Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2001-01-30
2002-10-29
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S688000, C501S134000
Reexamination Certificate
active
06472074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dielectric ceramic compositions suitable for use in high frequency regions, for example, microwave and milliwave regions. More specifically, the present invention relates to dielectric ceramic compositions suitable for miniaturization by laminating and co-sintering with metal electrodes, and to ceramic multilayer substrates, ceramic electronic parts and laminated ceramic electronic parts using the dielectric ceramic compositions.
2. Description of the Related Art
In recent years, high frequency dielectric ceramics have been widely used in, for example, dielectric resonators and MIC dielectric substrates. In order to miniaturize high frequency dielectric ceramics, it is required that the dielectric constant be large, the Q value be large and the temperature dependency of the dielectric constant be small.
An example of high frequency dielectric ceramic compositions is disclosed in Japanese Examined Patent Application Publication No.4-59267. Herein, the dielectric ceramic composition is represented by the general formula (Zr, Sn)TiO
4
. This dielectric ceramic composition is fired at a high temperature of 1,350° C. or more to provide a relative dielectric constant &egr;r of 38 or more and a Q value of 9,000 or more at 7 GHz.
Generally, in dielectric resonators, etc., used in high frequency regions, it is necessary to use low resistance and inexpensive metals such as Ag and Cu, as electrodes. In order to co-sinter the metal and the ceramic, the ceramic must be fired at a temperature below the melting points of these metals.
The melting points, however, of the aforementioned metals are 960 to 1,063° C., which are extremely low compared to the 1,300° C. firing temperature of the aforementioned dielectric ceramic composition. Accordingly, there is a problem in that the aforementioned dielectric ceramic composition is suitable for use in high frequencies, but cannot use these metals as inner electrode materials.
Regarding the dielectric ceramic composition disclosed in the aforementioned Japanese Examined Patent Application Publication No.4-59267, the firing temperature is as high as 1,350° C. or more. Therefore, the dielectric ceramic composition could not be co-sintered with the aforementioned low resistance metals.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a dielectric ceramic composition which can be fired at a temperature of about 1,100° C. or less, can be co-sintered with low resistance metals such as Ag and Cu, has a high dielectric constant, a high Q value and has a small temperature coefficient of the dielectric constant, and therefore is superior in high frequency characteristics, and exhibits high reliability in its environmental tolerance characteristics.
Another object of the present invention is to provide a ceramic multilayer substrate, a ceramic electronic part and a laminated ceramic electronic part which use the aforementioned dielectric ceramic composition, exhibit superior high frequency characteristics, and have superior reliability under the environment of high temperature, high humidity, etc.
According to an aspect of the present invention, a dielectric ceramic composition comprises 100 parts by weight of a primary component comprising about 22 to 43 parts by weight of TiO
2
, about 38 to 58 parts by weight of ZrO
2
and about 9 to 26 parts by weight of SnO
2
; and 3 to 20 parts by weight of glass containing at least B and Si.
Preferably, the dielectric ceramic composition further comprises about 10 parts by weight or less of NiO and about 7 parts by weight or less of Ta
2
O
5.
In a specified aspect of the present invention, the glass contains an alkali oxide, an alkaline-earth metal oxide, zinc oxide, Al
2
O
3
, B
2
O
3
and SiO
2
, and has a composition represented by the following formulae relative to 100 weight %, on a weight % basis of the entity of the glass:
10≦SiO
2
≦60;
5≦B
2
O
3
≦40;
0≦Al
2
O
3
≦30;
20≦EO ≦70 (wherein E: at least one element selected from alkaline-earth elements, Mg, Ca, Sr and Ba, and zinc (Zn)); and
0≦A
2
O≦15 (wherein A: at least one alkali metal element selected from Li, Na, and K).
Preferably, the dielectric ceramic composition further comprises about 7 parts by weight or less of CuO as an additive relative to 100 parts by weight of the primary component.
The present invention will be explained in detail as follows.
Because the dielectric ceramic composition according to the present invention contains about 3 to 20 parts by weight of the glass containing at least B and Si, relative to 100 parts by weight of the primary component, it can be fired at a temperature of about 1,100° C. or less, and can be co-sintered with low resistance metals such as Ag and Cu. In the present invention, the TiO
2
content is limited to the range of about 22 to 43 parts by weight relative to 100 parts by weight of the aforementioned primary component. When TiO
2
content is less than about 22 parts by weight, the dielectric constant of the resulting dielectric ceramic is decreased. When the content exceeds about 43 parts by weight, the temperature coefficient of dielectric constant of the resulting dielectric ceramic becomes too large on the positive side.
The ZrO
2
content is limited to the range of about 38 to 58 parts by weight. When the content is outside of this range, the temperature coefficient of the dielectric constant becomes too large on the positive side.
The SnO
2
content is limited to the range of about 9 to 20 parts by weight.
When the content is less than about 9 parts by weight, the temperature coefficient of the dielectric constant of the obtained dielectric ceramic becomes too large on the positive side and the Q value is decreased. When the content exceeds about 26 parts by weight, the temperature coefficient of dielectric constant of the obtained dielectric ceramic becomes too large on the negative side.
When the glass content is less than about 3 parts by weight relative to 100 parts by weight of the aforementioned primary component, it is not possible to fire at a temperature of about 1,100° C. or less. When the content exceeds about 20 parts by weight, the dielectric constant and the Q value of the obtained dielectric ceramic are decreased.
In the present invention, when about 10 parts by weight or less of NiO and about 7 parts by weight or less of Ta
2
O
5
are added relative to 100 parts by weight of the primary component, the Q value can be improved. When the NiO content exceeds about 10 parts by weight or the Ta
2
O
5
content exceeds about 7 parts by weight, on the contrary, the Q value of the obtained dielectric ceramic is decreased.
In the case in which the aforementioned glass component satisfies the aforementioned formulae, the sinterability at a low temperature of 1,100° C. or less is further improved, the moisture resistance of the resulting dielectric ceramic is improved, and dielectric ceramics having high Q values and high dielectric constants can be more surely obtained.
In the case in which the SiO
2
content is less than about 10 weight %, the moisture resistance of the obtained dielectric ceramic may be decreased and the Q value may be decreased. On the contrary, when the SiO
2
content of the glass exceeds about 60 weight %, the softening temperature of the glass may be increased and then the sinterability may be decreased.
In the aforementioned glass composition, in the case in which the B
2
O
3
content is less than about 5 weight %, the softening temperature of glass may be increased and then the sinterability may be decreased. When the content exceeds about 40 weight %, the moisture resistance may be decreased.
In the aforementioned glass composition, when the Al
2
O
3
content exceeds about 30 weight %, the softening temperature of glass may be increased and then the sinterability may be decreased.
Furthermore, in the case in which the additive proportion of the aforementioned alkaline-earth oxide or ZnO is less than about 22 weight %, the softening temp
Blackwell-Rudasil Gwendolyn
Jones Deborah
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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