Compositions – Magnetic – With wax – bitumen – resin – or gum
Patent
1999-02-22
2000-05-16
Koslow, C. Melissa
Compositions
Magnetic
With wax, bitumen, resin, or gum
252 6253, 252 6255, 106460, 148104, 148105, 524440, 524435, 523137, 523447, 523458, 523512, 523513, 523515, H01F 126, H01F 1113, H01F 108
Patent
active
060633034
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a magnetic powder and a magnetic molded article constituted by molding the magnetic powder.
BACKGROUND ART
A resin containing magnetic material that achieves its electromagnetic characteristics by dispersing magnetic powder in a resin is used to constitute the mold core material employed in electronic parts in which specific electromagnetic characteristics are required, such as choke coils, inductors, rotary transformers, EMI elements and the like in the known art. Magnetic particles constituting such a magnetic powder are formed in an almost spherical shape to assure a sufficient degree of fluidity during injection molding.
The resin containing magnetic material described above achieves outstanding advantages such as superior dimensional accuracy and a greater degree of freedom afforded in shape since it is achieved without undergoing a sintering process, compared to magnetic oxide materials that are achieved as sintered bodies through molding and sintering. However, the electromagnetic characteristics achieved in a magnetic molded article constituted of a resin containing magnetic material obtained through the prior art technology are inferior.
For instance, if a ferrite resin achieving good injection moldability and a high degree of magnetic permeability, which is obtained by selecting an appropriate particle size distribution and an appropriate content of the ferrite powder in the ferrite resin as disclosed in Japanese Unexamined Patent Publication No. 163236/1994, is employed to constitute a magnetic molded article, a low initial magnetic permeability .mu.i of approximately 22 is achieved.
In Japanese Unexamined Patent Publication No. 204027/1994, an approach in which a heat treatment is implemented at varying temperatures for different particle sizes of magnetic particles mixed in a magnetic oxide material, is disclosed. However, the resulting magnetic molded article only achieves an initial magnetic permeability .mu.i of approximately 35 at best.
While other prior art technologies such as those disclosed in Japanese Unexamined Patent Publication No. 185540/1990, Japanese Unexamined Patent Publication No. 226799/1990, Japanese Unexamined Patent Publication No. 96202/1991, Japanese Unexamined Patent Publication No. 12029/1992, Japanese Examined Patent Publication No. 52422/1991, Japanese Unexamined Patent Publication No. 84648/1994 and the like are known, a sufficient initial magnetic permeability cannot be achieved in any of the resulting magnetic molded articles, since the dimensions of the particles mixed in the magnetic oxide material are too small, the ratio at which they are mixed is too low.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a magnetic powder and a magnetic molded article constituted by molding the magnetic powder, with which the quantity of the magnetic particles filled in a magnetic molded article can be increased, to improve the electromagnetic characteristics.
In order to achieve the object described above, the magnetic powder according to the present invention is constituted of an aggregation of resin-coated magnetic particles. The resin-coated magnetic particles include non-spherical magnetic particles which are coated with resin. According to the present invention, the term "non-spherical" covers a large variety of shapes including scale shapes, flat shapes, shapes with a portion of a sphere or ovoid missing, and shapes with indentations and projections formed on the surface.
In order to improve the electromagnetic characteristics in a resulting magnetic molded article, the weight (filling quantity) of the magnetic powder relative to the entire volume must be increased as much as possible. However, in the prior art, it has been recommended that spherical or nearly spherical magnetic particles be used in consideration of achieving a sufficient degree of fluidity of the resin when dispersing the particles in the resin and, in particular, when performing injection molding.
As explained earl
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Koslow C. Melissa
TDK Corporation
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