiring thickness was 12.0 μm and the volume resistivity was 46.0 μΩ · cm. In the sample heated at 200 ° C. for 60 minutes, the thickness of the wiring was 11.5 μm and the volume resistivity was 6.8 μΩ · cm, and a highly conductive wiring was obtained.

[Example 4]
To 1.2 g of terpineol as an organic solvent, 1.3 g (solid content 1.008 g) of a phenol resin (PL4348, coefficient 0.775 manufactured by Japan Epoxy Resin Co., Ltd.) as a binder resin and a dispersant (Ajinomoto Fine) 0.20 g of a polymer pigment dispersant Ajisper PA111) manufactured by Techno Co., Ltd. was dissolved. 10.0 g of silver fine particles having an average primary particle diameter of 61 nm (9.86 g as silver) coated with sorbic acid (unsaturated fatty acid having 6 carbon atoms) as an organic compound is added to the solution thus obtained. After mixing by hand stirring for a minute, 10.0 g (9.96 g as silver) of flaky silver particles (DOWA Electronics) having an average particle size of 2.8 μm was added, and the mixture was further stirred for 10 minutes. After confirming that this solution had no color unevenness or lump of powder, this solution was passed through a three-roll mill and kneaded and defoamed to produce a conductive paste. The F value of this conductive paste is 95.16.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  In addition, the sample heated at 120 ° C. for 10 minutes has a wiring thickness of 15.0 μm and a volume resistivity of 185.9 μΩ · cm, and even when heated at such a low temperature for a short time, it exhibits conductivity. all right. In the sample heated at 120 ° C. for 60 minutes, the wiring had a thickness of 15.3 μm and a volume resistivity of 170.8 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the wiring thickness was 12.8 μm and the volume resistivity was 106.1 μΩ · cm. In addition, in the sample heated at 200 ° C. for 60 minutes, the wiring thickness was 14.3 μm and the volume resistivity was 6.4 μΩ · cm, and a highly conductive wiring was obtained.

[Example 5]
Average primary particle diameter of 3.7 g of organic solvent, 0.5 g of phenol resin (solid content 0.4 g) and coated with sorbic acid (unsaturated fatty acid having 6 carbon atoms) as an organic compound Except for using silver fine particles 10.0 g (9.69 g as silver) having an average primary particle diameter of 14 nm coated with hexanoic acid (straight fatty acid having 6 carbon atoms) as an organic compound instead of 61 nm silver fine particles, A conductive paste was produced in the same manner as in Example 4. The F value of this conductive paste is 99.99.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  In addition, the sample heated at 120 ° C. for 10 minutes has a wiring thickness of 11.9 μm and a volume resistivity of 103.0 μΩ · cm, and even when heated at such a low temperature for a short time, it exhibits conductivity. all right. In the sample heated at 120 ° C. for 60 minutes, the wiring had a thickness of 9.7 μm and a volume resistivity of 95.8 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the wiring thickness was 11.0 μm and the volume resistivity was 20.1 μΩ · cm. In the sample heated at 200 ° C. for 60 minutes, the wiring had a thickness of 9.8 μm and a volume resistivity of 4.9 μΩ · cm, and a highly conductive wiring was obtained.

[Comparative Example 1]
A conductive paste was produced in the same manner as in Example 4 except that the amount of the organic solvent was 0.3 g and the amount of the phenol resin was 2.2 g (solid content: 1.7 g). The F value of this conductive paste is 91.98.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  However, in the sample heated at 120 ° C. for 10 minutes, the wiring thickness is very high at 15.3 μm and the volume resistivity is 1110.1 μΩ · cm. Even in the sample heated at 120 ° C. for 60 minutes, the wiring thickness is 14. The volume resistivity at 3 μm was very high at 854.9 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the wiring thickness was as high as 15.5 μm and the volume resistivity was 294.3 μΩ · cm, and in the sample heated at 200 ° C. for 60 minutes, the wiring thickness was 13.5 μm. The volume resistivity was 9.4 μΩ · cm.

[Comparative Example 2]
The amount of organic solvent is 5.7 g, the amount of epoxy resin is 6.67 g, the amount of curing agent is 1.33 g, the amount of dispersant is 0.23 g, the amount of silver fine particles is 46.5 g (45.06 g as silver) ), A conductive paste was produced in the same manner as in Example 1 except that the amount of silver particles was changed to 46.5 g (46.32 g as silver). The F value of this conductive paste is 91.95.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  However, the sample heated at 120 ° C. for 10 minutes has a very high wiring resistivity of 12.2 μm and a volume resistivity of 956.5 μΩ · cm, and the sample heated at 120 ° C. for 60 minutes has a wiring thickness of 13. The volume resistivity at 5 μm was very high at 774.1 μΩ · cm.

  On the other hand, the sample heated at 200 ° C. for 10 minutes has a very high wiring resistivity of 12.5 μm and a volume resistivity of 1721.8 μΩ · cm, and the sample heated at 200 ° C. for 60 minutes has a wiring thickness of 10. The volume resistivity was as high as 408.9 μΩ · cm at 9 μm.

[Comparative Example 3]
A conductive paste was produced in the same manner as in Comparative Example 2 except that the amount of the organic solvent was 9.2 g and the amount of the dispersant was 0.45 g. The F value of this conductive paste is 91.95.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  However, the sample heated at 120 ° C. for 10 minutes has a very high wiring resistivity of 13.9 μm and a volume resistivity of 1870.7 μΩ · cm, and the sample heated at 120 ° C. for 60 minutes has a wiring thickness of 12. The volume resistivity at 4 μm was very high at 722.7 μΩ · cm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the thickness of the wiring was 13.2 μm and the volume resistivity was very high as 1743.6 μΩ · cm, and even in the sample heated at 200 ° C. for 60 minutes, the wiring thickness was 11. The volume resistivity at 5 μm was as high as 662.3 μΩ · cm.

[Comparative Example 4]
A conductive paste was prepared in the same manner as in Comparative Example 2 except that the amount of the organic solvent was 5.0 g and the amount of the dispersant was 0.90 g. The F value of this conductive paste is 91.95.

  Using the conductive paste thus prepared, the printability and adhesion of the wiring on which the wiring was drawn were evaluated and the volume resistivity of the wiring was calculated by the same method as in Example 1.

  As a result, both the wiring with a line width of 300 μm and the wiring with a line width of 80 μm had good printability and good adhesion of the wiring.

  However, the sample heated at 120 ° C. for 10 minutes has a very high wiring thickness of 13.4 μm and a volume resistivity of 1245.2 μΩ · cm, and the sample heated at 120 ° C. for 60 minutes has a wiring thickness of 14.4 μm. The volume resistivity was as high as 624.3 μΩ · cm at 5 μm.

  On the other hand, in the sample heated at 200 ° C. for 10 minutes, the thickness of the wiring was 14.3 μm and the volume resistivity was as high as 1427.4 μΩ · cm. Even in the sample heated at 200 ° C. for 60 minutes, the wiring thickness was 12. The volume resistivity was as high as 638.2 μΩ · cm at 1 μm.

  Table 1 shows the manufacturing conditions of the conductive pastes of Examples and Comparative Examples, and Table 2 shows the thickness and volume resistivity of wirings formed using these conductive pastes.

  As shown in Table 1 and Table 2, in Examples 1 to 5, silver particles containing a metal component, a binder resin or a binder resin and a curing agent, and a solvent, the metal component having an average particle size of 0.5 μm or more In a conductive paste composed of silver fine particles having an average primary particle size of 10 to 200 nm, it can be heated at a lower temperature (120 ° C.) than a conventional conductive paste by adding a dispersant and making the F value greater than 95. The conductive film wiring can be formed, and the conductive film can be formed with a very good conductive film having a volume resistivity lower than that of the conventional conductive paste (10 μΩ · cm or less). A conductive paste excellent in adhesiveness and printability with respect to can be obtained.

  The conductive paste according to the present invention can form conductive film wiring even when heated at a lower temperature than the conventional conductive paste, and has a lower volume resistivity than the conventional conductive paste and very good conductivity. Can be formed, and a conductive paste having excellent adhesion and printability to a substrate can be obtained. Therefore, it can be used for forming a fine circuit of a small electronic device, an electromagnetic wave shield, and the like. it can.

Claims (12)

Silver particles having a metal component, a binder resin or a binder resin and a curing agent, and a solvent to which a dispersant is added , wherein the metal component has an average particle size of 0.5 μm or more, and silver fine particles having an average primary particle size of 10 to 200 nm A conductive paste comprising a metal component and a binder resin or a binder resin or a binder resin and a curing agent, wherein the metal component is more than 95% by mass relative to the total amount. A metal component, a binder resin or a binder resin and a curing agent, and a solvent, wherein the metal component is composed of silver particles having an average particle diameter of 0.5 μm or more and silver fine particles having an average primary particle diameter of 10 to 200 nm. A conductive paste , characterized in that the metal component is coated with an organic compound and the metal component is more than 95% by mass relative to the total amount of the metal component and the binder resin or the binder resin and the curing agent . The conductive paste according to claim 2 , wherein the organic compound is a fatty acid. The conductive paste according to claim 2 , wherein the organic compound is a carboxylic acid. The conductive paste according to claim 2 , wherein the organic compound is sorbic acid. The conductive paste according to claim 2 , wherein the solvent is a solvent to which a dispersant is added. 7. The conductive paste according to claim 1, wherein the conductive paste has a volume resistivity of 10 μΩ · cm or less after the binder resin is cured by heating at 200 ° C. for 60 minutes . The conductive paste described in 1. Wherein the average particle diameter of the silver particles is 0.5 to 10 [mu] m, a conductive paste according to any one of claims 1 to 7. The conductive paste according to any one of claims 1 to 8 , wherein an addition amount of the silver fine particles in the metal component is 1 to 70% by mass. The conductive paste according to claim 1, wherein the binder resin is a phenol resin. The conductive paste according to claim 1, wherein the binder resin is an epoxy resin, and the conductive paste further contains a curing agent. The conductive paste according to claim 1, wherein the solvent is a polar solvent.

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