Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
2001-12-12
2004-05-25
Nguyen, Chau N. (Department: 2831)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
Reexamination Certificate
active
06741154
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a ferrite material for a ceramic inductor, and particularly relates to a ferrite material stable and excellent in temperature characteristic and for use in ferrite sinter used as various magnetic materials, which is capable of being burnt at a low temperature, and ferrite parts such as chip inductors, chip beads parts, composite multi-layer parts, ferrite cores, etc., using the ferrite material.
For example, multi-layer chip parts such as chip inductors or chip beads parts are usually manufactured as follows. That is, a magnetic substance layer paste and an internal conductor paste are laminated integrally by thick film technology and then burnt, external electrodes are formed by use of an external electrode paste, and the thus integrated lamination is then burnt to thereby manufacture the multi-layer chip part.
In this case, Ni—Cu—Zn ferrite which can be sintered at a temperature low to be not higher than the melting point of Ag composing internal electrodes is generally used as a magnetic material for the magnetic layers.
When Ni—Cu—Zn ferrite or Ni—Zn ferrite is used, Fe
2
O
3
obtained by thermal decomposition using a hydrochloric acid pickling waste liquor for iron chloride as a starting material, or Fe
2
O
3
obtained by thermal decomposition of iron sulfate obtained from a sulfuric acid pickling waste liquor for steel is used for producing iron oxide which is one of raw materials for the ferrite. As a result, a small amount of S or Cl exists in the ferrite raw material inevitably. Thus, it is known that the ferrite affects electromagnetic properties, that is, inductance properties, or sintering properties, that is, density, in accordance with the content of S or Cl (JP-B-2867196 or JP-A-11-144934).
In addition, there is proposed a production method in which additives (sintering auxiliaries) such as glass, bismuth oxide, vanadium oxide, etc., are added to obtain a high-density ferrite sinter (see JP-B-7-24242 or JP-A-1-179402). If such additives are contained, there occurs a scattering in particle size of crystals, causing the deterioration of &mgr;, Q and temperature characteristic.
In a conventional ferrite material, a high-density sinter having few vacancies cannot be obtained at a low burning temperature, that is, at a burning temperature not higher than the melting point of Ag used for internal conductors. Thus, the magnetic properties deteriorate in a moisture resistance load test or the like.
Therefore, even if the ferrite material is burnt at a high temperature or the density is increased by use of additives, there is a problem of side effects as follows. That is, disconnection or disappearance is brought about in internal conductors, or out-of-phase is produced in the grain boundary due to diffusion of Ag, or segregation of Cu. Thus, inductance, Q, or temperature characteristic is deteriorated, or a migration phenomenon is caused by the diffused Ag. As a result, deterioration of insulation resistance or failure due to short-circuit is brought about.
A ferrite material is generally obtained by mixing an iron compound and other ferrite constituent element compounds, and burning this mixture provisionally. In this provisionally burning process, it is known that the solid phase reaction rate to form spinel crystals varies in accordance with the content of S or Cl contained in the ferrite mixture powder (See JP-A-11-144934). Due to a difference of this reaction rate, a raw material or an intermediate product is residual or out-of-phase is produced by segregation of the raw material or the intermediate product by thermal dissociation. As a result, the powder composition is made uneven to have a bad influence on the sinter density or the magnetic properties.
It is also known that the content of S or Cl residual in powder obtained by pulverizing the powder after temporary burning affects the magnetic properties (see JP-B-2867196). This S or Cl is contained in the ferrite constituent element compounds.
SUMMARY OF THE INVENTION
It is an object of the present inventors to provide a ferrite material which is an Fe—Ni—Cu—Zn—Mg ferrite material or an Fe—Ni—Cu—Zn ferrite material, the S and Cl contents of which are regulated so that the ferrite material provides a high density and a small temperature characteristic for multi-layer chip parts and magnetic cores without using any additive.
In order to attain the foregoing object, the present inventors have found that by regulating the S and Cl contents of ferrite powder in a ferrite material as shown in the following paragraphs (A1) to (A3), it is possible to provide a ferrite material which provides a high density without using any additive, and has a small temperature characteristic in spite of the high density, and it is possible to provide high-performance ferrite parts such as chip inductors, chip beads parts, composite multi-layer parts, ferrite cores, etc., as shown in the following paragraphs (A4) to (A6), by use of this ferrite material.
(A1) In an Fe—Ni—Cu—Zn—Mg ferrite material, a sulfur content of ferrite powder in a raw material stage is in a range of from 300 ppm to 900 ppm on S basis and a chlorine content of the ferrite powder is not higher than 100 ppm on Cl basis, while a sulfur content of a ferrite sinter after burning is not higher than 100 ppm on S basis and a chlorine content of the ferrite sinter is not higher than 25 ppm on Cl basis.
(A2) In an Fe—Ni—Cu—Zn ferrite material, a sulfur content of ferrite powder in a raw material stage is in a range of from 300 ppm to 900 ppm on S basis and a chlorine content of the ferrite powder is not higher than 100 ppm on Cl basis, while a sulfur content of a ferrite sinter after burning is not higher than 100 ppm on S basis and a chlorine content of the ferrite sinter is lower than 10 ppm on Cl basis.
(A3) In the ferrite material defined in the paragraph (A1), the ferrite material has a composition of Fe
2
O
3
ranging from 25 mol % to 52 mol %, ZnO of 40 mol % or lower, CuO of 20 mol % or lower, NiO of 65 mol % or lower, and MgO occupying a remainder.
(A4) A chip part is constituted by a chip inductor or a chip beads part configured by laminating ferrite magnetic layers and internal conductors, wherein the ferrite magnetic layers are composed of a ferrite material defined in any one of the paragraphs (A1) to (A3).
(A5) A composite multi-layer part is constituted by at least an inductor portion configured by laminating ferrite magnetic layers and internal conductors, wherein the ferrite magnetic layers are composed of a ferrite material defined in any one of the paragraphs (A1) to (A3).
(A6) A ferrite core is constituted by a ferrite material defined in any one of the paragraphs (A1) to (A3).
It is therefore another object of the present invention to provide a ferrite material which is constituted by an Ni ferrite material providing a high density and a small temperature characteristic for a multi-layer chip part and a magnetic core without using any additive.
In order to obtain the foregoing object, the present inventors have found that ferrite materials capable of attaining the object can be provided as shown in the following paragraphs (B1) and (B2), and ferrite parts capable of attaining the object can be provided as shown in the following paragraphs (B3) to (B5).
(B1) A ferrite material constituted by an Ni ferrite material using a nickel compound as a raw material, the nickel compound having a specific surface area in a range of from 1.0 m
2
/g to 10 m
2
g and a sulfur content in a range of from 100 ppm to 1,000 ppm on S basis.
(B2) A ferrite material according to the paragraph (B1), wherein the Ni ferrite material has a composition of Fe
2
O
3
ranging from 25 mol % to 52 mol %, ZnO ranging from 0 mol % to 40 mol %, CuO ranging from 0 mol % to 20 mol %, NiO ranging 1 mol % to 65 mol %, and MgO occupying the remainder.
(B3) A chip part constituted by a chip inductor or a chip beads part configured by laminating ferrite magnetic layers and internal conductors; wherein the ferrite magnetic layers is comp
Kawasaki Kunihiko
Momoi Hiroshi
Sato Takahiro
Suzuki Takashi
Nguyen Chau N.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
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