JP2008162847A - Magnetic oxide material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high temperature range, to reduce the fluctuation of the initial magnetic permeability, to reduce the core loss to a low value, to ensure sufficient magnetic properties even at a high temperature of 100 ° C. or higher, to obtain a high surface resistance, and to achieve a high voltage It is added the a main component to provide an oxide magnetic material core can preferably be applied to materials such applications _Fe 2 _{O 3 47.2~49.2} mol%, ZnO is 25 to 30 mol%, CuO Is 3 to 10 mol%, MnO is 0.2 to 2.8 mol%, the balance is NiO, and the composition is 49.4 to 50.0 mol% in terms of (Fe ₂ O ₃ + MnO). The sintered body thus obtained has the characteristics of the mixed materials interacting with each other. The material characteristics are such that the core loss at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, and a temperature of 60 ° C. is 200 kW / m ³ or less. The temperature at which the loss reaches a minimum value is 100 ° C. or higher. Since the Fe component amount is 49.2 mol% or less, the surface resistance can be as high as 10 [GΩ] or more.
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Description

  The present invention relates to an MnNiCuZn-based oxide magnetic material, and more specifically, an improvement in temperature dependency in a core loss material that is applied to a core material such as an inverter transformer of a liquid crystal backlight. About.

  As oxide magnetic materials used for core materials such as transformers and coils, Mn—Zn ferrite and Ni—Zn ferrite are well known.

  Mn—Zn-based ferrite is favorably used as a core material for switching power supplies and the like because of its low core loss and high saturation magnetic flux density. However, Mn—Zn ferrite cannot be directly wound because of its low specific resistance, and has a drawback that it is difficult to reduce the size because it has a configuration in which a bobbin or the like is interposed for insulation.

Ni-Zn based ferrite can be directly wound around the core because of its remarkably high specific resistance, and is therefore attractive for downsizing. However, since Ni-Zn ferrite has a drawback of large core loss, an improvement measure is required. As countermeasure techniques, there are many proposals as seen in, for example, Patent Documents 1 to 6, and the core loss is adjusted by appropriately including Mn, Cu, etc. in addition to Fe, Ni, Zn as a composition. To improve.
Japanese Laid-Open Patent Publication No. 11-211981 JP 2002-198212 A JP 2002-289421 A JP 2004-107158 A Japanese Patent No. 2551009 Japanese Patent No. 3487552

  By the way, in applications such as inverter transformers for liquid crystal backlights, high-frequency and high-voltage driving has been adopted due to demands for miniaturization and high efficiency, and a high voltage of, for example, 1000 V or more is applied to the core material. Yes. For this reason, the core material is required to have high insulation characteristics, temperature characteristics are important because heat generation is large, core loss is required to be small even at high temperatures, and characteristics in which fluctuations in initial permeability are small after reaching a high temperature range are required.

Further, in applications where high voltage is applied, there is a problem of causing discharge due to a short circuit on the surface of the core material. In other words, Ni-Zn ferrite has a characteristic of high specific resistance, but in the firing, elements such as Zn and Cu are scattered by evaporation or the like, and the composition in the surface region slightly changes, and relatively The amount of Fe will increase. In a situation where the amount of Fe (Fe ₂ O ₃ ) exceeds 50 mol%, a phenomenon in which the resistance value is remarkably reduced due to the electron transfer when changing from divalent to trivalent occurs, and the electric resistance is extremely reduced. The surface film layer in which the electric resistance is reduced has a thickness of several tens to several hundreds of μm, and is a small region from the whole core material. However, when a high voltage of 1000 V or more is applied, a short circuit occurs.

  The object of the present invention is to solve the above-mentioned problems. The object of the present invention is to reach a high temperature range to reduce the fluctuation of the initial magnetic permeability, to reduce the core loss to a low value, and to achieve sufficient magnetism even at a high temperature of 100 ° C. or higher. An object of the present invention is to provide an oxide magnetic material that can secure characteristics, obtain a high surface resistance, and can be preferably applied to a core material or the like for applications where high voltage is applied.

In order to achieve the above-described object, the oxide magnetic material according to the present invention is an MnNiCuZn-based oxide magnetic material, the main component of which is 47.2 to 49.ferric oxide (Fe ₂ O ₃ ). 2 mol%,
Zinc oxide (ZnO) is 25-30 mol%,
3-10 mol% copper oxide (CuO),
Manganese oxide (MnO) is 0.2 to 2.8 mol% and the balance is nickel oxide (NiO),
Ferric oxide and manganese oxide in terms of Fe ₂ O ₃ + MnO 49.4 mol% ≦ (Fe ₂ O ₃ + MnO) ≦ 50.0 mol%
It is set as the composition to contain.

The sintered body having the above composition has an average crystal particle diameter of 8 to 20 μm, a core loss of 200 kW / m ³ or less at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, and a temperature of 600 ° C. The temperature is 100 ° C. or higher, and the relative temperature coefficient (αμir) of the initial permeability is 20 × 10 ⁻⁶ or lower in the temperature range of 25 ° C. to 130 ° C.

  As described above, the temperature-core loss characteristic at which the minimum value is 100 ° C. or more has a negative convex temperature characteristic, and the temperature rises from room temperature (or lower) (up to the minimum temperature). ) Has a characteristic that the loss is reduced, and the core loss is reduced when heat is generated due to use.

In the present invention, by setting Fe ₂ O ₃ , ZnO, CuO, MnO, NiO and (Fe ₂ O ₃ + MnO) to the above-described predetermined mixing ratio, the obtained sintered body has a core loss at a high temperature. It becomes smaller, and the fluctuation of the initial permeability becomes smaller in a wide temperature range. The composition according to the present invention described above is the result of an experiment, and the material characteristics of the sintered body are as follows: the core loss at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, and a temperature of 600 ° C. is 200 kW / m ³ or less. Was 100 ° C. or higher, and the relative temperature coefficient (αμir) of the initial permeability was 20 × 10 ⁻⁶ or lower in the temperature range of 25 ° C. to 130 ° C.

  In this case, since the temperature at which the core loss reaches a minimum value is 100 ° C. or more, there is a margin for the core loss that deteriorates with heat generation, and it can be said that it is preferable as a core material for a switching power supply that drives at high frequency and high voltage. .

In addition, since the Fe ₂ O ₃ content is 49.2 mol% or less, even if Cu or Zn evaporates or moves on the surface during firing and the composition changes in the surface region, the Fe ₂ O content in the surface region is reduced. _The situation in which ₃ exceeds 50 mol% is less likely to occur, and a high surface resistance can be obtained.

In terms of Fe ₂ O ₃ + MnO, 49.4 mol% ≦ (Fe ₂ O ₃ + MnO) ≦ 50.0 mol%, that is, near 50 mol%, the loss is small, and the minimum value can be 100 ° C. or more. .

The oxide magnetic material according to the present invention, the main component is _Fe 2 _{O 3} is from 47.2 to 49.2 mol%, ZnO is 25 to 30 mol%, CuO is from 3 to 10 mol%, 0.2 is MnO Since the composition is 2.8 mol%, the balance is NiO, and 49.4 to 50.0 mol% in terms of (Fe ₂ O ₃ + MnO), the sintered body (oxide magnetic material) is The characteristics of the mixed materials interact with each other.

As for the material properties of the sintered body, the core loss at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, and a temperature of 60 ° C. is 200 kW / m ³ or less, and the temperature at which the core loss shows a minimum value is 100 ° C. or more. That is, in the sintered body according to the present invention, the fluctuation of the initial permeability can be reduced by reaching the high temperature range, the core loss can be lowered, and sufficient magnetic properties are ensured even at a high temperature of 100 ° C. or higher. can do.

Also, since the blending of _Fe 2 _{O 3} is less than 49.2 mol%, a situation in which the surface area is _Fe 2 _{O 3} exceeds a relatively 50 mol% hardly caused, can be obtained a high surface resistance. As shown in the examples, the surface resistance can be sufficiently high above 10 [GΩ], and therefore, even when a high voltage of 1000 V or higher is applied, a short circuit and discharge can be prevented, and a core for applications where a high voltage is applied. It can be preferably applied to materials and the like.

  Hereinafter, preferred embodiments of the present invention will be described.

The oxide magnetic material according to the present invention is composed mainly of ferric oxide (Fe2O3), zinc oxide (ZnO), copper oxide (CuO), nickel oxide (NiO), etc., and has a composition of so-called MnNiCuZn ferrite. Yes. Specifically, the main component is 47.2 to 49.2 mol% of ferric oxide (Fe ₂ O ₃ ),
Zinc oxide (ZnO) is 25-30 mol%,
3-10 mol% copper oxide (CuO),
Manganese oxide (MnO) is 0.2 to 2.8 mol% and the balance is nickel oxide (NiO),
Ferric oxide and manganese oxide in terms of Fe ₂ O ₃ + MnO 49.4 mol% ≦ (Fe ₂ O ₃ + MnO) ≦ 50.0 mol%
It is set as the composition to contain.

  For production, first, a predetermined amount of each of the above-mentioned raw material components is weighed and wet mixed. For example, a mixed powder is manufactured by pulverizing with a ball mill, dried, crushed, and then calcined. In the calcining, for example, an electric furnace is used and the temperature is set to about 850 ° C. in the atmosphere.

  Since the grains grow when calcined, it is wet-pulverized again by an atomizer or the like. This is dried and crushed. Polyvinyl alcohol (PVA) is added to the powder to form a slurry, which is granulated by spray drying to obtain a powder having a predetermined particle diameter.

  Next, pressure for molding is applied to the granulated powder to form, for example, a ring shape, and then firing is performed in a gas furnace or the like. Firing is performed at a temperature of 1000 to 1200 ° C. in the atmosphere, for example, and a sintered body is produced by firing for a predetermined time (for example, 2 hours). The obtained sintered body is subjected to finish processing such as barrel polishing to obtain an oxide magnetic material having a predetermined shape and size.

  This sintered body is manufactured to have an average crystal particle diameter of 8 to 20 μm, which is realized by optimizing the firing conditions.

  When ZnO is blended in an amount of 25 mol% or less, the core loss increases, and when it exceeds 30 mol, the Curie temperature (Tc) decreases, and sufficient safety cannot be secured during heat generation. Therefore, the ZnO content is 25 to 30 mol%, and in this range, the core loss can be reduced and the Curie temperature can be increased.

  When the CuO content is 3 mol% or less, sintering does not proceed, and it is necessary to perform firing at a high temperature, which is not practical. If it is 10 mol% or more, the core loss is deteriorated. Therefore, the CuO content is 3 to 10 mol%, and firing can be appropriately performed at a relatively low temperature, a predetermined sintered density can be obtained, and the core loss can be reduced.

The composition of Fe ₂ O ₃ tends to increase the relative temperature coefficient of the initial magnetic permeability as it increases. Further, the _Fe 2 _{O 3} or _{(Fe 2 O 3 + MnO)} , the amount is reduced tended to core loss increases, the temperature indicating the minimum core loss becomes 100 ° C. or less. Therefore, the Fe ₂ O ₃ content is 49.2 mol% or less, and the relationship with manganese oxide is set to 50.0 mol% or less in terms of Fe ₂ O ₃ + MnO.

By setting the blending of Fe ₂ O ₃ to 49.2 mol% or less, even if Cu or Zn evaporates or moves on the surface during firing and the composition changes in the surface region, the Fe ₂ O _{3 is in the} surface region. Is relatively difficult to occur, and a high surface resistance can be obtained. Therefore, a short circuit can be prevented in applications where high voltage is applied.

Then, from the result of measurement of the magnetic characteristics of the sample which will be described later, and optimally, the formulation of _Fe 2 _{O 3} is preferably in the range of 47.2 to 49.2 _{mol%, (Fe 2 O 3 +} MnO) is 49.4 It is made into the range of -50.0 mol%, and the compounding of MnO is 0.2-2.8 mol%.

  The temperature at which the core loss shows the minimum value is determined to some extent by the composition of the main component, but since the core loss largely depends on the fine crystal structure, the crystal structure (crystal grains and their grain boundaries) is in the manufacturing process. Precise control is important. That is, the sintered body is a polycrystalline body, and it can be said that the variation in the composition of each crystal particle is one of the factors that deteriorate the core loss. In the present invention, the average crystal particle diameter of the sintered body is 8 to 20 μm. Therefore, the particle size distribution is concentrated in a narrow range, and as a result, the material characteristics of the entire core can be concentrated and uniformed in a predetermined distribution, and the core loss can be improved.

The sintered body having the composition described above has material properties of a core loss of 200 kW / m ³ or less at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, and a temperature of 60 ° C., and a temperature at which the core loss shows a minimum value is 100 ° C. or more. The relative temperature coefficient (αμir) of the initial magnetic permeability is 20 × 10 ⁻⁶ or less in the temperature range of 25 ° C. to 130 ° C. This material property is optimal as a core material for applications where a high voltage is applied, and it can be said that application to a core material such as an inverter transformer of a liquid crystal backlight is preferable.

  Samples were manufactured according to the manufacturing procedure described above. That is, in order to demonstrate the effect of the present invention, a plurality of samples were manufactured with different compositions, and the core loss, the relative temperature coefficient of initial permeability, and the surface resistance were measured for each sample.

As shown in Table 1, the samples were 32 samples with different compositions, and the outer shape was a ring shape. The composition of the main component is changed in the range of 43.22 to 49.70 mol% for ferric oxide (Fe ₂ O ₃ ), and in the range of 27.50 to 29.90 mol% for zinc oxide. The copper oxide (CuO) is changed in the range of 4.92 to 6.10 mol%, the manganese oxide (MnO) is changed in the range of 0.00 to 8.04 mol%, and the remaining nickel oxide (NiO) is changed in the range of 15.63 to 17.00 mol%, and ferric oxide and manganese oxide are changed in the range of 47.0 to 51.26 mol% in terms of Fe ₂ O ₃ + MnO. And 32 samples were prepared from these combinations.

  Moreover, the sintered compact by these each composition was manufactured so that an average crystal particle diameter might be set to 8-20 micrometers, and this was implement | achieved by optimization of baking conditions.

Each sample shown in the table is included in the present invention (the invention according to claim 1). And the Example in a table | surface respond | corresponds to the invention which concerns on Claim 3, and a comparative example does not satisfy the requirements of the invention which concerns on Claim 3 although it respond | corresponds to this invention.

  The BH analyzer was used to measure the core loss, and the measurement was performed in the range from room temperature 25 ° C. to high temperature 140 ° C. at a frequency of 60 kHz and a saturation magnetic flux density of 100 mT. An impedance analyzer was used to measure the relative temperature coefficient of the initial permeability, and the temperature characteristics of the initial permeability were measured at a frequency of 100 kHz and a current of 0.01 A. The surface resistance was measured using an ohmmeter under the conditions of a distance between electrodes of 20 mm and a voltage of 500V.

The core loss, relative temperature coefficient of initial permeability, and surface resistance of each sample were measured. As is apparent from the measurement results shown in Table 1, the characteristics of each raw material component interacted with each other to produce suitable magnetic properties. In order to achieve this, it is preferable that the composition of each component is within a predetermined range according to the present invention. That is, the main component is 47.2 to 49.2 mol% of ferric oxide (Fe ₂ O ₃ ),
Zinc oxide (ZnO) is 25 to 30 mol%,
3-10 mol% copper oxide (CuO),
Manganese oxide (MnO) is 0.2 to 2.8 mol% and the balance is nickel oxide (NiO),
Ferric oxide and manganese oxide in terms of Fe ₂ O ₃ + MnO 49.4 mol% ≦ (Fe ₂ O ₃ + MnO) ≦ 50.0 mol%
It was confirmed that the composition having the composition can obtain a surface resistance sufficiently high to 10 [GΩ] or more. Therefore, even when a high voltage of 1000 V or more is applied, short circuit and discharge can be prevented, and it can be preferably applied to a core material or the like for applications where a high voltage is applied.

Furthermore, in Examples 1 to 6 shown in Table 1, the core loss at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, and a temperature of 60 ° C. is 200 kW / m ³ or less, and the temperature at which the core loss shows a minimum value is 100 ° C. or more. It was confirmed that a material characteristic having a relative temperature coefficient (αμir) of initial permeability of 20 × 10 ⁻⁶ or less was obtained in a temperature range of 25 ° C. to 130 ° C.

Claims (3)

MnNiCuZn-based oxide magnetic material,
The main component is 47.2 to 49.2 mol% of ferric oxide (Fe ₂ O ₃ ),
Zinc oxide (ZnO) is 25-30 mol%,
3-10 mol% copper oxide (CuO),
Manganese oxide (MnO) is 0.2 to 2.8 mol%,
The balance is nickel oxide (NiO),
The ferric oxide and the manganese oxide in terms of Fe ₂ O ₃ + MnO are 49.4 mol% ≦ (Fe ₂ O ₃ + MnO) ≦ 50.0 mol%.
An oxide magnetic material having a composition containing the oxide magnetic material.   2. The oxide magnetic material according to claim 1, wherein the sintered body having the composition has an average crystal particle diameter of 8 to 20 μm. The sintered body having the above composition has a core loss at a frequency of 60 kHz, a saturation magnetic flux density of 100 mT, a temperature of 60 ° C. of 200 kW / m ³ or less, a temperature at which the core loss shows a minimum value is 100 ° C. or more, and an initial permeability. 3. The oxide magnetic material according to claim 1, wherein a relative temperature coefficient (α μir) is 20 × 10 ⁻⁶ or less in a temperature range of 25 ° C. to 130 ° C. 3.