JPH1045468A - Dielectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable firing at a low temp. and to improve surface smoothness by incorporating barium strontium titanate, zinc oxide, a maganese compd., a titanium compd., silicon dioxide and oxide of a specified rare earth element. SOLUTION: A multiple oxide made of barium strontium titanate represented by the formula (Ba1-x Srx )TiO3 (where 0.14<x<0.20) is used as a base and blended with 0.1-0.9 pt.wt. (expressed in terms of ZnO) zinc oxide, 0.1-0.5 pt.wt. (expressed in terms of MnO2 ) manganese compd., 0.1-1.3 pts.wt. (expressed in terms of TiO2 ) titanium compd., 0.05-0.20 pt.wt. (expressed in terms of SiO2 ) silicon dioxide and 0.8-1.8 pts.wt. (expressed in terms of Nd2 O3 , Sm2 O3 , Gd2 O3 , La2 O3 , Pr6 O11 , CeO2 , Tb4 O7 or Eu2 O3 ) at least one of oxides of rare earth elements to obtain the objective dielectric porcelain compsn. satisfying characteristic stipulated by Y5V of EIA standard, having a relative dielectric constant of >=1,500, capable of firing at a low temp. of <1,300 deg.C and capable of giving a dense sheetlike sintered compact of <=10μm thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high dielectric constant type ceramic porcelain composition for forming a thin plate which can be fired at a low temperature, and more particularly to a high dielectric constant type ceramic capacitor having excellent temperature characteristics of capacitance. The present invention relates to a dielectric ceramic composition suitable as a dielectric material for multilayer ceramic capacitors, axial capacitors, disk capacitors, thick film capacitors, and the like.

[0002]

2. Description of the Related Art Conventionally, barium titanate (BaTiO ₃ ) based dielectric ceramic compositions having a relative dielectric constant of about 6,000 to 10,000 have been used as dielectric materials for high dielectric constant type ceramic capacitors and multilayer ceramic capacitors. Among them, those using the dielectric ceramic composition have been widely applied to multilayer ceramic capacitors from the viewpoint of electric capacity.

In the multilayer ceramic capacitor, an electrode is generally formed on a green sheet made of a dielectric ceramic composition, a plurality of the green sheets are stacked so as to have a predetermined electric capacity, and the electrodes are simultaneously fired and integrated. To form an internal electrode.

However, the barium titanate (B)
aTiO ₃ ) based dielectric porcelain composition has a firing temperature of 130.
In order to be used as a dielectric material of a multilayer ceramic capacitor at a high temperature of about 0 to 1400 ° C., palladium (Pd) or platinum (Pt), which is a noble metal having a high melting point and a high temperature reducing property, is used as an internal electrode material to be co-fired. And the like, which makes it difficult to manufacture a low-cost, small-sized, large-capacity multilayer ceramic capacitor.

[0005] In order to solve the above disadvantage, a dielectric material having a relative dielectric constant as high as 10,000 or more is used, and the thickness of the dielectric ceramic composition between the internal electrodes is reduced to about 30 μm. In addition to minimizing the facing area to reduce the size of the multilayer ceramic capacitor, low-temperature sintering is also possible so that the internal electrode material is replaced with the inexpensive noble metal by inexpensive Ag-Pd or the like. .

As such a dielectric material, conventionally, barium titanate (BaTiO ₃ ) has a predetermined amount of barium stannate (BaSnO ₃ ) or calcium titanate (CaTiO ₃ ).
₃ ), cobalt oxide (CoO), manganese oxide (MnO)
₂ ) and the like, or a barium titanate (BaTiO ₃ ) or calcium zirconate (C
aZrO ₃ ) and a predetermined amount of lead titanate (PbTiO ₃ )
And a dielectric ceramic composition to which lead germanate (Pb ₅ Ge ₃ O ₁₁ ), bismuth titanate (BiTi ₂ O ₇ ), or the like is added (Japanese Patent Publication No. 60-57164, Japanese Patent Publication No. 61-1986) No. 16132).

[0007]

A predetermined amount of barium stannate (BaSn) is added to the barium titanate (BaTiO ₃ ).
O ₃ ), calcium titanate (CaTiO ₃ ), cobalt oxide (CoO), manganese oxide (MnO ₂ ), etc., or a predetermined amount of barium titanate (BaTiO ₃ ) or calcium zirconate (CaZrO ₃ ). Lead titanate (PbTiO ₃ ) and lead germanate (Pb ₅ Ge)
_The conventional dielectric porcelain composition to which ₃ O ₁₁ ) and bismuth titanate (BiTi ₂ O ₇ ) are added can relatively easily increase the relative dielectric constant at room temperature to about 10,000 to 20,000. Low-temperature baking at a temperature of not more than ℃ can be realized.

By the way, in the case of electronic components whose downsizing is progressing, it is required to further reduce the thickness of a sheet-shaped sintered body made of a dielectric ceramic composition in order to achieve a smaller size and a higher capacity. And now the required thickness is 10μ
m or less.

[0009] However, in the above-mentioned conventional dielectric porcelain composition, there is a problem that the dielectric strength between the pair of electrodes is reduced when the dielectric layer is made thin. As another method for increasing the capacitance, there is a method using a porcelain having a high relative dielectric constant. However, the relative dielectric constant of a conventional BaTiO ₃ -based dielectric porcelain is limited, and a high capacitance is required. There was a limit to conversion. Further, a thickness of 10 μm
When a multilayer capacitor consisting of the following thin layers is manufactured,
A high temperature load life of less than 40 hours when a DC voltage having an electric field strength of 1.2 × 10 ⁴ V / mm at 85 ° C. is applied is short, and
The rate of change of the capacitance in the temperature range of 30 ° C. to + 85 ° C. is extremely large as −90% to + 95%, and the rate of change of the capacitance in the temperature range is −82% to +22.
%, The Y5V characteristics of the EIA standard cannot be satisfied, and there has been a problem that various kinds of capacitors such as a small-sized and large-capacity multilayer ceramic capacitor cannot be obtained.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object the purpose of having a high relative dielectric constant at room temperature of 15,000 or more and a thin plate having a thickness of 10 μm or less when fired at a low temperature of less than 1300 ° C. A sintered body can be obtained, an inexpensive internal electrode material can be used, and of course, the high temperature load life is as long as 40 hours or more, and the rate of change of capacitance in the temperature range of -30 ° C to + 85 ° C is reduced. An object of the present invention is to provide a dielectric ceramic composition applicable to various types of capacitors, including a small-sized and large-capacity multilayer ceramic capacitor satisfying the Y5V characteristic of -82% to + 22% or less.

[0011]

According to the dielectric ceramic composition of the present invention, when the composite oxide composed of barium strontium titanate is expressed as (Ba _1-x Sr _x ) TiO ₃ ,
Is 0.14 <x <0.20, and zinc oxide converted to ZnO is 0.1 to 0.
9 parts by weight of manganese compound in terms of MnO ₂
0.5 to 0.5 parts by weight, 0.1 to 1.3 parts by weight of a titanium compound in terms of TiO ₂ , 0.05 to 0.20 parts by weight of silicon dioxide in terms of SiO ₂ , Nd ₂ O ₃ , Sm ₂ O
_{3, Gd 2 O 3, La} 2 O 3, Pr 6 O 11, CeO 2,
The rare earth oxide in terms of at least one selected from Tb ₄ O ₇ and Eu ₂ O ₃ is one comprising 0.8 to 1.8 parts by weight.

[0012]

According to the dielectric porcelain composition of the present invention, zinc oxide and the like are contained in the dielectric porcelain composition mainly containing a composite oxide composed of barium strontium titanate, and the titanium compound is further contained in excess. Accordingly, the Y5V characteristic is satisfied even with a multilayer capacitor having a thickness of 10 μm or less while maintaining the relative dielectric constant at 15000 or more and enabling low-temperature firing at less than 1300 ° C. Will be able to do it.

As a result, the dielectric loss tan δ, which is the basic characteristics of the dielectric ceramic composition, is 1.0% or less, the insulation resistance IR is 1.0 × 10 ⁵ MΩ or more, and the electric field strength at 85 ° C. In a high-temperature load test in which a DC voltage of 1.2 × 10 ⁴ V / mm was applied, no failure occurred for 40 hours or more, and the firing temperature was less than 1300 ° C., which facilitated industrial production,
A dielectric ceramic composition applicable to various ceramic capacitors can be obtained. In particular, in the present invention, by containing 0.05 to 0.2 parts by weight of silicon dioxide in terms of SiO ₂ , a high-temperature electric field strength of 85 ° C. and a DC voltage of 1.2 × 10 ⁴ V / mm was applied. The failure is less likely to occur for 40 hours or more in the load test.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the dielectric ceramic composition of the present invention, when a composite oxide composed of barium strontium titanate is represented by (Ba _1-x Sr _x ) TiO ₃ , x is 0.14.
The main component is represented by <x <0.20.

In the present invention, (Ba _1-x Sr _x ) Ti
When expressed as O ₃ , the main component having x satisfying 0.14 <x <0.20 is a composite oxide composed of barium strontium titanate having a high purity of 99.0% or more. When expressed as Ba _1-x Sr _x ) TiO ₃ and the molar fraction x is 0.14 or less, the relative dielectric constant εr at room temperature
Is smaller than 15,000, and when the mole fraction x is 0.2 or more, the temperature characteristics of the capacitance do not satisfy the Y5V characteristics.

Therefore, the above Y5V characteristic is satisfied, and
In order to maintain a high relative dielectric constant of at least 00 and obtain various types of capacitors including small-sized and large-capacity multilayer capacitors, the value of x is specified to be more than 0.14 and less than 0.20, and in particular, x Is desirably in the range of 0.16 to 0.19.

The zinc oxide (ZnO) adjusts the firing temperature and the relative dielectric constant of the dielectric ceramic composition, and the content thereof is 100 parts by weight of the main component.
If the amount is less than 0.1 part by weight, the firing temperature becomes 1300 ° C. or higher, the relative dielectric constant εr at room temperature becomes less than 15,000, and the density of the fired sheet-like sintered body also becomes 5.7 g / c.
m ³ or less, which is out of the practical range. If it exceeds 0.9 parts by weight, the relative dielectric constant ε at room temperature becomes 15
000, the insulation resistance IR is greatly reduced, and the density of the fired sheet-like sintered body is also 5.7 g /
cm ³ or less, which is out of the practical range.
0.1 to 0.9 parts by weight, more preferably 0.1 to 0.9 parts by weight.
It will be 3 to 0.5 parts by weight.

Further, the manganese compound serves to improve, for example, the dielectric loss tan δ of the dielectric porcelain composition, and its content is converted to manganese oxide (MnO ₂ ) based on 100 parts by weight of the main component. If the amount is less than 0.1 part by weight, the dielectric loss tan δ becomes as large as 1% or more, and 0.5% or more.
If the amount exceeds the weight part, the insulation resistance IR is greatly reduced.

Therefore, the content of the manganese compound is manganese oxide (Mn) based on 100 parts by weight of the main component.
It is limited to 0.1 to 0.5 parts by weight in terms of O ₂ ), and particularly preferably 0.2 to 0.3 parts by weight.

On the other hand, the titanium compound is mainly contained for improving the sinterability of the dielectric ceramic composition, and the amount of the titanium compound is based on 100 parts by weight of the main component.
If it is less than 0.1 part by weight in terms of titanium oxide (TiO ₂ ), the sintering temperature is 1300 ° C. or higher, the density of the sintered sheet after sintering is as low as 5.7 g / cm ³ or less, and the dielectric loss is further reduced. Since tan δ is as large as 1% or more, which falls outside the practical range, and when it exceeds 1.3 parts by weight, the dielectric loss tan δ exceeds 1.0%. 0.3 parts by weight, more preferably in the range of 0.2 to 1.2 parts by weight.

The silicon dioxide (SiO ₂ )
It adjusts the crystal grain size of the dielectric porcelain composition, and the content is adjusted to 0.05 with respect to 100 parts by weight of the main component.
If the amount is less than parts by weight, the electric field intensity at 85 ° C. is 1.2 × 10 ⁴ V
In a high-temperature load test to which a DC voltage of / mm is applied, defects tend to occur within 40 hours, and the firing temperature exceeds 1300 ° C, which is outside the practical range. Since the ratio decreases to less than 15,000 and falls outside the practical range, the content is specified to be 0.05 to 0.20 parts by weight, and more preferably 0.10 to 0.15 parts by weight. Become.

The rare earth compound is added to improve the sinterability of the dielectric ceramic composition and to increase the relative dielectric constant. The content of the rare earth compound is 100 parts by weight of the main component. (Nd ₂ O ₃ , Sm ₂ O ₃ , Gd ₂ O ₃ , L
a ₂ O ₃ , Pr ₆ O ₁₁ , CeO ₂ , Tb ₄ O ₇ , Eu ₂
If it is less than 0.8 parts by weight in terms of O ₃ ), the relative dielectric constant is 15
If it exceeds 1.8 parts by weight, the density and insulation resistance IR of the sheet-shaped sintered body become low.
Since the content is out of the practical range, the content is 0.1.
8 to 1.8 parts by weight, more preferably 1.0 to
1.6 parts by weight.

The dielectric ceramic composition of the present invention is, for example, a composite oxide (Ba _1-x Sr _x ) Ti composed of barium titanate and strontium oxide (SrO) as starting materials.
Zinc oxide (ZnO), manganese compound, titanium compound, silicon dioxide (SiO ₂ ) per 100 parts by weight of O ₃
A predetermined amount of each powder of the rare earth element oxide is added, mixed and pulverized, and a binder is added thereto to produce a ceramic slurry. This is applied, for example, by a doctor blade method and then dried, and the operations of coating and drying are repeated to produce a molded body having a predetermined thickness.
It is obtained by firing at 200 to 1300 ° C.

[0024]

EXAMPLES Hereinafter, the dielectric ceramic composition of the present invention will be described in detail based on examples. In evaluating the dielectric ceramic composition of the present invention, barium titanate (Ba) was used as a starting material.
As a composite oxide composed of (TiO ₃ ) and strontium oxide (SrO), (Ba _{1 -x} Sr _x ) TiO ₃ having a mole fraction x of 0.14 to 0.20 and an average particle size of 1 μm or less.
-Based barium strontium titanate 100
Powders of zinc oxide (ZnO), a manganese compound, a titanium compound, silicon dioxide (SiO ₂ ) and a rare earth element oxide, a manganese compound was manganese oxide (MnO ₂ ), and a titanium compound was titanium oxide (TiO
₂ ), the rare earth element oxide is an oxide (Nd ₂ O ₃ , Sm
₂ O ₃ , Gd ₂ O ₃ , La ₂ O ₃ , Pr ₆ O ₁₁ , CeO
₂ , Tb ₄ O ₇ , Eu ₂ O ₃ ), and weighed so as to be in parts by weight shown in Tables 1 and _2.
The mixture was wet-mixed and pulverized for 20 hours with a ball mill using balls.

[0025]

[Table 1]

[0026]

[Table 2]

Next, a ceramic slurry is prepared by adding a binder comprising an organic binder and a medium to the mixed and pulverized product and stirring the mixture, and then defoaming the obtained ceramic slurry. A green sheet having a thickness of about 10 μm was formed on a film carrier by a method.

The obtained green sheet is 130 mm long,
The sheet is cut into a rectangular shape having a width of 100 mm.
After stacking 0 sheets, hot-pressing is performed at a temperature of 80 ° C. to produce a laminated body having a thickness of about 1 mm, and the laminated body is punched into a disc having a diameter of 20 mm. It was baked at the temperature for 2 hours.

Thereafter, electrodes were baked on both end surfaces of the disc-shaped sintered body using a silver paste to obtain samples for evaluation.

Using the evaluation sample thus obtained, first, the relative dielectric constant and the dielectric loss tan δ of the evaluation sample were measured under the measurement conditions of a reference temperature of 25 ° C., a frequency of 1.0 kHz, and a measurement voltage of 1.0 Vrms. , And a DC voltage of 50
The insulation resistance IR when V was applied for 1 minute was measured, and the density was measured by the Archimedes method.

From the above measurement results, the relative dielectric constant ε was 1500
If the value is less than 0, for example, a laminated ceramic capacitor cannot be miniaturized, so that 15,000 or more is considered good. If the dielectric loss tan δ is 1.0% or more, for example, it becomes difficult to make a capacitor chip, and so on. Less than 0% was evaluated as good. On the other hand, the insulation resistance IR is 1.0 × 10 ⁵
If it is less than MΩ, the multilayer ceramic capacitor does not satisfy the insulation resistance standard, resulting in poor insulation.
0 ⁵ MΩ or more was evaluated as good. In addition, the density is 5.7 g /
cm ³ or less indicates that these high-permittivity dielectric ceramic compositions are insufficiently fired, and a low-temperature firing at a temperature lower than 1300 ° C. does not provide a practical sintered body. 0.7 g / cm ³ or more was evaluated as good. The above results are shown in Tables 3 and 4.

[0032]

[Table 3]

[0033]

[Table 4]

As is clear from Tables 3 and 4, in Sample Nos. 1, 8, 14, 21, 36 and 37, the relative dielectric constant which greatly contributes to the miniaturization and large capacity of the multilayer ceramic capacitor is 14800 or less. Sample number 8, 2
1, 31, and 37 all have firing temperatures of 1320 ° C. or higher.

Sample Nos. 15, 20, 21, and 30 have a large dielectric loss of 1.18% or more.
In 4, 21, 37, and 44, the firing temperature is 1210 to 134.
Even when fired at a very high temperature of 0 ° C., the density is 5.70 g /
It is low at less than cm ³ , resulting in insufficient sintering. Further, Sample Nos. 14, 20, and 44 all had an insulation resistance of 1.0 × 1.
It is as low as less than 0 ^5.

On the other hand, the sample of the present invention has a high relative dielectric constant of 15300 or more and a firing temperature of 12
90 ° C or less, dielectric loss is 0.93% or less, density is 5.72 g / cm ³ or more, and insulation resistance is 1.5 × 10
⁵ MΩ or more satisfies all required characteristics.

Next, using a ceramic slurry prepared in the same manner as described above with the composition shown in Tables 1 and 2, a thickness of 10
A silver-palladium (Ag-
Pd) After screen-printing the electrodes in a predetermined shape using a paste for an internal electrode made of a powder, twenty green sheets on which the electrodes are printed are laminated, hot-pressed and integrated, cut into predetermined dimensions, and A chip was prepared.

The obtained green chip was placed in the air at 400
After decomposing the binder by completely decomposing the binder by holding at a temperature of 2 ° C. for 2 hours, Table 3 corresponding to each composition was used.
At the sintering temperature shown in FIG. 4, sintering was performed for 2 hours.

Thereafter, an external extraction electrode made of silver-palladium (Ag-Pd) is baked on the sintered chip,
An evaluation chip capacitor was manufactured.

The thickness of one dielectric layer of the above-mentioned chip capacitor for evaluation was 8 μm on average.

Using the evaluation chip capacitor thus obtained, first, a reference temperature of 25 ° C., a frequency of 1.0 kHz,
The capacitance and the dielectric loss of the evaluation chip capacitor were measured under the measurement condition of a measurement voltage of 1.0 Vrms, and the temperature of the capacitance at a temperature of −30 ° C. to + 85 ° C. with respect to the capacitance of the reference temperature of 25 ° C. The rate of change was measured. Further, a high-temperature load test was conducted in which a DC voltage of 1.2 × 10 ⁴ V / mm was applied at 85 ° C. This high-temperature load test was performed on 300 chip capacitors for evaluation, and the chip capacitor which was initially short-circuited was measured by measuring the time from the start of voltage application to the short-circuit.

In addition, the above-mentioned chip capacitors for evaluation were determined based on the relative dielectric constants shown in Tables 3 and 4 and the design capacitance calculated from the internal electrode area, the interval between the internal electrodes, the number of layers, and the like of the chip capacitors for evaluation after sintering. The ratio of the measured capacities of the samples was defined as the capacity ratio.

Further, five porcelain surfaces of the chip capacitor for evaluation were randomly selected, and these were photographed at 800 times magnification with a scanning electron microscope.
The crystal grains were randomly selected, the size was measured by the intercept method, the average value was determined, and the average particle size was determined. It was also confirmed whether abnormal grain growth occurred. In this determination of abnormal grain growth, it was determined that abnormal grain growth had occurred if particles having a size five times or more the average particle size were present.

From the above measurement results, the value of the capacitance was 2
If it is less than 00 nF, it is difficult to reduce the size of the multilayer ceramic capacitor, so that 200 nF or more was evaluated as good.

When the dielectric loss is 5.0% or more, it is not practical as a multilayer ceramic capacitor. Therefore, a value less than 5.0% is regarded as good.

Further, when the volume ratio is less than 70%, a sufficient capacity as a multilayer ceramic capacitor cannot be obtained, and miniaturization is difficult.

In the high-temperature load test, if a failure occurs in less than 40 hours, the standard of the multilayer ceramic capacitor is not satisfied. Therefore, it is determined that no failure occurs for 40 hours or more.

When the average particle size is 8.0 μm or more, the high-temperature load life of the multilayer ceramic capacitor having a single dielectric layer thickness of 10 μm or less does not satisfy the specification.
8.0 μm or less was regarded as good.

[0049]

[Table 5]

[0050]

[Table 6]

As is clear from Tables 5 and 6, Sample No. 7
In, the temperature characteristics are outside the standard, and even if the standard conforms, for example,
Sample numbers 1, 8, 21, 36, and 37 all have small electrostatic capacities of less than 200 nF, so that miniaturization of the multilayer ceramic capacitor cannot be realized. In addition, sample numbers 15, 2
In Examples 0 and 30, the dielectric loss is 5.9% or more, which is out of the practical range.

In sample No. 21, abnormal grain growth was observed, the capacity ratio was as small as less than 70%, and it was difficult to reduce the thickness of one dielectric layer to 10 μm or less.

Sample Nos. 21 and 31 had an average particle size of 8.0 μm.
m, and the high-temperature load test of the multilayer ceramic capacitor having a dielectric layer having a thickness of 10 μm or less does not satisfy the standard.

On the other hand, the chip capacitors of the sample numbers of the present invention all have high capacitances of 221 nF or more, low firing temperatures of 1290 ° C. or less, low dielectric losses of 4.5% or less, and low capacitance ratios. Has 84% or more,
It can be seen that no abnormal grain growth was observed.

[0055]

As described above, the dielectric porcelain composition of the present invention comprises a composite oxide composed of barium strontium titanate as a main component, and the main components are a rare earth element oxide, zinc oxide (ZnO), and manganese. compounds, titanium compounds, from the fact that further contain a SiO _2, Y5V EIA standard
While satisfying the characteristics, the relative dielectric constant is 15000 or more,
It has a long life at high temperature load, can be fired at a low temperature of less than 1300 ° C, and can obtain a dense and sheet-like sintered body with a thickness of 10 µm or less with a smooth surface. It is possible to obtain a dielectric ceramic composition applicable to various kinds of capacitors including a large-capacity multilayer ceramic capacitor.

Claims (1)

[Claims] (1) When a composite oxide composed of barium strontium titanate is represented by (Ba _1-x Sr _x ) TiO ₃ ,
With respect to 100 parts by weight of the main component represented by x being 0.14 <x <0.20, 0.1 to 0.9 parts by weight of zinc oxide converted to ZnO and 0 to manganese compound converted to MnO ₂ were added. 0.1 to 0.5 parts by weight, TiO ₂
0.1 to 1.3 parts by weight of titanium compound
O ₂ 0.05 to 0.20 parts by weight of silicon dioxide in terms _{of, Nd 2 O 3, Sm 2} O 3, Gd 2 O 3, La
₂ O ₃ , Pr ₆ O ₁₁ , CeO ₂ , Tb ₄ O ₇ and Eu
A dielectric ceramic composition comprising 0.8 to 1.8 parts by weight of a rare earth element oxide converted into at least one selected from ₂ O ₃ .