JP2958820B2 - 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 has the 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 dielectric ceramic materials satisfying these conditions, for example, BaTiO ₃ of JP 62-256422 -CaZr
The composition of the O ₃ —MnO—MgO system and Japanese Patent Publication No. 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 Japanese Patent Application Laid-Open No. 62-256422, CaZrO ₃ and C
Since aTiO ₃ easily forms a secondary phase together with Mn and the like, there is a danger that reliability at a high temperature is reduced.

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.

Further, in the non-reducing dielectric ceramic compositions proposed so far, although the insulation resistance at room temperature is high, the resistance tends to decrease significantly at high temperatures. Therefore, these compositions have a drawback that the reliability at high temperatures is poor.

Therefore, a main object of the present invention is to make it possible to sinter the structure without converting it into a semiconductor even under a low oxygen partial pressure, to have a dielectric constant of 3000 or more, and to have an insulation resistance at room temperature of 12. 0 or more, insulation resistance at 125 ° C is l
ogIR is 10.0 or more, and the temperature characteristic of the dielectric constant is −55 ° C. to 125 ° C. based on the capacitance value of 25 ° C.
An object of the present invention is to provide a non-reducing dielectric ceramic composition that satisfies a range of ± 15% over a wide range of ° C.

[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 2.0 mol% of MnO. , MgO
And 0.5 to 5.0 mol%, NiO, as at least one contains a 0.3 to 3.0 mol%, further 100 parts by weight of the components of the _{Al 2 O 3, BaO-SrO} -L
0.5% of oxide glass mainly containing i ₂ O—SiO ₂
It is a non-reducing dielectric ceramic composition containing about 2.5 parts by weight.

[0010]

The non-reducing dielectric porcelain composition according to the present invention can be used in a neutral or reducing atmosphere at a temperature of 1300 to 1300.
Even when firing at a temperature of 1280 ° C., the structure is not reduced to a semiconductor. Further, this non-reducing dielectric ceramic composition shows a high insulation resistance value at room temperature of 12.0 or more in logIR, a small drop in the insulation resistance value even at a high temperature, and a high dielectric constant of 3000 or more. , The capacitance temperature change rate also satisfies the X7R characteristic specified in EIA.

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 objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As starting materials, BaTiO ₃ , rare earth oxide, Co ₂ O ₃ , MnO, NiO, Al ₂ O ₃ , M ₂ having different contents of alkali metal oxides contained as impurities.
gO, 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, an alkali metal oxide content of 0.05% by weight was used. Using BaTiO ₃ , sample No. 34
As for, BaTiO ₃ containing 0.07% by weight of alkali metal oxide was used.

[0014]

[Table 1]

After 5% by weight of a vinyl acetate-based binder was added to the obtained weighed material, the mixture was thoroughly wet-mixed with a ball mill using PSZ balls. Next, after the dispersion medium in this mixture was evaporated and dried, a powder was obtained through a sizing process. The obtained powder was subjected to a pressure of ² ton / cm ² and a diameter of 10 mm,
It was press-molded into a disk having a thickness of 1 mm to obtain a molded body.

Next, the compact obtained in this manner is subjected to binder removal under the condition of being kept in air at 400 ° C. for 3 hours, and then the H ₂ / N ₂ volume ratio is 3/100.
At a temperature shown in Table 2 in a reducing atmosphere gas stream.
Firing for a time resulted in 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 (logIR) of the capacitor at room temperature.
And the rate of temperature change of the capacity (TCC) was 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 500 V for 2 minutes at 125 ° C. and 125 ° C., and the results are shown as log values (logIR). Further, the temperature change rate (TCC) is 25 ° C.
(ΔC ₋₅₅ / C ₂₅ , ΔC ₊₁₂₅ / C ₂₅ ) at −55 ° C. and 125 ° C. based on the capacitance value of
Between 5 ° C. and + 125 ° C., the absolute value of the value at which the capacitance temperature change rate is the maximum, the so-called maximum change rate (| ΔC / C ₂₅
| _Max ).

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 2.0 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 2.0 mol%, as shown in Sample No. 15, the insulation resistance value, particularly the resistance value at high temperatures, is undesirably reduced.

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 numbers 27 and 28, There is no flattening effect, and the temperature tends to deviate to the (-) side at a low temperature side, and the effect of improving the insulation resistance value is also lost. On the other hand, if the addition amount exceeds 5.0 mol%, as shown in Sample No. 32, the dielectric constant ε and the insulation resistance value decrease, which is not preferable.

When the amount of NiO or Al ₂ O ₃ is 0.3
When the addition amount is less than 0.3 mol%, as shown in Sample No. 18, there is no effect on the improvement of the reduction resistance of the structure, and the decrease in the insulation resistance value is not more than 3.0 mol%. At the same time, it has no effect on improving the high-temperature IR value, which is not preferable. When the addition amount exceeds 3.0 mol%, as for MnO, the insulation resistance value of NiO decreases as shown in Sample No. 21, and for Al ₂ O ₃ , Sample Number 22 decreases. As shown in (1), there is a problem that the sinterability decreases, the dielectric constant decreases, and the dielectric loss increases.

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
It is not preferable to set the content to 2.5% by weight, when the addition amount is less than 0.5% by weight, as shown in Sample No. 26, since there is no effect on lowering the sintering temperature and improving the reduction resistance. On the other hand, if the addition amount exceeds 2.5% by weight, as shown in Sample No. 24, the dielectric constant ε decreases, which is not preferable.

Note that the characteristic data shown in Table 2 is data obtained for a single-plate capacitor. However, a multilayer capacitor obtained by forming the same composition into a sheet and processing a chip has almost the same data as the present data. The result is obtained.

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 2.0 mol% of MnO, and 0.5 to 5.0 of MgO. 0 mol%, and at least one of NiO and Al ₂ O ₃ 0.3 to
3.0 mol%, and the above-mentioned component was taken as 100 parts by weight to obtain Ba.
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.