Compositions – Magnetic – With wax – bitumen – resin – or gum
Reexamination Certificate
2000-10-24
2003-09-16
Koslow, C. Melissa (Department: 1755)
Compositions
Magnetic
With wax, bitumen, resin, or gum
C252S062550
Reexamination Certificate
active
06620337
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic interference repressor for preventing unwanted electronic waves from leaking out of electronic equipments, or for providing interferences between internal circuits and influences of miss-operation caused by external electronic waves. In practically, the present invention relates to electromagnetic interference repressor formed by composite magnetizer consisting of organic binder having soft magnetic powder dispersed therein.
Recently, an importance of a measure devised to deal with electromagnetic environmental problems in electronic equipments is recognized increasingly. This is supported by a background in which many kinds of electronic equipments provide circuits with higher densification than before and both active and passive elements each consisting of a semiconductor device, and the like, which radiate dielectric noise are congested increasingly. These are because electronic devices such as digital electronic equipments and the like aim at responding to requirements of accelerating circuit signal processing speed, higher frequency, higher performances of multifunction, down sizing and lower profiling of product configuration, in the back ground.
As a result, it is often caused to occur that normal operation of equipments are disturbed. This is caused by increase of line-to-line coupling due to electrostatic coupling and electromagnetic coupling and also by interference of radiation noise. In some cases, the noise may affect other external equipments.
As countermeasures against noise caused by electronic devices with higher processing speed, more advanced function and higher density, particularly, a countermeasure against noise caused in quasi-microwave band, installation of low pass filter, shielding and the like can be taken. However, a countermeasure by components requires space for installation in the electronic device and needs to consider down sizing and low profiling in design phase. The counter measure by components is therefore not suitable for an urgent measure. In addition an inductance component contributes to real number portion magnetic permeability &mgr;′ and is insufficient for inductance in current quasi-microwave band. Further, in the event of conducting an inadvertent shielding, secondary electromagnetic coupling may be induced.
In response to the problems, the above-mentioned composite magnetizer sheet for repressing electromagnetic interference has been proposed as one of countermeasures against noise in quasi-microwave band. For example, proposals are made about composite magnetizer sheets capable of repressing electromagnetic interference in unexamined Japanese Patent Publication No. Hei 7-212079 and unexamined Japanese Patent Publication No. Hei 7-183911.
The above-mentioned composite magnetizer sheets correspond to quasi-microwave band and are capable of reducing permeability of radiation noise and secondary electromagnetic coupling as wave absorbers using high real number portion magnetic permeability &mgr;′ and imaginary number portion magnetic permeability &mgr;″ with a wide spectrum. Accordingly, it is possible to lighten the burden of the anti-noise measure and product development and to avoid impediments to achieve down sizing and higher densification of a circuit.
Further, in the market, a component of an anti-noise measure which is easy to use similar to the above-mentioned composite magnetizer and is capable of corresponding to retrofit components is required. The component of an anti-noise measure is preferred to have frequency band capable of component correspondence, that is, low frequency between about 10 to about 100 MHz in quasi-microwave band. Further, in the circumstance that down sizing of the electronic equipments is proceeding, the composite magnetizer sheet is required to have lower profiling corresponding to the above-mentioned quasi-microwave band.
The above-mentioned composite magnetizer sheet utilized for quasi-microwave band can provide less magnetic permeable ratio as the frequency becomes lower. Accordingly, providing lower profiling in configuration is limited and effect of repressing the electromagnetic interference reduces, as it is understood from the rise frequency of &mgr;″. As another anti-noise measure which may be taken in small electronic equipments such as a mobile communications equipment, and the like, installing ferrite or rubber ferrite may be acceptable in idea. However, in most events, ferrite can not be installed because of the problems of a possibility to be cracked or a difficulty of placement. On the other hand, rubber ferrite which has less possibility to be cracked can not repress noise sufficiently, even though a space for installation is reserved.
Components such as coils, filters, and the like are usable in the frequency of a lower side and a higher side than the spectrum between about 10 to about 100 MHz. However, currently, no anti-noise measure which is easy to be used in the above-mentioned frequency band is found. Even if a component corresponding to such an anti-noise measure is found, change of design of a substrate, and the like requires a great deal of costs and man-hour.
To solve these problems, it becomes necessary to provide a composite magnetizer sheet adoptable to the spectrum of lower frequency between about 10 to about 100 MHz and capable of expressing the electromagnetic interference repressing effect even in the lower profiling thereof.
In order to provide such a composite magnetizer sheet, it becomes indispensable to enhance magnetic permeability &mgr;′ and &mgr;″ and depress magnetic resonance frequency. In response to these requirements, for example, a proposal is made about a composite magnetizer sheet in which the repressing effect in FM band between about 10 to about 100 MHz is improved and which is adjusted to lower profiling in unexamined Japanese Patent Publication No. Hei 10-168273. Improvements of the electromagnetic interference repressing effect and lower profiling in configuration has been achieved by using the technologies disclosed in the above-mentioned unexamined Japanese Patent Publication.
Here, description is made about an example of methods for forming the above-mentioned composite magnetizer. As methods for forming the above-mentioned quasi-microwave band composite magnetizer sheet, there are a wet process in which a blended and agitated slurry regime admixture of flat soft magnetic powder, binder and solvent for dissolve the binder is formed in membrane by using doctor blade, and the like, and a dry process in which an admixture of flat soft magnetic powder and binder is kneaded by kneader, and the like, and is formed by roll, and the like.
Further, in the method for manufacturing a composite magnetizer disclosed in the above-mentioned unexamined Japanese Patent Publication No. Hei 10-168273, flat soft magnetic powder in which stress-strain is eliminated is formed in sheets by wet process in order not to cause a strain to the flat soft magnetic powder in the forming process and pressure is added on the sheet surfaces in vertical direction by press, thus high density is achieved. Accordingly, it is possible to enhance the electromagnetic interference repressing effect in FM band and to correspond to lower profiling.
Even though the effect of repressing noise with frequency between about 10 to about 100 MHz is enhanced and profiling of the configuration become lower by the method disclosed in unexamined Japanese Patent Publication No. Hei 10-168273, it is possible to obtain a composite magnetizer having electromagnetic interference repressing effect reserved therein. However the composite magnetizer obtained by the above-mentioned method provides flame resistance insufficiently.
In addition, magnetic permeable property can not be obtained sufficiently only by coating, and in the event the flat soft magnetic powder is pressed for increasing fill factor to reserve high magnetic permeability, the flat soft magnetic powder gets strain in the r
Ono Norihiko
Yoshida Shigeyoshi
Koslow C. Melissa
McGinn & Gibb PLLC
Tokin Corporation
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