WO2024042873A1

WO2024042873A1 - Conductive paste, electrode, electronic component, and electronic device

Info

Publication number: WO2024042873A1
Application number: PCT/JP2023/024746
Authority: WO
Inventors: 喜昭吉井; 滉平森
Original assignee: ナミックス株式会社
Priority date: 2022-08-26
Filing date: 2023-07-04
Publication date: 2024-02-29
Also published as: TWI830643B; WO2024042872A1; WO2024042764A1

Abstract

Provided is a conductive paste comprising conductive particles (A), binder resin (B), and glass frits (C), wherein the conductive particles (A) have metal particles and a surface treatment layer containing a palladium compound, the surface treatment layer being placed on at least a part of the surface of the metal particles. The softening point of the glass frits (C) is 800 °C or below. Even when containing glass frits with a low softening point, this conductive paste can suppress outflow of glass components from an electrode during firing, and exhibits excellent sulfidation resistance.

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.

Electrodes are formed using conductive paste by firing the paste as described above, but due to the diversification of components due to the high performance of electronic devices and electronic components in recent years, consideration for environmental impact, productivity, etc. There is a need for the development of conductive pastes that can be fired at low temperatures. One method for enabling low-temperature firing is a technique in which a glass component having a low softening point, such as a Bi ₂ O ₃ -B ₂ O ₃ system, is included in the paste (Patent Document 3).

Japanese Patent Application Publication No. 7-335402 International Publication No. 2021/145269 Japanese Patent Application Publication No. 2007-273178

The method of firing conductive paste at low temperatures reduces the thermal load on other electronic components such as adherends, and also reduces energy costs, making it an advantageous method for manufacturing high-definition electronic components. be. However, since the glass component with a low softening point as used in Patent Document 3 has high fluidity, it flows out to electronic components such as substrates that are adherends during firing. When the glass component flows out, the plating is applied to that area, causing a phenomenon called plating elongation in which the plating precipitates outside the electrode. Furthermore, since the glass component flows out together with the conductive particles in the paste, short circuits and migration may occur at the point where the glass component flows out.

In addition to the outflow of glass components, the conductive paste may also contain factors that can cause electrode short-circuits. BACKGROUND ART Large amounts of sulfur oxides are emitted into the atmosphere due to the combustion of fossil fuels in gasoline vehicles, thermal power plants, and the like. 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.

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 require highly sulfidation-resistant electrodes.

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, in view of the above problems, the present invention is capable of suppressing the outflow of glass components from the electrode during firing even when containing a glass frit with a low softening point, and has excellent sulfidation resistance. The purpose is to provide a conductive paste.

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

(Configuration 1)
Configuration 1 includes (A) conductive particles;
(B) a binder resin;
(C) A conductive paste containing glass frit,
The conductive particles of (A) have metal particles and a surface treatment layer containing a palladium compound disposed on at least a portion of the surface of the metal particles,
The softening point of the glass frit (C) is 800°C or less,
It is a conductive paste.

(Configuration 2)
Structure 2 is the conductive paste of Structure 1, in which the content of the palladium compound contained in the surface treatment layer is 0.01 to 1.0 parts by weight based on 100 parts by weight of the metal particles.

(Configuration 3)
Structure 3 is the conductive paste of Structure 1 or 2, in which 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 according to any one of Configurations 1 to 4, in which the conductive particles (A) have an average particle diameter (D50) of 0.1 to 10 μm.

(Configuration 6)
Configuration 6 is the conductive paste of Configuration 5, in which the conductive particles (A) have an average particle diameter (D50) of 0.1 to 6 μm.

(Configuration 7)
Structure 7 is an electrode obtained by firing or heat-treating the conductive paste of any of Structures 1 to 6 above.

(Configuration 8)
Configuration 8 is an electronic component or electronic device that includes the electrode of Configuration 7.

ADVANTAGE OF THE INVENTION According to the present invention, there is provided a conductive paste that can suppress the outflow of glass components from the electrode during firing even when it contains a glass frit with a low softening point, and has excellent sulfidation resistance. be able to.

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 print pattern of the test piece for the migration resistance test of an Example and a comparative example. 4 is an optical microscope photograph showing an enlarged view of the center of the optical microscope photograph of the test print pattern 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). A scanning electron microscope (SEM) photograph 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 ( (magnification: 5000 times). FIG. 3 is a diagram showing changes over time in insulation resistance values of Example 1, Example 3, and Comparative Example 1 when an anti-migration test was conducted. This is a backscattered electron image (magnification: 500 times) taken by SEM of the side surface of the electrode thick film after firing in Examples 20 and 23 and Comparative Examples 6 and 9.

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, (B) a binder resin, and (C) a glass frit with a softening point of 800° C. or less. The conductive paste of this embodiment can be preferably used to form electrodes of electronic components such as chip resistors. (A) The conductive particles include metal particles and a surface treatment layer containing a palladium compound, which is disposed on at least a portion of the surface of the metal particles.

First, 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 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 palladium compound. The surface treatment layer is formed by surface treating metal particles with the palladium compound. (A) It is thought that by having the conductive particles with a surface treatment layer, the sintering speed can be controlled appropriately, so that the glass frit can be held without flowing out during the firing process. Moreover, (A) conductive particles containing predetermined surface-treated metal particles can suppress sulfidation of the metal contained in the conductive particles. 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. Further, 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 will be no dendrites between the wiring parts, which are always seen when migration occurs in the presence of moisture, and no polarity will be 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. 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 that has low electrical resistance, suppresses outflow of the glass frit during firing, and has high sulfidation resistance, (A) conductive particles should contain 50% by weight of surface-treated metal particles. It is preferable to contain 80% by weight or more of surface-treated metal particles, still more preferably to contain 90% by weight or more of surface-treated metal particles, and it is particularly preferable to contain only 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 palladium 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 palladium compound.

As the material of the metal particles whose surface is treated with a palladium 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, it is possible to form an electrode at relatively low cost while having high sulfidation resistance and sufficiently exhibiting the effect of suppressing outflow of glass frit.

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 palladium compound.

Palladium compounds that serve as raw materials for surface treatment of metal particles include palladium (II) chloride, palladium (II) oxide, organic palladium compounds, palladium fluoride, palladium on carbon, n-allyl palladium complex, cyclopentadienyl allyl palladium. , dichlorobis(triphenylphosphine)palladium (II), palladium bromide, and palladium complexes such as palladium fatty acid complexes such as palladium oleate. It is preferable to use palladium chloride as a palladium compound that is a raw material for surface treating metal particles.

The surface treatment layer can be formed by surface treatment using a palladium compound by a known method. Specifically, the surface treatment layer is formed by attaching a palladium soap solvent (surface treatment agent) containing palladium or palladium ions, an organic substance for dispersing these, and a solvent to the surface of the metal particles, and then applying the palladium soap solvent (surface treatment agent) containing palladium or palladium ions, an organic substance for dispersing these, and a solvent to the surface of the metal particles. , with the solvent removed. Thereby, a surface treatment layer containing a palladium 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. In order to deposit a shell (for example, palladium metal particles) on the surface of silver particles, the amount of palladium metal particles present in the shell increases. In other words, the amount of palladium used increases. On the other hand, in the present invention, since the surface treatment layer is formed with the palladium compound attached to the surface of the metal particles, the effect is that only a small amount of palladium is required. Palladium is an expensive metal due to its rarity and uneven distribution, and even in small amounts it has excellent sulfidation resistance, and the ability to suppress the outflow of glass components is an extremely important effect from a cost perspective.

The organic substance for dispersing palladium or palladium ions is preferably at least one selected from fatty acids and triazole compounds. When a fatty acid is used as a solvent, examples of the fatty acid 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, and stearic acid. acids, 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 At least one selected from melisic acid and the like 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 palladium or palladium 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 that can be used to disperse palladium or palladium ions and to properly adhere the palladium 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 palladium 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 palladium 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 palladium, 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 palladium 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 palladium 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 palladium compound. This embodiment is characterized in that the surface treatment layer of the surface treatment metal particles is not a thin film made of palladium metal or palladium alloy. When the surface treatment layer is a thin film made of palladium metal or palladium alloy, the amount of palladium blended is too large, which may cause adverse effects such as an increase in the electrical resistance of the resulting electrode. Further, after firing, a large amount of palladium metal or palladium alloy is present on the surface of the metal particles, which deteriorates the wettability of the solder to metal particles such as silver particles, increasing the possibility that soldering will be inhibited. Moreover, if the amount of palladium used increases, the cost will be high.

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 palladium soap solvent (surface treatment agent) in which the palladium compound is dispersed, and the concentration of the palladium compound in the palladium soap solvent (surface treatment agent). It can be controlled by adjusting. Further, by controlling the thickness of the surface treatment layer, the amount of palladium contained 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, 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, an electrode with high sulfidation resistance can be formed while using a small amount of palladium compound.

Since the conductive paste of this embodiment contains (A) surface-treated metal particles surface-treated with a palladium compound as the conductive particles, an electrode having high sulfidation resistance can be created without using a large amount of expensive palladium. can be formed. 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) that have been surface-treated with a palladium compound is as follows. It can be inferred as follows. That is, it is presumed that palladium as a surface treatment component and metal particles form a uniform alloy layer through sintering, thereby improving the sulfidation resistance. Palladium in the palladium compound comes to exist as metal particles and a palladium metal alloy layer (if the metal particles are silver particles, a palladium-silver alloy layer) by firing at, for example, 400 to 900°C. It is believed that this palladium metal alloy layer imparts high sulfidation resistance to the metal particles. Note that the content of palladium contained in the surface treatment layer is not very large. Therefore, compared to the case where palladium particles are added separately, the amount of palladium used can be reduced, and high sulfidation resistance can be obtained at relatively low cost. The electrode thus obtained has high sulfidation resistance and excellent adhesion to the substrate. 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) whose surface has been treated with a palladium compound is that by using surface-treated metal particles whose surface has been treated with a palladium compound, migration resistance can also be improved. , while maintaining the anti-migration effect of palladium, the density of the electrode is also improved. It is presumed that this improves migration resistance. However, the present invention is not limited to this inference.

In the conductive paste of the present embodiment, the content of palladium contained in the surface-treated metal particles is preferably 0.01 parts by weight or more, and preferably 0.05 parts by weight or more, based on 100 parts by weight of the metal particles. The amount is more preferably 0.08 parts by weight or more, and particularly preferably 0.08 parts by weight or more. Further, the palladium content is preferably 1.0 parts by weight or less, more preferably 0.8 parts by weight or less, and 0.6 parts by weight or less based on 100 parts by weight of the metal particles. is more preferable, particularly preferably 0.4 parts by weight or less, and most preferably 0.3 parts by weight or less. When the content of palladium contained in the surface-treated metal particles is within the above range, the amount of palladium used is small, and the change in resistance value of the electrode due to sulfidation of the electrode can be reduced while the cost is low. Note that the content of palladium 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.

(A) The average particle size of the conductive particles is preferably 0.1 μm to 10 μm, more preferably 0.2 μm to 8 μm, even more preferably 0.3 μm to 7 μm, particularly preferably 0.4 to 6 μm. It is. 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 0.1 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.

Since 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 then baked at, for example, 400 to 900°C. Accordingly, electrodes can be formed. In this case, the binder resin (B) is burned out during firing. Therefore, the function of (B) the binder resin is to (A) connect the conductive particles when the conductive paste of this embodiment is applied to a predetermined base material to form a predetermined electrode pattern. .

(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.

The conductive paste of this embodiment may contain an epoxy resin as the binder resin (B) in order to improve the adhesion between the surface-treated metal particles. 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 0.1 to 30 parts by weight, more preferably 0.5 to 15 parts by weight, and The amount is preferably 1 to 10 parts by weight, particularly preferably 1.5 to 8 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 further includes (C) glass frit. Electrodes can be formed by applying the conductive paste of this embodiment to a predetermined base material so as to form a predetermined electrode pattern, and firing at, for example, 400 to 900°C. 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 as long as it has a softening point of 800°C or lower, but preferably has a softening point of 250°C or higher, more preferably a softening point of 250 to 800°C, and even more preferably a softening point of 250 to 750°C. ℃, particularly preferably a glass frit with a softening point of 300°C to 700°C. By using a glass frit with a softening point of 800° C. or lower, firing can be performed at a relatively low temperature. However, a glass frit having a softening point of 800° C. or higher can also be used in combination without impairing the effects of the present invention. 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 .

It is further preferable that the glass frit contains 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.

More preferably, the glass frit contains Bi ₂ O ₃ . When a glass frit containing Bi ₂ O ₃ (bismuth-based glass frit) is used as the glass frit, the denseness 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, particularly 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.

The content of (C) glass frit is preferably 0.05 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, and 1 It is more preferably 6 parts by weight, and particularly preferably 2 to 4 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 contains zinc oxide as the glass frit (C), the Zn component in the glass frit precipitates as ZnO at the crystallization temperature. At this time, since the crystallized glass component forms a precipitated state on the surface of the fired body, the glass frit affects the sulfidation resistance of (A) conductive particles after firing, similar to the palladium in the surface-treated metal particles. It is possible to contribute to this.

<(D) Additive>
The conductive paste of this embodiment can contain a dispersant as the (D) additive. By including the dispersant in the conductive paste of this embodiment, the dispersibility of (A) conductive particles in the conductive paste can be improved, and (A) conductive particles can be prevented from agglomerating. can.

As the dispersant, a known dispersant can be used. As the dispersant, for example, a fatty acid amide, an acid type low molecular dispersant, or bismuth oxide (Bi ₂ O ₃ ) can be used.

The conductive paste of the present embodiment can contain organic additives, inorganic additives, and the like as (D) additives other than the dispersant. (D) As the additive, for example, silica filler, rheology modifier, and/or pigment can be used.

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

<(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 N,N-dimethylformamide (DMF), amides 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>
The conductive paste of this embodiment may further contain (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 (B) epoxy resin as a binder resin is 100 parts by weight, the conductive paste contains (F) 0 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.

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.

Electrodes can be formed by applying the conductive paste of the present embodiment to a predetermined base material so as to form a predetermined electrode pattern, and baking the paste at, for example, 400 to 900° C. in an air atmosphere. Therefore, since the conductive paste of the present embodiment includes (C) glass frit, the formed electrode is made of (A') conductive particles containing surface-treated metal particles and (C) glass frit. C') 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, for example, 400 to 900° C., the binder resin (B) and the solvent (E) contained in the conductive paste are vaporized or burned during firing. Therefore, the electrode does not substantially contain (B) binder resin and (E) solvent.

Since the surface-treated metal particles contained in the conductive paste of this embodiment are surface-treated with a palladium compound, the electrode of this embodiment contains palladium. The electrode of this embodiment preferably contains 0.01 to 10% by weight of palladium, more preferably 0.05 to 5% by weight of palladium, and even more preferably 0.07 to 1% by weight of palladium. , it is particularly preferable to contain palladium in an amount of 0.08 to 0.5% by weight. In addition, when the electrically conductive paste of this embodiment contains (C) glass frit, the electrode of this embodiment can contain palladium resulting from (C) glass frit. Since the electrode of this embodiment contains a predetermined amount of palladium, the electrode of this embodiment can have high sulfidation resistance. Note that the palladium content in the electrode can be measured by elemental analysis using EDS (Energy Dispersive X-ray Spectroscopy).

The electrode of this embodiment can include (C) zinc (zinc oxide) resulting from the glass frit. Since the electrode of this embodiment contains zinc in addition to palladium, high sulfidation resistance can be obtained.

Although the sheet resistance of the thin film serving as the electrode of this embodiment varies depending on the film thickness, it can be approximately 10 mΩ/□ (10 mΩ/square) or less than 10 mΩ/□. 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.

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 400 to 900°C, more preferably 500 to 880°C, and still more preferably 500 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. In addition, the organic components contained in the surface-treated metal particles disappear by firing in an air atmosphere, and the palladium in the palladium compound is formed by forming a palladium metal alloy layer on the surface of the metal particles (if the metal particles are silver particles, palladium - silver alloy layer). It is believed that the palladium metal alloy layer on the surface of the metal particles imparts high sulfidation resistance to the metal particles. Therefore, high sulfidation resistance can be obtained when the metal particles include a thin film surface treatment layer containing a palladium compound. Further, the content of palladium contained in the surface treatment layer is not very large. Therefore, compared to the case where palladium particles are added separately, the amount of palladium used can be reduced, and high sulfidation resistance can be obtained at relatively low cost. The electrode thus obtained has high sulfidation resistance and excellent adhesion to the substrate.

Even after the electrode obtained using the conductive paste of this embodiment is fired using the method described above, there is little flow out of glass components, etc., and problems such as plating elongation and short circuits are less likely to occur. In particular, in conventional conductive pastes, when only small metal particles (1 μm or less) are used as conductive particles, the glass component of the glass frit, which has a low softening point, is Being pushed outside could be one of the reasons for the outflow. On the other hand, in the conductive paste of this embodiment, it is presumed that the presence of the surface treatment layer of the metal particles slows down the sintering speed and allows the glass component to be retained in the electrode. The outflow of the glass component can be observed using a device such as a scanning electron microscope (SEM).

Furthermore, the electrode obtained as described above using the conductive paste of this embodiment can have the additional advantage of improved migration resistance. 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. Further, the conductive paste of this embodiment is not limited to forming terminal electrodes of chip resistors, but can also be suitably used 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 (E) in the proportions shown in Tables 1 and 2. In addition, all the proportions of each component shown in Tables 1 and 2 are shown in parts by weight. In Tables 1 and 2, 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 3 shows metal particles a1 to a4 and surface-treated metal particles A1 to A6 used as (A) conductive particles (component (A)) in Examples and Comparative Examples. Metal particles a1 and a2 are silver particles, and metal particle a4 is a palladium particle. Metal particles a1 to a4 are not surface-treated. Surface-treated metal particles A1 to A6 are produced by attaching a palladium soap solvent (surface treatment agent) in which a palladium 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 A6 have a surface-treated layer containing a palladium compound. In the "Pd content" column of Table 3, the weight ratio of palladium contained in the surface treatment layer to the weight of the surface treatment metal particles A1 to A6 is shown in units of weight %. The weight proportion of palladium in the surface-treated metal particles was measured by ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy).

Surface treatment of silver particles with a palladium compound was performed as follows. That is, the surface treatment of the silver particles with a palladium compound was performed using a palladium soap solvent (surface treatment agent) containing a palladium compound, an organic substance for dispersing these, and a solvent. The surface treatment was performed by attaching a palladium soap solvent (surface treatment agent) to the surface of the silver particles and removing the solvent through a drying process. Palladium chloride was used as the palladium compound. Furthermore, oleic acid was used as the solvent contained in the silver particle surface treatment agent. As described above, surface treatment layers were formed on the surface treatment metal particles A1 to A6.

(B) Binder resin Table 4 shows the (B) binder resins (resins B1 and B2) used in the Examples and Comparative Examples. Tables 1 and 2 show the blending amounts of resins B1 and B2 in the conductive pastes of Examples and Comparative Examples.

(C) Glass Frit Table 5 shows the (C) glass frits (C1 to C8) used in the Examples and Comparative Examples. Tables 1, 2, and 9 show the blending amounts of glass frits C1 to C8 in the conductive pastes of Examples and Comparative Examples.

(D) Additives Table 6 shows the (D) additives (Additives D1 to D3) used in Examples and Comparative Examples. Tables 1 and 2 show the amounts of additives D1 to D3 in the conductive pastes of Examples and Comparative Examples. Additive D1 is an organic additive. By adding additive D1, the printability of the conductive paste can be improved. Additive D2 is a dispersant. By adding additive D2, the dispersibility of (A) conductive particles and the like can be improved. Additive D3 is an inorganic additive. By adding additive D3, the adhesion of the conductive paste after firing can be improved.

(E) Solvents Table 7 shows the (E) solvents (solvents E1 to E3) used in the Examples and Comparative Examples. Tables 1 and 2 show the amounts of solvents E1 to E3 in the conductive pastes of Examples and Comparative Examples.

[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) Test pieces 50 for sulfidation resistance tests of Examples 1 to 16 and Comparative Examples 1 to 5 were prepared using a conductive paste containing glass frit 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 16 and Comparative Examples 1 to 5 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 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 and 2, 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 16 and Comparative Examples 1 to 5 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 16 and Comparative Examples 1 to 5 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.

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 and 2 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 1 and 3 and Comparative Example 1 were prepared according to the following procedure.

Test pieces 60 for the migration resistance test of Examples 1 and 3 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 1 to 16 and Comparative Examples 1 to 5 were prepared.

The migration resistance of the printed patterns 64a and 64b for migration resistance test of the test piece 60 of Examples 1 and 3 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 487 hours. Table 8 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 10 hours was judged to be defective, and was written as "defective" in Table 8. Test piece 60 whose insulation resistance value did not fall below 10 ⁶ Ω even after 80 hours was judged to have a certain degree of migration resistance and could be used for some purposes, and was marked as "usable" in Table 8. It was written as. Test piece 60 whose insulation resistance value did not fall below 10 ⁶ Ω even after 487 hours was judged to have excellent migration resistance and was listed as "good" in Table 8.

FIG. 7 shows changes over time in the insulation resistance values of Example 1, Example 3, and Comparative Example 1 when an anti-migration test was conducted. Test piece 60 of Example 3, which was determined to have excellent migration resistance (described as "good" in Table 8), did not have an insulation resistance value of 10 ⁶ Ω or less even after 480 hours. Test piece 60 of Example 1 (described as "usable" in Table 8), which was determined to be usable for some applications because of its excellent migration resistance to some extent, had an insulation resistance value of 10 even after 80 hours. It did not go below ⁶ Ω. Test piece 60 of Comparative Example 1, which was determined to have poor migration resistance (described as "defective" in Table 8), had an insulation resistance value of 10 ⁶ Ω or less within 10 hours.

[Solder heat resistance test]
Using the prepared conductive paste, test pieces for the soldering heat resistance test of Examples 1 to 16 and Comparative Examples 1 to 5 containing (C) glass frit were prepared 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, a solder bath (solder temperature: 260°C) containing 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 tested. The pieces were immersed for 10 seconds.

After immersing the test piece in the solder bath, the test piece was taken out, and if 95% or more of the electrode remained on the test piece, it was judged as having passed the soldering heat resistance test. In the "soldering heat resistance" column of Tables 1 and 2, "good" was written when the soldering heat resistance test was passed, and "poor" was written when the soldering heat resistance test was failed.

[Surface and cross-sectional observation by SEM, and cross-sectional observation by EDS analysis]
Figure 5 shows the surface 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, using a scanning electron microscope (SEM) at a magnification of 5000 times. This shows an SEM photograph taken by. FIG. 6 shows an SEM photograph taken at a magnification of 5000 times of the surface 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. 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.

[evaluation]
As is clear from the results shown in Tables 1 and 2, the electrode patterns obtained by firing the conductive pastes of Examples 1 to 16 had a resistance change rate of 65.0% or less (Example 11). , was relatively low. In contrast, the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 5 had a resistance change rate of 140% or more (Comparative Example 5). Therefore, it can be said that the electrode patterns obtained by firing the conductive pastes of Examples 1 to 16 have excellent sulfidation resistance.

As is clear from the results shown in Tables 1 and 2, the tensile adhesive strength of the adhesive strength test patterns obtained by firing the conductive pastes of Examples 1 to 16 was at most 17.8N (Example 11 and 15), and high tensile adhesive strength could be obtained. On the other hand, the tensile adhesive strength of the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 4 was in the range of 14.2 N (Comparative Example 4) to 15.2 N (Comparative Examples 1 to 3), The tensile adhesive strength was within a acceptable range. Further, the tensile adhesive strength of the electrode pattern obtained by firing the conductive paste of Comparative Example 5 was 7.1N. It is considered that the conductive paste of Comparative Example 5 had a lower tensile adhesive strength because it had poor sinterability compared to other Examples and Comparative Examples.

As is clear from the results shown in Tables 1 and 2, the results of the soldering heat resistance test for the electrode patterns obtained by firing the conductive pastes of Examples 1 to 16 were all passed ("good"). On the other hand, the results of the soldering heat resistance test of the electrode patterns obtained by firing the conductive pastes of Comparative Examples 1 to 4 were failures ("poor"). In addition, the result of the soldering heat resistance test of the electrode pattern obtained by baking the conductive paste of Comparative Example 5 was a pass ("good"). From the above, it can be said that the electrode patterns obtained by firing the conductive pastes of Examples 1 to 16 have excellent solder heat resistance.

From the results shown in Table 8, it is clear that the electrodes of Examples 1 and 3 of the present embodiment have better migration resistance than Comparative Example 1.

Comparing the SEM photographs of Example 3 shown in FIG. 5 and Comparative Example 1 shown in FIG. 6, it can be seen that the crystals of silver sulfide 20 are formed larger due to sulfidation in Comparative Example 1 than in Example 3. . Similar trends were observed for other Examples and Comparative Examples. Therefore, it can be said that the electrode of the example of this embodiment has higher sulfidation resistance than that of the comparative example. Furthermore, when the Pd content in the depth direction of the sample of Example 3 was measured by X-ray photoelectron spectroscopy (XPS), it was found that there was a portion with a Pd content of about 30 at.% at a depth of 80 nm. confirmed. This suggests that at least in the sample of Example 3, the sulfidation resistance of the electrode was improved by forming a silver-palladium alloy layer on the surface of the electrode.

<Examples 17 to 29, Comparative Examples 6 to 9: Evaluation of outflow of glass components>
A conductive paste was prepared in the same manner as in Example 1 using the formulation shown in Table 9. Next, the conductive paste of each example and comparative example was applied to the alumina substrate in a pattern of width 1 mm and length 71 mm to a thickness of approximately 15 μm, and dried at 150° C. for 10 minutes. , and was fired at 850° C. for 60 minutes to form a conductive thick film having a thickness of 10 μm after firing. A backscattered electron image of the electrode side surface of the obtained conductive thick film was taken using a scanning electron microscope (SEM) at a magnification of 500 times, and the length of the glass flow was measured. The silver component flowing with the glass during firing appears white in the backscattered electron image, so the area where the glass flows out is observed as a black and white mottled pattern (Figure 8). It was defined as. When the length of the glass flow was 40 μm or less, there was little outflow (judgment: ○). Table 9 shows the formulations and measurement results of each Example and Comparative Example, together with the measurement results of sulfidation resistance.

[evaluation]
In the conductive paste of the comparative example, it was confirmed that glass flowed out, and the results of the sulfidation resistance test also showed that the resistance value increased significantly, and there remained concerns about short circuits and disconnections. On the other hand, the conductive pastes of Examples 17 to 29 exhibit high sulfidation resistance, and unlike Comparative Example 7 and Example 19, when the same glass frit is used, the glass components do not flow out during firing. It was shown that even if a glass frit with a low softening point is used, an electrode with less concern about short circuits can be obtained.

50 Test piece for sulfidation resistance test 52 Alumina substrate for sulfidation resistance test 54 Printed pattern for sulfidation resistance test 54a, 54b Edges of printed pattern for sulfidation resistance test 60 Test piece for migration resistance test 62 Alumina for migration resistance test Substrate 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

(A) conductive particles;
(B) a binder resin;
(C) A conductive paste containing glass frit,
The conductive particles of (A) have metal particles and a surface treatment layer containing a palladium compound disposed on at least a part of the surface of the metal particles,
The softening point of the glass frit (C) is 800°C or less,
conductive paste.
The conductive paste according to claim 1, wherein the content of the palladium compound contained in the surface treatment layer is 0.01 to 1.0 parts by weight based on 100 parts by weight of the metal particles.
The conductive paste according to claim 1 or 2, wherein the surface treatment layer further contains an organic substance.
The conductive paste according to any one of claims 1 to 3, wherein the metal particles contain 50% by weight or more of silver.
The conductive paste according to any one of claims 1 to 4, wherein the conductive particles (A) have an average particle diameter (D50) of 0.1 to 10 μm.
The conductive paste according to claim 5, wherein the conductive particles (A) have an average particle diameter (D50) of 0.1 to 6 μm.
An electrode obtained by firing or heat treating the conductive paste according to any one of claims 1 to 6.
An electronic component or electronic device comprising the electrode according to claim 7.