Ferrite composition, electronic component and power supply

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 accessory components. The main component is constituted by 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. Relative to 100 pts.mass of the main component, the accessory components include 0.09 to 0.27 pt.mass of cobalt in terms of CoO, 0.13 to 0.225 pt.mass of titanium in terms of TiO2, 0.06 to 0.25 pt.mass of calcium in terms of CaCO3, and 0.015 to 0.045 pt.mass of niobium in terms of Nb2O5.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a ferrite composition, an electronic component including the ferrite composition, and a power supply device.

Background Art

[0002] In recent years, miniaturization and high efficiency of electronic devices have progressed, and miniaturization and high efficiency are strongly required also for electronic components used in power supply devices and the like. For ferrite sintered bodies used in electronic components such as coils and transformers for miniaturization and high efficiency, low loss characteristics are required.

[0003] Generally, the core loss Pcv of a ferrite composition consists of a hysteresis loss Phv, an eddy current loss Pev, and a residual loss Prv, and the eddy current loss Pev varies greatly depending on the size or shape of the core (magnetic core). In the conventional techniques, the change in the eddy current loss Pev due to the difference in the size or shape of the core cannot be suppressed, and when actually manufacturing a ferrite core, it was often impossible to obtain the designed value.

[0004] In Patent Document 1, by adjusting the main components with reduced magnetic anisotropy and magnetostriction, adjusting the sub-components with sufficient electrical resistivity, and controlling the amount of inevitable impurities, low loss at 300 kHz - 100 mT, 100 °C has been achieved.

[0005] Also, in Patent Document 2, with the main focus on preventing thermal runaway of a transformer, by adding CoO and TiO 2 simultaneously, loss reduction at 120 °C or higher has been achieved.

[0006] Furthermore, in Patent Document 3, loss reduction at 100 - 300 kHz has been achieved with a composition obtained by simultaneously adding CoO and TiO 2 However, in Patent Documents 1 to 3, the change in the eddy current loss due to the difference in the core shape has not been examined.

[0007]

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] In view of such circumstances, the present invention has been made, and its object is to provide a ferrite composition capable of reducing the change in eddy current loss due to differences in the size or shape of the core, an electronic component using the ferrite composition, and a power supply device using the electronic component.

Means for Solving the Problems

[0010] To achieve the above object, the ferrite composition according to the present invention has a main component and a sub - component, the main component is composed of iron oxide in an amount of 51.0 to 53.5 mol% in terms of Fe 2 O 3 conversion, zinc oxide in an amount of 7 to 14 mol% in terms of ZnO conversion, and manganese oxide as the balance, with respect to 100 parts by mass of the main component, as the sub - component, cobalt in an amount of 0.09 to 0.27 parts by mass in terms of CoO conversion, titanium in an amount of 0.13 to 0.45 parts by mass in terms of TiO 2 conversion, calcium in an amount of 0.06 to 0.25 parts by mass in terms of CaCO 3 conversion, and niobium in an amount of 0.015 to 0.045 parts by mass in terms of Nb 2 O 5 conversion are contained.

[0011] Generally, product design is carried out based on the characteristics of a core with a relatively small magnetic path cross-sectional area. However, in actual products, the magnetic path cross-sectional area is often large, and the shape is complex and the magnetic path cross-sectional area is often not uniform. For this reason, the characteristics in the product design stage may not match the characteristics of the actual product. On the other hand, the ferrite composition according to the present invention has the above configuration, so that it is possible to reduce the change in eddy current loss due to the difference in the shape or size of the core, that is, it is possible to suppress the change in eddy current loss due to the difference in the size or shape of the core.

[0012] The ferrite composition according to the present invention can be used as a magnetic core or a magnetic sheet (for non-contact power supply, electromagnetic wave absorber, noise filter, etc.) included in various electronic components such as inductors, transformers, choke coils, reactors, antennas, and non-contact power supply coils. In particular, the ferrite composition according to the present invention is preferably used as a magnetic core of a power transformer, and this power transformer can be incorporated and used, for example, in an in-vehicle switching power supply device used in an EV (Electric Vehicle), a PHV (Plug-in Hybrid Vehicle), or a commuter (vehicle), a power supply device for household or industrial electrical equipment, or a power supply device for computer equipment.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail.

[0014] The ferrite composition according to the present embodiment may be in a bulk form such as a sintered body, a powder form, or a thin film form, and its form is not particularly limited. And the ferrite composition of the present embodiment has a main component and a sub-component. The main component is composed of iron oxide, zinc oxide, and manganese oxide. On the other hand, as the sub-component, at least cobalt (Co), titanium (Ti), calcium (Ca), and niobium (Nb) are included.

[0015] First, the composition of the main components will be described. Assuming the total amount of the main components is 100 mol%, the content of iron oxide ranges from 51.0 to 53.5 mol% in terms of Fe 2 O 3 , preferably 51.25 to 52.8 mol%. The content of zinc oxide ranges from 7 to 14 mol% in terms of ZnO, preferably 8.6 to 12 mol%. Also, the content of manganese oxide is determined as the remainder among the main components by determining the contents of iron oxide and zinc oxide, which are the other main components.

[0016] The above-mentioned main components constitute main component particles having a spinel-type crystal structure in the cross-section of the ferrite composition. Here, the spinel-type crystal structure is represented by the stoichiometric composition formula AB 2 O 4 , where Mn and Zn enter the A site and Fe enters the B site. In the present embodiment, the main component particles of the spinel structure preferably have an average particle diameter in terms of the equivalent circle diameter of 6 to 18 μm, more preferably 8 to 14 μm. The average particle diameter of the main component particles can be measured by observing the cross-section of the ferrite composition with an SEM (scanning electron microscope) or STEM (scanning transmission electron microscope) and performing image analysis on the obtained cross-sectional photograph.

[0017] On the other hand, the content of the sub-components is expressed as the ratio to 100 parts by mass of the above-mentioned main components, that is, as the outer frame amount. In the present embodiment, the content of Co ranges from 0.09 to 0.27 parts by mass in terms of CoO, preferably 0.13 to 0.27 parts by mass, more preferably 0.21 to 0.27 parts by mass. Also, the content of Ti ranges from 0.13 to 0.45 parts by mass in terms of TiO 2 , preferably 0.13 to 0.35 parts by mass, more preferably 0.13 to 0.225 parts by mass. Also, the content of Ca ranges from 0.06 to 0.25 parts by mass in terms of CaCO 3 , more preferably 0.07 to 0.21 parts by mass. Also, the content of Nb ranges from Nb 2 O 5It is 0.015 to 0.045 parts by mass in terms of conversion.

[0018] The existence form of each sub-component inside the ferrite composition is not particularly limited. For example, each sub-component may be dissolved in the main component particles, or may exist as various compounds such as oxides, complex oxides, carbonates, etc. at the grain boundaries of the main component particles.

[0019] More specifically, Co and Ti are mainly dissolved in the main component particles, and it is considered that a part of Fe in the spinel lattice is replaced by the dissolved Co or Ti. In particular, by adding Co and Ti simultaneously, it is considered that Fe at the B-site rather than the A-site of the spinel lattice is more easily replaced by Co or Ti. When Fe in the spinel lattice is replaced by Co or Ti, the temperature dependence of the magnetic anisotropy constant becomes smaller, and as a result, the temperature dependence of the magnetic loss also becomes smaller.

[0020] On the other hand, Ca is mainly considered to exist as a compound at the grain boundaries of the main component particles and to be dissolved near the grain boundaries of the main component particles. The existence of Ca in the above form is considered to improve the sinterability of the ferrite composition and increase the grain boundary resistance. Also, Nb is considered to contribute to the homogenization of the crystal structure of the ferrite composition.

[0021] Also, it is preferable that the ferrite composition of this embodiment does not substantially contain Zr. In this embodiment, "not substantially containing Zr" means that the content rate of Zr is 0.009 parts by mass or less in terms of ZrO 2 in terms of conversion with respect to 100 parts by mass of the main component. The content rate of Zr is more preferably 0 to less than 0.005 parts by mass.

[0022] In addition, the ferrite composition of the present embodiment may contain other sub-components such as Si, V, P and inevitable impurities in addition to the above-described sub-components. The content of other sub-components and inevitable impurities shall be an amount that does not prevent the suppression of Pev change. For example, the total content of inevitable impurities is preferably about 0 to 0.001 parts by mass with respect to 100 parts by mass of the main component. Further, as other sub-components, it is preferable to select Si or / and V. In this case, with respect to 100 parts by mass of the main component, 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 to 0.04 parts by mass in terms of V 2 O 5 It is considered that Si contributes to the improvement of the sinterability of the ferrite composition. Further, V is considered to mainly exist as a compound at the grain boundaries of the main component particles and is considered to function to increase the grain boundary resistance.

[0023] The content of the main component and the content of the sub-component as described above can be measured by component analysis using a fluorescent X-ray analyzer (XRF). Further, at the time of cross-sectional observation by SEM or STEM, it may be measured by component analysis using an electron beam microanalyzer (EPMA), or it can also be measured using X-ray diffraction (XRD).

[0024] Next, an example of a method for manufacturing the ferrite composition according to the present embodiment will be described.

[0025] First, starting materials for the main component are prepared and weighed so as to have a predetermined composition after firing. As the starting materials for the main component, oxide powders or powders of compounds that become oxides by heating (such as carbonate powders) can be used. Specifically, α-Fe 2 O 3 powder, Mn 3 O 4It is preferable to use powder and ZnO powder. Also, a powder of a composite oxide containing two or more metals may be used as the starting material of the main component. For example, by subjecting an aqueous solution containing iron chloride and manganese chloride to oxidative roasting, a powder of a composite oxide containing Fe and Mn is obtained. Then, by adding and mixing ZnO powder to this powder of the composite oxide, it may be used as the starting material of the main component. Note that the average particle size of each of the above-described starting materials is preferably 0.1 to 3.0 μm.

[0026] Next, the weighed starting material of the main component is mixed with 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, after appropriate drying after mixing, it is calcined. Also, the conditions for the calcination treatment are preferably such that the holding temperature is 800 to 1100 °C, and the temperature holding time (temperature stabilization time) is preferably 0.5 to 5 hours. For the calcined material obtained by calcining under such conditions, it is pulverized using various pulverizers until the average particle size becomes about 0.5 to 3.0 μm. Note that when using a powder of a composite oxide containing Fe and Mn as the starting material of the main component, the calcination treatment may be omitted.

[0027] Next, the starting material of the sub-component is added to and mixed with the raw material after calcination. As the starting material of the sub-component, similar to the case of the main component, a powder of an oxide or a powder of a compound that becomes an oxide by heating can be used. Specifically, CoO powder, TiO 2 powder, CaCO 3 powder, Nb 2 O 5 powder can be used. Regarding the average particle size of the starting material of the sub-component as well, it is preferably 0.1 to 3.0 μm. Note that the starting material of the sub-component may be added after the calcination treatment, and then the above-described pulverization treatment may be performed to pulverize the calcined material while mixing the main component and the sub-component. Also, the starting material of the sub-component may be added after pulverization of the calcined material and mixed. Furthermore, CoO powder and TiO 2 powder may be mixed with the starting material of the main component in advance and subjected to the calcination treatment.

[0028] Next, an appropriate binder (such as polyvinyl alcohol) is added to the mixed powder of the main component and the sub-component obtained above and kneaded to obtain a composite material. Then, this composite material is formed into a predetermined shape by a method such as injection molding or mechanical press molding to obtain a molded body. For example, in injection molding, the above composite material is slurried and poured into a mold to obtain a molded body. In mechanical press molding, a granular composite material is filled into a mold and pressurized to obtain a molded body.

[0029] Next, the molded body obtained above is fired. The firing conditions are such that the holding temperature is 1150°C to 1400°C, more preferably 1200°C to 1300°C, and the temperature holding time is 1 to 10 hours, more preferably 2 to 6 hours. Also, in the temperature rising process from the start of heating to the holding temperature, it is preferable that the temperature rising rate is 50 to 300°C / hour, and in the temperature dropping process from the holding temperature to 900°C, it is preferable that the cooling rate is 50 to 200°C / hour. Further, the atmosphere during firing is a mixed atmosphere of oxygen and nitrogen, and it is preferable that the oxygen partial pressure in the temperature rising process and the temperature holding process is 0.1 to 5.0 vol%. Furthermore, in the temperature dropping process from the holding temperature to 1000°C, the oxygen partial pressure is gradually decreased, and below 1000°C, it is preferable that the oxygen partial pressure is 0.02 vol% or less.

[0030] By firing under the above conditions, a ferrite composition as a sintered body is obtained. The ferrite composition as the sintered body according to the present embodiment can be used as a magnetic core or a magnetic sheet in various electronic components.

[0031] When the ferrite composition according to the present embodiment is used as a magnetic core, the shape can be an E-shape, an F-shape, an I-shape, a T-shape, a U-shape, a drum shape, a toroidal shape, a pot shape, a cup shape, or simply a plate shape or a prismatic shape.

[0032] Note that 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, this paste is formed into a sheet by a method such as a sheet method or an extrusion method, and thereafter, a thin-film ferrite composition can be obtained by appropriately performing drying and heat treatment. Such a thin-film ferrite composition can be used, for example, as a core of a thin-film inductor or as a magnetic sheet (for non-contact power feeding, electromagnetic wave absorber, noise filter) for antennas and non-contact power feeding.

[0033] The core loss Pcv of the ferrite composition consists of a hysteresis loss Phv, an eddy current loss Pev, and a residual loss Prv. The conventional eddy current loss Pev varies greatly depending on the size or shape of the core. Specifically, as the size of the core increases, the eddy current loss tends to increase, and particularly as the magnetic path cross-sectional area of the core increases, the eddy current loss tends to increase.

[0034] On the other hand, in the ferrite composition according to the present embodiment, since the content ratios of the main component and the sub-component are within a predetermined range, the change in the eddy current loss due to the difference in the size or shape of the core (magnetic core) can be suppressed.

[0035] Therefore, the size and shape of the ferrite composition according to the present embodiment are not particularly limited.

[0036] As described above, the ferrite composition of the present embodiment is suitable as a core material or a magnetic sheet, and can be used in electronic components such as transformers, inductors, choke coils, reactors, antennas, and non-contact power feeding coils. Among the above electronic components, application as a transformer is particularly suitable. The transformer including the ferrite composition of the present embodiment is particularly preferably used by being incorporated into a power supply device. Examples of the power supply device include a switching power supply device in which the above transformer is combined with an input filter, a switching circuit, a rectifying circuit, a smoothing circuit, and the like.

[0037] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to the above-described embodiments and can be variously modified within the scope of the present invention.

Example

[0038] Hereinafter, the present invention will be explained in more detail using examples and comparative examples. However, the present invention is not limited to the following examples.

[0039] In this experiment, ferrite cores of Examples 1 to 41 and Comparative Examples 1 to 20 having the compositions shown in Tables 1 to 5 were prepared, and their eddy current losses Pev were measured. The ferrite cores of each example and each comparative example were produced by the following procedure.

[0040] First, as starting materials for the main components, α-Fe 2 O 3 powder, Mn 3 O 4 powder, and ZnO powder were prepared and weighed so as to have a predetermined ratio after firing. Then, each of the weighed powders was wet-mixed with a ball mill to obtain a raw material mixture. Further, after drying this raw material mixture, it was calcined at 900°C for 3 hours in an air atmosphere to obtain a calcined material.

[0041] 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, this pulverized powder and the starting materials for the sub-components were wet-mixed and then dried to obtain a mixed powder. At this time, as starting materials for the sub-components, CoO powder, TiO 2 powder, CaCO 3 powder, Nb 2 O 5 powder were prepared and weighed so as to have a predetermined ratio after firing. Also, in each example and each comparative example, SiO 2 powder and V 2 O 5 powder were also added in a predetermined amount as sub-components other than the above.

[0042] Next, 0.8 parts by mass of polyvinyl alcohol was added to 100 parts by mass of the above mixed powder, and this was sprayed and dried with a spray dryer to form granules. Then, the obtained granules were filled into two types of molds respectively, and a toroidal shaped molded body was obtained by pressure molding at a pressure of 100 MPa.

[0043] Here, the "two types of molds" are a mold for obtaining a "small core" with a smaller size and a mold for obtaining a "large core" with a larger size. That is, by the above process, a "small molded body" that becomes a "small core" after firing and a "large molded body" that becomes a "large core" after firing were obtained.

[0044] Next, each of the above molded bodies ("small molded body" and "large molded body") was fired under the following conditions. The firing conditions were a holding temperature of 1250 °C, a holding time of 5 hours, and a firing atmosphere of a mixed atmosphere of oxygen and nitrogen. The oxygen partial pressure during the temperature holding process was 4 vol%, and in the temperature decreasing process, the oxygen partial pressure was monotonically decreased in the temperature range of 1250 °C to 1000 °C, and was controlled so that the oxygen partial pressure became 0.02 vol% in the temperature range of 1000 °C or lower. Also, the heating rate was 200 °C / hour and the cooling rate was 100 °C / hour. By firing under such conditions, ferrite cores ("large core" and "small core") as sintered bodies were obtained.

[0045] Note that the shape of the obtained ferrite cores was toroidal in both the case of the small core and the large core as described above. Also, the dimensions of the produced small core and large core 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

[0046] Also, for the produced ferrite cores, their compositions were analyzed by XRF. The measurement results are shown in Tables 1 to 5.

[0047] Also, for each small core and each large core of each example and each comparative example, the magnetic loss Pcv at 100 °C was measured under the conditions of a frequency of 200 kHz, 300 kHz, 400 kHz, and a magnetic flux density of 100 mT. The eddy current loss Pev was calculated by the following method. As shown in Equation (1), the magnetic loss Pcv at frequencies from 200 kHz to 400 kHz can be expressed as the sum of the hysteresis loss Phv and the 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 as in Equation (2). Pcv = Kh×f + Ke×f 2 ···(2) Here, Kh is the hysteresis loss coefficient and Ke is the eddy current loss coefficient. Dividing both sides of Equation (2) by the frequency f gives the expression in Equation (3). Pcv / f = Kh + Ke×f ···(3) From Equation (3), since Pcv / f is a linear function of the frequency f, the eddy current loss coefficient Ke can be obtained from the slope. That is, based on the magnetic losses Pcv at frequencies of 200 kHz, 300 kHz, and 400 kHz respectively, the eddy current loss coefficient Ke was obtained. Based on the obtained eddy current loss coefficient Ke, the eddy current loss Pev was calculated by the following Equation (4). Pev = Ke×f 2 ···(4)

[0048] Furthermore, based on the Pev of each small core and each large core of each example and each comparative example, ΔPev was calculated by the following Equation (5). The results are shown in Tables 1 to 5. Note that when ΔPev is 400 kW / m 3 the following cases were judged to be good. ΔPev = (Pev of the large core) - (Pev of the small core)···(5)

[0049]

Table 1

[0050] Table 1 mainly shows the experimental results of fixing the content of the secondary components and changing the composition of the main components.

[0051] As shown in Table 1, when the main component is composed of iron oxide at 51.0 to 53.5 mol% in terms of Fe 2 O 3 zinc oxide at 7 to 14 mol% in terms of ZnO, and the remaining manganese oxide, and contains a predetermined amount of secondary components (Examples 1 to 9), ΔPev is 400 kW / 3 or less, and it was confirmed that ΔPev is smaller than that in Comparative Examples 1 to 4.

[0052] [Table 2]

[0053] [Table 3]

[0054] In Tables 2 and 3, when the main component is composed of iron oxide at 52.6 mol% in terms of Fe 2 O 3 zinc oxide at 9.5 mol% in terms of ZnO, and the remaining manganese oxide, the experimental results when the contents of the secondary components Co and Ti are changed are shown.

[0055] As shown in Tables 2 and 3, when the secondary components are cobalt at 0.09 to 0.27 parts by mass in terms of CoO and titanium at 0.13 to 0.45 parts by mass in terms of TiO 2 (Examples 10 to 22), ΔPev is 400 kW / m 3 or less, and it was confirmed that ΔPev is smaller than that in Comparative Examples 5 to 12.

[0056] [Table 4]

[0057] In Table 4, the main component is Fe2 O 3 The graph shows the experimental results when the content of the auxiliary components Co and Ti was changed in a case where the composition was 52.2 mol % iron oxide converted into ZnO, 11.5 mol % zinc oxide converted into ZnO, and the remainder manganese oxide.

[0058] As shown in Table 4, the secondary components are 0.09 to 0.27 parts by mass of cobalt in terms of CoO, and TiO 2 In the case where the content is 0.13 to 0.45 parts by mass (Examples 23 to 29), ΔPev is 400 kW / m 3 The following was confirmed.

[0059] [Table 5]

[0060] Table 5 shows the experimental results when the contents of the auxiliary components Ca and Nb were changed.

[0061] As shown in Table 5, calcium is added as a secondary component (CaCO 3 Converted to 0.06 to 0.25 parts by mass, niobium to Nb 2 O 5 In the case where the content is 0.015 to 0.045 parts by mass (Examples 30 to 41), ΔPev is 400 kW / m 3 The following was confirmed.

[0062] Taking the results of Tables 1 to 5 together, it was confirmed that the change in eddy current loss due to differences in core size or shape can be suppressed by making the composition of the main components and the contents of each of the subcomponents (Co, Ti, Ca, Nb) all satisfy the standard range of the present invention. It was also confirmed that if even one of the main components and subcomponents does not satisfy the standard range, the change in eddy current loss due to differences in core size or shape increases.

Claims

1. A ferrite composition having a main component and a subcomponent, The main component is Fe. 2 O 3 % iron oxide calculated as 51.0 to 53.5 mol % iron oxide calculated as ZnO, 7 to 14 mol % zinc oxide calculated as ZnO, and the remainder manganese oxide, The auxiliary components are 0.09 to 0.27 parts by mass of cobalt in terms of CoO and 0.09 to 0.27 parts by mass of titanium in terms of TiO relative to 100 parts by mass of the main component. 2 0.13 to 0.225 parts by mass of calcium in terms of CaCO 3 0.06 to 0.25 parts by mass of niobium in terms of Nb 2 O 5 The ferrite composition contains 0.015 to 0.045 parts by mass in terms of the amount of the ferrite.

2. An electronic component comprising a sintered body made of the ferrite composition according to claim 1.

3. A power supply device comprising the electronic component according to claim 2.

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