Magnetic core

Abstract

To provide a magnetic core that uses a NiZn system ferrite that can suppress an increase of a change rate of a complex relative magnetic permeability against a temperature while having an excellent productivity.SOLUTION: An electron component 10 contains a magnetic core that contains Fe of 47.5 to 48.6 mol% in an Fe2O3 conversion, Zn of 29 to 30.1 mol% in a ZnO conversion, Cu of 5.5 to 6.5 mol% in a CuO conversion, and Ni of 14.8 to 18 mol% in a NiO conversion, and contains Mn that is 0.25 weight part or less in a Mn3O4 conversion against a total amount of Fe2O3, ZnO, CuO, and NiO, Ca that is 0.025 weight part or more and 0.25 weight part or less in a CaO conversion, and Si that is 0.05 weight part or less in a SiO2 conversion. The magnetic core contains: a first magnetic core 21 that includes a flange part to both end parts of column-like shaft parts; and a second magnetic core 22 that is derived to a space between the flange parts of the first magnetic core. The flange part includes: a first width on the side opposite to the second magnetic core; and a second width on the side that is not opposite to the second magnetic core. The first width is larger than the second width.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to NiZn ferrites.

Background Art

[0002] In recent years, in automobiles, a vehicle control system using an in-vehicle LAN (Local Area Network) that performs data communication by differential transmission between a plurality of electronic control devices has been adopted. Although various electronic components are used in the vehicle control system, a noise filter is used in the signal path to prevent leakage of noise in data communication, suppress external noise from overlapping the signal path, and prevent malfunction of in-vehicle devices. As the noise filter, a common-mode choke coil in which a conductor is wound around a ferrite core (hereinafter referred to as a magnetic core) is used. Although the configuration of the common-mode choke coil varies, for example, there is a common-mode choke coil that uses a drum-shaped core and a plate-shaped core covering it as the magnetic core, as described in Patent Document 1.

[0003] In the noise filter, the impedance Z represented by the product of the complex relative permeability μ of the soft ferrite constituting the magnetic core and the frequency is used for noise removal.

[0004] Generally, it is known that the complex relative permeability μ of soft ferrite has a Snoek limit in which the real part μ' decreases as the frequency increases due to the loss caused by magnetic resonance. The higher the complex relative permeability μ of the soft ferrite, the earlier the real part μ' begins to decrease from a relatively low frequency. As the real part μ' decreases, the imaginary part μ” increases, shows a peak, and then decreases. Such a complex relative permeability μ is represented by Equation 1, and according to the changes in the real part μ' and the imaginary part μ”, the impedance Z exponentially increases as the frequency increases, and shows a behavior of decreasing as the real part μ' and the imaginary part μ” decrease.

[0005]

Equation

[0006] For example, CAN (Controller Area Network) is known as a standard for differential transmission-based data communication that is widely used as an in-vehicle LAN. Since harmonics of the signal frequency (250 kHz or 500 kHz in CAN) may become radiated noise up to the tens of MHz band, the noise filter used in the signal path is required to have a large impedance in the high-frequency band of 10 MHz or higher so as to attenuate common-mode noise.

[0007] Also, the noise filter is used even in the engine room of an automobile where the temperature is high. Therefore, for example, so that it can be used in a wide temperature range of -40°C to +150°C, the magnetic transition temperature (Curie temperature Tc) of the soft ferrite is a temperature exceeding at least 150°C, which is higher than the temperature at which it is used, and it is required that the temperature dependence of the complex relative permeability μ is small.

[0008] In response to such requirements, Patent Document 2 discloses a soft ferrite for a noise filter containing Fe, Zn, Ni, Cu, Ti and having a compound containing Ti dispersed at the grain boundaries of an Fe-Zn-Ni-Cu crystal. It is described that the Curie temperature is 160°C or higher, the temperature change rate of the magnetic permeability can be suppressed to -40% or more and 40% or less, and an excellent noise filter having stable noise removal performance can be obtained in a wide temperature range from the low temperature range to the high temperature range.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] In Patent Document 2, in order to obtain a grain boundary structure in which a compound containing Ti is dispersed at the grain boundaries, it is necessary to add TiO2 to the calcined powders of Fe2O3, ZnO, NiO, and CuO powders, pulverize them, mold the obtained pulverized powder, and bake it at a predetermined temperature. Since post-addition of TiO2 is required, in the production of soft ferrites, an increase in production man-hours, the equipment used, and the types of raw materials is expected. Therefore, it may hinder the provision of magnetic cores at low cost. Further, according to Table 2 of Patent Document 2, as the amount of TiO2 increases, the Curie temperature Tc decreases, and the temperature change rate of the magnetic permeability on the high temperature side tends to increase, indicating room for further improvement.

[0011] Therefore, an object of the present invention is to provide a NiZn-based ferrite having a high Curie temperature, capable of suppressing the change rate of the complex relative magnetic permeability with respect to temperature, and excellent in productivity.

Means for Solving the Problems

[0012] The first invention is composed of Fe of 47.50 mol% or more and 48.60 mol% or less in terms of Fe2O3, Zn of 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, Cu of 5.50 mol% or more and 6.50 mol% or less in terms of CuO, and Ni of 15.00 mol% or more and 17.00 mol% or less in terms of NiO, and the total amount of Fe2O3, ZnO, NiO, and CuO is 100 mol%. When the total amounts of Fe, Zn, Ni, and Cu are each 100 parts by mass in terms of Fe2O3, ZnO, NiO, and CuO, a NiZn-based ferrite in which Mn is 0.250 parts by mass or less in terms of Mn3O4, Ca is 0.025 parts by mass or more and 0.250 parts by mass or less in terms of CaO, and Si is 0.050 parts by mass or less in terms of SiO2.

[0013] The NiZn-based ferrite of the present invention has a Curie temperature Tc of 165 °C or higher, a complex relative magnetic permeability μ 25 of 650 or higher, and a change rate Δη 25 of the complex relative magnetic permeability μ max with respect to the complex relative magnetic permeability μ max of 5% or less in absolute value, and the complex relative magnetic permeability μ 25Complex relative permeability μ with respect to min The rate of change Δμ min is preferably 20% or less in absolute value. However, the complex relative permeability μ max is the highest complex relative permeability μ under the condition of a frequency of 100 kHz between -40°C and 150°C, and the complex relative permeability μ min is the lowest complex relative permeability μ under the condition of a frequency of 100 kHz between -40°C and 150°C. Also, the rate of change Δμ max =(μ max -μ 25 ) / μ 25 × 100(%), and the rate of change Δμ min =(μ min -μ 25 ) / μ 25 × 100(%). Also, the complex relative permeability μ 25 is the complex relative permeability μ at a frequency of 100 kHz and a temperature of 25°C.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a NiZn-based ferrite having a high Curie temperature, capable of suppressing the rate of change of the complex relative permeability with respect to temperature, and excellent in productivity, a magnetic core using the same, and a noise filter.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0016] Hereinafter, the NiZn ferrite according to an embodiment of the present invention, the magnetic core using the same, and the noise filter will be specifically described. Unless otherwise specified, the description of one embodiment is also applicable to other embodiments. Further, the following description is not restrictive, and various changes and additions may be made within the scope of the technical idea of the present invention, and it can be changed as appropriate.

[0017] FIG. 7 is an external perspective view of a noise filter, and the NiZn ferrite of the present invention is used, for example, for its magnetic core. The noise filter 10 includes a drum-shaped core (first magnetic core) 21, a plate-shaped core (second magnetic core) 22, a winding 30 provided on the first magnetic core 21, and terminals 31 and 32. The second magnetic core 22 is arranged so as to cover the first magnetic core 21, and is configured in a closed magnetic circuit structure in which they are adhesively fixed to each other.

[0018] FIG. 6 is a perspective view showing the noise filter 10 of FIG. 7 excluding the second magnetic core 22. The first magnetic core 21 has a shaft portion (not shown) and a first flange portion 25 and a second flange portion 26 at its end. Two conducting wires are wound in a spiral bifilar winding on the shaft portion of the first magnetic core 21 to form a first conducting wire 30a and a second conducting wire 30b. Two terminals 31 and 32 are formed on the first flange portion 25 of the first magnetic core 21. Only the terminal 33 appears on the second flange portion 26, but two terminals similar to the first flange portion 25 are formed, and each of the flange portions has two terminals. One end of the first conducting wire 30a is connected to the first terminal 31, and the other end is connected to a second terminal (not shown). One end of the second conducting wire 30b is connected to the third terminal 32, and the other end is connected to the fourth terminal 33.

[0019] FIG. 5 is an equivalent circuit diagram of the noise filter (common mode choke coil) shown in FIG. 7. In the figure, terminal T1 corresponds to the first terminal 31 in the noise filter of FIG. 9. Also, terminal T2 corresponds to a second terminal not shown. Terminal T3 corresponds to the third terminal 32, and terminal T4 corresponds to the fourth terminal 33.

[0020] (Composition of NiZn-based ferrite) The NiZn-based ferrite used for the core consists of Fe of 47.50 mol% or more and 48.60 mol% or less in terms of Fe2O3, Zn of 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, Cu of 5.50 mol% or more and 6.50 mol% or less in terms of CuO, and Ni of 14.80 mol% or more and 18.00 mol% or more in terms of NiO, with the total amount of Fe2O3, ZnO, NiO, and CuO being 100 mol%. When the total amounts of Fe, Zn, Ni, and Cu are each 100 parts by mass in terms of Fe2O3, ZnO, NiO, and CuO, it is represented by a composition in which Mn is 0.250 parts by mass or less in terms of Mn3O4, Ca is 0.025 parts by mass or more and 0.250 parts by mass or less in terms of CaO, and Si is 0.010 parts by mass or less in terms of SiO2. In addition, inevitable impurity elements in the raw materials may be included.

[0021] Fe is preferably 47.50 mol% or more and 48.60 mol% or less in terms of Fe2O3. As the amount of Fe2O3 increases, the change rate Δμ of the complex relative permeability μ described later min and the change rate Δμ max increase in absolute value, and if it exceeds 48.60 mol%, the desired change rate Δμ min , Δμ max may not be obtained. Here, the desired change rate Δμ min , Δμ max refers to the case where the absolute values of the change rates Δμ min , Δμ max are each 40% or less. Also, if it is less than 47.50 mol%, the complex relative permeability μ at a temperature of 25°C 25 decreases, and the desired complex relative permeability μ 25 may not be obtained. The desired complex relative permeability μ 25is 650 or more. It is more preferable that Fe2O3 is 48.50 mol% or less. Further, 47.80 mol% or more is more preferable, and 48.00 mol% or more is even more preferable.

[0022] Zn is preferably 29.00 mol% or more and 30.10 mol% or less in terms of ZnO conversion. When ZnO is less than 29.00 mol%, the desired complex relative permeability μ 25 may not be obtained. When it exceeds 30.10 mol%, a Curie temperature Tc of 160 °C or higher may not be obtained. The change rate Δμ max is preferably 29.25 mol% or more and preferably 29.90 mol% or less to reduce it.

[0023] And the contents of Fe2O3 and ZnO are preferably 77.00 mol% or more and 78.50 mol% or less. By setting it to 77.00 mol% or more, the complex relative permeability μ 25 can be made 800 or more. More preferably, it is 77.30 mol% or more. Also, it is preferably 78.40 mol% or less.

[0024] Cu is preferably 5.50 mol% or more and 6.50 mol% or less in terms of CuO conversion. When CuO is less than 5.50 mol% or exceeds 6.50 mol%, the desired complex relative permeability μ 25 may not be obtained. The preferable content of CuO is 5.70 mol% or more. Also, 6.30 mol% or less is preferable.

[0025] Also, Ni is preferably 14.80 mol% or more and 18.00 mol% or less in terms of NiO conversion. The amount of NiO is the remainder obtained by subtracting the total amount of the above components of Fe2O3, ZnO, and CuO from 100 mol% of the total of Fe2O3, ZnO, NiO, and CuO.

[0026] As impurity elements, specifically, Si, Ca, B, C, S, Cl, Se, Br, P, Te, I, Li, Na, Mg, Al, K, Ga, Ge, Sr, In, Sn, Sb, Ba, Bi, Sc, Ti, Mn, V, Cr, Y, Nb, Mo, Pd, Ag, Hf, Ta, Zr, Co, Pb, etc. can be mentioned. In the present invention, except for Mn, Ca, and Si, any of them may be included as long as they do not affect the Curie temperature Tc of the NiZn ferrite and the change rate Δμ of the complex relative permeability with respect to temperature min , Δμ max , that is, within the range where the desired performance can be obtained.

[0027] Among the impurity elements, Mn, which is contained in a large amount in Fe2O3 as the raw material, increases the absolute value of the change rate Δμ of the complex relative permeability min , Δμ max as its amount increases. Therefore, the Mn contained in the raw material is set to about several thousand ppm or less in terms of oxide, and the Mn contained in the NiZn ferrite is preferably 0 parts by mass or more and 0.250 parts by mass or less in terms of Mn3O4 with respect to 100 parts by mass of the total amount of Fe, Zn, Ni, and Cu in terms of Fe2O3, ZnO, NiO, and CuO.

[0028] Although Si is preferable in that the Curie temperature Tc of the NiZn ferrite and the complex relative permeability μ 25 increase as its amount increases, the absolute value of the change rate Δμ of the complex relative permeability min , Δμ max also increases. Therefore, the Si contained in the NiZn ferrite is preferably 0 parts by mass or more and 0.050 parts by mass or less in terms of SiO2 with respect to 100 parts by mass of the total amount of Fe, Zn, Ni, and Cu in terms of Fe2O3, ZnO, NiO, and CuO. More preferably, it is 0.010 parts by mass or less.

[0029] Ca increases the change rate Δμ of the complex relative permeability of the NiZn ferrite min , Δμ maxIn order to reduce the absolute value of [[ID=]], it is preferable that Ca contained in the NiZn ferrite is 0.025 parts by mass or more and 0.250 parts by mass or less in terms of CaO based on 100 parts by mass in terms of Fe2O3, ZnO, NiO, and CuO.

[0030] Other impurity elements contained in the raw materials are preferably limited to about several ppm to several tens of ppm each in terms of oxide. Further, other inevitable impurities contained in the NiZn ferrite are preferably all 0.005 parts by mass or less.

[0031] Quantification of each component of Fe2O3, ZnO, NiO, and CuO can be performed by fluorescent X-ray analysis and ICP emission spectroscopic analysis. First, qualitative analysis of the contained elements (Fe, Zn, Ni, Cu, Mn, Zr, Sn, P, S, Bi, Mg, Al, Si, Cl, K, Ca, Ti, V, Cr, Co, Pb, etc.) is performed by fluorescent X-ray analysis, and then the contained elements are quantified by the calibration curve method of comparing with a standard sample. In addition, inevitable impurities can be quantified by means such as combustion-infrared absorption method and atomic absorption method. Note that except for Mn contained in a large amount in the raw material of Fe2O3, and Ca and Si that are abundant in nature and easily cause contamination, even if other elements are contained, they are in trace amounts. Therefore, based on the values calculated according to the composition ratios of Fe2O3, ZnO, NiO, and CuO from the amounts described in the inspection table of the raw materials of Fe2O3, ZnO, NiO, and CuO, the amounts contained in the NiZn ferrite can be calculated from the composition ratios without any problem.

[0032] (Method for manufacturing NiZn ferrite) Compounds (oxides) of Fe, Zn, Ni, and Cu elements constituting NiZn ferrite are used as raw materials, and after wet-mixing them at a predetermined ratio, they are dried to obtain raw material powder. The raw material powder is calcined at 700 °C or higher and at a temperature lower than the sintering temperature to promote spinelization and obtain a calcined body.

[0033] As the spinelization progresses, it takes more time to grind the calcined body. Therefore, the calcination temperature lower than the sintering temperature is preferably specifically 100 °C or more lower than the sintering temperature. On the other hand, when the calcination temperature is less than 700 °C, the spinelization is too slow and the time required for calcination becomes too long. Therefore, it is preferably 700 °C or more. The calcination temperature is preferably 850 °C or more. When the composition of the calcined body has a difference (deviation) from the desired composition, when grinding the calcined body, compounds of each element of Fe, Zn, Ni, and Cu may be added to adjust the composition.

[0034] The calcined body is put into a ball mill together with ion-exchanged water and wet-ground to form a slurry. The grinding of the calcined body is preferably carried out until the average particle size (measured by the air permeability method) of the ground powder is 1.2 μm or more and 2.5 μm or less, and more preferably until it is 1.5 μm or more and 2.0 μm or less. The grinding time is preferably 0.1 hour or more and 4.0 hours or less. If it is less than 0.1 hour, a preferable grinding particle size may not be obtained, and if it exceeds 4.0 hours, there is a risk of an increase in the mixing of impurities due to the wear of members such as the grinding media and containers of the grinder.

[0035] A binder such as polyvinyl alcohol is added to the slurry, granulated with a spray dryer, and then pressure-molded to obtain a molded body having a predetermined shape. The molded body is sintered in a firing furnace at a temperature of 1000 °C or more and 1200 °C or less to obtain a sintered body (a core of NiZn-based ferrite). The firing process includes a heating process, a temperature holding process, and a cooling process. The atmosphere in the firing process may be an inert gas atmosphere or an air atmosphere. In the temperature holding process at a temperature of 1000 °C or more and 1200 °C or less, it is preferable to hold for a predetermined time in a predetermined temperature range.

[0036] When the average grinding particle size of the calcined powder is small, the sintering reaction activity is high, and densification is easily promoted from a low temperature. On the other hand, when the set temperature of the firing furnace is high, sintering becomes excessive, a coarse crystal structure is generated, and it becomes difficult to obtain a sintered body with a uniform and dense crystal grain size. By setting the average particle size of the ground powder to 1.2 μm or more and the sintering temperature in the firing process to 1000 °C or more and 1200 °C or less, the complex relative permeability μ 25 and the change rate Δμ of the complex relative permeability μmin , Δμ max is preferably stabilized.

[0037] The complex relative permeability μ, the sintered body density ds, and the average crystal grain size d of the obtained sintered body can be measured by the following methods. Also, the change rate Δμ max、 Δμ min can be calculated.

[0038] (1) Complex relative permeability μ The sintered body is used as an annular magnetic core, and a coil component wound with a conductor around it is used as an evaluation sample. Using an LCR meter (4285A manufactured by Agilent Technologies), the inductance L m and the resistance R m are measured, and from the obtained inductance L m and the resistance R m , the complex relative permeability μ, its real part μ', and imaginary part μ'' are calculated using Equations 2 to 4.

[0039] (a) Real part μ' of the complex relative permeability μ

Equation

[0040] (b) Imaginary part μ'' of the complex relative permeability μ

Equation

[0041]

Equation

[0042] Note that the annular magnetic core has a rectangular cross-section orthogonal to the magnetic path, with an inner diameter of φ20 mm, an outer diameter of φ30 mm, and a thickness of 8 mm. Also, Ae is the effective cross-sectional area of the magnetic core (m 2 ), le is the effective magnetic path length of the magnetic core (m), and μ0 is the permeability of vacuum [4π×10 -7(H / m), N is the number of turns of the conductor, f is the frequency (Hz), Lm is the measured inductance (H), and Rm is the measured resistance (Ω). The conductor used was enameled wire with a wire diameter of φ0.5 mm, and the number of turns N was 20 turns.

[0043] (2) Rate of change Δμ of the complex relative permeability μ max , Δμ min Connect the evaluation sample used for measuring the complex relative permeability μ to the measurement jig in the thermostat. The measurement jig is connected to an LCR meter (4285A). Between -40°C and 150°C, change the temperature of the evaluation sample and measure the inductance L m and resistance R m at a frequency of 100 kHz. The inductance L m and resistance R m obtained under the condition of temperature T are used to calculate the complex relative permeability μ T from Equation 2 to Equation 4. The complex relative permeability μ T is the complex relative permeability μ at temperature T. For example, the complex relative permeability μ 25 is the complex relative permeability μ at 25°C. Also, the complex relative permeability μ max is the highest complex relative permeability μ at temperatures from -40°C to 150°C, and Tμ max is the temperature at which the complex relative permeability becomes μ max . Also, the complex relative permeability μ min is the lowest complex relative permeability μ at temperatures from -40°C to 150°C, and Tμ min is the temperature at which the complex relative permeability becomes μ min . Using the obtained complex relative permeability μ, calculate the rate of change Δμ max from Equation 5 and the rate of change Δμ min from Equation 6.

[0044] The maximum rate of change Δμ on the positive side of the complex relative permeability μ max is the absolute value calculated by Equation 5.

Equation

[0045] The maximum rate of change Δμ on the negative side of the complex relative permeability μmin is the absolute value calculated by Equation 6. [Number]

[0046] (3) Curie temperature Tc The Curie temperature Tc was determined in accordance with JIS C2560 using an LCR meter with similar samples.

[0047] (4) Sintered body density ds The density was calculated by the volume-weight method from the dimensions and weight of the sintered body of NiZn-based ferrite. The sintered body density was 5.10×10 3 kg / m 3 was used as the threshold value, and values exceeding the threshold were judged as "good". If the sintered body density is small, insufficient sintering is considered, the mechanical strength is inferior, and chipping and cracking are likely to occur.

[0048] (5) Average crystal grain size The sintered body of NiZn-based ferrite was thermally etched at a temperature lower than the firing temperature, and a scanning electron microscope (SEM) photograph (3000 times magnification) of its surface was taken. The observed area of the SEM photograph was 33 μm × 43 μm at 3000 times magnification. Three arbitrary straight lines of length L1 were drawn on the SEM photograph, the number N1 of crystal grains existing on each straight line was counted, the value L1 / N1 obtained by dividing the length L1 by the number of particles N1 for each straight line was calculated, and the sum of the values of L1 / N1 was divided by 3 to obtain the average crystal grain size. Note that thermal etching may be performed at a temperature at which grain boundaries can be confirmed, and typically it is preferably performed at a temperature about 50 °C to 100 °C lower than the firing temperature. When the firing temperature of the sintered body of NiZn-based ferrite is unknown, thermal etching may be started at a low temperature and the temperature may be increased little by little until grain boundaries can be confirmed. [Examples]

[0049] Reference Examples 1 to 21 and Comparative Examples 1 to 9 The respective raw materials of Fe2O3 powder, ZnO powder, CuO powder, and NiO powder were weighed so as to obtain a NiZn ferrite having the composition shown in Table 1, wet-mixed, dried, and calcined at a temperature of 900 °C for 1 hour. Each of the obtained calcined bodies was put into a ball mill together with ion-exchanged water and pulverized to form a slurry. A part of the obtained slurry was dried and the average pulverized particle size was evaluated by the air permeability method. All of the average pulverized particle sizes were in the range of 1.5 μm to 1.7 μm. Polyvinyl alcohol was added to the remaining slurry as a binder, dried and granulated by a spray dryer, and pressure-molded to obtain each annular molded body. In addition, Mn in the NiZn ferrite is selected such that when the total amount of Fe2O3, ZnO, CuO, and NiO is 100 parts by mass, the total amount of Mn3O4, CaO, and SiO2 in terms of oxide is 0.250 parts by mass or less.

[0050] Each molded body was sintered at a temperature of 1100 °C for a holding time of 2 hours to obtain each annular NiZn ferrite sintered body having an outer diameter of 30 mm × inner diameter of 20 mm × thickness of 8 mm. The firing atmosphere was in air.

[0051] The density ds, complex relative permeability μ, real part μ' of the complex relative permeability μ, imaginary part μ" of the complex relative permeability μ, average crystal grain size, Curie temperature Tc, change rates Δμmin, Δμmax of the complex relative permeability μ, and normalized impedance Z of each NiZn ferrite sintered body N were measured or calculated by the above method. The obtained results are also shown in Table 1 and FIGS. 1 to 6. In Table 1, the change rate Δμ of the complex relative permeability μ -40 , Δμ 100 , Δμ 150 is the change rate of the complex relative permeability μ 25 with respect to the reference complex relative permeability μ T (T = -40 °C, 100 °C, 150 °C). When μ 25 is smaller than μ T and the change rate Δμ is negative, it is indicated with a minus sign. In FIGS. 1 to 4, the reference examples are indicated by white circles, the comparative examples are indicated by cross marks and black square marks, and the black square marks among them also indicate that the Curie temperature Tc is less than 160 °C.

[0052]

Table 1

[0053]

Table 2

[0054] For both the reference examples and the comparative examples, all NiZn - based ferrite sintered compacts had a good density \(d_s\) exceeding \(5.15\times10\) 3 kg / m 3 and were in the range of 5 μm to 20 μm for the average crystal grain size.

[0055] Figure 2 is a diagram showing the relationship between the ZnO content and the Curie temperature \(T_c\) of NiZn - based ferrite. As the ZnO content increased, the Curie temperature \(T_c\) decreased, and from Comparative Example 5 where the ZnO exceeded 30.10 mol% to Comparative Example 8, it was less than 160 °C.

[0056] Figures 3 and 4 are diagrams showing the relationship between the \(Fe_2O_3\) content and the change rates \(\Delta\mu_{max}\), \(\Delta\mu_{min}\) of the complex relative permeability \(\mu\). The change rate \(\Delta\mu\) max of the complex relative permeability \(\mu\) increased rapidly when the \(Fe_2O_3\) content exceeded 48.60 mol%. Also, the change rate \(\Delta\mu\) min of the complex relative permeability \(\mu\) tended to increase gently with respect to the \(Fe_2O_3\) content. Moreover, in Comparative Examples 5 to 8 where the Curie temperature \(T_c\) was less than 160 °C, the temperature at which the complex relative permeability \(\mu\) min was 150 °C, while for other evaluation samples it was - 40 °C, and the change rate \(\Delta\mu\) min increased significantly.

[0057] Figure 1 is a diagram showing the relationship between the total amount of \(Fe_2O_3\) and \(ZnO\) in NiZn - based ferrite and the complex relative permeability \(\mu\). As the total amount of \(Fe_2O_3\) and \(ZnO\) increased, the complex relative permeability \(\mu\) also increased.

[0058] Examples 1 - 4 and Comparative Examples 22 - 27 Weighed each raw material of Fe2O3 powder, ZnO powder, CuO powder, NiO powder, Mn3O4 powder, CaCO3 powder, and SiO2 powder so as to obtain a NiZn ferrite having the composition shown in Table 2. After wet-mixing the Fe2O3 powder, ZnO powder, CuO powder, and NiO powder, it was dried and calcined at a temperature of 900 °C for 1 hour. Each of the obtained calcined bodies was put into a ball mill together with Mn3O4 powder, CaCO3 powder, SiO2 powder, and ion-exchanged water, and pulverized with an attritor to obtain a slurry. A part of the obtained slurry was dried, and the average pulverized particle size was evaluated by the air permeability method. All the average pulverized particle sizes were in the range of 1.7 μm to 1.9 μm. Polyvinyl alcohol was added to the remaining slurry as a binder, and dried and granulated with a spray dryer, and then pressure-molded to obtain each annular molded body.

[0059] Each molded body was sintered at a temperature of 1100 °C for a holding time of 2 hours to obtain each annular NiZn ferrite sintered body having an outer diameter of 30 mm × inner diameter of 20 mm × thickness of 8 mm. The firing atmosphere was in air.

[0060] The density ds, complex relative permeability μ, Curie temperature Tc, and change rate Δμ of the complex relative permeability μ of each NiZn ferrite sintered body min , Δμ max were measured or calculated by the above method. The obtained results are shown in Table 3. In Table 3, Fe, Zn, Ni, and Cu are shown as the main components, while Mn3O4, CaO, and SiO2 are shown as the sub-components.

[0061]

Table 3

[0062]

Table 4

[0063] In both the examples and comparative examples, the density ds of each NiZn ferrite sintered body was 5.15×10 3 kg / m 3It was better than that. Also, the average crystal grain size was in the range of 5 μm to 20 μm.

[0064] When the amount of CaO increases, the change rate Δμ of the complex relative permeability min , Δμ max The absolute value of becomes smaller. In Examples 1 to 5 where the range is 0.025 parts by mass or more and 0.250 parts by mass or less, the absolute value of the change rate Δμ min is 20% or less, and the absolute value of Δμ max is 5% or less, greatly reducing the change rate of the complex relative permeability with respect to temperature. On the other hand, in Comparative Examples 22, 24 to 26 where the amount of CaO is 0.010 parts by mass or less, the change rates Δμ min , Δμ max are large. In Comparative Example 23 where the amount of CaO is 0.019 parts by mass, the change rates Δμ min , Δμ max are improved, but the change rate Δμ min exceeds 20%. Also, in Comparative Examples 22 and 24 where the amount of Mn3O4 exceeds 0.250 parts by mass and in Comparative Example 26 where the amount of SiO2 exceeds 0.050 parts by mass, the change rates Δμ min , Δμ max are large, and in Comparative Examples 25 and 26, the Curie temperature Tc was less than 165 °C.

[0065] As described above, consisting of 47.50 mol% or more and 48.60 mol% or less in terms of Fe2O3, 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, 5.50 mol% or more and 6.50 mol% or less in terms of CuO, and 14.80 mol% or more and 18.00 mol% or less in terms of NiO, with the total amount of Fe2O3, ZnO, NiO, and CuO being 100 mol%, and when the total amounts of Fe, Zn, Ni, and Cu are each 100 parts by mass in terms of Fe2O3, ZnO, NiO, and CuO, Mn is 0.250 parts by mass or less in terms of Mn3O4, Ca is 0.025 parts by mass or more and 0.250 parts by mass or less in terms of CaO, and Si is 0.050 parts by mass or less in terms of SiO2, for the NiZn-based ferrite, the Curie temperature Tc is high, and the change rates Δμ min , Δμ maxIt can be made into a NiZn ferrite with a small [value]. Also, since there is no need to have a complex organizational structure, it is excellent in productivity.

Explanation of symbols

[0066] 10 Electronic component 21 First core 22 Second core 30 Coil (conductive wire) 31, 32, 33 Terminals

Claims

1. Fe ２ O ３ in terms of conversion, Fe of "47.50 mol% or more and 48.60 mol% or less", and Zn in terms of ZnO of "29.00 mol% or more and 30.10 mol% or less", Cu in terms of CuO of "5.50 mol% or more and 6.50 mol% or less", Ni in terms of NiO of "14.80 mol% or more and 18.00 mol% or less", are contained, and Fe ２ O ３ When the total amount of ZnO, CuO and NiO is 100 mol%, Mn ３ O ４ In terms of conversion, it contains Mn of "0.250 parts by mass or less", Ca of "0.025 parts by mass or more and 0.250 parts by mass or less" in terms of CaO conversion, and Si of ２ "0.050 parts by mass or less" in terms of conversion, and is a magnetic core using NiZn-based ferrite. the magnetic core has a columnar shaft portion and a first magnetic core having flange portions at both ends of the shaft portion, and a second magnetic core spanned between the flange portions of the first magnetic core, the flange portion has a first width on the side facing the second magnetic core and a second width on the side not facing the second magnetic core, the first width is larger than the second width, magnetic core.

2. In the magnetic core according to Claim 1, the NiZn ferrite has a Curie temperature Tc of 165°C or higher, Complex relative permeability μ ２５ is the complex relative permeability μ under the conditions of "frequency 100 kHz and temperature 25°C", and is 650 or more, Complex relative permeability μ ｍａｘ is the highest complex relative permeability μ among the complex relative permeabilities μ under the conditions of "frequency 100 kHz, from -40°C to 150°C", and Complex relative permeability μ ｍｉｎ is the lowest complex relative permeability μ among the complex relative permeabilities μ under the condition of "frequency 100 kHz, from -40°C to 150°C", and The complex relative permeability μ ２５ The change rate Δμ ｍａｘ of the complex relative permeability μ ｍａｘ is 5% or less in absolute value, where "Δμ ｍａｘ = (μ ｍａｘ - μ ２５ ) / μ ２５ × 100 (%)", The complex relative permeability μ ２５ The change rate Δμ ｍｉｎ of the complex relative permeability μ ｍｉｎ is 20% or less in absolute value, where "Δμ ｍｉｎ = (μ ｍｉｎ - μ ２５ ) / μ ２５ × 100 (%)". magnetic core.

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