JP2006045005A - Dielectric ceramic composition and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition which exhibits a stable dielectric constant when it is simultaneously fired together with an electrode containing silver in the form of Ag, Ag-Pd, Ag-Pt or the like, in the dielectric ceramic composition having a high relative density and containing titanium oxide as a main component; and to provide a method for manufacturing the same. <P>SOLUTION: In the dielectric ceramic composition containing titanium oxide as a main component and having a relative density of ≥99%, Cu is contained in an amount of 0.2-0.9 wt.%, expressed in terms of CuO, based on the amount of titanium oxide being the main component, and further at least one kind selected from Zn, Al and Co is contained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dielectric ceramic composition used for various electronic devices and a method for producing the same.

  Hereinafter, a conventional dielectric ceramic composition will be described taking a multilayer ceramic electronic component using this material as an example.

  A conventional LC filter, which is a multilayer ceramic electronic component, has a coil pattern layer formed using an electrode containing Ag in a magnetic layer composed of a magnetic ceramic composition, and a dielectric composed of a dielectric ceramic composition. A capacitor electrode pattern layer formed by using an electrode containing Ag in the body layer was laminated to form a structure as shown in FIG.

  FIG. 1 is a perspective view of a conventional LC filter. In FIG. 1, 1 is a dielectric ceramic composition, 2 is a magnetic ceramic composition, 3 is an electrode pattern of a coil, and 4 is an electrode pattern of a capacitor.

  Here, the electrode pattern 3 of the coil and the electrode pattern 4 of the capacitor can be baked in the air atmosphere, and an electrode material containing silver such as Ag, Ag-Pd or Ag-Pt having a high electric conductivity is mainly used. It is used for. The dielectric ceramic composition 1 is made of a titanium oxide-based dielectric ceramic material that is sintered at a low temperature of about 900 ° C. for simultaneous firing of the electrode pattern 3 of the coil and the electrode pattern 4 of the capacitor.

  Further, since the titanium oxide-based dielectric ceramic material used for the dielectric ceramic composition 1 needs to be fired simultaneously with an electrode material having a low melting point such as silver, it is a main component for firing at a low temperature. Several percent of Cu is added to some titanium oxide. Further, other additives may be added to control the dielectric constant and temperature characteristics.

  Similarly, the magnetic ceramic composition 2 can be fired at around 900 ° C., and Ni—Zn—Cu ferrite having magnetism for increasing the inductance value is used.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP-A-5-234421

  However, in the above-mentioned conventional configuration, when a dielectric ceramic composition mainly composed of titanium oxide having a relative density of 99% or more is co-fired with an electrode containing silver such as Ag, Ag-Pd or Ag-Pt. Variation of dielectric constant caused by abnormal grain growth occurring in the dielectric ceramic composition occurs, and the capacitance value of the capacitor element using the dielectric ceramic composition as a dielectric layer varies. It was.

  The present invention solves the above-mentioned conventional problems, and provides a dielectric ceramic composition having a stable dielectric constant even when co-fired with an electrode containing silver such as Ag, Ag-Pd or Ag-Pt, and a method for producing the same. The purpose is to provide.

  In order to solve the above-described conventional problems, the present invention provides a dielectric ceramic composition mainly composed of titanium oxide and having a relative density of 99% or more in terms of CuO with respect to titanium oxide as a main component. The composition contains 0.2 to 0.9 wt% of Cu and at least one of Zn, Al, and Co.

  The dielectric porcelain composition of the present invention and the method for producing the same are described as follows. Since growth can be suppressed, a dielectric ceramic composition having a stable dielectric constant even when co-fired with an electrode containing silver and a method for producing the same can be provided.

(Embodiment 1)
Hereinafter, the dielectric ceramic composition and the manufacturing method thereof according to Embodiment 1 of the present invention will be described.

In the dielectric ceramic composition and the manufacturing method thereof in the first embodiment, as a first step, a titanium oxide powder having an average particle diameter of 0.7 μm or less as a main component and an average particle diameter of less than 0.1 μm Table 1 shows the copper oxide powder and any of zinc oxide powder, cobalt oxide powder or aluminum oxide having an average particle diameter of less than 0.1 μm in terms of TiO ₂ , CuO, ZnO, CoO and Al ₂ O ₃ . It mix | blended so that it might become a composition, it mixed and disperse | distributed using the medium stirring mill using the YTZ bead of 0.2mm (PHI) which is a dispersion medium after adding a suitable amount of organic solvents, and produced the ceramic slurry.

  Next, as a second step, an organic binder composed of a resin material such as polyvinyl butyral and a plasticizer such as DBP is added to form a slurry, and a doctor blade method, a reverse roll method or a die coater method using the obtained ceramic slurry. A ceramic green sheet was prepared by applying a predetermined thickness on a base film such as a PET film and drying with a dryer.

  Next, in order to evaluate the electrical characteristics of the dielectric ceramic composition, a multilayer structure of ceramic green sheets having a multilayer structure in which an electrode pattern for forming a capacitor element is printed on the inner layer is prepared.

  Therefore, after printing and forming in a predetermined electrode pattern shape using Ag paste on the ceramic green sheet obtained in the second step, the plurality of ceramic green sheets are laminated and thermocompression bonded. Produced.

  The laminate thus produced was fired as a third step in the air atmosphere at 900 ° C. under a firing condition of 2 hours. A dielectric ceramic with a built-in capacitor element having a built-in counter electrode was produced by using two electrode patterns in the inner layer of the laminate.

  The evaluation results of the dielectric properties of the dielectric ceramic produced by the manufacturing method as described above are shown in comparison with (Table 1).

Here, the relative density of the dielectric ceramic composition is calculated from the weight and dimensions of the fired body in which no Ag electrode is incorporated, and the relative density (%) based on the density of titanium oxide (4.2 g / cm ³ ). ).

  The average particle size of the fired dielectric ceramic composition and the observation of abnormal grain growth were observed by observing the cross section of the fired dielectric ceramic with an SEM.

  The dielectric constant is calculated from the capacitance of the built-in capacitor element using an impedance material analyzer (E4991A; Agilent) at 500 MHz, and the thickness of the dielectric layer formed on the inner layer and the electrode pattern area facing it. did.

  Moreover, the average particle diameter of the used various raw material powders was measured using a laser type particle size distribution meter (LS13320; BECKMAN COULTER).

  From the results of (Table 1), it can be seen that the dielectric constant is stable in the samples (Examples 1 to 9) having compositions in which abnormal grain growth does not occur. Here, copper oxide is effective in enhancing the sinterability of titanium oxide, which is the main component, and the addition of zinc oxide, cobalt oxide or aluminum oxide is an additive that exhibits the effect of suppressing abnormal grain growth.

  On the other hand, as shown in Comparative Examples 1 to 6, when the addition amount of the copper oxide powder is 0.1 wt% or less, a dielectric ceramic composition having a relative density of 99% or more cannot be obtained and the dielectric constant is stabilized, but the relative density is lowered. This is not desirable because the average value of the dielectric constant decreases due to the above. When the addition amount of copper oxide powder is 1.0 wt% or more, the effect of suppressing abnormal grain growth due to the addition of zinc oxide, cobalt oxide, or aluminum oxide cannot be exhibited, and the variation in dielectric constant becomes large. Therefore, the suitable addition amount of copper oxide powder was 0.20-0.90 wt%.

  For comparison, a sample was prepared through the same manufacturing process as described above using copper oxide powder having the composition of Examples 2, 5 and 8 and an average particle size of 0.3 μm. Abnormal grain growth of 30 μm was observed, and it was confirmed that the variation in dielectric constant was as large as 15 to 25%. This abnormal grain growth occurs frequently in the vicinity of the silver electrode, and it is considered that abnormal grain growth occurs when the sintering reaction proceeds in the presence of silver, copper oxide, and titanium oxide. Therefore, even if the addition amount of copper oxide is optimal as an overall addition amount, the copper oxide content is high in the microscopic region, and in such a microscopic region, zinc oxide is high. In addition, since it is difficult to obtain an effect of suppressing abnormal grain growth by adding cobalt oxide or aluminum oxide, it is desirable that the average particle diameter of the copper oxide powder be sufficiently uniformly dispersed using fine powder of less than 0.1 μm. Furthermore, it has been found that it is effective to use fine powder having an average particle diameter of zinc oxide, cobalt oxide or aluminum oxide of less than 0.1 μm.

  It was found that by adopting such a configuration (Example 1 to Example 9), abnormal grain growth does not occur even when co-firing with an electrode containing silver.

  Further, even when copper oxide powder having an average particle diameter of less than 0.1 μm is used, secondary particles of copper oxide powder of about 0.2 μm are present with a dispersion capacity of about 0.2 μm, and abnormal grain growth is similarly observed. From this, it is assumed that this phenomenon causes abnormal grain growth starting from copper oxide grains having a large grain size. Therefore, it is preferable to prepare a ceramic slurry by mixing and dispersing using a medium stirring mill or the like.

  Also, the average particle diameter of the titanium oxide powder is set to 0.7 μm or less because when it is larger than 0.7 μm, a dielectric ceramic composition having a relative density of 99% or more cannot be obtained at a firing temperature of 900 ° C. This is because. Further, if the addition amount of copper oxide is 1 wt% or more, a dielectric ceramic composition having a relative density of 99% or more can be obtained, but it is not desirable because abnormal grain growth occurs.

  In addition, in the case where an electrode containing silver and a capacitor element are formed using a dielectric porcelain composition having a relative density of less than 99%, the insulation reliability is insufficient. Short circuit failure may occur due to migration. Therefore, a relative density of 99% or more is indispensable as a ceramic dielectric composition for forming a capacitor element using an electrode material containing silver.

  As described above, copper oxide is added to enhance the sinterability of titanium oxide, which is the main component, and in the local location where the addition of this copper oxide and the electrode material containing silver are present in the electrode. By adding at least one of Zn, Al, and Co, which has the effect of suppressing the occurrence of abnormal grain growth due to grain boundary diffusion, local abnormal grain growth can be achieved while enhancing the co-sinterability with the electrode containing silver. A dielectric ceramic composition having a suppressed relative density of 99% or more can be obtained. This makes it possible to incorporate capacitor elements with little variation by using this dielectric ceramic composition in a dielectric layer such as a multilayer ceramic electronic component.

  Further, by setting the crystal particle diameter to 3 μm or less, a dielectric ceramic composition with little variation in dielectric characteristics can be obtained.

In addition, as a method for producing the dielectric ceramic composition, with respect to titanium oxide powder having an average particle diameter of 0.7 μm or less, copper oxide powder having an average particle diameter of less than 0.1 μm is 0.2 to 0.2 in terms of CuO. Add 0.9 wt%, and zinc oxide powder with an average particle size of less than 0.1 μm is 0.20 wt% in terms of ZnO, or cobalt oxide powder is 0.20 wt% in terms of CoO, or aluminum oxide powder is Al ₂ O. _After adding, mixing, and dispersing 0.05wt% in terms of ₃ and then co-firing the green sheet molded body with an electrode containing silver at a firing temperature of 1000 ° C or less, no abnormal grain growth occurs A titanium oxide based dielectric ceramic composition having a relative density of 99% or more can be produced.

  As a result, it is possible to realize a dielectric ceramic composition with little variation in dielectric constant and a method for manufacturing the same. Furthermore, a multilayer ceramic electronic component such as an LC filter, a noise countermeasure component and a high-frequency module component incorporating a high-accuracy capacitor element using an electrode containing silver using such a dielectric ceramic composition is realized. Can do.

  In the present embodiment, the raw material used in the first step has been described using an oxide as an example. However, any raw material that becomes an oxide in the firing step may be used, such as a hydroxide and a carbonate. It is possible to use.

  Moreover, although the ceramic green sheet has been described as an example of the forming method in the second step, it has been confirmed that the same effect can be obtained by a forming method such as dry forming or extrusion forming.

  In addition, although the firing in the air has been described as an example of the firing method in the third step, the same effect can be obtained by firing in the atmosphere if necessary.

(Embodiment 2)
Hereinafter, the dielectric ceramic composition and the manufacturing method thereof according to Embodiment 2 of the present invention will be described.

  As the dielectric ceramic composition in the present embodiment 2, a laminated dielectric ceramic composition was prepared by using the powder having the composition shown in Table 2 through the same process as in the first embodiment.

  The evaluation results of the obtained multilayer dielectric ceramic composition are shown in comparison with (Table 2).

  From the results of (Table 2), it can be seen that the dielectric constant is stable in the samples (Examples 10 and 11) having compositions in which abnormal grain growth does not occur. Further, when the added amount of zinc oxide powder is 0.05 wt% or less (Comparative Example 7), there is no effect of suppressing abnormal grain growth of the dielectric ceramic composition, and the added amount of zinc oxide powder is 0.30 wt% or more (Comparative Example 8). ) Is not desirable because a dielectric ceramic composition having a relative density of 99% or more cannot be obtained, and the average value of the dielectric constant decreases due to the decrease in relative density. Accordingly, the zinc oxide powder is preferably in the range of 0.10 to 0.25 wt%.

  For comparison, a sample was prepared through the same process as described above using the zinc oxide powder having the composition of Examples 10 and 11 and an average particle size of 0.15 μm, and the maximum particle size was 20 to 30 μm. Grain growth was observed and it was confirmed that the variation in dielectric constant was as large as 15 to 25%. Since zinc oxide powder having a large average particle size cannot provide an effect of suppressing abnormal grain growth, the average particle size of zinc oxide powder is preferably less than 0.1 μm. Furthermore, it has been found that the effect of suppressing abnormal grain growth increases as the dispersion proceeds with a medium stirring mill.

(Embodiment 3)
Hereinafter, the dielectric ceramic composition and the manufacturing method thereof according to Embodiment 3 of the present invention will be described.

  As the dielectric ceramic composition in the present third embodiment, a laminated dielectric ceramic composition was prepared by using the powder having the composition shown in Table 3 through the same process as in the first embodiment.

  The evaluation results of the obtained multilayer dielectric ceramic composition are shown in comparison with (Table 3).

  From the results of (Table 3), it can be seen that the dielectric constant is stable in the samples (Example 12 and Example 13) having a composition in which no abnormal grain growth occurs. When the addition amount of cobalt oxide powder is 0.10 wt% or less (Comparative Example 9), there is no effect of suppressing abnormal grain growth of the dielectric ceramic composition, and the addition amount of cobalt oxide powder is 0.25 wt% or more (Comparative Example 10). In this case, a dielectric ceramic composition having a relative density of 99% or more cannot be obtained, and the average value of the dielectric constant decreases due to a decrease in the relative density, which is not desirable. Therefore, the cobalt oxide powder was 0.15 to 0.20 wt%.

  For comparison, when a sample was prepared through the same process using cobalt oxide powder having the composition of Examples 12 and 13 and an average particle size of 0.30 μm, abnormal grain growth with a maximum particle size of 20 to 30 μm was observed. Observed, it was confirmed that the variation in dielectric constant was as large as 15 to 25%.

  From this result, it is desirable that the average particle diameter of the cobalt oxide powder is less than 0.1 μm because the effect of suppressing abnormal grain growth cannot be obtained with the cobalt oxide powder having a large particle diameter. Further, the effect of suppressing abnormal grain growth increases as the dispersion is advanced by the medium stirring mill.

(Embodiment 4)
Hereinafter, a dielectric ceramic composition and a manufacturing method thereof according to Embodiment 4 of the present invention will be described.

  The dielectric ceramic composition according to the fourth embodiment is a laminated dielectric ceramic composition produced by using the powder having the composition shown in Table 4 through the same process as in the first embodiment.

  The evaluation results of the obtained multilayer dielectric ceramic composition are shown in comparison with (Table 4).

  From the results of (Table 4), it can be seen that the dielectric constant is stable in the samples (Examples 14 and 15) having compositions in which abnormal grain growth does not occur. When the added amount of aluminum oxide powder is 0.01 wt% or less (Comparative Example 11), there is no effect of suppressing abnormal grain growth of the dielectric ceramic composition, and the added amount of aluminum oxide powder is 0.15 wt% or more (Comparative Example 12). In this case, a dielectric ceramic composition having a relative density of 99% or more cannot be obtained, and the average value of the dielectric constant decreases due to a decrease in the relative density, which is not desirable. Therefore, the aluminum oxide powder was set to 0.05 to 0.10 wt%.

  For comparison, a sample was prepared through the same process using aluminum oxide powder having the composition of Examples 2, 5 and 8 and an average particle size of 0.30 μm. As a result, abnormal particles having a maximum particle size of 20 to 30 μm were prepared. Growth was observed, and it was confirmed that the variation in dielectric constant was as large as 15 to 25%.

  From these results, since the effect of suppressing abnormal grain growth cannot be obtained with aluminum oxide powder having a large particle size, the average particle size of aluminum oxide powder is preferably less than 0.1 μm. Furthermore, it has been found that the effect of suppressing abnormal grain growth increases as the dispersion proceeds with a medium stirring mill.

  As described above, copper oxide is added to enhance the sinterability of titanium oxide, which is the main component, and in the local location where the addition of this copper oxide and the electrode material containing silver are present in the electrode. By adding at least one of Zn, Al, and Co, which has the effect of suppressing the occurrence of abnormal grain growth due to grain boundary diffusion, local abnormal grains are enhanced while improving the co-sinterability with the electrode containing silver. A dielectric ceramic composition having a relative density of 99% or more with suppressed growth can be obtained.

In addition, as a method for producing the dielectric ceramic composition, with respect to titanium oxide powder having an average particle size of 0.7 μm or less, copper oxide powder having an average particle size of less than 0.1 μm is 0.2 to 0.2 in terms of CuO. 0.9 wt% is added, and zinc oxide powder having an average particle size of less than 0.1 μm is 0.10 to 0.25 wt% in terms of ZnO, or cobalt oxide powder is 0.15 to 0.20 wt% in terms of CoO, or Aluminum oxide powder was added in an amount of 0.05 to 0.10 wt% in terms of Al ₂ O ₃ and blended, mixed and dispersed, and then the molded body was co-fired at a firing temperature of 1000 ° C. or less with a silver-containing electrode. Even in this case, a titanium oxide based dielectric ceramic composition having a relative density of 99% or more can be produced. As a result, it is possible to realize a dielectric ceramic composition that exhibits performance stable in dielectric characteristics such as dielectric constant and temperature characteristics, and a manufacturing method thereof. Furthermore, it is possible to realize a multilayer ceramic electronic component such as a high-homogeneous LC filter, a noise countermeasure component, a high-frequency module, etc. with a built-in capacitor element using an electrode containing silver using such a dielectric ceramic composition. it can.

  The dielectric ceramic composition and method for producing the same according to the present invention includes abnormal grain growth of a titanium oxide-based dielectric ceramic composition that occurs during simultaneous firing with an electrode containing silver such as Ag, Ag-Pd, or Ag-Pt. It is possible to suppress variations in dielectric constant by suppressing the above, and it is useful as a highly accurate multilayer ceramic electronic component used in various electronic devices.

A perspective view of a conventional LC filter

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric ceramic composition 2 Magnetic ceramic composition 3 Coil electrode pattern 4 Capacitor electrode pattern

Claims (6)

In the dielectric ceramic composition composed mainly of titanium oxide and having a relative density of 99% or more, containing 0.2 to 0.9 wt% of Cu in terms of CuO with respect to titanium oxide as the main component, A dielectric ceramic composition containing at least one of Zn, Al, and Co. The dielectric ceramic composition according to claim 1, wherein Zn is contained in an amount of 0.10 to 0.25 wt% in terms of ZnO. The dielectric ceramic composition according to claim 1, wherein the Al containing 0.05～0.10Wt% in terms of Al ₂ O _3. The dielectric ceramic composition according to claim 1, wherein Co is contained in an amount of 0.15 to 0.20 wt% in terms of CoO. The dielectric ceramic composition according to claim 1, wherein the crystal particle diameter is 3 μm or less. The dielectric ceramic composition according to claim 1 is blended after blending titanium oxide, copper oxide, at least one of zinc oxide, aluminum oxide, or cobalt oxide and a solvent so as to have a predetermined blending composition. The first step to disperse, the second step of producing a molded body after adding an organic binder to the blend composition obtained in the first step, and the molded body obtained from the second step at 1000 ° C. or less A method for producing a dielectric ceramic composition produced by a third step of firing at a temperature, wherein the titanium oxide used in the first step has an average particle size of 0.7 μm or less and an average particle size of less than 0.1 μm. A method for producing a dielectric ceramic composition using a certain copper oxide, zinc oxide, aluminum oxide or cobalt oxide.

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