JP5510296B2 - Ferrite composition, ferrite core and electronic component - Google Patents

Description

  The present invention relates to a ferrite composition suitable for manufacturing a ferrite core such as a transformer, choke coil, and inductor, a ferrite core composed of the composition, and a coil component in which a winding is wound around the ferrite core. And so on.

  In recent years, various electronic devices such as portable devices have been rapidly reduced in size and weight, and in response to this, there has been a demand for miniaturization, higher efficiency, and higher frequency of electronic components used in electric circuits of various electronic devices. It is growing rapidly.

  For example, a transformer for a liquid crystal backlight is required to have a smaller and thinner shape and a characteristic equal to or higher than that of a conventional one as the display becomes thinner. The characteristics required for the core used for such a transformer include, for example, low power loss in the operating frequency region and operating temperature region, high initial permeability, and high specific resistance. Conventionally, as a core material used in such a transformer, Mn—Zn-based ferrite with low power loss has been used in many cases.

  However, Mn—Zn ferrite has a low specific resistance and cannot be directly wound. Moreover, since the eddy current loss increases as the operating frequency becomes higher, there is a problem that it is not suitable for use in a high frequency region, for example, the MHz region.

  On the other hand, Ni—Zn-based ferrite has higher power loss than the above-mentioned Mn—Zn-based ferrite, but has a high specific resistance and can be directly wound. For this reason, various proposals for reducing the loss of Ni—Zn ferrite have been made.

For example, in Patent Document 1, as a main component, iron oxide is 46.0 to 49.95 mol% in terms of Fe ₂ O ₃ , copper oxide is 2.3 to 12.0 mol% in terms of CuO, and zinc oxide is ZnO. 24.0 to 30.0 mol% in terms of conversion, manganese oxide in an amount of 0.01 to 3.5 mol% in terms of Mn ₂ O ₃ , the balance being composed of nickel oxide, and phosphorus as a subcomponent in terms of P An oxide magnetic material containing 2 to 63 ppm and 0.001 to 0.5 wt% of tungsten oxide in terms of WO ₃ has been proposed.

  However, although the above-described oxide magnetic material improves power loss at 50 kHz, no consideration is given to power loss in a high frequency region, for example, the MHz region, and realization of low loss in the high frequency region is desired. It was. In particular, a portable small electronic device is required to have a ferrite composition having both high initial magnetic permeability and low power loss (MHz region).

JP 2003-321272 A

  The present invention has been made in view of such a situation, and is composed of a ferrite composition having a small power loss Pcv and high initial permeability and specific resistance even in a high frequency region (for example, 1 MHz or more), and the ferrite composition. An object of the present invention is to provide a certain ferrite core and an electronic component having the ferrite core.

In order to achieve the above object, the ferrite composition according to the present invention is composed mainly of 47.1 to 49.95 mol% of iron oxide in terms of Fe ₂ O ₃ and 2.3 to 0.3 in terms of CuO in terms of copper oxide. 10.0 mol%, constituting the oxide of zinc 27.6 to 32.0 mol% in terms of ZnO, manganese oxide containing 0.01 to 2.1 mol% in _Mn 2 _{O 3} in terms of, in the balance nickel oxide As a subcomponent, phosphorus is ₂ to 63 ppm in terms of P, zirconium oxide is 43 to 4530 ppm in terms of ZrO ₂ , and tungsten oxide is 0.01 to 0 in terms of WO ₃ with respect to 100 parts by weight of the main component. .25 parts by weight, and molybdenum oxide is contained in an amount of 0.01 to 0.15 parts by weight in terms of MoO ₃ .

Alternatively, in the ferrite composition according to the present invention, the main component is 47.1 to 49.95 mol% iron oxide in terms of Fe ₂ O ₃ , and 2.3 to 10.0 mol% in terms of copper oxide in terms of CuO, Zinc oxide is contained in an amount of 27.6 to 32.0 mol% in terms of ZnO, and the balance is composed of nickel oxide. 63 ppm, 43 to 4530 ppm of zirconium oxide in terms of ZrO ₂ , 0.01 to 0.25 parts by weight of tungsten oxide in terms of WO ₃ , and 0.01 to 0.15 parts by weight of molybdenum oxide in terms of MoO ₃ Features.

  By keeping the content of the oxide constituting the main component within the above range and further containing phosphorus, zirconium oxide, tungsten oxide and molybdenum oxide as subcomponents within the above range, the initial permeability μi and specific resistance can be kept high. However, power loss (core loss: Pcv) can be reduced even in a high frequency region (for example, 1 MHz or more). In particular, μi can be preferably 1100 or more, more preferably 1200 or more. Furthermore, μi / Pcv can be preferably 0.70 or more, and more preferably 0.72 or more.

  The reason why such an effect is obtained is not necessarily clear, but it is considered that the combined effect obtained by coexisting phosphorus, zirconium oxide, tungsten oxide, and molybdenum oxide in the above-mentioned range greatly influences.

When manganese oxide is contained in the main component, the total content of the iron oxide and the manganese oxide is preferably 50.1 mol% or less in terms of Fe ₂ O ₃ and Mn ₂ O _3. is there.

  By making the total content of the iron oxide and the manganese oxide in the above range, the above-described effects can be further enhanced.

  The ferrite core according to the present invention is composed of the ferrite composition described in any of the above, and is used in a frequency region of 1 MHz or more.

  An electronic component according to the present invention is an electronic component having the above ferrite core.

  Although it does not restrict | limit especially as an electronic component which concerns on this invention, A coil component, a transformer component, a magnetic head component, etc. are mentioned. Since the electronic component according to the present invention has a high inductance and a Curie point, it is suitable as a coil component such as an inductor or a choke coil. It is also suitable for transformer parts such as power transformers for switching and inverters.

  The upper limit of the frequency to be used is not particularly limited, but is about 20 MHz in consideration of the usage frequency of the device in which the ferrite core or the electronic component according to the present invention is used.

  According to the present invention, it is possible to obtain a ferrite composition in which power loss (core loss) is reduced even in a high frequency region (for example, 1 MHz or more) while maintaining high initial magnetic permeability and specific resistance.

  By applying such a ferrite composition to a ferrite core and an electronic component, it is possible to realize downsizing, high efficiency, and high frequency.

FIG. 1 shows a ferrite core for a transformer according to an embodiment of the present invention.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  In addition to the toroidal type shown in FIG. 1, the ferrite core for transformer according to the present embodiment includes FT type, ET type, EI type, UU type, EE type, EER type, UI type, drum type, pot type, cup Examples include molds. A desired transformer is obtained by winding a predetermined number of windings around the transformer ferrite core.

  The ferrite core for transformers according to this embodiment is composed of the ferrite composition according to this embodiment.

  The ferrite composition according to the present embodiment is a Ni—Cu—Zn based ferrite and contains iron oxide, copper oxide, zinc oxide and nickel oxide as main components. Moreover, you may contain a manganese oxide as needed.

In the main component 100 mol%, the content of iron oxide, calculated as _Fe 2 _{O 3,} 47.1 to 49.95 mol%, preferably 48.5 to 49.7 mol%, more preferably 49.0～ 49.5 mol%. If the content of iron oxide is too small, the initial permeability tends to decrease and the power loss (core loss) tends to increase. When the amount is too large, the specific resistance decreases and the power loss tends to increase.

  In 100 mol% of the main component, the content of copper oxide is 2.3 to 10.0 mol%, preferably 2.3 to 5.6 mol%, more preferably 4.0 to 5.6 in terms of CuO. Mol%. When there is too little content of copper oxide, sinterability will fall and as a result, it exists in the tendency for electric power loss to increase. Even if the amount is too large, power loss tends to increase.

  In 100 mol% of the main component, the content of zinc oxide is 27.6-32.0 mol%, preferably 29.0-31.0 mol%, more preferably 29.0-30.0 in terms of ZnO. Mol%. When the content of zinc oxide is too small, the initial permeability tends to decrease. If the amount is too large, the Curie point tends to decrease and the power loss tends to increase.

  The remainder of the main component may be composed only of nickel oxide, or may be composed of nickel oxide and manganese oxide.

The remainder of the main component, if the manganese oxide is contained, in the main component 100 mol%, the content of manganese oxide is a _Mn 2 _{O 3} in terms of, preferably 0.01 to 2.1 mol%, more Preferably it is 0.01-1.6 mol%, More preferably, it is 0.01-1.1 mol%. When the amount is too large, the specific resistance decreases and the power loss tends to increase.

  Usually, manganese is contained as an inevitable impurity in the form of manganese oxide in iron oxide, but manganese oxide may be contained within the above range.

When manganese oxide is contained in the main component, the total content of iron oxide and manganese oxide (Fe ₂ O ₃ + Mn ₂ O ₃ ) is calculated in terms of Fe ₂ O ₃ and Mn ₂ O ₃ . It is preferable that it is 50.1 mol% or less. By setting the upper limit of the total content of iron oxide and manganese oxide within the above range, good characteristics can be obtained.

  The ferrite composition according to the present embodiment contains phosphorus, zirconium oxide, tungsten oxide, and molybdenum oxide as subcomponents in addition to the above main components.

  The phosphorus content is 2 to 63 ppm in terms of P with respect to 100 parts by weight of the main component. When there is too little content of phosphorus, sinterability will fall and as a result, it exists in the tendency for electric power loss to increase. Even if the amount is too large, power loss tends to increase.

The content of zirconium oxide is 43 to 4530 ppm, preferably 43 to 3210 ppm, more preferably 43 to 1530 ppm in terms of ZrO _{2 with} respect to 100 parts by weight of the main component. If the zirconium oxide content is too low or too high, the power loss tends to increase.

The content of tungsten oxide is 0.01 to 0.25 parts by weight, preferably 0.1 to 0.25 parts by weight, more preferably 0.1, in terms of WO _{3 with} respect to 100 parts by weight of the main component. -0.22 parts by weight. If the content is too small, the power loss increases, and if the content increases, the power loss decreases, but the initial permeability μi tends to decrease.

The content of molybdenum oxide is 0.01 to 0.15 parts by weight, preferably 0.03 to 0.15 parts by weight, more preferably 0.03 in terms of MoO _{3 with} respect to 100 parts by weight of the main component. ~ 0.10 parts by weight. If the content is too small, the power loss increases. If the content increases, the power loss decreases, but μi / Pcv, which indicates the performance index of the ferrite core at 1 MHz, tends to decrease. Molybdenum oxide can reduce power loss even when added in a small amount. Addition of molybdenum oxide also has secondary effects such as improving the strength of the molded body and effectively preventing cracks and chips.

  In the ferrite composition according to the present embodiment, in addition to the composition range of the main component being controlled to the above range, the above-described phosphorus, zirconium oxide, tungsten oxide, and molybdenum oxide are contained as subcomponents. . As a result, it is possible to reduce power loss in a high frequency region (for example, 1 MHz or more) while maintaining good initial permeability and specific resistance.

  In addition, when phosphorus, zirconium oxide, tungsten oxide, or molybdenum oxide is contained alone, the above effect cannot be obtained sufficiently. That is, the above effect is considered to be a composite effect obtained for the first time when a specific amount of phosphorus, zirconium oxide, tungsten oxide, and molybdenum oxide is simultaneously contained. In particular, the initial permeability μi and μi / Pcv indicating the figure of merit of the ferrite core at 1 MHz can be improved.

  In addition, the ferrite composition according to this embodiment may include oxides of inevitable impurity elements other than manganese.

  Specifically, B, C, Si, S, Cl, As, Se, Br, Te, I, Li, Na, Mg, Al, K, Ca, Ga, Ge, Sr, Cd, In, Sn, Examples include typical metal elements such as Sb, Ba, Pb, and Bi, and transition metal elements such as Sc, Ti, V, Cr, Co, Y, Nb, Mo, Pd, Ag, Hf, and Ta.

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

  First, starting materials (raw materials of main components and raw materials of subcomponents) are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer. It is preferable to use a starting material having an average particle size of 0.1 to 3 μm.

As raw materials of the main component, iron oxide (α-Fe ₂ O ₃ ), copper oxide (CuO), zinc oxide (ZnO), nickel oxide (NiO), manganese oxide (Mn ₂ O ₃ ) as required, or A composite oxide or the like can be used. In addition, various compounds that become oxides or composite oxides by firing can be used. Examples of the oxide that becomes the above-mentioned oxide upon firing include simple metals, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds, and the like.

Phosphorus (P), zirconium oxide (ZrO ₂ ), tungsten oxide (WO ₃ ), and molybdenum oxide (MoO ₃ ) can be used as a raw material for the accessory component. Phosphorus is preferably used in the form of phosphoric acid (P ₂ O ₅ ). Zirconium oxide, tungsten oxide, and molybdenum oxide may be the same as those of the main component material.

  Next, the raw material mixture is calcined to obtain a calcined material. Calcining causes thermal decomposition of raw materials, homogenization of ingredients, formation of ferrite, disappearance of ultrafine powder due to sintering and grain growth to an appropriate particle size, and converts the raw material mixture into a form suitable for the subsequent process. Done for. Such calcination is preferably performed at a temperature of 800 to 1100 ° C. for about 1 to 3 hours. The calcination may be performed in the air (air), or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. The mixing of the main component raw material and the subcomponent raw material may be performed before calcining or after calcining.

  Next, the calcined material is pulverized to obtain a pulverized material. The pulverization is performed in order to break down the coagulation of the calcined material to obtain a powder having appropriate sinterability. When the calcined material forms a large lump, wet pulverization is performed using a ball mill or an attritor after coarse pulverization. The wet pulverization is performed until the average particle diameter of the calcined material is preferably about 1 to 2 μm.

  Next, the pulverized material is granulated (granular) to obtain a granulated product. The granulation is performed in order to convert the pulverized material into aggregated particles having an appropriate size and convert it into a form suitable for molding. Examples of such a granulation method include a pressure granulation method and a spray drying method. The spray drying method is a method in which a commonly used binder such as polyvinyl alcohol is added to the pulverized material, and then atomized in a spray dryer and dried at a low temperature.

  Next, the granulated product is molded into a predetermined shape to obtain a molded body. Examples of the molding of the granulated product include dry molding, wet molding, and extrusion molding. The dry molding method is a molding method in which a granulated product is filled in a mold and compressed and pressed (pressed). The shape of the molded body is not particularly limited, and may be appropriately determined according to the application. In the present embodiment, the shape is a toroidal shape.

  Next, the compact is fired to obtain a sintered body (the ferrite composition of the present embodiment). This firing is performed in order to obtain a dense sintered body by causing sintering in which the powder adheres at a temperature below the melting point between the powder particles of the molded body containing many voids. Such firing is preferably performed at a temperature of 900 to 1300 ° C. for usually 2 to 5 hours. The main calcination may be performed in the atmosphere (air) or in an atmosphere having a higher oxygen partial pressure than in the atmosphere.

  Through such steps, the ferrite composition according to the present embodiment is manufactured.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. .

  For example, in the above-described embodiment, in order to obtain a toroidal shape, the shape is formed before the main baking, but may be formed (processed) after the main baking.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

First, Fe ₂ O ₃ , NiO, CuO, ZnO, and Mn ₂ O ₃ were prepared as main component materials. P ₂ O ₅ and ZrO _2, WO ₃ and MoO ₃ were prepared as the raw materials for the accessory components. The average particle size of the starting material was 0.1 to 3 μm.

  Next, the prepared raw material powders of the main component and subcomponent were weighed and then wet mixed by a ball mill for 5 hours to obtain a raw material mixture.

  Next, the obtained raw material mixture was calcined in air at 900 ° C. for 2 hours to obtain a calcined material, and then wet pulverized with a ball mill for 20 hours to obtain a pulverized material.

  Next, after drying this pulverized material, 1.0 part by weight of polyvinyl alcohol as a binder was added to 100 parts by weight of the pulverized material, granulated, and sized with a 20 mesh sieve to obtain granules. The granules are pressure-molded at a pressure of 100 kPa to form a toroidal shaped body (dimension = outer diameter 18 mm × inner diameter 10 mm × height 5 mm) and a disk shape (dimension = diameter 25 mm × thickness 5 mm). Got.

  Next, each of these molded bodies was fired in air at 1000 to 1250 ° C. for 2 hours to obtain a toroidal core sample and a disk core sample as a sintered body. The obtained sample was subjected to fluorescent X-ray analysis to measure the composition of the ferrite core. The results are shown in Tables 1-3. The phosphorus (P) content was measured by absorptiometry. Furthermore, the following characteristics evaluation was performed with respect to the sample.

Power loss (Pcv)
The primary and secondary windings were wound five times on the obtained toroidal core sample, and the power loss Pcv at 1 MHz, 50 mT, 23 ° C. and 50 kHz, 150 mT, 140 ° C. was measured (unit: kW / m ³ ). The measurement was performed using a BH analyzer (SY-8232 manufactured by Iwasaki Tsushinki Co., Ltd.). The Pcv at 1 MHz was set to 2000 kW / m ³ or less. The results are shown in Tables 1-3.

  In addition, since the ferrite core and electronic components whose use frequency is 1 MHz or more are applied to, for example, a cellular phone, in this example, Pcv was measured in a temperature region in which such a device is normally used.

Initial permeability (μi)
A copper wire was wound around the obtained toroidal core sample for 10 turns, and an initial magnetic permeability μi was measured using an LCR meter (Hewlett Packard 4284A). The measurement conditions were a measurement frequency of 100 kHz, a measurement temperature of 23 ° C., and a measurement level of 0.4 A / m. Μi at 100 kHz was 1100 or more. The results are shown in Tables 1-3.

Specific resistance (ρ)
An In—Ga electrode was applied to both surfaces of the obtained disk core sample, a direct current resistance value was measured, and a specific resistance ρ was determined (unit: Ωm). The measurement was performed using an IR meter (SUPER MEGOHMMETER MODEL SM-5E manufactured by TOA Electronics). ρ was determined to be 10 ⁸ Ωm or more. The results are shown in Tables 1-3.

  In Tables 1 to 3, μi / Pcv indicating the performance index of the ferrite core at 1 MHz is also shown. μi / Pcv was determined to be 0.70 or more.

From Table 1, when P and ZrO ₂ which are subcomponents, WO ₃ and MoO ₃ are contained at the same time and the contents are within the scope of the present invention (Examples 1 to 18), power is supplied in a high frequency region (1 MHz). It was confirmed that the loss (Pcv) was good and high initial permeability (μi) and specific resistance tended to be obtained. In particular, when WO ₃ and MoO ₃ are contained at the same time and the content is within the scope of the present invention, the initial magnetic permeability (μi) can be 1100 or more, and further the ferrite core at 1 MHz. It was confirmed that the figure of merit (μi / Pcv) can be 0.70 or more. Therefore, it was confirmed that a high figure of merit was obtained.

On the other hand, when one or more of P or ZrO ₂ or WO ₃ or MoO ₃ is not contained (Comparative Examples 1, 3, 5, 7, 13 and 20-23), or P or ZrO ₂ or WO _When the content of P or ZrO ₂ out of the scope of the present invention was ₃ or MoO ₃ (Comparative Examples 6 and 8), the tendency of power loss at 1 MHz to deteriorate was confirmed.

Moreover, P, or one of ZrO ₂ or WO ₃ or MoO _3, in the case where the content of MoO ₃ is out of the range of the present invention (Comparative Example 2), the performance index of the ferrite core in the 1 MHz (.mu.i / Pcv ) Was confirmed to deteriorate.

In addition, among P, ZrO _2, WO _{3, and} MoO ₃ , when the content of WO ₃ is out of the scope of the present invention (Comparative Example 4), a tendency for the initial permeability μi to decrease is confirmed. It was.

  Moreover, from Table 2, when the content of CuO is outside the range of the present invention (Comparative Examples 9 and 10), it was confirmed that the power loss at 1 MHz tends to deteriorate. In addition, when the ZnO content is too small (Comparative Example 11), the initial magnetic permeability is decreased, and when the ZnO content is too large (Comparative Example 12), the power loss at 1 MHz tends to deteriorate. It was done.

Further, from Table 3, when the contents of Fe ₂ O ₃ and Mn ₂ O ₃ are outside the scope of the present invention (Comparative Examples 14 to 19), the power loss at 1 MHz deteriorates and the initial transmission It was confirmed that at least one of magnetic susceptibility and specific resistance deteriorated.

Claims (5)

The main components are iron oxide 47.1 to 49.95 mol% in terms of Fe ₂ O ₃ , copper oxide 2.3 to 10.0 mol% in terms of CuO, and zinc oxide 27.6 to 32 in terms of ZnO. 2.0 mol%, manganese oxide containing 0.01 to 2.1 mol% in _Mn 2 _{O 3} in terms of the balance is constituted by nickel oxide, with respect to the main component as 100 parts by weight, as a sub-component In addition, phosphorus is ₂ to 63 ppm in terms of P, zirconium oxide is 43 to 4530 ppm in terms of ZrO ₂ , tungsten oxide is 0.01 to 0.25 parts by weight in terms of WO ₃ , and molybdenum oxide is 0.01 to 0 in terms of MoO _3. . A ferrite composition containing 15 parts by weight. The main components are iron oxide 47.1 to 49.95 mol% in terms of Fe ₂ O ₃ , copper oxide 2.3 to 10.0 mol% in terms of CuO, and zinc oxide 27.6 to 32 in terms of ZnO. 0.0 mol%, and the balance is composed of nickel oxide, with respect to 100 parts by weight of the main component, as subcomponents, phosphorus is ₂ to 63 ppm in terms of P and zirconium oxide is 43 to 43 in terms of ZrO _2. A ferrite composition comprising 4530 ppm, tungsten oxide in an amount of 0.01 to 0.25 parts by weight in terms of WO ₃ , and molybdenum oxide in an amount of 0.01 to 0.15 parts in terms of MoO ₃ . _2. The ferrite composition according to claim 1, wherein the total content of the iron oxide and the manganese oxide is 50.1 mol% or less in terms of Fe ₂ O ₃ and Mn ₂ O ₃ .   A ferrite core made of the ferrite composition according to any one of claims 1 to 3 and used in a frequency region of 1 MHz or more.   An electronic component having the ferrite core according to claim 4.

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