KR20210048503A - Conductive paste - Google Patents

Abstract

The conductive paste of the present invention comprises a metal powder containing copper; Glass composition; And an organic vehicle, wherein the glass composition contains sulfur (S), and the content of the sulfur (S) is 10 ppm or more and 370 ppm or less with respect to the metal powder. According to the present invention, it is possible to appropriately control the firing behavior of a single metal powder containing copper, and as a result, a conductive paste having a wide firing window and less likely to cause problems such as voids or glass lift after firing can be provided.

Description

Conductive paste

The present invention relates to a conductive paste using a metal powder containing copper as a main component as a conductive component.

For example, when forming an external electrode of a multilayer ceramic electronic component such as a multilayer ceramic capacitor or a multilayer ceramic inductor, a conductive paste including a conductive powder, a glass composition, and an organic vehicle is used.

As the conductive powder, metal powder such as silver (Ag) or palladium (Pd) has been used in the past, but recently, from the viewpoint of excellent conductivity and production cost, a conductive paste containing a metal powder including copper (Cu) (hereinafter, referred to as Copper paste) is particularly widely used.

To form external electrodes of multilayer ceramic electronic components using copper paste, in general, first, a chip-shaped laminate in which dielectric layers and internal electrode layers are alternately stacked is prepared, and a method suitable for the cross section (e.g., dipping printing method or screen The copper paste is applied by printing method). Thereafter, the metal powder containing copper is fired in an atmosphere where it is difficult to oxidize, and the organic components in the paste are scattered and decomposed, and then the glass is fluidized and the metal particles containing copper are sintered to form an external electrode. At this time, the heating temperature range suitable for firing is determined according to the type or formulation of metal powder or glass composition, organic vehicle, and other additives contained in the paste.

Further, a plating layer such as tin or nickel is formed on the surface of the formed external electrode for the purpose of improving electrode reliability or facilitating solder mounting.

However, when the conventional copper paste is applied to the end surface of the chip-shaped laminate and then fired, if the temperature range suitable for the firing (hereinafter, "firing window") is narrow, it is likely to be oversintered due to temperature irregularity in the firing furnace or slight temperature change. Had a problem. When oversintering is performed, the glass component is exposed due to the rapid contraction of the metal powder containing copper, and the so-called "glass lift" may occur in which the glass component is ubiquitous on the surface portion of the pattern after firing. Due to the occurrence of such glass lifting, adhesion between the fired pattern and various metals such as tin and nickel decreases, making it difficult to form a plating layer or the like.

In order to suppress the occurrence of such glass lifting, a method of lowering the sintering temperature so that over-sintering does not occur can be considered. However, since the firing window is narrow, in this case, the compactness of the fired film (electrode) is lowered, and voids (voids) are generated in the film. As a result, not only the conductivity of the electrode and the adhesive strength with the ceramic body are deteriorated, but also when the plating treatment is performed on the fired film in the subsequent process, the plating solution penetrates into the film, causing a decrease in insulation resistance or occurrence of a body crack. The plating solution is heated and gasified during solder reflow and may cause a "solder burst" in which the molten solder scatters.

On the other hand, in order to control the sintering behavior of the metal powder, a method of applying a specific surface treatment to the surface of the metal powder has been tried from the past. For example, in Patent Document 1, in order to control the sintering initiation temperature, a method of attaching any one element of Al, Si, Ti, Zr, Ce, and Sn to the surface of the copper powder was attempted. In addition, Patent Document 2 describes that the catalytic action of the metal powder can be effectively suppressed by coating the surface of the metal powder of any one of nickel, silver, copper, and palladium with a metal compound containing sulfur.

However, according to the review of the present inventors, if such a surface treatment is performed on a metal powder containing copper, the influence on the firing behavior of a single metal powder containing copper is excessively large, and the sintering start temperature can be controlled. However, there are cases where the firing window is narrowed, and these conditions need to be changed drastically in the copper paste firing temperature or firing atmosphere without surface treatment. In this case, not only the design of the paste has to be reviewed from the beginning, but the overall cost of the paste increases due to the characteristics or restrictions of the raw materials or materials that can be used for the paste, or in some cases, it is often necessary to review the production line such as a kiln. not.

Japanese Patent Application Publication No. 2016-033850 Japanese Patent Application Publication No. 2014-005491

An object of the present invention is to provide a conductive paste that suitably controls the firing behavior of a single metal powder containing copper, and as a result, has a wide firing window and is unlikely to cause problems such as voids or glass lift after firing.

This object is achieved through the present invention described in the following (1) to (6).

(1) metal powder containing copper; Glass composition; And as a conductive paste containing an organic vehicle,

The conductive paste, wherein the glass composition contains sulfur (S), and the sulfur (S) content is 10 ppm or more and 370 ppm or less with respect to the metal powder.

(2) metal powder containing copper; Glass composition; Organic vehicle; And as a conductive paste containing an inorganic additive,

The conductive paste, wherein the inorganic additive contains sulfur (S), and the sulfur (S) content is 10 ppm or more and 370 ppm or less with respect to the metal powder.

(3) The conductive paste according to (2), wherein the inorganic additive is a sulfate.

(4) metal powder containing copper; Glass composition; Organic vehicle; And as a conductive paste containing an organic additive,

The organic additive has a thiol group, and the content of sulfur (S) in the organic additive is 10 ppm or more and 370 ppm or less with respect to the metal powder.

(5) The conductive paste according to any one of (1) to (4), wherein the metal powder is a copper powder.

(6) The conductive paste according to any one of (1) to (5), wherein the content of sulfur (S) contained in the metal powder is less than 10 ppm.

According to the present invention, it is possible to provide a conductive paste in which voids are less likely to occur in the fired film when fired, and adverse effects due to oversintering are less likely to occur.

Hereinafter, preferred embodiments of the present invention will be described in detail.

[Conductive paste]

1. First embodiment

A conductive paste according to a preferred embodiment of the present invention includes a metal powder containing copper; Glass composition; And an organic vehicle, wherein the glass composition contains sulfur (S), and the sulfur content is 10 ppm or more and 370 ppm or less with respect to the metal powder.

With this configuration, as a conductive paste containing copper, the fluctuation of the firing behavior is small compared to the case of surface treatment on the metal powder itself containing copper, the firing behavior can be appropriately controlled throughout the copper paste, and the firing window is wide. , It is possible to provide a conductive paste that is unlikely to cause problems such as voids or glass lift after firing.

It is thought that it is because of the following reason that such an excellent effect is obtained. That is, compared to the case where sulfur (S) was mixed with the metal powder or the sulfur compound was coated on the surface of the metal powder in the conventional example, the sulfur contained in the glass composition after the glass composition in the conductive paste began to flow during firing. Since this acts on copper constituting the metal powder, as a result, the present inventors speculate that the sintering behavior of the metal powder is gently controlled.

2. Second embodiment

In addition, the conductive paste according to another preferred embodiment of the present invention includes a metal powder containing copper; Glass composition; Organic vehicle; And an inorganic additive, wherein the inorganic additive contains sulfur, and the sulfur content is 10 ppm or more and 370 ppm or less with respect to the metal powder.

With this configuration, as a conductive paste containing copper, the fluctuation of the firing behavior is small compared to the case of surface treatment on the metal powder itself containing copper, the firing behavior can be appropriately controlled throughout the copper paste, and the firing window is wide. , It is possible to provide a conductive paste that is unlikely to cause problems such as voids or glass lift after firing.

It is thought that it is because of the following reason that such an excellent effect is obtained. That is, compared to the case in which sulfur (S) was mixed with the metal powder or the sulfur compound was coated on the surface of the metal powder in the conventional example, the glass composition in the conductive paste began to flow during firing, and then the sulfur constituting the inorganic additive was once. Since the sulfur dissolved in the glass composition and then dissolved in the glass composition acts on the copper constituting the metal powder, the present inventors estimate that the sintering behavior of the metal powder is gently controlled as a result.

3. Third embodiment

In addition, the conductive paste according to another preferred embodiment of the present invention includes a metal powder containing copper; Glass composition; Organic vehicle; And an organic additive, wherein the organic additive has a thiol group, and the content of sulfur in the organic additive is 10 ppm or more and 370 ppm or less with respect to the metal powder.

With this configuration, as a conductive paste containing copper, the fluctuation of the firing behavior is small compared to the case of surface treatment on the metal powder itself containing copper, the firing behavior can be appropriately controlled throughout the copper paste, and the firing window is wide. , It is possible to provide a conductive paste that is unlikely to cause problems such as voids or glass lift after firing.

It is thought that it is because of the following reason that such an excellent effect is obtained. That is, compared to the case in which sulfur (S) was mixed with the metal powder or the sulfur compound was coated on the surface of the metal powder in the conventional example, after the glass composition in the conductive paste began to flow during firing, the sulfur constituting the organic additive was The present inventors speculate that the sintering behavior of the metal powder is gently controlled as a result, since the sulfur dissolved in the glass composition once and then dissolved in the glass composition acts on the copper constituting the metal powder. .

Among the above embodiments, the glass composition of the first embodiment contains a predetermined amount of sulfur, or the inorganic additive of the second embodiment contains a predetermined amount of sulfur (especially, the glass composition contains a predetermined amount of sulfur. The form) is advantageous in that the compactness of the fired film is particularly excellent even when fired at a relatively low temperature (for example, 750°C), and the firing temperature range (firing window) for forming a preferred fired film is particularly wide. . In the present invention, the first embodiment is particularly preferred. On the other hand, in the case of the third embodiment, since the organic additive may strongly bind to the metal powder over time, environmental management including storage temperature is required.

If the above configuration is not satisfied, satisfactory results are not obtained.

For example, in the first to third embodiments, if the content of sulfur in the predetermined component of the conductive paste is less than the lower limit, adverse effects due to over-sintering during firing cannot be sufficiently prevented. In particular, when firing at a relatively high temperature (for example, 780°C or higher), adverse effects due to over-sintering are likely to occur remarkably.

In addition, in the first to third embodiments, when the content of sulfur in the predetermined component of the conductive paste exceeds the above upper limit, the occurrence of voids in the fired film during firing cannot be sufficiently prevented. In particular, when firing at a relatively low temperature (for example, 750°C or less), voids are likely to be remarkably generated in the fired film.

In addition, even if the sulfur content of the entire conductive paste is within the above range, when the sulfur content of the predetermined component does not satisfy the predetermined content condition, more specifically, when a large amount of sulfur is contained in the metal powder, the sintering start temperature of the metal powder, etc. Since the influence on the behavior is too great, the compactness of the fired film is lowered, and voids are liable to occur in the fired film.

As described above, the content of sulfur in the predetermined components (glass composition, inorganic additive, organic additive) of the conductive paste should be 10 ppm or more and 370 ppm or less with respect to the metal powder, preferably 12 ppm or more and 200 ppm or less, and 15 ppm or more and 100 ppm or less. It is particularly preferred.

Thereby, the above-described effect is more remarkably exhibited.

<Metal powder>

The conductive paste of the present invention contains a metal powder, and the metal powder contains copper.

Examples of such metal powder include pure copper powder or copper alloy powder composed of only copper. Further, it may be a metal powder having a core-shell structure in which a thin film made of copper oxide or an oxide thin film containing an element other than copper is coated on the surface of the copper particle as a core. It is particularly preferred that the thin film is glassy. The coating of the glassy thin film on the metal powder can be achieved, for example, by the method described in Japanese Patent No. 3206496 or the like.

Since the metal powder has a core-shell structure having the thin film, oxidation of the metal powder can be suppressed or the sintering start temperature of the metal powder can be controlled.

Sulfur is not included in the above-described thin film made of copper oxide or oxide thin film containing elements other than copper, but if the thin film is glassy, sulfur may be contained in the thin film. The glassy thin film not only suppresses oxidation of the metal powder, but also softens and flows during firing, and functions as a sintering aid for the metal powder. When the glassy thin film contains sulfur, the total amount of sulfur contained in other glass compositions, inorganic additives, or organic additives may be 10 ppm or more and 370 ppm or less with respect to the metal powder.

The content of the copper element (Cu) relative to the amount of all the metal elements contained in the metal powder is preferably 50% by mass or more and 100% by mass or less, and more preferably 80% by mass or more and 100% by mass or less.

The metal powder of the present invention does not contain sulfur substantially, but does not exclude a form containing sulfur as an inevitable impurity. That is, in the present invention, "the metal powder substantially does not contain sulfur" means that the content of sulfur contained in the metal powder is less than 10 ppm, more preferably less than 7 ppm, and even more preferably less than 5 ppm.

Thereby, the fluctuation of the firing behavior is small compared to the case where the surface treatment is performed on the metal powder itself containing copper, and the firing behavior can be appropriately controlled as a whole of the copper paste.

Although the average particle diameter (D ₅₀ ) of the metal powder is not particularly limited, it is preferably 0.2 µm or more and 5.0 µm or less, more preferably 0.5 µm or more and 4.5 µm or less, and still more preferably 1.0 µm or more and 4.0 µm or less.

In addition, in the present specification, the average particle diameter (D ₅₀ ) means 50% of the weight-based integrated fraction of the particle size distribution measured using a laser particle size distribution measuring device, unless otherwise noted, for example For example, it can be determined by measuring using a laser diffraction/scattering particle size distribution measuring device LA-960 (manufactured by HORIBA).

The BET specific surface area of the metal powder is not particularly limited, but it is preferably 0.30 m 2 /g or more and 1.00 m 2 /g or less, more preferably 0.40 m 2 /g or more and 0.90 m 2 /g or less, and 0.50 m 2 /g or more and 0.80 m 2 /g It is more preferable that it is the following. In addition, the BET specific surface area can be obtained using, for example, Tristar 3000 (manufactured by Shimadzu Corporation).

The content of the metal powder in the conductive paste is not particularly limited, but it is preferably 50.0% by mass or more and 80.0% by mass or less, more preferably 55.0% by mass or more and 75.0% by mass or less, and still more preferably 60.0% by mass or more and 70.0% by mass or less. .

Thereby, the electric conductivity of the fired film can be made more reliably and sufficiently excellent while sufficiently exhibiting the function of the metal powder containing copper.

In addition, it is preferable that the plurality of particles constituting the metal powder constituting the conductive paste of the present invention are metal particles having the same or uniform metal composition, but metal particles having different metal compositions may be used as long as the effect of the present invention is not impaired. You may include it. For example, the metal powder may contain a plurality of types of particles having different copper content from each other. Even in such a case, it is preferable that the total copper content of the metal powder satisfies the above-described conditions.

<Glass composition>

The glass composition contained in the conductive paste of the present invention may have any composition as long as its softening point is less than or equal to the firing temperature, but it is preferable that it is a glass composition substantially free of Pb, Cd, and Bi. _{For example, in the present invention, SiO 2} as an essential component with respect to the total amount of the glass composition in terms of oxides is in the range of 2.0% by mass or more and 12.0% by mass or less, and B ₂ O ₃ is in the range of 15.0% by mass or more and 30.0% by mass or less, Al ₂ O ₃ is contained within the range of 2.0 mass% or more and 12.0 mass% or less, and BaO as other optional components is 40.0 mass% or more and 65.0 mass% or less, ZnO is 5.0 mass% or more and 50.0 mass% or less, TiO ₂ in the range of 0.5% by mass or more and 7.0% by mass or less, CaO in the range of 3.0% by mass or more and 7.5% by mass or less, K ₂ O in the range of 1.5% by mass or more and 4.0% by mass or less, and MnO ₂ in the range of 2.5% by mass or more and 12.0% by mass A glass composition containing within% or less can be preferably used.

When the glass composition of the above composition is used, it is easy to form a dense electrode film that has excellent acid resistance and does not have poor strength or penetration of a plating solution even when firing is performed in a non-oxidizing atmosphere.

In the first embodiment of the present invention, sulfur is contained in the glass composition. Sulfur blending for the glass composition may be performed by any method, for example, when preparing a glass composition, for example, BaSO ₄ is mixed as a sulfur source with a material constituting the glass, and a conventional method such as melting, quenching, and grinding. It can be manufactured with. At this time, the sulfur source is weighed so that the amount of sulfur contained in the sulfur source is 10 ppm or more and 370 ppm or less with respect to the metal powder.

The glass composition may be contained in the conductive paste in the form of coating a metal powder, for example, as the above-described glassy thin film, but it is preferably contained in the form of a glass powder independent from the metal powder.

This makes it particularly advantageous in terms of cost.

The glass powder may be in the form of a powder in which particles such as granules, flakes, fibers, needles, and irregular shapes are collected, for example.

Hereinafter, the case where the glass composition constituting the conductive paste is glass powder will be mainly described.

The average particle diameter of the glass composition is not particularly limited, but it is preferably 0.1 µm or more and 4.5 µm or less, more preferably 0.3 µm or more and 4.0 µm or less, and even more preferably 0.8 µm or more and 3.5 µm or less.

The BET specific surface area of the glass composition is not particularly limited, but it is preferably 0.90 m 2 /g or more and 5.00 m 2 /g or less, more preferably 1.20 m 2 /g or more and 4.50 m 2 /g or less, and 1.50 m 2 /g or more and 4.00 m 2 /g It is more preferable that it is the following.

The content of the glass composition in the conductive paste is not particularly limited, but it is preferably 4.0% by mass or more and 20.0% by mass or less, more preferably 5.0% by mass or more and 15.0% by mass or less, and still more preferably 6.0% by mass or more and 10.0% by mass or less. .

In addition, although the plurality of particles constituting the glass composition constituting the conductive paste of the present invention may be glass particles having the same or uniform glass composition with each other, control of sintering behavior and adhesion/adhesion to a base material For the purpose of improving, and the like, a plurality of types of glass particles having different compositions, particle diameters, etc. may be included according to a generally widely known method.

<Organic Vehicle>

The organic vehicle included in the conductive paste in the present invention is not particularly limited, and examples include alcohols (e.g., terpineol, α-terpineol, β-terpineol, etc.), esters (e.g., hydroxy group). Containing esters, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, butylcarbitol acetate, etc.), ethers (eg glycol ethers such as dipropylene glycol-n-propyl ether, etc.) Cellulose resins (e.g. ethylcellulose, nitrocellulose, etc.), (meth)acrylic resins (e.g. polymethylacrylate, polymethylmethacrylate, etc.) ), ester resins (e.g., rosin ester), polyvinyl acetal (e.g., polyvinyl butyral, etc.) B. Depending on the application method, the organic vehicle may consist only of an organic solvent and may not require an organic binder.

The organic solvent preferably contains at least one of alcohols (especially terpineol) and ethers (especially dipropylene glycol-n-propyl ether), and more preferably contains both.

In addition, it is preferable to include a (meth)acrylic resin as the organic binder.

Although the content of the organic vehicle in the conductive paste is not particularly limited, it is preferably 10.0% by mass or more and 40.0% by mass or less, more preferably 15.0% by mass or more and 35.0% by mass or less, and still more preferably 20.0% by mass or more and 30.0% by mass or less. .

The content of the organic solvent in the conductive paste is not particularly limited, but it is preferably 7.0% by mass or more and 30.0% by mass or less, more preferably 10.0% by mass or more and 28.0% by mass or less, and furthermore 14.0% by mass or more and 25.0% by mass or less. desirable.

In addition, the content of the organic binder in the conductive paste is not particularly limited, but it is preferably 1.0% by mass or more and 15.0% by mass or less, more preferably 2.0% by mass or more and 10.0% by mass or less, furthermore 3.0% by mass or more and 8.0% by mass or less. desirable.

<Inorganic additives>

The conductive paste is a component different from each of the aforementioned components, and may contain an inorganic additive containing sulfur. At this time, the amount of the inorganic additive added is weighed so that the amount of sulfur contained in the inorganic additive is in the range of 10 ppm or more and 370 ppm or less with respect to the metal powder.

By using such an inorganic additive, for example, by adjusting the addition amount of the inorganic additive, the sulfur content of the metal powder in the conductive paste can be preferably adjusted without adjusting the sulfur content in the glass composition. As a result, for example, an easily available glass composition can be preferably used for producing a conductive paste.

The inorganic additive containing sulfur may be present in a dissolved state in the conductive paste, but is preferably contained as an insoluble component.

Thereby, it is possible to more effectively prevent accidental reaction with the metal powder during storage of the conductive paste, for example.

Examples of the inorganic additive containing sulfur include sulfate, sulfite, persulfate, thiosulfuric acid, and metal sulfide, but sulfates are preferable.

Among various inorganic additives, sulfate is a component that is relatively easily soluble in glass when the glass flows during firing of the conductive paste. Therefore, when a sulfate salt is used as an inorganic additive, the above-described effect is more remarkably exhibited.

Examples of the sulfate salt include barium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate, sodium sulfate, potassium sulfate, sodium potassium sulfate, and ammonium sulfate. Among these, barium sulfate is preferable.

Thereby, the above-described effect is more remarkably exhibited. In addition, barium sulfate is a highly chemically stable and poorly soluble component under normal conditions (eg, 0°C or more and 40°C or less in which the conductive paste is stored), and is a component that is difficult to unexpectedly react with the metal powder. In addition, since barium sulfate is a material that is relatively inexpensive and can be easily and stably obtained, it is also preferable from the viewpoint of stable supply of conductive paste and reduction in production cost.

As for the inorganic additive in the conductive paste, a small-diameter powder is more likely to contain sulfur in the glass composition, and although it is not particularly limited, the average particle diameter (D ₅₀ ) is preferably 0.5 µm or less, and more preferably 0.1 µm or less. When the availability is also considered, the average particle diameter is most preferably 0.01 µm or more and 0.05 µm or less.

<Organic additives>

The conductive paste is a component different from each of the aforementioned components, and may contain an organic additive containing sulfur. At this time, the amount of the organic additive added is weighed so that the amount of sulfur contained in the organic additive is in the range of 10 ppm or more and 370 ppm or less with respect to the metal powder.

By using such an organic additive, for example, by adjusting the amount of the organic additive added, the sulfur content of the metal powder in the conductive paste can be preferably adjusted without adjusting the sulfur content in the glass composition. As a result, for example, an easily available glass composition can be preferably used for producing a conductive paste.

The organic additive containing sulfur may be present in a dissolved state in the conductive paste, or may be included as an insoluble component.

As an organic additive containing sulfur, a compound having a thiol group, etc. are mentioned, for example.

Examples of compounds having a thiol group (organic additives) include thiols such as dodecanethiol (mercaptoalkane compounds), mercaptoalcohol compounds such as mercaptoethanol (compounds having both functional groups of OH and SH groups), and the like. I can.

<Other ingredients>

The conductive paste may contain other components other than the above-described components. For example, plasticizers and defoaming agents added to general conductive pastes, dispersants such as higher fatty acids or fatty acid esters, leveling agents, stabilizers, adhesion promoters, surfactants, etc. are exemplified, but it is preferable that sulfur is not contained in all components. Do.

[Use of conductive paste]

The conductive paste of the present invention is generally used to form a conductive portion by applying and firing by a widely known method. The application is not particularly limited, but is particularly suitable for forming internal conductors (internal electrodes) and terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors, and multilayer ceramic actuators.

Conductive paste coating is performed on a desired base body by, for example, screen printing, transfer printing, dipping, brush application, or a method using a dispenser, followed by drying and firing.

The drying temperature of the conductive paste is not particularly limited, but may be, for example, 100°C or more and 200°C or less. Further, the firing temperature (peak temperature) is also not particularly limited, but is, for example, 600°C or more and 900°C or less, preferably 700°C or more and 880°C or less, and more preferably 730°C or more and 850°C or less.

As mentioned above, although preferable embodiment of this invention was demonstrated, this invention is not limited to this.

Example

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the following examples. In addition, in the following description, the treatment in which no particular temperature or humidity conditions are indicated is performed at room temperature (25° C.) and 50% relative humidity. In addition, for various measurement conditions, in particular, the temperature and humidity conditions are not indicated are the values at room temperature (25°C) and 50% relative humidity.

[1] Manufacture of conductive paste

(Preliminaries)

First, as a metal powder, _{a flake-like copper powder having an average particle diameter D 50} : 2.7 μm and a BET specific surface area: 0.65 m 2 /g was prepared. Further, this copper powder is a single metal (pure copper) powder that does not substantially contain metal elements other than copper, and does not contain sulfur substantially.

In addition, as a glass composition, three types were prepared as a basic composition. Glass compositions A, B, and C are each in terms of oxide, using the oxide composition shown in Table 1 as the basic composition, combining each glass raw material, melting at 1,200°C using a platinum crucible, air cooling or rapid cooling, and then having an average particle diameter of D _{50 or less} . It was obtained by pulverizing until it became 2.1 μm.

In addition, when additional sulfur is added to the glass composition, barium sulfate (BaSO ₄ ) as a sulfur source for the glass composition A and the glass composition B is used as an external component for the glass raw material described in Table 1 (in other words, as shown in Table 1). Glass composition A and glass composition B were added by adjusting the amount of Ba raw material used relative to the basic composition accordingly, because the Ba component increases to the glass composition at that time. The basic composition was not changed, only the sulfur content was changed. In addition, when sulfur was added to the glass composition C, only the sulfur content was changed in the same manner except that _{potassium sulfate (K 2} SO _{4) was used as the sulfur source to adjust the amount of the K raw material.}

As an organic binder, VL-7501 (manufactured by Mitsubishi Chemical), Diamondal MB-2677 (manufactured by Mitsubishi Chemical), and Diamondal BR-105 (manufactured by Mitsubishi Chemical) were mixed in a 1:5:1 mass ratio. (Acrylic resin) was prepared.

As an organic solvent, a mixed solvent was prepared in which terpineol (manufactured by Ogawa Koryo Corporation, EK Terpineol) and glycol ether (manufactured by Dow Chemical Nippon Corporation: Dawanol DPnP glycol ether) were mixed in an 8:2 mass ratio.

_{In addition, BaSO 4 powder having an average particle diameter (D 50} ) of 0.5 μm was prepared as an inorganic additive containing sulfur, and mercaptoethanol, dodecanethiol, and dimethyl sulfoxide were prepared as organic additives.

(Example 1)

Metal powder; Glass composition A to which a sulfur component was added; Organic binders; And an organic solvent in a mass ratio of 65:9:5:21, and then kneaded with a roll mill to prepare a conductive paste. Further, in the conductive paste, the glass composition was contained as a glass powder.

Further, as a result of confirming the sulfur content with a carbon-sulfur analyzer EMIA-320V (manufactured by HORIBA), the sulfur content in Example 1 was 198 ppm based on the metal powder.

(Examples 2 to 7)

A conductive paste was prepared in the same manner as in Example 1, except that the amount of the sulfur component added to the glass composition A was changed so that the sulfur content of the metal powder became the value shown in Table 2.

(Example 8)

A conductive paste was prepared in the same manner as in Example 1 except that a sulfur component was not added to the glass composition A and BaSO _{4 powder was added as an inorganic additive.}

The _{sulfur content according to the addition of BaSO 4} powder was 115 ppm for the metal powder.

(Examples 9 to 11)

A conductive paste was prepared in the same manner as in Example 8, except that the addition amount of _{the BaSO 4} powder was changed so that the sulfur content of the metal powder became the value shown in Table 2.

(Example 12)

A conductive paste was prepared in the same manner as in Example 8, except that mercaptoethanol was added instead of _{BaSO 4 powder.}

The sulfur content according to the addition of mercaptoethanol was 115 ppm based on the metal powder.

(Examples 13 to 15)

A conductive paste was prepared in the same manner as in Example 12 except that the amount of mercaptoethanol was changed so that the sulfur content of the metal powder became the value shown in Table 2.

(Example 16)

A conductive paste was prepared in the same manner as in Example 12, except that dodecanethiol was used instead of mercaptoethanol.

(Examples 17-19)

A conductive paste was prepared in the same manner as in Example 16 except that the amount of dodecanethiol was changed so that the sulfur content of the metal powder became the value shown in Table 2.

(Comparative Example 1)

A conductive paste was prepared in the same manner as in Example 1, except that a sulfur component was not added to the glass composition A. In addition, neither an inorganic additive containing sulfur nor an organic additive was added to Comparative Example 1.

(Comparative Example 2)

A conductive paste was prepared in the same manner as in Example 1 except that the amount of the sulfur component added to the glass composition A was changed so that the sulfur content of the metal powder was 381 ppm.

(Comparative Example 3)

A conductive paste was prepared in the same manner as in Example 12 except that the amount of mercaptoethanol was changed so that the sulfur content of the metal powder was 9 ppm.

(Comparative Examples 4-5)

A conductive paste was prepared in the same manner as in Example 12, except that dimethyl sulfoxide was used instead of mercaptoethanol, and the amount of dimethyl sulfoxide was adjusted so that the sulfur content of the metal powder became the value shown in Table 2.

(Comparative Example 6)

A conductive paste was prepared in the same manner as in Example 1, except that the amount of the sulfur component added to the glass composition A was changed so that the sulfur content of the metal powder was 653 ppm.

[2] Evaluation

[2-1] 750℃ firing

First, using the conductive pastes of each of the above examples and each of the comparative examples, after drying the cross-section of a ceramic chip component having a size of 3.2 × 2.5 mm, coating and printing so that the film thickness is 165 μm, and after drying at 150° C. for 10 minutes, the peak temperature is A fired body was obtained by firing for 70 minutes in a firing furnace controlled at a temperature of 750°C.

Thereafter, EDX analysis using Quantax75 (manufactured by Bruker) was performed on the fired body under the conditions of an acceleration voltage of 5 kV, a measurement time of 100 seconds, and a magnification of 200 times, and the amount of glass lift (Si amount) at the center of the fired film was measured. The undersinterability was evaluated according to the criteria.

A: The glass lifting amount is less than 15%.

B: The glass lifting amount is 15% or more and less than 20%.

C: The glass lifting amount is 20% or more.

Next, the fired body was polished, and a cross-sectional SEM image of the fired film was taken using TM-4000 (manufactured by Hitachi Hi-Tech), and the void (void) area in the fired film was calculated according to the following criteria. The compactness was evaluated.

A: Density is 99% or more (porosity is 1% or less).

B: Density is 98% or more and less than 99% (porosity is more than 1% and less than 2%).

C: Density is less than 98% (porosity is more than 2%).

[2-2] Firing at 780℃

The fired bodies were prepared in Examples 1 to 19 and Comparative Examples 1 to 6 by the same method except that the peak temperature during firing was set to 780°C, and undersintering and compactness were evaluated.

These results are summarized in Table 2.

[3] Manufacture of conductive paste

(Examples 20 to 24, Comparative Examples 7 to 8)

_{As the glass composition, a glass composition B to which BaSO 4} was added so that the sulfur content of the metal powder became the value shown in Table 3 was used, and the mass ratio of the metal powder, the glass composition B, the organic binder and the organic solvent was 66:10:6. A conductive paste was prepared in the same manner as in Example 1 except for mixing at :18.

(Examples 25 to 29, Comparative Examples 9 to 10)

_{As the glass composition, a glass composition C to which K 2} SO ₄ was added so that the sulfur content of the metal powder became the value shown in Table 3 was used, and the mass ratio of the metal powder, the glass composition C, the organic binder and the organic solvent was 69:7. A conductive paste was prepared in the same manner as in Example 1, except for mixing at :5:19.

[4] Evaluation

[4-1] firing

Except for using the conductive pastes of Examples 20 to 29 and Comparative Examples 7 to 10, a fired body was produced by firing at peak temperatures of 750°C and 780°C in the same manner as above to evaluate undersintering and compactness.

In addition, fired bodies were prepared in Examples 1 to 7, Examples 20 to 29, Comparative Examples 2, and 6 to 10 in the same manner as above except that the peak temperature during firing was set to 830°C to evaluate undersintering and compactness. .

These results are summarized in Table 3.

On the other hand, in order to prepare the effect of adding sulfur to the glass composition, some evaluation results of Examples 1 to 7, Comparative Example 2, and Comparative Example 6 in Table 3 are duplicated with Table 2.

As is apparent from Tables 2 and 3, the conductive paste of the present invention is unlikely to have adverse effects due to over-sintering, and since the glass lift of the fired film is effectively prevented and the occurrence of voids in the fired film is effectively suppressed, a sufficiently wide firing window is achieved. You can see that it is. On the other hand, in the comparative example, satisfactory results were not obtained.

In addition, a conductive paste was prepared in the same manner as in Examples and Comparative Examples, except that a copper alloy powder containing 2% by mass of silver was used as the metal powder, and the average particle diameter of the metal powder was in the range of 0.2 µm or more and 5.0 µm or less. Inside, the BET specific surface area of the metal powder is within the range of 0.30 m2/g or more and 1.00 m2/g or less, the average particle diameter of the glass powder as a glass composition is within the range of 0.1 μm or more and 4.5 μm or less, and the BET specific surface area of the glass composition is 0.90 m2/ In the range of g or more and 5.00 m 2 /g or less, the content of the metal powder in the conductive paste is 50.0 mass% or more and 80.0 mass% or less, the content of the glass composition in the conductive paste is 4.0 mass% or more and 20.0 mass% or less The content of the organic vehicle in the range is 10.0% by mass or more and 40.0% by mass or less, the content of the organic solvent in the conductive paste is 7.0% by mass or more and 30.0% by mass or less, and the content of the organic binder in the conductive paste is 1.0% by mass or more and 15.0% by mass. Except for various changes within the range of% or less, a conductive paste was prepared in the same manner as in the above Examples and Comparative Examples, and the same evaluation as described above was performed. As a result, the same results as above were obtained.

The conductive paste of the present invention comprises a metal powder containing copper; Glass composition; And an organic vehicle, wherein the glass composition contains sulfur (S), and the sulfur (S) content is 10 ppm or more and 370 ppm or less with respect to the metal powder. In addition, the conductive paste of the present invention includes a metal powder containing copper; Glass composition; Organic vehicle; And an inorganic additive, wherein the inorganic additive contains sulfur (S), and the content of the sulfur (S) is 10 ppm or more and 370 ppm or less with respect to the metal powder. In addition, the conductive paste of the present invention includes a metal powder containing copper; Glass composition; Organic vehicle; And a conductive paste containing an organic additive, wherein the organic additive has a thiol group, and the content of sulfur (S) in the organic additive is 10 ppm or more and 370 ppm or less with respect to the metal powder. Accordingly, it is possible to appropriately control the firing behavior of a single metal powder containing copper, and as a result, a conductive paste having a wide firing window and less likely to cause problems such as voids or glass lift after firing can be provided. Therefore, the conductive paste of the present invention has industrial applicability.

Claims (6)

Metal powder containing copper; Glass composition; And as a conductive paste containing an organic vehicle,
The conductive paste, wherein the glass composition contains sulfur (S), and the content of the sulfur (S) is 10 ppm or more and 370 ppm or less with respect to the metal powder. Metal powder containing copper; Glass composition; Organic vehicle; And as a conductive paste containing an inorganic additive,
The inorganic additive contains sulfur (S), and the content of the sulfur (S) is 10 ppm or more and 370 ppm or less with respect to the metal powder. The method according to claim 2,
The conductive paste in which the inorganic additive is a sulfate. Metal powder containing copper; Glass composition; Organic vehicle; And as a conductive paste containing an organic additive,
The organic additive has a thiol group, and the content of sulfur (S) in the organic additive is 10 ppm or more and 370 ppm or less with respect to the metal powder. The method according to any one of claims 1 to 4,
The conductive paste in which the metal powder is copper powder. The method according to any one of claims 1 to 5,
A conductive paste in which the content of sulfur (S) contained in the metal powder is less than 10 ppm.