Ferrite material

Details Ferrite material Ferrite material

2002-03-07

2004-05-18

Koslow, C. Melissa (Department: 1755)

Compositions

Magnetic

Iron-oxygen compound containing

C252S062620, C252S062590

Reexamination Certificate

active

06736990

ABSTRACT:

TECHNICAL FIELD
A first group invention of the present invention relates to an NiCuZn-based ferrite material having an initial permeability &mgr;i of not lower than 200, particularly to a ferrite material having good temperature dependence of initial permeability, a high quality coefficient Q and high strength. The ferrite material of the present invention can be suitably used in, for example, a resin-mold-type ferrite component.
Further, a second group invention of the present invention relates to an NiCuZn-based ferrite material having an initial permeability &mgr;i of not higher than 100, particularly to a ferrite material having good temperature dependence of initial permeability, a high quality coefficient Q and high strength. The ferrite material of the present invention can be suitably used in, for example, a resin-mold-type ferrite component.
Still further, a third group invention of the present invention relates to an NiCuZn-based ferrite material as described above, particularly to a ferrite material used in a resin-mold-type ferrite component.
BACKGROUND ART
(1) In recent years, demands for components such as resin-mold-type chip inductor and stationary coil are rapidly growing in the fields of a television, a video recorder, a mobile communication device and the like. The products in such fields are demanded to have such characteristics as a small size, light weight and high accuracy, and along with the demand, demands for a decrease in tolerance and an increase in reliability to the above components are growing.
Meanwhile, a ferrite is commonly used in the core material of these components. In the case of a resin-mold-type inductor component, a compressive stress is produced in the core by resin molding, and the inductance value of the ferrite changes according to this compressive stress. Therefore, it is difficult to obtain a high-quality resin-mold-type inductor component having small inductance tolerance.
Under the circumstances, a ferrite which undergoes a small change in inductance when an external force is applied, that is, a ferrite having good stress resistance is desired. Further, to increase the reliability of a device using an inductance component, it is important to increase the reliability of the inductance component itself, specifically, to decrease the temperature dependence of initial permeability of the ferrite used in the inductance component.
In response to such a demand, a variety of improvement techniques in this field have heretofore been made. That is, in Japanese Patent Application Laid-Open No. 326243-1993, an NiCuZn-based ferrite containing 0.05 to 0.60 wt % of Co
3
O
4
, 0.5 to 2 wt % of Bi
2
O
3
and 0.10 to 2.00 wt % of a combination of SiO
2
and SnO
2
is proposed. However, since the NiCuZn-based ferrite contains a small amount of ZnO, a high initial permeability of not lower than 200 cannot be obtained.
Further, in Japanese Patent No. 267916, an NiCuZn-based ferrite containing 0.05 to 0.60 wt % of Co
3
O
4
, 3 to 5 wt % of Bi
2
O
3
and 0.10 to 2.00 wt % of SiO
2
is proposed. However, since the NiCuZn-based ferrite contains a small amount of ZnO, a high initial permeability of not lower than 200 cannot be obtained.
Further, in Japanese Patent Application Laid-Open No. 103953-1989, an NiZn based ferrite containing 0.05 to 2 wt % of Bi
2
O
3
, 0 to 1 wt % of SiO
2
and MgO or an oxide of Mn is proposed. Although the NiZn based ferrite has improved heat shock resistance, its temperature dependence of initial permeability cannot be said to be satisfactory.
Further, in Japanese Patent Application Laid-Open No. 228108-1989, an NiCuZn-based ferrite containing SiO
2
in an amount of 0.03 wt % or less, MnO in an amount of 0.1 wt % or less, Bi
2
O
3
in an amount of 0.1 wt % or less and MgO in an amount of 0.1 wt % or less to form a structure for alleviating the stress is proposed. However, since the NiCuZn-based ferrite contains a small amount of Bi
2
O
3
, its stress resistance cannot be said to be satisfactory.
Further, in Japanese Patent Application Laid-Open No. 325056-1996, an NiZn based ferrite material containing CoO, Bi
2
O
3
and SiO
2
to make a change in inductance under a load extremely small and increase a Q value at high frequency is disclosed.
However, as seen in the example disclosed in the gazette, the main composition of the example is out of the range of the main composition of the present invention and does not include MgO of the present invention. Therefore, the value of a quality coefficient Q is liable to be low.
In addition, in the case of a conventional NiCuZn ferrite containing Bi
2
O
3
and having high initial permeability, since its grain size diameter is large, a temperature coefficient is low and the Q is high, so that a ferrite component having high strength cannot be obtained.
(2) As described above, in recent years, demands for components such as resin-mold-type chip inductor and stationary coil are rapidly growing in the fields of a television, a video recorder, a mobile communication device and the like. The products in such fields are demanded to have such characteristics as a small size, light weight and high accuracy, and along with the demand, demands for a decrease in tolerance and an increase in reliability to the above components are growing.
Meanwhile, a ferrite is commonly used in the core material of these components. In the case of a resin-mold-type inductor component, a compressive stress is produced in the core by resin molding, and the inductance value of the ferrite changes according to this compressive stress. Therefore, it is difficult to obtain a high-quality resin-mold-type inductor component having small inductance tolerance.
Under the circumstances, a ferrite which undergoes a small change in inductance when an external force is applied, that is, a ferrite having good stress resistance is desired. Further, to increase the reliability of a device using an inductance component, it is important to increase the reliability of the inductance component itself, specifically, to decrease the temperature dependence of initial permeability of the ferrite used in the inductance component.
In response to such a demand, a variety of improvement techniques in this field have heretofore been made. That is, in Japanese Patent Application Laid-Open No. 326243-1993, an NiCuZn-based ferrite containing 0.05 to 0.60 wt % of Co
3
O
4
, 0.5 to 2 wt % of Bi
2
O
3
and 0.10 to 2.00 wt % of a combination of SiO
2
and SnO
2
is proposed. However, although the NiCuZn-based ferrite has improved stress resistance, Q is low and its temperature dependence of initial permeability is not satisfactory, either.
Further, in Japanese Patent No. 267916, an NiCuZn-based ferrite containing 0.05 to 0.60 wt % of Co
3
O
4
, 3 to 5 wt % of Bi
2
O
3
and 0.10 to 2.00 wt % of SiO
2
is proposed. However, as in the case of the above ferrite, its temperature dependence of initial permeability cannot be said to be satisfactory and its quality coefficient Q is also low.
Further, in Japanese Patent Application Laid-Open No. 103953-1989, an NiZn based ferrite containing 0.05 to 2 wt % of Bi
2
O
3
, 0 to 1 wt % of SiO
2
and MgO or an oxide of Mn is proposed. Although the NiZn based ferrite has improved heat shock resistance, its temperature dependence of initial permeability cannot be said to be satisfactory and its quality coefficient Q is also low.
Further, in Japanese Patent Application Laid-Open No. 228108-1989, an NiCuZn based ferrite containing SiO
2
in an amount of 0.03 wt % or less, MnO in an amount of 0.1 wt % or less, Bi
2
O
3
in an amount of 0.1 wt % or less and MgO in an amount of 0.1 wt % or less to form a structure for alleviating the stress is proposed. However, since the NiCuZn-based ferrite contains a small amount of Bi
2
O
3
, neither sufficient strength nor sufficient temperature dependence of initial permeability is obtained.
Further, in Japanese Patent Application Laid-Open No. 325056-1996, an NiZn based ferrite material containing CoO, Bi
2
O
3
and SiO
2
to make a change in inductance under a load extremely sm

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