JPH10177817A - Dielectric ceramic composition and dielectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition and a dielectric resonator whose dielectric constant is 7 or less and Q value at measured frequency 10GHz is 2,000 or more, and firing condition can be improved. SOLUTION: This dielectric ceramic composition is composed of a primary ingredient 60-99.9weight% which satisfies 10<=x<=40, 10<=y<=40, 20<=z<=80, x+y+z=100 when the composition expression by the molar ratio of metallic element oxide is expressed as xMgo.yAl2 O3 .zSiO2 and 0.1-40weight% of Sm by Sm2 O3 conversion, and there should exist Sm2 Si2 O7 as crystalline phase. It is desirable that the dielectric constant is 7 or less, and that Q value at measured frequency 10GHz (room temperature) is 2,000 or more.

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 example, a substrate for a circuit element used in a microwave or a millimeter wave band such as a microwave or a millimeter wave integrated circuit, and a support member for a dielectric resonator. , Dielectric resonator, dielectric waveguide,
The present invention relates to a high frequency dielectric ceramic composition useful as a material for a dielectric antenna or the like, and a dielectric resonator in which the dielectric ceramic is fixed to a substrate via a support member.

[0002]

2. Description of the Related Art In a high frequency circuit element such as a microwave or millimeter wave integrated circuit, a structure in which a dielectric resonant ceramic is fixed to a substrate via a supporting member may be adopted. For example, as shown in FIG. 1, a dielectric resonator control type microwave transmitter attaches a dielectric porcelain 1 to a porcelain substrate 3 via a support member 2 and generates a magnetic field H leaking out of the dielectric porcelain 1. A strip line 4 provided on the porcelain substrate 3 is used by utilizing such a structure, and these are housed in a metal case 5.

In this type of high-frequency circuit, a resonance system having a high no-load Q is formed by controlling the leakage of the electromagnetic field of the dielectric ceramic 1 through the support member 2. For the member 2, it is necessary to use a material having a low relative dielectric constant and a small dielectric loss (tan δ) (a large Q value). For this reason, conventionally, forsterite having a relative dielectric constant of about 7 and a Q value of about 15,000 at a measurement frequency of 10 GHz has been employed as a material of the support member 2, and the relative dielectric constant of the material of the porcelain substrate 3 is mainly Alumina porcelain having a Q value of about 20,000 or more at about 10 and a measurement frequency of 10 GHz has been employed (for example, see Japanese Patent Application Laid-Open No.
No. 04, etc.).

On the other hand, cordierite is conventionally known as a low dielectric constant material. However, since the firing temperature range is extremely narrow, it is difficult to obtain a dense sintered body. Dielectric constant 4-6, measurement frequency 10
It is used as a glass ceramic having a Q value of about 1000 at GHz (for example, JP-A-61-234128).
Reference).

[0005]

However, the relative dielectric constants of alumina and forsterite which have been conventionally used are about 10 and about 7, respectively, and with the recent widespread use of high frequency band dielectric resonators. Therefore, a material having a lower dielectric constant has been demanded.

On the other hand, porcelain such as glass ceramic used as a low dielectric constant material has a relative dielectric constant as small as about 4 to 6, but has a Q value of about 1000 at a measurement frequency of 10 GHz, and has a high frequency range in recent years. With the spread of dielectric resonators, there has been a demand for a low dielectric constant material having a higher Q value.

Further, alumina porcelain mainly used for a porcelain substrate of a resonator has a relatively high relative dielectric constant of about 10, and the line width becomes too small to form a high-impedance strip line (usually). (1 μm or less), there is a problem that disconnection occurs, the relative variation in line width increases, and the failure rate of the microwave integrated circuit increases.

On the other hand, if the thickness of the substrate is constant, the impedance of the strip line in this type of porcelain substrate is inversely proportional to the relative permittivity and the width of the strip line. By using a substrate material having a low relative dielectric constant, the impedance can be increased, and therefore, a material having a lower dielectric constant has been demanded.

As one means for solving the above-mentioned problem, the present applicant has proposed a composite oxide comprising Mg, Al, and Si as metal elements, and the molar ratio composition formula of each metal element oxide is xMgO.yAl ₂ O. _When expressed as ₃ · zSiO ₂ , the x, y, and z are 10 ≦ x ≦ 40, 10 ≦ y ≦ 40, 20 ≦
z ≦ 80, x + y + z = 100, and a relative dielectric constant of 6
Below, and the Q value at the measurement frequency of 10 GHz is 2000
The above-described dielectric ceramic composition for high frequency and dielectric resonator have already been proposed (Japanese Patent Application No. 7-195211).

The high frequency dielectric ceramic composition comprises alumina,
It was an excellent material having a lower dielectric constant than forsterite and a higher Q value than glass ceramic.

However, conventionally, cordierite has a very narrow firing temperature range, so that it is difficult to obtain a dense sintered body, and the above-described dielectric ceramic composition for high frequency which the inventors of the present invention filed earlier was no exception. . On the other hand, conventionally, an attempt has been made to increase the firing temperature range by adding Sm ₂ O ₃ to cordierite (see Japanese Patent Publication No. 6-74172).
Since a glass phase is generated by the addition of m ₂ O ₃ , the relative dielectric constant in a high frequency region is as low as 5 or less, but the Q value is 50 or less.
There is a problem that it is as low as about 0 (dielectric loss about 0.002).

An object of the present invention is to provide a dielectric ceramic composition and a dielectric resonator having a relative dielectric constant of 7 or less, a Q value at a measurement frequency of 10 GHz of 2000 or more, and capable of improving firing conditions. Aim.

[0013]

The dielectric porcelain composition of the present invention is a composite oxide comprising Mg, Al and Si as metal elements, wherein the composition formula based on the molar ratio of each metal element oxide is xMgO · When represented by yAl ₂ O ₃ .zSiO ₂ , x, y and z are 10 ≦ x ≦ 40 and 10 ≦ y
≦ 40, 20 ≦ z ≦ 80, x + y + z = 100, 60 to 99.9% by weight of the main component, and Sm of 0.1 to 40% by weight in terms of Sm ₂ O ₃ , and Sm as a crystal phase ₂ Si ₂ O ₇ is present. Further, the dielectric ceramic composition of the present invention has a characteristic that the relative dielectric constant is 7 or less and the Q value at a measurement frequency of 10 GHz (room temperature) is 2000 or more.

Further, the dielectric resonator according to the present invention is a dielectric resonator comprising a dielectric ceramic fixed on a substrate via a supporting member, wherein the substrate and / or the supporting member are:
It consists of the above-mentioned dielectric ceramic composition.

[0015]

In the dielectric porcelain composition disclosed in Japanese Patent Publication No. 6-74172, cordierite powder is added with Sm.
_Although firing is performed by adding ₂ O ₃ , Sm ₂ O ₃ is present as glass at the grain boundaries of the cordierite phase, and the dielectric loss is considered to be as large as about 0.002 due to this glass.

The present inventors have conducted intensive studies on this point, and found that the added Sm ₂ O ₃ has a low dielectric constant and a high Q value.
_{It has been found} that by controlling the cooling rate so as to precipitate as ₂ Si ₂ O ₇ , the relative dielectric constant at a measurement frequency of 10 GHz can be at most 7 and the Q value can be at least 2,000, and the present invention has been accomplished.

In addition, when Sm ₂ O ₃ functions as an auxiliary agent, the firing conditions can be improved without severely deteriorating the characteristics obtained by strictly controlling the firing conditions such as the firing temperature. In other words, it is possible to obtain a dielectric ceramic having a relative dielectric constant of 4 to 7 and a Q value at a measurement frequency of 10 GHz and a low dielectric constant of 2000 or more, and for example, a firing temperature width of about 5 to 10 ° C. Can be extended to about 80 ° C., which facilitates production and improves mass productivity.

Then, such a dielectric ceramic having a low dielectric constant and a high Q value is formed, for example, by using a support member of a dielectric resonator and / or
Alternatively, by using a substrate, a high-frequency circuit element such as a high-impedance microwave integrated circuit can be manufactured without impairing reliability.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric ceramic composition of the present invention has a composition ratio of xMgO.yAl ₂ O ₃ .zSiO ₂ where x, y and z are 10 ≦ x ≦ 40, 10 ≦ y
Those satisfying ≦ 40, 20 ≦ z ≦ 80, and x + y + z = 100 are the main components.

The main component composition of the dielectric ceramic composition of the present invention is limited to the above range for the following reasons. That is,
The reason why x indicating the molar percentage of MgO is set to 10 to 40 mol% is that if it is less than 10 mol%, a good sintered body cannot be obtained and the Q value is low, and if it exceeds 40 mol%, the relative dielectric constant becomes high. It is. In particular, x indicating the amount of MgO is desirably 15 to 35 mol% from the viewpoint that the Q value is 5000 or more.

Further, if the amount of Al ₂ O ₃ y of the y indicating the molar percentage was 10 to 40 mol% of Al ₂ O ₃ is less than 10 mol%, good sintered body is obtained The reason is that the Q value is lowered, and when it exceeds 40 mol%, the Q value is lowered. Y indicating the amount of Al ₂ O ₃ represents a Q value of 500.
From the viewpoint of 0 or more, 15 to 35 mol% is desirable.

When the molar percentage z of SiO ₂ is 20 ≦ z ≦ 80
The reason for the mol% is that when z is less than 20 mol%, the relative dielectric constant becomes large, and when it exceeds 80 mol%, a good sintered body cannot be obtained and the Q value becomes low. Z indicating the amount of SiO ₂
Is preferably 30 to 65 mol% from the viewpoint that the Q value is 5000 or more.

According to the invention, to that limited Sm 0.1 to 40% by weight Sm ₂ O ₃ in terms of the case the content of Sm ₂ O ₃ is less than 0.1% by weight (main ingredient If it is more than 99.9% by weight), the densification firing temperature does not become wide,
When the content is more than 40% by weight (the content of the main component is less than 60% by weight), the relative dielectric constant becomes too large, and
This is because the firing temperature range is rather narrow. Sm ₂ O
_As the content of ₃ increases, the sintering temperature decreases. On the other hand, the relative dielectric constant increases. Therefore, it is desirable to determine the Sm ₂ O ₃ content in consideration of these characteristics and the densification sintering temperature. . The content of Sm ₂ O ₃ is desirably more than 10% by weight and 40% by weight or less from the viewpoint that it is not necessary to control the cooling rate so strictly.

The dielectric ceramic composition of the present invention has a Q value of 50.
In order to make it equal to or more than 00, 15 ≦ x ≦ 35, 15 ≦ y ≦ 3
It is desirable to satisfy 5, 30 ≦ z ≦ 65. In the present invention, in particular, the composition of cordierite, ie, x = 22.
2, y = 22.2, z = 55.6 and 0.1 of Sm ₂ O ₃
Desirably, the content is about 40% by weight.

The Q value at a measurement frequency of 10 GHz is 2000
The reason for satisfying the above is that when the Q value is 2000 or more, it is possible to sufficiently cope with recent high frequency band dielectric resonators. The Q value is preferably as high as possible, but in particular, the measurement frequency is 10 GHz.
Is preferably 5000 or more.

In the dielectric porcelain composition of the present invention, the main crystal phase is cordierite, and Sm ₂ Si ₂ O ₇ is precipitated at a ratio depending on the amount of Sm ₂ O ₃ added and the firing conditions.
In addition, as other crystal phases, mullite, spinel, protoenstatite, clinoenstatite, cristobalite, forsterite, tridymite, safarin, and the like may be precipitated, but the precipitated phase differs depending on the composition.

As shown in FIG. 1, the dielectric resonator of the present invention comprises a dielectric ceramic 1 on a substrate 3 via a support member 2.
Is fixed, and the support member 2 or the substrate 3 or the support member 2 and the substrate 3 are made of the above-described dielectric ceramic composition. In this case, a known material is used for the dielectric porcelain 1. As the dielectric ceramic 1, the dielectric ceramic composition of the present invention may be used.

The dielectric porcelain composition of the present invention may be used as a raw material powder, for example, MgCO ₃ powder, Al ₂ O ₃ powder, Si
Using O ₂ powder, a Sm ₂ O ₃ powder were weighed at a predetermined ratio, and dried after wet mixing, the mixture was calcined at 1100 to 1300 ° C. in air, and pulverized. An appropriate amount of a binder is added to the obtained powder, and the mixture is molded by a known method such as a doctor plate method or press molding, and the molded body is fired at 1250 to 1440 ° C. for 5 minutes to 10 hours in an oxygen-containing atmosphere such as the air. It is obtained by doing.

After firing, it is necessary to adjust the temperature drop rate according to the amount ratio of Sm ₂ O ₃ to precipitate Sm ₂ Si ₂ O ₇ . In particular, it is necessary to lower the cooling rate when the amount of Sm ₂ O ₃ added is 10% by weight or less.
It is desirable to lower the temperature at a rate of not more than ° C / h. this is,
100 ° C. when the amount of Sm ₂ O ₃ added is 10% by weight or less
If the cooling rate is faster than / h, the added Sm ₂ O ₃
Do not precipitated as m ₂ Si ₂ O _7, or Sm ₂ Si
_This is because the amount crystallized as ₂ O ₇ is extremely small, most of which is present as glass at the grain boundaries of cordierite, and the dielectric loss increases.

When the addition amount of Sm ₂ O ₃ is more than 10% by weight, the cooling rate is 100 ° C./h or more, for example,
300 ° C. to 500 ° C. But Sm ₂ Si ₂ O ₇ is precipitated, but more is better to slow down the cooling rate Sm ₂ Si ₂ O
₇ precipitates and a high Q value can be obtained. Experiments by the present inventors have confirmed that when the amount of Sm ₂ O ₃ added is more than 10% by weight, a sufficient Q value can be obtained even at a temperature lowering rate of 300 ° C./h. In any case, Sm ₂ S
The higher the amount of i ₂ O ₇ precipitated, that is, the slower the temperature drop rate, the higher the Q value. Sm is desirably contained in an amount of more than 10% by weight and 40% by weight or less in terms of Sm ₂ O ₃ from the viewpoint of mass productivity as described above.

The Sm ₂ amounts Si ₂ O ₇ is deposited, which can be estimated from the peak intensity of X-ray diffractometry using Cu-K [alpha ray as an X-ray source, Sm ₂ in the vicinity 2 [Theta] = 30.5 degrees
The peak intensity of Si ₂ O ₇ is desirably 5% or more of the intensity of the main peak of cordierite near 2θ = 29.5 degrees.

The dielectric ceramic composition of the present invention comprises Mg, Al, Si, and Sm as metal elements.
For example, Ca,
In some cases, Ba, Zr, Ni, Fe, Cr, P, Na, Ti, and the like are mixed. In this case, as long as the above composition is satisfied, a porcelain having a low dielectric constant and a high Q value can be obtained.

In the dielectric ceramic composition of the present invention, if a low dielectric constant and a high Q value are required, for example, a circuit element substrate, a dielectric ceramic of a dielectric resonator, a dielectric waveguide Any material such as a dielectric antenna and the like can be applied, but as described above, it is most suitable for a support member or a substrate of a dielectric resonator.

[0034]

EXAMPLE As raw material powder, 99% pure MgCO ₃ , 99.7% pure Al ₂ O ₃ , 99.4% pure SiO ₂
Powder and Sm ₂ O ₃ having a purity of 99.9% were weighed so that the sintered body had the composition shown in Table 1, wet-mixed by a ball mill using ZrO ₂ balls for 15 hours, and then dried. This mixture was calcined at 1200 ° C. for 2 hours and then pulverized. The obtained powder was granulated by adding an appropriate amount of a binder, and the obtained powder was molded under a pressure of 1000 kg / cm ² to obtain a molded body having a diameter of 12 mm and a thickness of 8 mm. The molded body is fired in the atmosphere at 1250 to 1500 ° C. for 2 hours, and then cooled to room temperature at a temperature decreasing rate as shown in Tables 1 and 2.
A dielectric porcelain sample was obtained.

Using this sample, the relative dielectric constant and Q value at a frequency of 10 GHz (room temperature) were measured by the dielectric cylinder resonator method, and the results are shown in Tables 1 to 3.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

Tables 1 to 3 show that the dielectric ceramic composition according to the present invention has a low relative dielectric constant of 7 or less and a high Q value of 2000 or more at a measurement frequency of 10 GHz. . In the sample of the present invention, C-ray was used as the X-ray source.
X-ray diffraction measurement using u-Kα ray shows that Sm ₂ Si ₂ O ₇ is precipitated in addition to cordierite.

FIG. 2 shows an X-ray diffraction chart of the sample No. 43. From this Figure 2, in addition to cordierite,
It can be seen that Sm ₂ Si ₂ O ₇ was precipitated. Also, 2
It can be seen that the peak intensity of Sm ₂ Si ₂ O ₇ near θ = 30.5 degrees is 5% or more of the intensity of the main peak of cordierite near 2θ = 29.5 degrees.

On the other hand, when the amount of Sm ₂ O ₃ is 0 or 4
In the case of 5% by weight (samples Nos. 89 to 94), although the Q value was high, the firing temperature range was 5 to 10 ° C., indicating that production was difficult.

In samples 95 to 97, Sm ₂ O
₃ was added at 5 parts by weight, but the temperature drop rate was 100 ° C
/ H, the firing temperature range can be widened, but Sm ₂ Si ₂ O ₇ does not precipitate and the Q value is low. FIG. 3 shows an X-ray diffraction chart of a comparative example of Sample No. 96. From FIG. 3, it can be seen that Sm ₂ Si ₂ O ₇ is not precipitated.

[0043]

According to the dielectric porcelain composition of the present invention, Sm is precipitated as Sm ₂ Si ₂ O ₇ , thereby having a low relative dielectric constant of 7 or less and a high Q value at 10 GHz of 2,000 or more. A porcelain exhibiting a Q value can be obtained, and sintering conditions such as a sintering temperature can be improved by Sm ₂ O ₃ as an auxiliary without severely deteriorating the characteristics obtained by strictly controlling the sintering conditions. it can.

By using the dielectric ceramic composition of the present invention for a support member or a substrate of a dielectric resonator, for example, the reliability of a high-frequency circuit element such as a high-impedance microwave integrated circuit is impaired. It can be manufactured without any. In addition, since it has a low dielectric constant and a high Q value, for example, a substrate for a circuit element, a support for a dielectric resonator, a dielectric resonator, It is optimal as a material for dielectric waveguides, dielectric antennas and the like.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a dielectric resonator control type microwave transmitter showing an example of a high-frequency circuit element.

FIG. 2 is an X-ray diffraction diagram showing the crystal structure of Sample No. 43.

FIG. 3 is an X-ray diffraction diagram showing the crystal structure of Sample No. 96.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric porcelain 2 ... Support member 3 ... Porcelain board 4 ... Strip line 5 ... Metal case

Claims (3)

[Claims] 1. A composite oxide comprising Mg, Al and Si as metal elements, wherein a composition formula based on a molar ratio of each metal element oxide is represented by xMgO.yAl ₂ O ₃ .zSiO ₂ , , Y and z satisfies 10 ≦ x ≦ 40 10 ≦ y ≦ 40 20 ≦ z ≦ 80 x + y + z = 100, 60 to 99.9% by weight, and Sm is replaced by Sm
A dielectric ceramic composition comprising 0.1 to 40% by weight in terms of ₂ O ₃ and having Sm ₂ Si ₂ O ₇ as a crystal phase. 2. A device having a relative dielectric constant of 7 or less and a measurement frequency of 10
2. The dielectric ceramic composition according to claim 1, wherein the Q value at GHz (room temperature) is 2000 or more. 3. A dielectric resonator having a dielectric ceramic fixed on a substrate via a support member, wherein the substrate and / or the support member is made of the dielectric ceramic composition according to claim 1. A dielectric resonator characterized in that: