JP2022156993A - Ferrite composition, electronic component and power supply - Google Patents

Abstract

To provide: a ferrite composition capable of reducing the change of eddy current loss due to a difference in the size or shape of a core; an electronic component using the ferrite composition; and a power supply using the electronic component.SOLUTION: A ferrite composition has a main component and an accessory component. The main component is constituted of 51.0 to 53.5 mol% of iron oxide in terms of Fe2O3, 7 to 14 mol% of zinc oxide in terms of ZnO and the remainder consisting of manganese oxide; and the accessory component includes 0.09 to 0.27 pts.mass of cobalt in terms of CoO, 0.13 to 0.45 pts.mass of titanium in terms of TiO2, 0.06 to 0.25 pts.mass of calcium in terms of CaCO3 and 0.015 to 0.045 pts.mass of niobium in terms of Nb2O5 to 100 pts.mass of the main component.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a ferrite composition, and an electronic component and a power supply device containing the ferrite composition.

In recent years, electronic devices have become smaller and more efficient, and there is a strong demand for smaller and more efficient electronic components used in power supply devices and the like. Low-loss characteristics are required for ferrite sintered bodies used in electronic parts such as coils and transformers for miniaturization and high efficiency.

In general, the core loss Pcv of a ferrite composition consists of hysteresis loss Phv, eddy current loss Pev and residual loss Prv, and eddy current loss Pev varies greatly depending on the size or shape of the core (magnetic core). With conventional technologies, changes in eddy current loss Pev due to differences in core size or shape could not be suppressed, and when actually manufacturing ferrite cores, it was often not possible to obtain the value as designed. .

In Patent Document 1, the loss is reduced at 300 kHz-100 mT and 100° C. by adjusting the main component that reduces magnetic anisotropy and magnetostriction, adjusting the sub-component that provides sufficient electrical resistivity, and controlling the amount of unavoidable impurities. is done.

Moreover, in Patent Document 2, the loss is reduced at 120° C. or higher by adding CoO and TiO ₂ simultaneously, focusing on preventing thermal runaway of the transformer.

Furthermore, in Patent Document 3, loss reduction at 100 to 300 kHz is achieved with a composition to which CoO and TiO ₂ are added simultaneously.

However, Patent Documents 1 to 3 do not discuss changes in eddy current loss due to differences in core shape.

Japanese Patent No. 6730545 Japanese Patent No. 5786322 JP-A-2004-35372

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a ferrite composition capable of reducing changes in eddy current loss due to differences in core size or shape, and an electronic component using the ferrite composition. and to provide a power supply device using the electronic component.

In order to achieve the above object, the ferrite composition according to the present invention is
having a main component and a subcomponent,
The main component is composed of 51.0 to 53.5 mol% iron oxide in terms of Fe ₂ O ₃ , 7 to 14 mol% zinc oxide in terms of ZnO, and the balance manganese oxide,
With respect to 100 parts by mass of the main component, as the secondary components, cobalt is 0.09 to 0.27 parts by mass in terms of CoO, titanium is 0.13 to 0.45 parts by mass in terms of TiO ₂ , calcium is CaCO ₃ It contains 0.06 to 0.25 parts by mass in terms of conversion, and 0.015 to 0.045 parts by mass in terms of Nb ₂ O ₅ of niobium.

In general, product design is based on the characteristics of the core, which has a relatively small magnetic path cross-sectional area. However, actual products often have a large magnetic path cross-sectional area, and often have complex shapes and uneven magnetic path cross-sectional areas. For this reason, the characteristics at the product design stage may not match the characteristics of the actual product. In contrast, the ferrite composition according to the present invention, having the above configuration, can reduce changes in eddy current loss due to differences in core shape or size, that is, eddy current loss due to differences in core size or shape. A change in current loss can be suppressed.

The ferrite composition according to the present invention is used in various electronic parts such as inductors, transformers, choke coils, reactors, antennas, and contactless power supply coils. object, noise filter, etc.). In particular, the ferrite composition according to the present invention is preferably used as a magnetic core of a power transformer. It can be used by being incorporated in a switching power supply for a vehicle such as a hybrid vehicle, a commuter (vehicle), a power supply for household or industrial electrical equipment, or a power supply for computer equipment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

The ferrite composition according to this embodiment may be in a bulk form such as a sintered body, a powder form, or a thin film form, and the form is not particularly limited. And the ferrite composition of this embodiment has a main component and a subcomponent. The main components are iron oxide, zinc oxide and manganese oxide. On the other hand, the subcomponents include at least cobalt (Co), titanium (Ti), calcium (Ca), and niobium (Nb).

First, the composition of the main component will be explained. Assuming that the total amount of the main components is 100 mol%, the iron oxide content is in the range of 51.0 to 53.5 mol%, preferably 51.25 to 52.8 mol, in terms of Fe ₂ O ₃ . %. The standard range of zinc oxide content is 7 to 14 mol %, preferably 8.6 to 12 mol %, in terms of ZnO. In addition, the content of manganese oxide is determined as the balance of the main components by determining the content of iron oxide and zinc oxide, which are other main components.

The above main component constitutes main component particles having a spinel crystal structure in the cross section of the ferrite composition. Here, the spinel-type crystal structure is represented by the stoichiometric formula AB ₂ O ₄ , Mn and Zn enter the A site, and Fe enters the B site. In the present embodiment, the main component particles having a spinel structure preferably have an average particle diameter of 6 to 18 μm, more preferably 8 to 14 μm, in equivalent circle diameter. The average particle size of the main component particles can be measured by observing the cross section of the ferrite composition with a SEM (scanning electron microscope) or STEM (scanning transmission electron microscope) and analyzing the resulting cross-sectional photograph. .

On the other hand, the content of subcomponents is expressed as a ratio to 100 parts by mass of the main component, that is, as an outer frame amount. In the present embodiment, the content of Co is 0.09 to 0.27 parts by mass, preferably 0.13 to 0.27 parts by mass, more preferably 0.21 to 0.27 parts by mass in terms of CoO. It is 0.27 parts by mass. In addition, the content of Ti is 0.13 to 0.45 parts by mass, preferably 0.13 to 0.35 parts by mass, more preferably 0.13 to 0.45 parts by mass in terms of TiO ₂ . It is 0.225 parts by mass. In addition, the reference range for the Ca content is 0.06 to 0.25 parts by mass, more preferably 0.07 to 0.21 parts by mass in terms of CaCO ₃ . The standard range of the Nb content is 0.015 to 0.045 parts by mass in terms of Nb ₂ O ₅ .

The form in which each subcomponent exists inside the ferrite composition is not particularly limited. For example, each subcomponent may be solid-dissolved in the main component particles, or may exist as various compounds such as oxides, composite oxides, and carbonates at the grain boundaries of the main component particles.

More specifically, it is believed that Co and Ti are mainly dissolved in the main component particles, and part of the Fe in the spinel lattice is replaced by dissolved Co or Ti. In particular, it is believed that simultaneous addition of Co and Ti facilitates the substitution of Co or Ti for Fe, which is the B-site, not the A-site, of the spinel lattice. When Fe in the spinel lattice is replaced with Co or Ti, the temperature dependence of the magnetic anisotropy constant is reduced, and as a result, the temperature dependence of the magnetic loss is also reduced.

On the other hand, Ca is considered to be mainly present as a compound at the grain boundaries of the main component particles and dissolved in the vicinity of the grain boundaries of the main component particles. Presumably, the presence of Ca in the form described above improves the sinterability of the ferrite composition and increases the grain boundary resistance. In addition, Nb is considered to contribute to homogenization of the crystal structure of the ferrite composition.

Moreover, it is preferable that the ferrite composition of the present embodiment does not substantially contain Zr. In the present embodiment, “substantially free of Zr” means that the content of Zr is 0.009 parts by mass or less in terms of ZrO ₂ with respect to 100 parts by mass of the main component. The Zr content is more preferably 0 to less than 0.005 parts by mass.

In addition, the ferrite composition of the present embodiment may contain other subcomponents such as Si, V, and P and unavoidable impurities in addition to the subcomponents described above. The contents of other subcomponents and unavoidable impurities are set so as not to hinder the suppression of Pev change. For example, the total content of unavoidable impurities is preferably about 0 to 0.001 parts by mass with respect to 100 parts by mass of the main component. Moreover, it is preferable to select Si and/or V as other subcomponents. In this case, the content of Si is preferably 0.005 to 0.02 parts by mass in terms of SiO ₂ and the content of V is preferably 0.005 in terms of V ₂ O ₅ with respect to 100 parts by mass of the main component. It is preferably up to 0.04 parts by mass. Si is believed to contribute to improving the sinterability of the ferrite composition. Moreover, V is considered to exist mainly as a compound at the grain boundaries of the main component grains, and is thought to function to increase the grain boundary resistance.

The content rate of the main component and the content rate of the subcomponent as described above can be measured by component analysis using an X-ray fluorescence spectrometer (XRF). In addition, when observing a cross section with an SEM or STEM, it may be measured by component analysis using an electron probe microanalyzer (EPMA), or it may be measured using X-ray diffraction (XRD).

Next, an example of a method for producing a ferrite composition according to this embodiment will be described.

First, starting materials for the main component are prepared and weighed so as to have a predetermined composition after firing. As the starting material for the main component, an oxide powder or a compound powder that becomes an oxide when heated (carbonate powder, etc.) can be used. Specifically, α-Fe ₂ O ₃ powder, It is preferable to use _{Mn3O4 powder} and ZnO powder. Further, a composite oxide powder containing two or more kinds of metals may be used as a starting material for the main component. For example, by subjecting an aqueous solution containing iron chloride and manganese chloride to oxidative roasting, a composite oxide powder containing Fe and Mn is obtained. Then, ZnO powder may be added to and mixed with this composite oxide powder to form a raw material for the main component. The average particle size of each starting material described above is preferably 0.1 to 3.0 μm.

Next, the weighed starting materials of the main component are mixed in a mixer such as a ball mill, and then calcined. At this time, the mixing may be either wet mixing or dry mixing. When wet mixing is selected, the mixture is appropriately dried after mixing and then calcined. Further, as for the conditions of the calcination treatment, it is preferable to set the holding temperature to 800 to 1100° C., and the temperature holding time (temperature stabilization time) to be 0.5 to 5 hours. The calcined material obtained by calcining under such conditions is pulverized using various pulverizers until the average particle size reaches about 0.5 to 3.0 μm. Note that the calcination process may be omitted when a composite oxide powder containing Fe and Mn is used as the starting material of the main component.

Next, starting materials of subcomponents are added to and mixed with the raw materials after calcination. As a starting material for the subcomponent, as in the case of the main component, an oxide powder or a compound powder that becomes an oxide by heating can be used. Specifically, _CoO powder, _TiO2 powder, _CaCO3 powder, and _Nb2O5 powder can be used. The average particle size of the starting materials of the subcomponents is also preferably 0.1 to 3.0 μm. The starting materials for the subcomponents may be added after the calcination process, and then the above-described pulverization process may be performed to pulverize the calcined material while mixing the main and subcomponents. Also, the starting materials of the subcomponents may be added and mixed after the calcined material is pulverized. Further, the CoO powder and TiO ₂ powder may be mixed in advance with the starting raw materials of the main components and subjected to calcination treatment.

Next, a suitable binder such as polyvinyl alcohol is added to the mixed powder of the main component and subcomponent obtained above, and kneaded to obtain a composite material. Then, this composite material is molded into a predetermined shape by a technique such as injection molding or mechanical press molding to obtain a molded body. For example, in injection molding, a molded article is obtained by making the composite material slurry and pouring it into a mold. In mechanical press molding, a compact is obtained by filling a granular composite material into a mold and applying pressure.

Next, the compact obtained above is fired. The firing conditions are a holding temperature of 1150° C. to 1400° C., more preferably 1200° C. to 1300° C., and a temperature holding time of 1 to 10 hours, more preferably 2 to 6 hours. Further, in the temperature rising process from the start of heating to the holding temperature, the temperature rising rate is preferably 50 to 300° C./hour, and in the temperature dropping process from the holding temperature to 900° C., the cooling rate is 50 to 200° C./hour. It is preferable to The atmosphere during firing is preferably a mixed atmosphere of oxygen and nitrogen, and the partial pressure of oxygen is preferably 0.1 to 5.0 vol % during the temperature rising process and the temperature holding process. Furthermore, it is preferable to gradually decrease the oxygen partial pressure in the process of lowering the temperature from the holding temperature to 1000° C., and to set the oxygen partial pressure to 0.02 vol % or less at 1000° C. or lower.

By firing under the above conditions, a ferrite composition as a sintered body can be obtained. The ferrite composition as a sintered body according to this embodiment can be used as a magnetic core or a magnetic sheet in various electronic components.

When the ferrite composition according to the present embodiment is used as a magnetic core, the shape is E-shaped, F-shaped, I-shaped, T-shaped, U-shaped, drum-shaped, toroidal-shaped, pot-shaped, cup-shaped. It can be in the form of a mold, or simply a plate-like or prismatic shape.

The sintered body obtained after firing may be pulverized to obtain a powdery ferrite composition. In this case, a binder and a solvent can be further added to the obtained sintered body powder to form a paste. Then, the paste is formed into a sheet by a method such as a sheet method or an extrusion method, and then dried or heat-treated as appropriate to obtain a thin-film ferrite composition. Such a thin-film ferrite composition can be used, for example, as a magnetic core of a thin-film inductor, an antenna, or a magnetic sheet for non-contact power supply (for non-contact power supply, electromagnetic wave absorber, noise filter).

The core loss Pcv of the ferrite composition consists of hysteresis loss Phv, eddy current loss Pev and residual loss Prv, and the conventional eddy current loss Pev varies greatly depending on the size or shape of the core. Specifically, the eddy current loss tends to increase as the size of the core increases, and in particular, the eddy current loss tends to increase as the cross-sectional area of the magnetic path of the core increases.

On the other hand, in the ferrite composition according to the present embodiment, the content ratio of the main component and the subcomponent is within a predetermined range, so that the change in eddy current loss due to the difference in the size or shape of the core (magnetic core) is suppressed. can.

Therefore, the size and shape of the ferrite composition according to this embodiment are not particularly limited.

As described above, the ferrite composition of the present embodiment is suitable as a magnetic core material and a magnetic sheet, and can be used for electronic parts such as transformers, inductors, choke coils, reactors, antennas, and contactless power supply coils. Among the above electronic components, application as a transformer is particularly suitable. A transformer containing the ferrite composition of the present embodiment is preferably incorporated in a power supply device for use. Examples of the power supply include a switching power supply in which the above transformer is combined with an input filter, a switching circuit, a rectifying circuit, a smoothing circuit, and the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

EXAMPLES The present invention will be described in more detail below using examples and comparative examples. However, the present invention is not limited to the following examples.

In this experiment, ferrite cores of Examples 1 to 41 and Comparative Examples 1 to 20 having compositions shown in Tables 1 to 5 were produced and their eddy current loss Pev was measured. The ferrite cores of each example and each comparative example were produced by the procedure shown below.

First, α-Fe ₂ O ₃ powder, Mn ₃ O ₄ powder, and ZnO powder were prepared as starting materials for the main components, and weighed so as to have a predetermined ratio after firing. Then, the weighed powders were wet mixed in a ball mill to obtain a raw material mixture. Furthermore, after drying this raw material mixture, it was calcined at 900° C. for 3 hours in an air atmosphere to obtain a calcined material.

Next, the above calcined material was put into a ball mill filled with steel balls, and pulverized for 16 hours to obtain a pulverized powder having an average particle size of 1 to 2 μm. Then, the pulverized powder and the starting material of the subcomponent were wet-mixed and then dried to obtain a mixed powder. At this time, CoO powder, TiO ₂ powder, CaCO ₃ powder, and Nb ₂ O ₅ powder were prepared as starting materials for the subcomponents, and weighed so as to have a predetermined ratio after firing. In each example and each comparative example, a predetermined amount of SiO ₂ powder and V ₂ O ₅ powder were also added as subcomponents in addition to the above.

Next, 0.8 parts by mass of polyvinyl alcohol was added to 100 parts by mass of the mixed powder, and the mixture was sprayed with a spray dryer and dried to form granules. Then, the obtained granules were filled in two types of molds, respectively, and pressure-molded at a pressure of 100 MPa to obtain a toroidal-shaped compact.

Here, "two kinds of molds" are a mold for obtaining a "small core" of a smaller size and a mold for obtaining a "large core" of a larger size. That is, through the above steps, a "small compact" that will become a "small core" after firing and a "large compact" that will become a "large core" after firing were obtained.

Next, each of the above compacts (“small compact” and “large compact”) was fired under the following conditions. The firing conditions were a holding temperature of 1250° C., a holding time of 5 hours, and a mixed atmosphere of oxygen and nitrogen as the firing atmosphere. The oxygen partial pressure in the temperature holding process is 4 vol%, and in the temperature lowering process, the oxygen partial pressure is monotonically decreased in the temperature range of 1250 ° C. to 1000 ° C., and the oxygen partial pressure is 0 in the temperature range of 1000 ° C. or less. It was controlled to be .02 vol%. The temperature rising rate was 200° C./hour, and the cooling rate was 100° C./hour. By firing under these conditions, ferrite cores (“large core” and “small core”) were obtained as sintered bodies.

The shape of the obtained ferrite core was a toroidal shape as described above in both cases of the small core and the large core. In addition, the dimensions of the small core and the large core produced were as follows.
Small core: outer diameter: 20 mm, inner diameter: 10 mm, height: 5 mm, magnetic path cross-sectional area: 25 mm ²
Large core: outer diameter: 50 mm, inner diameter: 10 mm, height: 10 mm, magnetic path cross-sectional area: 200 mm ²

Moreover, the composition of the produced ferrite core was analyzed by XRF. Tables 1 to 5 show the measurement results.

Further, the magnetic loss Pcv at 100° C. was measured under conditions of frequencies of 200 kHz, 300 kHz and 400 kHz and a magnetic flux density of 100 mT for each small core and each large core of each example and each comparative example. The eddy current loss Pev was calculated by the following method.
As shown in Equation (1), magnetic loss Pcv at frequencies of 200 kHz to 400 kHz can be expressed as the sum of hysteresis loss Phv and eddy current loss Pev.
Pcv=Phv+Pev (1)
Next, since the hysteresis loss Phv is proportional to the frequency f, and Pev is proportional to the square of f, it can be expressed by Equation (2).
Pcv=Kh×f+Ke×f ² (2)
where Kh is the hysteresis loss factor and Ke is the eddy current loss factor.
Dividing both sides of the equation (2) by the frequency f yields the equation (3).
Pcv/f=Kh+Ke×f (3)
Since Pcv/f is a linear function of the frequency f from equation (3), the eddy current loss coefficient Ke can be obtained from the slope.
That is, the eddy current loss coefficient Ke was obtained based on the respective magnetic losses Pcv at frequencies of 200 kHz, 300 kHz and 400 kHz.
Based on the obtained eddy current loss coefficient Ke, the eddy current loss Pev was calculated by the following formula (4).
Pev=Ke×f ² (4)

Furthermore, ΔPev was calculated by the following formula (5) based on the Pev of each small core and each large core in each example and each comparative example. The results are shown in Tables 1-5. A ΔPev of 400 kW/m ³ or less was judged to be good.
ΔPev=(Pev of large core)−(Pev of small core) (5)

Table 1 mainly shows experimental results in which the content of the subcomponent was fixed and the composition of the main component was changed.

As shown in Table 1, the main components are 51.0 to 53.5 mol% iron oxide in terms of Fe ₂ O ₃ , 7 to 14 mol% zinc oxide in terms of ZnO, and the balance manganese oxide. , and containing a predetermined amount of subcomponents (Examples 1 to 9), the ΔPev is 400 kW/ ³ or less, and the ΔPev is smaller than that of Comparative Examples 1 to 4. It could be confirmed.

In Tables 2 and 3, the main components are 52.6 mol% iron oxide in terms of Fe ₂ O ₃ , 9.5 mol% zinc oxide in terms of ZnO, and the balance manganese oxide. In a certain case, the experimental results are shown when the contents of Co and Ti, which are subcomponents, are changed.

As shown in Tables 2 and 3, when 0.09 to 0.27 parts by mass of cobalt in terms of CoO and 0.13 to 0.45 parts by mass of titanium in terms of TiO ₂ are contained as subcomponents (implementation Examples 10 to 22) had a ΔPev of 400 kW/m ³ or less, and it was confirmed that the ΔPev was smaller than those of Comparative Examples 5 to 12.

In Table 4, in the case where the main component is composed of 52.2 mol% iron oxide in terms of Fe ₂ O ₃ , 11.5 mol% zinc oxide in terms of ZnO, and the balance manganese oxide , shows experimental results when the contents of Co and Ti, which are subcomponents, are changed.

As shown in Table 4, when 0.09 to 0.27 parts by mass of cobalt in terms of CoO and 0.13 to 0.45 parts by mass of titanium in terms of TiO ₂ are contained as subcomponents (Examples 23 to 29) was confirmed to have a ΔPev of 400 kW/m ³ or less.

Table 5 shows experimental results when the contents of Ca and Nb, which are subcomponents, were changed.

As shown in Table 5, when 0.06 to 0.25 parts by mass of calcium in terms of CaCO ₃ and 0.015 to 0.045 parts by mass of niobium in terms of Nb ₂ O ₅ are contained as auxiliary components (implementation Examples 30 to 41) were confirmed to have a ΔPev of 400 kW/m ³ or less.

Combining the results in Tables 1 to 5, it can be seen that the composition of the main component and the content of each of the subcomponents (Co, Ti, Ca, Nb) all satisfy the ranges serving as the criteria of the present invention, and the core It was confirmed that the change in eddy current loss due to the difference in size or shape can be suppressed. It was also confirmed that if even one of the main component and the subcomponent did not satisfy the standard range, the change in eddy current loss due to the difference in core size or shape increased.

Claims (3)

A ferrite composition having a main component and a subcomponent,
The main component is composed of 51.0 to 53.5 mol% iron oxide in terms of Fe ₂ O ₃ , 7 to 14 mol% zinc oxide in terms of ZnO, and the balance manganese oxide,
With respect to 100 parts by mass of the main component, as the secondary components, cobalt is 0.09 to 0.27 parts by mass in terms of CoO, titanium is 0.13 to 0.45 parts by mass in terms of TiO ₂ , calcium is CaCO ₃ A ferrite composition containing 0.06 to 0.25 parts by mass of niobium in an amount of 0.015 to 0.045 parts by mass of niobium in terms of Nb ₂ O ₅ . An electronic component comprising a sintered body composed of the ferrite composition according to claim 1 . A power supply device comprising the electronic component according to claim 2 .