JPH10270284A - Manufacture of dielectric ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing dielectric ceramic material for manufacturing a small-sized multilayer ceramic capacitor of low cost, wherein generation of a segregation phase is restrained, short-circuiting failures do not exist, characteristics deterioration in time is small, electrostatic capacity is large and reliability is high by improving dispersion of subcomponent to main component of dielectric ceramic material, and making composition uniform. SOLUTION: One or at least two kinds from among BaTiO3 , CaTiO3 , SrTiO3 or BaZrO3 are made to be the main component. Component containing at least three kinds of compounds selected out of the respective compounds of Ba, Ca, Sr, Mg, Si, Cr, Y, V, Mn, W, Zr is used as subcomponents, to be mixed in the above main component. Dielectric ceramic material wherein the above subcomponent of at least 0.2 wt.% and at most 10.0 wt.% is contained in the main component is manufactured. After the subcomponent is made into fine powder by water grinding, granule of the subcomponent is made by freezing and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a dielectric ceramic material for forming a dielectric green sheet of a multilayer ceramic capacitor having internal electrodes.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a laminated ceramic capacitor, a dielectric ceramic material mainly composed of BaTiO ₃ or the like is formed in a sheet shape, a conductor paste serving as an internal electrode is applied on the surface thereof, and a laminated pressure bonding is performed. And bake,
A method for making a multilayer ceramic capacitor is generally known.

[0003] The dielectric ceramic material for a multilayer ceramic capacitor usually has the following components:
For the purpose of adjusting temperature characteristics and improving various characteristics such as reliability, several types of elements are added as subcomponents.

[0004] Such subcomponents include Ba, Ca, Sr,
It consists of three or more compounds of Mg, Si, Cr, Y, V, Mn, W, and Zr.
As shown in (C), three or more of these compounds are prepared (step (a)), wet-mixed and pulverized (step (b)), and then dried with hot air (step (c)) to obtain particles. It has gained.
The subcomponent thus obtained is mixed with the main component to form the sheet.

In recent years, with the rapid miniaturization and high density of information equipment and communication equipment, multilayer ceramic capacitors are also required to be ultra-small and have high capacitance in order to be used for a wide range of electronic circuits. It is coming.

However, the conventional multilayer ceramic capacitor requires a dielectric interlayer thickness of 10 μm to 20 μm between the internal electrodes due to the properties of the dielectric ceramic material.
It was very difficult to achieve a small size and high capacitance. Further, if the interlayer thickness of the dielectric is forcibly set to 10 μm or less, conduction failure occurs between the internal electrodes, and the yield is extremely poor. High capacitance, high reliability and low cost were hindered from commercialization.

In Japanese Patent Application Laid-Open No. 5-124857, for the purpose of improving the dielectric breakdown voltage, the subcomponents are previously mixed and pulverized, and pulverized to an average particle size of 0.2 μm to 1.0 μm.
A production method of mixing and dispersing with a main component has been proposed.

[0008]

When the dielectric ceramic material is formed, the sub-components are mixed and pulverized, and when subjected to hot-air drying, the coagulation of the sub-component particles is large and the average particle size of the sub-components is large. Several μm, not completely dispersed in the main component phase
A degree of segregation phase (a phase in which a specific component element forms a different aggregate from other main parts and becomes non-uniform with the main part) or a heterogeneous phase (a phase in which the crystal structure is different. Exists). The SEM diagram (secondary electron image) and the COMP diagram (characteristic X-ray image) by the second stage electron microscope from the bottom of Reference Material 1 correspond to the same part, and appear in a horizontal stripe shape. Those are the internal electrodes of the capacitor. In the SEM diagram, the black dots indicate the segregation layer, and the white dots indicate the cavities.

Reference material 2 shows the characteristic X-rays from the internal electrodes and the base in the electron microscope image, which are displayed on a computer screen by color-coding the elements for each element. The second, third, and fourth elements are represented by Ba, S,
The amount of i becomes small, while the amount of Ti and Zn partially increases, and a segregation phase appears. As described above, in the conventional dielectric ceramic material, the average particle size of the sub-components increases due to the aggregation of the sub-components, and a segregation phase or a heterogeneous phase is present. There is a problem that the characteristics are rapidly deteriorated in the high temperature accelerated life test.

As described in JP-A-5-124857, even when the average particle size of the sub-components is 0.2 μm to 1.0 μm, the thickness between the internal electrodes cannot be reduced to 10 μm or less. Even if a multilayer ceramic capacitor having a thickness of about 10 μm is forcibly commercialized, there are problems such as a rapid decrease in yield due to the short circuit described above and a rapid deterioration in characteristics in a high-temperature accelerated life test.

An object of the present invention is to improve the dispersibility of subcomponents and to make the composition uniform so as to suppress the generation of a segregation phase and reduce the dielectric interlayer thickness to 1 in view of the above-mentioned problems of the prior art.
Provided is a method for manufacturing a dielectric ceramic material for producing a multilayer ceramic capacitor having a small size, high capacitance, low cost, and high reliability, with no short-circuit failure, little deterioration of characteristics due to aging even when the thickness is 0 μm or less. It is in.

[0012]

In order to achieve the above object, the present invention provides BaTiO ₃ , CaTiO ₃ , SrTiO
_3, or a one or mainly of two or more of the BaZrO _3, as an accessory component to be mixed into the main component, B
a, Ca, Sr, Mg, Si, Cr, Y, V, Mn,
A compound containing at least three or more compounds selected from the respective compounds of W and Zr (compounds are composed of oxides, carbides or hydroxides) is used, and the sub-component is 0.2 wt% with respect to the main component. When producing a dielectric ceramic material containing 10.0 wt% or less as described above, the auxiliary component is wet-pulverized, pulverized, and then freeze-dried to produce a subcomponent granule. ).

[0013] The present invention also relates to the present invention, wherein:
The average particle size is 0.001 μm to 0.15 μm by heat melting treatment with a plasma flame of 00 ° C. to 20,000 ° C.
Wherein the freeze-drying is performed after the ultrafine particles are wet-pulverized (claim 2).

In the present invention, the particles of the plural types of subcomponents are mixed, heat-treated at 600 ° C. to 1600 ° C., and finely pulverized to an average particle diameter of 0.05 μm to 1.0 μm by wet pulverization. The freeze-drying is performed (claim 3).

In the present invention, BaTi as a main component is used.
O ₃ and BaZrO ₃ are high dielectric constant materials,
O ₃ and SrTiO ₃ are the main components of a temperature-compensated low dielectric constant material. 0.2% by weight of various components
The content of 10.0 wt% or less is necessary for imparting reduction resistance during firing of the dielectric material, adjusting dielectric characteristics and temperature characteristics, and improving the reliability of a high-temperature accelerated life test and the like. . In the present invention, after the auxiliary component is wet-pulverized and freeze-dried, the state of fine particles having a small average particle size can be maintained without causing aggregation.

In the present invention, if the fine particles of the auxiliary component are obtained by the plasma method, ultrafine particles having an average primary particle size of 0.001 μm to 0.15 μm of the auxiliary component can be easily obtained. Even if the particles are fine particles, aggregation of the particles can be prevented by removing water by freeze-drying.

By mixing and dispersing the subcomponent composed of fine particles obtained as described above in the main component, the subcomponent is uniformly dispersed in the main component, and the composition is uniform and almost no generation of a heterogeneous phase or a segregation phase occurs. A dielectric ceramic material for producing a multilayer ceramic capacitor having less heterogeneous phase and segregated phase, no sharp increase in short-circuit failure, and no deterioration in characteristics even in a high-temperature accelerated life test can be obtained.

The average particle size of the sub-components is 0.001 μm
Even in the case of, short defect improvement can be seen,
When the thickness is less than 0.001 μm, it becomes expensive and tends to aggregate during wet mixing and drying. When the average particle size of the sub-components exceeds 0.15 μm, an increase in short-circuit failure is observed, and the average particle size is preferably 0.15 μm or less.

In the present invention, if three or more types of sub-components are treated by the plasma method, the properties of the sub-components will be described in
As described in JP-A-124857, the individual particles are not made up of individual components by pulverization, but can be made into an amorphous state in which three or more components are mixed in individual particles by plasma treatment, The desired properties are easily obtained,
Characteristics are stable.

[0020] In the present invention, the roasting method is used.
By subjecting the subcomponents to heat treatment at 0 ° C. or more and 1600 ° C. or less, some or all of the plurality of types of subcomponents can be dispersed at the atomic level by melting or sintering. If the roasting temperature is lower than 600 ° C., the three types of subcomponents are not melted or sintered. On the other hand, if the roasting temperature exceeds 1600 ° C., the grain growth or melting becomes remarkable, so that the particle size increases, and it becomes difficult to atomize the subcomponents. ° C
It is preferable to set the following.

In the case of the roasting method, the average particle size is set at 0.1.
It is difficult to make it less than 05. On the other hand, when the thickness exceeds 1.0 μm, the short-circuit failure or the like easily occurs. Therefore, in the case of the roasting method, the average particle size is 0.05 μm or more,
Fine particles of 1.0 μm or less are mixed and dispersed with the main component. When the average particle size is 0.05 μm or more and 1.0 μm or less, even if the thickness between the dielectric layers is less than 10 μm, particularly 1 μm to 8 μm, there is no sharp increase in short-circuit failure, and the high-temperature accelerated life is greatly increased. To improve.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] FIG. 1A is a process chart showing an embodiment of a method for producing a dielectric ceramic material according to the present invention. First, the granules of the auxiliary components are BaCO ₃ , CaCO ₃ , SiO ₂ , Y
₂ O ₃ , MgCO ₃ , Cr ₂ O ₃ , V ₂ O ₅ , and ZrO ₂ are each weighed and mixed (step (a)), and wet-mixed and pulverized with a ball mill using an organic solvent as a dispersion medium (step (a)). b)), after dehydration / drying with hot air (step (c)), to obtain granules having an average particle size of 0.5 μm to 2.0 μm.

Next, a plasma processing apparatus having a schematic structure as shown in FIG. 2 (in the figure, 1 is a plasma torch, 2 is a granule inlet, 3 is a gas inlet, 4 is a cooling furnace, 5 is a collecting furnace ), Granules are introduced from the inlet 2 above the apparatus, and argon gas and nitrogen gas are introduced into the plasma torch 1 from the gas inlet 3 and plasma generated by high-frequency heating to 10,000 ° C. The gas stream of the subcomponent gasified through the flame is rapidly cooled in the cooling furnace 4 so that the average particle size of the primary particles is 0.001 μm or more and 0.1 mm.
An ultrafine particle having a particle size of 20 μm or less was obtained as an auxiliary component (step (d)). Ultrafine particles having an average particle size of 0.001 to 0.20 μm were obtained by changing the cooling rate of the gasified subcomponent. 0.001, 0.01,
0.03, 0.05, 0.10, 0.15, 0.20μ
Thus, subcomponent granules having an average particle size of m were obtained.

Further, the auxiliary component was wet-mixed and pulverized with a ball mill using pure water as a dispersion medium (step (e)).

Next, the mud made in the step e is put into a metal vat, the mud is frozen at -10 ° C., and then the temperature is reduced to 0 ° C. to make a vacuum to sublimate the water, ie, freeze-dry. Then, granules in which the particles of the auxiliary component compound were not aggregated were produced (step (f)).

A multilayer ceramic capacitor was manufactured by the steps shown in FIG. 3 using the sub-components manufactured as described above. First, 3 wt% of the above sub-components is added to a main component material of BaTiO ₃ having an average particle size of 0.7 μm, and an organic solvent is used as a dispersion medium in a ball mill, and an organic binder and a plasticizer are added. To obtain a slurry made of a ceramic material (step (a)).

Using the slurry, a sheet was formed by a doctor blade method to obtain a dielectric ceramic green sheet and dried (steps (b) and (c)).

A conductive paste is printed on one surface of the obtained green sheet on a plurality of internal electrode patterns (step (d)), dried (step (e)), and then a plurality of green sheets are laminated and pressed (step (d)). (F)) After that, cutting (step (g)), a multilayer body of the multilayer ceramic capacitor was produced.

This laminate is heated at 320 ° C. in air for 5 hours.
After heating for a time to remove the binder, the mixture is heated to about 1200 ° C. in a reducing gas flow having a volume ratio of H ₂ / N ₂ of 3/100.
For 2 hours to produce a sintered body (step (h)).

Next, in order to compensate for the oxygen deficient by the above-mentioned calcination, calcination is performed at 800 ° C. for 4 hours in an air atmosphere to re-oxidize, and Cu paste is applied to both ends of the sintered body and baked. Terminal electrodes were formed (step (i)) to obtain a multilayer ceramic capacitor.

The internal electrodes of the multilayer ceramic capacitor had a thickness of 1.5 μm, the thickness of the dielectric layer between the internal electrodes was 5 μm, and the number of superposed dielectric layers was 210.
The external dimensions of the product are 3.2mm x 1.6mm x 1.2mm
It is.

Example 2 On the other hand, instead of the plasma treatment in the step (d), the powder having an average particle size of 0.5 μm to 2.0 μm was placed in a roasting furnace in an air atmosphere for 700 hours.
After heating at 0 ° C., the mixture was rapidly cooled, and then this subcomponent was wet-pulverized with water as a dispersion medium in a ball mill to make the average particle size 0.1 μm. A minor component was obtained. In the subsequent steps, a multilayer ceramic capacitor having the same dimensions as in Example 1 was manufactured.

Example 3 A multilayer ceramic capacitor having the same dimensions as in Example 2 except that the average particle size was set to 1.0 μm and the other steps were the same as in Example 2 was produced.

[Conventional example] As a conventional example, BaCO ₃ , CaC
O ₃ , SiO ₂ , Y ₂ O ₃ , MgCO ₃ , Cr ₂ O ₃ , V
₂ O ₅ and ZrO ₂ were each weighed and prepared, and mixed and pulverized with a ball mill using an organic solvent as a dispersion medium. Then, the dried mud powder was dried with hot air using a batch furnace to produce granules. The granules made have an average particle size of 1.5 μm
２．０2.0 μm. The granules are directly transferred to the Ba
A multi-layer ceramic capacitor having the same dimensions was manufactured by mixing with the main component composed of TiO ₃ and the other steps were the same as in the above embodiment.

[Short Failure Rate Test and High-Temperature Accelerated Life Test] The ceramic capacitors according to the above embodiment and the conventional example were evaluated by a withstand voltage failure rate (short failure rate) and a high-temperature accelerated life test. Withstand voltage failure, apply DC 10V,
Those having an insulation resistance of 100 MΩ or less after 30 seconds were regarded as defective. The high-temperature accelerated life test was performed by continuously applying an ambient temperature of 200 ° C. and a DC voltage of 25 V. Table 1 shows the results. FIG. 4 shows time on the horizontal axis and the occurrence rate of short-circuit failure on the vertical axis.

[0035]

[Table 1]

Example 1 in Table 1 shows the results of a test of 100 primary particles having an average particle size of the auxiliary component (average particle size after freeze-drying) of 0.03 μm. Also,
Example 2 in Table 1 shows that the average particle size of the primary particles of the sub-component is 0.1
It is the result of having tested about 100 micrometer thing. The conventional examples in Table 1 are the results of testing 100 samples with an average particle size of 1.0 μm.

In addition, Example 1 in FIG. 4 shows the test results for those having an average particle size of the primary particles of the sub-component of 0.03 μm, and Example 2 in FIG. 4 shows the average particle size of the primary particles of the sub-component. FIG. 4 shows the test results for those having a diameter of 0.1 μm, and the conventional example in FIG. 4 shows the test results for those having an average primary particle diameter of 1.0 μm of the subcomponent.

As is clear from Table 1, according to Examples 1 to 3, the short-circuit defect rate is reduced to about 1/240 to 1/24 or less. In addition, the life in a high temperature load test is 14 ~
It is longer than 240 times. Further, Embodiment 1 of FIG.
In the case of freeze-drying after plasma treatment as described above, if the average particle size is reduced, good results can be obtained in a high-temperature accelerated life test and a short-circuit failure test.

In the first embodiment employing the plasma method,
When the average particle size is 0.15 μm, the average particle size is 0.2 μm
The short-circuit failure rate is reduced to about 1/6,
Accelerated life has doubled. The average particle size is 0.001μ.
In the range of m to 0.15 μm, the incidence of short-circuit failure decreases as the average particle diameter decreases, and the accelerated life also increases. On the other hand, if the average particle size is less than 0.001 μm, aggregation is likely to occur and production becomes difficult. Therefore, the average particle size of the primary particles is preferably 0.001 μm to 0.15 μm.

Reference Material 3 shows the dispersion state of the particles in the case of the conventional method, Example 1, and Example 2, respectively. In Reference Material 3, the plasma method shown on the right end shows the concentration distribution of the element after mixing the sub-component having an average particle size of 0.03 μm as the main component in Example 1 above. In addition, what shows about the roasting method shows the concentration distribution of Ca and Si elements after mixing the sub-component having an average particle size of 0.1 μm obtained by the above-mentioned roasting method with the main component. . The conventional method (STD) is obtained by mixing the sub-component shown in the above-mentioned conventional example with the main component. As is apparent from Reference Material 3, when the plasma method is used, each element of the subcomponent is amorphous mixed with each element, so that each element is uniformly present as a whole particle aggregate. be able to. Further, in the case of the roasting method, since each particle of the subcomponent is present as a compound of each element, it is possible to obtain a state in which each element is uniformly distributed over the entire particle aggregate, similarly to the plasma method. In each case, a finer and more uniform component distribution can be obtained as compared with the case of the conventional method, and short-circuit defects can be reduced and characteristics can be stabilized.

Reference material 4 shows that the average particle size of the primary particles in Example 1 was 0.03 μm (BET value 30 m
4 is a COMP photograph by an electron microscope when the thickness of the dielectric layer between the internal electrodes is changed to 7 μm, 4 μm, and 2 μm using the ² / g) subcomponent.

[0042] [Example 4] Unlike the above embodiment, the composition _{is, (Ba w Ca x) (} Ti y Zr z) O 3 + (MnCO 3 +
Y ₂ O ₃ + V ₂ O ₅ + WO ₃ + SiO ₂ ) and (Ba
_w Ca _x ) (Ti _y Zr _z ) O ₃ as a main component, and as subcomponents, BaO, CaO, MnCO ₃ , Y ₂ O ₃ , V ₂ O ₅ , W
After weighing and blending O ₃ and SiO ₂ , respectively, the average particle diameter is 0.5 μm by the same process as the plasma treatment as described above.
give subcomponents of m, said as the main component (Ba _w Ca _x)
(Ti _y Zr _z ) O ₃ , and a short-circuit failure test and a high-temperature accelerated life test were performed in the same manner as described above. As a result, the same effect of reducing short-circuit failures and characteristic deterioration as in the above example was obtained.

[0043]

According to the present invention, BaTiO ₃ , CaTi
A dielectric ceramic material containing one or more of O ₃ , SrTiO ₃ , or BaZrO ₃ as a main component and a sub-component of 0.2 wt% or more and 10.0 wt% or less with respect to the main component. In the production method, when producing the sub-components, after wet pulverization, freeze drying is performed to obtain ultrafine particles, so that aggregation of the sub-components can be prevented, and the state of the ultrafine particles is maintained. can do. For this reason, by improving the dispersibility of the sub-components to the main component and making the composition uniform, the generation of segregation phase is suppressed, and even if the dielectric interlayer thickness is 10 μm or less, there is no short-circuit failure, and aging does not occur. It is possible to manufacture a small-sized multilayer ceramic capacitor with small characteristic deterioration, high capacitance, low cost and high reliability.

According to the second aspect, after blending the auxiliary component particles,
The average particle size is 0.001 μm or more by plasma method,
0.15 μm or less ultrafine particles were obtained.
The effect of claim 1 is further promoted. In addition, since part or all of the sub-components can be made amorphous, the element distribution can be made uniform throughout the dielectric ceramic material, and desired characteristics can be easily obtained, and a capacitor having stable characteristics can be obtained. it can.

According to the third aspect, the blended sub-components are
It is roasted at 0 ° C. to 1600 ° C. and wet-pulverized to 0.
By preventing agglomeration by freeze-drying at 05 μm, prevention of short-circuit failure and extension of life can be achieved. In addition, by roasting, a part or all of the three or more types of subcomponents become compounds with each other, so that the element distribution can be uniformed as a whole of the dielectric ceramic material, desired characteristics can be easily obtained, and capacitors having stable characteristics can be obtained. Can be obtained.

[Brief description of the drawings]

1 (A) and 1 (B) are each a diagram showing a manufacturing process of a sub-component in each embodiment of the method for manufacturing a dielectric ceramic material according to the present invention, and FIG. 1 (C) is a diagram showing a conventional process of manufacturing a sub-component.

FIG. 2 is a schematic configuration diagram of an apparatus for performing a plasma method used in the present invention.

FIG. 3 is a manufacturing process diagram for obtaining a multilayer ceramic capacitor using the subcomponent obtained by the manufacturing method of the present invention.

FIG. 4 is a diagram showing the results of a high-temperature accelerated life test in an example of the present invention and a conventional example.

[Explanation of symbols]

1: plasma torch, 2: granule inlet, 3: gas inlet, 4: cooling furnace, 5: collection furnace

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 35/46 E 35/48 D

Claims (3)

[Claims] 1. BaTiO ₃ , CaTiO ₃ , SrTiO ₃
Alternatively, one or more of BaZrO ₃ is used as a main component, and Ba, Ca, Sr,
Mg, Si, Cr, Y, V, Mn, W, and Zr are used, each containing at least three or more compounds selected from the compounds. 1
When producing a dielectric ceramic material containing 0.0 wt% or less, the sub-component is wet-pulverized and pulverized, and then freeze-dried to produce a granule of the sub-component, the production of the dielectric ceramic material. Method. 2. The method according to claim 1, wherein the particles of the auxiliary component are subjected to a heating and melting treatment with a plasma flame at 2,000 ° C. to 20,000 ° C. so as to have an average particle size of 0.1.
A method for producing a dielectric ceramic material, comprising forming ultrafine particles of 001 μm to 0.15 μm, wet-grinding the ultrafine particles, and freeze-drying. 3. The method according to claim 1, wherein the particles of the plurality of types of subcomponents are mixed,
Heat treated at 00 ° C, average particle size is 0.05μm ~ 1.0μm by wet grinding
A method for producing a dielectric ceramic material, comprising the steps of: