KR100261549B1 - Dielectric ceramic composition for microwave - Google Patents

Abstract

PURPOSE: To prepare a microwave dielectric composition having superior dielectric constant, quality coefficient, and low thermal coefficient of resonate frequency for low temperature sintering of below 960deg.C, additionally 0.105-0.125wt.% of CuO is added in the dielectric composition represented as Bi1-xMxNbO4, thereby it is applicable for use as laminate capacitor adopted to both PCS phone of 1.9GHZ frequency band and CDMA digital cellular phone of 900NHz frequency band. CONSTITUTION: The microwave dielectric composition is prepared by (i) blending Bi2O3 and M2O3 in a mole ration of 0.015: 0.985-0.15:0.85, wherein M is selected from the group consisting of Nd¬+3, La¬3+, Sm¬3+, and Pr¬3+; (ii) adding 0.105 to 0.125wt.% of CuO acting as sintering aid. In the composition, x is 0.1 in the case that M is La¬3+ or Sm¬3+, the range of x is 0.015≤x≤0.15 in the case that M is Nd¬3+, and x is 0.025 in the case that M is Pr¬3+.

Description

Microwave low temperature sintered dielectric composition and preparation method thereof

According to the present invention, a high frequency of stability of the temperature coefficient of the resonant frequency has a high dielectric constant and Q × f _o value by substituting one element of a member of the dielectric material having a relatively high temperature coefficient of resonant frequency with another element having the same valence. A dielectric composition and a method of making the same.

As the use of mobile communication devices used in high frequency bands, such as portable mobile phones, is rapidly becoming more common, the demand for miniaturization, light weight, and high performance of microwave dielectric elements used therein is increasing. The manufacturing process technology attracting attention as a solution to this problem is a multilayer technology of devices that are common in the fabrication of multilayer capacitors and multi-circuit boards. To apply this technology, the dielectric material constituting the device constitutes an internal circuit. It must be possible to sinter at temperatures below the melting point of the metal. Especially in the microwave band of several hundred MH _Z or more, the loss due to the resistance of the internal conductor metal of the multilayer device greatly affects the performance of the device. Therefore, a metal having high electrical conductivity such as silver (Ag) or copper (Cu) It is advantageous to use. However, microwave dielectric materials used in the manufacture of resonators, filters, and duplexers in portable telephones usually have a sintering temperature range of 1,200 ° C to 1500 ° C, much higher than the melting point of silver (melting point 961 ° C) or copper (melting point 1,064 ° C). Therefore, it is impossible to use them as they are.

Therefore, research is being actively conducted to add co-sintering with silver or copper by adding a sintering aid to increase the sinterability at low temperature to existing microwave dielectric materials or developing low-temperature sintered microwave dielectric materials with low sintering temperature. It's going on.

The most important properties required for microwave dielectric materials are

1) Since the size of the dielectric decreases in inverse proportion to the half power of the dielectric constant, the dielectric constant (ε _r ) must be large to reduce the size of the device.

2) The Q value (= 1 / tan δ) should be high to improve the selectivity of the resonance frequency.

3) The temporal change of the temperature coefficient (τ _f ) of the resonance frequency should be good in order to obtain stable resonance characteristics according to the temperature change.

Therefore, the microwave dielectric material must satisfy the above requirements, and therefore, even if the sintering temperature is lowered, the dielectric properties should not be reduced.

Among various microwave dielectric materials, Bi ₂ O ₃ -Nb ₂ O ₅ -based dielectrics have a low sintering temperature (1,100 ° C). Therefore, the sintering aid is added to reduce the sintering temperature to 1,000 ° C or below. It can be applied as a material. In order to stabilize the temperature characteristics of the resonant frequency of the mobile communication device and to facilitate temperature compensation of the resonant circuit, it is important to stabilize the temporal change of the temperature coefficient of the resonant frequency.

Accordingly, the present invention is to provide a dielectric composition for microwaves, which does not degrade the intrinsic dielectric properties of the dielectric or rather exhibits good dielectric properties, but has a small change over time in the temperature coefficient of the resonance frequency and a sintering temperature of 961 ° C. or less, which is a melting point of silver.

1 is a graph showing the temperature coefficient change of Bi _1-X Nd _x NbO ₄ microwave dielectric according to the molar ratio change of Nd ₂ O ₃ .

In the composition of Bi ₂ O ₃ and Nb ₂ O ₅ in a molar ratio of 1: 1, the factor for determining the dielectric properties is Nb ₂ O _5, so in the present invention, the amount of Nb ₂ O ₅ is fixed so as not to lower the dielectric property value. Instead, it replaces Bi ₂ O ₃ with another element having the same valence so as not to reduce the inherent dielectric properties of the Bi ₂ O ₃ dielectric or to show good dielectric properties but to change the temporal coefficient of resonant frequency over time. The technical characteristics thereof are to obtain a microwave dielectric composition having a sintering temperature of 961 ° C. or less, which is a melting point of silver.

The dielectric composition for microwaves of the present invention is 0 <x≤0.15 in a composition system represented by Bi _1-X M _x NbO ₄ , and M ⁺³ is a group consisting of Nd ⁺³ , La ⁺³ , Sm ⁺³ , and Pr ⁺³ Is selected.

In the dielectric composition for microwaves of the present invention, Bi ^{+ 3} of BiNbO ₄ dielectric having a temperature coefficient value of a negative resonance frequency of 0.105 wt% -0.125 wt% of CuO as a sintering aid is substituted by a constant ratio M ^{+ 3} Is done.

In the present invention, the elements for substituting Bi ₂ O ₃ include Nd ₂ O _3, La ₂ O ₃ , Sm ₂ O ₃ , Pr ₂ O _3, and the like. Nd ₂ O ₃ is most preferable, and the amount of substitution of Nd ₂ O ₃ is It is 0.025 mole which shows the best dielectric characteristic and temperature coefficient value of resonant frequency and it is manufactured by microwave device through general ceramic manufacturing process.

_f)의 변화를 나타낸 것으로 Nd₂O₃의 치환량이 증가할수록 그 값이 (+) 방향으로 점차 커지는 것을 볼 수 있다. 전술한 바와 같이 Nd₂O₃를 치환하지 않은 순수한 BiNbO₄는 공진주파수의 온도계수가 약 -21ppm/℃이나 Bi₂O₃를 Nd₂O₃로 일정량 치환하면 그값을 (+) 방향으로 증가시켜 0에 근접하는 양호한 공진주파수의 온도계수값을 나타내게 된다.1 is a temperature coefficient value of the resonance frequency of a Bi _1-X Nd _x NbO ₄ (hereinafter referred to as BNN) microwave dielectric according to a change in the molar ratio of Nd ₂ O ₃ (

_f ) shows a change in the value of Nd ₂ O _{3 It} can be seen that the value gradually increases in the (+) direction. As described above, pure BiNbO _{4 which} does not substitute Nd ₂ O ₃ has a temperature coefficient of resonant frequency of about -21 ppm / ° C., but when Bi ₂ O ₃ is replaced with Nd ₂ O ₃ by a certain amount, the value is increased in the (+) direction to 0. The temperature coefficient value of the good resonant frequency close to is shown.

The manufacturing process and general high frequency dielectric properties of the microwave dielectric composition of the present invention will be more clearly understood through the following examples, but the present invention is not limited thereto.

Example 1

These raw powders were prepared by using Bi ₂ O ₃ , Nb ₂ O ₅ , La ₂ O ₃ , Nd ₂ O _3, Sm ₂ O ₃ , Pr ₂ O _3, CuO with a purity of 99.9% or more as a basic raw material. Accurately weighed to the same composition and then wet hopped for 16 hours with ethanol as a solvent.

The mixed powder was sufficiently dried in a drier for at least 12 hours, and then calcined by maintaining at a temperature of 800 ° C. for 2 hours, followed by wet grinding for 16 hours by adding 0.105 wt% of CuO as a sintering aid to obtain a dry powder.

5% PVA aqueous solution was mixed with a dry powder and sieved, and then sieved.

At this time, the sintering conditions were 2 hours in the air at the sintering temperature of 920 degreeC, 940 degreeC, and 960 degreeC which are below the melting-melting temperature of silver.

The dielectric constant and Qxf _o values for the sintered specimens were measured in the microwave band, and the dielectric constant and Qxf _o value were measured in the resonator of TE ₁₁ mode in a resonator composed of circumferential specimens between two parallel conductor plates connected to a network analyzer (Hewlett packard HP8510B). The dielectric constant and Q × f _o value of the obtained dielectric material were measured using the Hakki-Coleman method. [Reference: BW Hakki, PD Coleman, "A Dielectric Resonator Method of measuring Inductive Capacitance in the Millimeter Range.", IRE. Trans., Microwave Theory Tech., 8, p402, (1960)] The temperature coefficient of the resonant frequency is determined by placing the specimen in a cavity resonator made of aluminum at the resonant frequencies f ₂₅ and 65 ° C at room temperature (25 ° C). The resonance frequency f ₆₅ was measured and calculated.

Table 1 shows the results of measuring the temperature constants of the dielectric constant, Q × f _o value and resonance frequency for these specimens.

Example 2

In the basic manufacturing process of Example 1 Bi ₂ O ₃ was changed from 0.015 mol to 0.15 mol with only Nd ₂ O ₃ by adding 0.125wt% CuO as a sintering aid to prepare a microwave dielectric.

At this time, sintering conditions were made into the air for 2 hours at the sintering temperature of 875 degreeC-960 degreeC.

If you look at the BNN dielectric constant changes in microwave dielectric material according to the molar ratio thriving of _{Nd 2 O 3, Nd 2 O} 3 in the degree of substitution is eseo 0.015 mole up to 0.025 mol is a change in the dielectric constant hardly substitution amount is increased more than the dielectric constant It can be seen that this decreases. However, with increasing temperature for the sintering temperature change of the quality coefficient (Q × f _o) in the BNN microwave dielectric according to the densification of the microstructure, like the change in the dielectric constant replacement amount of Nd ₂ O ₃ yi eseo 0.015 mole 0.025 mole Until now, it can be seen that there is no significant difference in the value of the quality factor, but the value is greatly changed if it is substituted more.

However, according to the change of sintering temperature, there is no big change in the value from 920 ℃ to 940 ℃, but rapidly increases when the sintering temperature reaches 950 ℃, which is the maximum value (Q × f _o ) when the substitution amount of Nd ₂ O ₃ is 0.05 mol. It has a value of about 27725 GHz and its value rapidly decreases as the sintering temperature increases, which is due to the transition of the crystal structure due to the substitution of Nd ₂ O ₃ .

The dielectric constant for these samples are shown measurement results of temperature coefficient Q × f _o value, and the resonance frequency in Table 2.

As can be seen from the table, the microwave dielectric of the present invention was sintered under conditions of up to 920 ° C./2hr by substituting 0.025 mol Nd ₂ O ₃ in the composition of Bi _1-x Nd _x NbO ₄ , and then adding CuO as a sintering aid. The composition can be sintered at ε _r = 40, Q x f _o = 22730 GHz (at 5 GHz), τ _f = 1.8 ppm / ° C or less.

The dielectric composition of the present invention is capable of sintering at a temperature of 960 ° C. or less, and has excellent dielectric constant and Q × f _o characteristics, good temperature coefficient of resonant frequency, and especially dielectric material for stacked bandpass filter of 900 MHz and 1.9 GHz band portable telephones. It can be usefully used as.

Claims (6)

A dielectric composition for microwaves, wherein 0 <x≤0.15 in a composition system represented by Bi _1-x M _x NbO ₄ , and M ⁺³ is selected from the group consisting of Nd ⁺³ , La ⁺³ , Sm ⁺³ , and Pr ⁺³ . The dielectric composition of claim 1, wherein M is La ³⁺ and x is 0.1. The dielectric composition of claim 1, wherein M is Sm ³⁺ and x is 0.1. The dielectric composition for microwaves according to claim 1, wherein M is Nd ³⁺ and 0.015 ≦ x ≦ 0.15. The dielectric composition of claim 1, wherein M is Pr ³⁺ and x is 0.025. Bi ₂ O ₃ and M ₂ O ₃ is 0.015 to 0.15 mole was mixed with molar ratio of 0.985 to 0.85 mol selected from the group consisting of ^{Bi +3 Nd +3, La +3,} Sm +3, Pr +3 M + ^The method for producing a dielectric composition for microwaves according to the composition system of claim 1, wherein the composition is substituted with ³ at the above mixing ratio and 0.10 wt% -0.125 wt% of CuO is added as a sintering aid.

Images