Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-01-19
2002-04-30
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S212000, C428S697000, C428S699000, C428S701000, C428S702000, C501S066000, C501S070000, C501S077000, C501S078000
Reexamination Certificate
active
06379805
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to low temperature-fired porcelain articles having a low dielectric constant and a high quality coefficient Q, and to electronic parts using such porcelain articles.
(2) Related Art Statement
In the high frequency circuit radio instruments such as cellular phones, top filters, interstage filters, local filters, etc. are used as high frequency circuit filters, and a laminated type dielectric filter is used as an interstage filter. An example of such a laminated type dielectric filter is disclosed in JP-A 5-243,810.
In order to produce the dielectric-laminated filter, a plurality of green sheets are produced from a powdery ceramic material to constitute a dielectric, a given electrode pattern is formed on each of the green sheets by printing with a given conductive paste. Then, a laminate is obtained by laminating the resulting green sheets, and the laminate is fired so that the conductive paste layers and the green sheets are simultaneously fired to densify the laminate.
At that time a metallic conductor having a low melting point, such as a silver-based conductor, a copper-based conductor or a nickel-based conductor is generally used as the electrode, their melting points are not more than 1,100° C., for example, and sometimes as low as around 930° C. For this reason, the dielectric needs to be sintered at a firing temperature lower than the low melting point metal constituting the electrode.
In order to decrease stray capacity, shorten the delay time and reduce the high frequency loss of an oscillator and a condenser housed, it is desired that the low temperature-fired porcelain article has a decreased dielectric constant ∈r and an increased quality coefficient Q. However, low temperature-fired porcelain articles having the optimum fired temperature of not more than 1,000° C., a dielectric constant of not more than 10, a quality coefficient Q of not less than 2500, and an absolute value of a temperature coefficient &tgr;f of the resonance frequency of not more than 30 ppm/°C. have not been available.
For example, in order to provide a low temperature-fired porcelain article capable of being fired at a low temperature and having a wide optimum firing temperature range, a high insulating resistance and a low dielectric constant ∈r, JP-B 7-98,679 proposes a low temperature-fired porcelain article containing an aluminum component in an amount of 2.0 to 10.0 wt % when calculated as Al
2
O
3
, a barium component in an amount of 20.0 to 50.0 wt % when calculated as BaCO
3
, a silicon component in an amount of 40 to 70 wt % when calculated as SiO
2
, a boron component in an amount of 1.0 to 3.0 wt % when calculated as B
2
O
3
, a chromium component in an amount of 0.3 to 3.0 wt % when calculated as Cr
2
O
3
, and a calcium component in an amount of 0.3 to 3.0 wt % when calculated as CaCO
3
. However, no measure has been recognized to control the quality coefficient Q of the low temperature-fired porcelain to not less than 2500, and porcelain articles which can be fired at optimum firing temperatures of not more than 1,000° C. have not been realized.
On the other hand, alumina and a glass-epoxy compound are used as materials for multi-layer wired substrates with low dielectric constants.
The present inventors have tried to incorporate condensers or inductors in multi-layer wired substrates made of materials having low dielectric constants. However, since the temperature coefficient &tgr;f of the resonance frequency of alumina or glass-epoxy compounded substrates is less than −60 ppm/° C., the alumina substrates or the glass-epoxy compounded substrates could not be employed for the condensers or the inductors requiring temperature compensation with high accuracy. On the other hand, low temperature-fired, BaO—SiO
2
—Al
2
O
3
-based porcelain articles have their optimum firing temperatures of not more than 1,000° C., porcelain articles having the dielectric constants of not more than 10 and the quality coefficient of not less than 2500 have not been offered. In addition, no examination has been made upon &tgr;f.
In order to provide low temperature-fired porcelain articles which enable low temperature firing with a wide optimum firing temperature range and possess high insulation resistance and low dielectric constants, for example, JP-B 7-98,679 proposes a low temperature-fired porcelain article that contains 2.0 to 10.0 wt % of an aluminum component when calculated as Al
2
O
3
, 20.0 to 50.0 wt % of a barium component when calculated as BaCO
3
, 40.0 to 70.0 wt % of a silicon component when calculated as SiO
2
, 1.0 to 3.0 wt % of a boron component when calculated as B
2
O
3
, 0.3 to 3.0 wt % of a chromium component when calculated as Cr
2
O
3
, and 0.3 to 3.0 wt % of a calcium component when calculated as CaCO
3
. However, a method has not been recognized to control the quality coefficient Q of the low temperature-fired porcelain article to not less than 2500. Further, a porcelain article which has the quality coefficient Q of not less than 2500 and which can be fired at an optimum firing temperature of not more than 950° C. has not been realized. Furthermore, a method has not been described to lessen an absolute value of the temperature coefficient &tgr;f of the resonance frequency of the low temperature-fired porcelain article.
SUMMARY OF THE INVENTION
It is an object of a first aspect of the present invention to provide a low temperature-fired BaO—SiO
2
—Al
2
O
3
based porcelain article having a dielectric constant of not more than 10 and a quality coefficient Q of 2,500. The quality coefficient Q is measured by the Hakki-Coleman method.
The low temperature-fired porcelain article according to the first aspect of the present invention comprises a barium component in an amount of 40 to 65 wt % when calculated as BaO, a silicon component in an amount of 25 to 46 wt % when calculated as SiO
2
, an aluminum component in an amount of 0.1 to 20 wt % when calculated as Al
2
O
3
, a boron component in an amount of 0.3 to 1.5 wt % when calculated as B
2
O
3
, and a zinc component in an amount of 0.5 to 20 wt % when calculated as ZnO, wherein the porcelain article has a dielectric constant &tgr;r of not more than 10, and a quality coefficient Q of not less than 2500.
It is an object of a second aspect of the present invention to provide a low temperature-fired, BaO—SiO
2
—Al
2
O
3
based porcelain article having a dielectric constant ∈r of not more than 10, a quality constant of not less than is 2500 and an absolute value of a temperature coefficient &tgr;f of a resonance frequency of not more than 30 ppm/°C. with high strength.
The low temperature-fired porcelain article comprises a barium component in an amount of 40 to 65 wt % when calculated as BaO, a silicon component in an amount of 25 to 46 wt % when calculated as SiO
2
, an aluminum component in an amount of 0.2 to 20 wt % when calculated as Al
2
O
3
, a boron component in an amount of 0.3 to 1.5 wt % when calculated as B
2
O
3
, a chromium component in an amount of 0.5 to 3.5 wt % when calculated as Cr
2
O
3
, and a zinc component in an amount of 0.5 to 20 wt % when calculated as ZnO, wherein the porcelain article has a dielectric constant ∈r of not more than 10, a quality coefficient Q of not less than 2500 and an absolute value of a temperature coefficient f of a resonance frequency of not more than 30 ppm/°C.
The following description on the zinc component, the silicon component, the aluminum component, and the boron component is also applicable to the porcelain articles according to the first and second aspects of the present invention.
When the zinc component is incorporated in an amount of not less than 0.5 wt % as calculated in the form of ZnO, the coefficient of thermal expansion of the low temperature-fired article decreases, and can be easily sintered, which enables firing at a low temperature. When the zinc component is not more than 20 wt %, reduction in the quality coefficient Q can be prevented.
When the sili
Baba Hideyuki
Kouda Yasunori
Oobuchi Takeshi
Burr & Brown
Jones Deborah
NGK Insulators Ltd.
Stein Stephen
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