WO2020090415A1

WO2020090415A1 - Ni paste and layered ceramic capacitor

Info

Publication number: WO2020090415A1
Application number: PCT/JP2019/040151
Authority: WO
Inventors: 寛志岡村; 秋本　裕二
Original assignee: 昭栄化学工業株式会社
Priority date: 2018-10-31
Filing date: 2019-10-11
Publication date: 2020-05-07
Also published as: JPWO2020090415A1; TW202029222A; CN112955980B; CN112955980A; JP7338634B2; KR20210084536A; TWI812799B

Abstract

Provided is a Ni paste characterized by containing (A) an electrically conductive powder comprising mainly Ni, (B) a binder resin, (C) an organic solvent and (D) a pyrochlore type oxide containing Sn and Ta and/or Nb, with the content of the pyrochlore type oxide being 0.05-2.0 parts by mass relative to 100 parts by mass of the electrically conductive powder (A) comprising mainly Ni. Provided by the present invention is a Ni paste for an internal electrode, which can minimize a reduction in melting point caused by solid solution of Sn into Ni and can improve load life at high temperature. The present invention can also provide a layered ceramic capacitor in which the thickness of a dielectric layer can be further reduced and which exhibits excellent reliability even if a voltage having a high electric field strength is applied.

Description

Ni paste and multilayer ceramic capacitor

The present invention relates to a Ni paste for forming internal electrodes for manufacturing a highly reliable multilayer ceramic capacitor, and a multilayer ceramic capacitor manufactured using this Ni paste.

Demand for miniaturization and large capacity for multilayer ceramic capacitors is increasing with the recent development of electronics technology. In order to meet these requirements, thinning of the dielectric layer that constitutes the monolithic ceramic capacitor has been promoted. However, when the dielectric layer is thinned, the electric field strength applied per layer becomes relatively high. Therefore, it is required to improve reliability when a voltage is applied.

Here, the monolithic ceramic capacitor is generally manufactured as follows. First, a dielectric ceramic raw material powder is dispersed in a resin binder and formed into a sheet, and a ceramic green sheet is formed into an inorganic electrode containing conductive powder and optionally ceramic powder, a resin binder, and an internal electrode mainly containing a solvent. The conductive paste is printed in a predetermined pattern and dried to remove the solvent and form an internal electrode dry film. Next, a plurality of the obtained ceramic sheets having the internal electrode dry film are stacked, pressure-bonded to form a laminated body, cut into a predetermined shape, and then fired at a high temperature to obtain a ceramic body. After that, a conductive paste for external electrodes is applied to both end faces of the ceramic body and then fired to obtain a laminated ceramic capacitor. The external electrodes may be formed by applying an external electrode paste to an unfired laminate and firing the ceramic bodies at the same time. As the internal electrode, one using Ni as a main component is known (for example, Patent Document 1).

When manufacturing a monolithic ceramic capacitor using Ni as a main component for the internal electrodes, it is necessary to perform firing in a reducing atmosphere in order to prevent oxidation of Ni. At this time, oxygen deficiency is introduced into the dielectric layer. However, there is a problem in that it causes a decrease in high temperature load life.

Therefore, in Patent Document 2, by using an internal electrode in which Sn is solid-dissolved in Ni, the height of the electrical barrier at the interface between the dielectric layer and the electrode layer is changed, and the invention is intended to achieve a high temperature load life. Is listed.

JP 2001-101926 A WO2012 / 111592

However, when Sn is solid-dissolved in Ni, the melting point of Ni is lowered and the sintering is promoted, so that ball-up easily occurs at various places of the electrode layer during firing, which deteriorates the continuity of the electrode film. Then, the decrease in the continuity of the electrode film causes a decrease in the capacitance of the capacitor.

Therefore, an object of the present invention is to provide a Ni paste for internal electrodes, which can suppress the melting point drop due to Sn solid solution in Ni as much as possible and can improve the high temperature load life. Another object of the present invention is to provide a multilayer ceramic capacitor that exhibits excellent reliability even when the dielectric layer is made thinner and a voltage with high electric field strength is applied.

The above problems can be solved by the present invention described below.
That is, the present invention (1) includes (A) a conductive powder mainly containing Ni,
(B) a binder resin,
(C) an organic solvent,
(D) Pyrochlore-type oxide containing Sn and one or both of Ta and Nb, and
Containing
The content of the pyrochlore type oxide is 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the conductive powder (A) Ni as a main component.
The present invention provides a Ni paste.

Further, in the present invention (2), the content of the pyrochlore type oxide is 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the conductive powder mainly composed of (A) Ni. (1) Ni paste is provided.

Further, in the present invention (3), the pyrochlore type oxide is represented by the following general formula (1):
Sn ²⁺ _2-x M _z Sn ⁴⁺ _y O _{7-xy / 2} (1)
(In the formula, M is one or two of Ta and Nb, x is 0 to 0.6, y is 0 to 0.5, and y + z = 2.)
The Ni paste according to (1) or (2) is characterized in that it is a pyrochlore type oxide represented by.

Further, the present invention (4) is a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately laminated,
External electrodes formed on the outer surface of the ceramic laminate,
Equipped with
At the interface between the ceramic dielectric layer and the internal electrode layer, there is a complex oxide containing Sn and either or both of Ta and Nb.
The present invention provides a laminated ceramic capacitor characterized by the following.

Further, the present invention (5) is a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately laminated,
External electrodes formed on the outer surface of the ceramic laminate,
Equipped with
The internal electrode layers are formed of a fired product obtained by firing the Ni paste of any one of (1) to (3) at 900 to 1400 ° C.,
The present invention provides a laminated ceramic capacitor characterized by the following.

According to the present invention, it is possible to provide a Ni paste for internal electrodes, which can suppress the melting point drop due to solid solution of Sn in Ni as much as possible and can improve the high temperature load life. Further, according to the present invention, it is possible to provide a monolithic ceramic capacitor that exhibits excellent reliability even when the dielectric layer is made thinner and a voltage with high electric field strength is applied.

The Ni paste of the present invention is
(A) a conductive powder mainly containing Ni,
(B) a binder resin,
(C) an organic solvent,
(D) Pyrochlore-type oxide containing Sn and one or both of Ta and Nb, and
Containing
The content of the pyrochlore type oxide is 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the conductive powder containing (A) Ni as a main component.
Is a Ni paste.

The Ni paste of the present invention is suitably used for forming internal electrodes of a laminated ceramic capacitor, and is also applicable to other ceramic electronic components such as a laminated ceramic actuator.

The Ni paste of the present invention includes at least one of (A) Ni-based conductive powder, (B) binder resin, (C) organic solvent, (D) Sn, and Ta and Nb. Or a pyrochlore-type oxide containing both of them.

The (A) Ni-based conductive powder according to the Ni paste of the present invention is a powder that is used as a conductive powder in a Ni paste for forming internal electrodes and that mainly contains Ni. Examples of the conductive powder (A) containing Ni as a main component include a powder containing only metallic Ni. As the conductive powder mainly composed of (A) Ni, a composite powder of Ni and another compound, a mixed powder of Ni and another compound, a mixture of Ni and another, as long as the effects of the present invention are exhibited. Examples thereof include alloy powder with a metal. Examples of the composite powder of Ni and another compound include a composite powder in which the surface of the Ni powder is covered with a glassy thin film, a composite powder in which the surface of the Ni powder is covered with an oxide, and a surface of the Ni powder. Examples thereof include composite powders which are surface-treated with an organometallic compound, a surfactant, fatty acids and the like. Examples of the mixed powder of Ni and another compound include a mixed powder of Ni powder and a co-material powder described later. The other metal that can be used in the alloy powder may be any metal that does not easily cause a melting point drop when alloyed with Ni, and examples thereof include Cu, Ag, Pd, Pt, Rh, Ir, Re, Ru and Os. , In, Ga, Zn, Bi, Pb, Fe, V, Y and the like. (A) The Ni content in the conductive powder mainly composed of Ni is not particularly limited as long as the effects of the present invention are exhibited, but is preferably 60% by mass or more, particularly preferably 80% by mass or more, and further preferably Is 100% by mass.

The average particle size of the (A) Ni-based conductive powder is not particularly limited, but is preferably 0.05 to 1.0 μm. When the average particle diameter of the conductive powder (A) mainly containing Ni is within the above range, a dense internal electrode layer having high smoothness can be easily formed. In addition, in the present specification, the symbol "-" indicating the numerical range indicates the range including the numerical values described before and after the symbol "-" unless otherwise specified. That is, for example, the notation “0.05 to 1.0” is synonymous with “0.05 or more and 1.0 or less” unless otherwise specified.

In the Ni paste of the present invention, the content of the (A) Ni-based conductive powder is not particularly limited, and is usually 30 to 30 in consideration of the finish viscosity, printability, storage stability, etc. of the Ni paste. It is appropriately selected within the range of 95% by mass. The content of the (A) Ni-based conductive powder in the Ni paste of the present invention may be selected in the range of 50 to 95 mass%.

The (B) binder resin relating to the Ni paste of the present invention is not particularly limited as long as it can be used as a conductive paste for forming internal electrodes. The (B) binder resin is generally used as a conductive paste for forming internal electrodes, for example, a cellulose resin such as ethyl cellulose, an acrylic resin, a methacrylic resin, a butyral resin, an epoxy resin, a phenol resin, Examples include rosin.

The content of the (B) binder resin in the Ni paste of the present invention is not particularly limited, and is usually 0.1 to 30 parts by mass, preferably 100 parts by mass of the conductive powder mainly containing (A) Ni. 1 to 15 parts by mass.

The (C) organic solvent related to the Ni paste of the present invention is not particularly limited as long as it can dissolve the (B) binder resin, and examples thereof include alcohol-based, ether-based, ester-based and hydrocarbon-based solvents and the like. Mixed solvent of.

The pyrochlore type oxide containing (D) Sn and / or one or both of Ta and Nb according to the Ni paste of the present invention is a composite oxide of Sn and Ta, and Sn and Nb. It is a composite oxide or a composite oxide composed of Sn, Ta, and Nb, and is an oxide having a pyrochlore type structure. Since the Ni paste of the present invention contains the pyrochlore type oxide containing (D) Sn and either or both of Ta and Nb, the high temperature load life of the laminated ceramic capacitor after firing is improved. (D) The pyrochlore type oxide containing Sn and one or both of Ta and Nb may contain a metal element other than Sn, Ta and Nb as long as the effect of the present invention is exhibited.

In the Ni paste of the present invention, the content of the pyrochlore type oxide containing (D) Sn and one or both of Ta and Nb is set to 100 parts by mass of the conductive powder mainly composed of (A) Ni. On the other hand, the amount is 0.05 to 2.0 parts by mass, preferably 0.1 to 0.6 parts by mass. When the content of the pyrochlore type oxide containing (D) Sn and either or both of Ta and Nb in the Ni paste of the present invention is in the above range, the content of the pyrochlore type oxide on the electrode layer and the dielectric layer side is increased. Element diffusion is suppressed as much as possible, and the high temperature load life is improved efficiently and surely. On the other hand, if the content of the pyrochlore type oxide containing (D) Sn and one or both of Ta and Nb in the Ni paste exceeds the above range, the improvement in high temperature load life tends to decrease. In addition, the variation in life becomes large. Further, if the content of the pyrochlore type oxide containing (D) Sn and one or both of Ta and Nb in the Ni paste is less than the above range, the effect of improving the high temperature load life can be obtained. Absent.

(D) A pyrochlore-type oxide containing Sn and one or both of Ta and Nb has a pyrochlore structure based on Sn ₂ (Ta, Nb) ₂ O _7. As is known, the pyrochlore structure can maintain a single phase within the range represented by the following general formula (1).

The (D) pyrochlore-type oxide containing Sn and one or both of Ta and Nb is preferably the following general formula (1):
Sn ²⁺ _2-x M _z Sn ⁴⁺ _y O _{7-xy / 2} (1)
(In the formula, M is one or two of Ta and Nb, x is 0 to 0.6, y is 0 to 0.5, and y + z = 2.)
It is a pyrochlore type oxide represented by. In the pyrochlore type oxide represented by the general formula (1), the M element may be only Ta, only Nb, or a combination of Ta and Nb. That is, in the pyrochlore type oxide represented by the general formula (1), the molar ratio of Ta and Nb, which are M elements, is 100: 0 to 0: 100. According to the description of the general formula (1), Sn ₂ Ta ₂ O ₇ becomes Sn ²⁺ ₂ Ta ₂ O ₇ , but in the present specification, it will be referred to as Sn ₂ Ta ₂ O ₇ according to the convention. To do.

Examples of the method for adding the pyrochlore-type oxide (hereinafter also referred to as the component (D)) containing (D) Sn and one or both of Ta and Nb to the Ni paste of the present invention include: Examples include a method of adding the component (D) as a powder, a method of forming a powder of the component (D) into a slurry, and a method of coating the surface of the conductive powder mainly containing (A) Ni with the component (D). Be done. When the component (D) is used as a powder or a slurry, the average particle size of the component (D) is preferably 50% or less, and particularly preferably 30% or less of the average particle size of the conductive powder mainly composed of (A) Ni. .. Since the content of the component (D) in the Ni paste of the present invention is small, the average particle size of the component (D) within the above range allows more uniform dispersion in the electrode film after printing.

According to the experiments conducted by the present inventors, SnO and Ta ₂ O ₅ were weighed in such amounts that they would become pyrochlore type oxides after firing, and when they were added to Ni paste and fired, the high temperature load life was Although an improvement can be seen, it is smaller than the effect of the present invention.

The Ni paste of the present invention can contain a common material powder which is usually added to the Ni paste for forming the internal electrodes. The co-material powder optionally contained is for the purpose of approximating the sintering shrinkage behavior of the internal electrode to that of the dielectric layer, and the kind of the co-material powder is not particularly limited, but is not limited to the ceramic dielectric material. It is desirable to select the capacitor so that the change in the characteristics of the capacitor due to the reaction of is minimized. As the co-material powder, a general formula: ABO ₃ (where A is at least one of Ba, Ca and Sr, and B is Ti, Zr, etc.), which is commonly used in Ni pastes for forming internal electrodes, is used. And Hf)), for example, a perovskite-type oxide powder such as barium titanate, strontium zirconate, or calcium zirconate, and those to which various additives are added. Is preferred. The co-material powder preferably has the same composition as or a similar composition to the dielectric ceramic raw material powder used as the main component of the dielectric layer. The common material powder may be attached to the surface of the conductive powder containing (A) Ni as a main component and then mixed with other components in the Ni paste.

When the Ni paste of the present invention contains a co-material powder, the content of the co-material powder in the Ni paste of the present invention is (A) the total content of the co-material powder with respect to 100 parts by mass of the conductive powder mainly containing Ni. And is 30 parts by mass or less. When the content of the co-material powder in the Ni paste exceeds the above range, the electrode layer becomes thick and a structural defect is likely to occur, and the electrode layer becomes a discontinuous film.

The average particle diameter of the co-material powder is not particularly limited, but it is more preferable that it is 30% or less of the average particle diameter of the conductive powder mainly composed of (A) Ni, which is more effective in suppressing sintering and improving the denseness. It is preferable because Further, it is preferable that the total specific surface area of the co-material powder in the paste is larger than the total specific surface area of the conductive powder mainly composed of (A) Ni in order to enhance the effect of improving the high temperature load life. By selecting the average particle size and content of the co-material powder, the total specific surface area of the co-material powder in the paste is made larger than the total specific surface area of the conductive powder (A) Ni as a main component. You can However, if the average particle size of the co-material powder is too small, the sintering of the powder itself will be too fast due to the increase in the surface area, and the effect of suppressing the sintering of the conductive powder mainly containing Ni will be low. The average particle size of the material powder is preferably 0.01 μm or more.

In addition to the above, the Ni paste of the present invention may contain additives such as a plasticizer, a dispersant, and a surfactant, which are usually added to the Ni paste for forming the internal electrodes, if necessary. ..

The Ni paste of the present invention contains the above-mentioned (A) Ni-based conductive powder, (B) binder resin, (C) organic solvent, and (D) Sn and one or both of Ta and Nb. It is prepared by uniformly mixing and dispersing a pyrochlore-type oxide containing, and a co-material powder and other various additives, which are optionally added, according to a conventional method.

The monolithic ceramic capacitor of the present invention is manufactured by the following method using the Ni paste of the present invention.

First, the dielectric ceramic raw material powder is dispersed in a resin binder and formed into a sheet by a doctor blade method, a die coater method or the like to produce a ceramic green sheet containing the dielectric ceramic raw material powder. As the dielectric ceramic raw material powder for forming the dielectric layer, barium titanate-based, strontium zirconate-based, calcium strontium zirconate-based perovskite-type oxides, or some of the metal elements constituting these are used. A powder containing an ordinary perovskite-type oxide as a main component, such as one substituted with the metal element of, is used. If necessary, these raw material powders are mixed with various additives for adjusting the capacitor characteristics. The particle size of the raw material powder is preferably about 0.05 to 0.4 μm when the thickness of the dielectric ceramic layer is 5.0 μm or less. Then, the Ni paste of the present invention is applied on the obtained ceramic green sheet by a usual method such as screen printing and dried to remove the solvent, thereby forming an internal electrode paste dry film having a predetermined pattern. Next, a predetermined number of ceramic green sheets having the internal electrode paste film formed thereon are stacked and pressure-laminated to produce an unfired laminated body. Next, the obtained laminated body is cut into a predetermined shape and then fired at a high temperature to simultaneously sinter the dielectric layer and the electrode layer to obtain a laminated ceramic capacitor body. Thereafter, terminal electrodes are baked on both end faces of the element body to form the laminated ceramic capacitor of the present invention. The terminal electrode may be attached before firing the above-mentioned laminated body and fired at the same time as the laminated body.

The thus-obtained monolithic ceramic capacitor of the present invention is a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately laminated,
External electrodes formed on the outer surface of the ceramic laminate,
Equipped with
At the interface between the ceramic dielectric layer and the internal electrode layer, there is a complex oxide containing Sn and either or both of Ta and Nb.
Is a monolithic ceramic capacitor.

The ceramic dielectric layer according to the monolithic ceramic capacitor of the present invention is, as the dielectric ceramic raw material powder, a perovskite type oxide such as barium titanate-based, strontium zirconate-based, calcium strontium zirconate-based, or a metal element constituting these. These dielectric ceramic raw material powders are molded by using a powder containing an ordinary perovskite type oxide as a main component, such as one in which a part of is replaced with another metal element, and 900 to 1400 in a reducing atmosphere. It is formed by baking at a temperature of 1,100 to 1,300 ° C.

In the multilayer ceramic capacitor of the present invention, the internal electrode layers containing Ni are formed by using the Ni paste of the present invention, that is, the Ni paste of the present invention is screen-printed or the like to form a ceramic green for forming a dielectric layer. It is formed by molding on a sheet, drying and firing. Therefore, the internal electrode layer containing Ni according to the multilayer ceramic capacitor of the present invention includes “Sn and either or both of Ta and Nb, or both, at the interface between the ceramic dielectric layer and the internal electrode layer. "Composite oxides" are present. In the multilayer ceramic capacitor of the present invention, "a complex oxide containing Sn and one or both of Sn and Ta and Nb are present" is present at the interface between the ceramic dielectric layer and the internal electrode layer. By this, the melting point drop due to the solid solution of Sn in Ni is suppressed as much as possible and the high temperature load life is improved. Therefore, even if the dielectric layer is further thinned and a voltage with high electric field strength is applied, it is excellent. Demonstrate reliability.

It should be noted that the presence of "a complex oxide containing Sn and one or both of Sn and Ta or Nb" at the interface between the ceramic dielectric layer and the internal electrode layer means that TEM (transmission electron microscope) is present. ) And EDS (energy dispersive X-ray spectroscopy), WDS (wavelength dispersive X-ray spectroscopy), or EELS (electron energy loss spectroscopy).

The internal electrode layer containing Ni according to the laminated ceramic capacitor of the present invention is formed by firing the Ni paste of the present invention in a reducing atmosphere at 900 to 1400 ° C, preferably 1100 to 1300 ° C.

The external electrode of the monolithic ceramic capacitor of the present invention is not particularly limited as long as it can be used as the external electrode of the monolithic ceramic capacitor.

Further, the laminated ceramic capacitor of the present invention is a ceramic laminated body in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately laminated,
External electrodes formed on the outer surface of the ceramic laminate,
Equipped with
The internal electrode layers are formed of a fired product obtained by firing the Ni paste of the present invention at 900 to 1400 ° C.,
Is a monolithic ceramic capacitor.

In the laminated ceramic capacitor of the present invention, the internal electrode layers are formed by molding the Ni paste of the present invention on a ceramic green sheet for forming a laminated layer by screen printing or the like, drying and firing. .. The firing temperature of the Ni paste of the present invention is 900 to 1400 ° C., preferably 1100 to 1300 ° C., and the firing atmosphere is a reducing atmosphere.

Hereinafter, the present invention will be described based on specific experimental examples, but the present invention is not limited thereto.

(Example 1)
<Production of Ni paste and multilayer ceramic capacitor>
First, in order to obtain a pyrochlore type oxide having a composition of Sn ₂ Ta ₂ O ₇ , SnO powder and Ta ₂ O ₅ powder were weighed and mixed, respectively, and reduced with N ₂ -0.1% H ₂ -H ₂ O gas. After firing in an atmosphere at 1000 ° C., it was ground until the average particle size became 0.05 μm to produce a pyrochlore type oxide containing Sn and Ta. It was confirmed by XRD (X-ray diffraction) that the obtained product was a pyrochlore type oxide containing Sn and Ta.
Next, with respect to 100 parts by mass of spherical nickel powder having an average particle size of 0.3 μm, 10.0 parts by mass of BaTiO ₃ powder having an average particle size of 0.05 μm as an additive powder and 6.0 parts by mass of ethyl cellulose (binder resin) were used. Parts, 2.0 parts by mass of a surfactant, 1.0 part by mass of a plasticizer, and 100 parts by mass of dihydroterpineol acetate (organic solvent), and a pyrochlore-type oxidation containing Sn and Ta obtained above. The powders were mixed in the amounts shown in Table 1 and kneaded using a three-roll mill to prepare 12 kinds of Ni pastes.
Next, a polyvinyl butyral binder, ethanol, and an additive for adjusting the capacitor characteristics are added to BaTiO ₃ powder having an average particle size of 0.2 μm, which is the main component of the ceramic green sheet, and wet mixed by a media mill to prepare a ceramic slurry. did.
This ceramic slurry was formed into a sheet by a die coater method to prepare a ceramic green sheet having a thickness of 5.5 μm.
Subsequently, an Ni electrode paste was printed on the ceramic green sheet in a rectangular pattern of 1.5 mm × 3.0 mm and then dried to form an internal electrode dry film. The thickness of the internal electrode dry film was 1.5 μm. Ceramic green sheets having a dry film of the internal electrodes were stacked so that the dielectric effective layer was 50 layers, and pressure and pressure of 1250 kg / cm ² were applied at 90 ° C. for pressure bonding and molding to obtain an unfired ceramic laminate. ..
This ceramic laminate was heated to 700 ° C. in an atmosphere of N ₂ -0.1% H ₂ —H ₂ O gas to burn the binder, and then the oxygen partial pressure at 1220 ° C. was 1 × 10 ^{−. In} a reducing atmosphere consisting of ⁸ atm of N ₂ -0.1% H ₂ -H ₂ O gas, the temperature was raised at a heating rate of 5 ° C./min, and the temperature was maintained at 1220 ° C. for 2 hours to sinter and densify. After that, a multilayer ceramic body was obtained by performing reoxidation treatment at 1000 ° C. for 3 hours in a N ₂ —H ₂ O gas atmosphere in the cooling stage.
Then, a Cu paste for forming an external electrode containing Cu powder and a BaO-based glass frit is applied to both end faces of the monolithic ceramic body and baked at a temperature of 780 ° C. in an N ₂ atmosphere to form an external electrode. A multilayer ceramic capacitor was produced.
By performing this for all of the above 12 kinds of Ni pastes, the samples of sample numbers 1 to 12 in Table 1 were obtained. In addition, in Table 1, the sample with * added to the sample number is a comparative example that does not satisfy the requirements of the present invention.
The external dimensions of the obtained monolithic ceramic capacitor were: width (W): 1.6 mm, length (L): 3.2 mm, thickness (T): 0.7 mm, and the internal electrode layer had a thickness of 1. It was 2 μm, and the thickness of the ceramic dielectric layer interposed between the internal electrodes was 4.0 μm. The area of the counter electrode per one dielectric layer was 3.25 mm ² .

<Evaluation of characteristics>
Each of the monolithic ceramic capacitors manufactured as described above (samples Nos. 1 to 12 in Table 1) was subjected to a high temperature load test by the method described below, and the continuity of the internal electrode layers was evaluated and the dielectric constant was measured. The vicinity of the interface between the body layer and the internal electrode layer was observed.
(1) High temperature load test 15 samples from each of the sample numbers 1 to 12 were sampled and subjected to a high temperature load test under the conditions of 180 ° C. and 60 V, and the time required for the insulation resistance to decrease by one digit was determined for each lamination. It was the failure time of the ceramic capacitor. Then, this failure time was Weibull plotted to obtain MTTF (mean failure time).
The shape parameter m value obtained from the Weibull plot is for evaluating the variation of the failure time. The larger this m value is, the smaller the variation of the failure time is, which is desirable as a capacitor.
Table 1 also shows the evaluation results of MTTF and m value.
(2) Evaluation of Continuity of Internal Electrode Layer Each of the laminated ceramic capacitors of Sample Nos. 1 to 12 was cut along a plane orthogonal to the internal electrode layer and observed with a SEM (scanning electron microscope). The observation magnification was 1000 times, 10 internal electrodes were randomly selected from the observation visual field, and the ratio of the portion where the electrodes were present to the entire length was measured and evaluated as continuity. Here, the continuity of 95% or more was marked with ◯, and the continuity of less than 95% was marked with x, which is also shown in Table 1.
(3) Observation of the vicinity of the interface between the dielectric layer and the internal electrode layer Each of the laminated ceramic capacitor element bodies of Sample Nos. 1 to 12 was cut along a plane orthogonal to the internal electrode layer, and a region corresponding to the central portion of the chip was measured by FIB. It processed using the micro sampling processing method by (focused ion beam), and produced the sample for analysis thinned. This sample was observed with a high resolution TEM (transmission electron microscope). The observation location was near the interface between the dielectric layer and the internal electrode layer.

1) Addition amount (parts by mass) of pyrochlore type oxide powder containing Sn and Ta to 100 parts by mass of spherical nickel powder

As shown in Table 1, the sample with no added pyrochlore type oxide Sn _₂ Ta ₂ O ₇ (Sample No. 1), all the samples was added pyrochlore type oxide Sn _₂ Ta ₂ O ₇ MTTF increased in (Sample Nos. 2 to 12). When the addition amount of the pyrochlore-type oxide of Sn ₂ Ta ₂ O ₇ was 0.1 part by mass or more with respect to 100 parts by mass of the spherical nickel powder, the MTTF was doubled or more.
On the other hand, in all the samples (Sample Nos. 2 to 12) to which the pyrochlore type oxide of Sn ₂ Ta ₂ O ₇ was added, the existence of the compound oxide layer of Sn and Ta was confirmed between the dielectric layer and the internal electrode layer. We were able to. Therefore, it can be said that the improvement of MTTF correlates with the existence of the complex oxide layer of Sn and Ta.
Further, the m value, which is an index of the variation in failure time, shows a maximum when the amount of the pyrochlore-type oxide of Sn ₂ Ta ₂ O ₇ added is about 0.4 parts by mass with respect to 100 parts by mass of the spherical nickel powder, Then, when it was 0.7 parts by mass or more, the m value became smaller than that of the non-added one. This was consistent with that in the dielectric layer, grain growth was promoted in the vicinity of the internal electrode rather than in the internal region of the dielectric layer.
Further, the continuity of the internal electrodes is 98% or more in the sample numbers 1 to 11, and the addition amount of the pyrochlore type oxide of Sn ₂ Ta ₂ O ₇ is 3.0 parts by mass with respect to 100 parts by mass of the spherical nickel powder. In Sample No. 12, which was No. 2, the continuity was 93%, and the ball-up of the electrode film was remarkable.
From the above, in order to suppress the melting point lowering due to the solid solution to Ni as much as possible and improve the high temperature load life, 100 parts by mass of the spherical nickel powder is mixed with the pyrochlore type oxide of Sn ₂ Ta ₂ O ₇ . The amount added should be in the range of 0.05 to 2.0 parts by mass, and if it is in the range of 0.1 to 0.6 parts, MTTF should be doubled or more without lowering the m value It is possible to improve the high temperature load life efficiently and surely.

(Example 2)
The same experiment as in Example 1 was carried out except that the composition of the pyrochlore type oxide of Sn ₂ Ta ₂ O ₇ was Sn ²⁺ _1.865 Ta ₂ O _6.865 and Sn ²⁺ _1.75 Ta _1.75 Sn ⁴⁺ _0.25 O _6.625. As a result, both obtained the same results as in Example 1. That is, it was confirmed that the effect of the present invention was achieved by including the single-phase pyrochlore type oxide containing Sn and Ta in the Ni paste.

Claims

(A) a conductive powder mainly containing Ni,
(B) a binder resin,
(C) an organic solvent,
(D) Pyrochlore-type oxide containing Sn and one or both of Ta and Nb, and
Containing
The content of the pyrochlore type oxide is 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the conductive powder (A) Ni as a main component.
Ni paste characterized by:
The content of the pyrochlore type oxide is 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the conductive powder mainly containing (A) Ni. Ni paste.
The pyrochlore type oxide has the following general formula (1):
Sn 2+ 2-x M z Sn 4+ y O 7-xy / 2 (1)
(In the formula, M is one or two of Ta and Nb, x is 0 to 0.6, y is 0 to 0.5, and y + z = 2.)
The Ni paste according to claim 1, which is a pyrochlore-type oxide represented by:
A ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately laminated;
External electrodes formed on the outer surface of the ceramic laminate,
Equipped with
At the interface between the ceramic dielectric layer and the internal electrode layer, there is a complex oxide containing Sn and either or both of Ta and Nb.
Is a multilayer ceramic capacitor.
A ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately laminated;
External electrodes formed on the outer surface of the ceramic laminate,
Equipped with
The internal electrode layer is formed of a fired product obtained by firing the Ni paste according to any one of claims 1 to 3 at 900 to 1400 ° C.
Is a multilayer ceramic capacitor.