JP3319704B2 - Dielectric porcelain composition and porcelain capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition, and more particularly, to a dielectric layer of a low-capacity ceramic capacitor of about 0.01 pF to 30 pF used in a high frequency range of several hundred MHz to several GHz. The present invention relates to a dielectric porcelain composition suitable for a porcelain and a ceramic capacitor using the dielectric porcelain composition.

[0002]

_2. Description of the Related Art Hitherto, as a material of a dielectric layer of a low-capacity ceramic capacitor used in a high-frequency region, TiO ₂ material, CaTiO ₃ material, LaTiO ₃ material, CaTiO ₃ material,
Low dielectric constant dielectric ceramic compositions such as ZrO ₃ -based materials and MgTiO ₃ -based materials have been used.

[0003] These dielectric porcelain compositions have firing temperatures as high as 1200 to 1500 ° C, have a relatively high dielectric constant for use in low-capacity porcelain capacitors, and use pure Pd as an internal electrode material. Disadvantageously, delamination is easily caused.

[0004]

Applicant The object of the invention is to solve the above-as to improve these disadvantages, magnesium silicate, zinc _{[(Mg a Zn (1-} a)) X SiO X + 2], alumina [A
l ₂ O ₃ ] and strontium titanate [SrTiO
₃ ] has been proposed prior to the present application.

[0005] The dielectric porcelain composition according to this proposal comprises 11
It is a material which can be fired at a temperature of 00 ° C. or less, has a small dielectric constant ε _r of 15 or less, and has excellent characteristics that delamination does not occur even when pure Pd is used as a material of an internal electrode.

However, the dielectric ceramic composition according to this proposal has a problem that when used for the dielectric layer of a ceramic capacitor, the leakage current is slightly large.

The present invention can be fired at a temperature of 1100 ° C. or less, has a dielectric constant ε _r of 15 or less, does not cause delamination even when pure Pd is used as a material of an internal electrode, and has a dielectric layer of a ceramic capacitor. It is an object of the present invention to provide a dielectric ceramic composition having a low leakage current (1.0 μA or less at 125 ° C.-600 V) when used in a ceramic capacitor and a ceramic capacitor using the dielectric ceramic composition.

[0008]

SUMMARY OF THE INVENTION The dielectric ceramic composition according to the invention have the general formula _{X (Mg a Zn (1-} a)) X SiO X + 2 -YAl 2 O 3 -
It contains a main component represented by ZSrTiO ₃ and an additional component comprising a compound of one or more elements selected from Nb, Ta and W, and contains magnesium silicate / zinc silicate [(Mg _a Zn _(1-a) ) _X SiO _{X + 2} ], alumina [A
l ₂ O ₃ ] and strontium titanate [SrTi
In the three-component composition diagram in which the molar ratio [%] of O ₃ ] indicates the molar ratio (X, Y, Z) of these three compounds, A (94.9, 0.1, 5.0) B (85.0, 10.0, 5.0) C (65.0, 10.0, 25.0) D (65.0, 0.1, 34.9) And the values of a and x in the general formula representing the main component are in the range of 0.1 ≦ a ≦ 0.80 0.67 ≦ x ≦ 1.50 Wherein the additional components are NbO _5/2 , TaO _5/2
Or in terms of WO ₃ is contained 0.01 to 0.2 mol%

Here, the reason why the molar ratio [%] of MZS falls within the above range is that if the molar ratio [%] of MZS deviates from the above range, a dense sintered body can be obtained by firing at 1100 ° C. or lower. or it is no longer, since the dielectric constant epsilon _r is larger than 15, even if the temperature coefficient TCC too large on the negative side.

Further, the molar ratio of Al ₂ O ₃ a [%] was set to the above range, the molar ratio of Al ₂ O ₃ [%] is outside the above range, dense in firing 1100 ° C. or less This is because a sintered body cannot be obtained.

Further, the molar ratio of ST to [%] was set to the above range, the molar ratio of ST [%] is greater than the above range, or the dielectric constant epsilon _r is greater than 15, the temperature coefficient TCC Is too large on the negative side, and when the molar ratio [%] of ST is smaller than the above range, 1100
This is because a dense sintered body cannot be obtained by firing at a temperature of not more than ℃.

The reason why the value of a is set in the above range is that a
Is larger than the above range, a dense sintered body cannot be obtained by firing at 1100 ° C. or less, and when the value of a is smaller than the above range, many pores are generated inside the sintered body and Q This is because the value becomes smaller than 1000.

The reason why the value of x is in the above range is that x
If the value of x is larger than the above range, a dense sintered body cannot be obtained by firing at 1100 ° C, and if the value of x is smaller than the above range, the appropriate temperature range during firing becomes extremely narrow, and Easy to wear, many pores are generated in the sintered body,
This is because the Q value becomes smaller than 1000.

The reason why the content of the additive is 0.01 to 0.2 mol% in terms of NbO _5/2 , TaO _5/2 or WO ₃ is that when the content is less than 0.01 mol%, the leakage current is improved. This is because there is no effect, and if it exceeds 0.2 mol%, a dense sintered body cannot be obtained by firing at 1100 ° C. or less. The same effect can be obtained by adding these additives alone or in a mixed state.

The desired characteristics can be obtained with or without calcination of the mixture comprising MZS, Al ₂ O ₃ and ST, but the electrical characteristics change depending on the presence or absence of calcination. However,
The calcination is effective when a reaction occurs between the additive component and the main component or between the additive components, the crystal system changes, and sudden shrinkage occurs or the shrinkage rate increases. That is, it is effective in suppressing structural defects such as delamination and cracks.

Further, the porcelain capacitor according to the present invention comprises:
The above dielectric ceramic composition is used as a dielectric layer. Here, Pd can be used as the material of the internal electrode, but Ag and Pt may be used. The porcelain capacitor can be applied to both a single-layer type and a multilayer type.

Further, the porcelain capacitor according to the present invention comprises:
Although it can be used sufficiently even in the low frequency range, especially, several hundred MHz
z to 0.01 pF used in a high frequency range of several GHz
It is suitable for use as a low-capacity porcelain capacitor of about 30 pF.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, MgO, ZnO and SiO
₂ were weighed at the ratios shown in Tables 1 to 1, and were put into a ball mill and pulverized and mixed for 15 hours in a wet system to obtain a slurry composed of these mixtures. Next, the slurry was taken out and filtered.
And dried sufficiently to obtain a powder of the mixture.

Next, the powder of this mixture is placed in a heating furnace,
Calcination was performed at 900 to 1200 ° C., and the compounds constituting the mixture were reacted with each other to obtain MZS. The sample N
o. 62-66 did not calcine.

Next, the MZS was put into a ball mill and sufficiently pulverized by a wet method to obtain MZS slurry. Next, take out the slurry, filter it, put the cake part in a dryer,
After sufficiently drying at 150 ° C., powder of MZS was obtained.

Next, MZS, Al ₂ O ₃ , ST and Nb
₂ O ₅ was weighed at the ratios shown in Tables 1 to 1, placed in a ball mill, and thoroughly mixed by a wet method to obtain a slurry composed of these mixtures. Next, the slurry was taken out and filtered, and the cake portion was put in a drier and dried sufficiently at 150 ° C. to obtain a powdery mixture.

Next, the powder of this mixture is placed in a heating furnace,
Calcination was performed at 700 to 900 ° C. for 2 to 4 hours. The sample N
o. 1-21, 28-30, 32-34, 36, 37,
39-66 did not calcine.

Next, an organic binder is added to the mixture, and the mixture is granulated and press-molded to form a disk-shaped sample having a diameter of about 10 mm and a thickness of about 0.5 mm.
4 hours firing and sintering, applying Ag paste, 70
It was baked at 0 ° C. for 15 minutes to form external electrodes, thereby forming a porcelain capacitor.

On the other hand, an organic solvent, an organic binder, a plasticizer and the like are added to the powder of the mixture and mixed to form a slurry. From the slurry, a ceramic green sheet having a thickness of 40 μm is obtained by a doctor blade method. A Pd electrode paste was printed in a predetermined pattern on the surface of the sample, and 11 sheets were alternately laminated and pressed to form a 10-layer laminate, and the obtained laminate was cut to obtain a plurality of chip laminates. .

Next, the sample is subjected to a binder removal treatment.
It is fired at about 950 to 1100 ° C for 1 to 4 hours, and an Ag paste is applied to both ends of the obtained sintered body sample.
For 15 minutes to form external electrodes, thereby forming a laminated ceramic capacitor (sample size: 1.0 mm × 0.5 m)
m × 0.5 mm, effective intersection area: 0.05 mm ² , thickness per dielectric layer: 30 μm)

[0026]

[Table 1]

[0027]

[Table 1]

[0028]

[Table 1]

Next, for the disk porcelain capacitor and the laminated porcelain capacitor, room temperature, HP4284A, 1 MHz,
C and Q were determined under the condition of 1 V _rms . The dielectric constant, the insulation resistance at 150 ° C., and the temperature coefficient of the dielectric constant (change rate of 85 ° C. based on 20 ° C.)
The average was determined. The results were as shown in Tables 2 and 2.

The insulation resistance ρ in Tables 2 and 2
, For example, 2.10E + 07 represents 2.10 × 10 ⁷ . The temperature coefficient TCC was calculated using the following equation (1). The leakage current is 600
V DC was applied, and the current value when stabilized was measured using a digital multimeter (YOKOGAWA7552).

[0031]

(Equation 1)

[0032]

[Table 2]

[0033]

[Table 2]

[0034]

[Table 2]

From the results shown in Tables 2 and 2, the following can be understood. That is, the sample No. As shown in 53, 54 and 55, the molar ratio [%] of MZS is 65.0 mol [%].
When fewer, or dense sintered bodies by firing 1100 ° C. or less can not be obtained, the dielectric constant epsilon _r is larger than 15, the temperature coefficient TCC becomes too large on the negative side.

Sample No. As shown in FIGS. 11 and _{30, when} the molar ratio [%] of Al ₂ O ₃ is more than 10.0 mol%, a dense sintered body cannot be obtained by firing at 1100 ° C. or less. 43, Al ₂ O ₃
When the molar ratio [%] is less than 0.1 mol%, 11
If the firing is performed at a temperature of 00 ° C. or less, a dense sintered body cannot be obtained.

Sample No. As shown in FIGS. 54 and 55, when the molar ratio [%] of ST is more than 34.9 mol%, a dense sintered body cannot be obtained or the dielectric constant becomes large, and the temperature coefficient becomes negatively large. Too much,
Sample No. As shown in 1, 11, the molar ratio of ST [%]
Is less than 5.0 mol%, a dense sintered body cannot be obtained by firing at 1100 ° C.

Sample No. As shown in FIGS. 31 and 32, when the value of a is larger than 0.8, a dense sintered body cannot be obtained by firing at 1100 ° C. As shown in 39, when the value of a is smaller than 0.1, there are many pores inside the sintered body, and the Q value is smaller than 1000.

The sample No. As shown in FIG. 59, when the value of x is larger than 1.5, a dense sintered body cannot be obtained by firing at 1100 ° C. As shown in 61, when the value of x is smaller than 0.67, the sintered body is easily fused, the appropriate firing temperature range becomes very narrow, and many pores are generated in the sintered body. , Q value is smaller than 1000.

The sample No. As shown in 2,3,13,14, NbO _5/2 , TaO _5/2 , WO ₃ are 0.01
If it is less than mol%, the leak current becomes 1.0 μA or more, and the effect of improving the leak current is lost.
As shown in FIGS. 7 and 17, when the content exceeds 0.2 mol%, 1
At 100 ° C., a dense sintered body cannot be obtained.

The sample No. 4 ~ 6,8,9,10,
As shown in 12, 15, and 16, the additive component NbO
_5/2, TaO _5/2, the addition of WO ₃ in the range of 0.01 to 0.2 mol%, any effect of improving leakage current is observed. In addition, the sample No. As shown in 45 to 48, the same effect can be obtained by adding these additional components in a mixed state.

The desired characteristics can be obtained with or without calcination of the mixture comprising MZS, Al ₂ O ₃ and ST, but the electrical characteristics change depending on the presence or absence of calcination. However, the calcination is effective when a reaction occurs between the added component and the main component or between the added components, the crystal system changes, and sudden shrinkage occurs or the shrinkage ratio increases. That is,
It is effective in suppressing structural defects such as delamination and cracks.

The dielectric porcelain composition according to the present invention, that is, the sample evaluated as “good” in Tables 1 to 1, was 11
It can be sintered by firing at 00 ° C or less, has a low dielectric constant of 15 or less, has a high Q value (1000 or more at 1 MHz), and has a dielectric constant of 150 ° C.
High resistivity (1.0 × 10 ³ MΩcm or more), low temperature coefficient of capacitance, JIS standard CH characteristics (−60 to +60 [ppm / ° C.]) CJ characteristics (−120 to +120 [ppm / ° C]) PH characteristics (-90 to -210 [ppm / ° C]) RH characteristics (-160 to -280 [ppm / ° C]) SH characteristics (-270 to -390 [ppm / ° C]) You can see that.

[0044]

According to the present invention, it is possible to obtain a low-capacity (0.01 pF to 30 pF) porcelain capacitor having a high Q value in a high-frequency region of several hundred MHz to several GHz and a small loss and leakage current. There is.

Further, according to the present invention, the sintering temperature of the dielectric ceramic composition can be lowered to 1100 ° C. or less, so that structural defects such as delamination can be suppressed, and the sintering temperature at the time of manufacturing a ceramic capacitor can be reduced. Power cost can be reduced, and the cost can be reduced.

Further, according to the present invention, since pure Pd can be used as the material of the internal electrode, there is an effect that a highly reliable ceramic capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is a three-component composition diagram showing the molar ratio [%] of MZS, Al ₂ O ₃ and ST.

[Table 1 ○ 1]

[Table 1 ○ 2]

[Table 1 ○ 3]

[Table 2 ○ 1]

[Table 2 ○ 2]

[Table 2 ○ 3]

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 35/16 C04B 35/46

Claims (4)

(57) [Claims] 1. A compound of the general formula X (Mg _a Zn _(1-a) ) _X SiO _{X + 2} —YAl ₂ O ₃ —
It contains a main component represented by ZSrTiO ₃ and an additive component composed of a compound of one or more elements selected from Nb, Ta and W, and contains magnesium silicate / zinc silicate [(Mg
_a Zn _(1-a) ) _X SiO _{X + 2} ], alumina [Al ₂ O
₃ ] and the molar ratio [%] of strontium titanate [SrTiO ₃ ] are the molar ratios of these three compounds (X, Y,
In the three-component composition diagram showing Z), A (94.9, 0.1, 5.0) B (85.0, 10.0, 5.0) C (65.0, 10.0, 25.0) D (65.0, 0.1, 34.9) is within a range surrounded by a polygon having the vertices of each of the points A to D, and a in the general formula representing the main component. And x are in the range of 0.1 ≦ a ≦ 0.80 0.67 ≦ x ≦ 1.50, and the additive component is 0 in terms of NbO _5/2 , TaO _5/2 or WO _3. 0.1 to 0.2 mol%. Wherein the general formula _{X (Mg a Zn (1-} a)) X SiO X + 2 -YAl 2 O 3 -
It contains a main component represented by ZSrTiO ₃ and an additive component composed of a compound of one or more elements selected from Nb, Ta and W, and contains magnesium silicate / zinc silicate [(Mg
_a Zn _(1-a) ) _X SiO _{X + 2} ], alumina [Al ₂ O
₃ ] and the molar ratio [%] of strontium titanate [SrTiO ₃ ] are the molar ratios of these three compounds (X, Y,
In the three-component composition diagram showing Z), A (94.9, 0.1, 5.0) B (85.0, 10.0, 5.0) C (65.0, 10.0, 25.0) D (65.0, 0.1, 34.9) is in a range surrounded by a polygon having the vertices of each of the points A to D, and the values of a and x in the above general formula Is in the range of 0.1 ≦ a ≦ 0.8 0.67 ≦ x ≦ 1.5, and the added component is 0.01 to 0 in terms of NbO _5/2 , TaO _5/2 or WO _3. A ceramic capacitor using a dielectric ceramic composition containing 2 mol% as a dielectric layer. 3. The porcelain capacitor according to claim 2, wherein pure Pd is used as a material of the internal electrode. 4. The porcelain capacitor according to claim 2, wherein dielectric layers and internal electrodes are alternately laminated.