JP2000239061A - Dielectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relatively inexpensive porcelain composition which can be baked at a lower temperature than the melting point of Ag, does not diffuse Ag during baking, can simultaneously be baked together with the Ag, and exhibits electric characteristics comprising a suitably high dielectric constant of about 20-40, a high Q value and a small resonance frequency temperature coefficient which are desirable for dielectric porcelains for high frequency of several GHz or higher. SOLUTION: This dielectric porcelain composition comprises 100 pts.wt. of a main component of formula: BaO.(a-x-y)TiO2.xGeO2+ySiO2 4.0<=(a)<=4.6; 0.15<=(x)+(y)<=0.8; 0.2<=(x)/[(x)+(y)]}, and 0.5-2 pts.wt. (converted into CuO) of Cu, 0.5-4 pts.wt (converted into ZnO) of Zn and 0.3-2 pts.wt. (converted into B2O3) of B as sub-components, wherein the conversion amount of ZnO is not lower than the conversion amount of CuO.

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, and more particularly, to a high frequency dielectric ceramic composition which can be co-fired with a low-resistance metal such as silver.

[0002]

2. Description of the Related Art In recent years, high-frequency components using dielectric porcelain have been frequently used in order to reduce the size of wireless communication devices and transmission / reception devices. For example, dielectric ceramics having an appropriate dielectric constant and a relatively high Q value are used for duplexers and filters for mobile phones in the 0.8 to 2 GHz band, and recently for antennas and the like. The dielectric porcelain used in this field is sometimes called a microwave dielectric porcelain.

The wavelength of an electromagnetic wave in a dielectric is reduced to ε _r ^-1/2 times the wavelength in a vacuum (ε _r : relative permittivity of the dielectric). Therefore, when a dielectric ceramic is used for a distributed constant circuit type component such as a duplexer or a filter, the wavelength is reduced as described above, and the circuit component can be downsized.

[0004] Characteristics required for the dielectric ceramic used in the high frequency distributed constant circuit type component has a specific dielectric constant epsilon _r be moderately high depending on the used frequency, it Q value (reciprocal of dielectric loss) is high ( That is, the dielectric loss <tanδ> of the material is low) and the temperature coefficient τ _f of the resonance frequency is small. BaO-TiO ₂ materials are known as dielectric ceramics that can satisfy such characteristics to some extent.

On the other hand, in order to further reduce the size of the above components, a surface mountable multilayer component having internal electrodes formed in a dielectric ceramic is used instead of a conventional component in which a dielectric resonator is housed in a metal case. It is more advantageous to do so.

[0006] Such a component can be efficiently manufactured by using a green sheet laminating method which is put to practical use in a multilayer capacitor or a multilayer circuit board. That is, after a conductor paste for an internal electrode is printed on a part of the dielectric green sheet in a predetermined electrode pattern, the sheets are laminated, and the laminated body is fired to simultaneously sinter the internal conductor. The external electrode can be formed on the sintered body, or printed with a conductor paste on the laminate before sintering, and fired simultaneously with the dielectric and the internal conductor. As a result, dielectric ceramic parts having internal electrodes designed in various shapes can be efficiently manufactured by a single firing, and the size of the dielectric ceramic parts can be made significantly smaller than the resonance wavelength. Therefore, the size of the component can be further reduced.

In a transmission line of a part or a circuit generally used in a microwave band or the like, Au, Ag, Cu, Ag-Pd (Pd:
(Less than several%). The melting points of these metals are as low as 1063 ° C for Au, 961 ° C for Ag, and 1083 ° C for Cu. Therefore, when manufacturing a laminated component by simultaneous firing with an internal conductor by a green sheet laminating method, a dielectric porcelain that can be sintered at a temperature lower than the melting point of the conductive metal is required. Conventional BaO-TiO ₂ materials have a high sintering temperature.
It must be fired at a temperature of 00 ° C. or more for a long time, and cannot be used for production by such low-temperature firing.

Further, in recent years and in the near future, high-speed wireless LA
N, ITS (Intelligent Transport System) related mobile communications, 2.5 GHz band, 5
The use of higher frequency bands, such as the GHz band and beyond, is being considered. In such a case, the distributed constant circuit-type component can be reduced in accordance with the increase in frequency. Therefore, it is not always necessary to increase the dielectric constant of the material too much, as in the case of a circuit component material used in a conventional mobile phone or the like. Instead, it may be an appropriate dielectric constant (for example, about 20 to 40). On the other hand, in the high-frequency band as described above, the electric energy loss in the component becomes large, so that the Q value of the component, that is, the Q value of the dielectric material to be used is increased so as to suppress this loss as much as possible. It is required to increase the resistance and to lower the resistance of the electrode material used.

[0009] Among the low-resistance metals used as the electrode materials described above, Cu is easily oxidizable and must be fired in a non-oxidizing atmosphere (eg, a nitrogen atmosphere or a nitrogen + hydrogen atmosphere). Baking equipment and operating costs increase. On the other hand, noble metals such as Au and Ag are chemically stable and can be fired in air. However, since Au is expensive, Ag or the above-mentioned Ag-Pd is advantageous as an electrode material in the case of baking in air. Among them, Ag, which is the metal having the lowest resistance, is particularly advantageous from the viewpoint of suppressing electric energy loss of components.
However, Ag has the lowest melting point among the above low resistance metals. Therefore, as the dielectric porcelain material, the lowest resistance Ag
It is desirable to use a material that can be fired at a temperature lower than the melting point of Ag so that it can be fired simultaneously.

For example, Japanese Patent Application Laid-Open No. 6-279109 discloses Ba
And the O-TiO-GeO ₂ material is contained B compound, Q value is high, the low temperature sinterable dielectric ceramic composition is described. However, since the firing temperature is 960-1400 ° C, Au and
Ag with a melting point of 961 ° C, although simultaneous firing with Ag-Pd is possible
Can not be used for simultaneous firing with. Further, this material is disadvantageous in terms of price because the Ge component is expensive.

Japanese Patent Application Laid-Open No. Hei 8-59344 discloses BaO-TiO-Nd
A dielectric porcelain composition in which a glass composition and CuO, SrTiO _{3 and the} like are added to a material containing Bi ₂ O ₃ and PbO in O _3/2 is disclosed. This dielectric ceramic composition has a very low sintering temperature and can be co-fired with Ag, but cannot be said to have a sufficiently high Q value.

[0012]

As described above, as a dielectric ceramic material for a distributed constant circuit type component for high frequencies of several GHz or more, the dielectric constant is appropriately high at about 20 to 40 and the Q value is sufficiently high. It is required that the temperature coefficient of the resonance frequency be low and the content of expensive components be as small as possible.

Further, in order to manufacture a laminated component by the above-described green sheet multilayer laminating method, it must be possible to fire at a temperature lower than the melting point of a low-resistance conductive metal, preferably Ag. Furthermore, if the conductive metal diffuses into the dielectric porcelain during firing, it becomes difficult to form a precise electrode pattern. Therefore, a material that suppresses this diffusion is desirable.

The present invention has the above-described high-frequency characteristics desired for a dielectric ceramic used in a high-frequency band of several GHz or more,
And it can be fired at a temperature lower than the melting point of Ag,
Does not diffuse into the dielectric porcelain, thereby providing a relatively inexpensive dielectric porcelain composition.

[0015]

Means for Solving the Problems A dielectric porcelain is used as an inner conductor.
When co-firing with Ag, it is common to fire at a temperature several tens of degrees lower than the melting point of 961 ° C of Ag (eg, 930 ° C or less). Have been considered necessary. The firing temperature is lowered in this way to prevent Ag from diffusing into the dielectric ceramic during firing. Therefore, if diffusion of Ag can be prevented, there should be no problem even if firing is performed at a temperature immediately below the melting point of Ag.

The present inventors have studied the dielectric porcelain composition from this viewpoint, and as a result, have shown the desirable high-frequency characteristics described above, can be sintered at a firing temperature lower than 960 ° C., and the diffusion of Ag during firing is suppressed. A relatively inexpensive dielectric porcelain composition that is unlikely to occur has been found.

In the present invention, the following composition formula BaO. (Axy) TiO ₂ .xGeO ₂ + ySiO ₂ [where 4.0 ≦ a ≦ 4.6 0.15 ≦ x + y ≦ 0.8 0.2 ≦ x / (x + y)] With respect to 100 parts by weight of the component, 0.5 to 2 parts by weight of Cu in terms of CuO, 0.5 to 4 parts by weight of Zn in terms of ZnO, and 0.3 to ₂ parts by weight of B in terms of B ₂ O ₃ as subcomponents, And ZnO conversion amount ≥ CuO conversion amount,
A dielectric porcelain composition characterized in that:

The dielectric porcelain formed from the composition of the present invention has the following high-frequency characteristics desired for a high-frequency dielectric porcelain of several GHz or more: a relative dielectric constant (ε _r ) of 30 to 36; Moderately high, Q value is expressed as fQ (f = 5 to 6 GHz) value, 8000 GHz
The temperature coefficient of resonance frequency (τ _f ) is as low as ± 30 ppm / ° C or less.

The dielectric porcelain composition of the present invention is sintered at a firing temperature lower than 960 ° C., and when sintered together with Ag, diffusion of Ag can be prevented. The sintering temperature is just below the melting point of Ag 961 ° C,
For example, the temperature may be 960 ° C., but even at a sintering temperature close to the melting point of Ag, Ag is not diffused during sintering, so that the dielectric ceramic can be co-sintered with Ag.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The chemical composition of the dielectric porcelain composition of the present invention is as follows: BaO. (Axy) TiO ₂ .xGeO ₂ + ySiO ₂ 4.0 ≦ a ≦ 4.6... 0.15 ≦ x + y ≦ 0.8 ... x / (x + y) ≥0.2 With respect to 100 parts by weight of the main component represented by: ... 0.5 to 2 parts by weight of Cu as CuO as an auxiliary component ... 0.5 to 4 parts by weight of Zn as ZnO the ... B in a proportion of 0.3 to 2 parts by weight.. in terms _of B ₂ O _3, and ... still a ZnO equivalent amount ≧ CuO equivalent amount, a, x, y is the molar ratio .

In the dielectric porcelain composition of the present invention, as a main component, a BaO—TiO ₂ system known to provide a dielectric porcelain having a good relative dielectric constant, a Q value and a good temperature coefficient τ _f is selected. GeO ₂ or GeO ₂ to reduce the sintering temperature
+ SiO ₂ is blended. The total amount of this compounding component may be GeO ₂ , but the germanium compound is expensive, so that up to 80 mol% thereof can be replaced by much cheaper SiO ₂ . Si
When the amount of O ₂ is within this range, the high-frequency characteristics are hardly deteriorated, and the material cost can be reduced. Cu, Zn and B added as subcomponents are effective elements for further lowering the sintering temperature, suppressing Ag diffusion during firing, and / or improving the performance of the dielectric ceramic.

The reasons for limiting the composition of the dielectric ceramic composition of the present invention as described above are as follows. For a <4, the fQ value drops significantly; for a> 4.6, τ _f increases.

When x + y <0.15, the sintering temperature is not sufficiently low; when x + y> 0.8, τ _f increases to the negative side. When x / (x + y) <0.2, the f · Q value is significantly reduced.

At (CuO content) <0.5 parts by weight, the sintering temperature is not sufficiently low; at (CuO content)> 2 parts by weight, the f · Q value is reduced, and τ _f is significantly degraded to the negative side. Ag diffusion increases.

When (ZnO amount) <0.5 part by weight, f · Q value is remarkably reduced and Ag diffusion amount is increased; (ZnO amount)
At> 4 parts by weight, the fQ value decreases and τ _f remarkably deteriorates to the negative side.

At (B ₂ O ₃ amount) <0.3 parts by weight, the sintering temperature is not sufficiently low; and at (B ₂ O ₃ amount)> 2 parts by weight, f ·
The Q value decreases, and the amount of Ag diffusion increases. When (CuO content)> (ZnO content), the diffusion amount of Ag increases.

The preferred composition of the dielectric porcelain composition of the present invention has the following composition so that τ _f ≦ ± 20 ppm / ° C. or less: 4.1 ≦ a ≦ 4.6 0.15 ≦ x + y ≦ 0.6 0.2 ≦ x / (x + y), Cu is 0.5 to 2 parts by weight in CuO conversion, Zn is 0.5 to 2 parts by weight in ZnO conversion
2 parts by weight, 0.3 to 1.5 parts by weight of B in terms _of B ₂ O _3.

The dielectric ceramic having the composition according to the present invention can be manufactured by a conventional method. That is, an oxide of each component metal, a composite oxide of two or more component metals (eg, BaTiO ₃ )
And / or suitable precursor compounds (eg, carbonates and carboxylate salts) that convert to oxides of the component metals during firing, are mixed in proportions to produce a predetermined composition, calcined, and shaped. After that, firing may be performed. In this case, the calcination temperature is preferably in the range of 1000 to 1100 ° C, and the calcination temperature is preferably in the range of 900 to 960 ° C.

In addition, the material BaO- (4 to
In 4.6) TiO _2, since Ge is in an amount within the above range is considered to be Ti site, BaO and TiO ₂ (or Ba-Ti compound and TiO _2, such as BaTiO ₃₎ only GeO _2, first 950 to 1150
After calcination at a temperature of ° C., the remaining components (SiO ₂ and the sub-component material or only the sub-component material) may be mixed, molded and fired. In this case, the main component BaO- (4-4.6) (Ti,
Ge) excellent high-frequency characteristics of the O ₂ based dielectric ceramic, the remaining it is possible to minimize the deterioration by the addition of ingredients, mixing all the ingredients at once, compared with the case of calcining And more excellent characteristics can be obtained.

However, as long as BaO, TiO ₂ and GeO ₂ are present at the time of calcination, even if one or more other materials other than B ₂ O ₃ are further present, the case of the above-mentioned method is not considered. A dielectric porcelain having almost no difference in characteristics can be obtained. That is,
Materials other than B ₂ O ₃ or its precursor compound can be mixed before calcination. It is preferable to add only the B ₂ O ₃ raw material after calcination. If B ₂ O ₃ is present during calcination, Ge
Does not enter the Ti site, and the Q value of the dielectric ceramic deteriorates.

The dielectric porcelain according to the present invention is suitable for producing a laminated dielectric porcelain component by firing together with a low-resistance inner layer conductor such as Ag by the above-described green sheet laminating method. The green sheet is made into a slurry by adding an appropriate amount of a binder, a plasticizer, a solvent, etc. to the calcined powder of the whole mixed raw material, or the calcined powder of the partial raw material and the mixed powder of the remaining raw materials, It can be produced by molding by a doctor blade method or the like.

On a green sheet cut to an appropriate size,
A conductor paste mainly composed of a low-resistance metal for forming an internal electrode is screen-printed in a predetermined shape, and then a screen-printed green sheet and a non-screened green sheet are appropriately combined and laminated, and thermocompression-bonded. If necessary, the laminate is cut and fired at the same time to form an external electrode to obtain a laminated component. The conductor paste for forming the external electrodes may be applied before firing and fired simultaneously.

The preferred conductor material for the internal electrodes is Ag, which is relatively inexpensive, has the lowest resistance, and can be fired in air. When the dielectric porcelain according to the present invention is used, even if an Ag paste is used for forming the internal electrodes, sintering can be performed at a temperature of 960 ° C. or less, and diffusion of Ag into the dielectric porcelain during firing is suppressed. Therefore, it is possible to co-fire with the Ag conductor without deteriorating the temperature characteristics and Q value of the dielectric ceramic due to the inclusion of Ag, and without deforming the electrode shape, and it is possible to sufficiently cope with miniaturization of the wiring pattern.

Therefore, for example, when a dielectric porcelain is used for a filter, deterioration of temperature characteristics is prevented, and it is not necessary to design a wider pass band in advance, and insertion loss can be reduced.

[0035]

EXAMPLES Examples of manufacturing dielectric ceramics using the dielectric ceramic composition according to the present invention will be described below along with comparative examples. However, the following examples are illustrative and do not limit the present invention. Further,% in Examples is% by weight unless otherwise specified.

[Preparation of High Frequency Characteristic Evaluation Sample] BaTiO ₃ , TiO ₂ , GeO ₂ , SiO ₂ , CuO, and ZnO powders having a purity of 99% or more were blended so as to have the composition shown in Table 1, and were wet-processed by a ball mill. Mix and evaporate the solvent to obtain a powder mixture. This powder mixture was calcined in the atmosphere at 1000 ° C. for 2 hours, B ₂ O ₃ was added to the calcined product so as to have the composition shown in Table 1, and the mixture was wet-pulverized with a ball mill. Dry powder obtained by evaporating and drying the ground slurry,
Add 1% organic binder (polyvinyl alcohol)
After sizing, the mixture was formed into a column having a diameter of 16 mm and a height of 8 mm at a pressure of 1.5 ton / cm ² . The obtained molded body was fired in the atmosphere at a temperature shown in Table 2 (range of 900 to 1060 ° C.) for 2 hours to obtain a cylindrical sintered body.

[Evaluation of High-Frequency Characteristics] (1) Using the cylindrical sintered body obtained by the above method, the relative dielectric constant (ε _r ) and f · Q value by the short-circuited cylindrical resonator method at both ends.
(f = 5 to 6 GHz) was measured. Since the Q value changes according to the measured resonance frequency, it is represented by an fQ value which is substantially unaffected by the frequency.

(2) The resonance frequency of the TE01δ mode is measured in the temperature range of −25 to 85 ° C., and the temperature coefficient (τ _f ) of the resonance frequency is determined based on the rate of change based on the resonance frequency at 25 ° C.
Was calculated.

[Preparation of Ag Diffusion Evaluation Sample Having Internal Ag Electrode]
A dry powder obtained by mixing raw materials other than ₂ O ₃ , calcining, and adding and mixing B ₂ O ₃ was added to an organic solvent containing xylene as a main component in an amount of about 70% and a plasticizer of about 3%. And about 7.5% of a binder (polyvinyl butyral), and slurried. Using this slurry, the doctor blade method
A green sheet obtained by forming a sheet to a thickness of 100 μm and drying was cut into a piece of 30 mm × 30 mm.

An Ag paste for forming an internal electrode was screen-printed on a part of the cut green sheet. The Ag paste was printed so that a rectangular electrode of 2 mm × 1 mm was formed on one sheet, with a vertical and horizontal space of 2 mm each, and formed in 5 rows and 5 columns. Printing thickness of Ag paste is 20 ± 2μm
Met. Four unprinted green sheets are laminated on the upper and lower sides of the green sheet on which the Ag paste is printed, respectively, and thermocompression-bonded at 90 ° C. and 100 kgf / cm ² . It was calcined in the air at the same temperature for 2 hours.

A dielectric ceramic sample having an internal electrode of Ag obtained by firing was cut at a position where the cross section of the internal electrode could be observed, the cut surface was polished, and the state of Ag diffusion was observed by SEM. Specifically, when the Ag of the electrode diffuses into the surrounding dielectric porcelain, the trace of the diffused Ag becomes a gap, and a cavity is formed around the electrode. When this cavity was formed, it was determined that Ag diffusion occurred. Table 2 shows the test results together with the firing temperature.

[0042]

[Table 1]

[0043]

[Table 2]

As can be seen from Table 2, according to the present invention,
By firing at a low temperature of 960 ° C or less, which can be fired simultaneously with Ag, the relative dielectric constant is moderately high, about 30 to 36, and the f · Q value is 8000.
GHz or higher, temperature coefficient of resonance frequency (τ _f ) ± 30
Dielectric porcelain having sufficiently excellent electrical characteristics in a high frequency band of several GHz or more, which is as low as ppm / ° C. or less, was obtained, and furthermore, diffusion of Ag during firing was suppressed.

[0045]

The dielectric porcelain composition according to the present invention has an appropriately high relative dielectric constant and a large Q (that is, the dielectric loss of the material).
A dielectric porcelain having characteristics required for a dielectric porcelain used in a high frequency band of several GHz or more such that the tan δ is low and the temperature coefficient of the resonance frequency is small.

Further, the dielectric ceramic composition has a low-temperature sintering property that sinters at a temperature (900 to 960 ° C.) lower than the melting point of low-resistance metal, particularly the best conductor but low-melting point Ag. During the firing, the diffusion of Ag into the dielectric porcelain is suppressed. Therefore, in some cases, the firing temperature is just below the melting point of Ag, but it is still possible to fire simultaneously with the Ag internal conductor. As a result, it is possible to provide a dielectric laminated component having excellent electrical characteristics in a high frequency band by using the Ag internal electrode with a small conductor loss, and to reduce the size and performance of the distributed constant circuit type dielectric ceramic component. To contribute.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G031 AA06 AA11 AA25 AA26 AA27 AA28 AA30 AA39 BA09 CA03 GA01 GA11 5G303 AA02 AA10 AB06 AB08 AB11 AB15 BA12 CA01 CB02 CB03 CB11 CB30 CB35 CB38 CB42 DA01

Claims (3)

[Claims] The present invention relates to 100 parts by weight of a main component represented by the following composition formula: BaO. (Axy) TiO ₂ .xGeO ₂ + ySiO ₂ [where 4.0 ≦ a ≦ 4.6 0.15 ≦ x + y ≦ 0.8 0.2 ≦ x / (x + y)] against, as an auxiliary component, 0.5 to 2 parts by weight of Zn and Cu in terms of CuO in a proportion of 0.3 to 2 parts by weight of 0.5 to 4 parts by weight B in terms _of B ₂ O ₃ in terms of ZnO, and ZnO equivalent amount ≧ CuO equivalent
A dielectric porcelain composition comprising: 2. A laminated dielectric porcelain component comprising the dielectric porcelain composition according to claim 1 and having an Ag internal electrode co-fired therewith. 3. An oxide of at least Ba, Ti and Ge,
Containing a composite oxide and / or a precursor compound thereof,
Calcining the raw material powder mixture containing no B compound at a temperature of 950 to 1150 ° C., adding the remaining component oxides, composite oxides, and / or precursor compounds thereof, and molding; A method for producing a dielectric porcelain comprising the composition according to claim 1, comprising a step of firing at a temperature of 960 ° C or lower.