JP3285759B2 - High frequency dielectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition for high frequencies, and more particularly to a material suitable for a dielectric resonator or the like.
The present invention relates to a dielectric ceramic composition for high frequency which is suitable as a material such as a dielectric substrate for C.

[0002]

2. Description of the Related Art Conventionally, in a microwave circuit, a dielectric ceramic material has been widely used for the purpose of downsizing a filter, stabilizing a frequency of a solid-state oscillator, impedance matching, a capacitor, and the like. It's being used. The dielectric ceramic material used in such a microwave region is required to have a high relative dielectric constant (εr) and a small temperature coefficient (τf) of the resonance frequency together with the unloaded Q value. I have. Incidentally, in the case of a band-pass filter using a quarter-wavelength resonator or a half-wavelength resonator, the resonator length can be shortened as the relative permittivity of the dielectric ceramic substrate used therein increases. However, in order to reduce the size of the filter, the higher the relative dielectric constant, the more advantageous. For this reason, various dielectric ceramic compositions (materials) have been proposed so far. For example, Japanese Patent Application Laid-Open No. 57-69607 discloses Ba.
100 of O-xTiO ₂ composition (3.9 ≦ x ≦ 4.1)
A dielectric porcelain composition obtained by adding 1 to 26 parts by weight of ZnO to parts by weight is disclosed.

On the other hand, in a low-pass filter or the like using a distributed constant line as a circuit element, the situation is slightly different from the above. That is, when used as a resonator, only the resonator frequency becomes a problem, but when used as a circuit element such as an inductance, the impedance becomes a problem.

By the way, a distributed constant line having a wavelength of 1/2 wavelength or less can be equivalently converted into a series inductance.
The obtained inductance (L) can be expressed by the following equation. ωL = Z ₀ · sin θ (where ω is the angular frequency, Z ₀ is the characteristic impedance, θ
Indicates the electrical length of the distributed constant line. )

As is apparent from the above equation, it is necessary to adjust the characteristic impedance (Z ₀ ) and the electrical length (θ) of the distributed constant line in order to obtain the required inductance (L) in the design. However, the characteristic impedance is a function of the relative permittivity, thickness, and conductor width of the dielectric ceramic substrate, and the higher the relative permittivity, the lower the characteristic impedance.

In order to reduce the loss in the pass band of the filter, it is necessary to reduce the loss of the used inductance. That is, it is necessary to reduce the loss of the distributed constant line. Then, in order to reduce the loss of the distributed constant line, it is necessary to increase the width of the distributed constant line. However, the countermeasure is to lower the characteristic impedance. It is understood that when the characteristic impedance is reduced, only a small inductance obtained from the above equation can be obtained. Therefore, in order to keep the loss of the distributed constant line small and to widen the range of inductance, it is important to lower the relative dielectric constant of the substrate.

[0007] Further, considering the case where the frequency is increased, the low-pass filter is twice as large as the pass band and 3 times as large as the pass band.
Although attenuation by a factor of 2 is required, as is apparent from the above equation, when the frequency increases and the electrical length exceeds π, the distributed constant line changes to a series capacitance. However, since the series capacitance has a low impedance with respect to a high-frequency signal, the signal does not attenuate twice or three times the signal that must be attenuated. From this, the characteristic impedance is increased,
The desired inductance must be realized with a small electrical length. In order to function as an inductance up to high frequencies by shortening the electrical length,
That is, the attenuation of the low-pass filter by the factor of two or three can be ensured.

For this reason, in order to form the inductance constituting the low-pass filter by the distributed constant line, the relative permittivity of the dielectric ceramic substrate used, and hence the dielectric ceramic material providing such a substrate. The lower the relative permittivity, the better. However, generally, in a substrate that can be fired at a low temperature, when the relative dielectric constant of the substrate becomes as low as 20 or less, the no-load Q value of the substrate deteriorates. The unloaded Q value of the substrate is an important factor that affects the loss of the distributed constant line together with the conductor loss. For this reason, it is required for such a substrate material to simultaneously satisfy a low relative dielectric constant and a high unloaded Q value.

By the way, among the conventional dielectric porcelain compositions, those having a characteristic that the relative dielectric constant is smaller than 30, while the unloaded Q value is 3000 or more, have not been realized yet. In particular, BaO-TiO ₂ -Zn revealed in JP 57-69607 Publication described above
In the O-based dielectric porcelain composition, a material having such properties is not disclosed at all.

[0010]

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a high unloaded Q value of 3000 or more, An object of the present invention is to provide a composition having a dielectric constant as low as 28 or less and a dielectric ceramic having a temperature coefficient of resonance frequency of within ± 21 ppm / ° C.

[0011]

The present inventors have conducted various studies in order to solve such a problem, and as a result, have found that BaO-TiO _2-
The dielectric ceramic composition of the ZnO-based, by incorporating aluminum oxide及beauty acid manganese at a predetermined ratio, while ensuring a high unloaded Q value and a small temperature coefficient, the dielectric constant preferably We have found a fact that can be reduced.

That is, the present invention has been completed based on such findings, and the features thereof are as follows:
General formula: represented by BaO.xTiO ₂ .yZnO;
And x and y in the general formula are each represented by a molar ratio:
Barium oxide, titanium oxide, and zinc oxide configured to satisfy the following formula: 3.2 ≦ x ≦ 5.7, y ≦ 1.4x-3.7, and y> 1.4x-4.48 And aluminum oxide (A) and manganese oxide (B) with respect to 100 parts by weight of the main component composition, under the following conditions: 3.2 ≦ x ≦ 4. When 0.5, 0.5 ≦ A ≦ 1.0, 0 ≦ B ≦ 2.5 4.3 <x ≦ 4.7, 0 <A ≦ 1.5, 0 ≦ B ≦ 2.5 4.7 < When x ≦ 5.3 0.5 ≦ A ≦ 1.5, 0 ≦ B ≦ 2.5 5.3 <x ≦ 5.7 When 0.5 ≦ A ≦ 1.0, 0 ≦ B ≦ 1 .5 (where A and B are in parts by weight) in the dielectric ceramic composition for high frequencies.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the dielectric ceramic composition for high frequency according to the present invention, the general formula: BaO.x
TiO ₂ · yZnO represents the ratio (x, y) of titanium oxide (TiO ₂ ) and zinc oxide (ZnO) to barium oxide (BaO) in terms of molar ratio, respectively. Formula: 3.2 ≦ x ≦ 5.7, y ≦
It must be combined to satisfy 1.4x-3.7 and y> 1.4x-4.48.

However, when the proportion (x) of the TiO ₂ component among the three components increases, the relative permittivity tends to increase, and the temperature coefficient of the resonance frequency increases. This is because, when the ratio (y) increases, the relative permittivity tends to decrease, and the temperature coefficient of the resonance frequency decreases. When the ratio of the TiO ₂ component is too low or too high, This is because the unloaded Q value becomes too low and becomes lower than 3000, and the temperature coefficient of the resonance frequency needs to be within ± 21 ppm / ° C. in the ratio between the TiO ₂ component and the ZnO component. .

The above-mentioned BaO, TiO ₂ and ZnO
Although aluminum oxide (Al ₂ O ₃ ), which is further blended with the main component composition of the formula ( ₁ ), lowers the relative dielectric constant by its addition, the unloaded Q value also decreases. Relative to 100 parts by weight of Al ₂ O ₃ per 0.5 part by weight, the relative dielectric constant decreases at a rate of 0.5 to 1.0,
The value also drops by about 500 to 1000.
Therefore, to make the relative dielectric constant as small as possible, Al
It is desirable to increase the addition amount of ₂ O ₃ , but in the present invention, the upper limit of the addition amount (A) is set to 1.5 parts by weight at the maximum so that the no-load Q value does not become too low. That is. In addition, manganese oxide (MnO ₂ ) added in the same manner as the Al ₂ O ₃ component improves the unloaded Q value without significantly affecting the relative permittivity and the temperature coefficient of the resonance frequency. In the present invention, it is advantageously added. However, if the addition amount is too large, the no-load Q value is rather lowered. ) Will be a maximum of 2.5 parts by weight.

Under these circumstances, the present inventors have conducted various studies and found that the relative permittivity was reduced to a practical range of 28 or less while securing a no-load Q value of 3000 or more. In order to realize the performance with the temperature coefficient of the resonance frequency within ± 21 ppm / ° C., the addition amount of Al ₂ O ₃ (A) and the addition amount of MnO ₂ (B) according to the ratio (x) of the TiO ₂ component. Has to be adjusted, and the following conditions (1) to (4) must be satisfied. When 3.2 ≦ x ≦ 4.3 0.5 ≦ A ≦ 1.0, 0 ≦ B ≦ 2.5 4.3 <x ≦ 4.7 When 0 <A ≦ 1.5, 0 ≦ B ≦ 2.5 4.7 <x ≦ 5.3 0.5 ≦ A ≦ 1.5, 0 ≦ B ≦ 2.5 5.3 <x ≦ 5.7 0.5 ≦ A ≦ 1 0, 0 ≦ B ≦ 1.5

In such a ratio, Al ₂
By adding O ₃ and MnO ₂ to prepare the target dielectric ceramic composition, it became possible to lower the relative dielectric constant to about 24, and thus the optimal substrate A value near 25, which is considered to be a relative dielectric constant, is advantageously realized, and it is possible to achieve both low-loss inductance and compact formation of capacitance.
In addition, the compactness of the capacitance is such that the capacitance in a low-pass filter or the like is formed with the ground and the electrode facing each other, and when a substrate having a low relative dielectric constant is used, the electrode area increases and the filter becomes large. For the purpose of miniaturization, it is necessary to make such a capacitor compact.

As described above, the dielectric porcelain composition according to the present invention provides BaO so as to satisfy the above-mentioned expressions of x and y.
100 parts by weight of the main component composition in which the molar ratios of the TiO ₂ component and the ZnO component are controlled with respect to the weight ratio of Al ₂ so as to satisfy the above conditions in accordance with the ratio (x) of the TiO ₂ component. O ₃ and MnO ₂ are added and contained by weight parts A and B, respectively.
Such a porcelain composition is prepared by calcining and pulverizing the raw material composition giving the composition. If a calcination temperature of 900 ° C. or more is employed for the calcination, a decrease in the calcination temperature of the dielectric ceramic composition accompanying an increase in the calcination temperature is recognized. In particular,
Since the effect is remarkable at a calcination temperature of 1050 ° C. or more, in the present invention, calcination is preferably performed at a temperature of 1050 ° C. or more. However, if the calcining temperature exceeds 1350 ° C., the calcined material hardens significantly after calcining, causing a problem in handling. Therefore, preferably, the calcining temperature of 1100 ° C. to 1300 ° C. is advantageously employed. Becomes

When the calcined material obtained by calcining in this manner is pulverized, the lower the average particle size of the pulverized material, the more the reduction in the firing temperature of the dielectric ceramic composition is promoted. . Therefore, according to the present invention, it is advantageous that the.
The calcined product is pulverized so as to have an average particle size of 8 μm or less. However, when the average particle size of the calcined and pulverized product is smaller than 0.1 μm, the moldability of the obtained dielectric porcelain composition is reduced, and for example, it is difficult to form a tape by a normal doctor blade method or the like. It is desirable to control the average particle size of the calcined and pulverized product to about 0.1 to 0.8 μm. In addition, the particle size of such a fine pulverized product is generally measured using a laser diffraction scattering method.

Further, since the dielectric ceramic composition according to the present invention is applied to a laminated dielectric filter or the like using an Ag-based material having a low conduction resistance for an electrode of an internal pattern, it can be fired at a low temperature. is desirable, in order that, in the present invention, to such a dielectric ceramic composition, further a glass component, for example, ZnO-B ₂ O ₃ -B
i ₂ O ₃ based glass, advantageously added, caused to compounding.
For example, 1 to 45 wt% ZnO-5 to 50 wt% B ₂ O
₃ by -15～94 wt% Bi ₂ O ₃ based formulation of the glass, the firing temperature of the dielectric ceramic composition of interest, 900
It can be lowered to around ° C.

The dielectric porcelain obtained by firing the dielectric porcelain composition according to the present invention is used as a substrate or the like to constitute a resonator of a filter or the like. No-load Q characteristics and practical relative permittivity characteristics,
Furthermore, a temperature coefficient of a small resonance frequency can be advantageously exerted.

[0022]

EXAMPLES Hereinafter, some examples of the present invention will be described to clarify the present invention more specifically. However, the present invention imposes some restrictions by the description of such examples. It goes without saying that you don't receive anything. In addition, various changes, modifications, improvements, and the like can be made to the present invention based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the examples described below. Should be understood.

First, high-purity barium carbonate (BaCO ₃ ) and titanium oxide (Ti
O ₂ ), zinc oxide (ZnO), aluminum oxide (Al
₂ O ₃ ) and manganese oxide (MnO ₂ ), and these components were replaced with various types of x, shown in Tables 1 to 4 below.
y, weighed so as to give Al ₂ O ₃ external amount and MnO ₂ external amount, and further, these raw materials were ball-milled for 16 hours.
Wet mixed. Then, the obtained mixture was taken out from a ball mill, dried, crushed, put into an alumina crucible, and calcined at 1150 ° C. for 4 hours.
Next, the obtained calcined product was disintegrated and wet-pulverized again in a ball mill for 80 hours to obtain various calcined and pulverized products having an average particle diameter of 0.6 μm or less.

Next, ZnO-B ₂ O ₃ -was added to the various calcined and pulverized materials thus obtained as a sintering accelerator.
After adding 2% of the SiO ₂ ternary glass and further adding PVA as a binder, granulation was performed using a sieve having an opening of 355 μm. Then, the obtained granulated powder is press-formed using a press-forming machine, and has a diameter of 1: 1.
Various cylindrical test pieces of 5 mm in length and 10 mm in length were obtained. Then, each of the test pieces was placed in air at 920
Various dielectric ceramic samples were produced by baking at a temperature of ° C. for 2 hours.

Further, various dielectric ceramic samples obtained by the sintering were polished into a cylindrical shape having a diameter of 8 mm and a length of 4 mm, and their dielectric properties were measured. The relative permittivity (εr) and the unloaded Q value were measured by a parallel conductor plate type dielectric resonator method, and the temperature coefficient of resonance frequency (τf) was measured in a range of −25 ° C. to 75 ° C. . The measurement frequency was 3 GHz. The obtained results are shown in Tables 1 to 4 below.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

As is clear from the results of these tables, Nos. 5, 6, 9, 1 having the dielectric ceramic composition according to the present invention.
0, 19, 21, 22, 34 to 36, 38 to 40, 49
~ 51 , 53 , 54 , 56 , 57 , 72 , 73 , 75 ,
For compositions 79 and 80, the unloaded Q value was 300
Although it is 0 or more, the relative permittivity is 28 or less, and the temperature coefficient (τf) of the resonance frequency is
It is within the range of ± 21 ppm / ° C.

On the other hand, in the composition of other No. deviating from the dielectric porcelain composition defined in the present invention, the obtained dielectric porcelain has a relative dielectric constant (εr), no load It was found that at least one of the Q value and the temperature coefficient (τf) of the resonance frequency was lower than the target, and as a result, the dielectric characteristics were inferior.

[0032]

As is clear from the above description, the dielectric ceramic composition for high frequencies according to the present invention is made of BaO, TiO ₂
And ZnO as main components, each of which is
In addition to being contained at a specific molar ratio, and having the Al ₂ O ₃ component and the MnO ₂ component contained at a specific ratio according to the ratio of such a TiO ₂ component, the content is 3000 Above high no-load Q
Value and the temperature coefficient of the resonance frequency is also ± 21 pp
m / ° C and a relative dielectric constant of 2
It is possible to effectively realize a practically effective low relative dielectric constant of 8 or less, reaching 24, and particularly advantageously achieve a relative dielectric constant near 25 which is optimal as the relative dielectric constant of the substrate. That is where the great technical significance of the present invention lies.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/42-35/50 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. General formula: BaO.xTiO ₂ .yZnO
And x and y in the general formula are represented by the following formulas in a molar ratio: 3.2 ≦ x ≦ 5.7, y ≦ 1.
A composition comprising barium oxide, titanium oxide and zinc oxide, which is constituted so as to satisfy 4x-3.7 and y> 1.4x-4.48, and further comprising 100% of the main component composition Aluminum oxide (A) and manganese oxide (B) were added to the parts by weight in the following conditions: 3.2 ≦ x ≦ 4.3 0.5 ≦ A ≦ 1.0, 0 ≦ B ≦ 0 <A ≦ 1.5 when 2.5 4.3 <x ≦ 4.7, 0.5 ≦ A ≦ 1.5 when 0 ≦ B ≦ 2.5 4.7 <x ≦ 5.3, 0 ≦ B ≦ 2.5 5.3 <x ≦ 5.7 When 0.5 ≦ A ≦ 1.0, 0 ≦ B ≦ 1.5 (where A and B are parts by weight) ). A high frequency dielectric porcelain composition characterized in that: