JPH03170370A - Dielectric porcelain composition and laminated ceramic capacitor using the same and production of laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain the title ceramic capacitor improved in dielectric constant by printing a CuO-contg. electrically conductive base on a dielectric green sheet of specified composition followed by lamination into a multilayer form which is then heat-treated in a mixed gas of H2 and N2 to reduce the CuO followed by sintering. CONSTITUTION:Pb(Mg1/3Nb2/3)O3, Ba(Ti1-xZrx)O3 and CuO are formulated at a specified ratio, calcinated and ground to prepare the objective dielectric porcelain composition of the formula (0.01<a<=3.0, 0<=b<0.15, 0.3<x<0.8). Thence, the presence composition as the inorganic component is mixed with an organic binder, plasticizer and solvent at a specified proportion into a slurry, which is then put to film formation into a dielectric green sheet. Thence, an electrically conductive paste prepared by kneading an organic vehicle with an inorganic component consisting mainly of CuO is put to screen printing on the green sheet to form an electrode pattern. The resulting green sheet is then laminated with other electrode-formed green sheet(s) made in a similar way followed by pressing into a multilayer form, which is then heat-treated to remove the binder contained, and the resulting multilayer form is further heat-treated in a mixed gas atmosphere of H2 and N2 to reduce the electrode material into Cu followed by roasting in a N2 atmosphere, thus obtaining the other objective laminated ceramic capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dielectric material used in ceramic capacitors, which can be sintered at a low temperature in a non-oxidizing atmosphere, and has dielectric properties in a wide temperature range. The present invention relates to a dielectric ceramic composition with a small temperature change in coefficient, a ceramic capacitor using this dielectric ceramic composition, and a method for manufacturing the ceramic capacitor.

2. Conventional technology The electrical properties required of dielectric materials used in ceramic capacitors include high dielectric constant, low dielectric loss, high insulation resistance, low temperature dependence of dielectric constant, and low dependence of dielectric constant on bias electric field. There is. Among these, the temperature dependence of the dielectric constant is defined in detail by JIS (Japanese Industrial Standards) and EIA (Electronic Industries Association) standards. For dielectric materials with a high dielectric constant, for example, the JIS standard requires Y-class B characteristics (capacitance change rate within ±10% from -25°C to +85°C), and the EIA standard requires X7R characteristics ( Capacitance change rate from -55°C to +125°C is ±15
% or less), and there are cases where a material with a small rate of change in capacity over a wide temperature range is required. Conventionally, dielectric materials with such good temperature characteristics have been mainly based on barium titanate, with a dielectric constant of about 1000 and annealing temperatures as high as 1300°C to 1400°C. Therefore, precious metals such as platinum and palladium must be used for the electrode material of ceramic capacitors, which increases costs.

In order to solve these problems with halium titanate-based materials, research has been carried out on various composite materials using perovskite-type dielectric materials containing lead ions (for example, JP-A-57
-57204, JP 5551759, JP 58-2
17462), and research on flattening the temperature characteristics of the dielectric constant by mixing perovskite dielectric materials containing multiple lead ions with different temperature characteristics (for example, Japanese Patent Application Laid-Open No. 592-037).
Publication No. 59, JJAP, vol. 24 (1985) Su
pplement pp. 427,429), and research on flattening the temperature characteristics of the dielectric constant by mixing a halium titanate-based material and a berovskite-type dielectric material containing lead ions (for example, Japanese Patent Laid-Open No. 156062/1983). Attempts are being made. The dielectric materials devised through these studies have a high dielectric constant and good temperature characteristics of the dielectric constant. Furthermore, since the firing temperature is relatively low, multilayer ceramic capacitors with internal electrodes made of relatively inexpensive silver-palladium alloys have also come to be manufactured.

Problems to be Solved by the Invention However, when dielectric materials such as those mentioned above are fired in a low oxygen partial pressure atmosphere, the insulation resistance of dielectric ceramics decreases significantly. The problem was that manufacturing the capacitor was difficult. In particular, since the firing temperature was 1000°C or higher, it was impossible to produce a ceramic vine capacitor using copper as the internal electrode.

In view of the above problems, the present invention provides a dielectric ceramic composition that can be sintered at low temperature in a non-oxidizing atmosphere and has a small temperature change in dielectric constant over a wide temperature range, and a dielectric ceramic composition that uses this dielectric ceramic composition. The present invention provides a ceramic capacitor and a method for manufacturing the ceramic capacitor.

Means for Solving the Problems In order to solve the above problems, the dielectric porcelain composite of the present invention has a high dielectric constant, low-temperature sintering in a non-oxidizing atmosphere, high insulation resistance, and small size in a wide temperature range. P b ( M g 1y3
N b zi3) O3 (hereinafter abbreviated as PMN), BaT
Solid solution of i○3 and BaZr○3 (hereinafter abbreviated as BTZ),
and copper oxide.

In addition, a process of making a green chip of a ceramic capacitor using the dielectric ceramic composition and copper oxide as a starting material for electrodes, a process of removing organic binder by heat treatment in air, and a process of removing internal electrodes by reduction treatment. We devised a manufacturing method for ceramic capacitors that consists of a process of metallizing copper, and a process of simultaneously firing the dielectric ceramic and electrodes in a neutral atmosphere, and by carefully examining the conditions of each process, we succeeded in converting copper into electrodes. This study was conducted in preparation for the production of Ceramic Q7 capacitors.

Function The present invention achieves high dielectric constant and excellent temperature dependence of dielectric constant by blending PMN, BTZ, and copper oxide in a predetermined ratio. This has been realized.

It is possible to obtain a high dielectric constant and an excellent temperature dependence of the dielectric constant by combining PMN and BTZ, two types of high permittivity dielectric materials with different temperature dependencies of the permittivity, and also By incorporating oxides, sufficient sintering at low temperatures is possible. Furthermore, the insulation resistance of this composite material did not decrease even when burned in a low-oxygen atmosphere, but rather the insulation resistance increased due to the high sinterability achieved.

Next, a method for manufacturing the ceramic capacitor of the present invention will be described. By using copper oxide as the starting material for the internal conductor, the organic binder can be sufficiently removed in air without worrying about shrinkage or oxidation of the internal conductor during binder removal, and in a hydrogen/nitrogen atmosphere after the binder removal process. By combining the reduction process at 100 mL and the annealing process in a nitrogen atmosphere, it has become possible to manufacture a laminated ceramic capacitor with copper internal electrodes that has excellent characteristics and reliability.

Example (Example 1) A single plate condenser will be described below as a first example of the present invention. To prepare the dielectric ceramic composition, industrial PbO, Mg○Nb205, BaC○3 are used as starting materials.
, Ti02, Zr02, and CuO were used. The PMN gathering was conducted as follows.

First, MgO and Nb205 were weighed and blended to form MgNb206, calcined in air at 950°C for 5 hours, and then crushed.
(M g +/3N b 2/3) 03, and in air at 900'C.
The mixture was calcined for a period of time and then crushed to obtain PMN powder.

This was done by combining BaTi○3 or by the following procedure.

Weigh and blend BaCO3 and Ti○2 at a molar ratio of 1:1,
It was calcined for 2 hours at a temperature of 300°C and then ground.

Ba (
For the combination of T i I-X ZrJ○3, BaT
It was carried out in the same manner as the i○3 meeting. That is, using BaCO3, Ti02 + Zr02 as raw materials, these were weighed and blended to form a predetermined composition, calcined in air, and then pulverized. During the synthesis of PMN and BaTiO3, blending and pulverization were carried out by a wet method using a short ball. PMNBaTiO3 or B a (T +
+-x Z rJ ○3 and Cu○ were wet mixed in a ball mill so as to achieve the desired mixing ratios shown in Table 1, and then dried.

Table 1 These mixtures were calcined in air at 800°C for 2 hours, and then ground in a ball mill. Drying was performed.

To the thus obtained dielectric ceramic composition powder, 5 parts by weight of polyvinyl alcohol was added as a binder, mixed, dried, and sized.

q Sorted porcelain composition powder at 1000 kg/a
It was shaped into pellets with a diameter of 10 mm and a thickness of 2.5 mm at a pressure of fl. The pellets were heated to about 700°C in air.
Dehindering was carried out at a temperature of 100.degree. C., followed by annealing at 950.degree. C. in nitrogen. Incidentally, the burning time was 1 hour for each, and the burning was performed by embedding Beresoto in the PMN powder to prevent lead from scattering. After sintering, the pellet shrinkage rate (S
After measuring hrinkage), apply A on both sides of the pellet.
The electrode paste was applied and completely dried in air at 120°C to produce a single-plate capacitor.

After that, for each sample, the dielectric constant (ε), dielectric loss (ta
nδ) and insulation resistance (R) were measured.

ε and tan δ at 25°C, IKHz. Measurements were performed under IVrms conditions. Also, R is 50V to the pellet.
A direct current bias of 100 mL was applied, and the resistance value was measured after 1 minute.

The results of these measurements are shown in Table 2.

Here, the capacitance-resistance product (CR product) is 10 expressed as the product of the capacitance and insulation resistance of the manufactured capacitor.

(The following is a blank space) l1 ○○○ ○○ ○○ 12 The compositions marked with O in Table 2 satisfy the compositional requirements of the present invention. As is clear from Table 2, the dielectric ceramic composition of the present invention can be sufficiently sintered at a low temperature of 1000°C or less in a low oxygen atmosphere, has a high dielectric constant (K≧3000), and has a high dielectric constant. Temperature change rate of temperature is also small l-55°C ~ +12
(±20% or less at 5°C), and has a sufficiently high resistivity for practical use. In Table 2, if the copper oxide content is low, sintering will not occur at temperatures below 1000"C, and the dielectric constant will be small, making it unsuitable. If it is too large, sufficient sinterability can be obtained, but the temperature characteristics will deteriorate and the dielectric loss will become too large, making it impractical.Also, the content of BaTi03 is particularly important for low-temperature sinterability and changes in dielectric constant due to temperature. If the content is low, the temperature dependence due to PMH is too strong, and if the content is high, the characteristics due to PMH cannot be obtained sufficiently.
The sinterability also decreases, making it unsuitable. Also. When a part of Ti in BaTi○3 is replaced with Zr, Ba(Ti, -xZ
rx) Since O3 has a Curie point on the lower temperature side than BaTiO3, it improves the temperature characteristics of the composition of the present invention in a high temperature range. However, if the amount of substitution of the Zr component is too large, the Curie point will shift too much to the low temperature side, so the temperature characteristics of the composition will be
In fact, it is not appropriate because it will make things worse. In this example, only the firing results in an N2 atmosphere were shown, but sufficient sintering was achieved by firing in air, and both the dielectric properties and temperature characteristics were good. In addition, although Cu○ (cupric oxide) was used as the copper oxide this time, even if Cu20 (cuprous oxide) is used, it will not be possible to produce the dielectric ceramic composition in the air. Cu in calcining
Similar results were obtained since it was oxidized to O.

Furthermore, the blending of PMN, copper oxide, and B a Ti O a is not limited to the present method; for example, copper oxide may be blended and calcined at the time of PMN blending without any problem.

(Example 2) Hereinafter, as a second example of the present invention, a multilayer ceramic capacitor having internal electrodes made of Cu will be described with reference to the drawings.

The dielectric powder was prepared using the method shown in Example 1, such as PMNCub,
A mixture of Ba (Tio.q Zro.+)O3, calcined and pulverized was used. The dielectric combination used or 0.
6 {P b(Mg+7z Nbzzz)Cuo. +
CL+. + 1'0.4Ba (Tio.q Zr
o. +) O3.

This dielectric material is an inorganic component, butyral resin is an organic binder, and di-n-butyl phthalate is a plasticizer.
Toluene was mixed as a solvent with the composition shown in the table below to form a slurry.

Non-a component 100 parts Butyral resin 10 parts D-n-butyl phthalate 1-5
40 parts toluene This slurry was formed into a film on an organic film by a doctor blade method to prepare dielectric Green Sea 1. The thickness of the green sheet after drying was about 3 olIm. Next, conductor pace 1.
was used as CuO powder inorganic substance, a vehicle in which ethyl cellulose was dissolved in terpineol was added, and the mixture was kneaded using three-stage rolls to obtain an appropriate viscosity. This conductive paste was screen printed on the green sheet to form an electrode pattern. Similarly, a desired number of electrode-shaped green sheets were stacked so that they could be used as counter electrodes, and a heat press was used to form 80
The laminate was pressed at a temperature and pressure of °C-1 20 kg/c+fl. Thereafter, it was cut into desired dimensions.

Next, this laminate was dehindered in air at 550° C. under the conditions shown in Table I. The dehindering temperature is determined in advance based on the results of thermal analysis of the organic binder, and should be at least the temperature at which the binder decomposes, but if heat treatment is performed at a higher temperature than necessary, unnecessary diffusion of the conductive material into the dielectric material may occur. Therefore, it is desirable to carry out the process at a temperature of about 600°C or less. In addition, as a result of this dehindering, the conductor paste containing copper oxide as a main component did not undergo a large volume change, and only the binder was scattered. After the binder has been completely removed, the laminate is heated with nitrogen gas for 1. ON/min, hydrogen gas 0.51
The second
The electrode material was reduced to Cu by heat treatment at a temperature of 400°C using the temperature raising and lowering conditions shown in the figure. After the reduction process, the laminate is heated to 950°C under the temperature raising and lowering conditions shown in Figure 3.
It was incinerated in a nitrogen atmosphere for 16 hours. Note that this calcination step was performed in the same tubular furnace as used in the reduction step. External electrodes (coated with metallic copper paste, dried, and baked in a nitrogen atmosphere at 600'C) on the multilayer ceramic capacitor fabricated as described above.
was installed and evaluated as a capacitor. The results are shown in Table 3.

Table 3 The dielectric constant of the obtained multilayer ceramic capacitor is approximately 320
0, the temperature change rate of dielectric constant was small, and the X7R characteristics of the ETA standard were satisfied. Further, as is clear from Table 3, the other properties were practically sufficient. Also,
When observing the internal cut surface, no cracks or delamination were observed, and the moisture resistance and electrode migration properties showed satisfactory results for practical use.

17 A cross-sectional view showing the structure of a multilayer ceramic capacitor manufactured by the manufacturing method of the present invention is shown in FIG. 1 in the diagram
2 is a dielectric material obtained according to the present invention, 2 is a copper internal electrode, and 3 is an external electrode.

As described above, the dielectric ceramic composite of the present invention can be sintered at low temperature in a low oxygen atmosphere, has a high dielectric constant and high insulation resistance, and in particular has a high dielectric constant over a wide temperature range. A multilayer ceramic capacitor with copper internal electrodes was able to be manufactured, which has excellent characteristics such as a low conversion rate, and also has practically sufficient characteristics by the method of manufacturing a multilayer ceramic capacitor of the present invention.

Effects of the Invention As described above, the dielectric ceramic composition of the present invention, which contains PMN, copper oxide, and BTZ as components, can be sufficiently sintered at an average temperature of 1000°C or less, and has a high dielectric constant. Porcelain with excellent insulation resistance and temperature characteristics is obtained.

Further, according to the method for manufacturing a multilayer ceramic capacitor of the present invention, the dielectric ceramic composition of the present invention is used as a dielectric material, and the steps of dehindering, reduction, and firing are performed under the above-mentioned configuration and conditions. , a highly reliable multilayer ceramic capacitor with copper electrodes having excellent mecrization properties can be obtained.

As described above, the dielectric ceramic composite of the present invention has excellent electrical properties and can be fired at low temperatures, so it is a dielectric material extremely suitable for mass production. The metallized capacitor is an extremely effective invention that can fully utilize the advantages of Cu, such as low conductive resistance, good migration resistance, and low cost.

[Brief explanation of the drawing]

Figures 1, 2, and 3 show the binder removal step and reduction step of the manufacturing method of the present invention, respectively. FIG. 4 is a graph showing an example of the temperature profile of the firing process, and FIG. 4 is a cross-sectional view showing the structure of a multilayer ceramic capacitor using a green sheet manufactured by the manufacturing method of the present invention. 1... Dielectric, 2... Internal electrode, 3...
...External electrode. 19 Hat/Scold

Claims (4)

[Claims] (1) General formula (1-x) {Pb(Mg_1_/_3Nb_2_/_3
)Cu_aO_3_+_a}・xBa(Ti_1_-_
A dielectric ceramic composition characterized in that, when expressed as bZr_b)O_3, it satisfies the following: 0.01<a≦0.30 0≦b<0.15 0.3<x<0.8. (2) A ceramic capacitor using the dielectric ceramic composition according to claim (1). (3) Using the dielectric ceramic composition according to claim (1),
A multilayer ceramic capacitor with u as an internal electrode. (4) A conductive paste consisting of an inorganic component mainly composed of CuO and an organic vehicle is printed on a dielectric green sheet made from the dielectric ceramic composition according to claim (1), and then the A process of laminating green sheets and printing the conductive paste on top of the green sheets is repeated to obtain a multilayer body, a process of heat treating this multilayer body in air, and then a process of heating the multilayer body in a mixed gas atmosphere of hydrogen and nitrogen. A method for manufacturing a ceramic capacitor, comprising the steps of: reducing CuO inside the multilayer body to metal Cu by heat treatment; and further sintering the reduced multilayer body in a nitrogen atmosphere.