JPH0646618B2 - Multilayer porcelain capacitor and method of manufacturing the same - Google Patents

Description

The present invention relates to a laminated porcelain capacitor having internal electrodes made of nickel and a method for manufacturing the same.

[Conventional technology]

Conventionally, generally, a laminated porcelain capacitor is formed by laminating a plurality of sheet-like dielectrics containing BaTiO ₃ as a main component with internal electrodes coated on the surface and alternately connecting the internal electrodes of each sheet in parallel for a pair of external connections. It is formed by connecting to an electrode and integrally sintering it. With the progress of electronics in recent years, miniaturization of electronic parts has rapidly progressed in such a multilayer ceramic capacitor, and it has come to be used in a wide variety of electronic circuits.

However, this conventional high-dielectric-constant dielectric material whose main component is BaTiO ₃ must be fired at a high temperature of 1250 ° C to 1350 ° C, and when this material is used as the dielectric of a laminated porcelain capacitor, The electrode uses palladium (melting point 1555 ° C) or its alloy, which is an expensive noble metal that does not melt at the firing temperature of the dielectric and does not oxidize. The number of internal electrodes is especially large if the capacitance is large. However, there is a drawback that the cost becomes large and the cost becomes high. Therefore, the conventional multilayer ceramic capacitor has high capacity efficiency, excellent dielectric properties, and high reliability, but its price is a major obstacle to its progress.

Therefore, it has been attempted to use an inexpensive base metal, such as nickel, as the internal electrodes in order to solve the disadvantage that the conventional multilayer ceramic capacitor is expensive. However, when a base metal such as nickel is used as an internal electrode, when the dielectric composed of barium titanate (BaTiO ₃ ) and the base metal internal electrode are simultaneously fired, the base metal is not oxidized and is sintered as a metal film. Since the equilibrium oxygen partial pressure of Ni / NiO is about 3 × 10 ⁻⁷ atm at 1300 ° C., the oxygen partial pressure must be lower than that. In this case, the dielectric substance made of barium titanate or its solid solution is Generally, it is reduced under the above-mentioned oxygen partial pressure and does not lose its insulating property (titanium (Ti) is excessive in barium titanate or its solid solution, and itself serves as a donor, that is, an n-type semiconductor, that is, a metal ion excess type semiconductor. As a result, there is a drawback that practical dielectric characteristics as a laminated ceramic capacitor cannot be obtained.

On the other hand, as a non-reducing dielectric ceramic composition that can be used as a laminated ceramic capacitor having internal electrodes such as nickel, barium titanate solid solution (Ba, Ca, Sr) TiO ₃ is a basic oxide (Ba, A non-reducing dielectric porcelain composition in which Ca, Sr) O is used in excess of the stoichiometric ratio with respect to TiO ₂ which is an acidic oxide and a base metal such as nickel can be used as an internal electrode is disclosed in Japanese Patent Publication No. 57-42588. It is proposed in the gazette and the like.

This is generally because in ABO ₃ type crystals, the A ion having 12 coordination with oxygen larger than the B ion is more stoichiometric than the B ion located at the center of the oxygen hahedron (perovskite) structure. It is known that when the amount is excessive, the crystal lattice strongly attracts oxygen atoms and is difficult to be reduced. The invention described in the above publication is based on this deviation of the stoichiometric ratio, and the specific reducibility of the dielectric substance. Is improved. However, in barium titanate or its solid solution, in the atomic ratio of barium (Ba) and titanium (Ti), if Ba / Ti> 1, the Curie temperature tends to be on the low temperature side due to the dielectric properties of the crystal of the stoichiometric composition. With the transition
The relative dielectric constant at the Curie temperature decreases. Therefore, in a composition with an excess of Ba with respect to the stoichiometric composition, a composition that dissolves in BaTiO ₃ and shifts the Curie temperature to a low temperature, for example, a so-called shifter such as BaZrO ₃ is used so that the Curie temperature is close to room temperature. In the case of BaTiO ₃ solid solution, the relative dielectric constant is lower than that in the stoichiometric composition,
As a result, the relative permittivity is reduced to about 8,000, and the dielectric characteristics of the laminated ceramic capacitor are deteriorated.

[Object of the Invention]

The present invention has been devised in view of the above-mentioned drawbacks, and its purpose is
In the solid solution of BaTiO ₃ , BaZrO ₃ and (Ca, Sr) ZrO ₃ ,
When the A / B ratio of the crystal lattice having the ABO ₃ structure is set to 1, Y ₂ O ₃ , M
By adding appropriate amounts of nO, Al ₂ O ₃ and NiO, 1300
Even if fired in an atmosphere with an oxygen partial pressure of 3 to 8 × 10 ^-9 atm at ℃ to 1340 ℃, it does not reduce, and powder of base metal powder such as nickel does not oxidize and sinters as a metal and has high insulation. It is an object of the present invention to provide a high-dielectric-constant type multilayer ceramic capacitor which has high properties and a high relative dielectric constant and is extremely economical.

[Means for solving problems]

The composition formula of the multilayer ceramic capacitor of the present invention is (1-xy) BaTiO ₃ + xBaZrO ₃ + y (Ca _1-a Sra) ZrO ₃ provided that 0 ≦ x ≦ 0.16 0.01 ≦ y ≦ 0.10 0 ≦ a ≦ 1 For main components, Y ₂ O ₃ , MnO, Al ₂ O ₃ and NiO
In the dielectric material that is added in the range shown below,
It is characterized by having internal electrodes made of nickel.

0.2 wt% <Y ₂ O ₃ <1.0 wt% 0.06 wt% <MnO <0.6 wt% 0.6 wt% <Al ₂ O ₃ <1.0 wt% 0.1 wt% <NiO <1.0 wt% By adding an oxide of a transition metal, the donor electron formed by the reduction of the BaTiO ₃ solid solution crystal is neutralized by the hole formed by the reduction of the transition metal oxide, and as a result, the formation of a crystalline semiconductor is suppressed. It is based on a technical idea.

In the multilayer ceramic capacitor of the present invention, MnO added to BaTiO ₃ which is the main component of the dielectric has an action of suppressing the reduction of BaTiO ₃ , and the dielectric has sufficient insulation even if fired in a reducing atmosphere. Have sex. However, the amount of MnO added to make the dielectric insulating should be 2 mol% or more,
In that case, the relative permittivity at the Curie temperature is significantly reduced. Therefore, in order to prevent the relative permittivity from decreasing,
It is also important to add O. This should be a solid solution with zirconate to minimize MnO
Of increasing the hole concentration by addition with NiO 2
Due to the points. At this time, NiO has an oxygen partial pressure of 3 to 8 x 10
^{At -9} atm, unlike MnO, it is important not to lower the relative permittivity of BaTiO ₃ .

In addition, Al ₂ O ₃ has the effect of forming a liquid phase in BaTiO ₃ in which zirconate is solid-solved, promoting the movement of the crystal lattice, improving the sinterability, and improving the relative dielectric constant. However, if the crystal grain growth becomes excessive, the relative dielectric constant increases, but the dielectric loss increases and the dielectric breakdown strength decreases, so
In addition to the addition of Al ₂ O ₃ , it is important to add a metal oxide that suppresses grain growth. As this metal oxide, Y ₂ O ₃ which has a strong bond with oxygen is used.

The reason for limiting the composition range of the dielectric in the multilayer ceramic capacitor of the present invention is 0.16 <x, 0.10 <y, Y ₂ O ₃
This is because when ≦ 0.2 wt%, 0.6 wt% ≦ MnO, and Al ₂ O ₃ ≦ 0.1 wt% or 1.0 wt% ≦ Al ₂ O ₃ , the dielectric constant of the dielectric is small and not practical.

Further, when y <0.01, Y ₂ O ₃ ≧ 0.1% by weight, MnO ≦ 0.1% by weight, and NiO ≦ 0.1% by weight, the dielectric resistance of the dielectric is small and unsuitable as a capacitor material.
Further, in the composition formula, (Ca _1-α , Srα) ZrO ₃ is 0 ≦ α ≦
In the range of 1, not all solid solution, but actually (1-α) CaZrO ₃ + α
Although it is SrZrO ₃ , it was described as above for convenience.

〔Example〕

Next, the present invention will be described based on examples. As a starting material
BaCO ₃ , CaCO ₃ , SrCO ₃ , TiO ₂ and ZrO ₂ undergo solid phase reaction at 1200 ℃, 1210 ℃ and 1220 ℃, and BaTiO ₃ , BaZrO ₃ and (Ca
_1-α Srα) CO ₃ was synthesized and finely ground.
Next, the synthetic fine powders BaTiO ₃ , BaTiO ₃ , (Ca _1-α , Srα) CO ₃ and
Y ₂ O ₃ , MnCO ₃ , Al ₂ O ₃ and NiO were weighed so as to have the proportions shown in Table 1, and mixed with a dispersant and a dispersion medium in a ball mill to prepare a raw material slurry. Then, an organic binder was added to this raw material slurry together with a plasticizer, and the mixture was thoroughly stirred and degassed under vacuum, and then formed into a film by the doctor blade method. Then about 130 mm in height and about 1 in width
On a sheet cut into 00 mm, an electrode was printed by a screen printing method using a predetermined plate, a nickel paste composed of nickel fine powder having an average particle size of 0.7 μm, an organic binder and a solvent. And the sheet with electrodes printed
After stacking 21 sheets, stacking 4 sheets on top and bottom of which no electrodes are printed, then stacking 1 sheet of cutting guide sheet on which carbon paste is printed in a grid pattern,
Along with thermocompression bonding with a hot press, the sample was cut into a length of about 7.9 mm and a width of about 6.5 mm according to a grid-like guide to obtain a chip-type multilayer ceramic capacitor sample consisting of 20 layers. After heat-treating this sample at 300 ° C. for 2 hours in the air, the oxygen partial pressure is controlled to 3 to 8 × 10 ⁻⁹ atm and the carrier gas is N ₂
The gas was fired at 1300 ° C to 1340 ° C for 2 hours. Finally, apply nickel / copper paste to the end surface of the fired body obtained, heat-treat it at 300 ° C for 2 hours in the atmosphere, control the oxygen partial pressure to about 5 × 10 ^-8 atm, and use carrier gas. The electrode for external connection was baked in an atmosphere of N ₂ gas.

Then, after leaving these evaluation samples for 48 hours at room temperature, measure the capacitance and dielectric loss at a frequency of 100 KHz and an input signal level of 1.0 Vrms, then apply DC 50 V for 1 minute and measure the insulation resistance at that time. did.

The above results are shown in Table 1.

[Effects of the Invention] As is clear from Table 1, the multilayer ceramic capacitor according to the present invention has a large capacitance and an insulation resistance of 5800 MΩ · μ.
It is excellent as F or more, and has good dielectric loss tangent and electrostatic capacitance temperature characteristics, and achieves the purpose of small size and large capacity.

It is also understood that in the laminated porcelain capacitor using nickel as the internal electrode, the dielectric porcelain can be sintered at the same time as the nickel metal electrode and satisfies all the dielectric characteristics of the sintered porcelain.

Claims (2)

[Claims] 1. A main component represented by the composition formula: (1-xy) BaTiO ₃ + xBaZrO ₃ + y (Ca _1-α Srα) ZrO ₃ where 0 ≦ x ≦ 0.16 0.01 ≦ y ≦ 0.10 0 ≦ a ≦ 1 In contrast, Y ₂ O ₃ , MnO, Al ₂ O ₃ and NiO
A multilayer ceramic capacitor having internal electrodes made of nickel in a dielectric formed by adding each of the following in the following range. 0.2 wt% <Y ₂ O ₃ <1.0 wt% 0.06 wt% <MnO <0.6 wt% 0.1 wt% <Al ₂ O ₃ <1.0 wt% 0.1 wt% <NiO <1.0 wt% 2. BaTiO ₃ , BaZrO ₃ and (Ca _1- α.Srα) CO ₃ powder synthesized by solid-state reaction using BaCO ₃ , CaCO ₃ , SrCO ₃ , TiO ₂ and ZrO ₂ as starting materials, and Y ₂ O ₃ ,, MnCO ₃ ,, Al ₂ O ₃ and Ni
O was added, and then this was molded into a sheet shape, and an electrode was printed on the upper surface with nickel paste, and then a plurality of the sheets were laminated, and the oxygen partial pressure was 3 to 8 × 1.
A method of manufacturing a multilayer ceramic capacitor, which comprises firing in a reducing atmosphere of 0 ^-9 atm.