JPH0785460B2 - Multilayer porcelain capacitor - Google Patents

Description

The present invention relates to a laminated porcelain capacitor having nickel internal electrodes.

[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. Such multilayer ceramic capacitors have been rapidly used in a wide variety of electronic circuits due to rapid miniaturization of electronic parts with the recent progress of electronics.

However, this conventional BaTiO ₃ -based dielectric material needs to be fired at a high temperature of 1250 ° C to 1350 ° C. When this material is used as a derivative of a laminated porcelain capacitor, the internal electrodes are Palladium (melting point 1555 ° C), which is an expensive noble metal that does not melt and does not oxidize at the firing temperature of, or its alloy is used, and the number of internal electrodes becomes large especially for those with large capacitance. The cost is high, and the conventional multilayer ceramic capacitor has high capacity efficiency, excellent dielectric properties, and high reliability, but its price is a serious 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 a derivative composed of barium titanate (BaTiO ₃ ) and the base metal internal electrode are co-sintered, 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 should be lower than that, and in this case, the dielectric composed of barium titanate or a solid solution thereof is generally reduced under the oxygen partial pressure and loses its insulating property.
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, for example, Japanese Patent Publication No. 57-42588. It is proposed in the gazette and the like.

This is generally because, in the ABO ₃ type crystal, 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 octahedral (perovskite) structure. It is known that when the amount is excessive, the crystal lattice strongly attracts oxygen atoms and is difficult to be reduced, and the invention described in the above publication is based on the deviation of the stoichiometric ratio, and the non-reducing property of the dielectric material. Is improved. However, the dielectric ceramic composition described in the above publication has a drawback that the rate of change of the dielectric constant with temperature is large and the dielectric properties are deteriorated.

In addition, as a high-dielectric-constant dielectric ceramic composition with a small rate of change in permittivity with temperature, BaTiO ₃ was added to bismuth stannate [Bi ₂
O _{3) 3],} zirconium bismuth [Bi ₂ (ZrO _{3) 3]}
Bismuth compounds such as nickel zirconate (NiZrO ₃ ) and magnesium zirconate (MgZrO ₃ )
Is added. This is because the maximum value of the dielectric constant near the Curie point of BaTiO ₃ is lowered by the strong depressor effect of the bismuth compound or nickel zirconate or magnesium zirconate, and the temperature change rate of the dielectric constant is reduced. However, when a base metal such as nickel is used as an internal electrode and a bismuth-based compound or a dielectric material containing nickel zirconate or magnesium zirconate added to BaTiO ₃ is co-fired below the equilibrium oxygen partial pressure of Ni / NiO, the dielectric Has a drawback that it is reduced and loses its insulating property, and as a result, satisfactory dielectric properties cannot be obtained.

Furthermore, BaTiO ₃ as the Ni / dielectric be calcined near the equilibrium oxygen partial pressure of NiO own non-reducing temperature change rate is small in dielectric constant without being reduced high dielectric constant type dielectric ceramic composition -MnO- MgO
A system composition has been proposed in JP-A-57-71866.

This has the effect that MnO and MgO suppress the reduction of BaTiO ₃ , the derivative is not reduced even when fired near the equilibrium oxygen partial pressure, and has sufficient insulating properties, and MgO is the bismuth compound. Since it has the same depressor effect, the temperature change rate of the dielectric constant is reduced. However, the dielectric porcelain composition described in the above publication has a low dielectric constant itself, and the amount of MgO added is increased to increase the EIA standard (Electrification).
-Ronic Industries Association Standard) Dielectric constant temperature change rate (However, + 25 ° C in the range of -55 ° C to + 125 ° C)
(With reference to) is within ± 15%, the dielectric constant is further reduced to 2200 or less, and practical dielectric properties cannot be obtained.

[Object of the Invention]

The present invention is mainly aimed at solving the above-mentioned problems. Specifically, nickel is used as an internal electrode, and the dielectric constant is high, the electric insulation is excellent, the dielectric loss tangent is small, and the dielectric is spread over a wide temperature range. It is an object of the present invention to provide a laminated porcelain capacitor which has a small rate of temperature change and is extremely economical.

[Means for solving problems]

According to the present invention, with respect to the main component whose composition formula is represented by (1-x-y-z ) BaTiO 3 + xCaZrO 3 + yMnO + zMgO where 0.003 ≦ x ≦ 0.023 0.005 ≦ y ≦ 0.030 0.010 ≦ z ≦ 0.080 as dielectric , Y ₂ O ₃ as an additive above MgO
As shown in Fig. 1, enclosed by points A, B, C, D, E MgO (mol%) Y ₂ O ₃ (mol%) A 8.00 2.00 B 5.00 0.25 C 1.00 0.25 D 1.00 1.00 E 6.00 2.50 The above object can be achieved by using nickel added as an internal electrode within the range and using nickel as an internal electrode in the dielectric.

It should be noted that FIG. 1 shows the dielectric used in the present invention.
FIG. ₂ is a binary system diagram showing the composition range of MgO and Y ₂ O ₃ , where MgO (mol%) is the mole fraction of the whole main component, and Y ₂ O ₃ (mol%) is the total amount of the main component and the additive. It is shown in terms of mole fraction.

FIG. 2 is a sectional view of the laminated ceramic capacitor of the present invention.

As shown in FIG. 2, the multilayer ceramic capacitor according to the present invention has a plurality of internal electrodes 2 made of nickel formed in a dielectric 1. The internal electrodes 2 are alternately connected to the external electrodes 3 formed on both ends.

According to the present invention, as the dielectric, using a dielectric excellent in non-reducing property, particularly as described above, BaTiO ₃ , CaZrO ₃ , MnO, and MgO are added to the main component composed of Y ₂ O as an additive in a specific ratio. _A mixture of ₃ in a specific ratio is used. The dielectric is a rare earth element oxide Y ₂ O ₃ and BaTiO _3, CaZrO _3, MgO, relative to MnO, by simultaneous addition, the bismuth compound or a zirconium nickel and similar depressor effects as zirconium magnesium It is possible to lower the maximum value of the dielectric constant near the Curie point of BaTiO ₃ , reduce the temperature change of the dielectric constant, and effectively improve the insulation resistance.

In addition, when nickel is used as the internal electrode, Ni / NiO
Equilibrium oxygen partial pressure at 1250 ℃ to 1350 ℃ 3 × 10
^{-10 to} 3 × 10 ^-8 atm The donor level electrons formed in the dielectric due to oxygen defects generated when firing in an atmosphere of Mn
By adding O and MgO, they can be recombined at the acceptor level, whereby the dielectric porcelain is prevented from becoming a semiconductor, and high insulation can be maintained.

Therefore, as a porcelain capacitor, a capacitor having a high relative permittivity and insulation resistance, a small dielectric loss tangent (tan δ), and a small variation with respect to temperature changes in the dielectric constant and the capacitance can be obtained.

The manufacture of the porcelain capacitor of the present invention will be described. When manufacturing dielectrics, the starting materials are BaCO ₃ and CaCO.
BaTiO ₃ and CaZrO ₃ are synthesized using powders of ₃ , TiO ₂ and ZrO ₂ . BaTiO ₃ is at a temperature of 1150 ℃ from BaCO ₃ and TiO ₂ ,
CaZrO ₃ is synthesized from CaCO ₃ and ZrO ₂ at a temperature of 1220 ° C. by solid-state reaction. After crushing the synthesized BaTiO ₃ and CaZrO ₃ , MnCO ₃ , MgCO ₃ and Y ₂ O ₃ are added to prepare a slurry. The obtained slurry is formed into a film (sheet) by a known forming means such as a doctor blade method or a calendar roll method.

On this sheet, a nickel paste containing fine nickel powder having an average particle diameter of 1.5 μm or less is printed by printing means, for example, a nickel internal electrode by a screen printing method. afterwards,
A plurality of printed sheets are laminated and fired in a reducing atmosphere. The firing conditions are preferably a firing temperature of 1250 ° C. to 1350 ° C. and an oxygen partial pressure in the atmosphere of 3 × 10 ^{−10 to} 3 × 10 ⁻⁸ atm.

For the final product, apply external electrode forming paste to both ends of the sintered body obtained as described above, and then 700 to 850 ℃
Is obtained by firing in a reducing atmosphere, particularly in an atmosphere with an oxygen partial pressure of 10 ^{−16 to} 10 ⁻¹⁰ atm. Examples of the material of the external electrode include silver, silver-palladium, nickel, copper, copper-nickel and the like. In the present invention, nickel, copper or copper-nickel is preferable from the viewpoint of adhesiveness to the internal electrode.

Incidentally, according to the present manufacturing method, 250 to 500 for the purpose of removing the organic binder before firing after stacking the sheets.
It is desirable to perform the heat treatment in the air at a low temperature of ℃.

The invention is illustrated by the following example.

〔Example〕

(Preparation of sample) Using BaCO ₃ , CaCO ₃ , TiO ₂ , and ZrO ₂ as starting materials, BaTiO ₃ and CaZrO ₃ were synthesized by solid-state reaction at 1150 ° C and 1220 ° C and pulverized. Next, synthesized BaTiO ₃ and CaZrO ₃
On the other hand, MnCO ₃ , MgCO ₃ and Y ₂ O ₃ were respectively weighed as dielectrics so that the proportions shown in Table 1 were obtained, and mixed with a dispersant and a dispersion medium in a ball mill to prepare a raw material slurry.

A plasticizer and an organic binder were added to the obtained slurry, and the mixture was sufficiently stirred and degassed in vacuum, and then formed into a film by the doctor blade method. Electrodes were printed on this sheet by a screen printing method using a predetermined plate, a nickel paste containing nickel fine powder having an average particle size of 0.7 μm, an organic binder and a solvent.

In the same manner, stack 21 sheets with electrodes printed, stack the sheets without electrodes printed on the top and bottom, and stack the cutting guide sheet with carbon paste printed on the grid on top of it, and after thermocompression bonding, vertically Cut to about 3.6 mm, about 1.8 mm wide,
A chip type sample consisting of 20 layers was obtained.

After heat-treating this sample at 300 ° C. for 2 hours, the oxygen partial pressure was controlled to 3 × 10 ^{−10 to} 3 × 10 ⁻⁸ atm with N ₂ as a carrier gas, and the sample was fired at 1250 ° C. to 1350 ° C. for 2 hours. Nickel copper paste is applied to both ends of the obtained sintered body, dried, and then the carrier gas is set to N ₂ and the oxygen partial pressure is controlled to about 1 × 10 ⁻¹⁵ atm, followed by firing at 800 ° C. for 10 hours and external connection. The electrode for baking was baked.

(Sample measurement method) After leaving the obtained sample at room temperature for 48 hours, the frequency of 1.0K
Capacitance and dielectric loss tangent were measured at Hz and input signal level of 1.0 Vrms. Then, apply DC voltage 50V for 1 minute,
The insulation resistance at that time was measured. Also, in the temperature range of -55 ° C to 125 ° C, the capacitance is measured in the same manner as the above method, and the capacitance is -55 ° C, -10 ° C, + 95 ° C for the capacitance of + 25 ° C.
The change rate at ℃ and + 125 ℃ was calculated.

The measurement results are shown in Table 1. The insulation resistance in Table 1 is the product of the capacitance C (μF) and the insulation resistance R (MΩ) C × R
It is expressed by (MΩ · μF).

As is clear from Table 1, MgO having a MgO content of less than 1 mol%
1 has low CR, Y ₂ O ₃ is 0, No. ₂ , 9, 21 has low CR, −
Large temperature change at 55 ℃. In addition, Y ₂ O ₃ at 6 mol% MgO
The same applies to No. 26, which is 0.75 mol%.

On the other hand, No. 6 containing Y ₂ O ₃ at 1.25 mol% and MgO at 1.0 mol% is +95
Large temperature change in ° C. In addition, MgO is 3 mol%, Y ₂ O ₃ 2.0
Sintering was difficult with mol% No. 13 and MgO 5 mol% and Y ₂ O ₃ 2.5 mol%. No.1 with less than 0.5 mol% MnO
CR is low in 6,31, CR is low in Nos. 20 and 35 with MnO exceeding 3.0 mol%, and capacitance is also low in No. 35.

No. 30 with 3 mol% Y ₂ O ₃ has a low capacitance, and MgO is 8.
Even with 5 mol% of No. 38, the capacitance is low and the temperature change at -55 ° C is large.

Further, No. 7 in which CaZrO ₃ is 0 has a low CR and the temperature characteristics at -55 ° C are also poor, and No. 15 in which the content is -2.5 mol% has poor temperature characteristics at + 95 ° C.

In contrast to these comparative examples, all the other samples of the present invention showed excellent characteristics and had a capacitance of 40 μF or more (dielectric constant of 2200).
Equivalent), dielectric loss tangent 2.5% or less, insulation resistance 1000 MΩ or more, and temperature change (-55 ℃ to + 125 ℃) ± 15
% Was achieved.

〔The invention's effect〕

Above, as detailed, according to the present invention, nickel as an internal electrode, BaTiO _3, CaZrO _3, MnO and certain ratio Y ₂ O ₃ with respect to the main component formed by compounding a specific ratio of MgO as a dielectric By adding in, capacitance 40μF or more, insulation resistance 1000
It is possible to obtain a laminated porcelain capacitor having excellent characteristics such as MΩ or more, electrostatic tangent of 2.5% or less, and temperature change (-55 ° C to + 125 ° C) of ± 15% or less, and excellent cost efficiency.

[Brief description of drawings]

FIG. 1 shows MgO and Y ₂ O in the dielectric used in the present invention.
FIG. 2 is a binary system diagram showing the composition range of ₃ , and FIG. 2 is a sectional view of the multilayer ceramic capacitor of the present invention. 1 ... Dielectric 2 ... Internal electrode 3 ... External electrode

Claims (1)

[Claims] To 1. A main component composition formula represented by (1-x-y-z ) BaTiO 3 + xCaZrO 3 + yMnO + zMgO where 0.003 ≦ x ≦ 0.023 0.005 ≦ y ≦ 0.030 0.010 ≦ z ≦ 0.080, with respect to the MgO , Y as an additive
_In FIG. 1, a derivative containing ₂ O ₃ so as to satisfy the composition within the range surrounded by the points A, B, C, D and E below has an internal electrode made of nickel. A laminated porcelain capacitor characterized by the above. MgO (mol%) Y ₂ O ₃ (mol%) A 8.00 2.00 B B 5.00 0.25 C 1.00 0.25 D 1.00 1.00 E 6.00 2.50