Title: Dielectric ceramic composition
Abstract: A dielectric ceramic composition of high dielectric constant and low dielectric loss, which can be co-fired with Ag electrodes, is provided for use in various parts of electric and electronic appliances. Based on a base composition with a high dielectric constant, the composition comprises glass frit and optionally CuO, as represented by the following formula: a wt. % {x CaO-y.sub.1 Sm.sub.2 O.sub.3 -y.sub.2 Nd.sub.2 O.sub.3 -w Li.sub.2 O-z TiO.sub.2 }+b wt. % (ZnO--B.sub.2 O.sub.3 --SiO.sub.2 based or Li.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit)+c wt. % CuO wherein, 13.0 mol %.ltoreq.x.ltoreq.20.0 mol %; 10.0 mol %.ltoreq.y.sub.1 +y.sub.2.ltoreq.17.0 mol %; 6.0 mol %.ltoreq.w.ltoreq.11.0 mol %; 60.0 mol %.ltoreq.z.ltoreq.67.0 mol % with the proviso that x+y.sub.1 +y.sub.2 +w+z=100; 85.0 wt. %.ltoreq.a.ltoreq.97.0 wt. %; 3.0 wt. %.ltoreq.b.ltoreq.15.0 wt. %; and c.ltoreq.7.0 wt. %.
Patent Number: 6,846,767 Issued on 01/25/2005 to Kim, et al.
| Inventors:
|
Kim; Woo Sup (Kyungki-do, KR);
Hur; Kang Heon (Kyungki-do, KR);
Kim; Jong Han (Kyungki-do, KR);
Kim; Joon Hee (Kyungki-do, KR)
|
| Assignee:
|
Samsung Electr-Mechanics Co., Ltd. (Suwon, KR)
|
| Appl. No.:
|
123139 |
| Filed:
|
April 17, 2002 |
Foreign Application Priority Data
| Nov 13, 2001[KR] | 2001-70537 |
| Current U.S. Class: |
501/136 |
| Intern'l Class: |
C04B 035/465 |
| Field of Search: |
501/136
|
References Cited [Referenced By]
U.S. Patent Documents
| 5403796 | Apr., 1995 | Takahashi et al. | 501/136.
|
| 5444028 | Aug., 1995 | Takahashi et al. | 501/136.
|
| 6108192 | Aug., 2000 | Sugimoto et al. | 361/321.
|
| 6221799 | Apr., 2001 | Takase et al. | 501/136.
|
| 6385035 | May., 2002 | Matoba et al. | 361/321.
|
| 6387835 | May., 2002 | Kim et al. | 501/136.
|
Other References
"Dielectric Properties of Ca.sub.1-x SM.sub.2x/3 TiO.sub.3 Li.sub.1/2
Ln.sub.1/2 TiO.sub.3 Ceramics", by Ki Hyun Yoon et al, Jap. J. Appl.
Phys.Vol 35 (1996) pp. 5145-5149, Park 1, No. 9B, Sep. 1996.
|
Primary Examiner: Group; Karl
Attorney, Agent or Firm: Lowe Hauptman Gilman & Berner LLP
Claims
What is claimed is:
1. A dielectric ceramic composition, comprising 85.0.about.97.0 wt % of a
base composition represented by the following chemical formula 1:
x CaO-y.sub.1 Sm.sub.2 O.sub.3 -y.sub.2 Nd.sub.2 O.sub.3 -w Li.sub.2 O-z
TiO.sub.2
wherein 13.0 mol %.ltoreq.x.ltoreq.20.0 mol %; 10.0 mol %.ltoreq.y.sub.1
+y.sub.2.ltoreq.17.0 mol %; 6.0 mol %.ltoreq.w.ltoreq.11.0 mol %; 60.0 mol
%.ltoreq.z.ltoreq.67.0 mol %, with the proviso that x+y.sub.1 +y.sub.2
+w+z=100; and 3.0.about.15.0 wt % of ZnO--B.sub.2 O.sub.3 --SiO.sub.2 or
Li.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit.
2. The dielectric ceramic composition according to claim 1, further
comprising CuO in an amount of 7.0 wt % or less.
3. The dielectric ceramic composition according to claim 1, wherein
ZnO--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit comprises ZnO in an
amount of 30.about.70 wt %, B.sub.2 O.sub.3 in an amount of 5.about.30 wt
%, SiO.sub.2 in an amount of 5.about.40 wt %, and PbO in an amount of
2.about.40 wt %.
4. The dielectric ceramic composition according to claim 1, wherein the
Li.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit comprises
Li.sub.2 O in an amount of 1--10 wt %, BaO in an amount of 10.about.40 wt
%, B.sub.2 O.sub.3 in an amount of 20.about.50 wt %, and SiO.sub.2 in an
amount of 15.about.40 wt %.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric ceramic composition which is
widely used in high frequency electronic components, more particularly, to
a low-temperature cofired dielectric ceramic composition with a high
dielectric constant and a low dielectric loss.
2. Description of the Prior Art
For use in a high frequency range (.about.2 GHz), chip type components such
as LC filters, require that their electrodes be high in electrical
conductivity. Ag or Cu is selected for internal electrode due to their
high electrical conductivity. Ag and Cu have melting points of 961.degree.
C. and 1,083.degree. C., respectively, which are both much lower than
those of Ni (1,455.degree. C.) or Ag--Pd.
Dielectric material must have lower sintering temperatures than the melting
point of the internal electrode. In the case that Ag or Cu is employed as
electrodes, available dielectric materials can be therefore selected from
only a narrow range.
Generally, LTCC materials using Ag as an internal electrode are composed
mainly of glass frit in combination with ceramic fillers for improving
strength and dielectric properties. And its sintering temperature is about
900.degree. C. or lower.
However, such compositions are, for the most part, found to have dielectric
constants of 10 or less, which are too low to apply the compositions for
LC filters. For use in LC filters, dielectric compositions are required to
show a high dielectric constant, a low dielectric loss (high Q value), and
a stable temperature coefficient of resonant frequency.
For instance, dielectric ceramic compositions with high dielectric
constants allow the reduction of the size of the electrodes, making it
possible to miniaturize devices. Additionally, such dielectrics are very
useful in reducing insertion loss. Further, stable temperature
coefficients of resonant frequency are helpful in stabilizing
high-temperature properties of dielectrics.
Development of LTCC materials with high dielectric constants has largely
been investigated in two manners: one is to develop new systems that can
be sintered at 900.degree. C. or lower; the other is directed to composite
systems comprising low-temperature sintering aids or glass frit on the
basis of conventional dielectric materials of high dielectric constants.
Usually, the former is Bi-based systems. These systems, however, have
difficulty in being used in practice due to reactivity with electrodes,
and poor reproducibility.
In association with the latter, there is known a technique in which a
CaO--Sm.sub.2 O.sub.3 --Nd.sub.2 O.sub.3 --Li.sub.2 O--TiO.sub.2
composition (K. H. Yoon et. al., Jpn. J. Appl. Phys., 35[9B] 5145 (1996))
with a sintering temperature of 1,300.degree. C. or higher is combined
with the sintering aid B.sub.2 O.sub.3 --Li.sub.2 O to reduce the
sintering temperature to 1,100.degree. C. However, 1,100.degree. C. is
still too high to conduct the co-firing of Ag electrodes.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to overcome the above
problems encountered in prior arts and provide a dielectric ceramic
composition which exhibits high dielectric constant and low dielectric
loss and can be cofired with Ag electrode.
It is another object of the present invention to provide a dielectric
ceramic composition which is improved in sintering properties as well as
being controllable in high frequency dielectric properties.
In accordance with an aspect of the present invention, there is provided a
dielectric ceramic composition represented by the following chemical
formula 1:
Chemical Formula 1
a wt. % {x CaO-y.sub.1 Sm.sub.2 O.sub.3 -y.sub.2 Nd.sub.2 O.sub.3 -w
Li.sub.2 O-z TiO.sub.2 }+b wt. % (ZnO--B.sub.2 O.sub.3 --SiO.sub.2 based
or Li.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit)
wherein, 13.0 mol %.ltoreq.x.ltoreq.20.0 mol %; 10.0 mol %.ltoreq.y.sub.1
+y.sub.2.ltoreq.17.0 mol %; 6.0 mol %.ltoreq.w.ltoreq.11.0 mol %; 60.0 mol
%.ltoreq.z.ltoreq.67.0 mol % with the proviso that x+y.sub.1 +y.sub.2
+w+z=100; 85.0 wt. %.ltoreq.a.ltoreq.97.0 wt. %; 3.0 wt.
%.ltoreq.b.ltoreq.15.0 wt. %.
In accordance with another aspect of the present invention, there is
provided a dielectric ceramic composition represented by the following
chemical formula 2:
Chemical Formula 2
a wt. % {x CaO-y.sub.1 Sm.sub.2 O.sub.3 -y.sub.2 Nd.sub.2 O.sub.3 -w
Li.sub.2 O-z TiO.sub.2 }+b wt. % (ZnO--B.sub.2 O.sub.3 --SiO.sub.2 based
or Li.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit)+c wt. % CuO
wherein, 13.0 mol %.ltoreq.x.ltoreq.20.0 mol %; 10.0 mol %.ltoreq.y.sub.1
+y.sub.2.ltoreq.17.0 mol %; 6.0 mol %.ltoreq.w.ltoreq.11.0 mol %; 60.0 mol
%.ltoreq.z.ltoreq.67.0 mol % with the proviso that x+y.sub.1 +y.sub.2
+w+z=100; 85.0 wt. %.ltoreq.a.ltoreq.97.0 wt. %; 3.0 wt.
%.ltoreq.b.ltoreq.15.0 wt. %; and c.ltoreq.7.0 wt. %.
DETAILED DESCRIPTION OF THE INVENTION
Based on CaO--Sm.sub.2 O.sub.3 --Nd.sub.2 O.sub.3 --Li.sub.2 O--TiO.sub.2
with low dielectric loss and high dielectric constant, the dielectric
ceramic composition of the present invention comprises ZnO--B.sub.2
O.sub.3 --SiO.sub.2 or Li.sub.2 O--B.sub.2 O.sub.3 --SiO.sub.2 glass frit
as a sintering aid, thereby being able to be cofired with Ag electrode
patterns in addition to exhibiting a high dielectric constant and low
dielectric loss.
To the composition, CuO may be further incorporated. In the dielectric
composition, CuO acts as a sintering aid to improve the densification of
the composition, and plays a role in controlling dielectric properties at
high frequencies.
As described above, the ceramic composition of CaO--Sm.sub.2 O.sub.3
--Nd.sub.2 O.sub.3 --Li.sub.2 O--TiO.sub.2, although superior in terms of
dielectric loss and dielectric constant, cannot be cofired with Ag
electrodes because it can be sintered at 1,300.degree. C. which is much
higher than the melting point of Ag (961.degree. C.).
In accordance with the present invention, the base ceramic composition
CaO--Sm.sub.2 O.sub.3 --Nd.sub.2 O.sub.3 --Li.sub.2 O--TiO.sub.2 is
modified in the molar ratio of its constituting ingredients, and is
incorporated with a certain amount of glass frit so as to make it possible
to co-fire the ceramic composition with the Ag electrode. For use in the
present invention, the base ceramic composition CaO--Sm.sub.2 O.sub.3
--Nd.sub.2 O.sub.3 --Li.sub.2 O--TiO.sub.2 comprises CaO (x) in an amount
of 13.about.20 mol %, Sm.sub.2 O.sub.3 and Nd.sub.2 O.sub.3 (y.sub.1
+y.sub.2) in an amount 10.about.17 mol %, Li.sub.2 O (w) in an amount of
6.about.11 mol %, and TiO.sub.2 (z) in an amount of 60.about.67 mol %,
with the proviso that x+y1+y2+w+z=100.
When CaO is used at less than 13 mol %, the composition has a large
negative TCF value. On the other hand, the TCF of the composition is
excessively increased in the positive direction at more than 20 mol % of
CaO. Therefore, the compositions containing less than 13 mol % or more
than 20 mol % of CaO cannot be used in practice. For practical uses in TCF
value, that is, in the range of .+-.20 ppm/.degree. C., CaO is preferably
used in an amount of 13 .about.20 mol %.
With the sum of Sm.sub.2 O.sub.3 and Nd.sub.2 O.sub.3 (y.sub.1 +y.sub.2)
amounting to 10 mol %, the base ceramic composition shows too large a
positive TCF. On the other hand, more than 17 mol % of the sum of Sm.sub.2
O.sub.3 and Nd.sub.2 O.sub.3 causes an increase in dielectric loss and
thus deteriorates the Q value. For these reasons, the sum of Sm.sub.2
O.sub.3 and Nd.sub.2 O.sub.3 is preferably defined in the range of
10.about.17 mol %. For example, in the presence of too small amounts of
Sm.sub.2 O.sub.3 and Nd.sub.2 O.sub.3, a CaTiO.sub.3 phase that is as high
as +300 ppm/.degree. C. in TCF is formed, giving rise to an excessive
increase in the TCF of the composition. On the other hand, more than 17
mol % of Sm.sub.2 O.sub.3 and Nd.sub.2 O.sub.3 in sum, an Sm.sub.2
Ti.sub.2 O.sub.7 phase is formed as a secondary phase which leads to
drastically decreasing the Q value.
Below 6 mol % of Li.sub.2 O, there is formed Sm.sub.2 Ti.sub.2 O.sub.7
which negatively affects the Q.sub.f value. On the other hand, when the
content of Li.sub.2 O is over 11 mol %, the base ceramic composition is
excessively increased in TCF. Accordingly, the preferable amount of
Li.sub.2 O falls within the range of 6-11 mol %.
In the present invention, a glass frit composition is used to lower the
sintering temperature of the base dielectric composition to such an extent
as to fire the composition together with electrodes made of low-melting
point metal such as Ag.
Useful in the present invention is the glass frit based on ZnO--B.sub.2
O.sub.3 --SiO.sub.2 --PbO or Li.sub.2 O--BaO--B.sub.2 O.sub.3 --SiO.sub.2.
Preferably, the ZnO--B.sub.2 O.sub.3 --SiO.sub.2 --PbO based glass frit
comprises ZnO in an amount of 30.about.70 wt %, B.sub.2 O.sub.3 in an
amount of 5.about.30 wt %, SiO.sub.2 in an amount of 5.about.40 wt %, and
PbO in an amount of 2.about.40 wt %.
B.sub.2 O.sub.3 lowers the viscosity of the glass and accelerates the
densification of the dielectric ceramic composition of the present
invention. Where B.sub.2 O.sub.3 is used in an amount lower than 5 wt. %,
the dielectric ceramic composition is likely to not be sintered at lower
than 900.degree. C. With more than 30 wt % of B.sub.2 O.sub.3, the
dielectric ceramic composition has poor moisture resistance. Thus, its
amount is preferably on the order of 5.about.30 wt. % of the glass frit.
More than 40 wt % of SiO.sub.2 results in an excessive increase in the
softening temperature of the glass frit which therefore cannot act as a
sintering aid. When SiO.sub.2 is present in an amount less than 5 wt %,
its effect is not obtained. That is, a preferable amount of SiO.sub.2
falls within the range of 5-40 wt. %.
With less than 2 wt % of PbO, the glass frit has too high a softening
temperature (Ts), making no contribution to the sintering of the
dielectric ceramic composition. On the other hand, more than 40 wt. % of
PbO lowers the Ts of the glass frit to improve the densification of the
composition, but has the problem of decreasing Q value. Considering these
facts, the amount of PbO in the glass frit is defined in the range of
2.about.40 wt %.
It is preferred that ZnO is used in an amount of 30.about.70 wt %.
Excessive amounts of ZnO lead to an increase in the softening temperature
of the glass frit, making the low temperature firing impossible.
In the case of the Li.sub.2 O--BaO--B.sub.2 O.sub.3 --SiO.sub.2 based glass
frit, it preferably comprises Li.sub.2 O in an amount of 1--10 wt %, BaO
in an amount of 10.about.40 wt %, B.sub.2 O.sub.3 in an amount of
20.about.50 wt %, and SiO.sub.2 in an amount of 15.about.40 wt %.
For the same reasons as in the ZnO--B.sub.2 O.sub.3 --SiO.sub.2 --PbO based
glass frit, contents of B.sub.2 O.sub.3 and SiO.sub.2 are limited in the
Li.sub.2 O--BaO--B.sub.2 O.sub.3 --SiO.sub.2 based glass frit, but
somewhat differ from those in the ZnO--B.sub.2 O.sub.3 --SiO.sub.2 --PbO
based glass frit.
Functioning to lower the softening temperature (Ts) of the glass frit to
improve the densification of the dielectric ceramic composition, Li.sub.2
O is used in an amount of up to 10 wt. %: otherwise, the composition is
poor in moisture resistance.
When being subjected to low temperature sintering in the presence of the
glass frit containing more than 40 wt % of BaO, the dielectric ceramic
composition is drastically decreased in Q value. At less than 10 wt % of
BaO, the softening temperature of the glass frit is increased,
deteriorating the sinterability of the composition. Thus, the amount of
BaO is preferably defined within the range of 10.about.40 wt % of the
glass frit.
As for the amount of the glass frit, it is preferably on the order of
3.about.15 wt % based on the total weight of the composition. For example,
when too little glass frit is used, sintering is not performed on the
composition, which therefore becomes small in dielectric constant. On the
other hand, when too much glass frit is used, a decrease is brought about
in both dielectric constant and Q value.
In accordance with another embodiment of the present invention, CuO is used
in the dielectric ceramic composition of the present invention to improve
the densification and to control the dielectric properties. In cooperation
with the glass frit, CuO acts as a sintering aid to increase the
dielectric constant. Also, CuO plays a role in controlling the temperature
coefficient of frequency without a large change in Q value. It is
preferably used in an amount of 7 wt % or less. More than 7 wt % of CuO
causes a decrease in dielectric constant and Q value, rather than
improving the densification of the composition. More than solubility limit
in the dielectric, CuO forms a secondary phase at the interface.
Below, a description will be given of the preparation of the dielectric
ceramic composition of the present invention.
The starting materials CaCO.sub.3, Sm.sub.2 O.sub.3, Nd.sub.2 O.sub.3,
Li.sub.2 CO.sub.3 and TiO.sub.2, each with a purity of 99.0% or higher,
are weighed according to a desired composition of x CaO-y.sub.1 Sm.sub.2
O.sub.3 -y.sub.2 Nd.sub.2 O.sub.3 -w Li.sub.2 O-z TiO.sub.2, and admixed
in a wet manner.
In this regard, the wet mixing is carried out by milling the starting
materials in deionized water for about 16 hours with the aid of 3.phi.
zirconia balls in a rod mill.
The slurry thus obtained is dried and calcined. Preferably, the calcination
is carried out at 1,000-1,150.degree. C. for about 2 hours at the heating
rate of 5.degree. C./min. When the calcination temperature is lower than
1,000.degree. C., much Sm.sub.2 TiO.sub.7 remains as an intermediate
phase, giving rise to a decrease in Q value after sintering. At higher
than 1,150.degree. C., on the other hand, the powders become too coarse to
pulverize later.
After being weighed according to a desired composition, the glass frit
components are melted at 1,200-1,400.degree. C., quenched in water, and
dry-pulverized. Then, the coarse particles are finely pulverized into
powder with a particle size of 0.5.about.1.0 .mu.m in ethyl alcohol.
The base dielectric ceramic composition is admixed with the glass frit
powder composition, together with appropriate amounts of CuO in a batch,
after which the admixture is pulverized.
Following drying, the powder thus obtained was subjected to secondary
calcinations at 600-700.degree. C. The secondary calcination temperature,
which is somewhat higher than the softening temperature (Ts) of the glass
frit, makes the dielectric homogenous with the glass frit, thereby
improving the uniformity of the dielectric ceramic composition after the
sintering.
Next, the calcined powder is further broken down into a desired particle
size, mixed with a binder, and molded to a desired form such as a disc or
a sheet.
Afterwards, the electrode in a form of disc or sheet is calcined and
co-fired at less than 900.degree. C. to produce a desired device.
Having generally described this invention, an improved understanding can be
obtained by reference to certain specific examples which are provided
herein for purposes of illustration only and are not intended to be
limiting unless otherwise specified.
EXAMPLE 1
CaCO.sub.3, Sm.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Li.sub.2 CO.sub.3, and
TiO.sub.2 were weighed according to the composition of x CaO-y.sub.1
Sm.sub.2 O.sub.3 -y.sub.2 Nd.sub.2 O.sub.3 -w Li.sub.2 O-z TiO.sub.2
ZrO.sub.2, as given in Table 1, below, and admixed in deionized water for
16 hours in the presence of 3.phi. zirconia balls using a rod mill.
The slurry thus obtained was dried, roughly pulverized in a mortar, and
heated at the rate of 5.degree. C./min to a temperature of
1,000-1,150.degree. C. at which calcination was carried out for 2 hours.
Subsequently, the calcined powder was pulverized first in a mortar and then
by use of a planetary mill at 200 rpm for 30 min. After being combined
with a binder, the pulverized powder was molded into a disc by uniaxial
compression at a pressure of 2.0 ton/cm.sup.2 using a 14 mm.phi. mold. The
specimen was sintered at 1,300.degree. C. for 3 hours and measured for
dielectric constant (K), Q value, and TCF. The results are given in Table
1, below.
In Table 1, the dielectric constant (K) and Q value were measured by the
Hakki & Coleman method while the temperature coefficient of resonant
frequency (TCF) was measured by the cavity method. TCF was determined
between 20 and 85.degree. C. In this regard, the specimen was measured for
resonant frequency after being maintained at 20.degree. C. for 30 min, and
then heated to and maintained at 85.degree. C. for 30 min prior to
re-measurement for resonant frequency. With the measurements, the TCF was
determined.
TABLE 1
Compo-
sition
No. CaO Sm.sub.2 O.sub.3 Nd.sub.2 O.sub.3 Li.sub.2 O TiO.sub.2
K Q TCF
1 11.0 15.0 0.0 8.0 66 81.0 3000 -60.0
2 21.0 5.0 5.0 8.0 61.0 120 4500 50.0
3 19.6 9.8 0.0 8.8 61.8 123 4350 65.0
4 6.7 17.5 0.0 8.4 67.4 75 500 -85.0
5 19.0 11.0 0.0 5.9 64.1 110.5 450 32.0
6 11.5 9.5 4.5 11.5 63.0 130 1300 75.0
7 15.8 13.2 0.0 7.9 63.1 105 5500 15.0
8 18.0 11.8 0.0 7.8 62.4 105.3 5604 13.3
9 16.9 4.8 7.9 7.8 62.6 113.2 3750 12.6
As shown in Table 1, the base ceramic composition according to the present
invention (Nos. 7-9) have dielectric constants higher than 70 in addition
to exhibiting a Q value of 500 or higher and a TCF of .+-.20 ppm/.degree.
C.
EXAMPLE 2
After composition Nos. 7 and 8 of Table 1 were roughly pulverized in
respective mortars, 2.0.about.17.0 wt % of the glass frit was added, along
with 0.about.8.0 wt % of CuO, to 30 g of each composition as shown in
Table 4, below, in a batch. Thereafter, the admixture was pulverized again
and mixed homogeneously.
The glass frit was prepared by weighing its components according to the
compositions of Tables 2 and 3, melting them at 1,200.about.1,400.degree.
C., quenching the molten glob in water, dry-pulverizing it to coarse
particles, and milling them to a size of 0.5.about.1.0 .mu.m in ethyl
alcohol.
Next, the admixture was dried, and calcined at 600-700.degree. C. for 2
hours.
Subsequently, the calcined powder was pulverized first in a mortar and then
milled for 30 min by use of a planetary mill at 200 rpm.
After being combined with a binder, the pulverized powder was molded into a
disc by uniaxial compression at a pressure of 2.0 ton/cm.sup.2 using a 14
mm.phi. mold. The specimen was sintered at 900.degree. C. for 3 hours and
measured the dielectric constant (K), Q value, TCF and sintered density.
The results are summarized in Table 4, below.
In Table 4, comparison 2 and 13 were prepared by sintering comparison 1 and
5 at 1,050.degree. C., respectively. Also, the samples were analyzed for
sintered state and the results are summarized in Table 5.
Dielectric properties, including dielectric constant (K), Q value, and TCF,
were measured in the same manner as in Example 1.
TABLE 2
Glass Frit No. B.sub.2 O.sub.3 SiO.sub.2 ZnO PbO
Example G1 20 10 55 15
Comparative G2 3 27 60 10
Comparative G3 35 20 40 5
Comparative G4 20 3 55 22
Comparative G5 15 45 35 5
Comparative G6 20 30 49 1
Comparative G7 10 15 32 43
Comparative G8 12 10 75 3
TABLE 3
Glass Frit No. SiO.sub.2 BaO B.sub.2 O.sub.3 Li.sub.2 O
Example G9 30 25 40 5
Comparative G10 20 20 55 5
Comparative G11 40 32 19 9
Comparative G12 11 38 42 9
Comparative G13 45 20 30 5
Comparative G14 25 29 45.5 0.5
Comparative G15 16 25 45 14
Comparative G16 15 45 35 5
Comparative G17 38 8 49 5
TABLE 4
Base
Composition Glass Frit Dielectric
Dielectric Amount Amount CuO Constant
TCF
No. Kind (wt %) Kind (wt %) (wt %) (k) Q
(ppm/.degree. C.) Note
Comparative 1 7 98.0 G1 2.0 0 -- --
-- .sup.1 P. S.
Comparative 2 7 98.0 G1 2.0 0 95 1500
12.5 Sintered
Example 1 7 97.0 G1 3.0 0 70 700
11.0 Sintered
Example 2 7 95.0 G1 3.0 2.0 80 800
4.0 Sintered
Example 3 7 93.0 G1 7.0 0 74 650
8.0 Sintered
Example 4 7 86.0 G1 14.0 0 70 600
7.5 Sintered
Comparative 3 7 83.0 G1 17.0 0 55.2 200
8.0 Sintered
Example 5 7 92.0 G1 7.0 1.0 77.5 960
6.5 Sintered
Comparative 4 7 89.0 G1 3.0 8.0 55 250
9.0 Sintered
Comparative 5 7 90.0 C. G2 10.0 0.0 -- --
-- .sup.2 N. S.
Comparative 6 7 90.0 C. G3 10.0 0.0 73 550
8.6 .sup.3 P.M.R.
Comparative 7 7 90.0 C. G4 10.0 0.0 -- --
-- .sup.2 N. S.
Comparative 8 7 90.0 C. G5 10.0 0.0 -- --
-- .sup.2 N. S.
Comparative 9 7 90.0 C. G6 10.0 0.0 -- --
-- .sup.2 N. S.
Comparative 10 7 90.0 C. G7 10.0 0.0 69 100
8.3 Poor Q
Comparative 11 7 90.0 C. G8 10.0 0.0 -- --
-- .sup.2 N. S.
Comparative 12 8 98.0 G9 2.0 0 -- --
-- .sup.2 N. S.
Comparative 13 8 98.0 G9 2.0 0 90 1400
11.5 Sintered
Example 6 8 97.0 G9 3.0 0 75 900
10.0 Sintered
Example 7 8 95.0 G9 3.0 2.0 84 990
8.0 Sintered
Example 8 8 93.0 G9 7.0 0 76 800
8.0 Sintered
Example 9 8 86.0 G9 14.0 0 65 550
4.5 Sintered
Comparative 14 8 83.0 G9 17.0 0 58.5 150
-2.0 Sintered
Example 10 8 92.0 G9 7.0 1.0 79.5 960
6.5 Sintered
Comparative 15 8 89.0 G9 3.0 8.0 50 180
5.0 Sintered
Comparative 16 8 87.0 C. 13.0 0.0 75.1 780
7.5 .sup.3 P.M.S.
G10
Comparative 17 8 87.0 C. 13.0 0.0 -- --
-- .sup.1 P. S.
G11
Comparative 18 8 87.0 C. 13.0 0.0 -- --
-- .sup.1 P. S.
G12
Comparative 19 8 87.0 C. 13.0 0.0 -- --
-- .sup.1 P. S.
G13
Comparative 20 8 87.0 C. 13.0 0.0 -- --
-- .sup.1 P. S.
G14
Comparative 21 8 87.0 C. 13.0 0.0 68 570
6.2 .sup.3 P.M.S.
G15
Comparative 22 8 87.0 C. 13.0 0.0 72 120
5.8 Poor Q
G16
Comparative 23 8 87.0 C. 13.0 0.0 -- --
-- .sup.1 P. S.
G17
.sup.1 poorly sintered
.sup.2 not sintered
.sup.3 poor moisture resistance
In addition to being sintered at as low as 900.degree. C. the dielectric
ceramic compositions 1.about.10 of the present invention, as shown in
Table 4, have a dielectric constant of 70 or higher, a Q value of 500 or
higher, and a TCF of .+-.20.0 ppm/.degree. C.
In contrast, the comparative compositions 1.about.23 are not sintered at
900.degree. C. or, even if sintered, show poor dielectric properties,
including dielectric constant, Q value and TCF.
As mentioned above, the addition of glass frit and CuO to the base
composition which is sinterable at 1,300.degree. C. or higher makes it
possible for the dielectric ceramic composition of the present invention
to be cofired with Ag electrodes at as low as 900.degree. C. Thus the
dielectric ceramic compositions exhibit a dielectric constant of 60 or
higher, a Q value of 500 or higher (at 3 GHz), and a TCF of .+-.20.0
ppm/.degree. C., so that they are suitable for use in multilayered LC
filters.
The present invention has been described in an illustrative manner, and it
is to be understood that the terminology used is intended to be in the
nature of description rather than of limitation. Many modifications and
variations of the present invention are possible in light of the above
teachings. Therefore, it is to be understood that within the scope of the
appended claims, the invention may be practiced otherwise than as
specifically described.
*
