KR101849470B1 - Low temperature co-fired microwave dielectric ceramics and manufacturing method thereof - Google Patents

Abstract

Disclosed are microwave dielectric ceramics for low temperature sintering and a manufacturing method thereof. The microwave dielectric ceramics for low temperature sintering by the present invention has composition formula, Ca[(Li_(1/3)Nb_(2/3))_0.8Ti_0.2]O_(3-δ)+x(ZnO·B_2O_3·SiO_2·BaO·CaCO_3). (In this case, the x is 5-30 wt%, preferably 10-20 wt%, of the total weight of a dielectric ceramics composition) The microwave dielectric ceramics manufactured by the above composition can be applied with a thick film process by enabling co-sintering with an internal conductive metal by enabling a low temperature sintering which is lowered to 850-900°C and has a promising application as low temperature co-sintering ceramics (LTCC) by having excellent microwave dielectric properties since the maximum value of a permittivity (ε_r) is about 40.1, the maximum value of a quality factor (Q×f) is about 7,059 GHz, and the minimum value of a temperature factor (τ_f) of resonance frequency is about -1 ppm/°C.

Description

TECHNICAL FIELD [0001] The present invention relates to a microwave dielectric ceramic for low temperature sintering, and a method of manufacturing the same. BACKGROUND ART [0002]

The present invention relates to microwave dielectric ceramics for low temperature sintering and a method of manufacturing the same, and more particularly, to microwave dielectric ceramics capable of low temperature sintering and having excellent microwave dielectric properties and a manufacturing method thereof.

In order to miniaturize high-frequency devices such as microwave filters, duplexers, resonators, and antennas, which are core components of these devices, and to make them more compact, lighter, and more surface-mountable as the mobile communication and Bluetooth markets continue to expand, It is essential.

Dielectric ceramics used as a material of such a high-frequency device generally require the following microwave dielectric characteristics.

First, since the microwave wavelength inside the dielectric ceramics is shortened in inverse proportion to the 1/2 power of the dielectric constant, the dielectric constant ( _r ) must be large for miniaturization of the microwave device.

Second, for the operation of high efficiency and large dielectric loss, the value of the reduced quality factor (Q) in the operating frequency band, typically this quality factor is a value with gopin Q · f ₀ value of the resonant frequency (f ₀₎ .

Third, it is preferable that the temperature coefficient (TCF: τ _f ) of the resonance frequency has a value close to 0 as possible for precise and stable operation of the operating frequency.

Particularly, in order to realize the above lamination, the dielectric ceramics are formed from a green sheet and then printed, laminated and sintered with patterns of the internal electrodes. Generally, the conductors of such internal electrodes are excellent in conductivity, The low temperature of Ag or Cu is used for the dielectric ceramics. The dielectric ceramics in the process are sintered simultaneously with these conductors.

Therefore, the dielectric ceramic used should be a low firing temperature, so the above temperature, while at the same time a good dielectric constant (ε _r) and a high quality factor (Q · f _0), and the temperature coefficient of the lowest resonant frequency (τ _f) to possess so-called superior to And should be low temperature co-fired ceramics (LTCC).

For this purpose, dielectric ceramics capable of low-temperature sintering have been developed until recently, but most of them are inferior in densification at low temperature sintering, degradation of dielectric constant due to addition of sintering, degradation of quality factor, Is greatly reduced.

One example of the low-temperature co-sintered ceramics developed so far is a BiNbO ₄ composition in which ZnO, B ₂ O ₃ , CuO, V ₂ O ₅ and the like are added. The composition has a good Q · f ₀ Value and permittivity (? _R ), but the operation is unstable due to the large temperature coefficient (? _F ) of the resonance frequency, which is problematic in practical application (Kagata H. et al., Jpn. J. Appl. Phys. 31, 3152 1992).

As another example, it has a microwave dielectric property with a Q · f ₀ value of at least 14,000 GHz, a dielectric constant (∈ _r ) of 41 to 46 and a temperature coefficient of resonance frequency (τ _f ) of ≤10, (Li _{1 /} 3Nb _2/3 ) _0.8 Ti _0.2 ] O _{3 -δ} (so-called CLNT) ceramics composition, which is disadvantageous in that it has a disadvantage that it is a high point that is high.

Since such a CLNT ceramics composition can not be sintered at a low temperature due to high sintering temperature, B ₂ O ₃ and Bi ₂ O ₃ are added to this composition (H. Ogawa et al., Journal of the European Ceramic Society, pp. 1761-1764 (Li George et al., Journal of Alloys and Compounds, pp. 336, 2004), or by adding lithium borosilicate (LBS) glass and lithium magnesium zinc borosilicate (LMZBS) (2003)), there have been many attempts to lower the sintering temperature of the high-temperature CLNT composition to a low temperature of about 950 ° C.

Disclosed is a microwave dielectric ceramics for low temperature sintering which is capable of low temperature sintering and has good microwave dielectric properties, and a method for producing the same.

In order to achieve the above object, a dielectric ceramic composition according to one aspect of the present invention comprises Ca [(Li _1/3 Nb _2/3 ) _0.8 Ti _0.2 ] O _{3 -δ} and ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ And may be a dielectric ceramics composition constituting a solid solution including glass.

At this time, the content of the glass may be in the range of 5 to 30 wt%, more preferably in the range of 10 to 20 wt%, based on the total weight of the dielectric ceramic composition.

In addition, the glass is preferably composed of 50 to 70 wt% of ZnO, 20 to 30 wt% of B ₂ O ₃ , 2 to 10 wt% of SiO ₂ , BaO> 0 and ≤10 wt% of CaO ₃ > 0 and ≤10 wt % ≪ / RTI > More preferably, the glass comprises 50 to 65 wt% of ZnO, 20 to 25 wt% of B ₂ O ₃ , 5 to 10 wt% of SiO _2, 5 to 10 wt% of BaO, and 5 to 10 wt% of CaCO _{3 based on} the total weight of the glass % ≪ / RTI >

A method for producing a dielectric ceramic composition according to another aspect of the present invention is a method for producing a dielectric ceramics composition _containing Ca, Ca, and Ca according to the composition formula Ca [(Li _1/3 Nb _2/3 ) _0.8 Ti _0.2 ] O _{3 -δ} Li, Nb, and Ti oxide powder and calcining to synthesize a CLNT powder; and mixing the synthesized CLNT powder with ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ Mixing and molding the glass powder to form a molded product, and sintering the molded product at a temperature ranging from 850 to 950 캜 to form a solid solution.

At this time, the glass powder may be mixed into the synthesized CLNT powder in a range of 5 to 30 wt%, preferably 10 to 20 wt%, based on the total weight of the dielectric ceramic composition.

According to the present _{invention, Ca [(Li 1/3 Nb 2/3} ) 0.8 Ti 0.2] O 3 -δ ceramics of low-melting-point glass composition _{ZnO · B 2 O 3 · SiO} 2 · BaO · low-melting-point consisting of CaCO ₃ It has excellent microwave dielectric properties with good Q · f ₀ value and permittivity (ε _r ) while having a good temperature coefficient (τ _f ) while being capable of low temperature sintering by adding a glass composition and thus being applied as low temperature co-sintered ceramics (LTCC) This promising dielectric ceramic composition is provided.

1A to 1C are electron micrographs, wherein FIG. 1A is a photograph of the microstructure of Example 3 of the present invention, FIG. 1B is Example 10 of the present invention, and FIG. 1C is a photograph of each microstructure of Example 17 of the present invention.

As described above, although the composition of Ca [(Li _1/3 Nb _2/3 ) _0.8 Ti _0.2 ] O _{3 -δ} (hereinafter referred to as "CLNT") has excellent microwave dielectric properties, It is impossible to co-fuse with a conductor metal by itself.

However, according to the present invention, ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ , which is a low melting point glass, is added to the CLNT composition to maintain the original excellent microwave dielectric properties to a certain extent, , Preferably from 850 to 900 캜.

As described above, the composition of the present invention can be sintered at a low temperature so that simultaneous sintering with an internal conductor metal is possible, while the maximum value of the permittivity ( _r ) is about 40.1, the maximum value of the quality factor (Q · f) is about 7,059 GHz, Since the minimum value of the temperature coefficient of frequency (τ _f ) has microwave dielectric properties as good as about -1 ppm / ° C., application as low temperature co-sintered ceramics (LTCC) is promising.

In the composition of the present invention, the addition amount of ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ glass as described above is 5 to 30 wt%, preferably 10 to 20 wt%, based on the total weight of the composition of the present invention.

In addition, the above-mentioned ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ Wherein the content of ZnO is in the range of 50 to 70 wt%, the content of B ₂ O ₃ is in the range of 20 to 30 wt%, the content of SiO ₂ is in the range of 2 to 10 wt%, the content of the BaO content of> 0, the content of ≤10wt%, the CaCO ₃ is> 0 and ≤10wt%. More preferably, the ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ Wherein the content of the ZnO, the content of the B ₂ O _{3, and} the content of the SiO ₂ in the glass are 50 to 65 wt%, 20 to 25 wt%, 5 to 10 wt%, respectively, relative to the total amount of the glass, The content is 5 to 10 wt%, and the content of CaCO ₃ is 5 to 10 wt%.

Hereinafter, preferred embodiments of the present invention will be described in more detail. However, the following embodiments of the present invention are provided to facilitate an understanding of the present invention, and the present invention is not limited to the following embodiments.

Example

First, as a comparative example, solid phase reaction was carried out using CaCO ₃ (purity of 99%), Li ₂ CO ₃ (purity of 99%), Nb ₂ O ₅ (purity of 99.9%) and TiO ₂ To prepare specimens. Powder having a basis weight of Ca [(Li _1/3 Nb _2/3 ) _0.8 Ti _0.2 ] O ₃ -δ ("CLNT") was ball milled with a solvent of zirconia balls for 24 hours. The mixed powder was dried in an oven at 100 ° C for 24 hours and calcined at 975 ° C for 4 hours. The synthesized powders were mixed with 3wt% of PVA and sintered at 1175 ℃ for 2 hours to prepare CLNT ceramics.

Meanwhile, in Examples 1 to 21 of the present invention, ZnO · B ₂ O ₃ , which was prepared according to Table 1 below as an additive, was added to the CLNT ceramics composition powder calcined in the above Comparative Example in order to lower the sintering temperature of the above CLNT ceramics SiO ₂ BaO CaCO ₃ Glass was added in an amount of 10 to 20 wt% and ball milled for 24 hours. Then, in the same manner as in the above comparative example, the same process was performed by drying and calcining, and the same amount of PVA was mixed. Thereafter, this powder was uniaxially pressed at a pressure of 1 ton / cm 2 to form a 10 mm thick, 4 to 5 mm thick, and then sintered at 850 to 900 ° C for 2 hours to prepare the inventive ceramics.

The surfaces of the specimens of the comparative examples and the examples thus prepared were polished, and then the dielectric constant (ε _r ), the Q · f _o value and the temperature coefficient (τ _f ) of the resonance frequency were measured by a parallel conductor plate method. The measured frequency was 9 to 11 GHz, and the measurement temperature range of the temperature coefficient (? _F ) of the resonance frequency was 25 to 80 占 폚. The microwave dielectric properties of each specimen thus measured are summarized in Table 1.

Additive content
(wt%) In additive
Content of each component (wt%) Sintering
Temperature
(° C) density
(g / cm3) permittivity
( _r ) Q · f ₀
(GHz) τ _f
(ppm / DEG C) ZnO B ₂ O ₃ SiO ₂ BaO CaCO ₃ Comparative Example 0 0 0 0 0 0 1175 4.11 41.4 17,600 -18 Example 1 10 50 20 10 10 10 875 4.07 39.8 4619 -8.5 Example 2 10 55 25 10 5 5 875 4.09 39.9 7059 -5.2 Example 3 10 60 20 10 5 5 875 4.05 37.7 3338 -6.7 Example 4 10 65 20 5 5 5 875 4.02 40.1 5561 -8.9 Example 5 10 68 30 2 - - 900 4.06 40.2 6574 -One Example 6 10 70 28 2 - - 900 3.98 39.1 3896 5.2 Example 7 10 55 25 10 - - 900 3.94 26.5 3804 -4.8 Example 8 15 50 20 10 10 10 875 4.13 40.1 4869 -1.5 Example 9 15 55 25 10 5 5 875 4.11 37.1 4400 2.1 Example 10 15 60 20 10 5 5 875 4.09 20.2 5213 -9.8 Example 11 15 65 20 5 5 5 875 4.12 25.2 4254 -5.9 Example 12 15 68 30 2 - - 900 4.08 38.3 5275 3.8 Example 13 15 70 28 2 - - 900 4.09 35.3 4264 -10.4 Example 14 15 55 25 10 - - 875 4.05 32.5 3925 5.2 Example 15 20 50 20 10 10 10 850 4.15 25.1 4520 8.4 Example 16 20 55 25 10 5 5 850 4.13 32.4 3900 6.5 Example 17 20 60 20 10 5 5 850 4.15 28.9 4200 -2.5 Example 18 20 65 20 5 5 5 850 4.16 25.3 5231 8.2 Example 19 20 68 30 2 - - 875 4.07 34.5 4520 9.5 Example 20 20 70 28 2 - - 875 4.13 25.5 3305 10.2 Example 21 20 55 25 10 - - 875 4.10 23.1 3536 11.5

1A to 1C are electron micrographs, and FIG. 1A is a microstructure photograph of Example 3, FIG. 1B is Example 10, and FIG. 1C is a microstructure photograph of Example 17. FIG. As can be seen from these microstructure photographs and the sintered density values in Table 1, Examples 1 to 21 of the present invention show that the sinterability is good at a low temperature of 850 to 900 ° C.

In particular, as shown in Table 1, ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ The glass compositions of this example had a lower quality factor (Q · f) value as compared to the comparative example without additive, but instead had a significantly reduced sintering temperature of comparative example of 1175 ° C at 850-900 ° C Lt; / RTI > Further, in this embodiment the composition of the dielectric constant (ε _r) the maximum value of about 40.1, and the minimum value of the quality factor (Q · f), the maximum value of about 7,059GHz, the temperature coefficient of the resonant frequency of the (τ _f) of about -1ppm / [Deg.] C.

As described above, according to the present invention, by adding ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ , which is a low melting point glass, to the CLNT composition, the composition according to the present invention exhibits excellent inherent microwave dielectric properties The sintering temperature can be lowered to 950 占 폚 or lower, preferably 850 to 900 占 폚, so that it can be very advantageously applied as low-temperature co-sintered ceramics (LTCC).

Meanwhile, the dielectric characteristics of the preferred embodiments of the present invention described above are somewhat different within the usual tolerance range depending on the powder characteristics such as average particle size, distribution and specific surface area of the composition powder, purity of the raw material, It will be appreciated by those skilled in the art that variations may be present.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. , Additions and the like are to be regarded as belonging to the claims.

Claims (8)

A dielectric ceramics composition comprising a solid solution of Ca [(Li _1/3 Nb _2/3 ) _0.8 Ti _0.2 ] O _{3 -δ} ceramics composition to which ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ glass is added. The method according to claim 1,
Wherein the content of the glass is in the range of 5 to 30 wt% based on the total weight of the dielectric ceramic composition. The method according to claim 1,
Wherein the glass content is in the range of 10 to 20 wt% based on the total weight of the dielectric ceramic composition. 4. The method according to any one of claims 1 to 3,
Wherein the glass comprises components in the following content (wt%) relative to the total weight of the glass.
ZnO 50-70;
B₂O₃ 20 to 30;
SiO₂ 2 to 10;
BaO > 0 and? 10; And
CaCO₃ > 0 and ≤10. 4. The method according to any one of claims 1 to 3,
Wherein the glass comprises components in the following content (wt%) relative to the total weight of the glass.
ZnO 50 to 65;
B₂O₃ 20 to 25;
SiO₂ 5 to 10;
BaO 5 to 10; And
CaCO₃ 5 to 10. Li, Nb and Ti oxide powders were mixed and calcined according to the composition formula Ca [(Li _1/3 Nb _2/3 ) _0.8 Ti _0.2 ] O _{3 -δ} (hereinafter referred to as "CLNT") to synthesize CLNT powder ;
The synthesized CLNT powder was mixed with ZnO · B ₂ O ₃ · SiO ₂ · BaO · CaCO ₃ Mixing and molding the glass powder to form a molded product;
And sintering the molded product at a temperature in the range of 850 to 950 캜 to form a solid solution. The method according to claim 6,
Wherein the glass powder is mixed with the synthesized CLNT powder in a range of 5 to 30 wt% based on the total weight of the dielectric ceramic composition. The method according to claim 6,
Wherein the glass powder is mixed with the synthesized CLNT powder in a range of 10 to 20 wt% based on the total weight of the dielectric ceramic composition.

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