JPH02242523A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To make the dielectric porcelain composition one with high dielectric constant, high insulation resistance and high insulation breakdown voltage, being excellent in quality Q, and with a small temperature coefficient of electrostatic capacity by making the composition contain tantalum oxide as auxiliary component against main components that the composition contains in such a manner that when an expression is given as xBaO-y[(TiO2)(1-m)(ZrO2)m]-zRe2O3, (x), (y) and (z) are in a specific mole ratio range. CONSTITUTION:The dielectric porcelain composition is made to contain tantalum oxide as auxiliary component by 0.1 to 10 parts by weight in Ta2O5 (against 100 parts by weight of main components that the composition contains in such a manner that when an expression is given as xBao-y[(TiO2)(1-m)(ZrO2)m]-z Re2-O3(x+y+z=1.00; 0.001<=m<=0.200; Re2O3 is at least one kind of oxide of rare earth material selected from among La2O3, Rr2O11/3, Nd2O3 and Sm2O3), (x), (y) and (z) are in a mole ratio range surrounded by points (a) to (f) in the figure. The composition thereby has its dielectric constant, insulation resistance, insulation breakdown voltage enhanced, its quality Q made excellent and its temperature coefficient of electrostatic capacity reduced.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention has high dielectric constant, insulation resistance, and dielectric breakdown voltage, excellent quality Q, and small capacitance temperature coefficient, and is suitable for use in multilayer ceramic capacitors. , prevents a decrease in capacitance and quality Q when the thickness of the internal electrode is reduced,
The present invention relates to a dielectric ceramic composition that can reduce variations in capacitance and quality Q.

Conventional technology Conventionally, the dielectric constant and insulation resistance are high, and the quality Q is excellent.
The following systems are known as dielectric ceramic compositions with small capacitance temperature coefficients.

・B2O-TiO2-Nd2O'3 system ・B2O-TiO2-8m203 system Problems to be solved by the invention However, these compositions, for example, 0.11BaOO,6
A dielectric material with a composition ratio of 8T i 02-0.21Nd20a was used, and the palladium internal electrode thickness was 4 μm.
, dielectric thickness 12 μm, internal electrode overlap dimensions 1, 2
When a multilayer ceramic capacitor with a laminated structure of mm X 0, 7 mm, and 19 dielectric layers is manufactured, the average value of capacitance: 724 pF, and the average value of goodness Q: 8
700, average value of capacitance temperature coefficient: NN35pp/°
Average value of C2 insulation resistance: 6. OX 1012Ω, average value of dielectric breakdown strength: 117 kv/mm, which is not a satisfactory value in terms of insulation resistance and dielectric breakdown strength. In addition, since the crystal grain size is large (1 to 5 μm), when the porosity in the element body increases, the electric field strength applied to each crystal grain becomes large (and the dielectric breakdown strength is also not a satisfactory value). .

In addition, in order to reduce the cost of multilayer ceramic capacitors and to prevent the occurrence of delamination, which is a structural defect inside the element body, the thickness of the palladium internal electrode was increased to 4 μm.
When thinning from m to 2 μm, a dielectric material with the above composition ratio is used, and the dielectric thickness and internal electrode claw dimensions are as shown in -.
The average value of capacitance of a multilayer ceramic capacitor with a laminated structure with a number of dielectric layers is small at 610 pF (and the variation in capacitance becomes large at 256 to 713 pF.Furthermore, the average value of quality Q is 4000). There was a problem in that as the quality level Q decreased, the variation in the goodness level Q increased from 600 to 8800.

Means for Solving the Problems In order to solve these problems, the present invention provides a formula xBa
O--y [(T i 02) B-m) (Z
ro 2) m] When expressed as ZRe203 (However,
e2O3 is La2O3, Pr20th/3. Nd2O3
, Sm2O3. ), x, y, z are not shown below and each point a.

Containing tantalum oxide as a subcomponent in an amount of 0.1 to 10 parts by weight in terms of Ta205 to 100 parts by weight of the main component consisting of the molar ratio range surrounded by b, c, d, e, f. This paper proposes a dielectric ceramic composition with characteristics.

FIG. 1 is a ternary diagram showing the composition range of the main components of the composition according to the present invention, and the reason for limiting the composition range of the main components will be explained with reference to FIG. That is, sintering is extremely difficult in region A. Furthermore, in region B, the quality Q decreases, making it impractical. Furthermore, in regions C and D, the capacitance temperature coefficient becomes too large on the negative side, making it impractical.

In region E, the temperature coefficient of capacitance shifts to a positive direction, but the dielectric constant is too small to be practical. Also, R
e2O3 as La2O3,P r20+w3゜Nd2O3
, SmpO3, La2O3,P r2
0+1/3. It is possible to shift the capacitance temperature coefficient in the positive direction without significantly lowering the dielectric constant in the order of Nd2O3 and Sm2O3, and La2O3, P r20+
+, z3. The capacitance temperature coefficient can be adjusted by using one type or a combination of Nd2O3 and Sm2O3.

In addition, by replacing TiO2 with ZrO2, it is possible to reduce the crystal grain size and increase the dielectric breakdown strength without significantly changing the dielectric constant, quality Q, temperature coefficient of capacitance, and insulation resistance. However, if the substitution rate m is less than 0.001, there is no substitution effect (on the other hand, if it exceeds 0.200, the dielectric constant, goodness Q, and insulation resistance decrease.

Figure 2 is a graph showing the effect of the inclusion of the sub-component element A205 on the main component of the composition according to the present invention in terms of the characteristics of a multilayer ceramic capacitor. explain. As shown in Figure 2, by containing Goa205, insulation resistance,
It has the effect of improving dielectric breakdown strength, increasing capacitance and quality Q, and reducing variations in capacitance and quality Q.

Insulation resistance and dielectric breakdown strength are improved by the inclusion of Ta205, but the content of Ta205 is the main component 10
If the amount is less than 0.1 part by weight, the capacitance and quality Q are low, and the capacitance and quality Q vary widely, so it was excluded from the scope of the present invention. -, way, T a
If the content of 205 exceeds 10.0 parts by weight based on the main component, the quality Q and insulation resistance will decrease, and the temperature coefficient of capacitance will increase toward the minus side, making it impractical.

The present invention further provides the above composition with at least one oxide selected from manguin, zinc, iron and silicon oxides, MnO2 and ZnO, respectively.

A configuration can be adopted in which 0.05 to 1.00 parts by weight of the metal is added to 100 parts by weight of the main component and the subcomponents combined in terms of Fe2O3 and SiO2. These additives have the effect of improving the sinterability of porcelain, but if the amount added is less than 0.05 parts by weight, there is no effect. It becomes irrelevant.

Example The present invention will be explained below using specific examples.

(Example 1) Chemically high-purity BaCO3TlO2, Z is used as a starting material.
rO2, La2O3, P r6ON d 203. S
The m203 and Ta205 powders were weighed to have the composition ratios shown in Table 1 below, put into a rubber-lined ball mill equipped with agate balls together with pure water, wet mixed, and then dehydrated and dried. This dry powder was placed in a high alumina crucible and calcined in air at 1100°C for 2 hours. This calcined powder was put into a rubber-lined ball mill equipped with agate balls together with pure water, wet-pulverized, and then dehydrated and dried.

After adding an organic binder to this dry powder and making it homogeneous, it was sized through a 32-mesh sieve, and was molded to a diameter of 15 m using a mold and a hydraulic press at a molding pressure of 1 ton/cut'.
m, thickness 0.4 mm. Next, the molded disk was placed in an alumina sheath covered with zirconia powder, and dielectric porcelain having the composition ratio shown in Table 1 below was obtained in air.

The thickness and diameter of the dielectric porcelain disk thus obtained were measured, and the sample for measuring the dielectric constant, goodness of quality Q, and capacitance temperature was prepared by baking silver electrodes on both sides of the dielectric porcelain disk. , the sample for measuring insulation resistance and dielectric breakdown strength was placed inside the outer circumference of the dielectric ceramic disk. A part without a silver electrode was provided with a width of mm, and a silver electrode was baked onto it. Then, the dielectric constant, goodness Q,
The capacitance temperature coefficient is measured using YHP Digital 1. Using CR meter model 4275Δ, measuring temperature 20°C2
Measurement voltage 1, OV rms, measurement frequency 1.
It was determined by measurement at MHz. Note that the capacitance temperature coefficient is 20°C.

The capacitance at 85° C. was measured and calculated using the following formula.

TC= (C-Co)/CoX 1/65X 106T
C・Capacitance temperature coefficient (ppm/°C) CO Capacitance at 20°C (pF) C, Capacitance at 85°C (+) F) Further, the dielectric constant was determined from the following formula.

K=143.8 Measurement voltage was 50V using HR meter model 4329A.

D, C: Determined from measurements with a measurement time of 1 minute.

The dielectric breakdown strength was determined by using a PH335 type 13 high voltage power supply made by Kikusui Electronics Co., Ltd., placing the sample in silicone oil, and dividing the dielectric breakdown voltage determined by the voltage increase rate of 5 QV/sec by the dielectric thickness. , the dielectric breakdown strength per 1 mm.

] 0 Further, the crystal grain size was determined by optical microscope observation at a magnification of 400.

The test conditions are also shown in Table 1, and the test results are shown in Table 2 below.
Shown in the table.

(Left below) (Example 2) Starting materials include chemically highly purified BaCO3TiO2, Z
rO2, La2O3, PreO+Nd2O3, Sm2O
3, Ta205. Mn 02. Z n O.

Fe2O3 and Si○2 powders were weighed to have the composition ratio shown in Table 3 below, and then treated in the same manner as in Example 1 to produce dielectric porcelain having the composition ratio shown in Table 3. Obtained.

The testing methods for these samples were the same as in Example 1, the test conditions are also shown in Table 3, and the test results are shown in Table 4 below.

(Left below) (Example 3) Chemically highly purified BaC03T i02 was used as the starting material.
．． Z r○2. La2O3,Pr60+I.

Using Nd2O3, Sm2O3 and Ta2's powder, the main component is 0.1]]BaO-0.68(Ti02)o
9(Z ro2)o, +] -0,21 Contained 0.0.05, 0.10, 0.50°1.00.5.00, 10.00, 12.00 wt% of Ta205 with respect to Nd203 A calcined pulverized powder is produced in the same manner as in Example 1.

However, Ta205 content 0.0.05゜12.00w
t% is outside the scope of this invention and is 0.100, 0.5
00, 1.00, 5.00°10.00wt% are within the scope of this invention.

An organic binder, a plasticizer 1 dispersant, and an organic solvent were added to this calcined and pulverized powder, and mixed in a polyethylene pot equipped with alumina balls to prepare a slurry. After mixing, 3
It was filtered using a 00 mesh nylon cloth. The slurry after filtration was formed into a sheet using a doctor blade on a polyester film that had been subjected to mold release treatment so that the dielectric thickness after sintering was 12 μm. Next, 10 sheets peeled from the polyester film were laminated on a support base. On top of this, the internal electrode thickness after sintering Shoei Chemical's back electrode palladium paste ML-3724 is 2 μm.
Screen printed and dried. A sheet peeled from a polyester film was laminated on top of this.

On top of this, the internal electrode overlap dimension after sintering is 1,2 m.
The internal electrode palladium paste was printed by shifting the printing position so that m X 0 was 7 mm, and after drying, one sheet peeled from the polyester film was laminated. These operations were repeated until the number of dielectric layers reached 19. On top of this, sheet 1 peeled from the polyester film
0 sheets were laminated. After sintering this laminate, it was cut into a laminate ceramic capacitor having a laminate structure in which the internal electrode overlap dimensions were 1.2 mm x O57nvn, the dielectric thickness was 12 μm, and the number of dielectric layers was 19. The cut sample was placed in an alumina pod covered with zirconia powder and heated at 5°C/h from room temperature to 350°C in air.
The temperature was raised to 100°C/1]r from 350'C]7, and after firing at 1270°C for 2 hours, the temperature was lowered to room temperature at 000C/hr.

Next, the fired sample was placed in a polyethylene pot with water-resistant sandpaper pasted on the inside, along with pure water, and the polyethylene pot was rotated to polish the surface of the fired sample to fully expose the internal electrode portion that will be connected to the external electrode. Ta. This sample was taken out of the polyethylene pot, dried, and then a silver external electrode was baked onto the exposed portion of the internal electrode to make it electrically conductive with the internal electrode, producing a multilayer ceramic capacitor.

The capacitance, quality Q, temperature coefficient of capacitance, insulation resistance, and dielectric breakdown strength of these samples were determined by measurements under the same conditions as in Example 1. In addition, the laminated structure was confirmed by approximately 172 mm in the length and width directions of the laminated ceramic capacitor.
The internal electrode overlap dimension is a polished cross section with a magnification of 100. The dielectric thickness and the internal electrode thickness were determined by optical microscope observation at a magnification of 400.

The measurement results are shown in FIG.

Note that the method for manufacturing dielectric ceramics in the examples is based on Ba
C0:+, ZrO2, TiO2, La20:+Pr60
++, Nd2O3, Sm2O3, Ta2'5゜MnO2
, Zn○, Fe2O3 and Sigh were used, but
The method is not limited to this method, but BaO, Z r
O2, T i 02゜La2O3, P r60++, N
d2O3, Sm2O3゜Ta 205. MnO2,Z
Characteristics comparable to those of the examples can be obtained even when using compounds such as nO, Fe2O3 and 5i(h).

Further, even if the main component is roughened and calcined and subcomponents are added, properties comparable to those of the examples can be obtained.

Effects of the Invention As described above, according to the present invention, the dielectric constant, insulation resistance, and dielectric breakdown voltage are high, the quality level Q is low, the capacitance temperature coefficient is small, and when used in a multilayer ceramic capacitor, This prevents a decrease in capacitance and quality Q when the thickness of the internal electrode is made thinner, and reduces the variation in capacitance and quality Q. It is possible to reduce costs and prevent the occurrence of delamination, which is an internal structural defect.Also, because the dielectric breakdown voltage is high, the thickness of the dielectric layer can be reduced, making it possible to make the element smaller and increase the capacity. be.

Furthermore, the addition of manganese, zinc, iron and silicon oxides allows the firing temperature to be lowered.

[Brief explanation of drawings]

FIG. 1 is a ternary diagram explaining the composition range of the main components of the composition according to the present invention, and FIG. 2 is a ternary diagram explaining the composition range of the main components according to the present invention.
8aO-0,68[(TiO2)o,5(ZrO2)0
．． 1] Subcomponent element a20 for 0.21Nd203
5, the dielectric thickness was 212 μm. Internal electrode overlap dimensions: 1, 2 mm x 0, 7
2 is a graph showing the electrical characteristics of a multilayer ceramic capacitor having a laminated structure with 19 dielectric layers.

Claims (2)

[Claims] (1) General formula xBaO-y[(TiO_2)_(_1_-_m_)(
ZrO_2)_m]-zRe_2O_3 (where x+y+z=1.00, 0.001≦m≦0.2
00, Re_2O_3 is La_2O_3, Pr_2O
An oxide of at least one rare earth element selected from _1_1_/_3, Nd_2O_3, and Sm_2O_3. ), x, y, z are the points a, b, c, d, e,
Ta_2O_5 tantalum oxide as a subcomponent to 100 parts by weight of the main component having a molar ratio range surrounded by f.
A dielectric ceramic composition characterized in that it contains 0.1 to 10 parts by weight calculated as . ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (2) At least one or more selected from manganese, zinc, iron, and silicon oxides are added to 100 parts by weight of the main component and subcomponent, respectively, to MnO_2 and ZnO.
, 0.05 in terms of Fe_2O_3 and SiO_2
The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition is added in an amount of 1.00 parts by weight.