TWI881107B - Ni PASTE, LAMINATED CERAMIC CAPACITOR, AND METHOD OF FORMING DIFFUSION REGION IN LAMINATED CERAMIC CAPACITOR - Google Patents

Abstract

A Ni paste contains: (A) conductive powder a main component of which is Ni; (B) binder resin; (C) organic solvent; and at least one substance selected from the group consisting of (D1) an additive containing Ta in a range of 0.025 to 2.50 parts by mass in terms of Ta ₂O ₅per 100.0 parts by mass of (A) the conductive powder a main component of which is Ni, (D2) an additive containing Nb in a range of 0.010 to 1.80 parts by mass in terms of Nb ₂O ₅per 100.0 parts by mass of (A) the conductive powder a main component of which is Ni, (D3) stabilized zirconia (SZ) with a zirconia crystal structure stabilized by a stabilizer in a range of 0.05 10 ^-2to 2.20 10 ^-2moles per 100g of (A) the conductive powder a main component of which is Ni, and (D4) an additive containing Al in the range of 0.10 to 5.50 parts by mass in terms of Al ₂O ₃per 100.0 parts by mass of (A) the conductive powder a main component of which is Ni. With the present invention, it is possible to provide a Ni paste for an inner electrode that can improve high-temperature load lifetime without decreasing continuity of an electrode film.

Description

Ni paste and multilayer ceramic capacitor, and method for forming diffusion region in multilayer ceramic capacitor

The present invention relates to a Ni paste for forming internal electrodes for manufacturing high-reliability multilayer ceramic capacitors, and a multilayer ceramic capacitor manufactured using the same.

In recent years, with the development of electronic technology, the demand for miniaturization and high capacity of multilayer ceramic capacitors has increased. In order to meet these requirements, the dielectric layers that constitute multilayer ceramic capacitors are evolving towards thinning. However, if the dielectric layers are thinned, the electric field strength applied to each layer will increase relatively. Therefore, it is required to improve the reliability when voltage is applied.

Here, the laminated ceramic capacitor is generally manufactured as follows. First, the dielectric ceramic raw material powder is dispersed in a resin binder, and the conductive paste for the internal electrode, which mainly contains conductive powder and inorganic powder such as ceramic powder, resin binder and solvent, is printed into a predetermined pattern on the thinned ceramic green sheet, and the solvent is removed by drying to form an internal electrode dry film. Then, a plurality of ceramic sheets with the obtained internal electrode dry film are stacked, pressed and bonded to form a laminate, and then cut into a predetermined shape and calcined at a high temperature to obtain a ceramic matrix. Then, after applying the conductive paste for the external electrode to both end surfaces of the ceramic substrate, the ceramic substrate is calcined to obtain a laminated ceramic capacitor. In addition, the external electrode is applied to the uncalcined laminate, and the external electrode paste can also be calcined at the same time as the ceramic substrate. Therefore, it is known that the internal electrode uses Ni as the main component (for example, Patent Document 1).

When the internal electrode uses Ni as the main component to manufacture a multilayer ceramic capacitor, in order to prevent Ni oxidation, it must be calcined in a reducing environment. At this time, oxygen vacancies will be introduced into the dielectric layer, which will become a problem that causes a decrease in high-temperature load life.

Therefore, Patent Document 2 states: By using an internal electrode in which Sn is solid-dissolved in Ni, the electron barrier height at the interface between the dielectric layer and the electrode layer is changed, thereby achieving an invention that increases the high-temperature load life.

[Prior Art Literature] [Patent Literature]

[Patent document 1] Japanese Patent Publication No. 2001-101926

[Patent Document 2] WO2012/111592

However, if Sn is dissolved in Ni, the melting point of Ni will be lowered and sintering will be accelerated. Therefore, ball-up will easily occur throughout the electrode layer during sintering, resulting in a decrease in the continuity of the electrode film. However, the reduced continuity of the electrode film will lead to a reduced capacity of the capacitor.

Therefore, the purpose of the present invention is to provide a Ni paste for internal electrodes that can improve the high-temperature load life without reducing the continuity of the electrode film. In addition, the purpose of the present invention is to provide a multilayer ceramic capacitor that can still show excellent reliability even if the dielectric layer is thinner and a high electric field strength voltage is applied.

The inventors of the present invention have conducted in-depth research to solve the above-mentioned problem and have found that by adding at least one selected from the group consisting of (D1) Ta-containing additives, (D2) Nb-containing additives, (D3) stabilized zirconia (SZ), and (D4) Al-containing additives to the Ni paste for internal electrodes containing (A) conductive powder mainly containing Ni in a predetermined ratio relative to (A) conductive powder mainly containing Ni, the continuity of the electrode film can be prevented from being reduced and the high-temperature load life can be improved, thereby completing the present invention.

That is, the Ni paste provided by the present invention (1) comprises: (A) a conductive powder mainly composed of Ni, (B) a binder resin, and (C) an organic solvent; and further comprises at least one selected from the following group: (D1) an additive containing 0.025 to _2.50 parts by mass of Ta in terms of _Ta2O5 relative to 100.0 parts by mass of the conductive powder mainly composed of Ni (A); (D2) an additive containing 0.010 to 1.80 parts by mass of Nb in terms of _Nb2O5 relative to 100.0 parts by mass of the conductive powder mainly composed of Ni (A); (D3) an additive containing 0.05× _10-2 to 2.20×10-4, a Nb in terms of Nb2O5 relative to 100 g of the conductive powder mainly composed of Ni (A ⁾ . ^-2 mol range, stabilized zirconium dioxide (SZ) whose crystal structure is stabilized by a stabilizer; and (D4) an additive containing 0.10 to 5.50 parts by mass of Al in terms of _Al2O3 relative to 100.0 parts by mass of the conductive powder (A ₎ mainly composed of Ni.

Furthermore, the present invention (2) provides a Ni paste as in (1), wherein when the Ta-containing additive (D1) is contained, the Ta-containing additive (D1) is contained in an amount in the range of 0.025 to 0.80 parts by mass in terms of Ta ₂ O ₅ relative to 100.0 parts by mass of the conductive powder (A) mainly comprising Ni.

Furthermore, the present invention (3) provides a Ni paste as in (1), wherein when the Nb-containing additive (D2) is contained, the Nb-containing additive (D2) is contained in an amount in the range of 0.010 to 0.50 parts by mass in terms of Nb ₂ O ₅ relative to 100.0 parts by mass of the conductive powder (A) mainly comprising Ni.

Furthermore, the present invention (4) provides the Ni paste as described in (1), wherein when the Ni _paste contains the stabilized zirconium dioxide ( _SZ ) (D3), the stabilizer is at least one selected from _Y2O3 , CaO, MgO and _Sc2O3 .

Furthermore, the present invention (5) provides a Ni paste as in (4), wherein, when containing the above-mentioned (D3) stabilized zirconium dioxide (SZ), the above-mentioned (D3) stabilized zirconium dioxide (SZ) contains the above-mentioned stabilizer in a range of more than 0.0 mol% and less than 45.0 mol%.

Furthermore, the present invention (6) provides a Ni paste as in (4), wherein, when containing the above-mentioned (D3) stabilized zirconium dioxide (SZ), the above-mentioned (D3) stabilized zirconium dioxide (SZ) contains the above-mentioned stabilizer in the range of 8.0~25.0 mol%.

Furthermore, the present invention (7) provides a Ni paste as described in any one of (1), (4) to (6), wherein when the stabilized zirconium dioxide (SZ) (D3) is contained, the stabilized zirconium dioxide (SZ) (D3) is contained in an amount of 0.05×10 ^-2 to 1.40×10 ^-2 mol relative to 100 g of the conductive powder (A) mainly composed of Ni.

Furthermore, the present invention (8) provides a Ni paste as in (1), wherein when the Al-containing additive (D4) is contained, the Al-containing additive (D4) is contained in an amount in the range of 0.10 to 2.30 parts by mass in terms of Al ₂ O ₃ relative to 100.0 parts by mass of the conductive powder (A) mainly comprising Ni.

Furthermore, the present invention (9) provides a Ni paste as described in any one of (1) to (8), wherein the content of the conductive powder (A) mainly Ni is 30.0 to 95.0 mass %.

Furthermore, the multilayer ceramic capacitor provided by the present invention (10) comprises: a ceramic multilayer body, which is formed by alternating a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni; and an external electrode, which is formed on the outer surface of the ceramic multilayer body; wherein the ceramic multilayer body contains at least one selected from the following group: (D1) Ta in the range of 0.025 to 2.50 parts by mass based on _Ta2O5 relative to 100.0 parts by mass of the conductive component containing Ni in (A); (D2) Nb2O in the range of 1.0 to 2.5 parts by mass based on _Nb2O5 relative to 100.0 parts by mass of the conductive component containing Ni in ( _A ); ₅ converted to Nb in the range of 0.010-1.80 parts by mass; and (D4) relative to 100.0 parts by mass of the conductive component containing Ni in (A), 0.10-5.50 parts by mass _{of Al2O3} converted to Al.

Furthermore, the multilayer ceramic capacitor provided by the present invention (11) comprises: a ceramic multilayer body, which is a stack of multiple ceramic dielectric layers and multiple internal electrode layers containing Ni in an alternating manner; and an external electrode, which is formed on the outer surface of the ceramic multilayer body; At the interface between the adjacent internal electrode layer and the ceramic dielectric layer and in the vicinity thereof, there is a diffusion region of at least one element selected from the group consisting of Ta, Nb, Zr, metal elements in the stabilizer, and Al.

Furthermore, the present invention (12) provides a multilayer ceramic capacitor as described in (11), wherein the metal element in the stabilizer is selected from at least one of Y, Ca, Mg and Sc.

Furthermore, the multilayer ceramic capacitor provided by the present invention (13) comprises: a ceramic multilayer body, which is a stack of multiple ceramic dielectric layers and multiple internal electrode layers containing Ni; and an external electrode, which is formed on the outer surface of the ceramic multilayer body; wherein the internal electrode layer is formed by calcining the Ni paste of any one of (1) to (9) at 900 to 1400°C.

According to the present invention, a Ni paste for internal electrodes can be provided that does not reduce the continuity of the electrode film and can improve the high-temperature load life. In addition, according to the present invention, a multilayer ceramic capacitor can be provided that can still show excellent reliability even if the dielectric layer is thinner and a high electric field strength voltage is applied.

FIG. 1 is a graph showing the relationship between Ta ₂ O ₅ and MTTF (with Ta ₂ O ₅ addition)/MTTF (without Ta 2 O 5 addition) in Table 1 in Example 1. FIG.

FIG. 2 is a graph showing the relationship between Nb ₂ O ₅ and MTTF (with Nb ₂ O ₅ addition)/MTTF (without Nb 2 O 5 addition) in Table 2 in Example 1. FIG.

FIG. 3 is a graph showing the relationship between MTTF (with ZrO ₂ addition)/MTTF (without addition) in Comparative Example 1 and MTTF (with YSZ addition)/MTTF (without addition) in Example 2. FIG.

FIG. 4 is a graph showing the relationship between MTTF (addition of YSZ) in Example 2 and MTTF (addition of ZrO ₂ ) in Comparative Example 1. FIG.

FIG. 5 is a relationship diagram of MTTF (YSZ addition)/MTTF (no addition) of Example 3 and MTTF (YSZ addition)/MTTF (ZrO ₂ addition) of Example 3. FIG.

FIG. 6 is a graph showing the relationship between Al ₂ O ₃ and MTTF (with Al ₂ O ₃ addition)/MTTF (without addition) in Table 8 in Example 5. FIG.

The Ni paste of the present invention comprises: (A) a conductive powder mainly composed of Ni, (B) a binder resin, and (C) an organic solvent; and further comprises: (D1) an additive containing 0.025 to 2.50 parts by mass of Ta in terms of Ta ₂ O ₅ relative to 100.0 parts by mass of the conductive powder mainly composed of Ni (A); (D2) an additive containing 0.010 to 1.80 parts by mass of Nb in terms of Nb ₂ O ₅ relative to 100.0 parts by mass of the conductive powder mainly composed of Ni (A); (D3) an additive containing 0.05×10 -2 to 2.20×10 ^-4 to 3.5 parts by mass of Nb in terms of Nb 2 O 5 relative to 100 g of the conductive powder mainly composed of Ni (A). ^-2 mol range, wherein the zirconia crystal structure is stabilized by using a stabilizer; and (D4) an additive containing 0.10 to 5.50 parts by mass of Al in terms of _Al2O3 relative to 100.0 parts by mass of the conductive powder (A ₎ mainly Ni.

At least one of the groups formed.

The Ni paste of the present invention may, for example, contain: (A) a conductive powder mainly composed of Ni, (B) a binder resin, and (C) an organic solvent, and further contain: ₍ D1) an additive containing Ta in an amount of 0.025 to 2.50 parts by mass in terms of _Ta2O5 relative to 100.0 parts by mass of the conductive powder mainly composed of Ni (A).

Furthermore, the Ni paste of the present invention may, for example, contain: (A) a conductive powder mainly composed of Ni, (B) a binder resin, and (C) an organic solvent, and further contain: (D2) an additive containing 0.010 to 1.80 parts by mass of Nb in terms of _Nb2O5 relative to 100.0 parts by mass of the conductive powder mainly composed _of Ni in (A).

Furthermore, the Ni paste of the present invention may, for example, contain: (A) a conductive powder mainly composed of Ni, (B) a binder resin, and (C) an organic solvent, and further contain: (D3) stabilized zirconium dioxide (SZ) in an amount of 0.05×10 ^-2 ~2.20×10 ^-2 mol relative to 100 g of the above-mentioned (A) conductive powder mainly composed of Ni, in which the zirconium dioxide crystal structure is stabilized by a stabilizer.

Furthermore, the Ni paste of the present invention may, for example, contain: (A) a conductive powder mainly composed of Ni, (B) a binder resin, and (C) an organic solvent, and further contain: (D4) an additive containing 0.10 to 5.50 parts by mass of Al in terms of _Al2O3 relative to 100.0 parts by mass of the conductive powder mainly composed _of Ni in (A).

The Ni paste of the present invention is suitable for forming internal electrodes of multilayer ceramic capacitors and other ceramic electronic parts such as multilayer ceramic actuators.

The Ni paste of the present invention contains at least: (A) conductive powder mainly composed of Ni, (B) binder resin, (C) organic solvent, and "at least one selected from the group consisting of (D1) Ta-containing additive, (D2) Nb-containing additive, (D3) stabilized zirconia (SZ), and (D4) Al-containing additive." That is, the Ni paste of the present invention contains at least: (A) conductive powder mainly composed of Ni, (B) binder resin, (C) organic solvent, and any one or more selected from (D1) Ta-containing additive, (D2) Nb-containing additive, (D3) stabilized zirconia (SZ), and (D4) Al-containing additive.

(A) of the Ni paste of the present invention is a conductive powder mainly composed of Ni, which is used as a conductive powder in the Ni paste for forming an internal electrode and mainly contains Ni powder. (A) The conductive powder mainly composed of Ni can be, for example, a powder consisting only of metal Ni. Moreover, (A) The conductive powder mainly composed of Ni can also be, for example, a composite powder of Ni and other compounds, a mixed powder of Ni and other compounds, an alloy powder of Ni and other metals, etc., provided that the effects of the present invention are achieved. The composite powder of Ni and other compounds can be, for example, a composite powder whose surface is coated with a glassy film, a composite powder whose surface is coated with an oxide, and a composite powder whose surface is treated with an organic metal compound, a surfactant, a fatty acid, etc. The mixed powder of Ni and other compounds can be, for example, a mixed powder of Ni powder and oxide powder, etc. In addition, other metals that can be used in alloy powders are metals that are not prone to melting point reduction when alloyed with Ni, or even if the melting point of the metal is reduced, as long as the content is within the extent that balling phenomenon does not occur, examples include: Cu, Ag, Pd, Pt, Rh, Ir, Re, Ru, Os, In, Ga, Zn, Bi, Pb, Fe, V, Y, etc. (A) The Ni content in the conductive powder mainly composed of Ni is not particularly limited as long as the effect of the present invention can be achieved. It is preferably 60.0 mass% or more, more preferably 80.0 mass% or more, and particularly preferably 100.0 mass%.

The average particle size of the conductive powder (A) mainly Ni is not particularly limited, and is preferably 0.05~1.0μm. By keeping the average particle size of the conductive powder (A) mainly Ni within the above range, a dense, smooth, and thin internal electrode layer can be easily formed. In addition, the symbol "~" in this specification that indicates a numerical range, unless otherwise stated, indicates a range including the numerical values recorded before and after the symbol "~". That is, for example, the expression "0.05~1.0" is synonymous with "0.05 or more and 1.0 or less" unless otherwise stated.

In the Ni paste of the present invention, (A) is mainly the content of Ni conductive powder, and there is no special restriction. If the processing viscosity, printability, storage stability and other factors of the Ni paste are considered, it can usually be appropriately selected within the range of 30.0~95.0 mass%.

The (B) binder resin of the Ni paste of the present invention is not particularly limited as long as it can be used in the conductive paste for forming the internal electrode. The (B) binder resin is generally used in the conductive paste for forming the internal electrode, and can be, for example, cellulose resins such as ethyl cellulose, acrylic resins, methacrylic resins, butyraldehyde resins, epoxy resins, phenolic resins, rosin, etc.

The content ratio of the (B) binder resin in the Ni paste of the present invention is not particularly limited. It is usually 0.1 to 30.0 parts by mass, preferably 1.0 to 15.0 parts by mass, relative to 100.0 parts by mass of the (A) conductive powder mainly composed of Ni.

The (C) organic solvent of the Ni paste of the present invention is not particularly limited as long as it can dissolve the (B) binder resin. Examples include alcohol, ether, ester, hydrocarbon solvents, and mixed solvents thereof.

The Ni paste of the present invention contains, in addition to (A) conductive powder mainly composed of Ni, (B) binder resin and (C) organic solvent, at least one selected from the group consisting of: (D1) Ta-containing additive, (D2) Nb-containing additive, (D3) stabilized zirconia (SZ), and (D4) Al-containing additive.

The component (D1) of the Ni paste of the present invention is a Ta-containing additive. The Ta-containing additive is provided that Ta ₂ O ₅ can be obtained after calcining the Ni paste. There are no particular limitations on the other aspects. For example, in addition to pure metal (Ta), inorganic compounds such as Ta oxides (Ta ₂ O ₅ , TaO ₂ ), sulfides (TaS ₂ ), halides (TaF ₅ , etc.), borides (TaB), etc., and organic metal compounds such as metal carbonyl compounds, metal alkoxides, and metal resinates, etc., can also be used. In the present invention, the Ta-containing additive is preferably Ta ₂ O ₅ .

When the Ni paste of the present invention contains (D1) a Ta-containing additive, the Ni paste of the present invention contains the Ta-containing additive in a ratio of preferably 0.025 to _2.50 parts by mass, more preferably 0.025 to 0.80 parts by mass, relative to 100.0 parts by mass of the (A) conductive powder mainly composed of Ni, when the Ta _{in the} Ta-containing additive is converted into Ta2O5.

The component (D2) of the Ni paste of the present invention is a Nb-containing additive. The Nb-containing additive is not particularly limited, provided that Nb ₂ O ₅ can be obtained after calcining the Ni paste. For example, in addition to pure metal (Nb), inorganic compounds such as Nb oxides (Nb ₂ O ₅ , NbO ₂ ), sulfides (NbS ₂ ), halides (NbF ₅ , etc.), borides (NbB), etc., and organic metal compounds such as metal carbonyl compounds, metal alkoxides, and metal resins can also be used. In the present invention, the Nb-containing additive is preferably Nb ₂ O ₅ .

When the Ni paste of the present invention contains (D2) a Nb-containing additive, the Ni paste of the present invention contains the Nb-containing additive in a ratio of preferably 0.010 to _1.80 parts by mass, more preferably 0.010 to 0.50 parts by mass, based on Nb in the Nb-containing additive converted into _Nb2O5 , relative to 100.0 parts by mass of the conductive powder (A) mainly comprising Ni.

The component (D3) of the Ni paste of the present invention is stabilized zirconia (SZ) whose crystal structure is stabilized by a stabilizer. The stabilized zirconia (SZ) is obtained by dissolving the stabilizer in zirconia (ZrO ₂ ) and introducing a divalent or trivalent metal element at the tetravalent Zr position, so that the crystal structure of zirconia (ZrO ₂ ) does not change with temperature changes and is stabilized.

The stabilizer is not particularly limited as long as it can stabilize zirconium dioxide (ZrO ₂ ), and examples thereof include oxides of alkali earth metals such as MgO, CaO, SrO, and BaO; oxides of rare earth elements such as Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , _{Pr 2 O 3 , Nd 2} O ₃ , Sm _{2 O 3} , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O 3 , and Yb 2 O ₃ ; and one or more oxides selected from Bi ₂ O ₃ , In ₂ O ₃ , and the like.

Among them, the present invention preferably uses one or more selected from yttrium oxide (Y ₂ O ₃ ), calcium oxide (CaO), magnesium oxide (MgO) and sc ₂ O ₃ for stabilization. The stabilizer used to stabilize zirconium dioxide (SZ) may be one or a combination of two or more.

In addition, in this specification, when there is no specific stabilizer and it refers to all stabilized zirconia, there are cases where stabilized zirconia is described as "SZ". Also, when it refers to stabilized zirconia using yttrium oxide (Y ₂ O ₃ ), calcium oxide (CaO), magnesium oxide (MgO) and sulphur oxide (Sc ₂ O ₃ ) as a stabilizer, they are described as "YSZ", "CSZ", "MSZ" and "ScSZ" respectively. In addition, stabilized zirconia (SZ) containing X (mol%) of stabilizer is described as "X-SZ". For example, "3.0-YSZ" refers to stabilized zirconia (YSZ) stabilized with 3.0 mol% of yttrium oxide (Y ₂ O ₃ ).

The content of the stabilizer in the stabilized zirconia (SZ) is not particularly limited, but is preferably more than 0.0 mol% and less than 45.0 mol%, more preferably more than 0.0 mol% and less than 40.0 mol%, and particularly preferably 8.0-25.0 mol%. By keeping the content of the stabilizer in the stabilized zirconia (SZ) within the above range, the high temperature load life can be easily improved. In addition, the stabilizer content (X mol%) in the stabilized zirconia (SZ) is the percentage of the molar number of the oxide of the metal element in the stabilizer relative to the total molar number of the oxide of Zr and the metal element in the stabilizer [(molar number of the oxide of the metal element in the stabilizer/(molar number of the oxide of the metal element in the stabilizer + molar number of the oxide of Zr in the stabilized zirconia (SZ))) × 100] obtained by converting the Zr in the stabilized zirconia (SZ) and the metal element in the stabilizer into oxides. When converting the oxides, for example, Zr is converted into ZrO ₂ , Y is converted into Y ₂ O ₃ , Ca is converted into CaO, Mg is converted into MgO, and Sc is converted into Sc ₂ O ₃ , and the molar number is calculated. Furthermore, when the stabilized zirconium dioxide (SZ) contains two or more stabilizers, each metal element in the two or more stabilizers is converted into oxides, and the total molar number of the oxide conversions is set as the oxide-converted molar number of the metal element in the stabilizer.

When the Ni paste of the present invention contains (D3) stabilized zirconia (SZ), the content of (D3) stabilized zirconia (SZ) in the Ni paste of the present invention is preferably 0.05×10 ^-2 ~2.20×10 ^-2 mol, more preferably 0.05×10 ^-2 ~1.40×10 ^-2 mol, in 100.0 g of (A) conductive powder mainly composed of Ni. By setting the content of (D3) stabilized zirconia (SZ) within the above range, the high temperature load life can be improved. In addition, although it is the content of stabilized zirconia (SZ) in Ni paste, the Zr in the stabilized zirconia (SZ) and the metal elements in the stabilizer are converted into oxides respectively, and the total mole conversion of the oxides of Zr and the metal elements in the stabilizer is obtained. By calculating the mole number in 100.0g of the conductive powder (A) mainly Ni, the content of stabilized zirconia (SZ) in Ni paste can be calculated.

The component (D4) of the Ni paste of the present invention is an Al additive. The Al additive is not particularly limited, provided that Al ₂ O ₃ can be obtained after calcining the Ni paste. For example, in addition to pure metal (Al), it may also be inorganic compounds such as Al oxide (Al ₂ O ₃ ), sulfide (Al ₂ S ₃ ), halide (AlF ₃ , etc.), boride (AlB ₂ ), nitride (AlN), carbide (Al ₄ C ₃ ), hydroxide (Al(OH) ₃ ), phosphate (AlPO ₄ ), sulfate (Al ₂ (SO ₄ ) ₃ ), and organic metal compounds such as metal alkoxides and metal resins. In the present invention, the Al-containing additive is particularly preferably Al ₂ O ₃ .

When the Ni paste of the present invention contains (D4) an Al-containing additive, the Ni paste of the present invention contains the Al-containing additive in a ratio of 0.10 to 5.50 parts by mass, preferably 0.10 to _2.30 parts by mass, relative to 100.0 parts by mass of the conductive powder (A) mainly comprising Ni, when Al in the Al _- containing additive is converted into Al2O3.

The Ni paste of the present invention may also contain in combination: (D1) Ta-containing additive, (D2) Nb-containing additive, (D3) stabilized zirconia (SZ), and (D4) Al-containing additive.

The mechanism by which the Ni paste of the present invention can achieve the effect of the present invention by containing at least one selected from the group consisting of (D1) Ta-containing additives, (D2) Nb-containing additives, (D3) stabilized zirconia (SZ), and (D4) Al-containing additives in the above-mentioned content ratio has not been clarified. However, according to the tests and studies of the inventors, it was observed that most of the Ta component, Nb component, stabilized zirconia (SZ) component or Al component contained in the Ni paste will move toward the ceramic dielectric layer during the calcination of the paste, resulting in the formation of a diffusion region (diffusion layer) containing a high concentration of Ta, Nb, Zr and metal elements in the stabilizer, or Al at the interface and its vicinity between the calcined ceramic dielectric layer and the internal electrode layer. In addition, the "interface and its vicinity" in the present invention refers to the area from the interface between the ceramic dielectric layer and the internal electrode layer, which is 1/16 of the thickness of the ceramic dielectric layer in the direction of the dielectric layer, to the area from the interface to the internal electrode layer, which is 1/2 of the thickness of the internal electrode layer.

The inventors of the present invention speculate that the existence of the diffusion region (diffusion layer) may cause the migration speed of oxygen vacancies in the ceramic dielectric layer toward the cathode to decrease during the high-temperature load life test, resulting in the inability to increase the life.

In addition, when using Ni paste containing (D3) stabilized zirconia (SZ), even if common material powder containing Zr is used, since the composition of the common material powder is the same as or similar to that of the ceramic dielectric layer, even if the Zr element diffuses from the internal electrode layer to the ceramic dielectric layer during calcination, the concentration distribution of the Zr element in the ceramic dielectric layer will hardly change. Therefore, the formation of a diffusion region (diffusion layer) containing high concentrations of Zr and metal elements in the stabilizer observed at and near the interface between the ceramic dielectric layer and the internal electrode layer can be considered to be caused by stabilized zirconia (SZ) contained in the Ni paste in addition to the common material powder.

Moreover, stabilized zirconia (SZ) introduces oxygen vacancies into zirconia (ZrO ₂ ). The more stabilizers there are, the more oxygen vacancies there are. By making the Ni paste contain stabilized zirconia (SZ), the concentration of oxygen vacancies near the interface can be increased compared to the case of containing unstabilized zirconia (ZrO ₂ ). As a result, in the high-temperature load life test, the oxygen vacancies inside the dielectric layer are not easy to move toward the electrode interface (cathode), which can further improve the high-temperature load life. On the other hand, when the stabilizer is excessive, the oxygen vacancy concentration is too high, which can be considered to cause a sharp decrease in the high-temperature load life characteristics.

Furthermore, the inclusion of Ta, Nb, SZ, or Al in the internal electrode layer after calcination does not lower the melting point of Ni, and therefore does not adversely affect the continuity of the electrode film. However, in the ceramic dielectric layer, if the concentration of Ta, Nb, SZ, or Al in the diffusion layer becomes too high, the wettability with Ni will decrease, which will adversely affect the continuity of the electrode film.

If the content of (D1) Ta additive, (D2) Nb additive, (D3) stabilized zirconia (SZ), or (D4) Al additive in the Ni paste is less than the above range, the effect of improving the high temperature load life cannot be achieved. If it exceeds the above range, the Ta component, Nb component, stabilized zirconia (SZ) component, or Al component diffused in the ceramic dielectric layer will generate crystal grain growth, resulting in a decrease in the high temperature load life.

The Ni paste of the present invention may further contain common material powders that are usually added to Ni pastes for forming internal electrodes. The common material powders may be arbitrarily contained in order to make the sintering shrinkage behavior of the internal electrode similar to that of the dielectric layer. The type of the common material powder is not particularly limited, and it is best to select the common material powder in such a way that the change in capacitor characteristics caused by the reaction with the ceramic dielectric is minimized. The common material powder is preferably a ceramic powder represented by the general formula ABO ₃ (wherein A is at least one of Ba, Ca and Sr, and B is at least one of Ti, Zr and Hf) used in Ni pastes for forming internal electrodes, such as barium titanate, strontium zirconate, calcium zirconate and other calcium titanate-type oxide powders, and various additives added thereto. The common material powder is preferably the same composition as the dielectric ceramic raw material powder used as the main component of the dielectric layer, or a similar composition. In addition, the common material powder can be attached to the surface of the conductive powder (A) mainly Ni in advance and then mixed with other components in the Ni paste.

When the Ni paste of the present invention contains common material powder, the content ratio of the common material powder in the Ni paste of the present invention is a ratio of 30.0 mass parts or less relative to 100.0 mass parts of (A) conductive powder mainly composed of Ni. If the content ratio of the common material powder in the Ni paste exceeds the above range, the electrode layer will not only become thicker and structural defects will occur easily, but also make the electrode layer a discontinuous film.

The average particle size of the common material powder is not particularly limited. From the perspective of exhibiting a better sintering inhibition effect and a density improvement effect, it is preferably less than 30% of the average particle size of the conductive powder (A) mainly composed of Ni. In addition, from the perspective of improving the high-temperature load life effect, the total specific surface area of the common material powder in the paste is preferably greater than the total specific surface area of the conductive powder (A) mainly composed of Ni. In addition, by selecting the average particle size and content of the common material powder, the total specific surface area of the common material powder in the paste can be greater than the total specific surface area of the conductive powder (A) mainly composed of Ni. However, if the average particle size of the common material powder is too small, the powder itself will sinter too quickly as the surface area increases, thereby reducing the effect of suppressing the sintering of the conductive powder mainly composed of Ni. Therefore, the average particle size of the common material powder is preferably greater than 0.01μm.

The Ni paste of the present invention may contain known compounds of metal elements other than the above mentioned without hindering the effect of the present invention. For various purposes, various compounds such as CaO, ZrO ₂ , Y ₂ O ₃ , Ti ₄ O ₇ , TiO ₂ , Co 3 O 4 , Fe ₂ O ₃ , La ₂ O ₃ , Li _{2 O} , MgO, MoO ₃ , SrO, V ₂ O ₅ , WO ₃ , CuO, etc. may also be added. In addition, _the present invention does not exclude the inclusion of Sn components. This is because Sn will form an alloy with Ni during calcination, resulting in a decrease in the melting point and promoting sintering, so it is judged that the above-mentioned balling phenomenon will occur. Therefore, if the Sn compound is one that does not alloy with Ni, or if the content is such that balling does not occur even if alloyed, it can be used together with (D1) Ta-containing additives, (D2) Nb-containing additives, (D3) stabilized zirconia (SZ), or (D4) Al-containing additives.

In addition to the above, the Ni paste of the present invention may contain additives such as plasticizers, dispersants, surfactants, etc. that are usually added to Ni paste for forming internal electrodes as needed.

The Ni paste of the present invention is prepared by uniformly mixing and dispersing the above-mentioned (A) conductive powder mainly composed of Ni, (B) binder resin, (C) organic solvent, "at least one selected from the group consisting of (D1) Ta-containing additive, (D2) Nb-containing additive, (D3) stabilized zirconia (SZ), and (D4) Al-containing additive", and other common material powders and various additives added as needed according to conventional methods.

The multilayer ceramic capacitor of the present invention is manufactured using the Ni paste of the present invention according to the following method.

First, the dielectric ceramic raw material powder is dispersed in a resin binder, and thin sheets are formed by a doctor blade method, a mold coating method, etc., to produce a ceramic green sheet containing the dielectric ceramic raw material powder. The dielectric ceramic raw material powder for forming the dielectric layer is a powder of calcite-titanic oxides such as barium titanate, strontium zirconate, and calcium strontium zirconate, or a part of the metal elements constituting the same is replaced by other metal elements, usually with calcite-titanic oxides as the main component. Various additives for adjusting the characteristics of the capacitor are mixed into the raw material powder as needed. When the particle size of the raw material powder is, for example, when the thickness of the dielectric ceramic layer is set to be less than 5.0μm, the average particle size is preferably about 0.05~0.4μm. Next, the Ni paste of the present invention is applied to the obtained ceramic green sheet by a common method such as screen printing, and the solvent is removed by drying to form a dried film of the internal electrode paste of a predetermined pattern. Next, the ceramic green sheets with the internal electrode paste film formed are overlapped by a predetermined number of sheets, and are subjected to heat pressing to produce an unfired laminate. Next, the obtained laminate is cut into a predetermined shape, and then calcined at a high temperature, and the dielectric layer and the electrode layer are sintered at the same time to obtain a laminated ceramic capacitor substrate. Then, the terminal electrodes are sintered on the two end faces of the substrate to obtain the laminated ceramic capacitor of the present invention. In addition, the terminal electrode can also be installed before the above-mentioned laminate is calcined and calcined simultaneously with the laminate.

The multilayer ceramic capacitor of the present invention thus obtained comprises: a ceramic laminate composed of a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni in an alternating manner; and an external electrode formed on the outer surface of the ceramic laminate; and the ceramic laminate contains at least one selected from the following group: (D1) Ta in the range of 0.025 to _2.50 parts by mass as calculated as _Ta2O5 relative to 100.0 parts by mass of the conductive component containing Ni (A); (D2) Nb2O in the range of 1.0 to 2.5 parts by mass as calculated as _Nb2O5 relative to 100.0 parts by mass of the conductive component containing Ni (A); ₅ converted to Nb in the range of 0.010-1.80 parts by mass; and (D4) relative to 100.0 parts by mass of the conductive component containing Ni in (A), 0.10-5.50 parts by mass of Al converted to Al ₂ O ₃ .

Furthermore, the multilayer ceramic capacitor of the present invention comprises: a ceramic multilayer body formed by alternating a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni; and an external electrode formed on the outer surface of the ceramic multilayer body; wherein the external electrode is formed at and near the interface between the internal electrode layer and the ceramic dielectric layer (i.e., from the interface between the ceramic dielectric layer and the internal electrode layer to the outer electrode layer). A diffusion region (diffusion layer) having a peak concentration of at least one element selected from the group consisting of Ta, Nb, Zr, metal elements in the stabilizer, and Al is provided in any part of the region from a region 1/16 of the thickness of the ceramic dielectric layer in the direction of the dielectric layer to a region 1/2 of the thickness of the internal electrode layer in the direction of the internal electrode layer from the interface.

The above diffusion region is a region where the concentration of at least one element selected from the group consisting of Ta, Nb, Zr, metal elements in the stabilizer, and Al increases from the above internal electrode layer toward the above ceramic dielectric layer and decreases after reaching a concentration peak.

Furthermore, the metal element in the above stabilizer is preferably selected from at least one of Y, Ca, Mg and Sc.

The ceramic dielectric layer of the multilayer ceramic capacitor of the present invention is formed by using dielectric ceramic raw material powders such as barium titanate, strontium zirconate, calcium strontium zirconate, etc., or metal elements constituting the above are partially replaced by other metal elements, etc., usually with strontium titanate oxide as the main component, and the dielectric ceramic raw material powders are formed into sheets and calcined at 900~1400℃, preferably 1100~1300℃ in a reducing environment.

In the multilayer ceramic capacitor of the present invention, the internal electrode layer containing Ni is formed using the Ni paste of the present invention, that is, the Ni paste of the present invention is formed on a ceramic green sheet for dielectric layer formation by screen printing, etc., dried, and then calcined. As mentioned above, most of the Ta component, Nb component, stabilized zirconia (SZ) component, or Al component contained in the Ni paste will move from the internal electrode layer to the ceramic dielectric layer during calcination, and a diffusion region (diffusion layer) containing Ta, Nb, Zr, metal elements in the stabilizer, or Al at a high concentration is formed at the interface between the internal electrode layer and the ceramic dielectric layer and in the vicinity thereof. In addition, in the diffusion region (diffusion layer), the concentration distribution of Ta, Nb, Zr, metal elements in the stabilizer, or Al is not uniform, but the concentration of Ta, Nb, Zr, metal elements in the stabilizer, or Al increases from the inner electrode layer toward the dielectric layer, and after reaching the concentration peak, the concentration distribution decreases. According to the research results so far, the concentration peak is estimated to be near the interface, but the position has not been accurately determined. That is, the thickness of the diffusion layer, the shape of the concentration slope, and the position of the concentration peak vary according to the calcination distribution such as calcination temperature, calcination time, and heating rate. For example, in the experimental example using a Ta-containing additive, when the temperature is rapidly raised and calcined for a short time, a diffusion layer is formed in which the Ta component diffuses from the inner electrode layer to the dielectric layer, and in the dielectric layer, Ta is only concentrated at a position very close to the interface with the inner electrode layer. In another experimental example, when calcination is performed for a long time, Ta is hardly observed in the inner electrode layer, and a diffusion layer with a wider Ta concentration slope (concentration peak) is formed in the dielectric layer.

Therefore, the characteristic of the multilayer ceramic capacitor of the present invention is that the ceramic laminate with the dielectric and the internal electrode layer stacked contains: (D1) Ta in the range of 0.025-2.50 mass parts, preferably _0.025-0.80 mass parts, calculated as _Ta2O5 , relative to 100.0 mass parts of the conductive component (A) containing Ni; (D2) Nb in the range of 0.010-1.80 mass parts, preferably 0.010-0.50 mass parts, calculated as _Nb2O5 , relative to 100.0 mass parts of the conductive component (A) containing Ni; and ₍ D4) _Al2O5 in the range of 100.0 mass parts of the conductive component (A) containing Ni. _3. Select at least one of the group consisting of Al in the range of 0.10 to 5.50 parts by mass, preferably 0.10 to 2.30 parts by mass.

Furthermore, the multilayer ceramic capacitor of the present invention is characterized by having: a ceramic multilayer body composed of a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni in alternating layers; and an external electrode formed on the outer surface of the ceramic multilayer body; and a diffusion region (diffusion layer) of at least one element selected from the group consisting of Ta, Nb, Zr, metal elements in the stabilizer, and Al is provided at and near the interface between the internal electrode layer and the ceramic dielectric layer. The metal element in the stabilizer is preferably selected from at least one of Y, Ca, Mg and Sc.

Furthermore, the multilayer ceramic capacitor of the present invention utilizes the above characteristics to improve the high temperature load life, so even if the dielectric layer is thinner and a high electric field strength voltage is applied, it can still show excellent reliability.

In addition, the dielectric layer and the internal electrode layer contain Ta components, Nb components, stabilized zirconia (SZ) components, or Al components, and have a diffusion region (diffusion layer) with a concentration distribution that increases from the internal electrode layer toward the ceramic dielectric layer and decreases after reaching a concentration peak. This can be confirmed by combining elemental analysis techniques such as SEM (scanning electron microscope), TEM (transmission electron microscope), or STEM (scanning transmission electron microscope) with EDS (energy dispersive X-ray spectroscopy), WDS (wavelength dispersive X-ray spectroscopy), or EELS (electron energy loss spectroscopy).

In the multilayer ceramic capacitor of the present invention, the internal electrode layer containing Ni is formed by calcining the Ni paste of the present invention at 900~1400℃, preferably 1100~1300℃ in a reducing environment.

The external electrode of the multilayer ceramic capacitor of the present invention is based on the premise that it can be used as the external electrode of the multilayer ceramic capacitor, and there are no special restrictions on other aspects.

Furthermore, the multilayer ceramic capacitor of the present invention comprises: a ceramic multilayer body composed of a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni alternately stacked; and an external electrode formed on the outer surface of the ceramic multilayer body; wherein the internal electrode layer is formed by calcining the Ni paste of the present invention at 900-1400°C.

In the multilayer ceramic capacitor of the present invention, the internal electrode layer is formed by forming the Ni paste of the present invention on a ceramic green sheet for multilayer formation by screen printing, etc., and then drying and calcining. The calcination temperature of the Ni paste of the present invention is 900~1400℃, preferably 1100~1300℃, and the calcination environment is a reducing environment. That is, the internal electrode layer is formed by the calcined product of the Ni paste of the present invention at 900~1400℃, preferably 1100~1300℃.

The present invention is described below based on specific experimental examples, but the present invention is not limited to them.

[Implementation example] <<(D1) contains Ta additive and (D2) contains Nb additive>> (Implementation Example 1) <Manufacturing of Ni paste and multilayer ceramic capacitors>

With respect to 100.0 g of spherical nickel powder with an average particle size of 0.3 μm, Ta ₂ O ₅ or Nb ₂ O ₅ in the mass proportions shown in Table 1 or Table 2, 10.0 g of BaTiO ₃ powder with an average particle size of 0.05 μm of common material powder, 6.0 g of ethyl cellulose (binder resin), 2.0 g of surfactant, 1.0 g of plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent) were mixed and kneaded using a three-roll mill to prepare a Ni paste.

Next, polyvinyl butyraldehyde-based binder, ethanol, and additives for adjusting capacitor properties are added to BaTiO ₃ powder with an average particle size of 0.2 μm, which is the main component of the ceramic green sheet, and wet mixing is performed using a grinding medium disperser to prepare a ceramic slurry.

The ceramic slurry is formed into a thin sheet using a mold coating method to prepare a ceramic green sheet with a thickness of 5.5μm.

Next, Ni paste was printed on the ceramic green sheet in a 1.5 mm × 3.0 mm rectangular pattern, and dried to form an internal electrode dry film. The thickness of the internal electrode dry film was 1.5 μm. The ceramic green sheets with the internal electrode dry film were stacked in a manner such that the dielectric effective layer formed 50 layers, and pressed and formed at 90° ^C with a pressure of 1250 kg/cm2 to obtain an unfired ceramic laminate.

The ceramic laminate was heated at 700°C in an environment consisting of _N2-0.1 % _H2 - _H2O gas to burn the binder, and then heated at 1220°C in a reducing environment consisting of _N2-0.1 % _H2 - _H2O gas with an oxygen partial pressure of 1× ^10-8 atm at a heating rate of 5°C/min, and maintained at 1220°C for 2 hours to achieve sintering densification. Then, in the cooling stage, it was reoxidized at 1000°C for 3 hours in an _N2 - _H2O gas environment to obtain a laminated ceramic substrate.

Next, a Cu paste for forming external electrodes containing Cu powder and BaO-based glass frit is applied to both end surfaces of the multilayer ceramic substrate, and fired at 780°C in an _N2 environment to form external electrodes, thereby manufacturing a multilayer ceramic capacitor.

This step is applied to all the above Ni pastes to obtain the samples in Table 1 or Table 2. In addition, in Table 1 or Table 2, the samples with sample numbers marked with "*" are comparative examples that do not meet the requirements of the present invention.

The dimensions of the obtained multilayer ceramic capacitor are width (W): 1.6mm, length (L): 3.2mm, thickness (T): 0.7mm, the thickness of the internal electrode layer is 1.2μm, the thickness of the ceramic dielectric layer between the internal electrodes is 4.0μm. In addition, the area of the opposing electrode per dielectric layer is ^3.25mm2 .

<Evaluation of characteristics>

For each multilayer ceramic capacitor (samples in Table 1 and Table 2) manufactured as described above, a high temperature load test was performed according to the method described below, and the continuity of the internal electrode layer was evaluated. In addition, the interface between the ceramic dielectric layer and the internal electrode layer was observed, and it was confirmed that a diffusion region (diffusion layer) was formed in which the concentration of Ta or Nb increased from the internal electrode layer toward the ceramic dielectric layer and decreased after reaching a peak concentration.

(1) High temperature load test

15 samples were taken from each sample and subjected to high temperature load test at 180℃ and 60V. The time required for the insulation resistance to drop by one order of magnitude was set as the failure time of each multilayer ceramic capacitor. Then, the failure time was subjected to Weber plotting to obtain MTTF (mean time to failure). The evaluation results of MTTF are combined and recorded in Table 1 or Table 2, and are organized as shown in Figure 1 and Figure 2 respectively.

(2) Evaluation of the continuity of the internal electrode layer

Each multilayer ceramic capacitor of each sample was cut from the orthogonal plane of the internal electrode layer and observed using a SEM (scanning electron microscope). The observation magnification was 1000 times, and 10 internal electrodes were randomly selected from the observation field of view. The ratio of the electrode portion to the total length was measured, and the continuity was evaluated based on this. Here, the continuity was rated as "◎" for more than 90%, "○" for 80-90%, and "×" for less than 80%, and the results were recorded in Table 1 or Table 2.

[Table 1]

1) Mass fraction relative to 100 mass fraction of spherical nickel powder

2) Ratio of MTFF of each sample to MTFF of sample 1A (without Ta ₂ O ₅ addition) (MTFF of each sample/MTTF of sample 1A)

1) Mass fraction relative to 100 mass fraction of spherical nickel powder

2) Ratio of MTFF of each sample to MTFF of sample 1A (without Nb ₂ O ₅ addition) (MTFF of each sample/MTTF of sample 1A)

As shown in Tables 1 and 2, compared with the sample without Ta ₂ O ₅ or Nb ₂ O ₅ (sample number 1A), all samples (sample numbers 2A to 10A and 12A to 20A) mixed with Ta ₂ O ₅ or Nb ₂ O ₅ within the range specified in the present invention showed an increase in MTTF.

Furthermore, regarding the continuity of the internal electrodes, sample numbers 2A~7A and 12A~16A showed over 90%, and sample numbers 8A~10A and 17A~20A showed 80~90%.

On the other hand, the samples _{in which Ta2O5 or Nb2O5 was mixed beyond} the range specified in the present invention (sample numbers 11A and 21A) had lower MTTF than the sample without _Ta2O5 or _Nb2O5 (sample number _1A ), and the continuity of _the internal electrode was less than 80%.

From the above, it can be seen that in order to improve the high-temperature load life, relative to 100 mass parts of spherical nickel _powder , it is best to mix 0.025~2.50 mass parts of _{Ta2O5 and} 0.01~ _1.80 mass parts of _Nb2O5 . If the mixing range is 0.025~0.80 mass parts of _Ta2O5 and 0.01 _~ 0.50 mass parts of _Nb2O5 , the high-load life can be further improved without damaging the continuity of the internal electrode.

<<(D3) Stabilized zirconium dioxide (SZ)>> (Implementation Example 2 and Comparative Example 1) <Manufacturing of Ni paste and multilayer ceramic capacitors> (Preparation of Ni paste)

Comparative Example 1 is to prepare ZrO ₂ in the molar ratio shown in Table 3 relative to 100.0 g of spherical nickel powder with an average particle size of 0.3 μm, and further mix 10.0 g of BaTiO ₃ powder with an average particle size of 0.05 μm of common material powder, 6.0 g of ethyl cellulose (binder resin), 2.0 g of surfactant, 1.0 g of plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent), and use a three-roll mill to knead and prepare Ni paste.

In Example 2, the Ni paste was prepared in the same manner as in Comparative Example 1 except that 3.0 mol% yttrium oxide-stabilized zirconia (3.0-YSZ) was used in place of ZrO ₂ in the molar ratio shown in Table 4.

(Manufacturing of multilayer ceramic capacitors)

Next, polyvinyl butyraldehyde-based binder, ethanol, and additives for adjusting capacitor properties are added to BaTiO ₃ powder with an average particle size of 0.2 μm, which is the main component of the ceramic green sheet, and wet mixing is performed using a grinding medium disperser to prepare a ceramic slurry.

The ceramic slurry was formed into a thin sheet using a mold coating method to prepare a ceramic green sheet with a thickness of 5.5 μm .

Next, the Ni paste of Example 2 and Comparative Example 1 was printed on the ceramic green sheet in a 1.5 mm × 3.0 mm rectangular pattern, and then dried to form an inner electrode dry film. The thickness of the inner electrode dry film was 1.5 μm. The ceramic green sheets with the inner electrode dry film were stacked in a manner such that the dielectric effective layer formed 50 layers, and were pressed and formed at 90°C with a pressure of 1250 kg/ ^cm2 to obtain an unfired ceramic laminate.

The ceramic laminate was heated at 700°C in an environment consisting of _N2-0.1 % _H2 - _H2O gas to burn the binder, and then heated at 1220°C in a reducing environment consisting of _N2-0.1 % _H2 - _H2O gas with an oxygen partial pressure of 1× ^10-8 atm at a heating rate of 5°C/min, and maintained at 1220°C for 2 hours to achieve sintering densification. Then, in the cooling stage, it was reoxidized at 1000°C for 3 hours in an _N2 - _H2O gas environment to obtain a laminated ceramic substrate.

Next, a Cu paste for forming external electrodes containing Cu powder and BaO-based glass frit is applied to both end surfaces of the multilayer ceramic substrate, and fired at 780°C in an _N2 environment to form external electrodes, thereby manufacturing a multilayer ceramic capacitor.

This step was applied to all the above Ni pastes to obtain samples 1B to 21B in Table 3 or Table 4. In addition, in Table 3 or Table 4, the samples with sample numbers marked with "*" are comparative examples that do not meet the requirements of the present invention.

The dimensions of the obtained multilayer ceramic capacitor are width (W): 1.6mm, length (L): 3.2mm, thickness (T): 0.7mm, the thickness of the internal electrode layer is 1.2μm, the thickness of the ceramic dielectric layer between the internal electrodes is 4.0μm. In addition, the area of the opposing electrode per dielectric layer is ^3.25mm2 .

<Evaluation of characteristics>

For each of the multilayer ceramic capacitors (samples in Table 3 and Table 4) manufactured as described above, a high temperature load test was performed according to the method described below, and the continuity of the internal electrode layer was evaluated. In addition, the interface between the ceramic dielectric layer and the internal electrode layer was observed, and it was confirmed that a diffusion region (diffusion layer) was formed in which the concentration of Zr and/or the metal element Y in the stabilizer increased from the internal electrode layer toward the ceramic dielectric layer, and then decreased after reaching a peak concentration.

(1) High temperature load test

15 samples were taken from each sample and subjected to high temperature load test at 180℃ and 60V. The time required for the insulation resistance to drop by one order of magnitude was set as the failure time of each multilayer ceramic capacitor. Then, the failure time was subjected to Weber plotting to obtain MTTF (mean time to failure). The evaluation results of MTTF are combined and recorded in Table 3 or Table 4.

Furthermore, to compare Example 1 and Example 2, their respective MTTFs are organized as shown in Figure 3.

Furthermore, the MTTF of adding stabilized zirconium dioxide (3.0-YSZ) was calculated, and compared with the MTTF of adding zirconium dioxide (ZrO ₂ ) in Comparative Example 1, the results are summarized in Table 5 and FIG. 4 .

(2) Evaluation of the continuity of the internal electrode layer

Each multilayer ceramic capacitor of each sample was cut from the orthogonal plane of the internal electrode layer and observed using a SEM (scanning electron microscope). The observation magnification was 1000 times, and 10 internal electrodes were randomly selected from the observation field of view. The ratio of the electrode portion to the total length was measured, and the continuity was evaluated based on this. Here, the continuity was rated as "◎" for more than 90%, "○" for 80-90%, and "×" for less than 80%, and the results were recorded in Table 3 or Table 4.

1) Molar number relative to 100g of spherical nickel powder

2) The ratio of the MTTF of each sample to the MTTF of sample 1B (no additive) (MTTF of each sample/MTTF of sample 1B)

1) Molar number relative to 100g of spherical nickel powder

2) The ratio of the MTTF of each sample to the MTTF of sample 1B (no additive) (MTTF of each sample/MTTF of sample 1B)

1) Ratio of MTTF of the sample with 3.0-YSZ added to the sample with the same molar amount of ZrO ₂ added (MTTF of the sample with 3.0-YSZ added/MTTF of the sample with the same molar amount of ZrO ₂ added)

As shown in Tables 3 to 5 and Figures 3 to 4, all samples (Samples _12B to 20B) mixed with stabilized zirconia (3.0-YSZ) within the range specified in the present invention have increased MTTF compared to the sample without addition (Sample 1B) in which ZrO ₂ and stabilized zirconia (3.0-YSZ) are not mixed. In addition, all samples (Samples 12B to 20B) mixed with stabilized zirconia (3.0-YSZ) within the range specified in the present invention have improved MTTF compared to the samples (Samples 2B to 10B) added with the same mole of zirconia (ZrO 2).

Furthermore, the continuity of the internal electrode is more than 90% for samples 12B~18B and 80~90% for samples 19B~20B.

On the other hand, the sample (sample 21B) in which the stabilized zirconium dioxide (3.0-YSZ) was mixed beyond the range specified in the present invention had a lower MTTF than the sample (sample 11B) in which zirconium dioxide (ZrO ₂ ) was mixed, and the continuity of the internal electrode was less than 80%.

From the above, it can be seen that, relative to 100g of spherical nickel powder, by mixing 0.05×10 ^-2 ~2.20×10 ^-2 mol of stabilized zirconium dioxide (3.0-YSZ), the high-temperature load life can be improved compared to the case of no addition and the case of adding zirconium dioxide (ZrO ₂ ). If it is within the range of 0.05×10 ^-2 ~1.40×10 ^-2 mol, the high-load life can be further improved without damaging the continuity of the internal electrode.

(Implementation Example 3) <Manufacturing of Ni paste and multilayer ceramic capacitors> (Preparation of Ni paste and grease)

Stabilized zirconia (X-YSZ) powder stabilized with yttrium oxide (Y ₂ O ₃ ) at a content (X mol %) as shown in Table 6 was prepared at a molar ratio of 0.80×10 ^-2 relative to 100.0 g of spherical nickel powder having an average particle size of 0.3 μm. 10.0 g of BaTiO ₃ powder having an average particle size of 0.05 μm, which was a common material powder, 6.0 g of ethyl cellulose (binder resin), 2.0 g of a surfactant, 1.0 g of a plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent) were mixed and kneaded using a three-roll mill to prepare a Ni paste.

(Manufacturing of multilayer ceramic capacitors)

Except for using the above-mentioned Ni paste, the rest is the same as Example 2.

This step was applied to all the above Ni pastes to obtain samples 22B~28B in Table 6.

<Characteristics evaluation>

Except for using the samples obtained above, the rest is implemented in the same way as Example 2. The results are summarized in Table 6.

The ratio of the MTTF (Samples 16B, 22B~28B) when only the stabilizer content is changed without changing the stabilizer content to the MTTF (Sample 1B) when neither ZrO ₂ nor stabilizer YSZ is added is shown as the black dots (left side of the vertical axis) in Figure 5.

Furthermore, the ratio of the MTTF (samples 16B, 22B to 28B) with the same addition of stabilized zirconia (X-YSZ) to the MTTF (sample 6B) with the same addition of zirconia (ZrO ₂ ) [i.e., MTTF (X-YSZ) / MTTF (ZrO ₂ )] is shown as the square points (right side of the vertical axis) in FIG5 .

1) X refers to the mole % _{of Y2O3} in stabilized zirconium dioxide (YSZ).

2) The ratio of the MTTF of each sample to the MTTF of sample 1B (no additive) (MTTF of each sample/MTTF of sample 1B)

3) Ratio of MTTF of each sample to sample 6B with the same molar amount of _ZrO2 added (MTTF of each sample/MTTF of sample 6B)

As shown in Table 6 and Figure 5, there is no correlation between the stabilizer (Y ₂ O ₃ ) content in stabilized zirconium dioxide (YSZ) and the continuity of the electrode film. However, when the stabilizer (Y ₂ O ₃ ) content is above 50.0 mol%, the MTTF is lower than that of the comparative example with zirconium dioxide (ZrO ₂ ) added (Sample 6B) and the comparative example without addition (Sample 1B). Therefore, in the stabilized zirconium dioxide (YSZ) of the present invention, if the content of the stabilizer (Y ₂ O ₃ ) is in the range of more than 0.0 mol % and less than 45.0 mol %, good results can be obtained, preferably in the range of more than 0.0 mol % and less than 40.0 mol %, and more preferably in the range of 8.0-25.0 mol %.

(Implementation Example 4) <Manufacturing of Ni paste and multilayer ceramic capacitors> (Preparation of Ni paste)

A stabilized zirconium dioxide (10.0-SZ) powder containing 10.0 mol% of the stabilizer shown in Table 7 was prepared in a ratio of 0.80×10 ^-2 mol to 100.0 g of spherical nickel powder having an average particle size of 0.3 μm. 10.0 g of BaTiO ₃ powder having an average particle size of 0.05 μm, 6.0 g of ethyl cellulose (binder resin), 2.0 g of a surfactant, 1.0 g of a plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent) were mixed in a ratio of 0.80×10 -2 mol to 100.0 g of a spherical nickel powder having an average particle size of 0.3 μm. A three-roll mill was used to knead the mixture to prepare a Ni paste.

(Manufacturing of multilayer ceramic capacitors)

Except for using the above-mentioned Ni paste, the rest is the same as Example 2.

This step was applied to all the above Ni pastes to obtain samples 29B~31B in Table 7.

<Characteristics evaluation>

Except for using the samples obtained above, the rest are implemented in the same way as Example 2. The results are summarized in Table 7.

1) The ratio of the MTTF of each sample to the MTTF of sample 1B (no additive) (MTTF of each sample/MTTF of sample 1B)

2) Ratio of MTTF of each sample to sample _6B with the same molar amount of ZrO2 added (MTTF of each sample/MTTF of sample 6B)

From the results in Table 7, it can be seen that even if the stabilizer is calcium oxide (CaO), magnesium oxide (MgO), or Sc ₂ O ₃ , it can still improve the high temperature load life without reducing the continuity of the internal electrode film, just like yttrium oxide (Y ₂ O ₃ ).

<<(D4) Contains Al additives>> (Example 5) <Manufacturing of Ni paste and multilayer ceramic capacitors>

Al ₂ O ₃ in the mass proportions shown in Table 8 was mixed with 100.0 g of spherical nickel powder with an average particle size of 0.3 μm, 10.0 g of BaTiO ₃ powder with an average particle size of 0.05 μm as a common material powder, 6.0 g of ethyl cellulose (binder resin), 2.0 g of surfactant, 1.0 g of plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent) and kneaded using a three-roll mill to prepare a Ni paste.

Next, polyvinyl butyraldehyde-based binder, ethanol, and additives for adjusting capacitor properties are added to BaTiO ₃ powder with an average particle size of 0.2 μm, which is the main component of the ceramic green sheet, and wet mixing is performed using a grinding medium disperser to prepare a ceramic slurry.

The ceramic slurry was formed into a thin sheet using a mold coating method to prepare a ceramic green sheet with a thickness of 5.5 μm .

Next, Ni paste was printed on the ceramic green sheet in a 1.5 mm × 3.0 mm rectangular pattern, and dried to form an internal electrode dry film. The thickness of the internal electrode dry film was 1.5 μm. The ceramic green sheets with the internal electrode dry film were stacked in a manner such that the dielectric effective layer formed 50 layers, and pressed and formed at 90° ^C with a pressure of 1250 kg/cm2 to obtain an unfired ceramic laminate.

The ceramic laminate was heated at 700°C in an environment consisting of _N2-0.1 % _H2 - _H2O gas to burn the binder, and then heated at 1220°C in a reducing environment consisting of _N2-0.1 % _H2 - _H2O gas with an oxygen partial pressure of 1× ^10-8 atm at a heating rate of 5°C/min, and maintained at 1220°C for 2 hours to achieve sintering densification. Then, in the cooling stage, it was reoxidized at 1000°C for 3 hours in an _N2 - _H2O gas environment to obtain a laminated ceramic substrate.

Next, a Cu paste for forming external electrodes containing Cu powder and BaO-based glass frit is applied to both end surfaces of the multilayer ceramic substrate, and fired at 780°C in an _N2 environment to form external electrodes, thereby manufacturing a multilayer ceramic capacitor.

This step was applied to all the above Ni pastes to obtain the samples in Table 8. In addition, in Table 8, the samples with sample numbers marked with "*" are comparative examples that do not meet the requirements of the present invention.

The dimensions of the obtained multilayer ceramic capacitor are width (W): 1.6mm, length (L): 3.2mm, thickness (T): 0.7mm, the thickness of the internal electrode layer is 1.2μm, the thickness of the ceramic dielectric layer between the internal electrodes is 4.0μm. In addition, the area of the opposing electrode per dielectric layer is ^3.25mm2 .

<Evaluation of characteristics>

For each multilayer ceramic capacitor (sample in Table 8) manufactured as described above, a high temperature load test was performed according to the method described below, and the continuity of the internal electrode layer was evaluated. In addition, the interface between the ceramic dielectric layer and the internal electrode layer was observed, and it was confirmed that a diffusion region (diffusion layer) was formed in which the Al concentration increased from the internal electrode layer toward the ceramic dielectric layer and decreased after reaching the concentration peak.

(1) High temperature load test

15 samples were taken from each sample and subjected to high temperature load test at 180℃ and 60V. The time required for the insulation resistance to drop by one order of magnitude was set as the failure time of each multilayer ceramic capacitor. Then, the failure time was subjected to Weber plotting to obtain MTTF (mean time to failure). The evaluation results of MTTF are combined in Table 8 and are organized as shown in Figure 6.

(2) Evaluation of the continuity of the internal electrode layer

Each multilayer ceramic capacitor of each sample was cut from the orthogonal plane of the internal electrode layer and observed using a SEM (scanning electron microscope). The observation magnification was 1000 times, and 10 internal electrodes were randomly selected from the observation field of view. The ratio of the electrode portion to the total length was measured, and the continuity was evaluated based on this. Here, the continuity was rated as "◎" for more than 90%, "○" for 80-90%, and "×" for less than 80%, and the results are recorded in Table 8.

1) Mass fraction relative to 100 mass fraction of spherical nickel powder

2) Ratio of MTFF of each sample to MTFF of sample 1C (without Al ₂ O ₃ addition) (MTFF of each sample/MTTF of sample 1C)

As shown in Table 8, compared with the sample without Al ₂ O ₂ (sample number 1C), all samples mixed with Al ₂ O ₃ within the range specified in the present invention (sample numbers 2C to 15C) showed an increase in MTTF.

Furthermore, the continuity of the internal electrode is more than 90% for sample numbers 2C~11C and 80~90% for sample numbers 12C~15C.

On the other hand, the sample in which Al ₂ O ₃ was mixed beyond the range specified in the present invention (sample number 16C) had a lower MTTF than the sample without Al ₂ O ₃ (sample number 1C), and the continuity of the internal electrode was less than 80%.

From the above, it can be seen that in order to improve the high-temperature load life, relative to 100 mass parts of spherical nickel _powder , _Al2O3 is preferably mixed in an amount of 0.10~5.50 mass parts. If it is within the range of 0.10~2.30 mass parts, the high-load life can be further improved without damaging the continuity of the internal electrode.

Claims (7)

A method for forming a diffusion region in a multilayer ceramic capacitor, wherein in the multilayer ceramic capacitor having: a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni alternately stacked; and an external electrode formed on the outer surface of the ceramic multilayer, a diffusion region of at least one element selected from the group consisting of Ta, Nb, Zr, and metal elements in a stabilizer is formed at and near the interface between the adjacent internal electrode layer and the ceramic dielectric layer. The invention comprises at least a step of manufacturing a laminated body of a predetermined number of ceramic green sheets forming the ceramic dielectric layer and an internal electrode paste film forming the internal electrode layer, and performing calcination at 900-1400° C. in a reducing environment; the internal electrode paste film is formed using a Ni paste containing (A) a conductive powder mainly composed of Ni, (B) a binder resin, (C) an organic solvent, and (D) an additive, and the additive (D) is at least one selected from the following group: (D1) an additive containing 0.025-0.80 parts by mass of Ta in terms of Ta ₂ O ₅ relative to 100.0 parts by mass of the conductive powder (A) mainly composed of Ni; (D2) an additive containing 0.010 to 0.50 parts by mass of Nb in terms of _Nb2O5 relative to 100.0 parts by mass of the conductive powder (A) mainly comprising Ni; and (D3) stabilized zirconia (SZ) containing a stabilizer in the range of 8.0 _to 25.0 mol% relative to 100 g of the conductive powder (A) mainly comprising Ni, wherein the zirconia crystal structure is stabilized in the range of 0.05× ^10-2 to 1.40× ^10-2 mol. A method for forming a diffusion region in a multilayer ceramic capacitor as claimed in claim 1, wherein the interface and its vicinity are a region from the interface between the adjacent internal electrode layer and the ceramic dielectric layer, from a region 1/16 of the thickness of the ceramic dielectric layer toward the dielectric layer side, to a region 1/2 of the thickness of the internal electrode layer from the interface toward the internal electrode layer side, and the concentration of at least one element selected from the group consisting of Ta, Nb, Zr, and metal elements in the stabilizer in the diffusion region has a concentration distribution that increases in a direction from the internal electrode layer side toward the ceramic dielectric layer side and decreases after reaching a concentration peak. A method for forming a diffusion region in a multilayer ceramic capacitor as claimed in claim 1 or 2, wherein the metal element in the stabilizer is one or more selected from Y, Ca, Mg and Sc. A multilayer ceramic capacitor, comprising: a ceramic multilayer body, which is a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni interlaced; and an external electrode, which is formed on the outer surface of the ceramic multilayer body; and having: at the interface between the adjacent internal electrode layer and the ceramic dielectric layer and in the vicinity thereof, a diffusion region having at least one element selected from the group consisting of Ta, Nb, Zr, and metal elements in a stabilizer, the diffusion region being a diffusion region formed by the method for forming a diffusion region in a multilayer ceramic capacitor of claim 1, The interface and its vicinity are the region from the interface between the adjacent internal electrode layer and the ceramic dielectric layer, from the region at a distance of 1/16 of the thickness of the ceramic dielectric layer toward the dielectric layer side, to the region at a distance of 1/2 of the thickness of the internal electrode layer from the interface toward the internal electrode layer side. In the diffusion region, the concentration of at least one element selected from the group consisting of the metal elements in the Ta, Nb, Zr, and stabilizer increases in the direction from the internal electrode layer side toward the ceramic dielectric layer side, and decreases after reaching a concentration peak. As in claim 4, the multilayer ceramic capacitor, wherein the metal element in the stabilizer is one or more selected from Y, Ca, Mg and Sc. A Ni paste comprises: (A) a conductive powder mainly composed of Ni, (B) a binder resin, (C) an organic solvent, and (D) an additive; wherein the additive (D) is at least one selected from the following group: (D1) an additive containing 0.025 to 0.80 parts by weight of Ta in terms of _Ta2O5 relative to 100.0 parts by weight of the conductive powder (A) mainly composed of _Ni ; (D2) an additive containing 0.025 to 0.80 parts by weight of Nb2O5 relative to 100.0 parts by weight of the conductive powder ( _A ) mainly composed of Ni; ₅ converted to an additive of Nb in the range of 0.010 to 0.50 parts by mass; and (D3) the crystal structure of the zirconium dioxide is stabilized by using a stabilizer in the range of 8.0 to 25.0 mol %, and the stabilized zirconium dioxide (SZ) is in the range of 0.05×10 ^-2 to 1.40×10 ^-2 mol relative to 100 g of the conductive powder (A) mainly comprising Ni. The Ni paste of claim 6, wherein when the (D3) stabilized zirconium dioxide (SZ) is contained, the stabilizer is at least one selected from Y ₂ O ₃ , CaO, MgO and Sc ₂ O ₃ .