JPH0717442B2 - Method for producing barium titanate-based dielectric ceramic material and method for producing dielectric ceramic - Google Patents

Description

The present invention relates to a method for manufacturing a barium titanate-based dielectric ceramic material used for manufacturing a ceramic electronic component such as a monolithic ceramic capacitor, and a dielectric ceramic. The present invention relates to an improved manufacturing method, and more particularly to an improved method for obtaining a starting material.

[Conventional technology]

With the progress of surface mounting, various electronic parts such as multilayer ceramic capacitors are required to have a form of chip parts suitable for surface mounting, and the demand for chip parts is increasing. By the way, in the case of a chip-type electronic component, it is strongly required that the component itself is light, thin, short and small in order to downsize the device. However, when the chip-type electronic component is made lighter, thinner, shorter, and smaller, there is a problem that the thermal or mechanical strength is reduced.

Further, although speeding up of processing in electronic component mounting machines and soldering machines has been attempted, such speeding up of processing has also forced severe conditions on chip components. As a result, defects such as cracks are apt to occur due to thermal or mechanical shocks during mounting of components or soldering.

Therefore, conventionally, the thermal or mechanical characteristics have been improved by changing the composition of the ceramics, the firing conditions and the like. That is, the composition and firing conditions have been selected such that the thermal or mechanical strength does not decrease even when the thickness, the thickness and the size are reduced.

[Technical problem to be solved by the invention]

However, when the thermal or mechanical characteristics are improved by selecting the composition and firing conditions of the ceramics, in most cases, the original electrical performance such as the dielectric constant, the dielectric constant temperature characteristics, or the dielectric loss is not achieved. It had to deteriorate.

An object of the present invention is to provide a novel method for producing a dielectric ceramic material and a method for producing a dielectric ceramic in which thermal or mechanical characteristics are improved without deteriorating the electrical performance such as a dielectric constant. To provide.

[Means for solving technical problems]

The method for producing a barium titanate-based dielectric ceramic material according to the present invention is characterized in that a mixed material obtained by mixing first and second barites having different compositions is used as a starting material, as described below. .

That is, the first barite containing Al ₂ O ₃ at 0.2% by weight or less, SiO ₂ at less than 1.3% by weight, and BaSO ₄ at 96% by weight or more and less than 100% by weight, and Al ₂ O ₃ at 0.2% by weight or less, the SiO ₂ 1.30 wt% to 3.
Prepare a mixed material by mixing a second barite containing less than 8 wt% and BaSO ₄ in the range of 96 wt% to less than 100 wt% so that the first barite exceeds 50 wt% of the whole. To do.

After that, the above mixed material was used as a raw material and BaCO was used for chemical treatment.
Generates ₃ .

Next, BaCO ₃ is mixed with TiO ₂ and baked to obtain BaT
Obtain an iO ₃ -based dielectric ceramic material.

Preferably, after obtaining the BaTiO ₃ powder by pulverizing the BaTiO _3, BaTiO ₃ 85-90 wt%, CaSnO ₃ 5-10 wt%, Ca
Preparing a composition containing 1 to 5% by weight of ZrO ₃ and less than 3% by weight of one or more trace additives selected from the group consisting of alcal earth oxides, transition metal oxides and mineralizers, and calcining Thus, a barium titanate-based dielectric ceramic is obtained.

Further, in another preferable example, BaTiO ₃ is added in an amount of 93 to 98% by weight and Nb.
1 to 2% by weight of ₂ O ₅ , 0.5 to 1% by weight of Nd ₂ O ₃ and 1 or more kinds of trace additives selected from the group consisting of alkaline earth oxides, transition metal oxides and mineralizers. Similarly, a dielectric porcelain is obtained by preparing a composition containing less than 1% and firing it. In the above, as the alkaline earth oxide, for example, Sr, Mg, etc., as the transition metal oxide, for example, Co, Mn, etc. Further, as the mineralizer, for example, Al ₂ O ₃ , Si, etc.
O ₂ or the like is used.

[Action]

BaCO _3, the raw material for barium titanate-based dielectric porcelain,
Conventionally, it is produced by using, as a raw material, one kind of barite produced in Japan mainly containing BaSO ₄ having the composition shown as the second barite in Table 1 described later. That is, when barite is mixed with coke and fired, BaSO ₄ + 2C → BaS + 2CO ₂ (1) BaS is generated by the reaction of the formula (1). Next, water and carbon dioxide were added to obtain BaCO ₃ by the formula (2).

BaS + H ₂ O + CO ₂ → BaCO ₃ + H ₂ S (2) Then, BaCO ₃ obtained as above is mixed with TiO ₂ and fired to obtain a BaTiO ₃ -based dielectric ceramic. Was manufactured.

On the other hand, the composition of barite varies considerably depending on the place of mining. The present inventor conducted various experiments using barite having various compositions as described above, and the first barite and the second barite having the above-mentioned compositions were It was found that a dielectric porcelain having excellent thermal or mechanical strength and little deterioration in electrical performance can be obtained by using a mixed material mixed so as to exceed 50% by weight of the whole as a raw material, and the present invention is achieved. Came to.

Since barite is used as the BaSO ₄ raw material, if the BaS obtained by the formula (1) is pure, the generated BaCO ₃ will be irrespective of the composition of the raw barite. It seems that there should be no difference.

However, as will be apparent from the examples described below, if a dielectric ceramic material is obtained by using a mixed material in which the first and second barites are mixed, thermal and mechanical properties of the obtained dielectric ceramic will be obtained. The characteristics are improved. This is not necessarily clear, but the content of Al ₂ O ₃ and SiO ₂ in barite for obtaining BaCO ₃ is lower than that of the conventional barite produced in Japan. It is thought to be due to.

[Explanation of Examples]

Example 1 The first barite having the composition shown in Table 1 and the second barite are contained in an amount of 60,50,40% by weight based on the total weight of the first barite.
Three types of mixed materials included were prepared.

By mixing each of the above mixed materials as a raw material with coke and firing the mixture, BaS is obtained according to the formula (1).
Was generated. Next, add water and carbon dioxide gas to form BaCO ₃
Got

For each BaCO ₃ obtained from different mixed materials,
BaTiO ₃ was obtained by mixing ₂ in equimolar ratio and firing at a temperature of 1150 ° C.

Each BaTiO ₃ obtained as described above was crushed and crushed Ba
A laminated ceramic capacitor was prepared using TiO ₃ by the following procedure.

BaTiO ₃ to 87 wt%, CaSnO ₃ to 8 wt%, CaZrO ₃ 3 wt%, and MgO as a minor additive, SiO ₂ and MnO ₂ in a total of 2
An organic binder was added to the composition containing wt% to form a ceramic green sheet having a thickness of about 30 μm by the doctor blade method.

On one surface of the ceramic green sheet, an internal electrode paste mainly composed of silver-palladium was printed, an appropriate number of layers were laminated, pressure-bonded in the thickness direction, then cut, and fired in air at a temperature of 1200 to 1300 ° C.

External electrodes were printed and baked on the obtained fired body to obtain a monolithic ceramic capacitor. Chip size is 2.0 ×
It is 1.25 × 0.8 mm and the design capacitance is 0.022 μF.

For comparison, after using only one of barites 2 to 4 in Table 1 to prepare BaTiO ₃ in the same manner as above, a monolithic ceramic capacitor was obtained by the same procedure. It was

The multilayer ceramic capacitor obtained as described above was evaluated by the following thermal spalling test and impact mechanical strength test.

The thermal spalling test uses 400 samples of 50 samples each.
It was immersed in a solder bath at ℃, 450 ℃ and 500 ℃ at a speed of 25 mm / sec, and whether or not cracks were generated in the sample was observed by a microscope (including broken ones). The number of cracks generated is shown in Table 2 below.

From Table 2, barite mixed materials included within the scope of the present invention
It can be seen that, when X and Y are used, cracks are less likely to occur, as compared with the case where a single kind of barite is used and the case where a mixed material Z other than the present invention is used as in the conventional case.

The impact mechanical strength test is carried out with 5 and 1 for 50 samples each.
It was performed by dropping 3 g of a metal body from a height of 0, 20 cm and observing with a microscope whether cracks were generated in the sample. Table 3 shows the number of cracks.

It can be seen from Table 3 that even in the impact mechanical strength test, the sample using the barite mixed material falling within the scope of the present invention has less cracks than the conventional product.

Example 2 A mixture of the first barite and the second barite shown in Table 1 was mixed, and the first barite was contained in a plurality of 70,50,30% by weight. A barite mixed material was obtained. Using a plurality of barite mixed materials as described above, in the same manner as in Example 1,
A BaTiO ₃ dielectric ceramic was prepared.

The resulting BaTiO ₃ ceramic was ground to a powder raw material, the BaTiO ₃
97% by weight, Nb ₂ O ₅ 1.5% by weight, Nd ₂ O ₃ 0.7% by weight, and a total of 0.8% by weight of the additives Co ₂ O ₃ , MnO and SiO ₂ . Using the composition obtained, Example 1
A monolithic ceramic capacitor was manufactured by the same method as in. The size of the manufactured ceramic capacitor is 2.0 × 1.2.
The size is 5 × 0.7 mm, and the capacity is 0.01 μF.

For comparison, any one of barites Nos. 1 to 4 in Table 1
BaTiO ₃ powder was prepared using only seeds, and a multilayer ceramic capacitor obtained in the same manner using the BaTiO ₃ powder was prepared as a comparative example.

A thermal spalling test and an impact mechanical strength test were performed in the same procedure as in Example 1 for the monolithic ceramic capacitor using the barite mixed material and the monolithic ceramic capacitor of the comparative example. The number of cracks
The results are shown in Tables 5 and 6.

As is clear from Tables 5 and 6, in the mixed materials O and P corresponding to the range of the present invention, the heat treatment is less than that in the examples using the barite mixed material Q outside the present invention and the comparative examples. It can be seen that the mechanical and mechanical strength is effectively increased.

〔The invention's effect〕

As described above, according to the present invention, the first barite containing Al ₂ O ₃ at 0.2 wt% or less, SiO ₂ at less than 1.30 wt%, and BaSO ₄ at 96 wt% or less and less than 100 wt%, The second barite containing Al ₂ O _{3 in an amount} of 0.2 wt% or less, SiO ₂ in the range of 1.30 wt% or more and less than 3.8 wt%, and BaSO ₄ in the range of 96 wt% or less and less than 100 wt% includes the first barite. Since BaCO ₃ system dielectric porcelain is manufactured using a mixed material that is mixed so as to exceed 50% by weight of the whole, it has excellent thermal and mechanical properties without lowering electrical performance such as permittivity. It becomes possible to obtain body porcelain. Therefore, by simply selecting the raw material, it becomes possible to obtain a ceramic electronic component having excellent thermal and mechanical properties that could not be realized by conventional products.

Claims (3)

[Claims] 1. Al ₂ O ₃ is 0.2% by weight or less, and SiO ₂ is 1.3% by weight.
First barite containing less than 96 wt% and less than 100 wt% of BaSO ₄ , Al ₂ O ₃ of 0.2 wt% or less, SiO ₂ of 1.3 wt% or more and less than 3.8,
Preparing a mixed material in which a second barite containing BaSO _{4 in an amount} of 96 wt% or more and less than 100 wt% is mixed so that the first barite exceeds 50 wt% of the whole, and the mixed material generating a BaCO ₃ by chemical processes as raw materials, BaTiO ₃ by firing the BaCO ₃ was mixed with TiO ₂
And a step of obtaining a barium titanate-based dielectric ceramic material. Wherein BaTiO ₃ by grinding BaTiO ₃ as set forth in claim 1
After obtaining a powder, BaTiO ₃ powder 85-90 wt%, CaSnO ₃ 5-10 wt%, CaZrO ₃ 1-5 wt%, and alkaline earth oxides, transition metal oxides and lead content agents A method for producing a barium titanate-based dielectric ceramic, comprising a step of preparing a composition containing less than 3% by weight of one or more trace additives selected from the group consisting of: and firing. Wherein BaTiO ₃ by grinding BaTiO ₃ as set forth in claim 1
After obtaining the powder, 93 to 98% by weight of BaTiO ₃ powder, 1 to 2% by weight of Nb ₂ O ₅ , 0.5 to 1% by weight of Nd ₂ O ₃ and alkaline earth oxides, transition metal oxides and minerals are obtained. A method for producing a barium titanate-based dielectric porcelain, comprising a step of preparing a composition containing less than 1% by weight of one or more trace additives selected from the group consisting of agents and firing the composition.