Compositions – Magnetic – Iron-oxygen compound containing
Reexamination Certificate
2000-02-22
2001-09-11
Koslow, C. Melissa (Department: 1755)
Compositions
Magnetic
Iron-oxygen compound containing
C252S062620, C252S062590
Reexamination Certificate
active
06287479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic ceramic composition and an inductor component using the same.
2. Description of the Related Art
Magnetic ceramic compositions primarily composed of Fe
2
O
3
, ZnO, NiO and CuO are known. The magnetic ceramic compositions have been used as magnetic bodies for inductor components as a countermeasure against noise and the like.
Inductor components, such as stacked chip inductors used in personal computers and the like, have low impedance in a high speed signal line at or above 75 MHz as a countermeasure against noise in this signal frequency range. However, in order to eliminate noise in a high frequency range at or above 200 MHz, inductor components must have high impedance and the rise of the impedance curve thereof must be steep.
Hence, magnetic bodies used for the inductor components described above must have low initial permeability &mgr;
i
(for example, below 10) in a high frequency range, such as at or above 200 MHz, and the threshold frequency of this initial permeability &mgr;
i
must be increased at a higher frequency range. In order to decrease deflection and delay of signals, which is specifically required for high speed signals, magnetic bodies used for inductor components must have superior temperature stability.
Conventionally, amounts of ZnO contained in magnetic ceramic compositions were decreased in order to decrease the initial permeability &mgr;
i
. However, even when ZnO is decreased to 0 molar percent, the initial permeability &mgr;
i
is decreased to only 20, and the threshold frequency thereof remains at or below 100 MHz.
In some cases, air-core coils are used for inductor components for high frequency use. In this case, the initial permeability &mgr;
i
is 1. However, the impedance thereof is low in the frequency range of 700 to 800 MHz, and sufficient effects for countermeasures against noise cannot be obtained.
Stacked chip inductors have laminated structures provided with internal conductors therein containing, for example, silver. When sintering is performed to obtain the laminated structure, consideration of suppressing undesired diffusion of components, such as silver, contained in the internal conductors is required. Hence, it is preferable that magnetic ceramic compositions used for magnetic bodies can be sintered at low temperature, such as at or below 930° C.
SUMMARY OF THE INVENTION
The present invention provides magnetic ceramic compositions and inductor components using the same, which can solve the problems and can meet the requirements described above.
The present invention specifically provides magnetic ceramic compositions and inductor components using the same, in which a small initial permeability &mgr;
i
below 10 can be obtained, and the threshold frequency of small initial permeability &mgr;
i
below 10 is not lowered in a high frequency range, such as at or above 200 MHz.
The present invention also provides magnetic ceramic compositions having superior temperature stability of the initial permeability &mgr;
i
and inductor components using the same.
The present invention also provides magnetic ceramic compositions which can be sintered at lower temperatures, such as at or below 930° C., and inductor components using the same.
To these ends, the magnetic ceramic compositions according to the present invention includes a Fe compound, a Zn compound, a Ni compound and a Cu compound as primary components, and also includes a bismuth compound and a cobalt compound as additive components.
Concerning the primary components, the composition ratio (Fe
2
O
3,
ZnO, NiO+CuO) of the Fe compound, the Zn compound, the Ni compound and the Cu compound represented by molar percent as Fe
2
O
3
, ZnO and (NiO and CuO), respectively, is in the region enclosed by point A (48.0, 0.5, 51.5), point B (48.0, 1.5, 50.5), point C (45.5, 4.0, 50.5), point D (44.0, 4.0, 52.0), and point E (44.0, 0.5, 55.5) in the ternary diagram in FIG.
1
. An absolute amount of about 8.0 to 14.0 molar percent of the Cu compound is included based on 100 molar percent of the primary components as Fe
2
O
3,
ZnO, NiO and CuO.
Concerning additive components, with respect to 100 parts by weight of the primary components as Fe
2
O
3
, ZnO, NiO, and CuO, about 0.25 to 1.0 part by weight of a bismuth compound as Bi
2
O
3
, and about 0.25 to 3.0 parts by weight of a cobalt compound as Co
3
O
4
are included.
Accordingly, by using the magnetic ceramic composition as a magnetic body, when the initial permeability &mgr;
i
is maintained to be below 10, the threshold frequency therefor is not decreased even in higher frequency ranges, such as at or above 200 MHz, whereby an inductor component having superior effects for countermeasures against noise can be obtained.
In addition, since the superior sintered state of the magnetic ceramic composition according to the present invention can be obtained by sintering at low temperatures, such as at or below 930° C., the magnetic ceramic composition can be advantageously employed for a magnetic body used for an inductor component having a laminated structure provided with internal conductors containing metal, such as silver, therein.
In the magnetic ceramic composition according to the present invention, it is preferable that about 0.5 to 3.5 parts by weight of a zirconium compound as ZrO
2
be further included as an additive component with respect to 100 parts by weight of the primary components as Fe
2
O
3
, ZnO, NiO and CuO. This permits superior temperature stability of the initial permeabilities &mgr;
i
to be achieved. Accordingly, in the inductor component using the magnetic ceramic composition as the magnetic body, deflection and delay of high-speed signals can be suppressed.
For the reasons mentioned above, the present invention can be applied to inductor components using the magnetic ceramic compositions described above as magnetic bodies inductor components having laminated structures provided with internal conductors therein.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
REFERENCES:
patent: 5906768 (1999-05-01), Kakinuma et al.
patent: 883291 (1961-11-01), None
patent: 5-326243-A (1993-12-01), None
patent: 08-325056 (1996-10-01), None
patent: 09-063826 (1997-07-01), None
patent: 09-007815 (1997-10-01), None
WPI Abstract Accession No. 1998-199123[18] & PJ100050514 A (TDK Corporation) Feb. 20, 1998 see abstract.
WPI Abstract Accession No. 1995-096583[13] & RU1355015 C Jul. 15, 1994 see abstract.
Koslow C. Melissa
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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