KR20230072621A - Dielectric ceramics composition for high frequency device, method of controlling microwave properties of the same, ceramic substrate thereby and manufacturing method thereof - Google Patents

Abstract

The present invention has a composition of the composition formula (Na _{1 - x} K _x ) ₂ MoO ₄ (wherein, the x is greater than 0 and is in the range of 0.2 mole or less), Au, Ag, Cu, Al, etc. While co-firing with general metal material electrode patterns including, having good permittivity (ε _r ) and dielectric loss (tan δ) and particularly excellent microwave dielectric properties of resonant frequency temperature coefficient (τ _f ), excellent thermal conductivity (κ) Disclosed is a dielectric ceramic composition for a high-frequency device having so-called ultra-low temperature co-fired ceramics (uLTCC) composition, which also has properties. The ceramic composition of the present invention can be co-firing with general metal material electrode patterns including Au, Ag, Cu, Al, etc. at a very low temperature of about 650 ° C or less, and is promising for application as a substrate for a high-frequency device.

Description

Dielectric ceramic composition for high-frequency elements, method for controlling microwave dielectric properties thereof, and ceramic substrate using the same, and method for manufacturing the same

The present invention relates to a dielectric ceramic composition for high-frequency elements, in particular, at a very low temperature of about 650 ° C. or less, co-firing with metal electrodes of a low melting point such as Al is possible, enabling lamination of high-frequency elements, while having good properties in the microwave frequency band. The present invention relates to a dielectric ceramic composition for high-frequency devices, which has excellent microwave dielectric properties such as permittivity (ε _r ) and dielectric loss (tan δ), and, above all, highly stable resonant frequency temperature coefficient (τ _f ) and excellent thermal conductivity (κ). .

In addition, the present invention relates to a method for controlling microwave dielectric characteristics including a resonant frequency temperature coefficient (τ _f ) and thermal conductivity (κ) of the dielectric ceramic composition for a high frequency element.

In addition, the present invention relates to a ceramic substrate using the dielectric ceramic composition for a high-frequency device and a method for manufacturing the same.

Recently, there is an increasing demand for layering technology capable of realizing surface mounting of high-frequency elements such as microwave filters, duplexers, resonators, and high-frequency integrated circuit boards, which are core parts of mobile communication devices.

In general, these high-frequency devices have a structure in which a high-frequency integrated circuit composed of microwave transmission lines is printed on a dielectric ceramic substrate. Therefore, the electrical characteristics of the high-frequency device are mainly influenced by the microwave dielectric characteristics of the dielectric ceramic itself constituting the substrate. The microwave dielectric properties of these dielectric ceramics generally require the following conditions (i) to (iii) to be satisfied:

(i) First, in order to increase the transmission speed of the high-frequency circuit, the dielectric constant (ε _r ) of dielectric ceramics is required to be small.

(ii) On the other hand, for the high-efficiency operation of the high-frequency circuit, the dielectric loss of the dielectric ceramics is small in the operating frequency band, so the value of the quality factor (Q) must be high, in other words, the value of the dielectric loss (tanδ), which is its reciprocal It should be small. Usually, the quality factor is evaluated as a value of Q×f, which is a product of this value and the corresponding resonance frequency (f), or evaluated as a dielectric loss value that is the reciprocal of the quality factor.

(iii) Lastly, for precise and stable operation of the high frequency circuit, a temperature coefficient of resonance frequency (T Coefficient: τ _f ) is required to be as small as possible. In general, the allowable range of the temperature coefficient (τ _f ) required when applied to a typical antenna resonator or filter is within approximately ±10 ppm/°C.

On the other hand, lamination of high-frequency devices is achieved by printing and stacking electrode patterns of general metal materials such as Au, Ag, Cu, and Al on a green sheet of dielectric ceramics, and co-firing together with these electrode patterns.

For this co-firing, when the electrode pattern is a metal material of Au, Ag, or Cu, so-called low-temperature co-fired ceramics that can be sintered at a temperature in the range of about 850 to 1000 ° C. ceramics: "LTCC") must be used.

In particular, as the electrode pattern, in order to use an Al metal material that is advantageous because it is cheaper than the Au, Ag, and Cu metal materials but has a relatively lower melting point instead, co-firing with such an Al electrode is required. For this purpose, so-called ultra-low temperature co-fired ceramics (“uLTCC”), which can be sintered at a lower temperature of about 650° C. or lower, must be used.

Compared to the conventional hybrid integrated circuit process in which a ceramic substrate is first fired, then each electrode is printed, and then additionally heat-treated, the ceramic green sheet on which the electrode is printed is heat-treated at once, so the process yield is high. And high element integration and easy manufacturing method are advantages, and in particular, it is very advantageous to apply a nano-metal electrode paste obtained by converting a conventional micron-sized metal material electrode powder into a nano-size.

As a prior art related to dielectric ceramics for LTCC high-frequency devices, a series of microporous structures are formed by adding polymer spheres, carbon powder or fiber, graphite powder, etc. to a dielectric substrate material and dissipating these organic materials by molding and heat treatment. A method of lowering the dielectric constant to about 5.6 due to air (permittivity of 1) accommodated therein has been proposed (hereinafter "Prior Art Document" 1). However, in this case, the roughness of the surface of the dielectric substrate becomes rough due to the inclusion of the graphite, and irregular channels are formed due to the presence of open pores, so the dielectric loss is rather large and the Q×f value is poor.

As another prior art, hollow or porous silica glass spheres are added to a glass-ceramic LTCC containing alumina or mullite, but the silica spheres are coated with a ceramic material, thereby recrystallizing the silica spheres and the resulting glass ceramic layer A method of improving the resonant frequency temperature coefficient (τ _f ) by reducing the rapid thermal expansion of has been proposed ("Prior Art Document" 2 below). However, in this case, pores are exposed on the surface of the substrate during polishing of the substrate, resulting in increased surface roughness. To prevent this, an additional process of re-coating the surface of the polished substrate with a glass ceramic layer not containing a porous material is required. It is very inefficient and increases the manufacturing cost.

As another prior art, a technique of making a part of the surface of an LTCC substrate porous by chemical etching has been proposed ("Prior Art Document" 3 below). However, this method is also structurally weak when the surface is rough and the etching depth is large, and when the conductive layer is formed on the substrate, the electrical insulation is weakened due to open pores, and the dielectric constant (ε _r ) of the dielectric layer is initially It is difficult to apply it as an actual circuit board because it is not implemented as designed.

As another prior art, a technique of lowering the apparent dielectric constant (ε _r ) to about 6.6 has been proposed by manufacturing a substrate of a hybrid structure in which a low dielectric constant polymer, for example, polyimide/glass bubble layer is coated on an LTCC substrate (see below). "Prior Art Literature" 4). By the way, there is no problem if this is a dummy layer without any electrode circuit layer inside the previously sintered LTCC substrate, but when applied to a structure with an interconnector including an electrode circuit layer inside the substrate, the polymer layer added to the LTCC layer and It is difficult to form an electrical contact and an additional process is required to solve it.

As described above, the conventional technologies proposed for low-temperature co-fired ceramics (LTCC) are still difficult to effectively put to practical use, and furthermore, the technology proposed for co-fired ceramics (uLTCC) requiring simultaneous firing at a lower temperature than the LTCC is almost non-existent. am.

Therefore, with a simple structure and manufacturing process, co-firing of metal electrodes and ultra-low temperatures is possible, while excellent microwave dielectric properties of low permittivity (ε _r ), low dielectric loss (tan δ), and low temperature coefficient (τ _f ) of stable resonant frequency. In addition to the characteristics, the development of ultra-low temperature co-fired ceramics (uLTCC) material having excellent thermal conductivity is required.

Furthermore, these materials enable energy savings due to the ultra-low temperature manufacturing process, cost reduction of raw materials due to compatibility with non-metallic electrodes, and expansion of compatibility with other materials.

1. B. Synkiewicz et al., Acta Physica Polonica A, vol.134, no.1, p.322 (2018)

2. US Patent Publication No. 5593526 (published on January 14, 1997)

3. Achim Bittner et al., Proc. Eurosensors XXIV, September 5-8 (2010)

4. Achim Bittneret et al., Microelectronic Engineering 88, p.2977 (2011)

Therefore, the present invention is a high-frequency device that can be sintered at a very low temperature of about 650 ° C or less and has good dielectric constant (ε _r ) and dielectric loss (tan δ) in the microwave frequency band, particularly stable resonant frequency temperature coefficient (τ _f ) and excellent thermal conductivity. It is to provide a dielectric ceramic composition and a method for controlling microwave dielectric properties of the composition, and to provide a ceramic substrate and a method for manufacturing the ceramic substrate thereby.

A dielectric ceramic composition for a high-frequency device according to an aspect of the present invention for solving the above problems is a dielectric ceramic composition for a high-frequency device, and is represented by the composition formula (Na _{1 -x} K _x ) ₂ MoO ₄ , but the x in the composition formula is 0 It has a composition in the range of greater than 0.2 moles or less.

At this time, optionally, the x of the composition formula may be in the range of 0.01 to 0.2 moles.

Optionally, the dielectric ceramic composition for a high-frequency device may be a composition that is sintered at 650° C. or less to form a solid solution.

On the other hand, in the method for controlling the microwave dielectric characteristics of a dielectric ceramic composition for a high frequency element according to another aspect of the present invention, in the dielectric ceramic composition for a high frequency element, the microwave dielectric characteristic is a resonance frequency temperature coefficient (τ _f ) value And at least one of a thermal conductivity (κ) value, wherein the dielectric ceramic composition has an α phase of a cubic crystal structure and a β phase of an orthorhombic crystal structure coexisting therein, and by changing the value of x within the above range in the composition formula. The microwave dielectric characteristics are controlled by controlling the relative fraction of the α phase and the β phase inside the dielectric ceramic composition and by adjusting the degree of phase transition from the α phase to the β phase.

On the other hand, in the method for controlling the microwave dielectric characteristics of a dielectric ceramic composition for a high-frequency device according to another aspect of the present invention, the microwave dielectric characteristics are the resonant frequency temperature coefficient (τ _f ) value and the thermal conductivity (κ) value At least one of, wherein the α phase of the cubic crystal structure and the β phase of the orthorhombic crystal structure coexist inside the dielectric ceramic composition, and by changing the sintering temperature of the dielectric ceramic composition, the α phase and the α phase and the The microwave dielectric properties are controlled by adjusting the relative fraction of the β phase and adjusting the degree of phase transition from the α phase to the β phase.

At this time, optionally, the sintering temperature of the dielectric ceramic composition may be adjusted within a temperature range of 525 to 625 °C.

On the other hand, a ceramic substrate for a high frequency element according to another aspect of the present invention includes the dielectric ceramic composition for a high frequency element and a metal electrode disposed on a surface of the dielectric ceramic composition.

On the other hand, a method for manufacturing a ceramic substrate for a high-frequency device according to another aspect of the present invention includes the following steps (i) to (iii):

(i) forming a single or a plurality of green tapes from the slurry of the dielectric ceramic composition;

(ii) disposing a metal electrode on the surface of the single green tape, or disposing a metal electrode on the surface of at least one of the plurality of green tapes and then laminating the plurality of green tapes to form a green tape stack. ; and

(iii) co-firing the single green tape or the green tape laminate together with the metal electrode in a temperature range of 650° C. or less.

In this case, optionally, the material of the metal electrode may be one or more of Au, Ag, Cu, and Al.

Also, optionally, the temperature range for the co-firing may be in the range of 575 to 600°C.

The (Na,K) ₂ MoO ₄ ceramic composition of the present invention is an ultra-low temperature co-fired ceramic (uTCC), and maintains good dielectric constant (ε _r ) and dielectric loss (tan δ) in the microwave frequency band while the sintering temperature is lowered to about 650 ° C or less. do. In particular, the composition of the present invention causes a phase transition between two unique phases having different structures coexisting in the composition and implements a self-temperature compensation mechanism that controls the degree of the phase transition, thereby increasing the resonant frequency temperature coefficient (τ _f ) and thermal conductivity (κ) are greatly improved. In addition, the sintering temperature of the ceramic composition of the present invention in the ultra-low temperature region is not only lower than the temperature of the Al material electrode having the lowest melting point (660 ° C) among the general metal materials, but also has no chemical reaction with Al. Co-firing with the Al material electrode is possible, so it can be put into practical use as a substrate for high-frequency devices with compatibility.

1 is a sintered body of a composition obtained by firing at a very low temperature in a temperature range of 525 to 625° C. while changing the substitution amount of K from 0 mol to 0.2 mol in a (Na _{1 - x} K _x ) ₂ MoO ₄ composition according to an embodiment of the present invention. In Figure 1, (a) is a composition sintered body with x = 0 mole, (b) is a composition sintered body with x = 0.1 mole, (c) is each X-ray diffraction pattern of the composition sintered body with x = 0.2 mole am.
Figure 2 shows the X-ray diffraction pattern data of the sintered body of the composition fired at 575 ° C., respectively, in (a) to (c) of FIG. As a result of processing by Rietveld's refinement in consideration of the pattern, (d) in FIG. 2 is in (a) in FIG. 1, (e) is in (b) in FIG. 1, and (f) is in FIG. Each resultant pattern corresponding to (c) of 1.
3 is a solid solution by changing the substitution amount of K from 0 mol to 0.2 mol in the (Na _{1 - x} K _x ) ₂ MoO ₄ composition according to an embodiment of the present invention and firing it at a very low temperature in the temperature range of 525 to 625 ° C. Showing the results of microstructure analysis by FE-SEM / EDS of the composition sintered body, in FIG. 3 (a1) to (a5) correspond to (a) in FIG. ) corresponds to FIG. 1 (b) and x = 0.1 mole of the composition sintered body, (c3) to (c5) correspond to FIG. , Inside each SEM picture, each particle distribution histogram and average particle size graph are inserted and shown, and the pictures (C1) to (c2) disposed at the bottom of the picture (c5) are EDS for some tissues in the picture (b3). is the result of the analysis.
4 to 7 show changes in microwave dielectric properties and thermal conductivity according to changes in K substitution amount (mol) and sintering temperature [T (℃)] of (Na,K) ₂ MoO ₄ compositions according to embodiments of the present invention. As graphs, FIG. 4 shows the change in dielectric constant (ε _r ), FIG. 5 shows the change in dielectric loss (tanδ), FIG. 6 shows the change in the resonance frequency temperature coefficient (τ _f ), and FIG. 7 shows the change in thermal conductivity (κ). ), respectively, and in FIGS. 4 to 7, x represents the K substitution amount x (mol) in (Na _{1 - x} K _x ) ₂ MoO ₄ of Formula 1 above.

The present invention is capable of co-firing with general metal material electrode patterns including Au, Ag, Cu, Al, etc. at a very low temperature of about 650 ° C or less, and has good dielectric constant (ε _r ) and dielectric loss (tan δ) and particularly excellent resonance frequency. To provide so-called ultra-low temperature co-fired ceramics (“uLTCC”) compositions that have microwave dielectric characteristics of temperature coefficient (τ _f ) and also have excellent thermal conductivity (κ) characteristics, This composition first uses NaMoO ₄ ceramics as a starting composition.

According to the present inventors, these NaMoO ₄ ceramics have generally low dielectric constant and dielectric loss values, but are good, but the resonant frequency temperature coefficient (τ _f ) has been investigated to reach a very large value of about -76ppm/℃, which is a high frequency element It is still unsuitable for use. As described above, in order to be applied as a general antenna resonator or filter, it is generally required that the tolerance range of the resonance frequency temperature coefficient (τ _f ) be controlled within approximately ±10 ppm/°C.

In addition, according to the present inventors, it was investigated that the NaMoO ₄ ceramics had a very low room temperature thermal conductivity (κ) of about 1 W/m·K. In general, when applied to high-frequency devices, it is desirable to have high thermal conductivity (κ) in order to solve the heat generation phenomenon of communication modules due to ultra-high frequency and integration, and conventional low temperature co-fired ceramics (low temperature co-fired ceramics: "LTCC") is in the range of approximately 1.2 to 1.5 W/m K.

Accordingly, the present inventors have significantly improved the resonant frequency temperature coefficient (τ _f ) and thermal conductivity (κ) characteristics, which were poor as described above, by substituting a small amount of K with Na at the A-site of NaMoO ₄ ceramics, which is the starting composition. ₂ MoO ₄ ceramics were developed.

In the present invention, the increase in the resonance frequency temperature coefficient (τ _f ) and thermal conductivity (κ) characteristics, as described below, is due to the K substituent intervening in the NaMoO ₄ ceramics, the phase composition, crystal structure and microstructure of the ceramics composition. This is effectively achieved by implementing a so-called self-temperature compensation mechanism that finely controls the structure. In particular, this self-temperature compensation mechanism is a phenomenon that could not be observed in conventional LTCC or uLTCC single compositions known to date.

The mechanism of the present invention keeps the permittivity and dielectric loss of the starting composition NaMoO ₄ good, while greatly reducing the resonant frequency temperature coefficient (τ _f ) to about -3pm/℃ and increasing the thermal conductivity (κ) to a maximum of 1.8 Significantly increase to about W/m K.

As a result, the (Na,K) ₂ MoO ₄ ceramic composition of the present invention achieves a very low resonant frequency temperature coefficient (τ _f ) value, thereby achieving stable operating characteristics when applied to a high-frequency device, as well as improved thermal conductivity (κ ), it can effectively dissipate heat from the communication module, so it can be effectively applied as a high-frequency device.

In addition, the (Na,K) ₂ MoO ₄ ceramic composition of the present invention can be co-fired with an electrode pattern of a general metal material including Au, Ag, Cu, Al, etc. at a very low temperature of about 650 ° C or less. In particular, the sintering temperature of the ultra-low temperature range of the (Na,K) ₂ MoO ₄ ceramic composition of the present invention is not only lower than the Al material electrode having the lowest melting point (660 ° C) among the general metal materials, but also 10 ° C or more lower, Co-fired with an Al material electrode is possible without any chemical reaction with Al, so it can be put into practical use as a substrate for high-frequency devices with compatibility.

On the other hand, in the (Na,K) ₂ MoO ₄ ceramics composition of the present invention, the substitution amount of K may be in the range of 0.2 mol or less at most, preferably in the range of 0.01 to 0.2 mol, and according to a preferred embodiment of the present invention (Na ,K) ₂ MoO ₄ ceramics composition can be represented by the following formula 1:

(Na _1-x K _x ) ₂ MoO ₄ (Equation 1)

(At this time, the x is in the range of up to 0.2 mol or less, preferably in the range of 0.01 to 0.2 mol)

In addition, the (Na,K) ₂ MoO ₄ ceramics composition according to a preferred embodiment of the present invention has a dielectric constant (ε _r ) ≤ 5, a dielectric loss (tan δ) ≤ 0.008, and a temperature coefficient of resonance frequency (τ _f ) ≤ It provides excellent microwave dielectric properties in the range of ±10 ppm/°C and excellent thermal conductivity in the range of approximately 1.2 to 1.8 W/m·K, which are very promising characteristics for applications as high-frequency devices.

Hereinafter, the present invention will be described in more detail through preferred embodiments of the present invention. These examples are only intended to further illustrate the present invention and should not be construed as limiting the present invention.

Example

The present invention ( Na,K ) ₂ MoO ₄ Manufacturing of ceramic composition sintered body

×t=10×1[mm³] 디스크 펠렛, 17.5×17.5×0.6[mm³] 각형 플레이트, 및

×t=12.7×1.2[mm³] 디스크 펠렛을 각각 형성한 후 500~625℃의 다양한 온도구간에서 2시간 소결하였다.First, using Na ₂ CO ₃ , K ₂ CO ₃ , and MoO ₃ powder as starting materials, weigh these raw material powders according to the stoichiometric ratio of Equation 1, and mix with ethanol as a solvent in a zirconia (YTSZ) ball mill for 12 hours did The mixed raw material powder slip is dried at 85 ° C, and the dried powder cake is crushed and then heat-treated in an alumina crucible at 450 ~ 550 ° C for 2 hours, and then 500 ° C for 2 hours is selected as the appropriate calcination condition through XRD analysis A predetermined synthetic powder having a bar crystal structure (cubic, Fd-3m) was obtained. And, based on each synthetic powder, after sintering,

× t = 10 × 1 [mm ³ ] disk pellets, 17.5 × 17.5 × 0.6 [mm ³ ] square plate, and

× t = 12.7 × 1.2 [mm ³ ] After forming disk pellets, respectively, they were sintered at various temperature ranges of 500 to 625 ° C for 2 hours.

The present invention ( Na,K ) ₂ MoO ₄ Measurement of Microwave Dielectric Characteristics of Ceramic Composition Sintered Body

In addition, the microwave dielectric characteristics of the sintered disk pellet samples were measured by connecting to a network analyzer (8720ES) using a split-post dielectric resonator (SPDR). In addition, the temperature coefficient (τ _f ) of the resonance frequency was calculated by putting the SPDR loaded with the sample into a temperature and humidity constant temperature chamber and applying the change value of the resonance frequency and the temperature range in the temperature range of 25 to 85 ° C. In addition, the thermal conductivity of the sample was calculated by measuring the thermal diffusivity and specific heat at room temperature using laser flash analysis (LFA) and then multiplying by the density of the sample.

The present invention ( Na,K ) ₂ MoO ₄ Analysis of self-temperature compensation mechanism of ceramic composition

The self-temperature compensation mechanism of the (Na,K) ₂ MoO ₄ ceramic composition of the present invention described above will be described below with reference to FIGS. 1 to 3 .

First, FIG. 1 is a solid solution obtained by ultra-low temperature firing in the temperature range of 525 to 625 ° C. while changing the substitution amount of K from 0 mol to 0.2 mol in the (Na _{1 - x} K _x ) ₂ MoO ₄ composition according to one embodiment of the present invention. X-ray diffraction patterns of the sintered composition are shown. In FIG. 1, (a) is a sintered composition with x = 0 mole, (b) is a sintered composition with x = 0.1 mole, and (c) is each X-ray of the sintered composition with x = 0.2 mole. is the diffraction pattern.

Figure 2 shows the X-ray diffraction pattern data of the sintered body of the composition fired at 575 ° C., respectively, in (a) to (c) of FIG. As a result of processing by Rietveld's refinement in consideration of the pattern, (d) in FIG. 2 is in (a) in FIG. 1, (e) is in (b) in FIG. 1, and (f) is in FIG. Each resultant pattern corresponding to (c) of 1.

3 is a solid solution by changing the substitution amount of K from 0 mol to 0.2 mol in the (Na _{1 - x} K _x ) ₂ MoO ₄ composition according to an embodiment of the present invention and firing it at a very low temperature in the temperature range of 525 to 625 ° C. Showing the results of microstructure analysis by FE-SEM / EDS of the composition sintered body, in FIG. 3 (a1) to (a5) correspond to (a) in FIG. ) corresponds to FIG. 1 (b) and x = 0.1 mole of the composition sintered body, (c3) to (c5) correspond to FIG. , Inside each SEM picture, each particle distribution histogram and average particle size graph are inserted and shown, and the pictures (C1) to (c2) disposed at the bottom of the picture (c5) are EDS for some tissues in the picture (b3). is the result of the analysis.

And, as shown in Figure 2, based on the X-ray diffraction data of Figure 1, considering the Bragg diffraction patterns of the α phase (Fd-3m) and the β phase (Pbca), the result data analyzed and calculated by the Rietveld method are shown in the table below arranged as in 1.

1 and 2 and Table 1, the pure Na ₂ MoO ₄ composition sintered body (ie, K substitution amount x=0.0 in Formula 1) has a cubic crystal structure ( Fd -3m space group) as a major phase Two phases coexist: an α phase (α-Na ₂ MoO ₄ ) and a β phase (β-Na ₂ MoO ₄ ) phase of an orthorhombic crystal structure ( Pbca space group) as a minor phase. Observed.

In the Na ₂ MoO ₄ composition in which the α phase (α-Na ₂ MoO ₄ ) and the β phase (β-Na ₂ MoO ₄ ) coexist, the substitution amount of K ⁺ ions for Na ⁺ and the firing temperature are controlled to The microwave dielectric properties of the entire composition are controlled by adjusting the relative fractions of the two phases.

In particular, as shown in Table 1, in the sintered body of the present invention (Na _{1 - x} K _x ) ₂ MoO ₄ composition, as its sintering temperature increases and/or the substitution amount of K ⁺ ions for Na ⁺ increases, the above α phase It can be seen that the phase transition to the β phase increases. In particular, as the substitution amount of K ⁺ ions increases in the composition of the present invention, it is observed that the fraction of cubic phase, which is α phase, relatively decreases, and the fraction of orthorhombic phase, which is β phase, relatively increases.

In the present invention, different crystal growth and arrangement changes and reduction in relative density according to the control of the relative fraction between the α phase and β phase, the degree of void between grains according to the coexistence of different orientation grains, porosity, Depending on the presence or absence of the secondary phase, the degree of thermal diffusion and thermal conductivity can be changed at the heat transfer interface between the internal grains. Regarding the secondary phase, the sintered body obtained by firing the K ⁺ substitution amount x = 0.1 composition shown in FIG. 3 (b5) at 625 ° C, and the K ⁺ substitution amount x = 0.2 composition shown in FIG. In the sintered bodies calcined at ~625 ° C, it was observed that a considerable amount of liquefaction of each crystal grain occurred and proceeded.

In the (Na,K) ₂ MoO ₄ composition of the present invention, the resonance frequency temperature coefficient (τ _f ) is determined by controlling the relative fraction between the α phase and β phase in the sintered body by controlling the firing temperature and/or the amount of K ⁺ substitution as described above. A self-temperature compensation mechanism is implemented and effectively controlled.

In the present invention, due to the operation of this self-temperature compensation mechanism, the large (-) temperature coefficient of the pure Na ₂ MoO ₄ composition, which was close to approximately -76ppm/℃, is close to zero and becomes small, resulting in a small resonance frequency. It is observed that the change is stable. This mechanism is a phenomenon that could not be observed at all in conventional LTCC or uLTCC single compositions.

In addition, in the (Na,K) ₂ MoO ₄ composition according to the present invention, the ionic radius (1.02Å) of the K ⁺ ion substituting Na ⁺ is larger than the ionic radius (1.38Å) of the Na ⁺ ion, and thus ion polarization rate increases, resulting in an increase in permittivity. However, since the internal porosity changes as the amount of substitution of K ⁺ ions increases and the permittivity decreases rather in the voids containing air (permittivity of 1) in the sintered body of the composition, the dielectric constant (ε) according to the substitution of K ⁺ ions throughout the sintered body of the composition It is observed that the change in _r ) is not very large.

Therefore, the (Na,K) ₂ MoO ₄ composition of the present invention maintains the good permittivity and dielectric loss value of NaMoO ₄ ceramics at similar levels, while the poor resonant frequency temperature coefficient (τ _f ) is It is improved to an excellent value by the self-temperature compensation mechanism according to the phase transition control.

The present invention ( Na,K ) ₂ MoO ₄ Analysis of Microwave Dielectric Characteristics of Ceramic Compositions

Microwave dielectric properties of various sintered bodies of ceramic compositions prepared and measured according to the examples of the present invention are shown in Table 2 and FIGS. 4 to 6, and their measured room temperature thermal conductivity values are shown in Table 3 and FIG. 7 below.

4 to 7 show changes in microwave dielectric properties and thermal conductivity according to changes in K substitution amount (mol) and sintering temperature [T (℃)] of (Na,K) ₂ MoO ₄ compositions according to embodiments of the present invention. As graphs, FIG. 4 shows the change in dielectric constant (ε _r ), FIG. 5 shows the change in dielectric loss (tanδ), FIG. 6 shows the change in the resonance frequency temperature coefficient (τ _f ), and FIG. 7 shows the change in thermal conductivity (κ). ), and x in each graph represents the K substitution amount x (mol) in (Na _{1 - x} K _x ) ₂ MoO ₄ in Equation 1 above.

division Furtherance sintering conditions
(℃-2h) measurement
frequency
f _o (GHz) permittivity
(ε _r ) dielectric loss
(tanδ) quality factor
(Q×f)
GHz resonant frequency
temperature coefficient
(τ _f )
ppm/℃ Comparative Example 1 Na ₂ MoO ₄ 575 15 4.16 0.00045 33,330 -28.52 Comparative Example 2 Na ₂ MoO ₄ 600 15 4.01 0.00047 31,910 -17.12 Comparative Example 3 Na ₂ MoO ₄ 625 15 3.96 0.00038 39,270 -22.88 Example 1 ₍ Na _0.995 K _0.005 ) _{2 MoO 4} 575 15 4.72 0.00061 39,765 -21.60 Example 2 ₍ Na _0.995 K _0.005 ) _{2 MoO 4} 600 15 4.38 0.00092 46,365 -65.10 Example 3 ₍ Na _0.995 K _0.005 ) _{2 MoO 4} 625 15 4.22 0.00028 46,350 -43.40 Example 4 (Na _0.99 K _{0. 01} ) _{2 MoO 4} 575 15 3.98 0.00120 45,210 -14.90 Example 5 (Na _0.99 K _{0. 01} ) _{2 MoO 4} 600 15 4.29 0.00062 50,880 -8.19 Example 6 (Na _0.99 K _{0. 01} ) _{2 MoO 4} 625 15 4.16 0.00014 42,885 -7.08 Example 7 (Na _0.9 K _{0. 1} ) _{2 MoO 4} 575 15 3.77 0.00698 2,149 -6.45 Example 8 (Na _0.9 K _{0. 1} ) _{2 MoO 4} 600 15 3.93 0.00426 3,521 -9.36 Example 9 (Na _0.9 K _{0. 1} ) _{2 MoO 4} 625 15 4.25 0.00821 1,827 -27.53 Example 10 (Na _0.8 K _{0. 2} ) _{2 MoO 4} 575 15 4.67 0.00291 5,154 -3.08 Example 11 (Na _0.8 K _{0. 2} ) _{2 MoO 4} 600 15 4.39 0.00556 2,698 -30.37 Example 12 (Na _0.8 K _{0. 2} ) _{2 MoO 4} 625 15 3.95 0.00291 3,521 -9.67 Example 13 (Na _0.7 K _{0. 3} ) _{2 MoO 4} 550 15 3.95 0.00098 15,306 -91.00 Example 14 (Na _0.7 K _{0. 3} ) _{2 MoO 4} 575 15 3.76 0.00551 2,722 -15.05

division Furtherance sintering conditions
(℃-2h) density
(g/cc) thermal diffusivity
(mm ² /s) specific heat
(J/K) room temperature thermal conductivity
(W/m K) note
(increase rate) Comparative Example 4 Na ₂ MoO ₄ 575 2.634 0.514 0.734 0.99 100%
(ref.) Comparative Example 5 Na ₂ MoO ₄ 600 2.585 0.524 0.756 1.02 102% Comparative Example 6 Na ₂ MoO ₄ 625 2.450 0.635 0.751 1.16 116% Example 15 (Na _0.9 K _{0. 1} ) _{2 MoO 4} 575 2.153 0.948 0.864 1.76 176% Example 16 (Na _0.9 K _{0. 1} ) _{2 MoO 4} 600 2.544 0.704 0.862 1.48 148% Example 17 (Na _0.9 K _{0. 1} ) _{2 MoO 4} 625 3.008 0.717 0.571 1.23 123% Example 18 (Na _0.8 K _{0. 2} ) _{2 MoO 4} 575 2.328 0.340 0.829 0.66 66% Example 19 (Na _0.8 K _{0. 2} ) _{2 MoO 4} 600 2.557 0.362 0.764 0.71 71% Example 20 (Na _0.8 K _{0. 2} ) _{2 MoO 4} 625 2.418 0.412 0.762 0.76 76%

First, referring to Table 2 and FIGS _. 4 to 6, the K substitution amount of 0.1 mol (Na _0.9 K _0.1 ) ₂ MoO ₄ composition sample according to Examples 7 to ₉ of the present invention shows a permittivity of 3.77 to 4.25 , especially in the range of sintering temperature of 575 ~ 600 ℃, the permittivity obtained was 3.77 ~ 3.93, pure Na ₂ MoO ₄ It is observed that significantly lower permittivity values are obtained than the compositions (Comparative Examples 1-3). In particular, the (Na _0.9 K _0.1 ) ₂ MoO ₄ composition sample sintered in the range of ₅₇₅ to 600 ° C according to Examples 7 to ₈ of the present invention has an excellent resonance frequency temperature coefficient in the range of -6.45 to -9.36 ppm / ° C is obtained, which is a value that sufficiently satisfies ±10ppm/° C., which is the range of the temperature coefficient of the resonance frequency of the microwave dielectric element required in a filter or resonator for a commercial antenna.

And, according to Examples 10 to 12 of the present invention, the K substitution amount is 0.2 mol (Na _{0.8 K 0. 2} ) ₂ MoO ₄ In the composition sample, the permittivity tends to increase somewhat from 3.95 to 4.67, and the dielectric loss is much higher than that of the pure Na ₂ MoO ₄ composition (Comparative Examples 1 to 3), while the temperature coefficient of the resonant frequency is still -3.1 to -9.67 ppm/℃. It is observed that it exhibits stable characteristics of the range.

On the other hand, as previously reviewed in Table 1, as the amount of K substitution and/or the sintering temperature increase, the internally coexisting α phase (α-Na ₂ MoO ₄ ) of the cubic crystal structure to the β phase of the orthorhombic crystal structure A phase transition to (β-Na ₂ MoO ₄ ) proceeds.

And in this regard, referring to Table 3 and FIG. 7, it is observed that the density value and the thermal diffusivity change as the phase transition from the α phase to the β phase develops as the amount of K substitution increases, and accordingly, in particular, Example 15 of the present invention In the sintered body of the composition of the present invention according to ~ 17, the increase in thermal conductivity by K substitution of Na ranges from a minimum of 123% to a maximum of 176% compared to the sintered body of the pure Na ₂ MoO ₄ composition (Comparative Example 4). However, in the case of the composition sintered body having a K substitution amount of 0.2 mol according to Examples 18 to 20 of the present invention, the thermal conductivity decreases, which is analyzed to be due to the decrease in thermal diffusivity associated with the decrease in relative density.

The present invention (Na _{1 - x} K _x ) ₂ MoO ₄ (x = 0.01 ~ 0.2 mol) composition prepared according to the above embodiments of the present invention has excellent sinterability in the firing range of about 575 ~ 625 ° C. , dielectric constant (ε _r ) in the range of approximately 3.77 to 4.67, dielectric loss (tanδ) in the range of approximately 0.00291 to 0.00821 (@15GHz), resonant frequency temperature coefficient (τ _f ) approximately -3.08 to -30.37ppm/℃, and room temperature It shows excellent microwave dielectric properties with thermal conductivity (κ) ranging from about 1.23 to 1.76 W/mK.

In addition, the (Na,K) ₂ MoO ₄ ceramic composition of the present invention can be advantageously applied as a high-frequency device by co-firing at a very low temperature of about 650 ° C. or less together with a metal electrode printed thereon and manufactured by a conventional thick film process. .

That is, in one embodiment of the present invention, the (Na,K) ₂ MoO ₄ ceramic composition of the present invention is prepared as a slurry according to a general thick film process such as a known doctor blade, and then a green tape is prepared from the slurry and a single green tape in which electrodes of metal materials such as Au, Ag, Cu, Al, etc. are printed on the surface, or a plurality of green tapes are prepared from the slurry, and the electrodes of the metal material are printed on the surface of one or more of the green tapes A ceramic substrate for a high-frequency device can be advantageously manufactured by co-firing the green tape laminate in which the plurality of green tapes are stacked together with the metal electrode at a temperature of about 650° C. or lower.

In such a high-frequency device, the (Na,K) ₂ MoO ₄ ceramic composition of the present invention has a low permittivity (ε _r ) and dielectric loss (tan δ) in the microwave frequency band, particularly stable resonance frequency temperature coefficient (τ _f ) and It provides greatly improved room temperature thermal conductivity (κ).

In addition, the ultra-low temperature sintering temperature of the (Na, K) ₂ MoO ₄ ceramic composition of the present invention is 10 ° C or more lower than that of the Al material electrode having the lowest melting point (660 ° C) among commonly used metal materials. temperature, and co-fired with an Al material electrode without any chemical reaction with Al, so that it can be put into practical use as a substrate for high-frequency devices with compatibility.

In the embodiments and examples of the present invention described above, the powder characteristics such as average particle size, distribution, and specific surface area of the powder composition, and the purity of the raw material, the amount of impurities added, and the sintering conditions vary somewhat within the usual error range. It is quite natural for those skilled in the art that this may exist.

In addition, preferred embodiments and embodiments of the present invention are disclosed for illustrative purposes, and anyone skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, and such modifications , changes, additions, etc. shall be regarded as belonging to the scope of the claims.

Claims (10)

In the dielectric ceramic composition for high-frequency elements,
A dielectric ceramic composition for a high-frequency device having a composition represented by the composition formula (Na _{1 - x} K _x ) ₂ MoO _{4 ,} wherein x in the composition formula is greater than 0 and is in the range of 0.2 mole or less. According to claim 1,
The dielectric ceramic composition for a high-frequency device in which the x in the composition formula is in the range of 0.01 to 0.2 mole. According to claim 1 or 2,
A dielectric ceramic composition for a high-frequency device that is sintered at 650 ° C or less to form a solid solution. In the method for controlling the microwave dielectric properties of the dielectric ceramic composition for a high-frequency device according to claim 1 or 2,
The microwave dielectric characteristic is at least one of a resonant frequency temperature coefficient (τ _f ) value and a thermal conductivity (κ) value, and the dielectric ceramic composition has an α phase of a cubic crystal structure and a β phase of a tetragonal crystal structure coexisting therein,
By changing the value of x in the composition formula within the above range, the relative fraction of the α phase and β phase inside the dielectric ceramic composition is controlled, and the degree of phase transition from the α phase to the β phase is controlled to obtain the microwave dielectric A method for controlling microwave dielectric characteristics of a dielectric ceramic composition for high-frequency devices that controls characteristics. In the method for controlling the microwave dielectric properties of the dielectric ceramic composition for a high-frequency device according to claim 1 or 2,
The microwave dielectric characteristic is at least one of a resonant frequency temperature coefficient (τ _f ) value and a thermal conductivity (κ) value, and the dielectric ceramic composition has an α phase of a cubic crystal structure and a β phase of a tetragonal crystal structure coexisting therein,
By changing the sintering temperature of the dielectric ceramic composition to control the relative fraction of the α phase and β phase inside the dielectric ceramic composition and to control the degree of phase transition from the α phase to the β phase to control the microwave dielectric characteristics A method for controlling microwave dielectric characteristics of a dielectric ceramic composition for high frequency devices. According to claim 5,
The sintering temperature of the dielectric ceramic composition is controlled within the temperature range of 525 ~ 625 ° C. Method for controlling the microwave dielectric properties of the dielectric ceramic composition for high frequency elements. A ceramic substrate for a high frequency element comprising the dielectric ceramic composition for a high frequency element according to claim 1 or 2 and a metal electrode disposed on a surface of the dielectric ceramic composition. In the manufacturing method of a ceramic substrate for a high frequency element,
forming a single or a plurality of green tapes from the slurry of the dielectric ceramic composition according to claim 1 or 2;
disposing a metal electrode on a surface of the single green tape, or disposing a metal electrode on the surface of at least one of the plurality of green tapes, and then laminating the plurality of green tapes to form a green tape laminate;
and co-firing the single green tape or the green tape laminate together with the metal electrode in a temperature range of 650° C. or less. According to claim 8,
The material of the metal electrode is at least one of Au, Ag, Cu, and Al. Method of manufacturing a ceramic substrate for a high-frequency device. According to claim 8,
The method of manufacturing a ceramic substrate for a high-frequency device in which the temperature range of co-firing is adjusted to a temperature range of 575 to 600 ° C.

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