JPS6114607B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a dielectric ceramic composition, and more particularly to a dielectric ceramic composition suitable as a dielectric of a multilayer ceramic capacitor. Conventional technology Conventionally, when manufacturing multilayer ceramic capacitors,
A conductive paste of noble metals such as platinum and palladium is printed on a dielectric raw sheet (green sheet) made of a dielectric ceramic composition, multiple sheets are stacked and pressed together, and then fired at a high temperature in an oxidizing atmosphere of 1300℃ or higher. Then, sintering of the dielectric ceramic composition and baking of the internal electrodes were performed simultaneously. As mentioned above, if a noble metal is used, the intended internal electrode can be obtained even if it is fired at a high temperature in an oxidizing atmosphere. However, platinum
Since precious metals such as palladium are expensive, multilayer ceramic capacitors have inevitably become expensive. In order to solve this problem, the applicant of the present invention proposed a non-oxidizing atmosphere,
We proposed a dielectric ceramic composition that can be sintered at 1200℃. According to this dielectric ceramic composition,
Internal electrodes can be formed by applying a conductive paste containing a base metal such as nickel as a main component and baking it. However, in a ceramic capacitor that uses this ceramic composition as a dielectric, the temperature change rate of capacitance is -25℃ specified by the JIS standard.
It was not possible to guarantee a range of ±10% at ~+85°C. Purpose of the Invention Therefore, the purpose of the present invention is to sinter at a temperature below 1200°C and to reduce the temperature change rate of capacitance by ±10.
% range. Structure of the Invention The present invention to achieve the above object is as follows:
Ba _k - _x M _x O _k TiO ₂ (where M is at least one metal of Mg and Zn, k is a numerical value in the range of 1.0 to 1.04, x is a numerical value in the range of 0.02 to 0.05) 100
Basic components in parts by weight and 25-50 mol% _Li2O and 50
The present invention relates to a dielectric ceramic composition obtained by firing a mixed material consisting of ~75 mol% SiO ₂ and 0.2 to 10.0 parts by weight of additional components. In addition, in the compositional formula showing the above-mentioned basic components, k-x, x, and k naturally indicate the number of atoms of each element. Effects of the invention According to the above invention, the following effects can be obtained. (a) Since this dielectric ceramic composition can be obtained at a firing temperature of 1200° C. or lower, energy consumption during firing can be reduced. Therefore, it is possible to reduce the cost of the dielectric ceramic composition. (b) Since sintering can be performed in a non-oxidizing atmosphere, it is possible to provide a multilayer ceramic capacitor having a base metal such as nickel as an internal electrode. (c) It is possible to provide a dielectric ceramic composition that has a high dielectric constant and a temperature change rate of capacitance within the range of ±10% from -25°C to +85°C. Examples Next, examples and comparative examples of the present invention will be described. k-x=0.95, Mg= of sample No. 1 in Table 1
0.03, Zn=0.02, x ₌ 0.05, k=1.0 determined according to Ba _0.95 M _{0.05 O 1.00} TiO ₂ , more specifically _:
In order to obtain the basic component consisting of Ba ₀ . ₉₅ Mg ₀ . _{03 Zn} 0 . ₀₂ O ₁ . ₀₀ TiO ₂ , BaCO ₃ , MgO,
ZzO, and TiO ₂ at 903.77g, 5.86g, 7.88g, and
385.93g of each was weighed and these raw materials were wet mixed for 15 hours. In addition, when the above raw material is expressed in molar parts without including impurities, it is BaCO ₃ 0.95 molar part,
0.03 mol part of MgO, 0.02 mol part of ZnO, and 1.0 mol part of TiO ₂ . Next, the above raw material mixture was dried at 150°C for 4 hours, pulverized and calcined at about 1200°C for 2 hours in the air to obtain a mixture of Ba ₀ . ₉₅ Mg ₀ . ₀₃ Zn ₀ . ₀₂ O ₁ . ₀₀ TiO ₂ A powder of the basic ingredients was obtained. On the other hand, in order to obtain the additive components of sample No. 1 in Table 1, 50.15 g (45 mol%) of Li ₂ CO ₃ and 49.85 g (55 mol%) of SiO ₂ were added.
(mol%) and add alcohol to this mixture.
Add 300cc and stir in a polyethylene pot for 10 hours using an alumina ball, then pre-calcinate in the air at 1000℃ for 2 hours, put this together with 300cc of water in an alumina pot, pulverize with an alumina ball for 15 hours, and then After that, dry at 150℃ for 4 hours to remove Li ₂ O45.
An additive component powder having a composition of 55 mol % of SiO ₂ was obtained. Next, 30g of the above additive component powder was added to 1000g of the basic component powder, and an organic binder consisting of an aqueous solution of acrylic acid ester polymer, glycerin, and condensed phosphate was added to the total weight of the basic component and additive component. 15% by weight (154.5 g) was added, and further 50% by weight (515 cc) of water was added, and these were placed in a ball mill and ground and mixed to prepare a slurry of porcelain raw material. Next, the above slurry is put into a vacuum deaerator to defoam, this slurry is put into a reverse roll coater, the thin film molding obtained from this is continuously received on a long polyester film, and the film is coated on the same film. Heat this to 100℃ and dry it.
A green porcelain sheet with a thickness of about 25μ was obtained. This sheet is long and is used by cutting it into 10cm squares. On the other hand, the conductive paste for internal electrodes has an average particle size of
10g of 1.5μ nickel powder and ethyl cellulose
A solution of 0.9 g dissolved in 9.1 g of butyl carbitol was placed in a stirrer and stirred for 10 hours. This conductive paste was printed on one side of the unsintered porcelain sheet through a screen having about 50 patterns of 14 mm in length and 7 mm in width, and then dried. Next, two unsintered porcelain sheets were laminated with the printed surfaces facing up. At this time, the adjacent upper and lower sheets were arranged so that their printed surfaces were shifted by about half in the longitudinal direction of the pattern. Further, four unsintered porcelain sheets each having a thickness of 60 μm were laminated on the upper and lower surfaces of this laminate. This laminate is then approximately
Approximately 40 tons of pressure was applied in the thickness direction at a temperature of 50°C to bond. Thereafter, this laminate was cut into a grid shape to obtain about 100 laminate chips. Next, this laminate was placed in a furnace capable of atmospheric firing, and the temperature was raised to 600°C at a rate of 100°C/h in an air atmosphere to sinter the organic binder. Thereafter, the atmosphere in the furnace was changed from air to an atmosphere containing 2% by volume of H ₂ + 98% by volume of N ₂ . Then, while maintaining the reducing atmosphere in the furnace as described above, the heating temperature of the laminate was increased from 600°C to the sintering temperature of 1110°C at a rate of 100°C/h and held for 3 hours. The temperature was lowered to 600°C at a rate of °C/h, the atmosphere was changed to air, and 600°C was maintained for 30 minutes for oxidation treatment, and then cooled to room temperature to produce a laminated sintered chip. Next, a conductive paste consisting of zinc, glass frit, and vehicle is applied to the side surface of the sintered chip where the electrodes are exposed, and dried.
Baking for 15 minutes at a temperature of °C to form a zinc electrode layer;
Furthermore, copper was deposited on this by electroless plating, and a Pb--Sn solder layer was further provided on this by electroplating to form a pair of external electrodes. As a result, as shown in FIG. 1, the dielectric ceramic layers 1, 2, 3, internal electrodes 4, 5, external electrodes 6,
A multilayer ceramic capacitor 10 consisting of 7 was obtained.
Note that the thickness of the dielectric ceramic layer 2 of this capacitor 10 is 0.02 mm, and the opposing area of the internal electrodes 4 and 5 is 5 mm.
×5mm= ^25mm2 . In addition, the porcelain layer 1 after sintering,
The compositions of Nos. 2 and 3 are substantially the same as the mixed composition of the basic components and additive components before sintering, and the basic components of the composite probskite structure (Ba ₀ . ₉₅ Mg ₀ . ₀₃ Zn ₀ . ₀₂ O _1.00 TiO ₂ ) between the crystal grains _.
It is considered that the additive components consisting of 45 mol% Li ₂ O and 55 mol% SiO ₂ were uniformly distributed. Next, we measured the electrical characteristics of the 10 capacitors 10 and found the average value. As shown in Table 2, the relative dielectric constant ε _s is 2690, tan δ is 1.3%, and resistivity ρ is 7.4 × 10 ⁶ MΩ・cm, capacitance change rate at -25℃ and +85℃ based on +20℃ capacitance △
C _-25 and △C ₊₈₅ were -9.1% and -8.7%. In addition, the temperature characteristics of capacitance based on the JIS standard are −25
When measured in the range of .degree. C. to +85.degree. C., the characteristic curve shown in FIG. 2 was obtained, and the temperature was within ±10%. Note that the electrical characteristics were measured in the following manner. (A) The relative permittivity ε _s is determined by measuring the capacitance under the conditions of temperature 20℃, frequency 1kHz, and voltage [effective value] 0.5V, and this measured value and the opposing area of electrodes 4 and 5 of 25mm ² and electrode 4 , 5 was calculated from the thickness of the porcelain layer 2 of 0.02 mm. (B) Dielectric loss tanδ (%) was measured under the same conditions as the relative dielectric constant. (C) Resistivity ρ (MΩ・cm) at a temperature of 20℃
After applying DC50V for 1 minute, the resistance value between the electrodes 6 and 7 was measured, and calculated based on this measured value and the dimensions. (D) Temperature characteristics of capacitance are measured by placing the sample in a thermostatic chamber at -25°C, 0°C, +20°C, +40°C, +60°C, and +85°C.
The capacitance was measured at each temperature of °C under the conditions of a frequency of 1 kHz and a voltage [effective value] of 0.5 V.
It was obtained by determining the rate of change of capacitance at each temperature when . Above, we have described the preparation method of sample No. 1 and its characteristics, but for samples No. 2 to 21, the compositions of the basic components and additive components, their ratios, and the firing temperature in a reducing atmosphere were also changed. Otherwise, a multilayer ceramic capacitor was manufactured in the same manner as Sample No. 1, and its electrical characteristics were measured in the same manner. Table 1 shows the composition of the basic components and additive components of each sample and the firing temperature during sintering, and Table 2 shows the electrical characteristics of each sample. Note that k-x, x, and k in the column of basic components in Table 1 indicate the number of atoms of each element in the composition formula, that is, the ratio of the number of atoms of each element when the number of Ti atoms is 1. Mg in the x column
and Zn indicate the content of M in the general formula, and Mg and Zn
The column shows the number of these atoms, and the total column shows the number of atoms.
The total value of Mg and Zn is shown. In Table 2, the temperature characteristics of capacitance are shown as capacitance change rates ΔC _-25 (%) and ΔC ₊₈₅ (%) at -25°C and +85°C.

【table】

【table】

【table】

[Table] In the present invention, the relative dielectric constant ε _s is 2000 or more, the dielectric loss tan δ is 2.5% or less, and the resistivity ρ is 1×10 ⁶ MΩ・
cm or more, and the temperature change rate △C of capacitance is within the range of ±10%. Therefore, sample No. 4,
5, 6, 8, 12, 16, 17, 19, and 21 are outside the scope of the present invention. Figure 2 shows only the temperature characteristics of sample No. 1.
Although the temperature characteristic curves of other samples are not shown and only △C _-25 and △C ₊₈₅ are shown in Table 2, the temperature characteristic curves of the samples belonging to the scope of the present invention are -25°C to +85°C.
The rate of change in capacitance ΔC in the range of is within the range of ±10%. Next, the reasons for limiting the composition will be described. When the amount of the additive component is zero, as shown in sample No. 8, a dense sintered body cannot be obtained even if the firing temperature is 1250°C, but as shown in sample No. 9,
When the amount added is 0.2 parts by weight per 100 parts by weight of the basic components, a sintered body having desired electrical properties can be obtained by firing at 1170°C. Therefore, the lower limit of the added components is 0.2 parts by weight. On the other hand, sample No. 12
As shown in , when the amount added is 12 parts by weight, tanδ
is 3.5%, which is worse than the target properties, but as shown in sample No. 14, when the amount added is 10 parts by weight, the target electrical properties can be obtained. Therefore, the upper limit of the amount added is 10 parts by weight. When the value of x is 0.01 as shown in sample Nos. 19 and 20, △C _-25 is -12.5% outside the range of ±10%,
-13.2%, but as shown in sample No. 18, when the value of x is 0.02, the target electrical characteristics can be obtained. Therefore, the lower limit of the value of x is 0.02.
On the other hand, as shown in Sample No. 5, when the value of x is 0.06, △C _-25 is -14.5%, which is outside the range of ±10%, but as shown in Samples No. 1 to 3, x When the value of is 0.05, the target electrical characteristics can be obtained. Therefore, the upper limit of the value of x is 0.05. In addition, both Mg and Zn of the M component are group metals and have almost the same function, so even when using only one of them, it is desirable that the value of x be in the range of 0.02 to 0.05. Furthermore, even when both are used, it is desirable that the value of x be in the range of 0.02 to 0.05. When the value of k is 0.98, as shown in sample No. 4, ρ becomes 6.2×10 ³ MΩ・cm, which is significantly lower than the target value, but as shown in sample No. 1, the value of k is 0.98. If the value is 1.00, the target electrical characteristics are obtained. Therefore, the lower limit of the value of k is 1.00. on the other hand,
When the value of k is 1.05, as shown in sample No. 16, a dense sintered body cannot be obtained, but when the value of k is 1.04, as shown in sample No. 20, the desired electrical characteristics are obtained. Therefore, the upper limit of the value of k is 1.04. As shown in sample No. 17, the additive component SiO ₂ is 45
In the case of mol%, tan δ is 3.2%, which is worse than the target value, but as shown in samples No. 9 and 18,
Target electrical properties are obtained when SiO ₂ is 50 mol %. Therefore, the lower limit for SiO ₂ is 50 mol%. On the other hand, when SiO ₂ is 80 mol% as shown in sample No. 6, a dense sintered body cannot be obtained, but when SiO ₂ is 75 mol% as shown in sample No. 2, a dense sintered body cannot be obtained. Target electrical characteristics can be obtained. Therefore, the upper limit for SiO ₂ is 75 mol%. Note that the range of LiO ₂ is necessarily 25 to 50 mol%. Modifications Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and, for example, the following modifications are possible. (a) A trace amount of a mineralizing agent such as MnO ₂ (preferably 0.05 to 0.1% by weight) may be added to the basic components to improve the sinterability, within a range that does not impede the object of the present invention. Further, other substances may be added as necessary. (b) The starting materials for obtaining the basic components and additive components may be other than those shown in the examples, such as BaO,
It may also be an oxide or hydroxide such as Li ₂ O or other compounds. (c) The oxidation temperature may be set to a temperature other than 600°C lower than the sintering temperature (preferably 1000°C or less).
That is, various changes can be made in consideration of the electrodes made of nickel or the like and the oxidation of the porcelain. (d) The firing temperature in a reducing atmosphere can be varied depending on the electrode material. (e) It is also applicable when sintering is performed in a neutral atmosphere. (f) Of course, it can also be applied to general ceramic capacitors other than multilayer ceramic capacitors.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a multilayer ceramic capacitor according to an embodiment of the present invention, and FIG. 2 is a diagram showing the temperature characteristics of capacitance of the ceramic capacitor of sample No. 1. 1, 2, 3...Porcelain layer, 4,5...Internal electrode, 6,
7...External electrode.

Claims (1)

[Claims] 1 Ba _k - _x M _x O _k TiO ₂ (where M is at least one metal of Mg and Zn, k is a numerical value in the range of 1.0 to 1.04, and x is in the range of 0.02 to 0.05. consisting of numerical values)
A dielectric ceramic composition obtained by firing a mixed material of 100 parts by weight of the basic component and 0.2 to 10.0 parts by weight of additive components consisting of 25 to 50 mol% Li ₂ O and 50 to 75 mol % SiO ₂ thing.