JP6950833B2 - Conductive paste for forming external electrodes of laminated ceramic electronic components - Google Patents

Description

The present invention relates to a conductive paste for forming an external electrode of a laminated ceramic electronic component using a metal powder containing copper as a main component as a conductive component.

As an 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 containing a conductive powder, a glass composition, and an organic vehicle is used.

Metal powders such as silver (Ag) and palladium (Pd) have been used as the conductive powders, but in recent years, metal powders containing copper (Cu) have been used from the viewpoint of excellent conductivity and production cost. A conductive paste containing (hereinafter, copper paste) is particularly widely used.

In order to form an external electrode of a laminated ceramic electronic component using a copper paste, generally, first, a chip-shaped laminate in which dielectric layers and internal electrode layers are alternately laminated is prepared, and an end face thereof is prepared. On the other hand, the copper paste is applied by an appropriate method (for example, a dip printing method or a screen printing method). Then, the metal powder containing copper is heated and fired in an atmosphere where it is difficult to oxidize, the organic components in the paste are scattered and decomposed, and then the glass is fluidized and the metal particles containing copper are sintered with each other. An external electrode is formed. At this time, the range of the heating temperature suitable for firing is determined by the type and composition of the metal powder, the glass composition, the organic vehicle, and other additives contained in the paste.
Further, a plating layer of tin, nickel, or the like is formed on the surface of the formed external electrode for the purpose of improving reliability as an electrode and facilitating solder mounting.

By the way, in the conventional copper paste, when firing after coating the chip-shaped laminate on the end face, if the temperature range suitable for firing (hereinafter referred to as "firing window") is narrow, temperature unevenness in the firing furnace may occur. There is a problem that oversintering is likely to occur due to a slight temperature change. In the case of oversintering, the metal powder containing copper rapidly shrinks to cause the glass component to emerge, which may cause so-called "glass floating" in which the glass component is unevenly distributed on the surface portion of the pattern after firing. When such glass floating occurs, the adhesion between the fired pattern and various metals such as tin and nickel is lowered, and it becomes difficult to form a plating layer and the like.

In order to suppress the occurrence of such glass floating, it is conceivable to lower the firing temperature so that oversintering does not occur. However, since the firing window is narrow, in this case, the density of the firing film (electrode) becomes low, and voids (voids) are generated in the film. As a result, the conductivity of the electrode and the adhesive strength with the ceramic element deteriorate, and the plating solution penetrates into the film when the fired film is plated in a later process, resulting in a decrease in insulation resistance and the element. In addition to causing body cracks, the infiltrated plating solution is heated during solder reflow and gasified, causing "solder explosion" in which the molten solder scatters.

By the way, in order to control the firing behavior of the metal powder, it has been conventionally attempted to perform a specific surface treatment on the surface of the metal powder. For example, in Patent Document 1, in order to control the sintering start temperature, it is attempted to attach any one of the elements Al, Si, Ti, Zr, Ce, and Sn to the surface of the copper powder. Further, 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 nickel, silver, copper, or palladium with a metal compound containing sulfur. ..

However, according to the study by the present inventors, when these surface treatments are applied to the metal powder containing copper, the influence on the firing behavior of the metal powder containing copper alone is too great, and the sintering start temperature is set. Even if it can be controlled, the firing window may be narrowed, or these conditions may have to be changed significantly depending on the firing temperature and firing atmosphere of the copper paste when the surface treatment is not performed. In that case, not only will it be necessary to redesign the paste from scratch, but the cost of the entire paste will increase due to the characteristics and restrictions of the raw materials and materials that can be used for the paste, and in some cases, the production line of the firing furnace, etc. It is not uncommon for cases to need to be reviewed.

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

An object of the present invention is to appropriately control the firing behavior of a single metal powder containing copper, and as a result, the firing window is wide, and the formation of an external electrode of a laminated ceramic electronic component that is less likely to cause problems such as voids and glass floating after firing. To provide a conductive paste for use.

Such an object is achieved by the present invention described in the following (1) to ( 6).
(1) A conductive paste for forming an external electrode of a laminated ceramic electronic component containing a metal powder containing copper, a glass composition, and an organic vehicle.
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.
A conductive paste for forming an external electrode of a laminated ceramic electronic component, characterized in that the content of sulfur (S) contained in the metal powder is less than 10 ppm.

(2) The conductive paste for forming an external electrode of the laminated ceramic electronic component according to (1) above, wherein the metal powder is copper powder.

(3) The conductive paste for forming an external electrode of the laminated ceramic electronic component according to (1) or (2) above, wherein the sulfur content in the glass composition is 12 ppm or more and 200 ppm or less with respect to the metal powder. ..
(4) For forming an external electrode of the laminated ceramic electronic component according to any one of (1) to (3) above, wherein the sulfur content in the glass composition is 15 ppm or more and 100 ppm or less with respect to the metal powder. Conductive paste.
(5) The glass composition contains SiO ₂ in the range of 2.0% by mass or more and 12.0% by mass or less, and B ₂ O ₃ in the range of 15.0% by mass or more and 30.0% by mass or less. The conductivity for forming an external electrode of the laminated ceramic electronic component according to any one of (1) to (4) above, which contains Al ₂ O ₃ in the range of 2.0% by mass or more and 12.0% by mass or less. Sex paste.
(6) The conductive paste for forming an external electrode of the laminated ceramic electronic component according to any one of (1) to (5) above, wherein the glass composition does not substantially contain Pb, Cd and Bi.

According to the present invention, it is possible to provide a conductive paste for forming an external electrode of a laminated ceramic electronic component, which is less likely to generate voids in the fired film when fired and is less likely to cause an adverse effect due to oversintering. ..

Hereinafter, preferred embodiments of the present invention will be described in detail.
[Conductive paste]
1. 1. 1st Embodiment The conductive paste according to a preferred embodiment of the present invention is a conductive paste containing a metal powder containing copper, a glass composition, and an organic vehicle, and the glass composition is sulfur (S). ), And the content of the sulfur is 10 ppm or more and 370 ppm or less with respect to the metal powder.

With such a configuration, in the conductive paste containing copper, the fluctuation of the firing behavior is small as compared with the case where the metal powder containing copper itself is surface-treated, and the firing behavior of the copper paste as a whole is appropriately controlled. It is possible to provide a conductive paste which has a wide firing window and is less likely to cause problems such as voids and glass floating after firing.

It is considered that such an excellent effect can be obtained for the following reasons. That is, as compared with the case where the metal powder is mixed with sulfur (S) or the surface of the metal powder is coated with the sulfur compound in the conventional example, the glass composition in the conductive paste starts to flow during firing. The present inventors speculate that the sulfur contained in the glass composition acts on the copper constituting the metal powder, and as a result, the sintering behavior of the metal powder is loosely controlled. doing.

2. Second Embodiment The conductive paste according to another preferred embodiment of the present invention is a conductive paste containing a metal powder containing copper, a glass composition, an organic vehicle, and an inorganic additive. , The inorganic additive contains copper, and the content of the sulfur is 10 ppm or more and 370 ppm or less with respect to the metal powder.

With such a configuration, in the conductive paste containing copper, the fluctuation of the firing behavior is small as compared with the case where the metal powder containing copper itself is surface-treated, and the firing behavior of the copper paste as a whole is appropriately controlled. It is possible to provide a conductive paste which has a wide firing window and is less likely to cause problems such as voids and glass floating after firing.

It is considered that such an excellent effect can be obtained for the following reasons. That is, as compared with the case where sulfur (S) is mixed with the metal powder or the surface of the metal powder is coated with a sulfur compound in the conventional example, the glass composition in the conductive paste starts to flow during firing and then becomes inorganic. The sulfur constituting the additive is once dissolved in the glass composition, and then the sulfur dissolved in the glass composition acts on the copper constituting the metal powder, resulting in sintering of the metal powder. The present inventors speculate that the behavior may be loosely controlled.

3. 3. Third Embodiment The conductive paste according to another preferred embodiment of the present invention is a conductive paste containing a metal powder containing copper, a glass composition, an organic vehicle, and an organic additive. 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 such a configuration, in the conductive paste containing copper, the fluctuation of the firing behavior is small as compared with the case where the metal powder containing copper itself is surface-treated, and the firing behavior of the copper paste as a whole is appropriately controlled. It is possible to provide a conductive paste which has a wide firing window and is less likely to cause problems such as voids and glass floating after firing.

It is considered that such an excellent effect can be obtained for the following reasons. That is, as compared with the case where sulfur (S) is mixed with the metal powder or the surface of the metal powder is coated with a sulfur compound in the conventional example, the glass composition in the conductive paste starts to flow during firing and then becomes organic. The sulfur constituting the additive is once dissolved in the glass composition, and then the sulfur dissolved in the glass composition acts on the copper constituting the metal powder, resulting in sintering of the metal powder. The present inventors speculate that the behavior may be loosely controlled.

Among the above-described embodiments, the glass composition of the first embodiment contains a predetermined amount of sulfur, and the inorganic additive of the second embodiment contains a predetermined amount of sulfur (particularly, a glass composition). In the form in which the product contains a predetermined amount of sulfur), the compactness of the fired film can be made particularly excellent even when the material is fired at a relatively low temperature (for example, 750 ° C.). Further, it is advantageous in that the range of the firing temperature (firing window) at which a suitable firing film can be formed is particularly wide. In the present invention, the first embodiment is particularly preferable. In the case of the third embodiment, since the organic additive may be strongly bound to the metal powder with time, it is necessary to manage the environment including the storage temperature.

If the above configuration is not satisfied, satisfactory results cannot be obtained.
For example, in the first to third embodiments, when the sulfur content in the predetermined component of the conductive paste is less than the lower limit, the adverse effect of oversintering during firing is sufficiently prevented. Can't be done. In particular, when fired at a relatively high temperature (for example, 780 ° C. or higher), adverse effects due to oversintering are likely to occur remarkably.

Further, in the first to third embodiments, when the sulfur content in the predetermined component of the conductive paste exceeds the upper limit value, the generation of voids in the fired film at the time of firing is sufficiently prevented. Can not do it. In particular, when fired at a relatively low temperature (for example, 750 ° C. or lower), voids are likely to be remarkably generated in the fired film.

Further, even if the sulfur content of the conductive paste as a whole is within the above range, if the sulfur content in the predetermined component does not satisfy the condition of the predetermined content, more specifically. When a large amount of sulfur is contained in the metal powder, the influence on the firing behavior such as the sintering start temperature of the metal powder is too large, so that the density of the fired film is lowered and the fired film is reduced. Voids are likely to occur inside.

As described above, the content of sulfur in the predetermined components (glass composition, inorganic additive, organic additive) of the conductive paste may be 10 ppm or more and 370 ppm or less with respect to the metal powder. , 12 ppm or more and 200 ppm or less, and particularly preferably 15 ppm or more and 100 ppm or less.
As a result, the above-mentioned effect is more prominently exhibited.

<Metal powder>
The conductive paste in the present invention contains a metal powder, and the metal powder contains copper.
Examples of such a metal powder include pure copper powder and copper alloy powder made of only copper. Further, it may be a metal powder having a core-shell structure in which copper particles are used as a core and the surface thereof is coated with a thin film made of copper oxide or an oxide thin film containing an element other than copper. The thin film is particularly preferably glassy. Coating of a vitreous thin film on a metal powder can be achieved by, for example, the method described in Japanese Patent No. 3206496 or the like.

Since the metal powder has a core-shell structure provided with the thin film, it is possible to suppress the oxidation of the metal powder and control the sintering start temperature of the metal powder.

The above-mentioned thin film made of copper oxide and the oxide thin film containing elements other than copper do not contain sulfur, but when the thin film is vitreous, sulfur may be contained in the thin film. .. The vitreous thin film not only suppresses the oxidation of the metal powder, but also softens and flows during firing, and also functions as a sintering aid for the metal powder. When the vitreous 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 copper element (Cu) with respect to the total amount of 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 in the present invention is substantially sulfur-free, but does not exclude aspects containing sulfur as an unavoidable impurity. That is, in the present invention, "the metal powder contains substantially no sulfur" means that the content of sulfur contained in the metal powder is less than 10 ppm, more preferably less than 7 ppm, and less than 5 ppm. More preferred.

As a result, the variation in the firing behavior is small as compared with the case where the metal powder itself containing copper is surface-treated, and the firing behavior of the copper paste as a whole can be appropriately controlled.

The average particle size (D ₅₀ ) of the metal powder is not particularly limited, but 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 1.0 μm or more. It is more preferably 4.0 μm or less.

In the present specification, the average particle size (D ₅₀ ) refers to a weight-based integrated fraction 50% value of the particle size distribution measured using a laser particle size distribution measuring device, unless otherwise specified, for example. It can be obtained by measurement using a laser diffraction / scattering type particle size distribution measuring device LA-960 (manufactured by HORIBA).

BET specific surface area of the metal powder is not particularly limited, it is preferably not more than 0.30 m ² / g or more ^{1.00m 2 / g, 0.40m 2 /} g or more 0.90 m ² / g or less of It is more preferable, and even more preferably less 0.50 m ² / g or more 0.80 m ² / g. The BET specific surface area can be determined by using, for example, Tristar 3000 (manufactured by Shimadzu Corporation).

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

As a result, the conductivity of the fired film can be made more reliably and sufficiently excellent while fully exerting the functions of the metal powder containing copper.

The plurality of particles constituting the metal powder constituting the conductive paste of the present invention are preferably metal particles having the same or uniform metal composition with each other, but as long as the effects of the present invention are not impaired, it is preferable. It may contain metal particles having different metal compositions. For example, the metal powder may contain a plurality of types of particles having different copper contents from each other. Even in such a case, the copper content of the metal powder as a whole preferably satisfies the above-mentioned 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 equal to or lower than the firing temperature, but the glass composition does not substantially contain Pb, Cd and Bi. Is preferable. _{For example, in the present invention, SiO 2} is added as an essential component in the range of 2.0% by mass or more and 12.0% by mass or less with respect to the total amount of the entire glass composition in terms of oxide _{, and B 2} O ₃ Is contained in the range of 15.0% by mass or more and 30.0% by mass or less, Al ₂ O ₃ is contained in the range of 2.0% by mass or more and 12.0% by mass or less, and BaO is 40 as other optional components. Within the range of 0.0% by mass or more and 65.0% by mass or less, ZnO is within the range of 5.0% by mass or more and 50.0% by mass or less, and TiO ₂ is 0.5% by mass or more and 7.0% by mass or less. within the range of, within the following 7.5 wt% 3.0 wt% or more CaO, the _{K 2} O in the range of 1.5 wt% to 4.0 wt% or less, the MnO ₂ 2. A glass composition containing in the range of 5% by mass or more and 12.0% by mass or less can be preferably used.

When the glass composition having the above composition is used, even when firing is performed in a non-oxidizing atmosphere, it is possible to form a dense electrode film having excellent acid resistance and no poor strength or penetration of plating solution. It's easy.

In the first embodiment of the present invention, sulfur is contained in the glass composition. Any method may be used for blending sulfur into the glass composition, but as an example, when producing a glass composition, for example, BaSO ₄ as a sulfur source is mixed with the material constituting the glass, and melted and rapidly cooled. , Can be manufactured by ordinary methods such as crushing. 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 being coated with the metal powder as the above-mentioned glassy thin film, for example, but is contained in the form of the glass powder independent of the metal powder. preferable.
This is particularly advantageous in terms of cost.

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

In the following description, the case where the glass composition constituting the conductive paste is a glass powder will be mainly described.

The average particle size of the glass composition is not particularly limited, but 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 0.8 μm or more and 3.5 μm or more. The following is more preferable.

BET specific surface area of the glass composition is not particularly limited, equal to or less than 0.90 m ² / g or more 5.00 m ² / g is preferably, 1.20 m ² / g or more 4.50 m ² / g or less Is more preferable, and more preferably 1.50 m ² / g or more and 4.00 m ² / g or less.

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

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, but the firing behavior can be controlled and the substrate can be coated. For the purpose of improving adhesiveness and adhesion, a plurality of types of glass particles having different compositions, particle sizes, etc. may be contained according to a generally widely known method.

<Organic vehicle>
In the present invention, the organic vehicle contained in the conductive paste is not particularly limited, and for example, alcohols (for example, tarpineol, α-terpineol, β-terpineol, etc.), esters (for example, hydroxy group-containing esters, 2, Select from organic solvents such as 2,4-trimethyl-1,3-pentanediol monoisobutyrate, butyl carbitol acetate, etc.), ethers (for example, glycol ethers such as dipropylene glycol-n-propyl ether, etc.) Cellular resins (eg, ethyl cellulose, nitrocellulose, etc.), (meth) acrylic resins (eg, polymethylacrylate, polymethylmethacrylate, etc.), ester-based resins (eg, rosin), etc. One or more selected from organic solvents such as ester) and polyvinyl acetal (for example, polyvinyl butyral) can be dissolved or dispersed, but depending on the application and coating method, the organic vehicle is organic. It consists only of solvent and may not require an organic binder.

The organic solvent preferably contains at least one of alcohols (particularly terpineol) and ethers (particularly dipropylene glycol-n-propyl ether), and those containing both of them are more preferable. preferable.
The organic binder preferably contains a (meth) acrylic resin.

The content of the organic vehicle in the conductive paste is not particularly limited, but is preferably 10.0% by mass or more and 40.0% by mass or less, and 15.0% by mass or more and 35.0% by mass or less. Is more preferable, and 20.0% by mass or more and 30.0% by mass or less is further preferable.

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

The content of the organic binder in the conductive paste is not particularly limited, but is preferably 1.0% by mass or more and 15.0% by mass or less, and 2.0% by mass or more and 10.0% by mass or less. It is more preferable that it is 3.0% by mass or more and 8.0% by mass or less.

<Inorganic additive>
The conductive paste may contain an inorganic additive containing sulfur as a component different from each of the above-mentioned components. 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, sulfur with respect to the metal powder in the conductive paste without adjusting the sulfur content in the glass composition. The content of the above can be preferably adjusted. As a result, for example, an easily available glass composition can be suitably used for producing a conductive paste.

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

Thereby, for example, when the conductive paste is stored, it can be more effectively prevented from reacting unintentionally with the metal powder.

Examples of the sulfur-containing inorganic additive include sulfate, sulfite, persulfate, thiosulfate, metal sulfide and the like, but sulfate is preferable.

Among various inorganic additives, sulfate is a component that is relatively easily dissolved in glass when the glass flows during firing of the conductive paste. Therefore, when a sulfate is used as the inorganic additive, the above-mentioned effects are more prominently exhibited.

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

As a result, the above-mentioned effect is more prominently exhibited. In addition, barium sulfate is a component having high chemical stability and poor solubility under normal conditions (for example, conditions such as 0 ° C. or higher and 40 ° C. or lower at which the conductive paste is stored), and is unwillingly a metal. It is a component that does not easily react with powder. Further, barium sulfate is a substance that is relatively inexpensive and can be easily and stably obtained, and is preferable from the viewpoints of stable supply of conductive paste and reduction of production cost.

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

<Organic additive>
The conductive paste may contain an organic additive containing sulfur as a component different from each of the above-mentioned components. 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 addition amount of the organic additive, sulfur with respect to the metal powder in the conductive paste without adjusting the sulfur content in the glass composition. The content of the above can be preferably adjusted. As a result, for example, an easily available glass composition can be suitably 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 contained as an insoluble component.

Examples of the sulfur-containing organic additive include compounds having a thiol group and the like.
Examples of the compound having a thiol group (organic additive) include thiols such as dodecanethiol (mercaptoalkane compound), a mercaptoalcohol compound such as mercaptoethanol (compound having both OH group and SH group functional groups), and the like. Can be mentioned.

<Other ingredients>
The conductive paste may contain other components in addition to the above-mentioned components. For example, plasticizers and defoamers added to general conductive pastes, dispersants such as higher fatty acids and fatty acid esters, leveling agents, stabilizers, adhesion promoters, surfactants and the like can be mentioned. However, it is preferable that the components do not contain sulfur.

[Use of conductive paste]
The conductive paste of the present invention is used for forming a conductive portion by applying and firing by a generally widely known method. Its application is not particularly limited, but it 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.

The conductive paste is applied to a desired substrate by, for example, screen printing, transfer printing, dipping, brush coating, a method using a dispenser, or the like, and then drying and firing.

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

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto.

The present invention will be described in more detail with reference to specific examples below, but the present invention is not limited to the following examples. In the following description, the treatments that do not particularly indicate the temperature condition and the humidity condition are performed at room temperature (25 ° C.) and a relative humidity of 50%. Further, as for various measurement conditions, those that do not particularly indicate temperature conditions and humidity conditions are numerical values at room temperature (25 ° C.) and relative humidity of 50%.

[1] Manufacture of conductive paste (preparation)
First, as the metal powder, a flake-shaped copper powder having _{an average particle size of D 50} : 2.7 μm and a BET specific surface area of 0.65 m ^{2 / g was prepared.} This copper powder is a single metal (pure copper) powder that does not substantially contain a metal element other than copper, and does not substantially contain sulfur.

As the glass composition, three types were prepared as the basic composition. For each of the glass compositions A, B and C, each glass raw material is prepared based on the oxide composition shown in Table 1 in terms of oxide, melted at 1200 ° C. using a platinum crucible, air-cooled or rapidly cooled, and then air-cooled or rapidly cooled. It could be pulverized until the average particle size D _{50 became 2.1 μm.}

When further sulfur is added to the glass composition, barium sulfate (BaSO ₄ ) is added as a sulfur source to the glass raw materials shown in Table 1 for the glass composition A and the glass composition B. It was added as a component (in other words, a component further added with the total of the glass raw materials shown in Table 1 as 100% by mass), but at that time, the Ba component increases as the glass composition, so that the Ba raw material with respect to the basic composition is increased accordingly. By adjusting the amount of glass used, only the sulfur content was changed without changing the basic compositions of the glass composition A and the glass composition B. When sulfur is added to the glass composition C, potassium sulfate (K ₂ SO ₄ ) is used as the sulfur source, and only the sulfur content changes in the same manner except that the amount of the K raw material used is adjusted. I did.

As an organic binder, VL-7501 (manufactured by Mitsubishi Chemical Corporation), Dianal MB-2677 (manufactured by Mitsubishi Chemical Corporation), and Dianal BR-105 (manufactured by Mitsubishi Chemical Corporation) have a mass ratio of 1: 5: 1. A mixed resin (acrylic resin) mixed in 1 was prepared.

As the organic solvent, a mixed solvent in which tarpineol (manufactured by Ogawa Fragrance Co., Ltd., EK tarpineol) and glycol ether (manufactured by Dow Chemical Japan, manufactured by Dow Chemical Japan: Dawanol DPnP glycol ether) was mixed at a mass ratio of 8: 2 was prepared.

_{In addition, BaSO 4 powder having an average particle size (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)
A metal powder, a glass composition A to which a sulfur component is added, an organic binder, and an organic solvent are mixed at a mass ratio of 65: 9: 5: 21 and then kneaded with a roll mill to produce a conductive paste. bottom. In the conductive paste, the glass composition was contained as a glass powder.

When the sulfur content was confirmed by a carbon / sulfur analyzer EMIA-320V (manufactured by HORIBA), the sulfur content in Example 1 was 198 ppm with respect to the metal powder.

(Examples 2 to 7)
A conductive paste was produced 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 with respect to the metal powder was the value shown in Table 2. bottom.

( Reference example 1 )
A conductive paste was produced in the same manner as in Example 1 except that the sulfur component was not added to the glass composition A and BaSO _{4 powder was added as an inorganic additive.}
The _{sulfur content due to the addition of BaSO 4} powder was 115 ppm with respect to the metal powder.

( Reference Examples 2-4 )
A conductive paste was produced in the same manner as in Reference Example 1 except that the addition amount of the _{BaSO 4} powder was changed so that the sulfur content with respect to the metal powder was the value shown in Table 2.

( Reference example 5 )
A conductive paste was produced in the same manner as in Reference Example 1 except that mercaptoethanol was added instead of _{BaSO 4 powder.}

The sulfur content due to the addition of mercaptoethanol was 115 ppm with respect to the metal powder.

( Reference examples 6 to 8 )
A conductive paste was produced in the same manner as in Reference Example 5 except that the amount of mercaptoethanol added was changed so that the sulfur content with respect to the metal powder was the value shown in Table 2.

( Reference example 9 )
A conductive paste was produced in the same manner as in Reference Example 5 except that dodecanethiol was used instead of mercaptoethanol.

( Reference Examples 10 to 12 )
A conductive paste was produced in the same manner as in Reference Example 9 except that the amount of dodecanethiol added was changed so that the sulfur content with respect to the metal powder was the value shown in Table 2.

(Comparative Example 1)
A conductive paste was produced in the same manner as in Example 1 except that the 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 produced 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 with respect to the metal powder was 381 ppm.

(Comparative Example 3)
A conductive paste was produced in the same manner as in Reference Example 5 except that the amount of mercaptoethanol added was changed so that the sulfur content with respect to the metal powder was 9 ppm.

(Comparative Examples 4 to 5)
Dimethyl sulfoxide was used instead of mercaptoethanol, and the conductivity was the same as in Reference Example 5 except that the amount of dimethyl sulfoxide added was adjusted so that the sulfur content in the metal powder was the value shown in Table 2. A sex paste was produced.

(Comparative Example 6)
A conductive paste was produced 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 in the metal powder was 653 ppm.

[2] Evaluation [2-1] Baking at 750 ° C. First, using the conductive pastes of the above Examples, Reference Examples, and Comparative Examples, the end faces of the 3.2 × 2.5 mm size ceramic chip parts were used. A fired body was obtained by coating and printing so that the film thickness after drying was 165 μm, drying at 150 ° C. for 10 minutes, and then firing in a temperature-controlled furnace so that the peak temperature was 750 ° C. for 70 minutes. rice field.

Then, the fired body was subjected to EDX analysis using Quantax75 (manufactured by Bruker) 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 floating (Si amount) in the central portion of the fired film was performed. Was measured, and the persinterability was evaluated according to the following criteria.

A: The amount of glass floating is less than 15%.
B: The amount of glass float is 15% or more and less than 20%.
C: The amount of glass floating is 20% or more.

Subsequently, the fired body is polished, and a cross-sectional SEM image of the fired film near the center is photographed using TM-4000 (manufactured by Hitachi High-Tech) to calculate the area of voids (voids) in the fired film. , The denseness of the fired film was evaluated according to the following criteria.

A: Dense density is 99% or more (porosity is 1% or less).
B: Dense density is 98% or more and less than 99% (porosity is more than 1% and less than 2%).
C: Dense density is less than 98% (porosity is more than 2%).

[2-2] Baking at 780 ° C. A fired body was prepared from Examples 1 to 7, Reference Examples 1 to 12 and Comparative Examples 1 to 6 in the same manner except that the peak temperature at the time of firing was set to 780 ° C., and overburned. The sinterability and compactness were evaluated.
These results are summarized in Table 2.

[3] Production of Conductive Paste (Examples 8 to 12 , Comparative Examples 7 to 8)
_{As the glass composition, a glass composition B to which BaSO 4} was added so that the sulfur content with respect to the metal powder became the value shown in Table 3 was used, and the mass of the metal powder, the glass composition B, the organic binder, and the organic solvent was used. A conductive paste was produced in the same manner as in Example 1 except that the mixture was mixed at a ratio of 66:10: 6: 18.

(Examples 13 to 17 , 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 with respect to the metal powder became the value shown in Table 3 was used, and the metal powder, the glass composition C, the organic binder, and the organic solvent were used. A conductive paste was produced in the same manner as in Example 1 except that the mixture was mixed with a mass ratio of 69: 7: 5: 19.

[4] Evaluation [4-1] Firing The calcined product was fired at peak temperatures of 750 ° C. and 780 ° C. in the same manner as described above except that the conductive pastes of Examples 8 to 17 and Comparative Examples 7 to 10 were used. Was prepared, and the persinterability and denseness were evaluated.
Further, a fired body was prepared from Examples 1 to 7, Examples 8 to 17 , Comparative Example 2, and Comparative Example 6 to 10 in the same manner as described above except that the peak temperature at the time of firing was set to 830 ° C., and overburned. The bondability and tightness were evaluated.
These results are summarized in Table 3.
In order to compare 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 overlap with Table 2.

As is clear from Tables 2 and 3, the conductive paste of the present invention is less likely to cause an adverse effect due to oversintering, effectively prevents glass from floating in the fired film, and is used in the fired film. Since the generation of voids is also effectively suppressed, it can be seen that a sufficiently wide firing window is achieved. On the other hand, in the comparative example, satisfactory results were not obtained.

Further, a conductive paste was produced in the same manner as in the Examples, Reference Examples and Comparative Examples except that a powder made of a copper alloy containing 2% by mass of silver was used as the metal powder, and the average of the metal powders was also produced. in the range of 0.2μm or more 5.0μm or less particle size, the BET specific surface area of the metal powder 0.30 m ² / g or more 1.00 m ² / g within the range, the average particle of the glass powder as the glass composition within a diameter less 0.1μm or 4.5 [mu] m, within a BET specific surface area of 0.90 m ² / g or more 5.00 m ² / g or less of the glass composition, the content of the metal powder in the conductive paste The content of the glass composition in the conductive paste is in the range of 50.0% by mass or more and 80.0% by mass or less, and the content of the glass composition in the conductive paste is in the range of 4.0% by mass or more and 20.0% by mass or less, in the conductive paste. The content of the organic vehicle is in the range of 10.0% by mass or more and 40.0% by mass or less, and the content of the organic solvent in the conductive paste is in the range of 7.0% by mass or more and 30.0% by mass or less. Conductivity in the same manner as in the Examples, Reference Examples and Comparative Examples, except that the content of the organic binder in the sex paste was variously changed within the range of 1.0% by mass or more and 15.0% by mass or less. When the paste was produced and evaluated in the same manner as described above, the same results as described above were obtained.

The conductive paste of the present invention is a conductive paste containing a metal powder containing copper, a glass composition, and an organic vehicle, wherein the glass composition contains sulfur (S), and the sulfur (S) The content is 10 ppm or more and 370 ppm or less with respect to the metal powder. The conductive paste of the present invention is a conductive paste containing a metal powder containing copper, a glass composition, an organic vehicle, and an inorganic additive, and the inorganic additive contains sulfur (S). The content of the sulfur (S) is 10 ppm or more and 370 ppm or less with respect to the metal powder. The conductive paste of the present invention is a conductive paste containing a metal powder containing copper, a glass composition, an organic vehicle, and an organic additive, and the organic additive has a thiol group. 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. Therefore, it is possible to provide a conductive paste in which the firing behavior of a single metal powder containing copper is appropriately controlled, and as a result, the firing window is wide and problems such as voids and glass floating after firing are less likely to occur. Therefore, the conductive paste of the present invention has industrial applicability.

Claims (6)

A conductive paste for forming an external electrode of a laminated ceramic electronic component containing a metal powder containing copper, a glass composition, and an organic vehicle.
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.
A conductive paste for forming an external electrode of a laminated ceramic electronic component, characterized in that the content of sulfur (S) contained in the metal powder is less than 10 ppm. The conductive paste for forming an external electrode of a laminated ceramic electronic component according to claim 1, wherein the metal powder is a copper powder. The conductive paste for forming an external electrode of a laminated ceramic electronic component according to claim 1 or 2, wherein the sulfur content in the glass composition is 12 ppm or more and 200 ppm or less with respect to the metal powder. The conductive paste for forming an external electrode of a laminated ceramic electronic component according to any one of claims 1 to 3, wherein the sulfur content in the glass composition is 15 ppm or more and 100 ppm or less with respect to the metal powder. The glass composition contains SiO ₂ in the range of 2.0% by mass or more and 12.0% by mass or less, and B ₂ O ₃ in the range of 15.0% by mass or more and 30.0% by mass or less. The conductive paste for forming an external electrode of a laminated ceramic electronic component according to any one of claims 1 to 4, which contains Al ₂ O ₃ in a range of 2.0% by mass or more and 12.0% by mass or less. The conductive paste for forming an external electrode of a laminated ceramic electronic component according to any one of claims 1 to 5, wherein the glass composition does not substantially contain Pb, Cd and Bi.