JP2890865B2 - Dielectric ceramic composition for temperature compensation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating dielectric porcelain composition, and more particularly to a temperature compensating dielectric porcelain composition used, for example, as a dielectric porcelain for a multilayer capacitor.

[0002]

2. Description of the Related Art Conventionally, as this kind of dielectric ceramic composition for temperature compensation, a MgTiO ₃ —CaTiO ₃ series ceramic composition has been used.

[0003]

However, MgT
iO ₃ In -CaTiO ₃ based ceramic composition, as high as the sintering temperature is 1300 ° C. or higher, further, a problem that the semiconductive ceramic is reduced when fired at low oxygen partial pressure neutral or reducing Had a point.

Therefore, a metal which does not melt at a temperature at which the dielectric ceramic material sinters and which is not oxidized even when fired under a high oxygen partial pressure at which the dielectric ceramic material does not turn into a semiconductor must be used as a material of the internal electrode. Must. For this reason, when using a conventional material as the dielectric porcelain of the multilayer capacitor, expensive platinum or palladium which has a high melting point and is hardly oxidized at a high temperature must be used as a material of the internal electrode.
This hindered the cost reduction of multilayer capacitors.

Therefore, in order to solve the above problems,
It has been desired that the material of the internal electrodes be changed from expensive noble metals to inexpensive base metals such as nickel and copper. However, using such a base metal as the material of the internal electrode,
When firing under conventional conditions, the electrode material is oxidized or melted. Therefore, in order to use such a base metal as a material for the internal electrode, it does not turn into a semiconductor even when fired at a low temperature in a neutral or reducing atmosphere having a low oxygen partial pressure, and as a dielectric ceramic material for a capacitor. There has been a need for a dielectric ceramic composition having sufficient specific resistance and excellent dielectric properties.

A dielectric porcelain composition for solving this kind of problem is disclosed in Japanese Patent Application Laid-Open No. 1-108808. This dielectric ceramic composition can be fired in a neutral or reducing atmosphere having a low oxygen partial pressure. Therefore, a multilayer capacitor for temperature compensation using a base metal such as nickel or copper as a material of an internal electrode can be provided by using this dielectric ceramic composition. But,
This dielectric porcelain composition solves the above-mentioned problems with respect to the firing temperature and the temperature coefficient of the dielectric, but has a Q value of 1
It was as small as 2000 or less at MHz.

[0007] Therefore, the main object of the present invention is to provide a neutral or reducing atmosphere having a low oxygen partial pressure.
Sintered without reduction at a low temperature of 000 ° C. or less, and the absolute value of the temperature coefficient of capacitance is 60 ppm / ° C. or less, the Q value is 2500 or more, and the specific resistance at 20 ° C. is 1
An object of the present invention is to provide a dielectric ceramic composition for temperature compensation which can provide a dielectric ceramic having a density of × 10 ¹³ Ωcm or more and can use a base metal such as copper as an internal electrode.

[0008]

SUMMARY OF THE INVENTION The present invention comprises magnesium oxide, calcium oxide, strontium oxide, silicon oxide, zirconium oxide and aluminum oxide as main components, and reduces the total content of magnesium oxide, calcium oxide and strontium oxide. (Mg _1-ab Ca
_a Sr _b) O (provided that, 0 <a, 0 <b , 0 <a + b ≦
0.95) and converted to X parts by weight, and the total content of zirconium oxide and aluminum oxide is defined as ｛(Zr
O ₂ ) _1-c (Al ₂ O ₃ ) _c ｝ (where 0 ≦ c ≦ 0.
5) and converted to Y parts by weight, and the content of silicon oxide
When converted to O ₂ and expressed as Z parts by weight (however, X + Y +
Z = 100), the following points A, B, C and D (X, Y,
Z) A (50, 2.5, 47.5) B (50, 30, 20) C (20, 60, 20) D (20, 2.5, 77.5) Surrounded by a polygon with vertices Titanium oxide is further added to 100 parts by weight of
This is a dielectric ceramic composition for temperature compensation to which W parts by weight (where 0 ≦ W ≦ 10) is added in terms of O ₂ .

[0009]

According to the present invention, in a neutral or reducing atmosphere having a low oxygen partial pressure, it is sintered without being reduced at a low temperature of 1000 ° C. or less, and the absolute value of the temperature coefficient of capacitance is obtained. Is 60 ppm / ° C. or less, the Q value is 2500 or more, and a dielectric ceramic composition for temperature compensation capable of obtaining a dielectric ceramic having a characteristic of a specific resistance of 1 × 10 ¹³ Ωcm or more at 20 ° C. is obtained. Can be Therefore, when this dielectric ceramic composition for temperature compensation is used as a material for a multilayer capacitor, a base metal such as copper can be used as an internal electrode. Therefore, it is possible to eliminate an increase in the cost of the electrodes due to the increase in the capacity of the multilayer capacitor, and to provide a low-cost multilayer capacitor. Further, since the dielectric ceramic obtained from the dielectric ceramic composition for temperature compensation has a high Q value, it can be used as a material for high frequency LC filters, RF modules and the like.

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.

[0011]

EXAMPLE First, as a starting material, the main component was MgC.
O ₃ , CaCO ₃ , SrCO ₃ , ZrO ₂ , Al ₂ O ₃
And SiO ₂ and TiO _{2 as a} sub-component were weighed so as to have the compositions shown in Table 1, respectively.
After wet mixing for 6 hours, the mixture was evaporated to dryness to obtain a mixed powder.

Next, the mixed powder was calcined at 850 ° C. for 2 hours, and 8 parts by weight of vinyl acetate was added thereto as a binder.
The mixture was again wet-mixed and pulverized by a ball mill for 16 hours to obtain a pulverized product.

[0013] The pulverized material was evaporated to dryness and sized to obtain a granular powder. Then, the granular powder thus obtained was pressed with a dry press at a pressure of ² ton / cm ² and formed into a disc having a diameter of 20 mm and a thickness of 1.0 mm to obtain a molded product.

Next, this molded product was fired in an N ₂ -H ₂ gas atmosphere at each temperature condition shown in Table 2 for 2 hours to obtain a fired device.

[0015] Furthermore, In-
A sample (capacitor) is formed by applying a Ga alloy to form an electrode
1 to 22 were produced.

Then, the obtained sample was measured for dielectric constant ε, Q value, temperature coefficient of capacitance α (ppm / ° C.), 20
Each characteristic of the specific resistance ρ ₂₀ (Ωcm) at ° C. was measured under the following conditions and measuring methods, and the results are shown in Table 2. (1) Dielectric constant ε: Measured under the conditions of a frequency of 1 MHz, a voltage of 1 Vrms and a temperature of 20 ° C. (2) Q value (quality factor): frequency 1 MHz, voltage 1 Vr
The measurement was performed under the conditions of ms and a temperature of 20 ° C. (3) Temperature coefficient of capacitance alpha (ppm / ° C.): was determined by the following equation from the capacitance C ₈₅ Metropolitan in the electrostatic capacitance C ₂₀ and 85 ° C. at 20 ° C.. α (ppm / ° C.) = {(C ₈₅ −C ₂₀ ) / C ₂₀ } × {1 / (85−20)} × 10 ⁶ (4) Specific resistance ρ ₂₀ (Ωcm) at 20 ° C .: 500 V at 20 ° C. Was determined from the current value flowing when the DC voltage was applied.

In Tables 1 and 2, those marked with * are out of the scope of the present invention, and the others are within the scope of the present invention.

[0018]

[Table 1]

[0019]

[Table 2]

Further, as shown in the ternary diagram of composition of the main component of each sample shown in Table 1 and Table 2 in FIG. In this drawing, the number with a circle indicates each sample number.

Furthermore, in the figure 1, the region showing the main component composition ratio of the composition of the invention, illustrated composition point A, B, in square with an apex C and D. That is, the sum of the contents of magnesium oxide, calcium oxide, and strontium oxide is converted to (Mg _{1 -abCa a} Sr _b ) O as X parts by weight, and the sum of the contents of zirconium oxide and aluminum oxide is _expressed as ｛(ZrO ₂ ) _1-c (Al ₂ O ₃ )
_c Converted to 重量, Y parts by weight, and the content of silicon oxide
When converted to O ₂ and expressed as Z parts by weight (however, X + Y +
Z = 100), and the composition ratio (X, Y, Z) of the main components of the composition of the present invention is represented by composition point A (50, 2.5, 47.
5), B (50, 30, 20), C (20, 60, 2)
0) and D (20, 2.5, 77.5) correspond to the composition ratio in a region surrounded by a polygon having vertices.

In the composition according to the present invention, titanium oxide is added in an amount of W parts by weight (where 0 ≦ W ≦ 10) in terms of TiO ₂ with respect to 100 parts by weight of the main component.

In the figure, 0 <a, 0 <b, 0 <a + b ≦ 0.9 in the composition according to the present invention.
It is not shown that the relationship of 5,0 ≦ c ≦ 0.5 holds.

Next, explaining the temperature compensation dielectric ceramic composition according to the present invention have been selected for the reasons to the above-mentioned range. (1) In the composition region outside the line connecting the composition points A and B shown in the three-component composition diagram, the Q value is 2500 or less, and the glassy material floats on the surface of the sintered ceramic body. See Sample No. 6). (2) In the composition region outside the line connecting the composition points A and D shown in the three-component composition diagram, the Q value is 2500 or less, the specific resistance is less than 10 ¹³ Ωcm, and the surface of the sintered ceramic body is It is not preferable because vitreous material floats on the surface (see sample No. 5). (3) In the composition region outside the line connecting the composition points B and C shown in the three-component composition diagram, a dense sintered body cannot be obtained even when fired at a temperature of 1150 ° C. (Sample No. 7) reference). (4) In the composition region outside the line connecting the composition points C and D shown in the three-component composition diagram, the Q value is 2500 or less and the specific resistance is less than 10 ¹³ Ωcm, which is not preferable (see Sample No. 8). ). (5) When a + b is larger than 0.95, the firing temperature is 1
2,000 ° C. or higher, which is not preferable (see sample numbers 12 and 14). (6) If c is larger than 0.5, it is not preferable because a dense sintered body cannot be obtained even when firing at a temperature of 1150 ° C. (see Sample No. 18). (7) When W is larger than 10, the firing temperature is 1000 ° C.
This is not preferable because the Q value becomes 2500 or less and the absolute value of the temperature coefficient of the capacitance becomes greater than 60 ppm / ° C. (see Sample No. 22).

[0025] In contrast, in the sample in the scope of the invention, in a reducing atmosphere and sintered at a low temperature of 1000 ° C. or less, the absolute value of the temperature coefficient of capacitance 60 ppm / ° C.
The following characteristics are obtained: a high quality factor (Q value) of 2500 or more, and a specific resistance at 20 ° C. of 1 × 10 ¹³ Ωcm or more.

[0026] Thus, by using the dielectric ceramic composition according to the present invention as a dielectric ceramic capacitor, it is possible to use a base metal such as copper as internal electrodes. Therefore, it is possible to eliminate the increase in the cost of the electrodes accompanying the increase in the capacity of the multilayer capacitor, and to obtain a low-cost multilayer capacitor. In addition, since the dielectric ceramic composition has a high Q value, an LC filter for high frequency,
It can be used as a material for RF modules and the like.

In the above embodiment, a reducing atmosphere composed of N ₂ -H ₂ was used as the sintering atmosphere. However, in the present invention, Ar, CO, CO ₂ , H ₂ , N ₂ and a mixed atmosphere gas thereof are used. It is needless to say that may be used.

[Brief description of the drawings]

FIG. 1 is a three-component composition diagram showing the mixing ratio of the main components of the composition of the present invention.

[Table 1]

[Table 2]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Sakabe 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd. (56) References JP-A-60-137868 (JP, A) JP-A-62-252341 (JP, A) JP-A-63-295473 (JP, A) JP-A-1-102808 (JP, A)

Claims (1)

(57) [Claims] The present invention comprises magnesium oxide, calcium oxide, strontium oxide, silicon oxide, zirconium oxide and aluminum oxide as main components, and the total content of magnesium oxide, calcium oxide and strontium oxide is expressed as (Mg _1-ab Ca
_a Sr _b) O (provided that, 0 <a, 0 <b , 0 <a + b ≦
0.95) and converted to X parts by weight, and the total content of the zirconium oxide and the aluminum oxide is {(ZrO ₂ ) _{1 -c} (Al ₂ O ₃ ) _c } (where 0 ≦
c ≦ 0.5), and the silicon oxide content is converted to SiO ₂ to be Z parts by weight (where X + Y + Z = 100), and the following points A, B, C and D (X, Y, Z) A (50, 2.5, 47.5) B (50, 30, 20) C (20, 60, 20) D (20, 2.5, 77.5) In the composition within the range surrounded by the polygon having the apex, titanium oxide is further converted to TiO ₂ with respect to 100 parts by weight of the main component and W parts by weight (where 0 ≦ W ≦ 10).
An added dielectric ceramic composition for temperature compensation.