JPH06302467A - Dielectric porcelain composition and multilayer ceramic capacitor using dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a multilayer ceramic capacitor which can ensure a sufficient electrostatic capacity even under high-temperature surroundings without increasing the number of laminates. CONSTITUTION:A multilayer capacitor is constituted of a dielectric porcelain composition which contains 0.75 to 0.5mol of MnO and 0.05 to 0.5mol of Y2O3 with reference to 100mol of BaTiO3 and, in addition, of a dielectric porcelain composition which contains 4.6mol or higher of at least one kind out of Al2O3 and SiO2. The permittivity of the compositions has a maximum value between 85 and 125 deg.C, the permittivity has a high value by 15% of higher as compared with that at room temperature, and the permittivity at room temperature is 2000 or higher. It is desirable to use BaCO3 at a purity of 97.1% or higher and TiO2 at a purity of 97.5% or higher as starting raw materials.

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 a laminated ceramic capacitor using the dielectric ceramic composition, and more particularly, to a dielectric ceramic composition whose capacitance increases as the operating environment temperature rises. The present invention relates to a laminated ceramic capacitor.

[0002]

2. Description of the Related Art As is widely known, a monolithic ceramic capacitor is constructed by alternately laminating ceramic dielectrics and internal electrodes. Conventionally, a multilayer ceramic capacitor is often required to have electric characteristics such as a dielectric constant, particularly stable temperature characteristics over a wide temperature range. For example, the B characteristic of the JIS standard specifies that the rate of change in capacitance is within ± 10% in the temperature range of -25 ° C to 85 ° C, and the X7R characteristic of the EIA standard specifies a temperature range of -55 ° C to 125 ° C. It is specified that the rate of change in capacitance in the temperature range is within ± 15%.

Since the relative permittivity has a negative temperature coefficient, when used in a high temperature environment, JIS-B
Even a monolithic ceramic capacitor that satisfies the characteristics is 85
Maximum -10% when used in temperature environment of ℃, EIA
-Multilayer ceramic capacitors that meet X7R characteristics 12
When used in a temperature environment of 5 ° C, a maximum decrease of -15% in electrostatic capacity is allowed.

In the case of a motor using a brush, a spark is generated in order for the motor to rotate because an electric current is intermittent between the commutator attached to the rotary shaft of the motor and the fixed brush. When the inductance of the coil of the motor is large, a large noise voltage is generated due to this intermittent current, and the repeated application of this noise voltage destroys the insulating layer of the coil, which may render the motor unusable.

In order to prevent such an accident, a brush-type motor uses a capacitor for absorbing noise voltage. A monolithic ceramic capacitor is generally used as a noise voltage absorbing capacitor. However, since the ceramic dielectric used in the monolithic ceramic capacitor has JIS-B characteristics or EIA-X7R characteristics, When the temperature finally rises to about 85 ° C. along with the rotation, the electrostatic capacity decreases, and it is not possible to absorb the noise voltage sufficiently, which causes the motor life to be shortened.

As described above, in order to make the capacitance of a monolithic ceramic capacitor used in a high temperature environment such as a noise voltage absorbing capacitor of a motor sufficient in a high temperature region, the capacitance at room temperature is Need to be bigger. Therefore, when using a conventional monolithic ceramic capacitor to remove noise from a motor, it is necessary to increase the capacitance at room temperature in order to secure the capacitance in a high-temperature environment. This is a cause of rising manufacturing costs.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The problems of the above-mentioned conventional monolithic ceramic capacitor are as follows:
The problem that the electrostatic capacity cannot be ensured in a high temperature environment is solved, and a sufficient electrostatic capacity can be secured even in a high temperature environment without increasing the number of laminated layers.
An object of the present invention is to obtain a multilayer ceramic capacitor that can efficiently remove noise when used for removing noise from a motor and can prolong the life of a device that uses the multilayer ceramic capacitor.

[0008]

In order to solve the above-mentioned problems, in the present application, a ceramic dielectric material having a larger dielectric constant at high temperature than at room temperature, that is, "BaTiO ₃ " is used.
0.75 to 0.5 mol part of MnO with respect to 100 mol part,
The present invention is characterized in that it is a dielectric porcelain composition characterized by containing Y ₂ O ₃ in an amount of 0.05 to 0.5 mol, and "MnO is 0.75 with respect to 100 mol of BaTiO _3.
~0.5mol unit, provides invention to adopt a configuration that the Y ₂ O ₃ multilayer ceramic capacitor using the dielectric ceramic composition characterized by containing 0.05~0.5mol part ".

[0009]

The dielectric constant of the ceramic dielectric material according to the present invention has a positive temperature coefficient and reaches its maximum value at 85 ° C. to 125 ° C. Therefore, a monolithic ceramic capacitor using this ceramic dielectric material can be used in a high temperature environment. Even in Japan, a sufficient electric capacity is maintained.

[0010]

EXAMPLES Examples of the present invention will be described below. First Example A ceramic sample having the composition shown in Table 1 was prepared by the method described below.

[Table 1]

(1) BaCO ₃ having a purity of 97.5% and a purity of 9
8.1% TiO ₂ was weighed, wet mixed and ground using a ball mill or the like. (2) Dried and molded, put in a zirconia sheath, 11
It was calcined at 70 ° C to 1250 ° C. (3) The particle size is 0.5 to 0.5 after coarsely crushing the calcined molded body.
It was finely pulverized to a size of 2.5 μm and dried at 150 ° C. (4) The BaTiO ₃ thus completed was weighed and mixed so that the composition ratio shown in Table 1 was obtained.
A mixed solvent and a binder were added to this mixture and dispersed to obtain a paste. (5) A ceramic green sheet having a thickness of about 30 μm was prepared from this paste, and Ni internal electrodes were printed, dried and laminated to obtain a laminated body of 5 layers having a shape of 3.2 mm × 1.6 mm. (6) The binder is removed from the binder, and the temperature is 1200 ° C to 140 ° C.
Firing at 0 ° C. for 2 hours in a reducing atmosphere with a volume ratio of H ₂ / N ₂ of 3/100, and then performing 1 at O ₂ partial pressure of 100 ppm or less.
Annealing was performed at 000 ° C. for 2 hours to obtain a porcelain. (7) Copper paste was applied to both end surfaces of the obtained porcelain and baked to form electrodes, thereby forming a capacitor. (8) Regarding the capacitor thus obtained,
Relative permittivity ε ₂₀ , dielectric loss tan at room temperature (20 ° C)
δ (%), insulation resistance value logIR (Ω), capacitance temperature change rate Cmax (%), temperature Tcp showing maximum value of electrostatic capacitance
(° C) was measured.

The various data were measured under the following conditions. Relative permittivity ε ₂₀ and dielectric loss tan δ at room temperature
Was measured by applying an alternating current having a frequency of 1 KHz and a voltage of 1 V at a temperature of 20 ° C. Insulation resistance value logIR is DC at 20 ℃
It is the log value of the resistance value measured after applying a voltage of 50 V and 1 minute. The capacitance temperature change rate Cmax is a change rate of the capacitance with respect to temperature in the range of −55 ° C. to 125 ° C., and the temperature (T _CP ) at which the capacitance shows the maximum value is also shown. An accelerated life test in which a direct current of 100 V was continuously applied at 200 ° C. was performed, and the time when the capacitor was broken was measured.

The results are shown in Table 2.

[Table 2]

In evaluating the test results, the maximum capacitance change rate Cmax is + 15% or more, the accelerated life of the capacitor is 10 hours or more, the relative dielectric constant at room temperature is 2,000 or more,
Curie point is 85 ° C to 125, which is the normal operating temperature range
Those having a temperature of ° C were evaluated as good, and other samples were evaluated as bad.

If MnO is less than 0.75 mol, the chip will be deformed. (Sample 1) When the amount exceeds 5 mol, the maximum capacitance change rate Cmax becomes less than + 15%. (Sample 5)

As a result of the accelerated life test of the capacitor,
When Y ₂ O ₃ is 0.05 mol, it is 12.3 hours, and when it is 1 mol or more, it is 24 hours or more. Therefore, when Y ₂ O ₃ is less than 0.05 mol, the accelerated life of the capacitor itself is short and it cannot be practically used. (Sample 6) If Y ₂ O ₃ exceeds 0.5 mol, it becomes a semiconductor. (Sample 9)

A is a sintering aid for lowering the sintering temperature.
By adding 1 ₂ O ₃ or SiO ₂ , firing at low temperature becomes possible. Firing is possible even if Al ₂ O ₃ or SiO ₂ is not added, but high-temperature firing is required, so the internal electrodes may be interrupted. But,
When Al ₂ O ₃ and SiO ₂ exceed 4.6 mol, the relative dielectric constant at room temperature becomes 2,000 or less, and the maximum rate of change Cmax of the electrostatic capacitance also becomes small. (Samples 14, 18)

SrT which is a shifter for lowering the Curie point
By adding iO ₃ , the Curie point on the high temperature side such as 125 ° C. can be lowered to around 85 ° C. Therefore, it is not necessary to add SrTiO ₃ when the operating temperature of the equipment rises to around 100 to 125 ° C., but SrTiO ₃ does not need to be added when the operating temperature is about 85 ° C. to 100 ° C.
The Curie point can be lowered by adding TiO ₃ . However, when SrTiO ₃ exceeds 10 mol, the Curie point is lowered to 70 ° C., so that it is not possible to secure the electrostatic capacitance in the operating temperature range of 85 ° C. to 125 ° C. (Sample 23)

FIG. 1 shows the rate of change in electrostatic capacitance with respect to temperature of a laminated ceramic capacitor using the ceramic dielectric of the sample * according to the present invention and a conventional laminated ceramic capacitor using a ceramic dielectric having JIS-B characteristics. the [Delta] C / C ₂₀ shows a graph of measurement. As is clear from this graph, the rate of change in electrostatic capacitance of the monolithic ceramic capacitor using the JIS-B characteristic ceramic dielectric is substantially constant in both the room temperature environment and the high temperature environment. Therefore, the electrostatic capacity in a high temperature environment decreases, so that the electrostatic capacity in a room temperature environment must be increased.

On the other hand, the multilayer ceramic capacitor using the ceramic dielectric of Sample 12 has a temperature of 80 ° C. to 1 ° C.
The rate of change in electrostatic capacity at 00 ° C is much larger than that in the room temperature environment. Therefore, when used in this temperature range, sufficient electrostatic capacity can be obtained without increasing the electrostatic capacity at room temperature. Can be secured. Looking at this graph, the electrostatic capacitance of the monolithic ceramic capacitor using the ceramic dielectric of Sample 12 is small in the region exceeding 100 ° C.
A larger electrostatic capacity is ensured than a monolithic ceramic capacitor using a ceramic dielectric having IS-B characteristics.

FIG. 2 shows, as a representative of a laminated ceramic capacitor using the ceramic dielectric of the present invention, a laminated ceramic capacitor using the ceramic dielectrics of Samples 2, 17 and 25 and a conventional JIS-B characteristic. 7 is a graph showing the relationship between the temperature and the dielectric constant of a laminated ceramic capacitor using the ceramic dielectric material. As is clear from this graph, the dielectric constant of the monolithic ceramic capacitor using the JIS-B characteristic ceramic dielectric is substantially constant both in the room temperature environment and the high temperature environment.

On the other hand, Samples 2 and 17 according to the present invention
And 25, the multilayer ceramic capacitor using the ceramic dielectric has the maximum dielectric constant in the temperature range of 80 ° C to 125 ° C. Therefore, the monolithic ceramic capacitor using the ceramic dielectric according to the present invention has a temperature of 80 ° C.
It is clear that it has a larger electrostatic capacity in the temperature range of ˜125 ° C. than in room temperature.

Second Embodiment In the case of the first embodiment, the main raw material BaTiO ₃ is made from BaCO ₃ and TiO _2. However, BaCO ₃ contains SrC.
_{O 3, CaCO 3, Na 2} CO 3 or the like, is to the TiO ₂ similar _{Nb 2 O 5, ZrO 2,} CaO, SiO 2, P 2 O 5, PbO
Since these impurities are contained as impurities, the characteristics of the finally obtained monolithic ceramic capacitor are affected by these impurities. On the other hand, when this BaTiO ₃ is prepared by the solution method, hydrothermal synthesis, sol-gel method, etc., the purity is 99.9%.
The above can be obtained. Therefore, this purity 9
A sample having the same composition as the sample 24 as shown in Table 3 was prepared using 9.9% BaTiO ₃ , and the mixed solvent and the binder were added in the same manner as in Example 1 to form a paste, and this paste was used. A green sheet was produced by the same method as in Example 1 to obtain a 5-layer laminate.

[Table 3]

The obtained laminated body was debindered and fired in a reducing atmosphere, and then electrodes were formed to obtain a laminated ceramic capacitor. Table 4 shows the results of testing this capacitor by the same method as in the first embodiment.

[Table 4]

As shown in Table 4 and apparent from the test results, the dielectric constant ε ₂₀ at room temperature is further higher than that of the monolithic ceramic capacitor obtained by the solid phase method as in the first embodiment.
Has grown. Further, by using high-purity BaTiO ₃ , a capacitor having a large maximum capacitance change rate could be obtained.

Third Example In the first example, BaCO ₃ and TiO ₂ having purities of 97.5% and 98.1% were used. Therefore,
BaCO _3, to examine the effects of TiO ₂ of purity, Table 5 using different BaCO _3, TiO ₂ purity of the sample 24
A laminated body was prepared in the same manner as in Example 1 with the composition as shown in FIG.

[Table 5]

Table 6 shows the test results of this sample.

[Table 6]

According to this table, the purity of BaCO ₃ is 96.
The sample 26 having a purity of 4% and a purity of TiO ₂ of 96.8% has a low relative dielectric constant of 1860 although the maximum capacitance change rate is large at 170.5%. On the other hand, BaCO
Sample 27 in which the purity of ₃ is 97.1% and TiO ₂ is 975%, and sample 28 in which BaCO ₃ is 99.5% and TiO ₂ is 99.6% are 3210 and 3, respectively.
It has a high relative dielectric constant of 850, and the maximum capacitance change rates are relatively large at 25.3 and 50.1, respectively.

Fourth Example Using the ceramic dielectric material according to the present invention, a laminated ring capacitor for absorbing noise voltage having the shape shown in FIG. 3 was produced. This laminated ring capacitor body 1 is made of ceramic, and its overall shape is a disk shape, and a hole 2 through which a motor shaft penetrates is formed in the center of the disk. On the outer circumference of the disk of the laminated ring capacitor body 1, a partition 3a,
3b, 3c are formed, and these partition parts 3a, 3
The multilayer ring capacitor body 1 is divided into three capacitor elements 4a, 4b and 4c by b and 3c. Internal electrodes 5a, 5b, 5c, 5d made of Ni or the like are formed inside the laminated ring capacitor body 1, and these internal electrodes are formed on the outer periphery of the disk and coated with a copper paste.
Extraction electrode 6 formed by baking
It is connected to a, 6b, and 6c.

The shape of the laminated ring capacitor for absorbing noise voltage has an outer diameter of 10.7 mm, an inner diameter of 5.8 mm and a thickness of 1.1 mm. The capacitance of each capacitor element is 0.47 μF and the operating voltage is 38V. When this laminated ring capacitor was used in a motor, the lead electrodes 6a, 6b, 6c were plated with Ni and solder, and were connected by solder.

For comparison, a laminated ring capacitor having the shape shown in FIG. 2 was prepared using a ceramic composition of JIS standard F characteristics and B characteristics, and the life of a motor using this laminated ring capacitor was measured for a maximum of 1000 hours. did. As a result, the life of the motor using the laminated ring capacitor made of the JIS standard F characteristic ceramic composition was 47 hours, and the life of the motor using the laminated ring capacitor made of the JIS standard B characteristic ceramic composition was 723 hours. On the other hand, when the laminated ring capacitor made of the ceramic dielectric material according to the present invention was used, the life of the motor exceeded 1000 hours.

Particularly, in the case of JIS-F characteristics,
The life of the motor is extremely short because the capacitance in the high temperature range decreases. In the B characteristic, the electrostatic capacity slightly changes even at a high temperature, so the life of the motor is longer than that of the F characteristic, but it is not sufficient as compared with the product of the present invention. In the product of the present invention, since the electrostatic capacity at the high temperature portion is increased by 15% or more, the noise absorption becomes better than that at room temperature, and the life of the motor can be extended.

[0033]

As is apparent from the above description, the multilayer ceramic capacitor according to the present invention has a large capacitance at high temperature than at room temperature. Therefore, unlike the conventional monolithic ceramic capacitor, it is not necessary to increase the number of laminated layers to increase the electrostatic capacitance at room temperature in order to secure the electrostatic capacitance at a high temperature, and thus it is possible to reduce the cost by reducing the number of laminated layers.

Moreover, since the dielectric material according to the present invention is a reduction resistant material, inexpensive Ni is used as the internal electrode material used when manufacturing a laminated ceramic capacitor, instead of expensive precious metal such as Pd. can do.

The monolithic ceramic capacitor according to the present invention is useful not only for removing noise from a motor but also for eliminating noise in various devices used in a high temperature environment or when used as a bypass capacitor. It is also useful when the dielectric material according to the present invention is used to form a shape other than the ring-shaped capacitor shown in FIG. 2, that is, an ordinary monolithic ceramic capacitor, single plate capacitor, or polygonal capacitor. is there.

[Brief description of drawings]

FIG. 1 is a temperature change characteristic graph of the capacitance of a laminated ceramic capacitor using the dielectric material of the present invention.

FIG. 2 is a graph of temperature change characteristics of the dielectric constant of the dielectric material of the present invention.

FIG. 3 is a partially broken perspective view of a motor noise eliminating multilayer ring capacitor that is an embodiment of the present invention.

[Explanation of symbols]

 1 Multilayer Ring Capacitor Main Body 2 Holes 3a, 3b, 3c Partitions 4a, 4b, 4c Capacitor Elements 5a, 5b, 5c, 5d Internal Electrodes 6a, 6b, 6c Extraction Electrodes

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taku Harada 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (12)

[Claims] 1. Mn based on 100 mol parts of BaTiO ₃
O is 0.75 to 0.5 mol and Y ₂ O ₃ is 0.05 to 0.5 mol.
A dielectric porcelain composition, characterized in that it is contained in parts. 2. The dielectric ceramic composition according to claim 1, further containing 4.6 mol parts or less of at least one of Al ₂ O ₃ and SiO ₂ . _3. Sr based on 100 mol parts of BaTiO ₃
TiO ₃ is 10.0 mol parts or less, and MnO is 0.75 to 5.0 m.
ol part and Y ₂ O ₃ in an amount of 0.05 to 0.5 mol part. 4. The dielectric ceramic composition according to claim 3, further containing 4.6 mol parts or less of at least one of Al ₂ O ₃ and SiO ₂ . 5. A B having a purity of 97.1% or more as a starting material.
The dielectric ceramic composition according to claim 1, claim 2, claim 3 or claim 4, wherein aCO ₃ and 97.5% or more of TiO ₂ are used. 6. The maximum value of the dielectric constant is between 85 ° C. and 125 ° C., the dielectric constant is higher than room temperature by 15% or more, and the dielectric constant at room temperature is 2000 or more. The dielectric ceramic composition according to claim 1, claim 2, claim 3, claim 4, or claim 5. 7. Mn based on 100 mol parts of BaTiO ₃
O is 0.75 to 0.5 mol and Y ₂ O ₃ is 0.05 to 0.5 mol.
A monolithic ceramic capacitor using a dielectric porcelain composition characterized by containing a part thereof. 8. The multilayer ceramic capacitor according to claim 7, further comprising at least 4.6 mol part of Al ₂ O ₃ and SiO ₂ contained therein in a dielectric ceramic composition. 9. Sr based on 100 mol parts of BaTiO ₃
TiO ₃ is 10.0 mol parts or less, and MnO is 0.75 to 5.0 m.
ol portion, multilayer ceramic capacitor using the dielectric ceramic composition characterized in that the Y ₂ O ₃ containing 0.05~0.5mol unit. 10. The multilayer ceramic capacitor according to claim 9, which further comprises at least 4.6 mol part of Al ₂ O ₃ and SiO ₂ contained therein. 11. A dielectric ceramic composition comprising BaCO ₃ having a purity of 97.1% or more and TiO ₂ having a purity of 97.5% or more as a starting material. The laminated ceramic capacitor according to claim 9 or 10. 12. The maximum dielectric constant is between 85 ° C. and 125 ° C., the dielectric constant is 15% or more higher than room temperature, and the dielectric constant at room temperature is 2000 or more. The multilayer ceramic capacitor according to claim 7, claim 8, claim 9, claim 10, or claim 11, which uses the characteristic dielectric ceramic composition.