JP2002179460A - Ferrite material and ferrite core using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ferrite material having 40 to 60 magnetic permeability, high Q value, small change rate of the inductance to be used for a high frequency band. SOLUTION: The ferrite material contains 46 to 52 mol.% Fe2O3, 28 to 36 mol.% NiO and 16 to 22 mol.% ZnO as the main components. When the average grain size of the material is represented by D, the material contains grains having 0.2D to 3D grain sizes by >=50 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite material of Ni-Zn type used in a high frequency band and a ferrite core using the same, and particularly to a ferrite used as a core material of a resin mold type chip inductor. About the material.

[0002]

2. Description of the Related Art In recent years, in the fields of televisions, personal computers, mobile communication devices, etc., with the development of higher frequencies, there is an increasing demand for higher frequency components used in these devices.

[0003] In the field of resin-molded chip inductors and fixed coils, which are rapidly increasing in demand, demands for miniaturization, weight reduction and high reliability are increasing.

[0004] In response to this requirement, the characteristics required for the ferrite core material used for these magnetic cores are as follows:
(1) low loss at high frequency, that is, high Q; (2) low magnetic permeability to obtain a wide inductance value due to winding; and (3) high permeability to suppress deterioration of characteristics due to pores. The above four characteristics are mainly mentioned: having a sintering density, (4) having a small inductance change with respect to an external stress caused by a resin to be molded, that is, having a low magnetostriction characteristic.

As such a ferrite material, for example, Japanese Patent Application Laid-Open No. 2-133509,
１９19 mol% of Fe ₂ O ₃ and 11 to 25 mol% of Zn
O and 0-10 mol% of CuO and the remainder and SiO ₂ of PbO and 0.01 to 15 parts by weight of 0.01 to 15 parts by weight Ni-Zn ferrite material consisting of NiO 0.01 to
By adding 15 parts by weight of talc, an excellent stress-resistant material having a high sintering density has been proposed.

In Japanese Patent Application Laid-Open No. H8-325056, N
Attempts have been made to obtain a ferrite material with low magnetostriction and high Q value in i-Zn ferrite material by the addition of CoO and Bi ₂ O ₃ and SiO _2.

[0007] Further, Japanese Patent Application Laid-Open No. Hei 8-51012 discloses that a Ni—Zn—Cu ferrite material is used in an amount of 0.1%. ~
0.5 parts by weight of Co ₃ O ₄ and 0 to 10 parts by weight of Bi ₂ O ₃
When the addition of SiO ₂ of 0 parts by weight is proposed.

[0008]

Problems to be Solved by the Invention
The ferrite material disclosed in Japanese Patent Publication No. 9 has a problem that the magnetic permeability is too low and PbO which is not considered to be environmentally friendly is used. Further, the Ni-Zn ferrite material disclosed in JP-A-8-325056 has a problem that the magnetostriction is large and the Q value is low.

Further, the ferrite material disclosed in Japanese Patent Application Laid-Open No. 8-51012 has a problem that the magnetic permeability is as small as 15 or less and the magnetostriction is large. Furthermore, in these conventional techniques, even if the inductance is adjusted to a predetermined value as an element, when the resin is actually molded, a compressive stress due to shrinkage of the resin is applied when the resin is cured or when the resin is cooled from the curing temperature to room temperature. In addition, there is a problem that the inductance of the ferrite core is reduced due to the compressive stress, and a circuit using the inductor element using these ferrite materials has low reliability.

If the rate of decrease in inductance is always constant, adjustment can be made in advance. However, the rate of decrease in inductance varies because the pressure during resin molding varies. Therefore, a low magnetostrictive material that is a material having a small inductance reduction ratio with respect to a compressive stress is desired. In particular, 1
High Q value and high magnetic permeability of 40 MHz or higher
This requirement was significant for materials having ６０60. Accordingly, an object of the present invention is to provide a ferrite core having a high Q value at a magnetic permeability of 40 to 60, a high sintering density, and low magnetostriction characteristics.

[0011]

The ferrite material of the present invention contains, as main components, oxides of Fe, Ni and Zn in an amount of 46 to 52 mol% in terms of Fe ₂ O ₃ and 2 in terms of NiO, respectively.
It is characterized by containing 8 to 36 mol% and 16 to 22 mol% in terms of ZnO, and when the average crystal grain size is D, the crystals having a grain size of 0.2 D to 3 D are 50 vol% or more.

Further, based on 100 parts by weight of the main component,
Co, Bi and Si are 0.05 to 0.30 in terms of CoO.
Parts, 4-8 parts by weight of Bi in terms of Bi ₂ O _3, characterized in that it contains 1.0 to 4.0 parts by weight of Si in terms of SiO _2.

Further, Cu and Mn are each replaced by CuO
It is characterized by containing 0.4 parts by weight or less in conversion and 0.45 parts by weight or less in MnO conversion.

The ferrite material has a magnetic permeability of 40 to 60 and a density of 5.1 g / cm ³ or more and 10 K to 10 K.
The rate of change of inductance under compressive stress of gf is ±
It is characterized by being within 5%.

Further, the ferrite core is formed into a predetermined shape with the ferrite material.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below.

The ferrite material of the present invention means a sintered body obtained by molding and firing a green body.
In order to have a high Q value, a high density, a magnetic permeability of 40 to 60, and a low rate of change of inductance, it is important that the material is a ferrite material shown below.

That is, oxides of Fe, Ni and Zn are used as main components in an amount of 46 to 52 m in terms of Fe ₂ O ₃ , respectively.
ol%, 28 to 36 mol% in terms of NiO, 16 to 22 mol% in terms of ZnO, and when the average crystal grain size is D, a ferrite material in which crystals having a grain size of 0.2 D to 3 D are 50 vol% or more. It is important that Fe to Fe
_The reason why 46 to 52 mol% is calculated in terms of ₂ O ₃ is that 46 mo
If it is less than 1%, the magnetic permeability becomes smaller than 40, and
If the amount is more than mol%, sintering is poor and the density is reduced, and the Q value is reduced.

The reason why Ni is set to 28 to 36 mol% in terms of NiO is that if less than 28 mol%, the Q value decreases, and
This is because if it exceeds 6 mol%, the magnetostriction characteristics increase and the rate of change in inductance increases.

The reason why Zn is set to 16 to 22 mol% in terms of ZnO is that when Zn is less than 16 mol% in terms of ZnO, the magnetic permeability becomes smaller than 40, and when it exceeds 22 mol%, the Q value decreases.

When the average crystal grain size is D, 0.2D to 3D
The reason why the crystal having a particle diameter of D is 50% by volume or more is that if it is less than 50% by volume, the Q value decreases, which is not preferable. In order to increase the Q value, it is more preferable that the crystals having a particle size of 0.2D to 3D be 75% by volume or more.

Further, in the ferrite material of the present invention,
It is preferable that the average crystal grain size D is 0.8 to 8 μm. This is because the Q value is not significantly improved when the average crystal grain size D is out of the range of 0.8 to 8 μm.

The average crystal grain size D of the ferrite material of the present invention and the volume% of the crystal having a size of 0.2D to 3D are measured by using an SEM photograph of the sintered body.

In the ferrite material of the present invention, Co, Bi and Si are added to 100 parts by weight of the main component.
0.05 to 0.30 parts by weight in terms of O, Bi is Bi ₂ O ₃
4-8 parts by weight in terms of, 1.0 to Si in terms of SiO ₂
It is preferred to contain 4.0 parts by weight.

Co is C with respect to 100 parts by weight of the main component.
The content of 0.05 to 0.30 parts by weight in terms of oO is
If the amount is less than 0.05 parts by weight, the Q value is not significantly improved,
If the amount is more than 0.3 parts by weight, the magnetic permeability tends to be low within the range of 40 to 60.

Further, B is added to 100 parts by weight of the main component.
i The Bi ₂ O ₃ less and no remarkable improvement in the density of from 4 parts by weight to contain 4-8 parts by weight in terms of, or not as remarkable improvement of the density is more than 8 parts by weight, the permeability is 40
This is because the value tends to be high within the range of 60.

Further, S was added to 100 parts by weight of the main component.
When i is contained in an amount of 1.0 to 4.0 parts by weight in terms of SiO ₂ , the effect of reducing the inductance change rate is not significant when the amount is less than 1.0 part by weight, and when the amount is more than 4 parts by weight, the magnetic permeability is 40 to 40 parts by weight. This is because the value tends to be low within the range of 60.

The ferrite material of the present invention preferably contains Cu and Mn in an amount of 0.4 parts by weight or less in terms of CuO and 0.45 parts by weight or less in terms of MnO _{2 based on} 100 parts by weight of the main component. .

Each of Cu and Mn is 0.4 in terms of CuO.
The reason why the content is not more than 0.4 parts by weight in terms of MnO ₂ is that when the content of Cu and Mn is out of this range, the magnetic permeability tends to be low in the range of 40 to 60.

The ferrite material of the present invention has a magnetic permeability of 40 to 60, a density of 5.1 g / cm ³ or more, and 9
It is preferable that the rate of change of inductance under a compressive stress of 8 MPa is within ± 5%. If the ferrite material is used as a chip inductor or coil outside these ranges, the reliability of these products will not be sufficiently high. ± 3% change in inductance
It is particularly preferable that it is within the range.

The ferrite core of the present invention is characterized in that the ferrite core is formed into a predetermined shape by using the ferrite material.

Here, the ferrite core may be a ring-shaped toroidal core or a bobbin-shaped core, and a coil can be formed by winding each of them.

The method for producing the ferrite material of the present invention is, for example, as follows. That is, the main composition is Fe
₂ O ₃ , NiO, and ZnO were prepared by mixing the respective raw materials so as to be in the above-described composition range, and pulverized and mixed with a ball mill or the like.
It is calcined in the range of 0 to 1000 ° C. so that the average particle size after calcining is 0.5 to 1 μm and the specific surface area is 3 to 4 m ² / g.

Next, CoO, Bi ₂ O was added to the obtained calcined powder.
_3. SiO ₂ , CuO, MnO are added so as to be in the composition range described above, and pulverized and mixed by a ball mill or the like to obtain a powder A having a controlled particle size distribution.

The particle size distribution of the obtained powder A is such that the average particle size is 0.5 to 0.7 μm.

The ferrite material of the present invention can be obtained by granulating the obtained powder A by a known method, shaping it into a predetermined shape, and firing at 900 to 1300 ° C.
In the ferrite material of the present invention, when the average grain size is D, the average grain size after calcination is 0.5 to 1 μm in order to make the crystals having a grain size of 0.2D to 3D to be 50% by volume or more. The particle size of the raw material and the calcination temperature conditions are controlled so that the specific surface area becomes 3 to 4 m ² / g, and the calcined powder is further added to the calcination powder in the range of 0.5 to 0.7.
It is important to mill to an average particle size of μm. By using this manufacturing method, it is possible to control the magnetic permeability to 40 to 60 and obtain a ferrite material having a high Q value and a small inductance change rate.

The ferrite material of the present invention is used for a signal chip inductor, and particularly has a high Q at a high frequency.
It can be suitably used for a component requiring a value or a component for which an inductance change rate is to be suppressed, such as a resin mold type chip inductor.

The present invention can be used not only for the ferrite core but also for various uses.

For example, as a ferrite substrate for mounting various electronic components, dividing the electronic components, an electromagnetic wave absorbing member for absorbing electromagnetic waves to shield a magnetic head or the like, and generating heat. Can be used.

It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0041]

EXAMPLE 1 Each raw material was prepared by mixing Fe ₂ O ₃ , NiO, and ZnO so as to be in the composition range shown in Table 1, and pulverized and mixed with a ball mill or the like.
After calcination in the range of 0 to 1000 ° C, the particle size after calcination is 0.5.
~1.0μm, specific surface area was set to become 3~4m ² / g.

Next, the obtained calcined powder was pulverized and mixed with a ball mill or the like to obtain powder A having an average particle size of 0.5 to 0.7 μm.
I got

A predetermined binder was added to the obtained powder A, and the mixture was granulated. The shape of the toroidal core (a sample for evaluating the magnetic permeability μ and Q value) and the shape of a 3 × 3 × 15 square rod (magnetostriction) were measured in a compression molding machine. A sample for property evaluation) and a columnar shape (sample for evaluation of sintered density) were formed, and these formed bodies were fired in a range of 900 to 1300 ° C. to obtain a ferrite core. Note that a coated copper wire having a wire diameter of 0.2 mm was wound around the ferrite core seven times, and the respective characteristics were measured.

The permeability μ at 100 KHz and the rate of change ΔL / L of the inductance under a compressive stress of 98 MPa, which is the magnetostrictive characteristic, were measured at 1 MHz using the LCR meter.

B. Sintering density D was evaluated according to the Archimedes' method.

Further, the average crystal grain size D of the obtained sintered body and the volume% of the crystals having a size of 0.2D to 3D were measured using the SEM photograph of the sintered body as follows.

The inside section of the sintered body was polished and mirror-finished. The mirror-finished sample was subjected to a heat treatment at, for example, 1100 ° C. for 15 minutes by a thermal etching method so that the crystal shape could be observed in an SEM image. After the heat treatment, an acceleration voltage of 15 kV and a probe current of 5 × 10 ^{−10 were} measured for each sample using a wavelength-dispersive X-ray microanalyzer.
A photograph of the backscattered electron image was taken at about A and at a magnification of about 300 to 3000 times. From the photographs thus obtained, the particle size was measured by an image analysis method. In this image analysis method, the particle size Hd is
Assuming that A is the area inside the particle, it was determined from Hd = 2 (A / π) ^1/2 .

The results are as shown in Table 1.

From these results, it is found that the samples within the range of the present invention have a Q value of 140 or more when the magnetic permeability is in the range of 40 to 60, an inductance change rate ΔL / L of 5% or less, and a sintered density B.C. D
Was 5.15 g / cm ³ or more, and excellent characteristics were obtained.

On the other hand, in a sample outside the scope of the present invention,
If the permeability μ is out of the range of 40-60, or if the inductor
Or the sintering density is 5.1 g /
cm ^ThreeOr less.

[0051]

[Table 1]

Example 2 Next, the main component was fixed to 49 mol% of Fe ₂ O ₃ , 32 mol% of NiO and 19 mol% of ZnO,
O also changed in several ways as shown in Table 2 in the range of 0.03 to 0.35 parts by weight of Bi ₂ O ₃ 3-9 parts by weight of SiO ₂ of 0.5 to 5 parts by weight, other A sample having a toroidal core shape, a square rod shape and a cylindrical shape was obtained under the same conditions as in Example 1 above.

For the obtained sintered body, in the same manner as in Example 1, the magnetic permeability, the Q value, the inductance change rate due to the magnetostrictive characteristics, the sintered density, the average crystal grain size D of the sintered body and 0.2
When the volume% of the crystals of D to 3D was measured, the results shown in Table 2 were obtained.

From these results, it was found that the amount of CoO added was 0.05
0.3 amount of 4-8 parts by weight of parts by weight Bi ₂ O ₃ and S
The sample of the present invention in which iO _{2 was} contained in an amount of 1 to 4 parts by weight had a magnetic permeability μ of 40 to 60, a Q value of 160 or more, an inductance change rate ΔL / L of 3% or less, and a sintered density of 5.1 g / cm ³ or more and even better results were obtained.

[0055]

[Table 2]

Example 3 Next, the main components were fixed to 49 mol% of Fe ₂ O ₃ , 32 mol% of NiO and 19 mol% of ZnO, and 0.15 parts by weight of CoO and 6 parts by weight of Bi ₂ O 0.4 parts by weight or less of Cu to a composition containing ₃ and 2 parts by weight of SiO ₂
O and MnO of 0.45 parts by weight or less were varied in various ways as shown in Table 3, and other conditions were the same as in Example 1 to obtain a sample having a toroidal shape, a square rod shape and a cylindrical shape.

With respect to the obtained sintered body, in the same manner as in Example 1, the magnetic permeability, the Q value, the magnetostriction characteristics, the sintering density, the average crystal grain size D of the sintered body, and the crystal having a size of 0.2D to 3D Was evaluated, and the results shown in Table 3 were obtained.

From these results, the samples within the scope of the present invention were transparent.
Magnetic susceptibility μ is 40-60, Q value is 160 or more, inductance
Rate of change ΔL / L is 3% or less, and the sintered density is 5.2 g /
cm ^ThreeAs described above, more favorable results were obtained.

[0059]

[Table 3]

Example 4 Next, the main components were fixed to 49 mol% of Fe ₂ O ₃ , 32 mol% of NiO and 19 mol% of ZnO, and 0.15 parts by weight of CoO and 6 parts by weight of Bi ₂ O as subcomponents The composition of ₃ and 2 parts by weight of SiO ₂ , 0.3 parts by weight of CuO and 0.40 parts by weight of MnO is fixed, and the volume% of 0.3D to 3D crystals is determined as the particle size of the powder after calcination. , The specific surface area, and the ground particle size after calcination were controlled and changed, and a sample having a toroidal shape, a square rod shape, and a cylindrical shape was obtained in the same manner as in Example 1 above.

For the obtained sintered body, in the same manner as in Example 1, the magnetic permeability, Q value, magnetostriction characteristics, sintering density, average crystal grain size D of the sintered body, and crystals having a size of 0.2D to 3D were obtained. When the% by volume was evaluated, the results shown in Table 4 were obtained.

As shown in Table 4, the samples within the range of the present invention had a magnetic permeability μ of 40 to 60, a Q value of 160 or more, a change rate of inductance ΔL / L of 3% or less, and a sintered density of 5% or less. .
Even better results were obtained with 2 g / cm ³ or more.

[0063]

[Table 4]

[0064]

According to the present invention, when each of the oxides of Fe, Ni and Zn is contained in a specific range and the average crystal grain size is D, the crystals having a grain size of 0.2D to 3D are more than 50% by volume. By doing so, it is possible to obtain a ferrite material having a high Q value, a high density, and excellent magnetostriction characteristics in the range of magnetic permeability of 40 to 60.

Therefore, if a ferrite core is formed from the ferrite material of the present invention, a ferrite core with low magnetostriction can be obtained.

As a result, it is possible to suppress a change in characteristics with respect to a pressure caused by resin sealing or the like.
Since high reliability can be obtained, it can be widely used for resin-sealed chip inductors and other electronic components.

Claims (6)

[Claims] An oxide of Fe, Ni and Zn as main components is 46 to 52 mol% in terms of Fe ₂ O ₃ , respectively.
28-36 mol% in conversion, 16-22 m in ZnO conversion
ol%, and when the average grain size is D, 0.2D ~
A ferrite material, wherein a crystal having a 3D particle size is 50% by volume or more. 2. Co, based on 100 parts by weight of the main component,
0.05-0.30 parts by weight of Bi and Si in terms of CoO, 4.0 to 8.0 parts by weight of Bi in terms of Bi ₂ O _3, Si
_2. The ferrite material according to claim 1, wherein the ferrite material contains 1.0 to 4.0 parts by weight in terms of SiO2. 3. The method according to claim 1, wherein the main component is 100 parts by weight of Cu, M
The ferrite material according to claim 1, wherein n is 0.4 parts by weight or less in terms of CuO and 0.45 parts by weight or less in terms of MnO. 4. The ferrite material according to claim 1, wherein said average particle diameter D is 0.8 to 8 μm. 5. A magnetic permeability of 40 to 60 and a density of 5.1 g / c.
m ³ or more, the ferrite material according to claim 1 Inductance change under compressive stress of 98MPa is equal to or is within 5% ±. 6. A ferrite core formed into a predetermined shape with the ferrite material according to claim 1.