JPH04359806A - Dielectric ceramic composition and dielectric filter using dielectric ceramic composition and its manufacture - Google Patents

Abstract

PURPOSE:To make it possible to sinter a dielectric ceramic composition having a high dielectric constant, low dielectirc loss and temperature coefficient of electrostatic capacity, and usable for a compact layered capacitors, etc., at low temperature and provide a dielectric filter using the composition and a copper as an inner conductor and give a method to manufacture the filter. CONSTITUTION:Using a BaTiO3-Nd2O3-Sm2O3 type and a SiO2-Pb0-CaO-B2O3-Na2 O-MgO-K2O type and limiting ratio of each component, dielectric constant as high as at least 10, high Q, high specific resistionty and low temperature coefficient of electrostatic capacity are achieved even by sintering the composition at temperature as low as highest 1000 deg.C at which copper is not oxidized. Also, using the composition and CuO as a starting raw material for a conductor part, an economical and highly reliable dielectric filter is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition that can be fired at a relatively low temperature, a dielectric filter using the composition and using copper as an internal conductor, and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION In recent years, electronic components such as capacitors are rapidly becoming stacked chip components due to the desire for miniaturization.

[0003] There is a permanent demand for miniaturization of electronic components, and for this purpose, the dielectric constant of the dielectric ceramic used must be as large as possible. Furthermore, for high frequency use, dielectric loss and temperature coefficient of capacitance must also be small.

Furthermore, as the number of layers increases, the cost of expensive metals such as platinum and palladium used in conductors has increased. Recently, attempts have been made to replace these precious metals with relatively inexpensive metals such as silver-palladium alloys, nickel, and copper. (For example, see JP-A-49-19399, JP-A-1-248326, and JP-A-1-227305.) However, dielectric ceramics that can use these metals have a large dielectric constant, but have a large dielectric loss. The temperature coefficients of capacitance and capacitance were mainly relatively large.

[0005] Copper, which has high electrical conductivity and good solderability and ion migration resistance, is effective as a conductor for dielectric ceramics used in high frequency bands; however, in order to co-fire copper as a conductor, must be fired below the melting point of copper and in nitrogen so that the copper is not oxidized. Even when metallic copper is used as a starting material, in the firing process, if there is too much oxygen, the copper will be oxidized, and if there is too little, the organic binder will not be sufficiently decomposed and good conductivity will not be obtained. It is necessary to control the partial pressure.

[0006]

[Problems to be Solved by the Invention] However, with the above-mentioned conventional configuration, there is a problem that it is difficult to control the oxygen partial pressure accurately in the firing process, and that the copper This had the problem of cracks occurring in the element body due to volumetric expansion due to oxidation.

The present invention solves the above-mentioned conventional problems, and can be fired at a low temperature of 1000°C or less, and even under firing conditions with a low oxygen partial pressure that does not oxidize copper, the dielectric constant is 10 or more. The first object of the present invention is to provide a dielectric ceramic composition that has a high Q (reciprocal of dielectric loss value), high specific resistance, and has a very small temperature change rate of capacitance.

A second object of the present invention is to provide an inexpensive and highly reliable high-frequency dielectric filter using a base metal such as copper as a conductor, and a method for manufacturing the same.

[0009]

[Means for Solving the Problems] In order to achieve the first object, the dielectric ceramic composition of the present invention has BaTiO3-Nd
2O3-Sm2O3-TiO2 system, Al2O3 and SiO
2-PbO-CaO-B2O3-Na2O-MgO-K
It has a composition consisting of 2O system, and the amount of each component is limited within a predetermined range.

[0010] In order to achieve the second object, the dielectric filter of the present invention and its manufacturing method include a structure including the above dielectric ceramic composition and a copper inner conductor, and a structure in which the above dielectric ceramic composition is inorganic. A first green sheet containing an organic binder and a plasticizer as components is produced, a paste composition containing CuO as a main component is printed on the green sheet to form a pattern, and a pattern is formed on the green sheet, which is different from the first green sheet. Either a predetermined number of patterned second green sheets are laminated to form a multilayer structure, or a CuO paste is printed on the green sheet, and a dielectric paste having the same composition as the inorganic composition of the green sheet is printed. A green laminate formation process that is repeated a predetermined number of times to form a multilayer body, a heat treatment process that burns out the organic components inside the multilayer body in the air or an oxygen atmosphere, and a process for forming metallic copper in hydrogen or a mixed gas of hydrogen and nitrogen. It has a structure consisting of a reduction step to make it oxidized, and a firing step in nitrogen.

[0011]

[Function] With this configuration, even at a relatively low firing temperature of 1000°C or less, and under firing conditions such as low oxygen partial pressure that the copper is not oxidized, it has a dielectric constant of 10 or more, high Q, high resistivity, and small This results in a dielectric filter using a dielectric ceramic composition having a temperature coefficient of capacitance and copper as an internal conductor.

0012

[Examples] Examples of the present invention will be described below.

(Example 1) Industrial raw material BaTiO3,
Nd2O3, Sm2O3, TiO2, Al2O3, Si
Predetermined amounts of O2, PbO, CaO, B2O3, Na2O, MgO, and K2O were weighed so as to have the composition ratios shown in Table 1.

[0014]

[Table 1]

After thoroughly kneading BaTiO3, Nd2O3, Sm2O3 and TiO2, the mixture was placed in an alumina porcelain crucible, covered with a homogeneous lid, and calcined in a furnace. The calcined powder was placed in a polyethylene container along with pure water and zirconia boulders and wet-pulverized. The crushed sample was taken out from the polyethylene container into a stainless steel container and thoroughly dried in a dryer. Next, SiO2, PbO, CaO, B
After sufficiently kneading 2O3, Na2O, MgO and K2O, they were placed in an alumina porcelain crucible, covered with a homogeneous lid, melted in a furnace, and rapidly cooled to vitrify. The vitrified sample was placed in a polyethylene container together with pure water and zirconia stones, wet-pulverized, and then sufficiently dried in the same manner as described above. Next, the calcined sample, the vitrified sample, and Al2O3 were placed in a polyethylene container together with pure water and zirconia cobblestones and wet-kneaded, and then taken out from the container and thoroughly dried.

[0016] Add polyvinyl alcohol aqueous solution to the sample powder prepared in this way, thoroughly knead it in a mortar, and
It was granulated using a 2-mesh sieve. Put the granulated powder into the mold,
A disk-shaped sample was prepared by pressure molding at a pressure of about 1 ton per square centimeter. This sample was placed on an alumina base plate and fired at a predetermined temperature while the atmosphere in the furnace was controlled to have an oxygen partial pressure that would not oxidize the copper.

In--Ga alloy was applied to both sides of the fired sample, and the capacitance, Q, insulation resistance, and rate of change in capacitance with temperature of the sample were measured. The capacitance and Q were measured at 20° C. with 1 V applied and a frequency of 1 MHz. The insulation resistance was measured by applying a 50V DC voltage for 30 seconds and measuring the value 1 minute later. The temperature change rate of capacitance was measured in the range from -25°C to +85°C, and calculated based on the capacitance at +20°C. (Table 2) shows the results. The criteria for judgment are that the optimum firing temperature is 1000°C or less, the dielectric constant is 10 or more,
The Q was 2000 or more, the specific resistance was 1013 Ω·cm or more, and the capacitance temperature change rate was within 0±30 ppm per 1°C.

[0018]

[Table 2]

[0019] Sample number 1 has a firing temperature of 1000
Since it is higher than ℃ and the specific resistance is also outside the criteria,
This SiO2-PbO-CaO-B2O3-Na2O-
The composition ratio of the MgO-K2O system was set outside the scope of the invention. Samples with sample numbers 2 and 3 have a Q lower than 2000 and a resistivity lower than 1013 Ωcm, so this Al2O3
The composition ratio is outside the scope of the invention. Sample numbers 13 and 1
Sample No. 8 has a dielectric constant lower than 10, so this Al
The composition ratio of 2O3 was set outside the scope of the invention. Sample No. 17 has a temperature change rate of capacitance that is outside the criteria, so this BaTiO3-Nd2O3-Sm2O3-T
The iO2 composition ratio was outside the scope of the invention. Since the other samples sufficiently satisfied the characteristics of the criteria, each composition ratio was determined to be within the range of the present invention.

(Example 2) Industrial raw materials BaTiO3 is 8.0% by weight, Nd2O3 is 14.0% by weight, Sm2O
3 is 5.0% by weight, TiO2 is 13.0% by weight, Al2
O3 is 17.5% by weight, SiO2 is 25.5% by weight, P
bO is 7.65% by weight, CaO is 3.4% by weight, B2O
3 is 2.55% by weight, Na2O is 1.275% by weight, M
1.275 wt% gO and 0.85 wt% K2O
A predetermined amount was weighed so that BaTiO3, Nd
After thoroughly kneading 2O3, Sm2O3 and TiO2, the mixture was placed in an alumina porcelain crucible, covered with a homogeneous lid, and calcined in a furnace. The calcined powder was placed in a polyethylene container along with pure water and zirconia boulders and wet-pulverized. The crushed sample was taken out from the polyethylene container into a stainless steel container and thoroughly dried in a dryer. Next, SiO2, PbO,
After sufficiently kneading CaO, B2O3, Na2O, MgO and K2O, they were placed in an alumina porcelain crucible, covered with a homogeneous lid, melted in a furnace, and rapidly cooled to vitrify. The vitrified sample was placed in a polyethylene container together with pure water and zirconia cobblestones, wet-pulverized, and then sufficiently dried in the same manner as described above. Next, the calcined sample, the vitrified sample, and Al2O3 were placed in a polyethylene container together with pure water and zirconia cobblestones and wet-kneaded, and then taken out from the container and thoroughly dried.

Next, the conductive paste was prepared by adding 5% by weight of glass frit to CuO powder as an inorganic component, and adding ethyl cellulose as an organic binder together with a vehicle dissolved in terpineol, and mixing with a three-stage roll.

Next, the powder thus produced was used as an inorganic component, and polyvinyl butyral and polyvinyl butyral were added as organic binders.
Di-n-butyl phthalate as a plasticizer, as a solvent,
A mixture of toluene and isopropyl alcohol (30:7)
0 weight ratio) were mixed in the composition ratio as shown in Table 3 to form a slurry.

[0023]

[Table 3]

[0024] This slurry was formed into a sheet on an organic film using a doctor blade method. Next, dry, punch out,
Through-hole processing was performed. A conductive pattern was formed on this green sheet by screen printing using the CuO paste described above. A predetermined number of green sheets were stacked and thermocompressed to produce a laminate.

Next, this laminate was raised to a temperature of 600° C. in the atmosphere and held for 2 hours to burn off the organic components. Further, this laminate was heat-treated in pure hydrogen or a mixed gas of hydrogen and nitrogen at a temperature of 175 to 400° C. for 5 hours to reduce the conductor portion. Next, this laminate was fired in nitrogen at a temperature of 925° C. for 1 hour.

[0026] In the laminate thus produced,
The sheet resistance of the internal conductor was 2 mΩ/□, indicating that the CuO was completely metallized. Also, the dielectric constant and Q of this laminate are 14 and 1, respectively, at a measurement frequency of 1 MHz.
0000, and the specific resistance was 1×10 14 Ω·cm. Further, the dielectric filter manufactured by this method had a resonant frequency of 930 MHz, an unloaded Q of 80, and an insertion loss of 3 dB.

[0027]

Effects of the Invention As is clear from the description of the above embodiments, the present invention provides BaTiO3-Nd2O3-Sm2O3
-TiO2 system, Al2O3 and SiO2-PbO-Cao
- A configuration with a composition consisting of B2O3-Na2O-MgO-K2O system and in which the amount of each component is limited within a predetermined range, a configuration with the above-mentioned dielectric ceramic composition and a copper internal conductor, and the above-mentioned dielectric porcelain composition A first green sheet containing an inorganic composition, an organic binder, and a plasticizer is produced, and a paste composition containing CuO as a main component is printed on the green sheet to form a pattern, thereby forming a first green sheet. This can be done by laminating a predetermined number of second green sheets with different patterns, or by printing CuO paste on the green sheet and printing a dielectric paste with the same composition as the inorganic composition of the green sheet. A green laminate formation process in which printing is repeated a predetermined number of times to form a multilayer body, a heat treatment process in which organic components inside the multilayer body are incinerated in the air or oxygen atmosphere, and in hydrogen or a mixed gas of hydrogen and nitrogen. The structure consists of a reduction process to convert copper into metal copper, and a firing process in nitrogen, which allows firing at a low temperature of 1000°C or less, and even under firing conditions at a low oxygen partial pressure that does not oxidize copper, the dielectric constant is 10. As described above, we have developed an excellent dielectric porcelain composition that has a high Q, high specific resistance, and a very small temperature change rate of capacitance, as well as an inexpensive and highly reliable high-frequency product that uses base metals such as copper as conductors. This makes it possible to realize an excellent dielectric filter and a method for manufacturing the same.

Claims (4)

[Claims] Claim 1: BaTiO3-Nd2O3-Sm2O3-
TiO2 system, Al2O3 and SiO2-PbO-CaO-
The composition consists of B2O3-Na2O-MgO-K2O system, and contains 4.0 to 8.0% by weight of BaTiO3 and Nd2O.
7.0 to 14.0% by weight of 3, 2.5 to 5% of Sm2O3
．． 0% by weight, 6.5-13.0% by weight of TiO2, Al
15.0 to 35.0% by weight of 2O3 and 24% of SiO2.
0 to 33.0 wt%, PbO 7.20 to 9.90 wt%, CaO 3.20 to 4.40 wt%, B2O3 2
．． 40-3.30% by weight, 1.20-1.6 Na2O
5 wt%, 1.20-1.65 wt% MgO and K
A dielectric ceramic composition containing 2O in a range of 0.80 to 1.10% by weight, and the total of each component being 100% by weight. 2. A dielectric filter comprising the dielectric ceramic composition according to claim 1 and a copper internal conductor. 3. A green sheet containing an organic binder and a plasticizer in an inorganic component made of the dielectric ceramic composition according to claim 1 is prepared, and a paste composition containing CuO as a main component is screen printed on the green sheet. forming a pattern by forming a pattern with the paste composition, and laminating a predetermined number of green sheets with a pattern different from the green sheet to form a multilayer, and an unfired laminate forming step in the air or an oxygen atmosphere. 3. The method according to claim 2, comprising a heat treatment step of incinerating the organic components inside the multilayer body, a reduction step of the CuO to metallic copper in hydrogen or a mixed gas of hydrogen and nitrogen, and a firing step in a nitrogen atmosphere. A method for manufacturing a dielectric filter. 4. Producing a green sheet containing an organic binder and a plasticizer in an inorganic component made of the dielectric ceramic composition according to claim 1, and screen printing a paste containing CuO as a main component on the green sheet, A step of forming an unfired laminate by repeating screen printing of a dielectric paste having the same composition as the inorganic composition of the green sheet a predetermined number of times to form a multilayer; a heat treatment step of incinerating the Cu
3. The method for manufacturing a dielectric filter according to claim 2, comprising a step of reducing O to metallic copper in hydrogen or a mixed gas of hydrogen and nitrogen, and a step of firing in a nitrogen atmosphere.