WO2024043328A1 - Electroconductive paste, electrode, electronic component, and electronic appliance - Google Patents

Abstract

An electroconductive paste comprising (A) electroconductive particles and (B) a binder resin, wherein the electroconductive particles (A) include surface-treated metal particles, the surface-treated metal particles comprising metal particles and a surface treatment layer disposed on at least some of the surfaces of the metal particles, the surface treatment layer including a zinc compound. The electroconductive paste has high sulfurization resistance and can form relatively inexpensive electrodes.

Description

Conductive paste, electrodes, electronic components and electronic equipment

The present invention relates to a conductive paste used for forming electrodes of electronic components, for example. The present invention also relates to an electrode formed using the conductive paste, and an electronic component such as a chip resistor having the electrode.

A conductive paste containing silver powder (silver particles) is used to form the electrodes of a chip resistor, which is one of the electronic components. FIG. 1 shows an example of a cross-sectional structure of a chip resistor 100. The chip resistor 100 has a rectangular alumina substrate 102, and a resistor 104 and an extraction electrode 106 for extracting electricity from the resistor 104 are formed on the upper surface of the alumina substrate 102. Furthermore, a lower surface electrode 108 is formed on the lower surface of the alumina substrate 102 for mounting the chip resistor 100 on the substrate. Furthermore, a connection electrode 110 for connecting the extraction electrode 106 and the lower surface electrode 108 is formed on the end surface of the alumina substrate 102. The extraction electrode 106 and the lower surface electrode 108 are each formed by applying a conductive paste to the upper and lower surfaces of the alumina substrate 102 by printing and then firing the paste. Generally, a nickel plating film 112 and a tin plating film 114 are formed on the extraction electrode 106, the bottom electrode 108, and the connection electrode 110.

As a conductive paste used for forming electrodes, Patent Document 1 discloses a paste for a top electrode of a chip resistor, which is made by dispersing conductive powder, glass frit, and an inorganic binder in an organic vehicle.

Further, Patent Document 2 discloses that the conductive particles contain (A) surface-treated metal particles containing Ag and Sn, (C) glass frit, and (B) binder resin, and (A) the weight of Sn in the conductive particles. Conductive pastes are disclosed in which the proportion is less than 10% by weight.

Japanese Patent Application Publication No. 7-335402 International Publication No. 2021/145269

Large amounts of sulfur oxides are emitted into the atmosphere due to the combustion of fossil fuels in gasoline vehicles and thermal power plants. Furthermore, in sewage treatment plants, garbage treatment plants, and the like, sulfur is reduced by anaerobic bacteria and hydrogen sulfide is generated. Therefore, components containing sulfur, such as sulfur oxides and hydrogen sulfide, exist in the atmosphere.

When components containing sulfur in the atmosphere reach the surface of metals such as silver, the sulfur components adhere to the surface of metals such as silver and react with the metals such as silver to form metal sulfides such as silver sulfide. For example, similar reactions occur in electrodes made mainly of silver, such as those of chip resistors, so that metals such as silver inside the electrodes may turn into metal sulfides such as silver sulfide. If metal sulfides such as silver sulfide are generated inside the electrode, the electrode may break. Therefore, devices such as chip resistors that have electrodes made of metal such as silver may malfunction. This phenomenon is called disconnection due to sulfidation. Disconnection due to sulfurization may also occur in electrodes made of copper, indium, aluminum, or alloys containing at least one of these in addition to silver.

Improving conductivity is one way to improve the performance of electrodes, but increasing the density of metal particles in order to improve conductivity increases the degree of sulfidation reaction, so it is necessary to reduce the conductive paste. Even if it is made resistive, it is required to be able to suppress disconnection due to sulfurization. In order to suppress wire breakage due to sulfidation, electrodes whose main material is metal such as silver used in devices such as chip resistors need to have high sulfidation resistance.

It has been proposed to add palladium alone or a predetermined amount (for example, about 20% by weight) of palladium as conductive particles in a conductive paste to form an electrode with high sulfidation resistance. However, since the price of palladium is high, there is a problem in that the cost of the conductive paste increases due to palladium alone or the addition of palladium, which increases the cost of the electrode.

Therefore, an object of the present invention is to provide a conductive paste that has high sulfidation resistance and can form a relatively low-cost electrode.

In order to solve the above problems, the present invention has the following configuration.

(Configuration 1)
Configuration 1 is a conductive paste containing (A) conductive particles and (B) binder resin,
(A) the conductive particles include surface-treated metal particles,
The surface-treated metal particles include metal particles and a surface treatment layer disposed on at least a portion of the surface of the metal particles,
The surface treatment layer is a conductive paste containing a zinc compound.

(Configuration 2)
Configuration 2 is the conductive paste of Configuration 1, in which the surface-treated metal particles have a zinc content of 10 to 1000 ppm.

(Configuration 3)
Structure 3 is the conductive paste according to Structure 1 or 2, wherein the surface treatment layer further contains an organic substance.

(Configuration 4)
Configuration 4 is the conductive paste of any one of Configurations 1 to 3, in which the metal particles contain 50% by weight or more of silver.

(Configuration 5)
Configuration 5 is the conductive paste of any of Configurations 1 to 4, in which the conductive particles (A) have an average particle diameter (D50) of 0.5 to 10 μm.

(Configuration 6)
Configuration 6 is the conductive paste of any of Configurations 1 to 5, wherein the content of the binder resin (B) is 0.1 to 30 parts by weight based on 100 parts by weight of the (A) conductive particles. be.

(Configuration 7)
Configuration 7 is the conductive paste according to any one of Configurations 1 to 6, wherein the conductive paste further contains (C) glass frit.

(Configuration 8)
Configuration 8 is the conductive paste of Configuration 7, in which the glass frit (C) contains ZnO.

(Configuration 9)
Configuration 9 is the conductive paste of Configuration 7 or 8, wherein the content of the (C) glass frit in the conductive paste is 0.05 to 10 parts by weight based on 100 parts by weight of the (A) conductive particles. It is.

(Configuration 10)
Structure 10 is an electrode obtained by firing or heat-treating the conductive paste of any of Structures 1 to 9.

(Configuration 11)
Configuration 11 is the electrode of Configuration 10, wherein the electrode contains 0.1 to 10% by weight of zinc.

(Configuration 12)
Configuration 12 is an electronic component or electronic device that includes the electrode of configuration 10 or 11.

According to the present invention, it is possible to provide a conductive paste that has high sulfidation resistance and can form a relatively low-cost electrode.

FIG. 2 is a schematic diagram showing an example of a cross-sectional structure of a chip resistor. It is a schematic diagram which shows the shape of the test piece for the sulfidation resistance test of an Example and a comparative example. It is an optical micrograph which shows the shape of the test piece for the migration resistance test of an Example and a comparative example. FIG. 4 is an optical microscope photograph showing an enlarged view of the center of the optical microscope photograph of the test piece for the migration resistance test shown in FIG. 3. FIG. A scanning electron microscope (SEM) photograph of the surface of a fired conductive paste after a test piece prepared under the same conditions as in Example 3 was stored in a sulfur-containing gas atmosphere for 150 hours to sulfurize it. (magnification: 5000 times). This is an SEM photograph (5000x magnification) of a cross section of a fired body of conductive paste after a test piece prepared under the same conditions as Example 3 was stored in a sulfur-containing gas atmosphere for 150 hours to sulfurize it. . Energy dispersive X-ray spectroscopy (EDS) analysis results (magnification: 5000x) corresponding to the cross-sectional SEM photograph of Example 3 shown in FIG. 6, showing the distribution of silver (Ag) content in gray scale. It is. FIG. 7 is an EDS analysis result (magnification: 5000 times) corresponding to the cross-sectional SEM photograph of Example 3 shown in FIG. 6, and is a diagram showing the distribution of sulfur (S) content in gray scale. This is an SEM photograph (5000x magnification) of the surface of a fired conductive paste after a test piece prepared under the same conditions as Comparative Example 1 was stored in a sulfur-containing gas atmosphere for 150 hours to sulfurize it. . This is an SEM photograph (5000x magnification) of a cross section of a fired body of conductive paste after a test piece prepared under the same conditions as Comparative Example 1 was stored in a sulfur-containing gas atmosphere for 150 hours to sulfurize it. . 11 is an EDS analysis result (magnification: 5000 times) corresponding to the cross-sectional SEM photograph of Comparative Example 1 shown in FIG. 10, and is a diagram showing the distribution of silver (Ag) content. 11 is an EDS analysis result (magnification: 5000 times) corresponding to the cross-sectional SEM photograph of Comparative Example 1 shown in FIG. 10, and is a diagram showing the distribution of sulfur (S) content. This is an SEM photograph (magnification: 5000x) of a region of a test piece prepared under the same conditions as in Example 3, where the amount of zinc present on the electrode surface is analyzed by EDS after being sulfurized in the sulfidation resistance test. 14 is a diagram showing in gray scale the results of measuring the amount of zinc oxide (ZnO) by EDS analysis corresponding to the SEM photograph of Example 3 shown in FIG. 13. FIG. 14 is a diagram showing in gray scale the results of measuring the amount of zinc aluminate (ZnAlO) by EDS analysis corresponding to the SEM photograph of Example 3 shown in FIG. 13. FIG.

Hereinafter, embodiments of the present invention will be specifically described. Note that the following embodiments are examples of embodying the present invention, and do not limit the present invention within its scope.

The conductive paste of this embodiment includes (A) conductive particles and (B) a binder resin. (A) The conductive particles include surface-treated metal particles. The conductive paste of this embodiment can be preferably used to form electrodes of electronic components such as chip resistors having electrodes made of the predetermined (A) conductive particles. (A) The conductive particles can contain 50% by weight or more of surface-treated metal particles that have been surface-treated with a zinc compound.

Hereinafter, the components contained in the conductive paste of this embodiment will be explained.

<(A) Conductive particles>
The conductive paste of this embodiment includes (A) conductive particles. (A) The conductive particles include surface-treated metal particles. The surface-treated metal particles include metal particles and a surface treatment layer disposed on at least a portion of the surface of the metal particles. The surface treatment layer is a thin film containing a zinc compound. The surface treatment layer is formed by surface treating metal particles with a zinc compound. (A) When the conductive particles contain predetermined surface-treated metal particles, sulfidation of the metal contained in the conductive particles can be suppressed. Therefore, by using the conductive paste of this embodiment, an electrode having high sulfidation resistance can be formed.

In addition, the inventors of the present invention have discovered that the (A) conductive particles of the conductive paste of this embodiment include predetermined surface-treated metal particles, thereby improving the migration resistance of the resulting electrode as an additional effect. We also found that it improved. Migration resistance means a property capable of suppressing migration. Migration is when a voltage is applied to a pair of electrodes (a positive electrode and a negative electrode), and if water and/or water vapor is present near the electrodes, the metals contained in the electrodes and wiring become ionized, and the positive This is a phenomenon in which metal dendrites move from the electrode to the negative electrode and the insulation between wiring parts decreases. Furthermore, migration may occur even in an atmosphere not affected by moisture, such as at 100° C. or higher or in a vacuum. In this case, even if a pair of electrodes is almost short-circuited, there are no dendrites between the wiring parts, which are always seen when migration occurs in the presence of moisture, and no polarity is observed ( In other words, it occurs regardless of the polarity of the positive and negative electrodes). Migration resistance means such a property that can suppress migration, which has been widely known in the past. A pair of electrodes may be short-circuited due to metal migration. By improving migration resistance, short circuits of the electrodes can be suppressed. In addition, the conductive paste of this embodiment is not only a conductive paste of a type that is fired at a relatively high temperature (for example, 500 to 900 °C), but also a conductive paste that is fired at a relatively low temperature (for example, 100 to 200 °C). It has been found that even in the case of a thermosetting conductive paste that is thermally cured by the method, the migration resistance of the resulting electrode is improved. However, the advantage of improved migration resistance is not necessarily an essential effect of the conductive paste of this embodiment, but is considered to be one advantage.

(A) The conductive particles can contain metals other than the surface-treated metal particles. However, in order to reliably obtain an electrode having low electrical resistance and high sulfidation resistance, it is preferable that (A) the conductive particles contain 50% by weight or more of surface-treated metal particles; It is more preferable to contain 80% by weight or more of surface-treated metal particles, it is even more preferable to contain 90% by weight or more of surface-treated metal particles, and it is especially preferable that the surface-treated metal particles are composed only of surface-treated metal particles. In addition, in this specification, "(A) conductive particles consist only of surface-treated metal particles" means that (A) conductive particles do not intentionally contain any metal other than surface-treated metal particles. This does not exclude the inclusion of conductive particles other than the surface-treated metal particles that are inevitably mixed in.

(A) The conductive particles can include metal particles of materials such as Zn, In, Al, and/or Si as metal particles other than the surface-treated metal particles, as long as the effects of this embodiment are not impaired. The metal particles included in the surface-treated metal particles and the metal particles other than the surface-treated metal particles can be metal particles of an alloy. Furthermore, the metal particles included in the surface-treated metal particles and the metal particles other than the surface-treated metal particles can include metal particles of a plurality of different types of metals or alloys.

The surface-treated metal particles include metal particles and a surface treatment layer disposed on at least a portion of the surface of the metal particles. The surface treatment layer is a thin film formed on at least a portion of the surface of the metal particles. By surface treating the metal particles with a zinc compound, a surface treatment layer can be formed on at least a portion of the surface of the metal particles. Therefore, the surface-treated metal particles can be metal particles whose surface has been treated with a zinc compound.

As the material of the metal particles whose surface is treated with the zinc compound, Ag, Cu, In, Al, or an alloy thereof can be used. Since the electrical conductivity is relatively high, the material of the metal particles is preferably Ag and/or Cu, and more preferably Ag.

In the conductive paste of the present embodiment, the metal particles preferably contain 50% by weight or more of silver (Ag), more preferably 80% by weight or more of silver (Ag), and 90% by weight of silver (Ag). It is more preferable to contain silver (Ag) in an amount of 95% by weight or more. In the most preferred embodiment, the metal particles of the surface-treated metal particles contained in the conductive paste of this embodiment consist only of silver (Ag) particles. This is because the electrical conductivity of silver is relatively high compared to other metals. In addition, in this specification, "the metal particles of the surface-treated metal particles consist only of silver (Ag) particles" means that metal particles other than silver (Ag) particles are intentionally not used as the metal particles. This does not preclude the inclusion of metal particles other than silver (Ag) particles that are unavoidably mixed. Similarly, other similar descriptions do not exclude substances that are unavoidably mixed.

The conductive paste of this embodiment preferably contains 50 parts by weight or more of surface-treated metal particles, more preferably 70 parts by weight or more, and still more preferably 80 parts by weight or more, based on 100 parts by weight of the conductive paste. preferable.
Further, the conductive paste of the present embodiment preferably contains 50 to 99 parts by weight of surface-treated metal particles, more preferably 70 to 97 parts by weight or more, and 80 to 95 parts by weight, based on 100 parts by weight of the conductive paste. It is more preferable to include parts by weight. By being within the above range, an electrode having high sulfidation resistance and relatively low cost can be formed.

The method for producing metal particles is not particularly limited, and can be produced by, for example, a reduction method, a pulverization method, an electrolysis method, an atomization method, a heat treatment method, or a combination thereof. Flake-shaped metal particles can be produced, for example, by crushing spherical or granular metal particles using a ball mill or the like.

The surface-treated metal particles include a surface treatment layer disposed on at least a portion of the surface of the metal particles. The surface treatment layer is a thin film formed on at least a portion of the surface of the metal particles by surface treating the metal particles with a surface treatment agent containing a zinc compound.

At least one zinc compound selected from zinc oxide, zinc chloride, zinc sulfate, zinc hydroxide, and zinc complexes such as zinc fatty acid complexes (e.g., zinc oleate, etc.) is used as a raw material for surface treatment of metal particles. One can be used.

The surface treatment layer can be formed by surface treatment using a zinc compound by a known method. Specifically, the surface treatment layer is formed by attaching a zinc soap solvent (surface treatment agent) containing zinc or zinc ions, an organic substance for dispersing these, and a solvent to the surface of the metal particles, and removing the solvent through a drying process. is removed. Thereby, a surface treatment layer containing a zinc compound can be formed on the surface of the metal particles. Note that there is also a technology in which the surface of metal particles is coated with other metal particles through reduction treatment to form a core-shell structure, but when attempting to form a surface treatment layer using this technology, core particles (e.g. Silver particles) Since metal particles are deposited as a shell on the surface, the amount of metal particles present in the shell increases. On the other hand, in the present invention, since the surface treatment layer is formed with the zinc compound attached to the surface of the metal particles, only a small amount of zinc can be used.

The organic substance for dispersing zinc or zinc ions is preferably at least one selected from fatty acids and triazole compounds. When using fatty acids, the fatty acids include butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, cabric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, Oleic acid, vaccenic acid, linoleic acid, linolenic acid, arachidic acid, eicosadienoic acid, eicosatrienoic acid, eicosatetraenoic acid, arachidonic acid, behenic acid, lignoceric acid, nervonic acid, cerotic acid, montanic acid, and melisic acid At least one selected from the following can be used. Among these fatty acids, it is preferable to use at least one selected from palmitic acid, stearic acid, and oleic acid. It is more preferable to use oleic acid as the organic substance (fatty acid) contained in the surface treatment agent. When using a triazole compound as an organic substance for dispersing zinc or zinc ions, benzotriazole can be used as the triazole compound.

Note that the solvent contained in the surface treatment agent for forming the surface treatment layer may be any solvent as long as it can be used to disperse the zinc compound and to properly adhere the zinc compound to the metal particles. Examples of solvents include alcohols such as methanol, ethanol, and isopropyl alcohol (IPA), organic acids such as ethylene acetate, aromatic hydrocarbons such as toluene and xylene, N-methyl-2-pyrrolidone (NMP), etc. N-alkylpyrrolidones, amides such as N,N-dimethylformamide (DMF), ketones such as methyl ethyl ketone (MEK), cyclic carbonates such as terpineol (TEL), and diethylene glycol monobutyl ether (butyl carbitol, BC) , bis[2-(2-butoxyethoxy)ethyl]adipate, 2,2,4-trimethylpentane-1,3-diol monoisobutyrate (Texanol), and water.

A surface treatment layer can be formed on the surface of the metal particles by attaching a surface treatment agent containing a solvent in which the above-mentioned zinc compound is dispersed to the surface of the metal particles and removing the solvent by drying. In this way, surface-treated metal particles can be obtained.

Furthermore, the surface treatment layer of the surface treated metal particles can be manufactured as follows. That is, first, metal particles are dispersed in water. A solvent in which the above-mentioned zinc compound is dispersed is added as a coating agent to water in which metal particles are dispersed to obtain a water slurry containing metal particles coated with a coating agent containing zinc, and then the coating is performed by decantation. The metal particles coated with the agent are allowed to settle. Next, the supernatant liquid is removed, and the resulting wet metal particles coated with the coating material are added together with an acrylic dispersant to a polar solvent having a boiling point of 150 to 300°C. Thereafter, surface-treated metal particles can be produced by drying in a nitrogen atmosphere at a temperature from room temperature to 100° C., preferably at a temperature of 80° C. or less for 12 hours or more to remove moisture. Note that if the drying temperature is too high, the surface-treated metal particles will be sintered, which is not preferable.

It is preferable that the surface treatment layer of the surface treated metal particles contained in the conductive paste of this embodiment further contains an organic substance. For example, when the surface treatment layer is formed using the above-mentioned zinc compound, the surface treatment layer contains an organic substance. Since the surface-treated metal particles have a surface-treated layer containing an organic substance, the resulting electrode can have high sulfidation resistance even if the amount of zinc compound is small. Note that the organic substance may be a liquid organic fatty acid or a solid fatty acid. Examples of liquid fatty acids include saturated fatty acids such as butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, and pelargonic acid, as well as myristoleic acid, palmitoleic acid, ricinoleic acid, oleic acid, linoleic acid, and linolenic acid. Unsaturated fatty acids such as These fatty acids may be used alone or in combination of two or more. Among these, it is preferable to use oleic acid, linoleic acid, or a mixture thereof. Examples of solid fatty acids include saturated fatty acids having 10 or more carbon atoms, such as capric acid, palmitic acid, and stearic acid, and unsaturated fatty acids, such as crotonic acid and sorbic acid.

The surface treatment layer of the surface treated metal particles used in this embodiment is a thin film of a zinc compound. This embodiment is characterized in that the surface treatment layer of the surface treatment metal particles is not a thin film made of zinc metal or zinc alloy. When the surface treatment layer is a thin film made of zinc metal or zinc alloy, the amount of zinc blended is too large, which may cause adverse effects such as an increase in the electrical resistance of the resulting electrode. Moreover, since a large amount of zinc metal or zinc alloy exists on the surface of the metal particles after firing, there is a high possibility that soldering of metal particles such as silver particles will be inhibited.

The surface treatment layer is a thin film formed on at least a portion of the surface of the metal particles. The surface treatment layer is preferably a thin film that covers 50% or more of the surface of the metal particle, more preferably a thin film that covers 80% or more of the surface of the metal particle, and covers 90% or more of the surface of the metal particle. A thin film is preferable, and a thin film covering 95% or more of the surface of the metal particles is particularly preferable. Most preferably, the surface treatment layer is a thin film that covers the entire surface of the metal particles.

The thickness of the surface treatment layer of the surface-treated metal particles does not necessarily have to be uniform, but is preferably uniform in order to more effectively suppress sulfidation of the metal particles. The thickness of the surface treatment layer can be controlled by, for example, controlling the viscosity of the zinc soap solvent (surface treatment agent) in which a zinc compound is dispersed, and the concentration of the zinc compound in the zinc soap solvent (surface treatment agent). It can be controlled by adjusting. Further, by controlling the thickness of the surface treatment layer, the amount of zinc in the surface treatment layer can be controlled. The thickness of the surface treatment layer is preferably from 1 to 100 nm, more preferably from 1 to 70 nm, and particularly preferably from 1 to 50 nm. The thickness of the surface treatment layer can be measured, for example, by X-ray photoelectron spectroscopy. By setting the thickness of the surface treatment layer within this range, it is possible to form an electrode with high sulfidation resistance even though the amount of zinc compound is small.

The conductive paste of this embodiment includes (A) surface-treated metal particles surface-treated with a zinc compound as conductive particles, thereby forming an electrode having high sulfidation resistance without using expensive palladium. be able to. Therefore, by using the conductive paste of this embodiment, an electrode having high sulfidation resistance and relatively low cost can be formed. In particular, when silver particles are used as metal particles, silver is easily sulfurized. By using the conductive paste of this embodiment, it is possible to effectively suppress disconnection of an electrode mainly made of silver due to sulfurization at low cost.

For example, when silver particles are used as metal particles, the reason why sulfidation of the silver particles can be suppressed by using surface-treated metal particles (surface-treated silver particles) whose surface has been treated with a zinc compound is as follows. It can be inferred as follows. That is, zinc is more easily sulfurized than silver. Therefore, in electrodes made of surface-treated metal particles in which zinc exists around metal particles (silver particles), the zinc is sulfurized and absorbs sulfur components in the atmosphere, and the sulfur components are absorbed by the metal particles (silver particles). silver particles). Therefore, it is thought that sulfidation of silver particles (metal particles) that have a conductive function as an electrode can be suppressed. Similar inferences can be made regarding metal particles other than silver particles. However, the present invention is not limited to this inference.

When the conductive particles (A) of the conductive paste of this embodiment include predetermined surface-treated metal particles, the migration resistance of the obtained electrode can be improved as an additional effect. The reason why migration resistance can also be improved by using surface-treated metal particles (surface-treated silver particles) surface-treated with a zinc compound can be inferred as follows. Since zinc has a higher ionization tendency than silver, it is presumed that by using zinc, zinc could trap electrons and suppress the ionization of silver. Further, by using surface-treated metal particles whose surface has been treated with a zinc compound, the denseness of the electrode is improved. It is presumed that this makes it difficult for moisture to enter, thereby improving migration resistance. However, the present invention is not limited to this inference.

In the conductive paste of this embodiment, the content of zinc contained in the surface-treated metal particles is preferably 10 to 1000 ppm, more preferably 15 to 950 ppm, even more preferably 20 to 900 ppm, and particularly preferably 22 to 850 ppm. . When the content of zinc contained in the surface-treated metal particles is within the above range, changes in the resistance value of the electrode due to sulfidation of the electrode can be reduced. Note that the content of zinc contained in the surface-treated metal particles can be measured by ICP emission spectrometry (high frequency inductively coupled plasma emission spectrometry).

(A) The shape of the conductive particles is not particularly limited, and for example, spherical, granular, flaky, and/or scaly surface-treated metal particles can be used.

The average particle diameter of the conductive particles (A) is preferably 0.5 μm to 10 μm, more preferably 0.8 μm to 8 μm, and still more preferably 1 μm to 7 μm. The average particle diameter herein means the volume-based median diameter (D50) obtained by laser diffraction scattering particle size distribution measurement method. (A) If the average particle diameter (D50) of the conductive particles is larger than 10 μm, sinterability is poor and a dense film cannot be obtained. In addition, if the average particle diameter (D50) of (A) conductive particles is less than 0.5 μm, the dispersibility tends to deteriorate, making it difficult to obtain a uniform thin film when printing the conductive paste. There are cases.

<(B) Binder resin>
The conductive paste of this embodiment includes (B) a binder resin.

The (B) binder resin connects the (A) conductive particles together in the conductive paste. Note that the conductive paste of this embodiment may or may not include (C) glass frit, which will be described later. The function of the binder resin (B) included in the conductive paste of this embodiment is different depending on whether it contains (C) glass frit or not.

When the conductive paste of this embodiment includes (C) glass frit, the conductive paste of this embodiment is applied to a predetermined base material so as to form a predetermined electrode pattern, and heated to a relatively high temperature (for example, 500 to 900°C). ), an electrode can be formed. In this case, the binder resin (B) is burned out during firing. Therefore, the function of the binder resin (B) in this case is to (A) connect the conductive particles together when the conductive paste of this embodiment is applied to a predetermined base material in a predetermined electrode pattern. That's true.

When the conductive paste of this embodiment does not contain (C) glass frit, the conductive paste of this embodiment is applied to a predetermined base material so as to form a predetermined electrode pattern, and the conductive paste is applied at a relatively low temperature (for example, 100 to 200 ℃), an electrode can be formed. In this case, the binder resin (B) is not burned out during heat treatment. In this case, the function of the binder resin (B) is to connect the conductive particles (A) to each other when the conductive paste of this embodiment is applied to a predetermined base material in a predetermined electrode pattern. (A) The shape of the electrode after the heat treatment is maintained by connecting the conductive particles together after the heat treatment.

(B) As the binder resin, for example, cellulose resins such as ethyl cellulose resin and nitrocellulose resin, thermoplastic resins such as acrylic resin, alkyd resin, saturated polyester resin, butyral resin, polyvinyl alcohol, and hydroxypropyl cellulose may be used. I can do it. These resins can be used alone or in combination of two or more.

As the binder resin (B), it is preferable to use at least one selected from cellulose resins such as ethyl cellulose resins and nitrocellulose resins, and alkyd resins.

When the conductive paste of this embodiment does not contain (C) glass frit, in order to improve the adhesion between the surface-treated metal particles, (B) epoxy resin is used as the binder resin. can include. There are no particular restrictions on the type of epoxy resin, and any known epoxy resin can be used. Examples of epoxy resins include bisphenol A type, bisphenol F type, biphenyl type, tetramethylbiphenyl type, cresol novolac type, phenol novolac type, bisphenol A novolac type, dicyclopentadienephenol condensation type, phenol aralkyl condensation type, and glycidylamine. Examples include epoxy resins such as molds, brominated epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. These epoxy resins can be used alone or in combination of two or more. Furthermore, a thermosetting resin other than epoxy resin may be used for the purpose of improving the adhesion between surface-treated metal particles. Furthermore, thermoplastic resins such as polyurethane resins and/or polycarbonate resins may also be used.

The content of the binder resin (B) is preferably 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight, and even more preferably The amount is 2 to 10 parts by weight, particularly preferably 3 to 7 parts by weight. When the content of the binder resin (B) in the conductive paste is within the above range, the applicability of the conductive paste to the substrate (base material) and/or the paste leveling properties are improved, resulting in an excellent printed shape. Obtainable. On the other hand, when the content of the binder resin (B) exceeds the above range, the amount of the binder resin (B) contained in the applied conductive paste is too large. Therefore, there is a possibility that electrodes and the like cannot be formed with high precision.

<(C) Glass frit>
The conductive paste of this embodiment can further include (C) glass frit.

When the conductive paste of this embodiment includes (C) glass frit, the conductive paste of this embodiment is applied to a predetermined base material so as to form a predetermined electrode pattern, and heated to a relatively high temperature (for example, 500 to 900°C). ), an electrode can be formed. In this case, the above-mentioned binder resin (B) is burned out during firing. The shape of the electrode after firing can be maintained by connecting the (A) conductive particles together using the (C) glass frit contained in the conductive paste.

The glass frit is not particularly limited, but a glass frit with a softening point of preferably 300°C or higher, more preferably 400 to 900°C, and even more preferably 500 to 800°C can be used. The softening point of the glass frit can be measured using a thermogravimetric measuring device (for example, TG-DTA2000SA manufactured by BRUKER AXS).

Examples of the glass frit (C) include borosilicate-based and barium borosilicate-based glass frits. Examples of glass frits include bismuth borosilicate, alkali metal borosilicate, alkaline earth metal borosilicate, zinc borosilicate, lead borosilicate, lead borate, lead silicate, and bismuth borate. and zinc borate-based glass frits. These glass frits can also be used in combination of two or more types. The glass frit is preferably lead-free from the viewpoint of environmental considerations.

It is preferable that the glass frit contains at least one selected from the group consisting of ZnO, Bi ₂ O ₃ , BaO, Na ₂ O, CaO, and Al ₂ O ₃ . More preferably, the glass frit contains at least one selected from the group consisting of ZnO and Bi ₂ O ₃ .

When the conductive paste of this embodiment includes (C) glass frit, it is more preferable that the glass frit includes ZnO. When a glass frit containing ZnO (zinc-based glass frit) is used as the glass frit, an electrode with higher sulfidation resistance can be obtained.

When the conductive paste of this embodiment includes (C) glass frit, it is more preferable that the glass frit includes Bi ₂ O ₃ . When a glass frit containing Bi ₂ O ₃ (bismuth-based glass frit) is used as the glass frit, the density of the electrode can be improved.

The average particle size of the glass frit is preferably 0.1 to 20 μm, more preferably 0.2 to 10 μm, and most preferably 0.5 to 5 μm. The average particle size here means the volume-based median diameter (D50) obtained by laser diffraction scattering particle size distribution measurement method.

When the conductive paste of the present embodiment includes (C) glass frit, the content of (C) glass frit is preferably 0.05 to 10 parts by weight based on 100 parts by weight of (A) conductive particles. The amount is preferably 0.07 to 8 parts by weight, more preferably 0.08 to 6 parts by weight. If the content of glass frit is less than this range, the adhesion of the electrode obtained by firing the conductive paste to the substrate (base material) will decrease. If the content of glass frit is more than this range, the resistance value of the electrode obtained by firing the conductive paste will be high, and the surface of the fired body will be covered with the glass component, resulting in poor plating properties. Note that when the content of glass frit is relatively small, an electrode with low resistance can be obtained. Moreover, when the content of glass frit is relatively large, an electrode with excellent chemical resistance can be obtained. Chemical resistance is a required property because plating pretreatment is required when forming a plating film on the surface of an electrode. Plating pretreatment is performed for the purpose of removing contaminants from the electrode surface, activating the electrode surface, and bringing it into a clean state suitable for plating. The pollutants that need to be removed can be broadly divided into organic and inorganic pollutants. The pretreatment step is not a single step that removes all contaminants. For example, organic substances are removed in a process using an alkaline cleaning agent. Inorganic substances are removed in a process using acid-based cleaning agents. Therefore, electrodes are required to have high chemical resistance.

When the conductive paste of this embodiment includes (C) glass frit, the glass frit softens as the temperature rises, and the sintering (firing) of the (A) conductive particles progresses. When the glass frit content is large, the glass component may be pushed out to the surface of the fired body. In that case, the surface of the fired body may be covered with a glass component. (C) When the glass frit contains zinc oxide, the Zn component in the glass frit precipitates as ZnO at the crystallization temperature, so the (A) conductivity after firing is It can contribute to the sulfidation resistance of particles.

<(D) Dispersant>
The conductive paste of this embodiment can contain (D) a dispersant. By containing the (D) dispersant in the conductive paste of this embodiment, the dispersibility of the (A) conductive particles in the conductive paste can be improved, and the agglomeration of the (A) conductive particles can be prevented. can do.

(D) As the dispersant, a known dispersant can be used. (D) As the dispersant, for example, an acid type dispersant can be used.

<(E) Solvent>
The conductive paste of this embodiment can contain (E) a solvent. Examples of solvents include alcohols such as methanol, ethanol, and isopropyl alcohol (IPA), organic acids such as ethylene acetate, aromatic hydrocarbons such as toluene and xylene, and N-methyl-2-pyrrolidone (NMP). N-alkylpyrrolidones such as, amides such as N,N-dimethylformamide (DMF), ketones such as methyl ethyl ketone (MEK), cyclics such as terpineol (TEL), and diethylene glycol monobutyl ether (butyl carbitol, BC) Examples include carbonates, bis[2-(2-butoxyethoxy)ethyl]adipate, 2,2,4-trimethylpentane-1,3-diol monoisobutyrate (Texanol), and water.

The content of the solvent in the conductive paste of this embodiment is not particularly limited. The content of the solvent is, for example, preferably 1 to 100 parts by weight, more preferably 5 to 60 parts by weight, and still more preferably 8 to 35 parts by weight, based on 100 parts by weight of the (A) conductive particles.

The viscosity of the conductive paste of this embodiment is preferably 50 to 700 Pa·s (shear rate: 4.0 sec ⁻¹ ), more preferably 100 to 300 Pa·s (shear rate: 4.0 sec ⁻¹ ). The viscosity of the conductive paste of this embodiment can be adjusted by appropriately controlling the content of the solvent. By adjusting the viscosity of the conductive paste within this range, the applicability and/or handling of the conductive paste to the substrate (base material) becomes good, and the conductive paste can be applied to the substrate with a uniform thickness. becomes possible. Note that the viscosity of the conductive paste can be measured at a temperature of 25° C. and 10 rpm using an HB type viscometer (manufactured by Brookfield Corporation) (SC4-14 spindle).

<(F) Curing agent>
It is preferable that the conductive paste of this embodiment further contains (F) a curing agent. When the conductive paste of this embodiment contains an epoxy resin as the binder resin (B), the curing of the epoxy resin can be appropriately controlled by including the curing agent (F).

(F) A known curing agent can be used as the curing agent. (F) The curing agent preferably contains at least one selected from a phenolic curing agent, a cationic polymerization initiator, an imidazole curing agent, and a boron trifluoride compound. Examples of the boron trifluoride compound include boron trifluoride monoethylamine, boron trifluoride piperidine, and boron trifluoride diethyl ether. (F) As the curing agent, boron trifluoride monoethylamine can be preferably used.

In the conductive paste of this embodiment, when the total weight of (A) conductive particles and (C) epoxy resin as a binder resin is 100 parts by weight, the conductive paste contains 0 (F) curing agent. .1 to 5 parts by weight, more preferably 0.15 to 2 parts by weight, even more preferably 0.2 to 1 parts by weight, particularly 0.3 to 0.6 parts by weight. preferable. By setting the weight ratio of the curing agent (F) within a predetermined range, the epoxy resin that is the binder resin component (B) can be appropriately cured, and an electrode with a desired shape can be obtained.

<Other ingredients>
The conductive paste of this embodiment can contain other additives, such as organic additives and inorganic additives. Specifically, it may contain a silica filler, a rheology modifier, and/or a pigment as an additive.

By adding an organic additive to the conductive paste as an additive, the printability of the conductive paste can be improved. By adding a dispersant to the conductive paste as an additive, the dispersibility of conductive particles and the like can be improved. By adding an inorganic additive to the conductive paste as an additive, the adhesion of the conductive paste after firing can be improved.

The conductive paste of this embodiment can be manufactured by mixing the above-mentioned components using, for example, a Raikai machine, a pot mill, a three-roll mill, a rotary mixer, and/or a twin-shaft mixer. .

<Electrode>
This embodiment is an electrode obtained by firing or heat-treating the conductive paste of this embodiment described above.

When the conductive paste of this embodiment includes (C) glass frit, the conductive paste of this embodiment is applied to a predetermined base material so as to form a predetermined electrode pattern, and heated to a relatively high temperature (for example, 500 to 900°C). ), the electrode can be formed by firing in an air atmosphere. Therefore, when the conductive paste of this embodiment contains (C) glass frit, the electrode is made of (A') conductive particles containing surface-treated metal particles and (C) glass frit. It can contain a glass component. After firing, the conductive particles (A') are in a sintered state. Note that when the conductive paste of this embodiment is fired at a relatively high temperature (for example, 500 to 900°C), the binder resin (B) and the solvent (E) contained in the conductive paste are vaporized or burned during firing. do. Therefore, the electrode does not substantially contain (B) binder resin and (E) solvent.

When the conductive paste of this embodiment does not contain (C) glass frit, the conductive paste of this embodiment is applied to a predetermined base material so as to form a predetermined electrode pattern, and the conductive paste is applied at a relatively low temperature (for example, 100 to 200 ℃), an electrode can be formed. Therefore, when the conductive paste of this embodiment does not contain (C) glass frit, the electrode of this embodiment is made of (A') conductive particles containing surface-treated metal particles and (B) a binder resin. (B') a binder component. (A') The conductive particles are connected via the (B') binder component.

Since the surface-treated metal particles contained in the conductive paste of this embodiment are surface-treated with a zinc compound, the electrode of this embodiment contains zinc. The electrode of this embodiment preferably contains 0.1 to 10% by weight of zinc, more preferably 0.5 to 8% by weight, and even more preferably 1 to 5% by weight of zinc. In addition, when the electrically conductive paste of this embodiment contains (C) glass frit, the electrode of this embodiment can contain zinc resulting from (C) glass frit. Since the electrode of this embodiment contains a predetermined amount of zinc, the electrode of this embodiment can have high sulfidation resistance. Note that the zinc content in the electrode can be measured by elemental analysis using EDS (Energy Dispersive X-ray Spectroscopy).

The sheet resistance of the thin film serving as the electrode of this embodiment varies depending on the film thickness, but can be approximately 10 mΩ/square or less than 10 mΩ/square. Therefore, it can be preferably used for forming electrodes that are required to have low resistance.

Next, a method for forming electrodes on a substrate (base material) using the conductive paste of this embodiment will be described. First, a conductive paste is applied onto the substrate. The conductive paste can be applied by any known method, such as dispensing, jet dispensing, stencil printing, screen printing, pin transfer, or stamping.

When the conductive paste of this embodiment includes (C) glass frit, after applying the conductive paste on the substrate, it is dried if necessary, and the substrate is placed in a firing furnace or the like. Then, the conductive paste applied onto the substrate is fired at 500 to 900°C, more preferably 600 to 880°C, and still more preferably 700 to 870°C. A specific example of the firing temperature is 850°C. As a result, the solvent component contained in the conductive paste evaporates at 300° C. or lower, and the resin component is burned out at 400° C. to 600° C., forming a fired body (electrode) of the conductive paste. Further, it is considered that the organic components contained in the surface-treated metal particles disappear by firing in an air atmosphere, and the zinc in the zinc compound exists as a coating on the surface of the metal particles as zinc oxide. The electrode thus obtained has high sulfidation resistance and excellent adhesion to the substrate.

When the conductive paste of this embodiment does not include (C) glass frit, the conductive paste is applied onto the substrate, and then the substrate is placed in a heat treatment furnace or the like. Then, the conductive paste applied on the substrate is heat treated at 100 to 200°C, more preferably 150 to 200°C. The heat treatment time is preferably 20 to 90 minutes, more preferably 30 to 60 minutes. A specific example of the heat treatment conditions is 150° C. for 60 minutes. Thereby, a cured body (electrode) of the conductive paste can be formed by drying the solvent component contained in the conductive paste and thermosetting the conductive paste. The electrode thus obtained has high sulfidation resistance and excellent adhesion to the substrate.

Furthermore, the electrode obtained as described above using the conductive paste of this embodiment can have the additional advantage of improved migration resistance. This additional advantage can be obtained both when the conductive paste contains (C) a glass frit and (C) does not contain a glass frit. However, this advantage is not necessarily an essential effect of the conductive paste of this embodiment, but is considered to be one advantage.

<Electronic parts or electronic equipment>
This embodiment is an electronic component or electronic device having the above-described electrode. In this specification, electronic components refer to components used in electronic devices, such as chip resistors and board circuits. In this specification, an electronic component means a component that operates electronically, and specifically can be a component that operates at 48 V or less of DC. In this specification, an electronic device means a device including an electronic component having the electrode of this embodiment.

The conductive paste of this embodiment can be used for forming circuits of electronic components or electronic equipment, forming electrodes, and bonding devices such as electronic components (for example, semiconductor chips) to a substrate (base material). be.

The conductive paste of this embodiment can be preferably used for forming electrodes of chip resistors. FIG. 1 shows an example of a cross-sectional structure of a chip resistor 100 of this embodiment. The chip resistor 100 can include a rectangular alumina substrate 102, a resistor 104 and an extraction electrode 106 arranged on the surface of the alumina substrate 102. The extraction electrode 106 is an electrode for extracting electricity from the resistor 104. Furthermore, a lower surface electrode 108 for mounting the chip resistor 100 on the substrate can be arranged on the lower surface of the alumina substrate 102. Furthermore, a connection electrode 110 for connecting the extraction electrode 106 and the lower surface electrode 108 can be arranged on the end surface of the alumina substrate 102. At least one of the extraction electrode 106, the bottom electrode 108, and the connection electrode 110 can be formed using the conductive paste of this embodiment. In particular, it is preferable that the extraction electrode 106 be formed using the conductive paste of this embodiment. Note that a nickel plating film 112 and a tin plating film 114 can be disposed on the top surface of the extraction electrode 106, the bottom electrode 108, and the connection electrode 110 (the surface opposite to the alumina substrate 102).

The electrode of this embodiment is not limited to the electrode of a chip resistor. Electrodes formed using the conductive paste of this embodiment can be used as electrodes for various types of electronic components. Electronic components include passive components (for example, chip resistors, capacitors, resistors, inductors, etc.), circuit boards (for example, a predetermined circuit (electrode or wiring) on a substrate such as an alumina substrate, an aluminum nitride substrate, a glass substrate, etc.). ), solar cells, and electromagnetic shields. The conductive paste of this embodiment can be used to form electrodes and/or wiring of these electronic components. Examples of electronic devices including electronic components having the electrodes of this embodiment include semiconductor devices, photovoltaic modules, and electronic devices including circuit boards.

The conductive paste of this embodiment can be used as a die attach material for attaching a semiconductor chip in a semiconductor device. When the semiconductor device is a power semiconductor device, it can be used as a brazing material for attaching a power semiconductor chip. The conductive paste of this embodiment can be used as an electrode of a solar cell. The conductive paste of this embodiment can be used as a conductive adhesive. Furthermore, the conductive paste of this embodiment can be suitably used not only for forming terminal electrodes of chip resistors, but also as a conductive paste for terminal electrodes of passive components such as MLCCs and chip inductors. .

By using the conductive paste of this embodiment, it is possible to form an electrode that has high sulfidation resistance, low resistance, and relatively low cost. Therefore, by using the conductive paste of this embodiment, electronic components such as chip resistors in which highly reliable electrodes are formed can be obtained at relatively low cost.

Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

[Preparation of conductive paste]
A conductive paste was prepared by mixing the following components (A) to (F) in the proportions shown in Tables 1 to 4. Note that all the proportions of each component shown in Tables 1 to 4 are shown in parts by weight. In Tables 1 to 4, the weight of (A) conductive particles (total weight of metal particles and surface-treated metal particles) was 100 parts by weight. Moreover, the average particle size means the volume-based median diameter (D50) obtained by laser diffraction scattering particle size distribution measuring method.

(A) Conductive particles Table 5 shows metal particles a1 to a3 and surface-treated metal particles A1 to A8 used as (A) conductive particles (component (A)) in Examples and Comparative Examples. Metal particles a1 and a2 are silver particles, and metal particle a3 is a zinc particle. Metal particles a1 to a3 are not surface-treated. Surface-treated metal particles A1 to A8 are produced by attaching a zinc soap solvent (surface treatment agent) in which a zinc compound is dispersed in a solvent to the surface of silver particles, which are metal particles, and removing the solvent through a drying process. The surface was treated by Therefore, the surface-treated metal particles A1 to A8 have a surface-treated layer containing a zinc compound. The "zinc content" column in Table 5 shows the weight ratio of zinc contained in the surface treatment layer to the weight of the surface treatment metal particles A1 to A8 in units of ppm by weight. The weight proportion of zinc in the surface-treated metal particles was measured by ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy). As described above, surface treatment layers were formed on the surface treatment metal particles A1 to A8.

Surface treatment of silver particles with a zinc compound was performed as follows. That is, the surface treatment of the silver particles with a zinc compound was performed using a zinc soap solvent (surface treatment agent) containing a zinc compound, an organic substance for dispersing these, and a solvent. The surface treatment was performed by attaching this zinc soap solvent (surface treatment agent) to the surface of the silver particles and removing the solvent through a drying process. Zinc oleate was used as the zinc compound. Furthermore, oleic acid was used as a dispersant included in the surface treatment agent for silver particles.

(B) Binder resin Table 6 shows the (B) binder resins (resins B1 to B6) used in the examples and comparative examples. Tables 1 to 4 show the blending amounts of resins B1 to B6 in the conductive pastes of Examples and Comparative Examples.

(C) Glass Frit Table 7 shows the (C) glass frits (GF-C1 and GF-C2) used in Examples and Comparative Examples. Tables 1 to 4 show the blending amounts of glass frits GF-C1 and GF-C2 in the conductive pastes of Examples and Comparative Examples.

(D) Dispersant In the conductive pastes of Examples and Comparative Examples, an acid type low molecular dispersant 3M 221P (manufactured by NOF Corporation) was used as the (D) dispersant (dispersant D). Tables 1 to 4 show the amount of dispersant D in the conductive pastes of Examples and Comparative Examples.

(E) Solvents Table 8 shows the (E) solvents (solvents E1 to E4) used in the Examples and Comparative Examples. Tables 1 to 4 show the blending amounts of solvents E1 to E4 in the conductive pastes of Examples and Comparative Examples.

(F) Hardening agent F
In the conductive pastes of Examples 20 to 22, boron trifluoride monoethylamine (Stella Chemifa Co., Ltd.) was used as the curing agent F (F). Table 4 shows the amount of curing agent F in the conductive pastes of Examples 20 to 22.

[Preparation of test piece 50 for sulfidation resistance test]
FIG. 2 shows a schematic diagram of a test piece 50 for the sulfidation resistance test. (C) Using a conductive paste containing glass frit, test pieces 50 for sulfidation resistance tests of Examples 1 to 19 and Comparative Examples 1 to 3 were prepared according to the following procedure.

First, on a 20 mm x 20 mm x 1 mm (t) alumina substrate 52 (purity 96%) for sulfidation resistance testing, a zigzag printed pattern 54 for sulfidation resistance testing as shown in FIG. 2 is formed by screen printing. A conductive paste was applied. The length between the two ends 54a and 54b of the printed pattern 54 for sulfidation resistance testing is 71 mm, and the width of the printed pattern 54 for sulfidation resistance testing is 1 mm. In order to form a printed pattern 54 for testing the sulfidation resistance of the conductive paste, screen printing was performed using a stainless steel 325 mesh screen (emulsion thickness 5 μm). Next, the printed pattern 54 for sulfidation resistance test of the conductive paste was dried at 150° C. for 10 minutes using a batch type hot air dryer. After drying the printed pattern 54 for sulfidation resistance test of the conductive paste, the printed pattern 54 for sulfidation resistance test was fired using a belt-type firing furnace. The firing temperature was maintained at 850°C for 10 minutes. The total time from putting it in the kiln to taking it out was 60 minutes. In the manner described above, test pieces 50 of Examples 1 to 19 and Comparative Examples 1 to 3 were produced.

(C) For Examples 20 to 22 using conductive pastes that do not contain glass frit, similarly to Examples 1 to 19 and Comparative Examples 1 to 3, using the conductive pastes of Examples 20 to 22, A zigzag print pattern 54 (Fig. 2 A conductive paste was applied as shown in (see). Next, the printed pattern 54 for sulfidation resistance test of the conductive paste was heat-treated at 150° C. for 10 minutes using a batch type hot air dryer to harden the printed pattern 54 for sulfidation resistance test. . In the manner described above, test pieces 50 of Examples 20 to 22 were produced.

[Sulfidation resistance test method]
First, the electrical resistance (initial electrical resistance) between the two ends 54a and 54b of the printed pattern 54 for sulfidation resistance test of the test pieces of Examples and Comparative Examples was measured. Next, a petri dish (height 18 mm, diameter 86 mm) containing 10 g of sulfur powder was placed in the bottom of a glass desiccator (height 420 mm, diameter 300 mm), and the Example and A test piece of a comparative example was placed. This desiccator was stored in a constant temperature bath at 60° C. for 150 hours to sulfurize the test piece. Next, the electrical resistance after sulfurization was measured. In the "Resistance value change rate (sulfidation resistance test)" column of Tables 1 to 4, the resistance value change rate of the electrical resistance after sulfidation with respect to the initial electrical resistance of Examples and Comparative Examples is shown in percent. The resistance value change rate can be expressed by the following formula.
Resistance value change rate = (electrical resistance after sulfidation - initial electrical resistance) / initial electrical resistance

[Preparation of test piece for adhesive strength test]
Using the prepared conductive paste, test pieces of Examples 1 to 19 and Comparative Examples 1 to 3 containing (C) glass frit were produced according to the following procedure. First, a conductive paste was applied by screen printing onto a 20 mm x 20 mm x 1 mm (t) alumina substrate (purity 96%). As a result, 25 (5×5) adhesive strength test patterns each having a square pad shape of 1.5 mm on a side were formed on the alumina substrate. In order to form a pattern for testing the adhesive strength of the conductive paste, screen printing was performed using a stainless steel 325 mesh screen (emulsion thickness: 5 μm).

Next, the conductive paste was dried at 150° C. for 10 minutes using a batch hot air dryer. After drying the pattern for testing the adhesive strength of the conductive paste, the pattern for testing the adhesive strength of the conductive paste was fired using a belt-type firing furnace. The firing temperature was maintained at 850°C for 10 minutes. The total time from putting it in the kiln to taking it out was 60 minutes. In the manner described above, test pieces of Examples 1 to 19 and Comparative Examples 1 to 3 were prepared.

Next, Ni/Au plating was performed on the adhesive strength test pattern. Next, solder (M705 manufactured by Senju Metal Industry Co., Ltd., a Sn alloy containing 3.0% by weight of Sn-Ag and 0.5% by weight of Cu) was attached to the adhesive strength test pattern at 260°C for 3 seconds. After that, a Sn-plated annealed copper wire (diameter 0.8 mm) was soldered to the adhesive strength test pattern. For soldering the Sn-plated annealed copper wire, out of the 5 x 5 adhesive strength test patterns on the alumina board, one for each of the 5 pieces in the second row, for a total of 5 Sn-plated annealed copper wires. This was done by soldering a total of five Sn-plated annealed copper wires, one for each of the five wires in the fourth row. A total of 10 Sn-plated annealed copper wires were soldered, and the tensile adhesive strength of the lead wires was measured using a strength testing machine. Specifically, the alumina substrate was installed perpendicularly to the strength testing machine at a 90 degree angle so that the adhesive strength test pattern was on the top surface, and the lead wires were placed upward perpendicularly to the alumina substrate. The tensile adhesive strength was measured by pulling the sample. The force (N) when the lead wire was peeled off was defined as the tensile adhesive strength.

Similar to the test pieces of Examples 1 to 19 and Comparative Examples 1 to 3, the conductive pastes prepared as Examples 20 to 22 were used on a 20 mm x 20 mm x 1 mm (t) alumina substrate (purity 96%). Then, a conductive paste was applied by screen printing. As a result, 25 (5×5) adhesive strength test patterns each having a square pad shape of 1.5 mm on a side were formed on the alumina substrate. Next, the conductive paste was heat-treated at 150° C. for 10 minutes using a hot air dryer to harden the adhesive strength test pattern of the conductive paste. In the manner described above, test pieces of Examples 20 to 22 were produced. Next, in the same manner as Examples 1 to 19 and Comparative Examples 1 to 3, Ni/Au plating was performed on the adhesive strength test patterns of Examples 20 to 22. Next, in the same way as the test pieces of Examples 1 to 19 and Comparative Examples 1 to 3, Sn-plated annealed copper wire (lead wire) was soldered to the adhesive strength test pattern, and the tensile adhesive strength of the lead wire was measured using a strength tester. was measured.

The results of the adhesive strength test were obtained by measuring the tensile adhesive strength of 10 test pieces of each example and each comparative example. The "Adhesive Strength (N)" column of Tables 1 to 4 shows the average value of the tensile adhesive strength of the 10 test pieces of each Example and each Comparative Example measured as described above.

[Migration resistance test]
FIG. 3 shows an optical micrograph of test print patterns 64a and 64b of an example of the test piece 60 for the migration resistance test. Using the prepared conductive paste, test pieces 60 for the migration resistance test of Examples 3, 4, and 20 to 22, and Comparative Example 1 were prepared according to the following procedure.

The test pieces 60 for the migration resistance test of Examples 3 and 4 and Comparative Example 1 were produced in the following procedure. First, on a 110 mm x 20 mm x 0.8 mm (t) alumina substrate 62 (purity 96%) for migration resistance testing, as shown in FIG. 3 and FIG. The conductive paste was applied so that the two comb-shaped migration resistance test printed patterns 64a and 64b were alternated. The printed pattern for migration resistance test 64a is connected to the first electrode 66a, and the printed pattern for migration resistance test 64b is connected to the second electrode 66b. The print width L of the migration resistance test print patterns 64a, 64b is 200 μm, and the space S between the migration resistance test print patterns 64a, 64b is 200 μm. In order to form printed patterns 64a, 64b and electrodes 66a, 66b for conductive paste migration resistance testing, screen printing was performed using a 400 mesh screen made of stainless steel (emulsion thickness 10 μm). Next, the printed patterns 64a, 64b for the migration resistance test of the conductive paste and the electrodes 66a, 66b were dried at 150° C. for 10 minutes using a batch type hot air dryer. After drying the conductive paste migration resistance test printed patterns 64a, 64b and electrodes 66a, 66b, the migration resistance test printed patterns 64a, 64b and electrodes 66a, 66b were fired using a belt-type firing furnace. . The firing temperature was maintained at 850°C for 10 minutes. The total time from putting it in the kiln to taking it out was 60 minutes. The thickness of the migration test printed patterns 64a, 64b and the electrodes 66a, 66b after firing was 10 to 20 μm. As described above, test pieces 60 for the migration resistance test of Examples 3 and 4 and Comparative Example 1 were prepared.

The test piece 60 for the migration resistance test of Examples 20 to 22 was produced in the following procedure. First, similarly to the test piece 60 of Examples 3 and 4 and Comparative Example 1, a 110 mm x 20 mm x 0.8 mm (t) alumina substrate 62 (purity 96%) for migration resistance testing was coated with screen printing. As shown in FIGS. 3 and 4, the conductive paste was applied so that the two comb-shaped migration resistance test printed patterns 64a and 64b were alternated. Next, the conductive paste was heat-treated at 200° C. for 30 minutes using a hot air dryer to harden the adhesive strength test pattern of the conductive paste. In the manner described above, test pieces for the migration resistance tests of Examples 20 to 22 were prepared.

The migration resistance of the printed patterns 64a and 64b for the migration resistance test of Examples 3, 4, and 20 to 22 and Comparative Example 1 was measured according to the following procedure. First, as shown in FIG. 3, a voltage (40 V) was applied between the first electrode 66a and the second electrode 66b of the two migration resistance test printed patterns 64a and 64b. The insulation resistance value between the first electrode 66a and the second electrode 66b was measured while stored in an environment with a temperature of 85° C. and a humidity of 85%. The insulation resistance value was calculated from the measured value of the current flowing between the first electrode 66a and the second electrode 66b and the applied voltage of 40V. The test piece 60 to which an applied voltage of 40 V was applied was held in an environment of a temperature of 85° C. and a humidity of 85% for a maximum of 500 hours. Table 9 shows the results of the migration resistance test. Before the test, the insulation resistance values of all samples were 10 ⁷ Ω or more. A test piece 60 whose insulation resistance value became 10 ⁶ Ω or less within 500 hours was judged to be defective, and was written as "defective" in Table 9. Test piece 60 whose insulation resistance value did not fall below 10 ⁶ Ω even after 500 hours was judged to have excellent migration resistance, and was listed as "good" in Table 9.

[Amount of zinc in electrode]
Using the conductive paste prepared in Example 3, the amount of zinc on the electrode surface of the test piece after the sulfidation resistance test was quantitatively analyzed by EDS (energy dispersive X-ray spectroscopy) analysis. As a result, it was confirmed that 3.09% zinc component was precipitated on the surface of zinc. Moreover, FIG. 13 shows an SEM photograph (5000x magnification) for EDS analysis of the zinc distribution on the electrode surface of the test piece after the sulfidation resistance test. 14 and 15 show in gray scale the results of measuring the distribution of zinc oxide (ZnO) and zinc aluminate (ZnAlO) by EDS analysis corresponding to the SEM photograph shown in FIG. 13. As shown in FIGS. 13 to 15, it was confirmed that zinc was not present alone on the electrode surface, but as zinc oxide and zinc aluminate.

[Surface and cross-sectional observation by SEM, and cross-sectional observation by EDS analysis]
Figures 5 and 6 show the surface and cross section of a test piece prepared under the same conditions as test piece 50 of the sulfidation resistance test of Example 3, in which the rate of change in resistance value was relatively small. A SEM photograph taken by an electron microscope (SEM) is shown. 7 and 8 show the results of EDS analysis of a cross section of a test piece prepared under the same conditions as the test piece 50 of the sulfidation resistance test of Example 3. 9 and 10, the surface and cross section of a test piece prepared under the same conditions as test piece 50 of the sulfidation resistance test of Comparative Example 1, in which the rate of change in resistance value was large, was photographed by SEM at a magnification of 5000 times. A SEM photograph is shown. 11 and 12 show the results of EDS analysis of a cross section of a test piece prepared under the same conditions as the test piece 50 of the sulfidation resistance test of Comparative Example 1. Note that, as in the case of the sulfidation resistance test, the test piece was stored in a sulfur atmosphere (60° C.) for 150 hours, and then subjected to SEM observation and EDS analysis.

[evaluation]
As is clear from the results shown in Tables 1 to 4, the electrode patterns obtained by firing the conductive pastes of Examples 1 to 22 had a resistance change rate of 220.2% or less (Example 19). , was relatively low. On the other hand, the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 3 had a resistance value change rate of 300% or more (Comparative Example 1) or were exposed to a sulfur atmosphere in the sulfidation resistance test. The electrical resistance value after storage was too high to be measured.

As is clear from the results shown in Tables 1 to 4, the tensile adhesive strength of the adhesive strength test patterns obtained by firing the conductive pastes of Examples 1 to 22 was 17.2N (Examples 7, 17, and 21) to 25.9N (Example 10), and a high tensile adhesive strength could be obtained. On the other hand, the tensile adhesive strengths of the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 3 ranged from 10.1 N (Comparative Example 3) to 20.1 N (Comparative Example 1), and the tensile adhesive strength The strength was within a reasonable range.

From the results shown in Table 9, it is clear that the electrodes of Examples 3, 4, and 20 to 22 of the present embodiment have better migration resistance than Comparative Example 1.

Comparing the SEM photographs of Example 3 shown in FIGS. 5 and 6 and Comparative Example 1 shown in FIGS. 9 and 10, it is found that in Comparative Example 1, larger crystals of silver sulfide 20 were formed due to sulfidation than in Example 3. I can understand that. In FIG. 10 of Comparative Example 1, it can also be seen that voids 30 are generated in a part of the electrode 10. Furthermore, from the EDS analysis results of Comparative Example 1 shown in FIGS. 11 and 12 and Example 3 shown in FIGS. I can understand what is being formed. Therefore, it can be said that the electrode of the example of this embodiment has higher sulfidation resistance than that of the comparative example.

10 Electrode 20 Silver sulfide 30 Void 50 Test piece for sulfidation resistance test 52 Alumina substrate for sulfidation resistance test 54 Printed pattern for sulfidation resistance test 54a, 54b Edge of printed pattern for sulfidation resistance test 60 Test for migration resistance test Piece 62 Alumina substrate for migration resistance test 64a, 64b Printed pattern for migration resistance test 66a First electrode 66b Second electrode 100 Chip resistor 102 Alumina substrate 104 Resistor 106 Takeout electrode 108 Bottom electrode 110 Connection electrode 112 Nickel plating film 114 Tin Plating film

Claims (12)

1. (A) conductive particles;
   (B) A conductive paste containing a binder resin,
   (A) the conductive particles include surface-treated metal particles,
   The surface-treated metal particles include metal particles and a surface treatment layer disposed on at least a portion of the surface of the metal particles,
   A conductive paste, wherein the surface treatment layer contains a zinc compound.
2. The conductive paste according to claim 1, wherein the zinc content contained in the surface-treated metal particles is 10 to 1000 ppm.
3. The conductive paste according to claim 1 or 2, wherein the surface treatment layer further contains an organic substance.
4. The conductive paste according to any one of claims 1 to 3, wherein the metal particles contain 50% by weight or more of silver.
5. The conductive paste according to any one of claims 1 to 4, wherein the conductive particles (A) have an average particle diameter (D50) of 0.5 to 10 μm.
6. The conductive paste according to any one of claims 1 to 5, wherein the content of the (B) binder resin is 0.1 to 30 parts by weight based on 100 parts by weight of the (A) conductive particles. .
7. The conductive paste according to any one of claims 1 to 6, wherein the conductive paste further contains (C) glass frit.
8. The conductive paste according to claim 7, wherein the glass frit (C) contains ZnO.
9. The conductive paste according to claim 7 or 8, wherein the content of the (C) glass frit in the conductive paste is 0.05 to 10 parts by weight based on 100 parts by weight of the (A) conductive particles.
10. An electrode obtained by firing or heat-treating the conductive paste according to any one of claims 1 to 9.
11. The electrode according to claim 10, wherein the electrode contains 0.1 to 10% by weight of zinc.
12. An electronic component or electronic device comprising the electrode according to claim 10 or 11.