JP3087387B2 - Non-reducing dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reducing dielectric porcelain composition, and more particularly to a non-reducing dielectric porcelain used as a dielectric material for a multilayer capacitor using a base metal such as nickel as an internal electrode material. Composition.

[0002]

2. Description of the Related Art A conventional dielectric porcelain material containing BaTiO ₃ as a main component has a property that when fired under a neutral or reducing low oxygen partial pressure, the material is reduced to become a semiconductor. Therefore, as the internal electrode material, a noble metal such as Pd or Pt which does not melt at the temperature at which the dielectric ceramic material sinters and is not oxidized even when fired under a high oxygen partial pressure which does not turn the dielectric ceramic material into a semiconductor. Had to be used. This has greatly hindered the cost reduction of the manufactured multilayer capacitor.

[0003] In order to solve the above problems,
For example, it has been desired to use a base metal such as Ni as a material for an internal electrode. However, if such a base metal is used as a material for an internal electrode and fired under conventional conditions, the electrode material is oxidized and does not function as an electrode. Therefore, in order to use such a base metal as a material for an internal electrode, it does not turn into a semiconductor even when baked in a neutral or reducing atmosphere having a low oxygen partial pressure, and is sufficient as a dielectric material for a capacitor. There has been a need for dielectric porcelain materials having specific resistance and excellent dielectric properties.
As a dielectric porcelain material satisfying these conditions, for example, Japanese Patent Application Laid-Open No. 63-103861, BaTiO ₃ —MnO—
MgO-rare earth oxide composition, JP-B-61-146
No. 11 BaTiO _3- (Mg, Zn, Sr, Ca) O
-B ₂ O ₃ composition -SiO ₂ system have been proposed.

[0004]

However, in the non-reducing dielectric ceramic composition disclosed in JP-A-63-103861, the temperature change rate (TCC) of the insulation resistance and the dielectric constant is a major component. Since it is sensitive to the particle diameter of certain BaTiO ₃ , it is difficult to control to obtain stable characteristics, and it cannot be said that it is practical.

The composition disclosed in JP-B-61-14611 has a dielectric constant of 2,000.
２2800, which is the dielectric constant of a conventional porcelain composition using a noble metal such as Pd.
It was inferior compared to. Therefore, replacing this composition with a conventional material as it is for cost reduction is disadvantageous in terms of increasing the size and the capacity of a capacitor, and there remains a problem.

[0006] Further, the temperature change rate (TCC) of the dielectric constant of this composition is -25 ° C based on the capacitance value of 20 ° C.
± 10% in the temperature range from
At high temperatures exceeding ℃, it greatly exceeds 10%, and E
There is a disadvantage that the X7R characteristics specified in the IA are greatly deviated.

In addition, the non-reducing dielectric ceramic compositions proposed so far, including the above-mentioned composition, generally have poor reliability at high temperatures, and the dielectric properties of a capacitor using Pd as an internal electrode are poor. The MTTF (m
There was a drawback that the "Ean time to failure" was short.

Therefore, a main object of the present invention is that even under a low oxygen partial pressure, the structure does not become a semiconductor and can be fired, the dielectric constant is 3000 or more, and the insulation resistance is a product of the capacitance ( CR product), and the dielectric constant has a temperature characteristic of ± 15% over a wide range of −55 ° C. to 125 ° C. based on a capacitance value of 25 ° C.
When the electric field strength of 10.0 kV / mm is applied at 150 ° C. with super-acceleration at 150 ° C.
An object of the present invention is to provide a non-reducing dielectric ceramic composition having a TF of 500 hours or more.

[0009]

According to the present invention, BaTiO ₃ containing 0.04% by weight or less of alkali metal oxides contained as impurities, Tb ₂ O ₃ , Dy ₂ O ₃ , H
The mixing ratio of at least one rare earth oxide (Re ₂ O ₃ ) selected from o ₂ O ₃ and Er ₂ O ₃ to Co ₂ O ₃ is 92.0 to 99.4 mol% of BaTiO _3. When,
0.3 to 4.0 mol% of Re ₂ O ₃ and Co ₂ O ₃
With respect to 100 mol% of the main component in the range of 0.3 to 4.0 mol%, as subcomponents, 0.2 to 4.0 mol% of BaO and 0.2 to 3.0 mol% of MnO. , MgO
And 0.5 to 5.0 mol%, CaZrO ₃ 0.5~3.
5 contains a mole%, further 100 parts by weight of the components, containing 0.5 to 2.5 parts by weight of oxide glass mainly composed of _{BaO-SrO-Li 2 O-} SiO 2, the non-reducing It is a conductive dielectric ceramic composition.

[0010]

The non-reducing dielectric porcelain composition according to the present invention can be used in a neutral or reducing atmosphere in the range of 1260 to 1600.
Even if it is fired at a temperature of 1300 ° C., the structure is not reduced to be a semiconductor. Further, the non-reducing dielectric ceramic composition has a high dielectric constant of 3000 or more when the insulation resistance is expressed as a product of the capacitance and a capacitance (CR product), and also has a capacitance temperature change rate. It satisfies the X7R characteristics specified in EIA,
The MTTF when applying an electric field strength of 0.0 kV / mm is 500 hours or more.

Therefore, when the non-reducing dielectric ceramic composition according to the present invention is used as a dielectric material of a multilayer ceramic capacitor, a base metal material represented by Ni or the like can be used as an internal electrode material. Therefore, it is possible to significantly reduce the cost without deteriorating the characteristics as compared with the conventional one using a noble metal such as Pd.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments.

[0013]

EXAMPLES As starting materials, BaTiO ₃ , rare earth oxides, BaCO ₃ , MnO, MgO, CaZrO ₃ , having different contents of alkali metal oxides contained as impurities.
An oxide glass was prepared. These raw materials were weighed so as to have a composition ratio shown in Table 1 to obtain a weighed material. For sample numbers 1 to 32, BaTiO ₃ having an alkali metal oxide content of 0.03% by weight was used. For sample number 33, the alkali metal oxide content was 0.0%.
5 Using the wt% of BaTiO _3, for sample No. 34, the content of alkali metal oxides were used BaTiO ₃ of 0.07% by weight.

[0014]

[Table 1]

The obtained weighed material is dispersed together with a dispersion medium in PSZ.
The mixture was mixed by a ball mill using balls to obtain a raw material slurry. Next, an organic binder and a plasticizer were added to the slurry, and the mixture was sufficiently stirred, and then formed into a sheet by a doctor blade method to obtain a ceramic green sheet.

Next, a conductive paste for forming an internal electrode is printed on one surface of the ceramic green sheet thus obtained, dried, and a plurality of ceramic green sheets are laminated. I got a body. After delamination of the laminated body at 320 ° C. for 5 hours, the volume ratio of H ₂ / N ₂ was 3/1.
In a reducing atmosphere gas stream of No. 00, calcination was performed for 2 hours at a temperature shown in Table 2 to obtain a porcelain.

[0017]

[Table 2]

A silver paste was applied to both sides of the obtained porcelain and baked to form silver electrodes to form capacitors. Then, the dielectric constant ε, dielectric loss tan δ, insulation resistance value (logI
R), the temperature change rate of the capacity (TCC) and the MTTF were measured. Table 2 shows the results.

The dielectric constant ε and dielectric loss tan δ were measured at a temperature of 25 ° C., a frequency of 1 kHz, and an AC voltage of 1 V. In addition, the insulation resistance value was measured at a temperature of 25.
The measurement was performed by applying a DC voltage of 25 V at 2 ° C. for 2 minutes, and the result is shown as a product (CR product) with the capacitance value. further,
Regarding the temperature change rate (TCC), the change rate (ΔC at −55 ° C. and 125 ° C. based on the capacitance value at 25 ° C.)
_-55 / C ₂₅ , ΔC ₊₁₂₅ / C ₂₅ ) and -55 ° C to +12
The absolute value of the value at which the capacitance temperature change rate is maximum between 5 ° C., that is, the so-called maximum change rate (| ΔC / C ₂₅ | _max ) is shown. For MTTF, the number of samples n = 18
The electric field strength at 150 ° C. was 10.0 kV / mm.
It was calculated from the time up to the dielectric breakdown when the voltage was applied.

As apparent from Table 2, the non-reducing dielectric ceramic composition according to the present invention exhibits excellent characteristics.

The reasons for limiting the ranges of the main component and the subcomponent in the present invention as described above are as follows.

First, the reason for limiting the range of the main component will be described.

The composition ratio of BaTiO _{3 as} the main component is 9
The content of 2.0 to 99.4 mol% is determined when the composition ratio is 92.0 mol%.
If less than 0 mol%, rare earth elements and Co ₂ O ₃
Is increased, as shown in sample number 4,
Undesirably, the insulation resistance value and the dielectric constant decrease. When the composition ratio of BaTiO ₃ exceeds 99.4 mol%, the effect of the addition of the rare earth element and Co ₂ O ₃ has no effect, and as shown in Sample No. 3, the capacity of the high-temperature portion (near the Curie point) The rate of temperature change is large and shifts to the (+) side, which is not preferable. Further, the reason why the content of the alkali metal oxide in BaTiO ₃ is set to 0.04% or less is that if the content exceeds 0.04%, as shown in Sample Nos. 33 and 34, the dielectric constant decreases, and Is not preferred.

Next, the reasons for limiting the range of the subcomponent will be described.

The reason why the amount of BaO is set to 0.2 to 4.0 mol% is that when the amount of addition is less than 0.2 mol%, as shown in Sample No. 9, the structure of the semiconductor during firing in the atmosphere is changed to a semiconductor. And
It is not preferable because the insulation resistance value is remarkably reduced. On the other hand, if the addition amount exceeds 4.0 mol%, as shown in Sample No. 12, the sinterability decreases, which is not preferable.

The reason why the addition amount of MnO is 0.2 to 3.0 mol% is that when the addition amount is less than 0.2 mol%,
As shown in Sample No. 17, the effect of improving the reduction resistance of the structure is lost and the insulation resistance value is remarkably reduced, which is not preferable. On the other hand, if the addition amount exceeds 3.0 mol%, as shown in Sample No. 15, the insulation resistance value decreases, which is not preferable.

The reason why the addition amount of MgO is 0.5 to 5.0 mol% is that when the addition amount is less than 0.5 mol%, as shown in Sample Nos. 22 and 23, The curve showing the rate of change tends to have a single peak, and tends to deviate to the (-) side in a low temperature part, and to the (+) side in a high temperature part (near the Curie point), and also has the effect of improving the insulation resistance value. It is not preferable because it disappears. On the other hand, if the addition amount exceeds 5.0 mol%, as shown in Sample No. 26, the dielectric constant ε and the insulation resistance value decrease, which is not preferable.

The reason why the amount of CaZrO ₃ added is 0.5 to 3.5 mol% is that when the addition amount is less than 0.5 mol%,
As shown in sample numbers 31 and 32, there is no effect on the improvement of the MTTF value, which is not preferable. When the amount of addition exceeds 3.5 mol%, as shown in Sample No. 29, the rate of change in capacitance at high temperature (near the Curie point) tends to deviate to the (-) side, and the dielectric constant increases. This is not preferable because the rate ε decreases.

Finally, BaO—SrO—Li ₂ O—Si
The amount of addition of the oxide glass containing O ₂ as a main component is 0.5 to
The reason for setting the content to 2.5% by weight is that if the amount added is less than 0.5% by weight, as shown in Sample No. 21, the effect of lowering the sintering temperature and the effect of improving the reduction resistance are lost. Not preferred. On the other hand, if the addition amount exceeds 2.5% by weight, as shown in Sample No. 19, the dielectric constant ε decreases, which is not preferable.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-70221 (JP, A) JP-A-5-17212 (JP, A) JP-A-5-9066 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C04B 35/42-35/49 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. BaTiO ₃ having an alkali metal oxide content of 0.04% by weight or less as an impurity,
b ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ at least one rare earth oxide (Re ₂ O 3)
₃ ) and Co ₂ O ₃ in a proportion of 92.0 to 99.4 mol% of BaTiO _3, 0.3 to 4.0 mol% of Re ₂ O ₃ , and 0.3 to 4 of Co ₂ O ₃ With respect to 100 mol% of the main component in the range of 0.0 mol%, as subcomponents, 0.2 to 4.0 mol% of BaO, 0.2 to 3.0 mol% of MnO, and 0.5 to 5.0 of MgO. 0 mol%, and 0.5 to 3.5 mol% of CaZrO _3.
O-SrO-Li a ₂ O-SiO ₂ oxide glass mainly containing 0.5 to 2.5 parts by weight, non-reducible dielectric ceramic composition.