JP2016113330A - Ferrite core, electronic component and power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite core having suppressed sound squeak during driving near 100°C, high in saturation magnetic flux density and having core strength.SOLUTION: There is provided a MnZn-based ferrite containing a main component of iron oxide of 50.5 o 55.5 mol% in terms of FeOand zinc oxide of 7.0 to 11.5 mol% in terms of ZnO and the balance manganese oxide and containing Ni of 500 to 10000 ppm in terms of NiO, Ti of 100 to 6000 ppm in terms of TiO, Co of 500 to 4000 ppm in terms of CaO, Si of 50 to 300 ppm in terms of SiO, Ca of 200 to 3000 ppm in terms of CaO based on the main component, which is a polycrystalline material having a spinel structure and has a composition ratio of Ca and Si in a grain boundary satisfying a relational expression.SELECTED DRAWING: None

Description

The present invention relates to a ferrite core having a high saturation magnetic flux density in the vicinity of 100 ° C., suppression of noise during driving, and high strength.

Ferrite sintered bodies are used as magnetic core materials for power transformers and the like. The ferrite sintered body forming the core (magnetic core) is called a ferrite core, and MnZn-based ferrite containing Mn and Zn is widely used. In recent years, with the miniaturization of power supplies, ferrite cores are also required to have a high saturation magnetic flux density due to miniaturization and low profile. Further, the ferrite core is easily cracked or chipped when mounted on a power source, during transportation, or used, and the core strength is a problem. Furthermore, the noise during use is also a problem, and a reduction in noise is also required.

As a method for increasing the strength of the core, for example, in Patent Document 1, ZnO: 10.0 to 15.0 mol%, Fe ₂ O ₃ : 52.0 to 54.0 mol%, MnO: the basic component having the remaining component composition _{, Bi 2 O 3: 0.0050~0.0200mass%} , SiO 2: 0.0050~0.0500mass% and CaO: it is described that contains a 0.0200~0.2000mass%.

As a method for suppressing sound generation, for example, Patent Document 2 describes providing a transformer in which transformer noise is reduced or prevented by sandwiching a damping material between the legs of a core having a plurality of legs. Has been.

JP 2000-138117 A JP2013-118308A

However, although the core strength is improved in Patent Document 1, the saturation magnetostriction that causes the noise is not reduced in this technique, and thus the suppression of the noise during driving is not sufficient. In Patent Document 2, although noise is reduced, magnetostriction is not reduced and it cannot be said to be a fundamental solution.

Accordingly, an object of the present invention is to provide a ferrite core that can solve the above-described problems of the prior art. In particular, an object is to provide a ferrite core having a high saturation strength with a high saturation magnetic flux density at 100 ° C. by reducing magnetostriction at 100 ° C. to suppress noise during driving.

For this purpose, the present inventors have determined the composition, grain boundaries and grains of iron oxide and zinc oxide as main components contained in MnZn-based ferrite, and nickel oxide, cobalt oxide, titanium oxide, silicon oxide and calcium oxide as subcomponents. Focusing on the composition ratio of silicon and calcium in the vicinity of the boundary, we conducted intensive research on the characteristics. As a result, it has been found that the noise during driving at 100 ° C. can be suppressed, the saturation magnetic flux density is high, and a high core strength can be realized, and the present invention has been completed.

That is, the ferrite core of the present invention, 50.5～55.5Mol% iron oxide calculated as _Fe 2 _{O 3,} 7.0～11.5Mol% of zinc oxide calculated as ZnO, the main balance being manganese oxide It is MnZn type ferrite containing a component, and Ni contains 500 to 10000 ppm in terms of NiO, Ti contains 100 to 6000 ppm in terms of TiO ₂ , and Co contains 500 to 4000 ppm in terms of CoO. , MnZn-based ferrite containing 50 to 300 ppm of Si in terms of SiO ₂ and 200 to 3000 ppm of Ca in terms of CaO, wherein the MnZn-based ferrite is a polycrystal having a spinel structure, and Ca in grain boundaries The composition ratio X of Ca and Si at the point A at which the concentration is maximum and the point B that advances from the point A in the 5 nm intragranular direction That Ca and Si composition ratio Y is a ferrite core which satisfy the following relational expression.
Relational expressions: 0.5 ≦ X ≦ 1.0, X + 0.05 ≦ Y ≦ X + 0.50
However, X and Y are represented by the following formulas, X and Y = Ca concentration (at%) / Si concentration (at%)
And

In the ferrite core of the present invention, as subcomponents, Nb is 50 to 750 ppm in terms of Nb ₂ O ₅ , Ta is 50 to 1500 ppm in terms of Ta ₂ O ₅ , and V is 50 in terms of V ₂ O ₅ as subcomponents. It is preferably characterized by containing ˜1000 ppm and Sn containing one or more of 500 to 8000 ppm in terms of SnO ₂ .

It is possible to suppress the noise during driving near 100 ° C., achieve a high saturation magnetic flux density at 100 ° C., and high core strength.

First, the reasons for limiting the components in the present invention will be described.
The ferrite core of the present invention has a high saturation magnetic flux density at 100 ° C. by appropriately selecting the composition as follows, and can reduce noise during driving by reducing the saturation magnetostriction at 100 ° C.

In the ferrite core of the present invention, the amount of Fe as a main component is set to 50.5 to 55.5 mol% in terms of Fe ₂ O ₃ . In the following, the notation of Fe amount in terms of Fe ₂ O ₃ is simply expressed as Fe ₂ O ₃ amount or the like. When the amount of Fe ₂ O ₃ is less than 50.5 mol%, the saturation magnetostriction is reduced, but the saturation magnetic flux density is reduced. On the other hand, when the amount of Fe ₂ O ₃ exceeds 55.5 mol%, the saturation magnetostriction becomes large. Therefore, in the present invention, the amount of Fe ₂ O ₃ is set to 50.5 to 55.5 mol%. A preferred amount is 51.5 to 54 mol%.

The amount of ZnO also affects the saturation magnetic flux density and saturation magnetostriction. When the amount of ZnO is less than 7.0 mol%, the saturation magnetostriction becomes large. When ZnO exceeds 11.5 mol%, the saturation magnetic flux density is reduced. Therefore, in the present invention, the amount of ZnO is set to 7.0 to 11.5 mol%. The ferrite core of the present invention is composed of MnO as the main component except for the inevitable impurities other than the above.

Next, subcomponents in the present invention will be described.
In the ferrite core of the present invention, the amount of Ni is 500 to 10,000 ppm in terms of NiO as a subcomponent. NiO is effective in suppressing magnetostriction, and is added in an amount of 500 ppm or more with respect to the main component in order to obtain the effect. However, when there is too much addition amount, a saturation magnetic flux density will become small. Therefore, in the present invention, the amount of NiO is 10000 ppm or less. A preferred amount is 2000-10000 ppm.

The ferrite core of the present invention has an amount of TiO ₂ of 100 to 6000 ppm as a subsidiary component. TiO ₂ can be replaced with Fe in the spinel lattice as tetravalent Ti ions to reduce magnetostriction. In order to obtain the effect, 100 ppm or more is added to the main component. However, when the addition amount is too large, the saturation magnetic flux density becomes small. Therefore, in the present invention, the amount of TiO ₂ is set to 6000 ppm or less. A preferred amount is 1000 to 3000 ppm.

The ferrite core of the present invention has a CoO content of 500 to 4000 ppm as a subcomponent. CoO is effective in suppressing magnetostriction, and in order to obtain the effect, 500 ppm or more is added to the main component. However, when the addition amount is too large, the saturation magnetic flux density is reduced. Therefore, in this invention, the amount of CoO shall be 4000 ppm or less. A preferable amount of CoO is 500 to 3000 ppm.

Moreover, the effect is further enhanced by adding Ni, Ti and Co simultaneously. Ni or Co can be dissolved in the B site to obtain a magnetostriction suppressing effect. However, when these are added alone, they are dissolved not only in the B site but also in the A site, and a sufficient effect on the amount added cannot be obtained. However, by adding Ti at the same time, Ni and Co are easily dissolved in the B site, and a larger magnetostriction suppressing effect can be obtained than when adding alone.

In addition, the ferrite core of the present invention can improve the core strength by controlling the segregation amount and solid solution amount of Si and Ca.

The ferrite core of the present invention can contain 50 to 300 ppm of SiO ₂ and 200 to 3000 ppm of CaCO ₃ as subcomponents. Si and Ca are segregated at the grain boundaries to form a high resistance layer and contribute to low loss, and have the effect of improving the sintering density as a sintering aid. If the amount of SiO ₂ is less than 50 ppm or the amount of CaCO ₃ is less than 200 ppm, the above effect cannot be obtained sufficiently. On the other hand, when the amount of SiO ₂ exceeds 300 ppm or the amount of CaCO ₃ exceeds 3000 ppm, abnormal grains grow and the strength decreases. Therefore it is preferable to 500~2000ppm the 50~150ppm and CaCO ₃ content of SiO ₂ amount, it is preferable to further 800~1600ppm the 75~125ppm and CaCO ₃ content of SiO ₂ amount.

FIG. 1 is a schematic diagram of a cross section of a ferrite core. The Mn—Zn-based ferrite 100 is formed from particles 1 and grain boundaries 2. As shown in the figure, the composition analysis of Si and Ca is performed in the grain boundary normal direction of an arbitrary two grain boundary, and the point where the Ca concentration becomes maximum is A, and the point 5 nm away from there in the grain boundary normal direction. B. The inventors have found that the strength of the Mn—Zn ferrite is improved when the composition ratio of Ca and Si (Ca / Si ratio) at each point satisfies the following relational expression. Here, the composition ratio at point A was X and the composition ratio at point B was Y.
Relational expressions: 0.5 ≦ X ≦ 1.0, X + 0.05 ≦ Y ≦ X + 0.50

In addition, when determining points A and B, grain boundaries shared by three or more grains were avoided. This is because a grain boundary shared by a large number of grains is expected to have a grain boundary segregation state different from that of a two grain grain boundary, and the grain boundary normal direction cannot be determined as one.

In the present invention, it is considered that the stress applied to the crystal lattice is gradually attenuated by satisfying the above-described relational expression so that Ca has a composition distribution that gradually attenuates compared to Si from the particle interface to the particle internal direction. It is done. That is, it is considered that the stress applied to the crystal lattice inside the particle is relaxed, the crystal lattice inside the particle exists stably in terms of energy, and expresses high strength as a whole crystal.

Moreover, in this invention, a core loss can be suppressed by restrict | limiting a subcomponent as follows.
The ferrite core of the present invention can contain Nb ₂ O _{5 in an} amount of 50 to 750 ppm and Ta ₂ O ₅ in the range of 50 to 1500 ppm as subcomponents. Nb and Ta are components that have a function of increasing the grain boundary resistance. If the amount of Nb ₂ O ₅ is less than 50 ppm or the amount of Ta ₂ O ₅ is less than 50 ppm, there is no improvement effect. Further, if the amount of Nb ₂ O ₅ exceeds 750 ppm or the amount of Ta ₂ O ₅ exceeds 1500 ppm, the core loss increases due to abnormal grain growth. Therefore, the amount of Nb ₂ O ₅ is 50 to 750 ppm and the amount of Ta ₂ O _{5 is} increased. It limited to the range of 50-1500 ppm. When the content increases, abnormal grain growth occurs, so that it is preferable to contain Nb ₂ O _{5 in} the range of 100 to 300 ppm and Ta ₂ O ₅ in the range of 100 to 500 ppm.

The ferrite core of the present invention can contain V ₂ O ₅ in the range of 50 to 1000 ppm as a subcomponent. V is a component having a function of increasing the grain boundary resistance. If the amount of V ₂ O ₅ is less than 50 ppm, there is no improvement effect. _Further, since V 2 _{O 5} weight core loss increases due to abnormal grain growth exceeds 1000 _ppm, with limited V 2 _{O 5} amount in the range of 50 to 1000 ppm. When the content is increased, abnormal grain growth occurs, so that the amount of V ₂ O ₅ is preferably contained in the range of 100 to 500 ppm.

The ferrite core of the present invention may contain 500 to 8000 ppm of SnO ₂ as a subcomponent. Sn is a component that partially exists at the grain boundary and promotes grain boundary reoxidation in the cooling process after sintering to reduce the loss. SnO ₂ also serves to lower the bottom temperature by substituting with atoms of the spinel lattice as tetravalent ions. However, if the addition amount is too large, abnormal grain growth is caused and the loss becomes high. Therefore, the SnO ₂ amount is contained in the range of 500 to 8000 ppm. Preferably, the amount of SnO ₂ is contained in the range of 1000 to 3000 ppm. These components are not necessarily added in the form of an oxide, and may be mixed in the form of a carbonate, for example.

Next, a manufacturing method suitable for the ferrite core according to the present invention will be described.
As the raw material of the main component, an oxide or a powder of a compound that becomes an oxide by heating is used. Specifically, Fe ₂ O ₃ powder, Mn ₃ O ₄ powder, ZnO powder, or the like can be used. What is necessary is just to select suitably the average particle diameter of each raw material powder in the range of 0.1-3.0 micrometers. The raw material powder of the main component is wet mixed and then calcined. The calcining temperature may be a predetermined temperature within the range of 800 to 1100 ° C. What is necessary is just to select the stable time of calcination suitably in the range of 0.5 to 5.0 hours. After the calcination, the calcined material is pulverized, for example, to an average particle size of about 0.5 to 3.0 μm. In the present invention, not only the above-mentioned main component materials, but also a composite oxide powder containing two or more metals may be used as the main component materials. For example, a complex oxide powder containing Fe and Mn can be obtained by oxidizing and baking an aqueous solution containing iron chloride and manganese chloride. This powder and ZnO powder may be mixed and used as a main component material. In such a case, calcining is unnecessary.

Add subcomponents after calcination. For the addition after the calcining, the above-mentioned pulverization may be performed by adding the subcomponent raw material to the calcined material, or the subcomponent raw material may be added and mixed after the calcining of the calcined material. However, NiO, TiO ₂ , and CoO can be calcined together with the main component raw materials.
As a subcomponent material, an oxide or a powder of a compound that becomes an oxide by heating can also be used. Specifically, NiO powder, Mn ₃ O ₄ powder, SiO ₂ powder, CaCO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, or the like can be used.

The mixed powder composed of the main component and the subcomponent is granulated into a granule in order to smoothly execute the subsequent molding process. Granulation can be performed using, for example, a spray dryer. A small amount of a suitable binder such as polyvinyl alcohol (PVA) is added to the mixed powder, and this is sprayed and dried with a spray dryer. The particle size of the obtained granules is preferably about 80 to 300 μm.

The obtained granules are molded into a desired shape using, for example, a press having a mold having a predetermined shape, and this molded body is subjected to a firing step.
In the firing step, it is necessary to control the firing temperature and firing atmosphere. The firing temperature can be appropriately selected from the range of 1250 to 1500 ° C., but it is preferably fired in the range of 1300 to 1400 ° C. in order to sufficiently bring out the effect of the ferrite core of the present invention. As the firing atmosphere, the oxygen partial pressure may be appropriately adjusted in a mixed atmosphere of nitrogen and oxygen.

It cools from the maximum temperature in a baking process to 950 degreeC, and holds temperature at 950 degreeC for 2 hours. By holding at a constant temperature, an amorphous grain boundary layer containing Si, Ca, Nb and the like as additive elements is formed. Next, the temperature is raised again to 1200 ° C., maintained at 1200 ° C. for 10 to 40 minutes, and then cooled to room temperature. By this temperature holding operation at 1200 ° C., a state in which Ca is appropriately dissolved in the crystal grains can be realized, and as a result, the stress applied to the crystal grains from the crystal grain boundary can be relaxed. When the holding time at 1200 ° C. is short, the solid solution of Ca into the crystal grains becomes insufficient, so that the stress applied to the crystal grains from the grain boundary increases, and the effect of improving the strength cannot be obtained. On the other hand, if the holding time at 1200 ° C. is long, the formation of grain boundaries becomes insufficient because Ca is excessively dissolved in the crystal grains, leading to a decrease in strength and an increase in magnetic loss.

In the general firing process of the ferrite core, reheating is not performed at the time of cooling. However, by performing reheating, the intragranular solid solution of Ca is promoted and sufficient strength can be obtained.

The sintered ferrite core according to the present invention can obtain a relative density of 93% or more, more preferably 95% or more.
The ferrite core obtained by the present invention can be used for a transformer, and the transformer obtained by the present invention can be used for a switching power supply device.

FIG. 2A is a perspective view showing an E-shaped ferrite core (magnetic core) according to this embodiment. As shown in FIG. 2A, the E-shaped ferrite core 200 is called an E-type core and is used for a transformer or the like. As a transformer in which an E-type core such as the ferrite core 200 is adopted, a transformer in which two E-type cores are arranged to face each other as shown in FIG. 2B is known.

FIG. 3 is a block diagram showing the configuration of the switching power supply apparatus.

A switching power supply device 300 shown in FIG. 3 is a device (DC / DC converter) for converting a DC input voltage Vin into a DC output voltage Vout, and an input filter 301 that removes a noise component contained in the DC output voltage Vin. The switching circuit 302 that converts the output of the input filter 301 into alternating current, the transformer 303 that transforms the output of the switching circuit 302, the rectifier circuit 304 that converts the output of the transformer 303 into direct current, and the output of the rectifier circuit is smoothed And a smoothing circuit 305. In the switching power supply 300 having such a configuration, if the core according to the present invention is used as the core of the transformer 303, the heat generated in the transformer 303 is efficiently discharged, so that the reliability of the switching power supply 300 is improved. It becomes possible.

The switching power supply device 300 shown in FIG. 3 is particularly preferably used as a switching power supply device for automobiles.

FIG. 4 is a block diagram schematically showing main parts of an automobile provided with the switching power supply device 300.

As shown in FIG. 4, when the switching power supply device 300 is used for an automobile, the switching power supply device 300 is provided between the high voltage battery 310 and the electric equipment 320 and the low voltage battery 330 and is supplied from the high voltage battery 310. The high voltage of about 144V or about 288V is stepped down to about 14V and supplied to the electric device 320, and the low voltage battery 330 is charged. Examples of the electric device 320 include an air conditioner and an audio device provided in an automobile.

Charging the high voltage battery 310 is performed by electric power supplied from the power generation device 340. The output of the high voltage battery 310 is also supplied to the motor 350, and the motor 350 drives the drive system 360 based on a high voltage (about 144V or about 288V) supplied from the high voltage battery 310. In the fuel cell vehicle, the fuel cell body is the power generation device 340, and in the hybrid vehicle, the motor 350 also serves as the power generation device 340.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

Hereinafter, the present invention will be described based on specific examples.
Fe ₂ O ₃ powder, Mn ₃ O ₄ powder and ZnO powder as raw materials of main components, NiO powder, TiO ₂ powder, Co ₃ O ₄ powder, SiO ₂ powder, CaCO ₃ powder, Nb ₂ O ₅ as raw materials of subcomponents Powder, V ₂ O ₅ powder, Ta ₂ O ₅ powder and SnO ₂ powder were used.

In Tables 1, 3, and 4, Fe ₂ O ₃ was 53.5 mol%, ZnO was 10.0 mol%, and the balance was MnO. In Table 1, a material in which NiO is 7000 ppm, TiO ₂ is 1000 ppm, CoO is 2000 ppm, SiO ₂ is 100 ppm, CaCO ₃ is 1000 ppm, and Nb ₂ O ₅ is added at a ratio of 200 ppm to the main components as subcomponents. The composition of the main component in Table 2 and the composition of the subcomponents in Tables 2 to 4 are shown in the table. Further, in Table 2, in addition to the materials shown in the table, SiO ₂ was added at 100 ppm, CaCO ₃ was added at 1200 ppm, Nb ₂ O ₅ was added at 200 ppm, and in Table 3, Nb ₂ O ₅ was added at 200 ppm in addition to the materials shown in the table.

After these powders were wet mixed, they were calcined in the atmosphere at 900 ° C. for 3 hours.
A binder was added to the obtained mixture, granulated, and molded to obtain a toroidal shaped body, an I-shaped shaped body, and an E-shaped shaped body. The obtained molded body was fired under the following conditions under oxygen partial pressure control. The temperature was maintained at 1300 ° C. and an oxygen partial pressure of 1.0 vol% for 5 hours, then cooled to 950 ° C., and maintained at 950 ° C. for 2 hours. Next, the temperature was raised again to 1200 ° C., maintained at 1200 ° C. for 0 to 40 minutes, and then cooled to room temperature. In Table 1, the molded body was fired under different cooling conditions.

Thus, a toroidal ferrite core (outer diameter 20 mm, inner diameter 10 mm, thickness 5 mm), I-shaped ferrite core (length 70 mm, width 8 mm, thickness 8 mm) and E-shaped ferrite core (Length 40 mm, height 15 mm, width 5 mm) was obtained.

Next, the measurement method of the present invention will be described.
The magnetostriction at 100 ° C. was measured using a strain gauge (KFG: general-purpose foil strain gauge) manufactured by Kyowa Denki. A strain gauge was attached to the side surface of the central portion of the I-type ferrite core. The absolute value of the rate of change at which the amount of distortion no longer changes after exciting the I core is defined as the saturation magnetostriction amount λs.

For squealing at 100 ° C., the sound pressure level of each E-type core composition was measured in a simple anechoic box using a noise meter (LA-5570) manufactured by Ono Sokki. The data shows the overall value (OA value) after A characteristic conversion. The measurement was performed by installing the core and the sound level meter at a position 10 mm apart.

The strength was measured using a square-shaped sintered body according to the method described in JIS R1601, using a test jig 3p-30 and an I-shaped core having a total length of 40 mm, and the value was defined as a bending strength σb3. .

The saturation magnetic flux density Bs at 100 ° C. was measured on a toroidal core with a DC magnetization characteristic tester (SK-110) manufactured by Metron Giken.

The composition analysis of Si and Ca was performed using a transmission ion microscope (TEM: JEM-2100F) equipped with a focused ion beam (FIB) processing apparatus and an energy dispersive X-ray analyzer (EDS: JED-2300T). . In addition, for TEM observation, particles having an average crystal grain size or larger, which were sliced with an FIB processing apparatus, were used. The average crystal grain size was calculated by observing the cross section of the core center using an optical microscope, measuring the heelwood diameter of all crystals in the 1 mm × 1 mm field of view, and calculating the average. FIG. 5 shows (a) an optical micrograph of a cross section of the ferrite core, (b) a TEM observation image, and a composition analysis location. In the composition analysis, line analysis is performed in the normal direction of the grain boundary at the two-grain grain boundary substantially perpendicular to the thin sample surface, and the point where the Ca concentration becomes maximum is A, and the point which advances from the point A in the 5 nm grain direction is B. The Ca / Si ratio at each point, that is, the values of X and Y were obtained. At that time, the spot size of the electron beam was set to 1 nm or less. In addition, measurement was performed at 10 locations per sample, and values obtained by averaging 8 locations excluding the highest and lowest Ca concentrations at point A were used as X and Y.

The core loss Pcv at 100 ° C. is obtained by using a toroidal-shaped ferrite core and winding 5 turns on the primary side and 5 turns on the secondary side, and at a frequency of 100 kHz and a maximum magnetic flux density of 200 mT. The measurement was performed with an IWATSU BH analyzer (SY-8217).

From the above measurement results, the following can be understood.
“-” In the table indicates that the material is not added.

(Table 1)
A sample was produced under the firing conditions as shown in FIG. If the normal firing conditions and the holding time at 1200 ° C. are short (Comparative Examples 1 and 2), the amount dissolved in the grains is small, the value of X becomes larger than 1.0, and the strength becomes lower than 120 MPa. End up. Even if the holding time at 1200 ° C. is long (Comparative Example 3), the value of X becomes larger than 1.0 and the strength becomes lower than 120 Mpa.

(Table 2)
When the amount of Fe ₂ O ₃ is less than 50.5 mol% (see Comparative Examples 4 and 5), the saturation magnetic flux density Bs at 100 ° C. (hereinafter, omitted at 100 ° C.) becomes smaller than 380 mT. Further, when the amount of Fe ₂ O ₃ exceeds 55.5 mol% (see Comparative Examples 10 and 11), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB.
If the ZnO amount is less than 7.0 mol% (see Comparative Examples 6 and 8), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB. Further, when the ZnO amount exceeds 11.5 mol% (see Comparative Examples 7 and 9), the saturation magnetostriction becomes small, but the saturation magnetic flux density Bs becomes smaller than 380 mT.

(Table 3)
When the value of X is smaller than 0.5 (Comparative Example 12), the core strength is lowered, and even when larger than 1.0 (Comparative Example 13), the core strength is lowered. Further, when the value of Y is smaller than X + 0.05 (Comparative Example 14), the core strength is lowered, and even when larger than X + 0.5 (Comparative Example 15), the core strength is lowered.
Further, if the amount of NiO as a subcomponent is less than 500 ppm (see Comparative Example 16), the saturation magnetostriction becomes large and the OA value becomes larger than 45 dB. Further, when the amount of NiO exceeds 10,000 ppm (see Comparative Example 17), the saturation magnetostriction becomes small, but the saturation magnetic flux density Bs becomes smaller than 380 mT.
When the amount of TiO _{2 as} a subcomponent is less than 100 ppm (see Comparative Example 18), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB. Further, when the amount of TiO ₂ exceeds 6000 ppm (see Comparative Example 19), the magnetostriction becomes small, but the saturation magnetic flux density Bs becomes smaller than 380 mT.
If the amount of CoO as a subcomponent is less than 500 ppm (see Comparative Example 20), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB. Further, when the amount of CoO exceeds 4000 ppm (see Comparative Example 21), the saturation magnetic flux density Bs becomes smaller than 380 mT.
If the amount of the minor component SiO ₂ is small (see Comparative Example 22), the core strength is reduced. Further, even if the amount of SiO ₂ is large (see Comparative Example 23), the core strength is lowered. When the amount of CaCO _{3 as a} subcomponent is small (see Comparative Example 24), the core strength is low, and even when the amount of CaCO ₃ is large (see Comparative Example 25), the core strength is low.

In contrast to this, the amount of Fe ₂ O ₃ is 50.5 to 55.5 mol%, the amount of ZnO is 7.0 to 11.5 mol%, and the amount of NiO is 500 to 10,000 ppm as an accessory component with respect to the main component of the remaining MnO. TiO ₂ content is 100 to 6000 ppm, CoO is 500 to 4000 ppm, Si is 50 to 300 ppm in terms of SiO ₂ , Ca is 200 to 3000 ppm in terms of CaO, 0.5 ≦ X ≦ 1.0, X + 0.05 ≦ Y When satisfying the relationship of ≦ X + 0.50, the saturation magnetostriction at 100 ° C. is 1.5 × 10 ⁻⁶ or less, the OA value is 45 dB or less, the saturation magnetic flux density Bs is 380 mT or more, and the core strength is 120 MPa or more. Can do.

(Table 4)
Other subcomponents are as follows.
Further, by adding _Nb 2 _{O 5} and _Ta 2 _{O 5,} it is possible to reduce the core loss Pcv (see Example 33-39). However, since the core loss is deteriorated if it is added too much, the optimum addition amount ranges are 50 to 750 ppm or less for Nb ₂ O ₅ and 50 to 1500 ppm or less for Ta ₂ O ₅ .
_Further, by adding V 2 _{O 5,} it is possible to reduce the core loss Pcv (see Example 40-42). However, since the core loss is deteriorated if it is added too much, the optimum range of addition amount is 50 to 1000 ppm or less for V ₂ O ₅ .
Moreover, the core loss Pcv can be reduced by adding SnO ₂ (see Examples 43 to 45). However, since the core loss is deteriorated if it is added too much, the optimum range of addition amount is SnO ₂ of 500 to 8000 ppm or less.

As described above, the ferrite core according to the present invention can sufficiently suppress the squeal of the core during driving near 100 ° C., can increase the saturation magnetic flux density, and can increase the core strength.

FIG. 1 is a schematic diagram of a cross section of a sintered body of Mn—Zn ferrite. FIG. 2A is a perspective view showing an E-shaped ferrite core (magnetic core) according to the embodiment. (B) is a perspective view showing a transformer concerning an embodiment. FIG. 3 shows ferrite sintered body measurement positions, which are (a) FIB processing position and (b) EDS analysis position, respectively. FIG. 4 is a switching power supply block diagram. FIG. 5 is a block diagram showing a main part of an automobile provided with a switching power supply device. FIG. 6 is a diagram showing a firing pattern.

1 particle 2 grain boundary 100 cross section of Mn-Zn ferrite 200 ferrite core (magnetic core)
201 (middle leg)
202 (coil)

Claims (4)

50.5～55.5Mol% iron oxide calculated as _Fe 2 _{O 3,} 7.0～11.5Mol% of zinc oxide calculated as ZnO, a MnZn ferrite containing main component balance being manganese oxide, For this main component, Ni is contained in an amount of 500 to 10000 ppm in terms of NiO, Ti is in an amount of 100 to 6000 ppm in terms of TiO ₂ , Co is contained in an amount of 500 to 4000 ppm in terms of CoO, and Si is in an amount of 50 to 300 ppm in terms of SiO _2. A MnZn-based ferrite containing 200 to 3000 ppm of Ca in terms of CaO, wherein the MnZn-based ferrite is a polycrystal having a spinel structure, and the Ca concentration at the point A where the Ca concentration in the grain boundary is maximized. The composition ratio X of Si and the composition ratio Y of Ca and Si at the point B advanced from the point A in the direction of 5 nm in the grain are expressed as Ferrite core, characterized in that the plus.
Relational expressions: 0.5 ≦ X ≦ 1.0, X + 0.05 ≦ Y ≦ X + 0.50
However, X and Y are represented by the following formulas, X and Y = Ca concentration (at%) / Si concentration (at%)
And With respect to the main component, Nb is 50 to 750 ppm in terms of Nb ₂ O ₅ , Ta is 50 to 1500 ppm in terms of Ta ₂ O ₅ , V is 50 to 1000 ppm in terms of V ₂ O ₅ , and Sn is 500 to 500 in terms of SnO _2. 2. The ferrite core according to claim 1, wherein the ferrite core contains 8000 ppm or more. The electronic component comprised using the ferrite core of any one of Claim 1 and Claim 2 A power supply device comprising the electronic component according to claim 3.