JP2024003265A - conductive paste - Google Patents

Abstract

To provide a conductive paste for an internal electrode of a layered ceramic capacitor, which is capable of maintaining relatively high coverage even if the internal electrode constitutes a thin layer.SOLUTION: Provided is a conductive paste for forming internal electrodes 4 and 5 of a layered ceramic capacitor 1 fabricated through a firing step. The conductive paste includes conductive metal powder, ceramic powder, an organic solvent, and an organic binder. The conductive metal powder contains silver. At least a portion of the ceramic powder comprises an ABO3 type oxide having a specific ion radius in which the ratio of the ion radius in the 6-coordination of an element at the A site in ABO3 with respect to the ion radius in the 6-coordination of silver is 0.89 or more and 1.02 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a conductive paste, and particularly to a conductive paste for forming internal electrodes of a multilayer ceramic capacitor.

A multilayer ceramic capacitor typically includes a multilayer body and a multilayer structure including a plurality of laminated dielectric layers made of ceramic and a plurality of internal electrodes each disposed along a plurality of interfaces between the dielectric layers. A plurality of external electrodes are provided on the outer surface and electrically connected to the internal electrodes. The internal electrode includes a plurality of first internal electrodes and a plurality of second internal electrodes arranged alternately in the stacking direction of the laminate, and the external electrode includes a first external electrode electrically connected to the first internal electrode. and a second external electrode electrically connected to the second internal electrode.

In order to reduce the size and increase the capacity of a multilayer ceramic capacitor having such a structure, it is necessary to reduce the thickness of the dielectric layer and the internal electrodes, and to increase the coverage (electrode continuity) of the internal electrodes. Generally, in the firing process when manufacturing multilayer ceramic capacitors, the temperature at which the conductive metal particles contained in the conductive paste film that will become the internal electrodes is sintered is higher than the temperature at which the ceramic constituting the dielectric layer is sintered. Since the metal particles contained in the internal electrodes are low, the metal particles contained in the internal electrodes are sintered first. This causes a reduction in the coverage of the internal electrodes. Particularly, in the case of internal electrodes that are thin, such as having a thickness of 1 μm or less, the coverage tends to decrease, and such a decrease in coverage tends to hinder an increase in capacity.

Therefore, in order to form thin internal electrodes with high coverage, the temperature at which the conductive metal particles contained in the conductive paste film that will become the internal electrodes is sintered must be needs to be higher. As a result, the temperature at which the metal particles contained in the conductive paste film, which is to become the internal electrode, sinter can be brought closer to the temperature at which the ceramic forming the dielectric layer starts sintering, and the internal electrode and dielectric layer The shrinkage timing during sintering can be brought closer to each other. As a result, the coverage of the internal electrodes becomes high, and a large capacity can be realized.

In order to increase the coverage of the internal electrodes and increase the capacity by the method described above, for example, as described in paragraph 0004 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2016-31807), It is known to add to the conductive paste a ceramic material having a composition similar to that of the ceramic constituting the dielectric layer, that is, a co-material. By adding the co-material, it is possible to shift the sintering timing of the metal particles contained in the conductive paste film that will become the internal electrode to a higher temperature side, and the metal particles contained in the conductive paste film are sintered. The temperature can be brought close to the temperature at which the ceramic forming the dielectric layer is sintered.

JP2016-31807A

However, even if a co-material is added to the conductive paste for forming internal electrodes, the temperature at which the metal particles contained in the conductive paste sinter is still higher than the temperature at which the ceramic constituting the dielectric layer sinters. It cannot be denied that this is low, and further improvement is desired. In particular, with respect to internal electrodes that are thin, for example, 1 μm or less in thickness, there is a strong need for an effective solution to the problem of coverage deterioration that impedes increases in capacity.

Therefore, the present invention was made in view of such problems, and an object of the present invention is to provide a conductive paste for forming internal electrodes that can maintain relatively high coverage even when the internal electrodes are made thinner. shall be.

The present invention is a conductive paste for forming internal electrodes of a multilayer ceramic capacitor, which contains a conductive metal powder, a ceramic powder, an organic solvent, and an organic binder. contains silver, and at least a part of the ceramic powder has a ratio of the ionic radius of the element at the A site in ABO ₃ in the 6-coordination to the ionic radius of the 6-coordination of silver to be 0.89 or more and 1. It is characterized by being a powder made of an ABO ₃ type oxide with a specific ionic radius of 0.02 or less.

If the internal electrodes of a multilayer ceramic capacitor are formed using the conductive paste according to the present invention, the coverage of the internal electrodes can be increased. Therefore, even if the internal electrodes are made thinner, the coverage of the internal electrodes can be maintained at a high level, so that increasing the capacity of the multilayer ceramic capacitor is not hindered.

1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 1 to which a conductive paste according to the present invention is applied.

Referring to FIG. 1, the structure of a multilayer ceramic capacitor 1 to which a conductive paste according to the present invention is applied will be described.

Multilayer ceramic capacitor 1 includes a multilayer body 2 . The laminate 2 includes a plurality of laminated dielectric layers 3 made of ceramic, and a plurality of internal electrodes 4 and 5 arranged along the interface between the plurality of dielectric layers 3. The internal electrodes 4 and 5 are classified into a plurality of first internal electrodes 4 and a plurality of second internal electrodes 5, which are alternately arranged in the stacking direction of the laminate 3. A first external electrode 6 and a second external electrode 7 are provided on the outer surface of the laminate 2, more specifically, on each opposing end surface. The first external electrode 6 is electrically connected to the first internal electrode 4 , and the second external electrode 7 is electrically connected to the second internal electrode 5 .

The dielectric layer 3 is made of, for example, a ceramic whose main component is ABO ₃ (A is at least one of Ba, Ca, and Sr, and B is at least one of Ti and Zr). Become. Further, the ceramic may have the above-mentioned ABO ₃ as a main component, and may further contain at least one of Mn, Mg, Si, Y, Dy, and Gd as a subcomponent.

Internal electrodes 4 and 5 contain silver as a conductive component. Further, as a characteristic composition, the internal electrodes 4 and 5 contain, for example, at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ . AgTiO ₃ , EuTiO ₃ and NaTiO ₃ have an illuminite crystal structure.

Note that, as can be seen from the experimental examples described below, in a preferred embodiment, the dielectric layer 3 is made of a ceramic whose main component is at least one selected from BaTiO ₃ , SrTiO ₃ and CaZrO ₃ , and the internal electrodes 4 and 5 contains silver as a conductive component, contains at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as a ceramic material, and optionally contains BaTiO ₃ , SrTiO ₃ and CaZrO contained in the dielectric layer 3. It further contains at least one species selected from ₃ .

The external electrodes 6 and 7 are formed, for example, by applying a conductive paste containing Ag or Cu as a main conductive component to the end surface of the laminate 2 and baking it. If necessary, for example, Ni plating and Sn plating may be applied on the thick film formed by baking.

The multilayer ceramic capacitor 1 is manufactured, for example, through the following steps. First, a ceramic slurry containing ceramic raw material powder having the composition as described above is prepared. Next, a suitable sheet forming method is applied to the ceramic slurry to form a ceramic green sheet. Next, a conductive paste to become each of the internal electrodes 4 and 5 is applied by printing or the like onto a predetermined ceramic green sheet among the plurality of ceramic green sheets. Next, a plurality of ceramic green sheets are laminated and pressed together to obtain a green laminate. The green laminate is then fired. In this firing step, the ceramic green sheet becomes the dielectric layer 3. Thereafter, external electrodes 6 and 7 are formed on the end faces of the laminate 3.

The conductive paste that is to become the internal electrodes 4 and 5 used in manufacturing the multilayer ceramic capacitor 1 described above is preferably manufactured as follows.

In preparing the conductive paste, the first step is to prepare a ceramic powder slurry containing ceramic powder, an organic solvent, and a dispersant, and the second step is to prepare a metal powder slurry containing a conductive metal powder, an organic solvent, and a dispersant. , a third step of preparing an organic vehicle containing an organic resin component and an organic solvent, and a fourth step of mixing the ceramic powder slurry, metal powder slurry, and organic vehicle.

More specifically, in the first step, a ceramic powder slurry is prepared by mixing ceramic powder and a dispersant into an organic solvent.

The ceramic powder used is, for example, at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as ABO ₃ oxides, and in addition to this, BaTiO ₃ and SrTiO 3 as co-materials. ₃ and at least one selected from CaZrO 3 and CaZrO ₃ may be used.

Since the conductive metal powder contained in the metal powder slurry produced in the second step described below contains silver, AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as the above-mentioned ABO ₃ oxides have a 6-coordination of silver. This results in an ABO ₃ type oxide having a specific ionic radius in which the ratio of the ionic radius in the 6-coordination of the A-site element in ABO ₃ to the ionic radius is 0.89 or more and 1.02 or less.

According to the ceramic powder made of at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as the ABO _trioxide , during firing, there is a gap between the ceramic powder and the silver powder contained in the metal powder slurry prepared in the second step. can suppress reactions that may occur. The ceramic powder has the above-mentioned ABO _trioxide as a main component, and may further contain at least one of Mn, Mg, Si, Y, Dy, and Gd as a subcomponent. When such a subcomponent is contained, grain growth of ceramic particles is further suppressed, and sintering of metal particles may be suppressed more effectively.

As the dispersant mixed into the ceramic powder in the first step, for example, an anionic polymer dispersant can be used, and as the organic solvent, for example, dihydroterpineol can be used.

In the second step, a metal powder slurry is prepared by mixing conductive metal powder and a dispersant into an organic solvent. As the conductive metal powder, a powder made of silver is used. As the dispersant and organic solvent used in the second step, those similar to those used in the first step can be used.

In the third step, an organic vehicle is prepared by mixing an organic resin component with an organic solvent. As the organic resin component, for example, ethyl cellulose resin can be used. The organic solvent used in the third step can also be the same as that used in the first step.

In the fourth step, the above-described ceramic powder slurry, metal powder slurry, and organic vehicle are mixed. As a result, a conductive paste to become the internal electrodes 4 and 5 is obtained. This conductive paste contains a ceramic powder slurry, and the ceramic powder slurry is a ceramic powder made of at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as an ABO ₃ oxide with a specific ionic radius, as described above. Therefore, the internal electrodes 4 and 5 included in the multilayer ceramic capacitor 1 manufactured through the firing process contain at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ .

[Experiment example]
Next, an experimental example conducted to confirm the effects of the present invention will be described.

In this experimental example, silver powder was prepared as the conductive metal powder contained in the conductive paste for forming internal electrodes.

On the other hand, in addition to AgTiO ₃ , EuTiO ₃ and NaTiO 3 , CuTiO ₃ , SrTiO ₃ , BaTiO ₃ and CaZrO ₃ are used as ABO ₃ oxides having a specific ionic radius constituting the ceramic powder contained in the conductive paste for forming internal _electrodes. prepared. Table 1 shows the "crystal structure", "coordination number", "A-site element", and "ion radius" for these ABO _trioxides . Note that Sr, Ba, and Ca are 12-coordinated in the original perovskite structure, but Sr, Ba, and Ca also form a solid solution at the sites of 6-coordinated elements (Ag, Eu, Na) in the ilmenite structure. Since it is 6-coordinated when it is oxidized, the "ionic radius" in Table 1 shows the value for 6-coordination.

Experimental Example 1, Experimental Example 2, and Experimental Example 3, which were carried out by changing the ceramic raw material constituting the dielectric layer, will be described below.

(Experiment Example 1) Main component of ceramic constituting dielectric layer: BaTiO ₃
1. Preparation of BaTiO ₃ -based ceramic raw material constituting the dielectric layer As starting materials, the main component BaCO ₃ and TiO ₂ powders were weighed, mixed in a ball mill for 72 hours, and then heat treated at a top temperature of 1000°C for 2 hours. A heat-treated powder was obtained. On the other hand, MnO, Dy ₂ O ₃ , MgO, SiO ₂ and BaCO ₃ powders were prepared as subcomponents, and the subcomponent powders were 100BaTiO ₃ +0.5Mn+1.0Dy+1.0Mg+1.0Si+2. The powders were weighed so as to have a composition ratio of 0Ba, and these subcomponent powders were added to the heat-treated powder, mixed for 24 hours in a ball mill, and then dried to obtain a BaTiO ₃ ceramic raw material powder.

2. Preparation of conductive paste for forming internal electrodes The conductive paste for forming internal electrodes contained the "ABO _trioxide " powder shown in Table 2 below and the BaTiO ₃ ceramic raw material powder for the dielectric layer. It was used as a ceramic powder.

These "ABO ₃ oxide" powders and BaTiO ₃ -based ceramic raw material powder were weighed so as to have the "addition ratio" shown in Table 2, and these powders, dihydroterpineol as an organic solvent, and anion as a dispersant were weighed. A ceramic powder slurry was prepared by pre-mixing the mixture and the polymer dispersant using a medium-free stirring mill, and then performing a dispersion treatment using a medium-stirring mill (first step).

On the other hand, silver powder as a conductive metal powder, dihydroterpineol as an organic solvent, and an anionic polymer dispersant as a dispersant were dispersed in a three-roll mill to prepare a metal powder slurry (second process).

Furthermore, ethyl cellulose resin as an organic resin component and dihydroterpineol as an organic solvent were mixed to obtain an organic vehicle (third step).

Thereafter, the metal powder slurry and the ceramic powder slurry were added to the organic vehicle and mixed and dispersed to produce a conductive paste for forming internal electrodes (fourth step).

Table 2 shows the ratio of the 6-coordinate ionic radius of the A-site element to the 6-coordinate ionic radius of silver to be included in the internal electrode, i.e., "ionic radius ratio (A-site element/metallic silver)". "It is shown. For sample 8, the ratio of the ionic radius (1.35 Å) of Ba element in the 6-coordination shown in Table 1 to the ionic radius (1.15 Å) in the 6-coordination of silver is shown. .

3. Preparation of Multilayer Ceramic Capacitor A ceramic slurry containing the BaTiO ₃ ceramic raw material powder prepared in 1 above was prepared, and then a doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Next, the conductive paste for forming internal electrodes prepared in 2 above was applied onto a predetermined ceramic green sheet among the plurality of ceramic green sheets by screen printing. Next, a plurality of ceramic green sheets were laminated and pressed together to obtain a raw laminate. The green laminate was then fired. Thereafter, external electrodes were formed on the end faces of the sintered laminate to produce a multilayer ceramic capacitor as a sample.

4. evaluation

An internal electrode and a dielectric layer located at the center in the height direction of a laminate included in a multilayer ceramic capacitor serving as a sample were peeled off from each other by electric field peeling.

Next, the vicinity of the central part (1/2 in the width direction and 1/2 in the length direction) of the exposed internal electrode was observed using a microscope at a magnification of 100 times. Then, by analyzing the obtained images, the ratio of the area occupied by the conductor film as the internal electrode in the exposed portion was determined as the "coverage" shown in Table 2. If the "coverage" is 80% or more, it is judged as good, and enter "○" in the "evaluation" column.If the "coverage" is lower than 80%, it is judged as poor, and in the "evaluation" column, write "○". ×” was entered.

5. Discussion Samples 1 to 3 and 5 to 7 in Table 2 have an “evaluation” of “○”. In these samples 1 to 3 and 5 to 7, the internal electrode contains one of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as the ABO ₃ oxide. Further, the internal electrode contains silver as a conductive component.

Here, focusing on the ionic radius, first, as shown in the "AgTiO ₃ " section of Table 1, the ionic radius of silver in six coordinations is 1.15 Å. On the other hand, the ionic radii in the 6-coordination of the A-site elements of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as the ABO ₃ oxides contained in the internal electrodes in Samples 1 to 3 and 5 to 7 are shown in Table 1. , 1.15 Å, 1.17 Å and 1.02 Å, respectively.

In samples 1 to 3 and 5 to 7, which were evaluated as "○", the ratio of the ionic radius in six coordinations of the element at the A site in ABO ₃ to the ionic radius in six coordinations of silver, that is, the radius ratio" is 0.89 or more and 1.02 or less.

In this way, AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as ABO ₃ oxides in Samples 1 to 3 and 5 to 7 have an ionic radius in the 6-coordination of the A-site element in ABO ₃ that is included in the internal electrode. Since the ionic radius is equal to or close to the six-coordinate ionic radius of silver as a conductive metal, the energy difference with silver in the internal electrode is 0 or small, so it remains without being ejected from the internal electrode part, and the internal It acts to improve the heat resistance of the electrode. As a result, it is estimated that the coverage of Samples 1 to 3 and 5 to 7 was as high as 82% or more.

In addition, as in samples 5 to 7, the addition ratio of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ is not necessarily 100%, but if it is 10% or more, none of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ is included. The effect of improving coverage was observed compared to the previous case.

On the other hand, in sample 4, which was evaluated as "×", SrTiO ₃ was used as the ABO ₃ oxide, and the ionic radius of Sr, which is the element at the A site in ABO ₃ , in the 6-coordination is shown in Table 1. As shown in , it is 1.18 Å. Therefore, the ratio of the ionic radius of Sr in six coordinations to the ionic radius of silver in six coordinations, that is, the "ionic radius ratio" is 1.03. That is, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and the coverage was as low as 76%.

In addition, in sample 8, which was also evaluated as "x", only BaTiO ₃ as a co-material was added to the internal electrode. In this case, Ba, which is an element at the A site in ABO ₃ of the perovskite structure, has 12 coordinations, but when it is dissolved in the A site of the illuminite structure, it has 6 coordinations, which is the coordination number of the A site of the illuminite structure. It is necessary to compare the ionic radius at the 6-coordinate position, and the ionic radius at the 6-coordinate position of Ba is 1.35 Å, as shown in Table 1. Therefore, the ratio of the ionic radius of Ba in six coordinations to the ionic radius of silver in six coordinations, that is, the "ionic radius ratio" is 1.17. Therefore, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and the coverage was as low as 75%.

In these samples 4 and 8, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and _BaTiO3 was discharged from the internal electrode part, and the heat resistance of the internal electrode did not improve and the coverage It is assumed that the

(Experiment Example 2) Main component of ceramic constituting dielectric layer: CaZrO ₃
1. Preparation of CaZrO ₃ -based ceramic raw material constituting the dielectric layer As starting materials, powders of main components CaCO ₃ and ZrO ₂ and powders of MnO, SiO ₂ and MgO as subcomponents were weighed and heated in a ball mill for 72 hours. After mixing, the mixture was heat treated at a top temperature of 1000° C. for 2 hours to obtain a CaZrO ₃ ceramic raw material powder.

2. Preparation of conductive paste for forming internal electrodes The conductive paste for forming internal electrodes contained the "ABO _trioxide " powder shown in Table 3 below and the CaZrO ₃ -based ceramic raw material powder for the dielectric layer. It was used as a ceramic powder.

These "ABO ₃ oxide" powders and CaZrO ₃ -based ceramic raw material powder were weighed so as to have the "addition ratio" shown in Table 3, and after going through the same process as in Experimental Example 1 above, they were mixed into powders for forming internal electrodes. A conductive paste was prepared.

In Table 3, as in Table 2, "ion radius ratio (A site element/metallic silver)" is shown. For sample 18, the ratio of the ionic radius (1.00 Å) of the Ca element in the 6-coordination shown in Table 1 to the ionic radius (1.15 Å) in the 6-coordination of silver is shown. .

3. Preparation of Multilayer Ceramic Capacitor A ceramic slurry containing the CaZrO ₃ ceramic raw material powder prepared in 1 above was prepared, and then a doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Thereafter, a multilayer ceramic capacitor serving as a sample was manufactured through the same steps as in Experimental Example 1.

4. evaluation

According to the same procedure as in Experimental Example 1, "coverage" was determined as shown in Table 3 and evaluated in the same manner.

5. Discussion Samples 11 to 13 and 15 to 17 in Table 3 have an “evaluation” of “○”. In these samples 11 to 13 and 15 to 17, the internal electrodes contained one of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as the ABO ₃ oxide. Further, the internal electrode contains silver as a conductive component.

Here, focusing on the ionic radius, first, as shown in the "AgTiO ₃ " section of Table 1, the ionic radius of silver in six coordinations is 1.15 Å. On the other hand, the ionic radius in the 6-coordination of each A-site element of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as ABO ₃ oxides contained in the internal electrodes in Samples 11 to 13 and 15 to 17 is shown in Table 1. , 1.15 Å, 1.17 Å and 1.02 Å, respectively.

In samples 11 to 13 and 15 to 17, which were evaluated as "○", the ratio of the ionic radius in six coordinations of the element at the A site in ABO ₃ to the ionic radius in six coordinations of silver, that is, the ratio of the ionic radius in six coordinations of silver radius ratio" is 0.89 or more and 1.02 or less.

In this way, AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as ABO ₃ oxides in Samples 11 to 13 and 15 to 17 have an ionic radius in the 6-coordination of the A-site element in ABO ₃ that is included in the internal electrode. Since the ionic radius is equal to or close to the six-coordinate ionic radius of silver as a conductive metal, the energy difference with silver in the internal electrode is 0 or small, so it remains without being ejected from the internal electrode part, and the internal It is presumed that this acts to improve the heat resistance of the electrode, and as a result, the coverage of Samples 11 to 13 and 15 to 17 was as high as 81% or more.

Further, as in samples 15 to 17, the addition ratio of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ is not necessarily 100%, but if it is 10% or more, none of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ is included. The effect of improving coverage was observed compared to the previous case.

On the other hand, in sample 14, which was evaluated as "×", CuTiO ₃ was used as the ABO ₃ oxide, and the ionic radius of Cu, which is an element at the A site in ABO ₃ , in the 6-coordination is shown in Table 1. As shown in , it is 0.73 Å. Therefore, the ratio of the ionic radius of Cu in six coordinations to the ionic radius of silver in six coordinations, that is, the "ionic radius ratio" is 0.63. That is, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and the coverage was as low as 75%.

In addition, in sample 18, which was also evaluated as "x", only CaZrO ₃ as a common material was added to the internal electrode. In this case, Ca, which is an element at the A site in ABO ₃ of the perovskite structure, has 12 coordinations, but when dissolved in the A site of the illuminite structure, Ca has 6 coordinations, which is the coordination number of the A site of the illuminite structure. It is necessary to compare the ionic radius at the 6-coordinate position, and the ionic radius at the 6-coordinate position of Ca is 1.00 Å, as shown in Table 1. Therefore, the ratio of the ionic radius of Ca in six coordinations to the ionic radius of silver in six coordinations, that is, the "ionic radius ratio" is 0.87. Therefore, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and the coverage was as low as 72%.

In these samples 14 and 18, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and CaZrO ₃ was discharged from the internal electrode portion, and the heat resistance of the internal electrode did not improve and the coverage It is assumed that the

(Experiment Example 3) Main component of ceramic constituting dielectric layer: SrTiO ₃
1. Preparation of SrTiO ₃ -based ceramic raw material constituting the dielectric layer As starting materials, the main component SrCO ₃ and TiO ₂ powders and the subcomponent MnO, SiO ₂ and MgO powders were weighed and heated in a ball mill for 72 hours. After mixing, the mixture was heat-treated at a top temperature of 1000° C. for 2 hours to obtain SrTiO ₃ ceramic raw material powder.

2. Preparation of conductive paste for forming internal electrodes The conductive paste for forming internal electrodes contained the "ABO _trioxide " powder shown in Table 4 below and the SrTiO ₃ -based ceramic raw material powder for the dielectric layer. It was used as a ceramic powder.

These "ABO ₃ oxide" powders and SrTiO ₃ -based ceramic raw material powder were weighed so as to have the "addition ratio" shown in Table 4, and after going through the same process as in Experimental Example 1 above, they were prepared for forming internal electrodes. A conductive paste was prepared.

In Table 4, as in Table 2, "ion radius ratio (A site element/metallic silver)" is shown. For sample 28, the ratio of the ionic radius (1.18 Å) of the Sr element in the 6-coordination shown in Table 1 to the ionic radius (1.15 Å) in the 6-coordination of silver is shown. .

3. Preparation of Multilayer Ceramic Capacitor A ceramic slurry containing the SrTiO ₃ ceramic raw material powder prepared in 1 above was prepared, and then a doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Thereafter, a multilayer ceramic capacitor serving as a sample was manufactured through the same steps as in Experimental Example 1.

4. evaluation

According to the same procedure as in Experimental Example 1, "coverage" was determined as shown in Table 4 and evaluated in the same manner.

5. Discussion Samples 21 to 23 and 25 to 27 in Table 4 have an “evaluation” of “○”. In these samples 21 to 23 and 25 to 27, the internal electrode contains one of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as the ABO ₃ oxide. Further, the internal electrode contains silver as a conductive component.

Here, focusing on the ionic radius, first, as shown in the "AgTiO ₃ " section of Table 1, the ionic radius of silver in six coordinations is 1.15 Å. On the other hand, the ionic radius in the 6-coordination of each A-site element of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as ABO ₃ oxides contained in the internal electrodes in Samples 21 to 23 and 25 to 27 is shown in Table 1. , 1.15 Å, 1.17 Å and 1.02 Å, respectively.

In samples 21 to 23 and 25 to 27, which were evaluated as "○", the ratio of the ionic radius in six coordinations of the element at the A site in ABO ₃ to the ionic radius in six coordinations of silver, that is, radius ratio" is 0.89 or more and 1.02 or less.

In this way, AgTiO ₃ , EuTiO ₃ and NaTiO ₃ as ABO ₃ oxides in Samples 21 to 23 and 25 to 27 have an ionic radius in the 6-coordination of the A-site element in ABO ₃ that is included in the internal electrode. Since the ionic radius is equal to or close to the six-coordinate ionic radius of silver as a conductive metal, the energy difference with silver in the internal electrode is 0 or small, so it remains without being ejected from the internal electrode part, and the internal It is presumed that this acts to improve the heat resistance of the electrode, and as a result, the coverage of Samples 21 to 23 and 25 to 27 was as high as 80% or more.

In addition, as in samples 25 to 27, the addition ratio of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ is not necessarily 100%, but if it is 10% or more, none of AgTiO ₃ , EuTiO ₃ and NaTiO ₃ is included. The effect of improving coverage was observed compared to the previous case.

On the other hand, in sample 24, which was evaluated as "×", CuTiO ₃ was used as the ABO ₃ oxide, and the ionic radius in the 6-coordination of Cu, which is the element at the A site in ABO ₃ , is shown in Table 1. As shown in , it is 0.73 Å. Therefore, the ratio of the ionic radius of Cu in six coordinations to the ionic radius of silver in six coordinations, that is, the "ionic radius ratio" is 0.63. That is, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and the coverage was as low as 72%.

In addition, in sample 28, which was also evaluated as "x", only SrTiO ₃ as a common material was added to the internal electrode. In this case, Sr, which is an element at the A site in ABO ₃ of the perovskite structure, has 12 coordinations, but when it is dissolved in the A site of the illuminite structure, it has 6 coordinations, which is the coordination number of the A site of the illuminite structure. It is necessary to compare the ionic radius at the 6-coordinate position, and the ionic radius at the 6-coordinate position of Sr is 1.18 Å, as shown in Table 1. Therefore, the ratio of the ionic radius of Sr in six coordinations to the ionic radius of silver in six coordinations, that is, the "ionic radius ratio" is 1.03. Therefore, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and the coverage was as low as 70%.

In these samples 24 and 28, the "ion radius ratio" was outside the range of 0.89 or more and 1.02 or less, and SrTiO ₃ was discharged from the internal electrode portion, and the heat resistance of the internal electrode did not improve and the coverage It is assumed that the

In Experimental Examples 1 to 3 described above, the powder made of an ABO ₃ type oxide with a specific ionic radius as at least a part of the ceramic powder contained in the conductive paste is selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ . Although at least one type was used, other types may be used. In other words, in an ABO ₃ type oxide with a specific ionic radius, the ratio of the ionic radius of the A-site element in ABO ₃ to the 6-coordination ionic radius of silver contained in the conductive paste is 0. Any ABO ₃ type oxide may be used as long as it is .89 or more and 1.02 or less.

Embodiments of this invention include the following.

<1>
A conductive paste for forming internal electrodes of a multilayer ceramic capacitor, comprising a conductive metal powder, a ceramic powder, an organic solvent and an organic binder,
The conductive metal powder contains silver,
At least a portion of the ceramic powder has a ratio of the ionic radius of the element at the A site in ABO ₃ at the 6-coordination to the ionic radius at the 6-coordination of silver from 0.89 to 1.02. A conductive paste that is a powder consisting of an ABO ₃ type oxide with a specific ionic radius.

<2>
The conductive paste according to <1>, wherein the ABO ₃ type oxide with the specific ionic radius has an illuminite crystal structure.

<3>
The conductive paste according to <2>, wherein the ABO ₃ type oxide having the specific ionic radius is at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ .

<4>
10% by volume or more of the ceramic powder is a powder consisting of an ABO ₃ type oxide having the specific ionic radius, and the remainder of the ceramic powder is mainly composed of at least one selected from BaTiO ₃ , SrTiO ₃ and CaZrO ₃ . The conductive paste according to any one of <1> to <3>, which is a powder.

1 Multilayer ceramic capacitor 2 Laminated body 3 Dielectric layer 4, 5 Internal electrode 6, 7 External electrode

Claims (4)

A conductive paste for forming internal electrodes of a multilayer ceramic capacitor, comprising a conductive metal powder, a ceramic powder, an organic solvent and an organic binder,
The conductive metal powder contains silver,
At least a portion of the ceramic powder has a ratio of the ionic radius of the element at the A site in ABO ₃ at the 6-coordination to the ionic radius at the 6-coordination of silver from 0.89 to 1.02. A conductive paste that is a powder consisting of an ABO ₃ type oxide with a specific ionic radius. The conductive paste according to claim 1, wherein the ABO ₃ type oxide of the specific ionic radius has an illuminite crystal structure. The conductive paste according to claim 2, wherein the ABO ₃ type oxide having the specific ionic radius is at least one selected from AgTiO ₃ , EuTiO ₃ and NaTiO ₃ . 10% by volume or more of the ceramic powder is a powder consisting of an ABO ₃ type oxide having the specific ionic radius, and the remainder of the ceramic powder is mainly composed of at least one selected from BaTiO ₃ , SrTiO ₃ and CaZrO ₃ . The conductive paste according to any one of claims 1 to 3, which is a powder.

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