JP2693249B2 - Low loss porcelain capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a low loss ceramic capacitor, and particularly to a high dielectric constant, an excellent dielectric constant temperature characteristic, a low loss, and frequency dependence and voltage dependence. The present invention relates to a porcelain capacitor which is small in size and has high reliability.

[Conventional technology]

In recent years, switching power supplies have become smaller and lighter, have higher frequencies, or
Along with the high definition of CRT displays, it is required that the dielectric loss (tan δ) of the ceramic capacitor is small and the self-heating of the dielectric ceramic itself is also small.

Conventionally, BaTi has been used as a high dielectric constant porcelain dielectric composition.
O ₃ -based porcelain compositions have been widely put into practical use, but this type has a large dielectric loss, and particularly at high frequencies, the dielectric loss becomes significantly large.

To address these issues, SrTiO ₃ −PbTiO ₃ −Bi
₂ O ₃ —TiO ₂ —MgTiO ₃ based porcelain compositions have been proposed.

Recently, inexpensive copper or nickel has come to be used as an electrode material of a porcelain capacitor instead of silver which has been widely used conventionally. Among them, copper is considered to be a promising electrode material because it has no electro-migration, which is a drawback of silver electrodes, has high reliability, and can be formed at a relatively low cost.

[Problems to be solved by the invention]

However, the formation of the copper electrode requires baking in a neutral or reducing atmosphere in order to prevent its oxidation. Conventionally, however, in the above-mentioned porcelain dielectric composition, the porcelain dielectric composition itself is reduced. Easy to be reduced by sexual atmosphere,
The desired properties could not be obtained.

Therefore, an object of the present invention is to solve the above problems, excellent reduction resistance, high dielectric constant and small rate of change in dielectric constant temperature characteristics, and small dielectric loss causing self-heating,
A porcelain capacitor having a copper electrode is provided.

[Means for solving the problem]

In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive studies and found that a desired low-loss ceramic capacitor can be provided by adding a composite additive of MnO, CoO, and CeO _{2 to} the above-mentioned ceramic composition system. It was

That is, 30.0 to 70.0% by weight of SrTiO ₃ and 0.0 to 40 of PbTiO ₃ .
0 wt%, Bi ₂ O ₃ 8.0 to 40.0 wt%, TiO ₂ 3.0 to 20.0 wt%, MgO 1.0 to 10.0 wt% to 100 parts of the composition,
0.05 to 1.0 wt% of MnO, CoO and CeO ₂ as additives
Add 0.05 to 3.0% by weight.

This makes it possible to obtain a low-loss porcelain dielectric composition with excellent reduction resistance and good temperature characteristics. By baking a copper electrode on this facing surface, a high dielectric constant, low dielectric constant temperature characteristics, and self-heating It is possible to manufacture a highly reliable porcelain capacitor with a small dielectric loss that causes the above.

〔Example〕

 The present invention will be described in detail based on examples.

After sintering SrCO ₃ , TiO ₂ , PbO, Bi ₂ O ₃ , MgCO ₃ and additives as raw materials, weighed and blended so as to have the composition ratio shown in Table 1,
Wet mix in pot mill. Then dehydrated, 900-100
Pre-baking at 0 ° C.

Next, this is crushed, an organic binder is added and granulated, and then pressure molding is performed to a diameter of 16 mm and a thickness of 0.6 mm. This molded product is fired in the air atmosphere at a temperature of 1160 to 1260 ° C. for 2 hours. Copper electrodes are baked on both sides of the thus obtained porcelain sintered body to prepare a capacitor, which is used as a measurement sample.

After that, the dielectric constant ε _s and the dielectric loss ta of each sample are
The characteristic values of nδ (%) (measurement frequency 1 KHz, 100 KHz), dielectric constant temperature characteristic change rate ΔC / C (%), and insulation resistance at 125 ° C were measured and shown in Table 1.

In Table 1, sample numbers marked with * are 1, 2, 3,
4, 6, 7, 8, 9, 13, 14, 15, 19, 21, 23, 24, 2
7, 28 and 30 are outside the scope of the present invention. The measurement conditions for the measured values shown in Table 1 are as follows.

Dielectric constant (ε _s ): Room temperature 1KHz Dielectric loss (tan δ): Room temperature 1KHz, 100KHz Dielectric constant temperature characteristic change rate (ΔC / C): Based on the dielectric constant of 20 ℃, within the range of -25 ℃ and + 85 ℃ Rate of change Insulation resistance: 125 ° C., 500 V, 1 minute value As is clear from Table 1, the samples within the scope of the present invention have a high dielectric constant and a good rate of change in dielectric constant temperature characteristics.
Furthermore, the dielectric loss at 1KHz and 100KHz is small, and the insulation resistance at high temperature is high.

The reason why the respective component ranges are limited as described above in the present invention is as follows.

In the main component, when SrTiO ₃ is less than 30.0% by weight, the dielectric loss at 1 KHz and the rate of change in the dielectric constant temperature characteristics are large (see sample No. 14 in Table 1), and when it exceeds 70.0% by weight, the dielectric constant becomes 1000. It becomes smaller as follows (for example, see No. 23 above).

Although PbTiO ₃ has a dielectric constant of 1000 or more even at 0.0% by weight (for example, refer to No. 7 above), when it exceeds 40.0% by weight, the dielectric loss and the rate of change in the dielectric constant temperature characteristics become large at 1 KHz (for example, No. 7 above). See 3).

When Bi ₂ O ₃ exceeds 40.0% by weight, the dielectric constant becomes 1000 or less (for example, refer to No. 13 above), and when it is less than 8.0% by weight, the rate of change in dielectric constant temperature characteristics becomes large (for example, refer to No. 8 above).

When TiO ₂ is less than 3.0% by weight, 1 KHz dielectric loss becomes large (see, for example, No. 2 above), and when it exceeds 20.0% by weight, the rate of change in dielectric constant temperature characteristics becomes large (for example, No. 15 above).
reference).

When MgO is less than 1.0% by weight, it is hard to be burnt and has a low dielectric constant of 1000 or less (see, for example, No. 9).

Further, the additive MnO is 1.
When it exceeds 0% by weight, the dielectric constant becomes as low as 1000 or less (for example, see No. 21 above), and when it is less than 0.05% by weight, the rate of change in dielectric constant temperature characteristics becomes large (for example, see Nos. 1 and 19).

CoO and CeO ₂ are each 0.05% with respect to 100 parts of the main composition component.
If it is less than 10% by weight, the effect of the addition that the composition itself is less likely to be reduced in a reducing atmosphere is lost, and the insulation resistance at 125 ° C. becomes low (for example, see Nos. 1, 4, 24 and 26 above),
If it exceeds 3.0% by weight, the effect on the reducing atmosphere does not change, but the dielectric constant decreases (for example, see No. 30 above).

It is clear from the following that the addition of MnO, CoO or CeO ₂ as an additive makes the porcelain dielectric composition less susceptible to the influence in the reducing atmosphere during baking of the copper electrode.

That is, FIG. 3 shows the results of reduction experiments by temperature in a nitrogen atmosphere. According to FIG. 3, without the above-mentioned additive, the porcelain dielectric composition is easily reduced, and the insulation resistance at high temperature is significantly reduced (see sample No. 1).

The combined addition of CoO and CeO ₂ makes the porcelain dielectric composition difficult to reduce (see Sample No. 19), and the addition of MnO further deteriorates the insulation resistance at high temperature in a reducing atmosphere. Improve (see Sample No. 25). This is 1 in Table 1
As is clear from the insulation resistance at 25 ° C, it is shown that the combined addition of MnO, CoO, and CeO ₂ improves the insulation resistance at high temperatures (see Sample No. 1, 19, 25). It shows that the body composition itself has a uniform and high insulating force and is excellent in reliability.

Fig. 1 shows the relationship between the amount of added MnO, the dielectric constant and the rate of change in the dielectric constant temperature characteristics when MnO was added and mixed. Sample No. 19 (0.0% by weight of MnO) and No. 1 in Table 1 are shown. 25 (MnO 0.2 wt%), No. 20 (MnO 0.5 wt%), No. 21 (MnO 1.5 wt%) are shown. The reason for limiting the amount of MnO added is clear from this as well.

That is, if it is less than 0.05% by weight, the rate of change in the dielectric constant-temperature characteristic rapidly increases, and if it exceeds 1.0% by weight, the permittivity decreases to 1000 or less.

Further, FIG. 2 shows the relationship between the amount of added MnO, the frequency and the dielectric loss, and the effect of the addition of MnO on the dielectric loss is clear from this.

Table 2 compares the characteristics of the silver electrode product provided with the silver electrode and the copper electrode product provided with the copper electrode of the present invention using the porcelain dielectric composition having the composition of sample No. 25 in Table 1. is there.

Self-heating temperature of the capacitor is applied voltage 2000V, f = 68K
In Hz, it is the self-heating temperature when the surface temperature of the product is the ambient temperature.

The number of failures in the moisture resistance load test is the number of failures by 4000 hours when 30 samples were tested at a temperature of 60 ° C and a humidity of 90 to 95% and an applied voltage of 1500V.

As is clear from Table 2, the baked silver electrode showed significant improvements in characteristics such as the rate of change in dielectric constant-temperature characteristics, self-heating temperature, and reliability, as compared with conventional products.

FIG. 4 shows that the composition of sample No. 25 in Table 1 which is the range of the porcelain dielectric composition of the present invention is provided with a silver electrode and a copper electrode, and an AC voltage of 60 Hz is applied to the composition. It shows the relationship between the AC voltage value and the dielectric loss at that time. As a result, the copper electrode has a smaller voltage dependency, and the merit of the copper electrode product is clear from this.

In the above examples, the power generation charges are SrTiO ₃ ,
Each component may be prepared in advance and blended, such as PbTiO ₃ , MgTiO ₃ , Bi ₂ O ₃ , and nTiO ₂ , or PbO or Pb
₃ O ₄ , CoO is Co ₃ O ₄ , MnO is MnCO ₃ , MgO is MgCO ₃ or other compounds, and similar properties can be obtained as long as they have the above composition after sintering.

〔The invention's effect〕

The present _{invention, SrTiO 3 -PbTiO 3 -MgTiO 3 -Bi} 2 O 3 -T
New additions to the iO ₂ -based porcelain dielectric composition include MnO and Co
By mixing O and CeO ₂ , the porcelain dielectric composition is not reduced even in the reducing atmosphere during baking of the copper electrode, and the copper electrode further increases the permittivity-temperature characteristic change rate at a high dielectric constant. It is possible to obtain a highly reliable porcelain capacitor having improved dielectric loss and reduced dielectric loss at high frequencies and voltage dependency of the dielectric loss.

[Brief description of the drawings]

Fig. 1 is a diagram showing the relationship between the amount of MnO added and the dielectric constant and the change rate of the dielectric constant temperature characteristics of sample Nos. 19, 20, 21, and 25 in Table 1, and Fig. 2 is the sample Nos. 19 and 20 in Table 1. , 21 and 25 relationship diagram of frequency characteristics of MnO addition amount and dielectric loss, Fig. 3 is insulation resistance characteristic diagram of sample No. 1, 19 and 25 in Table 1 in nitrogen atmosphere, and Fig. 4 is It is a voltage characteristic view of the dielectric loss of the sample which baked and formed the silver electrode and the copper electrode with respect to the composition of sample No. 25 of Table 1.

Front page continuation (72) Inventor Shinobu Fujiwara 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Tetsuji Maruno 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (56) References JP-A-2-123720 (JP, A) JP-A-2-222127 (JP, A) JP-A-60-189107 (JP, A)

Claims (1)

(57) [Claims] 1. SrTiO ₃ 30.0 to 70.0% by weight PbTiO ₃ 0.0 to 40.0% by weight Bi ₂ O ₃ 8.0 to 40.0% by weight TiO ₂ 3.0 to 20.0% by weight MgO 1.0 to 10.0% by weight Added to 100 parts by weight of the above composition. MnO 0.05-1.0% by weight, CoO, CeO ₂ 0.05-3.0% by weight, respectively, and mixed on the opposing surfaces of the porcelain composition, a low loss porcelain capacitor characterized by forming a baking electrode mainly composed of copper. .