JPH10130050A - Preparation of dielectric material for low-temperature sintering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate fluctuations in characteristics varying with every production lot even if a firing temp. and the compsn. ratio between a perform material and a glass material are kept constant, to easily maintain the specific dielectric constant of the final products constant and to avert the occurrence of the time and cost losses in production stages. SOLUTION: Small batch powder processing treatment to weigh a small amt. from a large amt. of a calcined high-dielectric constant materials of a BaO-TiO2 -Nd2 O3 system which is the prefrom material, to take out the preform material for a precedent test, to mix this material with the separately weighed glass material and to pulverize the mixture is executed and, thereafter, a sample is manufactured and the processing test to measure the specific dielectric constant is carried out. The amt. of the Bi2 O3 to be added is determined within the range of <=1vol.% according to the component of the specific dielectric constant lowered from its target value. A large batch treatment to weight the remaining preform material and glass material so as to attain the same component ratio as the compsn. ratio of the precedent test, to add and mix the prescribed amt. of the Bi2 O3 to and with this material and the pulverize the same is executed. There is no need for adding the Bi2 O3 if the specific dielectric constant nearly coincides with the target value in the precedent test.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a dielectric material for low-temperature sintering, which can make the relative dielectric constant of a large batch processed product substantially close to a target value despite the characteristic fluctuation of the base material. It is. More specifically, in the present invention, a calcined BaO—TiO ₂ —Nd ₂ O ₃ -based high dielectric constant material and a glass material are weighed at a fixed ratio, a preliminary test is performed, and a target of relative dielectric constant is measured. The amount of decrease from the value is determined, and an appropriate amount of Bi ₂ O ₃ is added in the range of 1% by volume or less, mixed, and pulverized so that the relative dielectric constant of the product becomes almost the target value. The present invention relates to a method for preparing a dielectric material for low-temperature sintering that can be adjusted. This technique is useful, for example, for manufacturing a high dielectric constant dielectric porcelain used for a resonator having a laminated structure in a microwave band.

[0002]

2. Description of the Related Art Dielectric filters are used in various mobile communication devices using microwaves, such as mobile phones. Along with the demand for downsizing of devices, further downsizing of dielectric filters is required, and stop line filters having a laminated structure are being developed in some parts. This kind of laminated dielectric filter is manufactured through a process of laminating a number of green sheets (unfired sheets) made of dielectric ceramics, integrating them under pressure, and cutting and firing. At this time, the internal electrodes are screen-printed on the green sheet, and the external electrodes are also formed by screen printing. Therefore, a dielectric material having a high dielectric constant that sinters at a low temperature at which the electrode pattern of the electrode material does not collapse is required. Also, if such a dielectric material for low-temperature sintering is developed, there is a possibility that dielectric filters having various other structures can be developed.

As a method of sintering a dielectric material at a low temperature, a technique of adding a glass material has been developed. For example, S
A method of manufacturing a low-temperature sintered dielectric porcelain using an iO ₂ -B ₂ O ₃ -BaO-based glass material has been proposed (Japanese Patent Application Laid-Open No. Hei 7 (1994)).
-69719). In general, the advantage of adding a glass material is that low-temperature sintering becomes possible, but on the other hand, there is a problem that the addition of the glass material lowers the relative dielectric constant. Another problem with low-temperature sintering is that the relative density of the sintered product is low, and the relative dielectric constant of the sintered dielectric ceramic fluctuates.

[0004] As a technique that can solve such a problem,
The present inventors have proposed Ba containing Bi ₂ O ₃ and Al ₂ O _3.
Against O-TiO ₂ -Nd ₂ O ₃ based high dielectric constant material,
It proposed a method of manufacturing a low-temperature sintering dielectric ceramic pulverized and mixed by adding glass material _{ZnO-B 2 O 3 -SiO 2} -Al 2 O 3 system (Japanese Patent Application No. 7-66979). As a result, sufficient dielectric properties can be obtained even at a firing temperature of 1000 ° C. or lower. Therefore, it is possible to mold a dielectric component including an internal electrode material (Ag, Au, Ag-Pd, etc.) and fire the same as it is. A high performance laminated stop line type dielectric filter can be manufactured.

[0005]

However, a low-temperature sintering dielectric material in which a glass material is added to a base material (calcined BaO—TiO ₂ —Nd ₂ O ₃ based high dielectric constant material)
There is a problem that the relative dielectric constant changes considerably for each production lot due to variations in the characteristics of the base material and subtle variations in the production conditions, which hinders stable product production. B
BaO-TiO ₂ -N containing i ₂ O ₃ and Al ₂ O ₃
against d ₂ O ₃ based high dielectric constant material, ZnO-B ₂ O ₃
-The dielectric material for low-temperature sintering obtained by adding and mixing and pulverizing a glass material of -SiO ₂ -Al ₂ O ₃ type has a relatively small variation in relative dielectric constant for each production lot, but still has a large variation. Has a variation in relative dielectric constant of about ± 6. A change in the relative dielectric constant causes a change in the resonance wavelength (resonance frequency) when a filter is manufactured, and if it is too large, adjustment becomes difficult or impossible. Therefore, it is important to keep the relative dielectric constant of the product as constant as possible even if the production lot changes.

[0006] The relative dielectric constant of the fired dielectric porcelain generally increases as the relative density increases. Therefore, when the relative dielectric constant is lowered due to the variation in the material characteristics, the firing temperature may be increased to increase the relative density. However, when the electrode material is provided inside, there is a limit in increasing the firing temperature.
As another method, a method of increasing the relative density by increasing the amount of the glass material added can be considered. However, since glass itself is a low dielectric constant material, an increase in the glass material causes a decrease in the relative dielectric constant. Conversely, even if an attempt is made to increase the relative dielectric constant by reducing the amount of the glass material added, the relative density does not increase and the effect cannot be expected. For this reason, it is very difficult to control the relative dielectric constant to be constant by changing the composition ratio between the high dielectric constant material and the glass material. Even if it is possible to keep the relative dielectric constant constant by changing the composition ratio, there is a concern that the calculation of the composition becomes complicated and that the number of errors made by the operator in the weighing process increases.

Therefore, as shown in FIG.
BaO-TiO calcined_Two-Nd _TwoO_ThreeMass of system high
A small amount is weighed from the dielectric material to obtain a base material for the preliminary test.
The base material taken out and taken out, and the glass material weighed separately
Small batch powder processing that mixes
After that, the sample is molded and fired at a predetermined temperature
A preliminary test is performed to determine the material properties. So
And the relative permittivity of the sample almost matches the target value
In the same way as the small batch processing,
Large batch processing of the body material
Heading manufacturing process). However, if the relative dielectric
When the rate is lower than the target value (including the allowable range)
In some cases, the base material of the production lot is
Cannot be used as a laminated dielectric filter and must be discarded
No (of course, the base material is
Although it can be used as a body material, a series of manufacturing processes
Must be excluded from the process). In any case,
Uses manufactured base material (calcined high dielectric constant material)
Must remanufacture a new base material
However, time and cost losses are extremely large.

[0008] From the above, while maintaining the composition ratio between the base material (calcined high dielectric constant material) and the glass material constant, the relative dielectric constant according to the material characteristics and manufacturing conditions of the base material for each production lot. There is a need for a simple method that can compensate for the decrease in the dielectric constant and make the relative dielectric constant substantially equal to the target value in a subsequent process.

It is an object of the present invention to compensate for characteristic variations that vary from one production lot to another and keep the relative dielectric constant of a final product easily, while keeping the firing temperature and the composition ratio between the base material and the glass material constant. It is an object of the present invention to provide a method for preparing a dielectric material for low-temperature sintering that can be adjusted to a low temperature and avoids a time and cost loss in a manufacturing process.

[0010]

According to the present invention, as shown in FIG. 1, first, a calcined BaO--TiO, which is a base material, is used.
₂ -Nd ₂ O ₃ based mass (1 production lot tens kg, for example about 20 kg) a high dielectric constant small amount of material (several tens to several hundreds g, for example, about 200g) of matrix material for the preceding test weighed After taking out the base material and mixing it with a separately weighed glass material (for example, ZnO-based glass) and subjecting it to small batch powder processing, the sample is formed by molding and firing at a low temperature. A preliminary test for measuring characteristics (relative permittivity) is performed. In this way, it is determined whether or not the measured value of the relative permittivity substantially coincides with the target value, and if not, the amount of decrease from the target value is obtained.

As a result of the characteristic measurement, if the relative dielectric constant substantially coincides with the target value, the remaining base material and the same glass material are simply weighed and mixed so as to have the same composition ratio as in the preceding test. A large batch process of pulverizing the powder may be performed. On the other hand, if the characteristic measurement shows that the relative dielectric constant has decreased from the target value, 1% by volume is calculated according to the decrease.
The addition amount of Bi ₂ O ₃ is determined within the following range. Then, the remaining base material and the same glass material as described above are weighed so as to have the same composition ratio as in the preceding test, and Bi ₂ O ₃ is weighed and added, followed by large batch processing of mixing and pulverizing.
The mixed and pulverized material thus adjusted flows to the next step, for example, a green sheet manufacturing step.

For example, the base material is calcined BaO--Ti
For O ₂ -Nd ₂ O ₃ based high dielectric constant material, to produce a multilayer dielectric filter using an appropriate amount is added to the materials glass material, the dielectric constant of the final product at approximately 63 ± 1.5 If there is, it is within the adjustable range of the resonance frequency and can be used. Therefore, a dielectric material is prepared to have such a relative dielectric constant.

Here, the added amount of Bi ₂ O ₃ is within 1% by volume. By adding 1% by volume, the relative dielectric constant can be improved by about 4 or so. Even if more amount of Bi ₂ O ₃ is added, the relative dielectric constant does not increase and conversely decreases if it is too large, and addition of Bi ₂ O ₃ tends to lower the Qf value. Is meaningless. From this, in the present invention, even if the relative dielectric constant of the sample of the preceding test is lower than the target value (including the allowable range) by about four, the relative dielectric constant is increased by adding an appropriate amount of Bi ₂ O _{3 so} as to be close to the target value. It can be seen that it can be improved up to. Specifically, for example, the addition amount x (volume%) of Bi ₂ O ₃ is calculated by the formula y ≒ 3.2x ² + x with respect to the decrease y from the target value of the relative dielectric constant.

Bi ₂ O _{3 is} used for the base material and the glass material.
The reason why the relative dielectric constant is improved by adding is not completely elucidated, but the following factors are considered. Bi ₂
The melting point of O ₃ is 817 ° C., which is considerably lower than the firing temperature of the dielectric material for low-temperature sintering (usually 900 to 1000 ° C.). Therefore, Bi added in a small amount enters into the glass material, functions as a sintering aid, and improves the sinterability of the material. Therefore, what is important is that Bi ₂ O ₃
Is not contained in the calcined BaO—TiO ₂ —Nd ₂ O ₃ -based high dielectric constant material, but must be put together with the glass material separately. Incidentally, Bi ₂ O ₃ in the same amount of preliminarily fired BaO-TiO ₂ -Nd
Even if it is added in advance to a ₂ O ₃ -based high dielectric constant material, the effect of improving the relative dielectric constant as in the present invention does not occur. In other words, it is important that an appropriate amount of added Bi enters the glass.

[0015]

As base material used in the Detailed Description of the Invention The present invention (calcined previously BaO-TiO ₂ -Nd ₂ O ₃ based high dielectric constant material) is, for example, BaO is 10 as a main component
16 mol%, TiO ₂ is 67 to 72 mol%, Nd ₂ O ₃
There has a composition of 16 to 18 mol%, the Bi ₂ O ₃ 7 to 10 wt% as an auxiliary component other hand, the Al ₂ O ₃ 0.3
There is a material containing about 1.0% by weight. As the glass material, 45 to 70% by weight of ZnO and 5% of B ₂ O ₃ were used.
To 13 wt%, SiO ₂ is 7-40 wt%, Al ₂ O ₃
There composition is 8-20 wt%, already have material _{ZnO-B 2 O 3 -SiO 2} -Al 2 O 3 system is vitrified.

The above-mentioned host material itself has dielectric properties exhibiting a high dielectric constant. However, in order to exhibit good characteristics by itself, ordinary firing at a high temperature of about 1300 ° C. or more must be performed. In order to fire a dielectric molded product containing an internal electrode material such as Ag to produce a dielectric component, it must be able to be sintered at 1000 ° C. or lower. Therefore, a glass material is added to the base material, and the base material is pulverized.

In the BaO-TiO ₂ -Nd ₂ O ₃ -based high dielectric constant dielectric material, the above-mentioned component range is particularly preferable because the material itself exhibits the best characteristics. It is. BaO as a main component is 10%.
If it is less than mol%, the relative dielectric constant becomes small, and if it exceeds 16 mol%, the temperature coefficient becomes large. TiO ₂ is 67 mol%
If it is less than 70%, the sinterability is poor, and if it exceeds 72 mol%, the temperature coefficient becomes large. If Nd ₂ O ₃ is less than 16 mol%, the temperature coefficient is poor, and if it exceeds 18 mol%, the relative dielectric constant becomes small. When the content of Bi ₂ O _{3 as} an auxiliary component is less than 7% by weight, the effect of improving the temperature coefficient is small, and when it exceeds 10% by weight, the sinterability deteriorates. When Al ₂ O ₃ is less than 0.3% by weight, the effect of improving Qf and temperature coefficient is small, and when it exceeds 1.0% by weight, the relative dielectric constant is small and Qf is reduced.

Next, the glass material is for sintering a high dielectric constant material at a low temperature, and is made of ZnO--B ₂ O ₃ --Si.
The addition of an appropriate amount of the O ₂ —Al ₂ O ₃ system is effective for improving the relative density of the sintered porcelain. The reason why it is particularly preferable to set each component range to the above value is as follows. ZnO
When the content is less than 45% by weight, the relative density decreases, and when it exceeds 70% by weight, the relative dielectric constant decreases. B ₂ O ₃ is 5
If it is less than 13% by weight, Qf will be low, and if it exceeds 13% by weight, the relative density will be low. If the content of SiO ₂ is less than 7% by weight, the effect of improving the temperature coefficient is small, and if it exceeds 40% by weight, the relative density becomes low. If the content of Al ₂ O ₃ is less than 8% by weight, Qf
Becomes lower, and when it exceeds 20% by weight, the relative dielectric constant becomes smaller. Such a glass material is used as a base material, BaO-T.
iO ₂ -Nd 3 to 20 against ₂ O ₃ based high dielectric constant material
By adding the volume%, firing can be performed at an appropriate temperature of 880 to 1000 ° C. At this time, the addition amount of the glass material is 3 to 2
0% by volume is preferred. If it is less than 3% by volume, low-temperature sintering is difficult, and if it exceeds 20% by volume, the relative permittivity will be reduced.

In the present invention, the average particle size of the material is set to 0.1. It is preferable to adjust it to several μm or less. Thereby, reactivity can be increased and low-temperature sintering can be promoted. Note that the base material and the glass material may be mixed in advance and pulverized. However, at the time after adding Bi ₂ O ₃ , the base material, the glass material, and the Bi ₂
Mixing O ₃ and pulverizing it is preferable because the process is simplified.

[0020]

EXAMPLE A calcined BaO-TiO _{2 serving} as a base material was used.
-Nd ₂ O ₃ -based high dielectric constant material and ZnO-based glass material are weighed. Base material The main components are BaO 15 mol%, TiO ₂ 69 mol%, Nd
A ₂ O ₃ 16 mol%, Bi ₂ O ₃ 8% by weight as an auxiliary component, Al ₂ O _3: A composition comprising 0.3 wt%,
This is a material that has been calcined. Glass material A pre-vitrified material having a composition of 70% by weight of ZnO, 7% by weight of B ₂ O ₃ , 11% by weight of SiO _{2 and} 12% by weight of Al ₂ O ₃ . These materials are mixed at a volume ratio of the glass material 5 to the base material 95.

To these mixed powders, Bi ₂ O ₃ is added in a range of 3% by volume or less (including those without Bi ₂ O ₃ for comparison), mixed and pulverized (average particle size: 0.6μ
m) to prepare a material powder. A measurement sample is manufactured using the various material powders. The manufacturing process is a very general one, in which a binder is added, granulated, pressed into a predetermined shape, and then fired at a predetermined temperature (here, 930 ° C.). Then, the relative permittivity εr is measured by the cavity resonator method. FIG. 3 shows the measurement results. FIG. 3 is a plot of the relative dielectric constant εr with respect to the amount of Bi ₂ O ₃ added (% by volume).

As can be seen from FIG. 3, by adding an appropriate amount of Bi ₂ O ₃ within a range of 1% by volume or less, Bi ₂ O ₃ is added.
It can be seen that the relative dielectric constant can be increased by about 4 as compared with the case where no is added. However, when the added amount of Bi ₂ O ₃ exceeds 1% by volume, on the contrary, the relative dielectric constant starts to decrease, and although not shown, it has been found that Qf also greatly decreases. % Or less. Thus, for example, if the target value of the relative dielectric constant of the sintered product is 63 and the allowable range is ± 1.5, about 0.6% by volume of Bi ₂ O ₃ is added to the base material and the glass material. As a result, the relative permittivity can be made closer to the target value, and the dielectric constant can be adjusted to a usable dielectric property.

In FIG. 3, when the amount of Bi ₂ O ₃ added is 1% by volume or less, when the relative permittivity is Y and the amount of added Bi ₂ O ₃ is x, the curve is approximated by a quadratic curve. ≒ 3.2x ² + x + c Here, c is the relative dielectric constant when Bi ₂ O _{3 is} not added. The relative dielectric constant changes depending on the matrix material, the glass material, the mixing ratio of the two, and the state of adjustment of the powder, but the degree of the effect of the increase of the relative dielectric constant by the addition of Bi ₂ O ₃ is almost the same. Has a substantially parallel movement relationship), and when y is a difference from the target value of the relative dielectric constant, y ≒ 3.2x ² + x. Therefore, by implementing the preceding test measurement of specific dielectric constant in the case of Bi ₂ O ₃ not added, when determining the decrease amount y from the target value of the measured dielectric constant, Bi ₂ O ₃ added from the above equation The quantity x can be calculated. In large batch processing, B
By adding i ₂ O ₃ , it is possible to prepare a dielectric material for low-temperature sintering such that the relative dielectric constant becomes almost a target value.

[0024]

As described above, according to the present invention, Bi ₂ O ₃ is added to a matrix material and a glass material in an amount corresponding to a decrease from a target value of the relative dielectric constant, mixed, and pulverized. Therefore, even if the relative dielectric constant when using only the base material and the glass material is lower than the target value and cannot be used as it is, without changing the composition ratio of the base material and the glass material , And without changing the firing temperature
By a simple operation of adding an appropriate amount of Bi ₂ O ₃ , it is possible to improve the relative dielectric constant and prepare a material near the target value. As a result, the base material can be effectively used, which can contribute to a reduction in yield and a reduction in cost. In addition, since the relative permittivity can be adjusted quite accurately, there is an effect that a process such as adjustment of a resonance frequency can be simplified when manufacturing a product such as a laminated dielectric filter.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a material preparation step according to the present invention.

FIG. 2 is an explanatory view showing an example of a conventional material preparation step.

FIG. 3 is a graph showing a change in relative dielectric constant with respect to the amount of added Bi ₂ O ₃ .

Claims (3)

[Claims] 1. A calcined BaO—Ti as a base material
O ₂ -Nd ₂ O ₃ based retrieval of large amounts of matrix material for the preceding test with a small amount weighed a high dielectric constant material is micronized and mixed with base material extracted, and a glass material weighed separately small batches After the powder processing, the sample is molded and fired at low temperature to conduct a preliminary test to measure the relative permittivity, and the decrease in the measured relative permittivity from the target value is determined. The materials and the same glass material as described above are weighed so as to have the same composition ratio as in the preceding test. A low-temperature sintering process characterized in that Bi ₂ O ₃ is added, mixed and finely pulverized, and the relative dielectric constant of the large-batch processed product is adjusted to substantially match a target value. Preparation method of dielectric material. 2. The method for preparing a dielectric material for low-temperature sintering according to claim 1, wherein the glass material is a ZnO-based material. _3. The addition amount x (vol%) of Bi ₂ O ₃ is defined as y ≒ with respect to the decrease y of the measured value of the relative dielectric constant from the target value.
3.2x ² + x becomes method for preparing a low-temperature sintered dielectric material of claim 1, wherein the calculated added formula.