JPH09306716A - Sintered ferrite material and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered ferrite material which has a high saturation magnetic flux density and a small temperature coefficient of initial permeability. SOLUTION: In this method, a sintered ferrite material is manufactured by using Fe2 O3 , NiO, ZiO and CuO as principal components, and adding at least one of PbO and HBO3 at 0.00211-0.00528mol% or Bi2 O3 at 0.00101-0.00253mol%, and at least one of SiO2 , Cr2 O3 , Al2 O3 , SnO2 and WO3 at 0.00392-0.00982mol, to the principal components at 100mol%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite sintered body and a method for manufacturing the same, and more particularly, to a ferrite sintered body for a chip inductor having high saturation magnetic flux density and a small temperature coefficient of initial permeability. , And a manufacturing method thereof.

[0002]

2. Description of the Related Art Chip inductors have various inductances, and one characteristic that determines their performance is the allowable current. The permissible current is determined by itself by determining the shape and material properties of the ferrite core that constitutes the chip inductor.

For example, Fe ₂ O ₃ , NiO, ZnO, CuO
A characteristic curve A in FIG. 1 shows the relationship between the inductance of the drum core shape and the permissible current, which is a ferrite sintered body in which PbO and SiO ₂ are added to the main component. The variation of the inductance is determined by the number of windings wound around the drum core. The larger the number of windings, the larger the inductance, but the smaller the allowable current. Therefore,
The relationship between the allowable current and the inductance in a drum core shape having a certain shape, for example, the above-mentioned ferrite sintered body, has a characteristic value on the characteristic curve A in FIG.

Conventionally, as a ferrite sintered body used for a chip inductor, Japanese Patent Publication No. Sho 60-21939 discloses that "a nickel-zinc-copper-based ferrite is the main component, and PbO is 3 wt% or less and SnO ₂ is an auxiliary component. "Oxide magnetic material containing 2 wt% or less", and Japanese Patent Publication No. 61-685, "Fe ₂ O ₃ contains 51.8 to 61.2 parts and NiO contains 12.8 to 15.2.
Parts, CuO 5.3 to 6.3 parts, MnO 7.0 to 8.3 parts, V ₂ O ₅
3.8-4.5 parts, PuO 6.3-15.9 parts, SiO ₂ 0.3-
Dielectric ceramic material having a composition of 0.7 part, 0.002 to 0.01 part of Al ₂ O _{3 and} 0.9 to 2.2 part of ZnO ”, and JP-A-1-1016
In the 09 publication, "31-46 mol% Fe ₂ O ₃ , 15-29 mol% Z
nO, the balance is NiO and CuO, and a spinel type composition in which the molar ratio of NiO is higher than the molar ratio of CuO,
0.05 to 1.0 wt% of Co ₃ O ₄ as a small amount component, or an equivalent amount of cobalt oxide or cobalt carbonate,
And a magnetic material for high frequency, which contains 0.05 to 4.0 wt% of SiO _{2 and} has little loss even at a high frequency of 1 MHz or more. "
In 93667 JP "25 to 45 mol% of Fe ₂ O _3, 0~20mol% of ZnO, the remainder is NiO and CuO, the molar ratio of NiO is a large spinel composition than the molar ratio of CuO, Magnetic material for high frequency with small loss even at high frequency of 1 MHz or more containing 0.1 to 12 wt% of Bi ₂ O ₃ and 0.05 to 4.0 wt% of SiO ₂ as small amount components ”, and JP-A-4-61.
No. 203 gazette, "A ferrite element in which a copper conductor is integrally fired in a non-oxidizing atmosphere as a copper conductor to form a copper conductor inside the ferrite base, and the raw material composition of the ferrite base is nickel-zinc ferrite 100 Copper conductor integrated firing type ferrite element in which PbO component is added in a ratio of 0.3 parts by weight or more and 5.0 parts by weight or less with respect to parts by weight "or" The ferrite base as a copper conductor is integrally fired in a non-oxidizing atmosphere and the inside of the ferrite base is integrated. A ferrite element in which a copper conductor is formed on the base material, wherein the ferrite base material composition is Pb based on 100 parts by weight of nickel-zinc ferrite.
O component is 0.3 parts by weight or more and 5.0 parts by weight or less, B ₂ O ₃ component is 0.
A copper conductor integrated firing type ferrite element in which a proportion of 03 parts by weight or more and 1.5 parts by weight or less and a SiO ₂ component is added by 0.03 parts by weight or more and 1.5 parts by weight or less, and "F
e ₂ O ₃ 40 to 50 mol%, ZnO 10 to 35 mol%, CuO
3-10 mol% and the balance NiO ferrite material, B
A ferrite material containing 0.03 to 2 wt% of at least one of i ₂ O ₃ and PbO, the grain boundaries of the crystal structure of which are Bi ₂
Formed of an amorphous layer composed of O ₃ , PbO and impurities,
Thermal shock resistant ferrite material with grain boundary thickness of 2 to 50 nm "
Have been proposed respectively.

Further, as a method for producing ferrite, Japanese Patent Application Laid-Open No. 47-8176 discloses that a fine ferrite-forming starting mixture is formed into an object having a desired shape, compressed, and then sintered to form a polycrystalline ferrite body. In manufacturing
BaF ₂ ; SrF ₂ ; B, Bi, Ca, Cu, Mg, P
A certain amount of one kind of particle growth promoting substance selected from oxides of b, Si, V and Fe ₃ (PO ₄ ) ₂ or a mixture of these substances is added in a predetermined amount in the manufacturing stage before sintering, and A method for producing a polycrystalline ferrite body, which is selected so as to obtain a crystal having a relationship with the sintering temperature and having an average grain size of 50 μm or more ”has been proposed.

[0006]

In recent years, along with the miniaturization of electronic equipment, the inductor has also been miniaturized. However, there is a problem that the allowable current, which is the characteristic performance of the inductor, is reduced by simply reducing the size.

For example, Fe ₂ O ₃ , NiO, ZnO, CuO
If a characteristic curve A of FIG. 1 is a characteristic of a conventional ferrite sintered body in which PbO and SiO ₂ are added to the main component, and the characteristic of the conventional product such as the shape of the drum core is 80, the dimension of each part of the drum core is, for example, 80 When the size is reduced to be%, the characteristic becomes the characteristic curve B in FIG.

In order to make the allowable current of the characteristic performance correspond to the characteristic curve A of FIG. 1 even if the inductor is miniaturized, as long as the shape of the inductor is determined, the shortage in which the characteristic value is lowered by the material is compensated. There must be. In other words, an inductor having such a performance that it can pass the characteristic curve C of FIG. 1 is naturally required if it has the same shape.

In order to increase the permissible current with the same inductor, a material that does not easily cause magnetic saturation, that is, a high magnetic flux density material is required.

However, if the material of the conventional inductor is designed so as to have a high magnetic flux density, the temperature coefficient of the inductance becomes large and the product becomes a defective product.

Therefore, a material having a high saturation magnetic flux density and a small temperature coefficient of inductance is required.

Regarding the characteristics (saturation magnetic flux density, temperature characteristics) of the proposed conventional ferrite sintered body, there are materials having a high (large) saturation magnetic flux density, but the temperature coefficient of μiac is also large. Further, the material having a small μiac temperature coefficient had a small saturation magnetic flux density. Therefore, there is no material that satisfies both characteristics, that is, has a high saturation magnetic flux density and a small μiac temperature coefficient.

The present invention has a high saturation magnetic flux density and μia.
An object of the present invention is to provide a ferrite sintered body of a material having a small temperature coefficient of c and a method for manufacturing the same.

[0014]

Means for Solving the Problems As a result of earnest studies to achieve the above-mentioned object, the present inventor found that a magnetic material handbook [Asakura Shoten Co., Ltd., December 15, 1984, fifth edition], page 617
9.17 “Spontaneous magnetization of M-Zn binary ferrite (OK) E.
W.Gorter: Philips Res. Rep. 9 (1954) 295. ”Was focused on the relationship between the ferrite composition in the multi-component ferrite and the molecular magnetic moment. Then, it was found that the composition of the material having a high magnetic flux density can be achieved by setting the combination of nickel ferrite and zinc ferrite in the vicinity of 1: 1. The ferrite sintered body and the manufacturing method thereof according to the present invention are made based on the above findings.

The ferrite sintered body of the present invention comprises Fe ₂ O ₃ ,
NiO, ZnO, CuO as the main component
Relative mol%, PbO, at least one of from 0.00211 to 0.00528 mole% of H ₃ BO _3, or Bi ₂ O ₃ 0.0010
1 to 0.00253 mol%, and SiO ₂ , Cr ₂ O ₃ , Al ₂ O
_At least one of ₃ , ₃ , SnO ₂ , and WO ₃ is 0.00392-
It is characterized in that 0.00982 mol% was added.

The ferrite sintered body according to claim 2 of the present invention comprises Fe ₂ O ₃ , NiO, ZnO and CuO, and has a composition ratio of ferric oxide and an oxide of a divalent metal. 47 ~ 51
Mol%: 53-49 mol%, and the composition ratio of nickel ferrite and zinc ferrite is 18.7-25.5 mol%: 2
The composition is composed of 9.0 to 18.6 mol% as a main component, and at least one of PbO and H ₃ BO ₃ is added to 0.00211 to 0.00528 mol% or Bi ₂ O ₃ with respect to 100 mol% of the main component.
0.00101 to 0.00253 mol%, and SiO ₂ , Cr
It is characterized in that at least one kind of ₂ O ₃ , Al ₂ O ₃ , SnO ₂ , and WO ₃ is added in an amount of 0.00392 to 0.00982 mol%.

The method for producing the ferrite sintered body of the present invention is as follows:
_{Fe 2 O 3, NiO, ZnO} , relative to ferrite material 100 mole% composed mainly of CuO, PbO as a secondary component, H ₃
From 0.00211 to 0.00528 mole% of at least one class of the BO _3, or at least one of Bi ₂ O ₃ of from 0.00101 to 0.00253 mol%, and _{SiO 2, Cr 2 O 3,} Al 2 O 3, SnO 2, WO 3 After adding 0.00392 to 0.00982 mol% of the type, the powder obtained by calcination and pulverization is further finely pulverized into a fine powder having a particle size of 1.4 microns or less, and the fine powder is molded to obtain a molded body. Is formed and the molded body is fired.

[Operation] 1. High magnetic flux density The composition ratio of ferric oxide and oxide of divalent metal is set to about 1: 1 and the composition ratio of nickel ferrite and zinc ferrite is set to about 1: 1. It is possible to achieve a high magnetic flux density.

2. Control of temperature coefficient of μiac μiac∝Ms ² / K Equation 1 In Equation 1, μiac is initial permeability, Ms is magnetic moment,
K represents a magnetocrystalline anisotropy constant. Since the magnetic moment Ms is determined by the composition of nickel ferrite and zinc ferrite, the temperature coefficient is controlled by adjusting the crystal magnetic anisotropy constant K of the denominator. In general,
The crystal magnetic anisotropy constant K rapidly approaches zero as the measurement temperature rises, and as a result, the temperature coefficient of the initial magnetic permeability μiac increases.

By using a high melting point oxide and a low melting point oxide as sub-components added to the main component, the high melting point oxide is precipitated at the grain boundary and grain growth is suppressed, whereby the magnetocrystalline anisotropy is increased. It is considered that the constant K is prevented from changing with temperature.

3. Crystal densification By strengthening crushing rather than ball mill crushing (particle size 1.6 micron or more), and making the particle size 1.4 micron or less,
It is possible to prevent the generation of pores in the crystal during sintering, and it is possible to densify the crystal. Thereby, the saturation magnetic flux density can be increased.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In the ferrite sintered body of the present invention, at least one of PbO and H ₃ BO ₃ added to 100 mol% of Fe ₂ O ₃ , NiO, ZnO, and CuO is 0.00211 to 0.00528 mol. %, Or Bi ₂ O ₃ of 0.00101
～0.00253 mol%, and _{SiO 2, Cr 2 O 3,} Al
_At least one of ₂ O ₃ , SnO ₂ , and WO ₃ is 0.0039
2 to 0.00982 to that the mol%, PbO, at least one additive amount is less than 0.00211 mol% of H ₃ BO _3, or the addition amount of Bi ₂ O ₃ is the effect of sintering promoting less than 0.00101 mol% The content of at least one of PbO and H ₃ BO ₃ exceeds 0.00528 mol%, or Bi ₂ O ₃
If the addition amount of Pb exceeds 0.00253 mol%, the values of μiac and Bs become small. In addition, SiO ₂ , Cr ₂ O ₃ ,
If the addition amount of at least one of Al ₂ O ₃ , SnO ₂ and WO ₃ is less than 0.00392 mol%, there is no effect of reducing the temperature coefficient of μiac, and if the addition amount exceeds 0.00982 mol%, the values of μiac and Bs are It gets smaller.

Fe ₂ O ₃ , N of the ferrite sintered body of the present invention
In the main component composed of iO, ZnO, and CuO, the composition ratio of ferric oxide and divalent metal oxide is around 1: 1, that is,
47 to 51 mol%: 53 to 49 mol%, and the composition ratio of nickel ferrite and zinc ferrite is about 1: 1,
That is, the reason why the composition is composed of 19.7 to 26.9 mol%: 22.1 to 29.3 mol% is to increase the value of Bs and also the value of μiac.

In the method for producing a ferrite sintered body of the present invention, after adding subcomponents to the main component, calcining and pulverizing the pulverized product, the pulverized product is further pulverized to have a particle size of 1.4 microns or less. This is to eliminate pores in the crystal grains, densify the crystal, and increase Bs.

After the fine powder is molded to form a compact, the compact is fired to produce a ferrite sintered body at a firing temperature of about 980 to 1070 ° C.

Next, the control of the high magnetic flux density material, the temperature coefficient of μiac, and the control of the particle size will be described in more detail.

1. High Magnetic Flux Density Material The composition of a material having a high magnetic flux density can be achieved by using a combination of nickel ferrite and zinc ferrite in the vicinity of 1: 1.

The ferrite reaction is expressed by the following equations 2, 3,
As shown in 4, the ferric oxide and the oxide of the divalent metal react with each other at a ratio of 1: 1. Therefore, by adjusting the amount of ferric oxide to approach this, a higher magnetic flux density can be obtained. It becomes a material.

NiO + Fe ₂ O ₃ = NiO.Fe ₂ O ₃ Formula 2 ZnO + Fe ₂ O ₃ = ZnO.Fe ₂ O ₃ Formula 3 (1-X) NiO.Fe ₂ O ₃ + (1 + X) ZnO.Fe ₂ O ₃ = NiO (1-X) · ZnO (1 + X) · Fe ₂ O ₃ Formula 4 In Formula 4, the value of X is NiO: Fe ₂ O ₃ or ZnO: Fe ₂
It represents the excess and deficiency mole number of O ₃ , and its range is determined from the scope of the claims of the present invention.

FIG. 2 shows the relationship between the NiO content (mol%) in the ferrite composition and the saturation magnetic flux density Bs (mT). As is clear from FIG. 2, the saturation magnetic flux density Bs (mT) tends to increase as the amount of NiO (mol%) increases, and there is a peak of the saturation magnetic flux density Bs in the vicinity of 23 to 27% of NiO.

FIG. 3 shows the relationship between the NiO content (mol%) in the ferrite composition and μiac. As is clear from FIG. 3, contrary to the characteristics shown in FIG. 2, μiac tends to decrease as the NiO content (mol%) increases.

On the other hand, it is necessary to make μiac ≧ 200 and Bs ≧ 3500 from the characteristics when the sample shape is a drum core shape product. Therefore, the NiO composition is 18.7 mol% ≦ N.
iO ≦ 25.5 mol% is required.

FIG. 4 shows the relationship between the amount of Fe ₂ O ₃ (mol%) in the ferrite composition and the saturation magnetic flux density Bs (mT). As is clear from FIG. 4, the Fe ₂ O ₃ content is 50 mol%
There is a peak of the saturation magnetic flux density Bs in the vicinity. Further, the composition of Fe ₂ O ₃ content is 47.3 mol% because of the above requirement of Bs ≧ 3500.
≦ Fe ₂ O ₃ ≦ 50.9 mol% is required.

Further, the ferrite sintered body of the present invention has the meaning that it is excellent in the DC superposition characteristic or the permissible current becomes large only when it is used in the open magnetic circuit.

2. Control of μiac temperature coefficient Fe ₂ O ₃ 48.75 mol%, NiO 21.25 mol%, ZnO 2
The main component is a composition of 5 mol% and CuO 5 mol% in total of 100 mol%, the following additives are added to the main component, and the mixture is wet-mixed in a ball mill for 2 hours.

Additives for controlling the temperature coefficient include SiO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , SnO ₂ and WO _3.
And other high melting point oxides, and at least one of these high melting point oxides is 0.00
It is effective to add 392 to 0.00982 mol%. However, since the AC initial permeability μiac and the saturation magnetic flux density Bs become small only by this, PbO, H ₃ BO _3, etc. are added as a low melting point oxide in order to make up for these, and the main component is 100 mol. %, At least one of PbO and H ₃ BO ₃ is added in an amount of 0.00211 to 0.00528 mol%, or Bi ₂ O ₃ is added in an amount of 0.00101 to 0.00253 mol%.

That is, by adding a high-melting point oxide and a low-melting point oxide as auxiliary components to the main component within a specific range, the temperature coefficient of μiac (αμr ≦) which is a desired characteristic is added.
10) can be obtained.

3. Control of particle size In addition to the control of the high magnetic flux density material and the temperature coefficient, the control of the particle size during pulverization of the calcined powder is also an important point.

FIG. 5 shows μiac in normal grinding and fine grinding.
The relationship between the temperature coefficient and the saturation magnetic flux density Bs is shown.

By controlling the particle diameter to 1.4 microns (μm) or less, the saturation magnetic flux density Bs (mT) can be further increased while maintaining the same temperature coefficient (eg, αμr = 6) as shown in FIG. Can be done.

A more detailed description will be given. The particle size of the powder pulverized by the ordinary ball mill is 1.7 μm, and the relationship between the temperature coefficient of the ordinary pulverized μiac produced by using this powder and the saturation magnetic flux density Bs is represented by a circle in FIG. It shifts to the left like the line. On the other hand, for example, the relationship between the temperature coefficient of the finely pulverized μiac produced by using the powder finely pulverized with an attritor to 1.4 μm or less and the saturation magnetic flux density Bs is shown by the line indicated by the ● in FIG. Is shifting to the right. That is, as shown by the arrow in FIG.
If the temperature coefficient is the same (for example, αμr = 6), the saturation magnetic flux density Bs (mT) is increased by pulverizing.

[0042]

EXAMPLES Specific examples of the present invention will be described together with comparative examples.

Example As main components, Fe ₂ O ₃ 48.75 mol%, NiO 21.25 mol%, ZnO 25 mol%, CuO 5 mol%, total 100 mol%.
As a main component, and at least one of SiO ₂ , Cr ₂ O ₃ , SnO ₂ , and WO ₃ , which are high melting point oxides, and PbO and H ₃ B, which are low melting point oxides, as secondary components.
Powder 100g of at least one or Bi ₂ O ₃ was obtained by blending the composition as shown in Table 1 (sample No. 6-29) of the O ₃
Was wet mixed with a 0.5 liter ball mill for 2 hours to obtain a mixture.

The mixture was dried in an air atmosphere at a temperature of 150 ° C., dried, and calcined in an air atmosphere at a temperature of 900 ° C., and then pulverized again in a ball mill for 2 hours. Manufactured by the trade name MA01S) and pulverized to a fine powder until the particle size becomes 1.4 microns or less.

After drying the fine powder at a temperature of 150 ° C. in the air atmosphere, 40 g of the fine powder and 4 g of a polyvinyl alcohol (PVA) solution as a binder were added and mixed, and the mixture was granulated and molded and processed. Toroidal core for measuring electromagnetic characteristics (outer diameter φ28.1 mm, inner diameter φ
21.1mm), and drum-shaped core for measuring DC superposition characteristics and temperature characteristics (outer diameter φ2.10mm, height 2.32m)
m, central axis 0.93 mm, and brim thickness 0.46 mm).

The toroidal cores and the drum-shaped cores thus formed were fired in the air at the firing temperatures shown in Table 1 to obtain ferrite sintered bodies having different subcomponent compositions (Sample Nos. 6 to 29). Was produced.

Comparative Example Fe ₂ O ₃ 46.13 mol%, NiO 18.15 mol%, ZnO 3
2.82 mol%, CuO 2.89 mol%, a total of 100 mol% of the composition as the main component, and H ₃ BO ₃ 0.00941 as a minor component.
Mol%, Nb ₂ O ₅ 0.00302 mol%, CaCO ₃ 0.00058
A mixture was obtained by wet mixing 100 g of powder obtained by mixing glass components consisting of mol% with the composition shown in Table 1 (Sample Nos. 1 to 3) for 2 hours in a 0.5 liter ball mill.

Separately, 100 g of powder containing only the main component (Sample Nos. 4 and 5 in Table 1) to which no subcomponents were added was wet-mixed for 2 hours with a 0.5-liter ball mill to obtain a mixture.

The mixture was dried in an air atmosphere at a temperature of 150 ° C., dried, and then calcined in an air atmosphere at a temperature of 900 ° C., and then pulverized again in a ball mill for 2 hours to give a particle size of 1.6 to 2.0.
A micron powder was obtained.

After the powder was dried at a temperature of 150 ° C. in the air atmosphere, 4 g of a polyvinyl alcohol (PVA) solution as a binder was added to 40 g of the powder and mixed, and the mixture was granulated. Toroidal core for measuring electromagnetic characteristics (outer diameter φ28.1mm, inner diameter φ2
1.1mm), and a drum-shaped core (outer diameter φ2.10mm, height 2.32) for measuring DC superposition characteristics and temperature characteristics
mm, central axis 0.93 mm, and brim thickness 0.46 mm).

The formed toroidal core and the drum-shaped core were fired in the air at the firing temperature shown in Table 1 to obtain ferrite sintered bodies having different sub-component compositions (sample numbers 1 to 5). Was produced.

Example manufactured by the above method (Sample No. 6)
.About.29) and comparative examples (sample numbers 1 to 5) of the ferrite sintered bodies, the electromagnetic characteristics (initial permeability .mu.iac,
Temperature coefficient of initial permeability αμr [ppm / ℃], saturation magnetic flux density B
s [mT]) was measured and the results are shown in Table 2. The electromagnetic characteristics (initial magnetic permeability μiac, temperature coefficient αμr [ppm / ° C.] of initial magnetic permeability, saturation magnetic flux density Bs [mT]) in Table 2 were measured under the following conditions.

The initial magnetic permeability μiac and the temperature coefficient αμr (temperature range of −40 to + 85 ° C.) of the initial magnetic permeability were measured on a sample in which a core of a toroidal shape was wound with 60 turns.

The saturation magnetic flux density Bs [mT] is 1.6 kA / m when the secondary winding is further 20 turns on the toroidal sample.
The magnetic field was measured.

The relationship between the initial magnetic permeability μiac and the saturation magnetic flux density Bs [mT] is shown in FIG. Incidentally, in FIG. 6, the number attached to the mark ◯ indicates the sample number.

Further, winding was performed for 40 turns on the drum-shaped cores of the examples and comparative examples to fabricate an inductor, and the direct current superposition characteristics of this inductor (bias current [A]
And the temperature coefficient [μH]) were measured and the results are shown in Fig. 7.
It was shown to.

Those marked with * in Tables 1 and 2 are outside the scope of the present invention, and the others are within the scope of the present invention.

[0058]

[Table 1]

[0059]

[Table 2]

As is clear from Table 2 and FIG. 6, the saturation magnetic flux density Bs (mT) of the example of the present invention is higher than the saturation magnetic flux density Bs (mT) of the comparative example by 20% or more, and in the example. Although the saturation magnetic flux density is high, the initial permeability (μi
The temperature coefficient αμr (ppm / ° C) of ac) is not high. Further, it can be seen that the initial magnetic permeability of the example is at the same level as the initial magnetic permeability of the comparative example. On the other hand, in the comparative examples (Sample Nos. 1 to 5), the saturation magnetic flux density Bs (mT) was high, and the temperature coefficient αμr (ppm / ° C) of the initial permeability (μiac) was high.
Also, the target characteristics (high Bs and low μiac) cannot be obtained.

As is clear from FIG. 7, as the performance of the inductor, even if a DC bias is applied, it is a stable core as long as the inductance is constant, and the embodiment of the present invention shows this. It can be seen that the inductance is stable. Therefore, it can be seen that the DC superposition characteristics of the example are significantly extended as compared with the comparative example.

As described above, Pb as a sub-component in the main component
O in the range of 0.00211 to 0.00528 mol% and SiO ₂
The ferrite sintered body produced by adding 0.00392 to 0.00982 mol% has the above-mentioned electromagnetic characteristics.

Further, part or all of PbO may be converted into H ₃ B.
It may be replaced with a low melting point oxide of O ₃ or Bi ₂ O ₃ . Furthermore, a part or all of SiO ₂ may be replaced with Cr ₂ O ₃ , Al
_It may be replaced by refractory oxides of ₂ O ₃ , SnO ₂ and WO ₃ .

Even if the subcomponent added to the main component was the material of the present invention, the amount of addition was outside the range of the present invention, the ferrite sintered body, Sample No. 8, Sample No. 18, and Sample No. 19 had μiac, It can be seen that the characteristics of αμr and Bs cannot be controlled as expected.

Table 3 shows the temperature characteristics of the inductance of the drum-shaped cores of the example (Sample No. 9) and the comparative example (Sample No. 2).

The measurement of the temperature characteristic of the inductance was carried out under the condition of -40 ° C to + 85 ° C in the air atmosphere.

[0067]

[Table 3]

As is clear from Table 3, the Example (Sample No. 9) is at the same level as the Comparative Example (Sample No. 2).

As described above, according to the embodiment of the present invention, by specifying the kind and the addition amount of the subcomponent added to the main component,
It is possible to manufacture a ferrite sintered body having excellent DC superposition characteristics while maintaining the temperature characteristics of the inductance.

[0070]

According to the ferrite sintered body of the present invention, since the saturation magnetic flux density is higher than that of the conventional ferrite sintered body, the allowable current can be increased if the inductors have the same shape, and the same allowable current is obtained. In that case, the shape of the inductor can be reduced, and since the temperature coefficient of the initial permeability of the inductance is small, it can be replaced with a conventional product having a low temperature coefficient.

Further, according to the method for producing a ferrite sintered body of the present invention, there is an effect that a ferrite sintered body having a high saturation magnetic flux density and a small temperature coefficient of initial permeability can be easily produced. .

[Brief description of drawings]

FIG. 1 is a characteristic curve diagram showing the relationship between inductance and allowable current,

FIG. 2 is a characteristic curve diagram showing the relationship between the amount of NiO and the saturation magnetic flux density (Bs),

FIG. 3 is a characteristic curve diagram showing the relationship between the amount of NiO and the initial magnetic permeability (μiac),

FIG. 4 is a characteristic curve diagram showing the relationship between the amount of Fe ₂ O ₃ and the saturation magnetic flux density (Bs),

FIG. 5: Saturation magnetic flux density (B
characteristic curve showing the relationship between s) and the temperature coefficient of initial permeability (αμr),

FIG. 6 is a characteristic curve diagram showing the relationship between the saturation magnetic flux density (Bs) and the temperature coefficient of initial permeability (αμr) in Examples and Comparative Examples,

FIG. 7 is a characteristic curve diagram showing a relationship between a bias current (A) and an inductance (μH) in Examples and Comparative Examples.

Claims (3)

[Claims] 1. Fe ₂ O ₃ , NiO, ZnO, CuO as a main component, and PbO, H ₃ B based on 100 mol% of this main component.
At least one kind of 0.00211 to 0.00528 mole% of O _3, or Bi ₂ O ₃ of from 0.00101 to 0.00253 mole%, and at least one of _{SiO 2, Cr 2 O 3,} Al 2 O 3, SnO 2, WO 3 Of 0.00392 to 0.00982 mol% is added to the ferrite sintered body. 2. Fe ₂ O ₃ , NiO, ZnO, and CuO, and the composition ratio of ferric oxide and divalent metal oxide is 47.
-51 mol%: 53-49 mol%, and the composition ratio of nickel ferrite and zinc ferrite is 18.7-25.5 mol%: 29.0-18.6 mol% as a main component, the main component is 100 mol %, At least one of PbO and H ₃ BO ₃ is 0.00211 to 0.00528 mol%, or Bi
0.003 to 0.00253 mol% of ₂ O ₃ , and SiO ₂ , Cr ₂
A ferrite sintered body, wherein at least one of O ₃ , Al ₂ O ₃ , SnO ₂ , and WO ₃ is added in an amount of 0.00392 to 0.00982 mol%. 3. A ferrite raw material containing Fe ₂ O ₃ , NiO, ZnO, and CuO as main components in an amount of 100 mol% and 0.0021 of at least one of PbO and H ₃ BO ₃ as auxiliary components.
1 to 0.00528 mol%, or Bi ₂ O ₃ 0.00101 to 0.00253
Mol%, and _{SiO 2, Cr 2 O 3,} Al 2 O 3, Sn
At least one of O ₂ and WO ₃ is 0.00392 to 0.00982
After adding mol%, the powder obtained by calcining and pulverizing is further finely pulverized to a fine powder having a particle size of 1.4 μm or less, and the fine powder is molded to form a molded body. A method for producing a ferrite sintered body, which comprises firing a molded body.