JP2012240897A - Ferrite composition and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic component where both reduction in electric power loss and high saturated magnetic flux density are attained under the environment of a high frequency and low magnetic field in which the in-use temperature or environmental temperature is close to room temperature or the air temperature, more specifically it is in the range of 0-50°C, and to provide a ferrite composition suitable for the electronic component.SOLUTION: The ferrite composition is characterized in that: a main ingredient contains 63.3-65.5 mol% of an iron oxide in terms of FeOand 11.6-15.8 mol% of a zinc oxide in terms of ZnO; the remainder is constituted of a manganese oxide; a sub ingredient contains 60-250 ppm of a silicon oxide in terms of SiOand 360-1,000 ppm of calcium oxide in terms of CaO based on 100 wt.% of the main ingredient; and the content of Pb is 7 ppm or less and the content of Cd is 7 ppm or less based on 100 wt.% of the main ingredient.

Description

  The present invention relates to a ferrite composition and an electronic component, and the ambient temperature or use temperature is near room temperature or near ambient temperature. More specifically, the use temperature is in the range of 0 to 50 ° C., and the environment is in a high frequency and low magnetic field environment. The present invention relates to an electronic component capable of achieving both a reduction in power loss and a high saturation magnetic flux density, and a ferrite composition suitable for the electronic component.

  In recent years, various electronic devices such as portable devices have rapidly become smaller and lighter, and in order to respond to this demand, there are demands for miniaturization, higher efficiency and higher frequency of electronic components used in electric circuits of various electronic devices. Is growing rapidly.

  For example, Ni-Zn ferrite has been conventionally used as a coil magnetic core for a DC-DC converter of a portable device or the like. However, since Ni—Zn ferrite has a relatively large power loss, it has been difficult to cope with downsizing, high efficiency, and high frequency of components such as a coil magnetic core.

  For such a problem, it is conceivable to use Mn—Zn ferrite instead of Ni—Zn ferrite. Conventionally, Mn—Zn ferrite has been used in power transformers and the like, and has been used in a low frequency and high magnetic field environment.

  In general, a ferrite used as a magnetic core of a transformer or the like has been required to have temperature characteristics that minimize magnetic loss in a temperature range higher than the actual operating temperature range. This is because there is a risk of causing a so-called thermal runaway in which the transformer heats up due to magnetic loss and the temperature of the transformer itself rises, and as a result, the magnetic loss further increases and the heat generation of the transformer increases. is there. In the case of a power transformer, the operating temperature range is usually a temperature near the operating temperature (for example, 80 ° C.).

  However, in recent years, for example, when the transformer is cooled using a fluorine-based inert liquid or the like, it is possible to set the ambient temperature or use temperature to room temperature or lower, and further to an arbitrary temperature. In this case, the temperature at which the magnetic loss is minimized is not particularly limited, and it is only required that the absolute value of the magnetic loss is small.

  On the other hand, when used as a coil magnetic core for a DC-DC converter of a portable device or the like, the environmental temperature or the operating temperature is near room temperature or near the outside temperature, and the voltage is lower than that of a transformer, and there is less risk of thermal runaway. . In addition, as described above, such a portable device is required to have a high driving frequency (for example, 1 MHz or more) and to have a small loss in a high frequency region.

  Also, in transformers and parts used in portable devices such as DC-DC converters, the response to large currents is progressing. For this reason, a magnetic core used for such a component is required to have excellent direct current superposition characteristics that do not lower the inductance even with a large current. A high saturation magnetic flux density is indispensable for realizing an excellent DC superposition characteristic, and it is necessary to have a high saturation magnetic flux density particularly at the ambient temperature or the use temperature.

  Therefore, there is a need for a ferrite composition having an ambient temperature or operating temperature near room temperature or outside temperature, more specifically in the range of 0 to 50 ° C., reducing magnetic loss in a high frequency region and having a high saturation magnetic flux density. It has been.

As an example of a Mn—Zn ferrite having a low loss and a high saturation magnetic flux density, for example, in Patent Document 1, Fe ₂ O ₃ is 52.4 to 53.7 mol% and ZnO is 7.0 to 11 as main components. .5 mol%, and the remainder MnO, as an auxiliary component, and _CaO, and V 2 _{O 5,} and _{Nb 2 O 5, Al 2 O} 3 or _Bi 2 _{O 3} and a have been proposed Mn-Zn ferrite containing specified amounts Yes.

However, as described in Patent Document 1, the Mn—Zn ferrite described above is a temperature (Pcv _min ) at which the magnetic loss in the low frequency region is minimized at 60 ° C. or more, which is the actual driving temperature of the transformer. There is a problem that it is not suitable for use in the vicinity of room temperature and in a high frequency region.

JP 2003-128458 A

  The present invention has been made in view of such a situation, and the operating temperature or ambient temperature is near room temperature or near ambient temperature, more specifically in the range of 0 to 50 ° C., and in a high frequency and low magnetic field environment, It is an object of the present invention to provide an electronic component capable of achieving both a reduction in loss and a high saturation magnetic flux density, and a ferrite composition suitable for the electronic component.

In order to achieve the above object, the ferrite composition according to the present invention is composed mainly of 63.3 to 65.5 mol% of iron oxide in terms of Fe ₂ O ₃ and 11.6 to in terms of zinc oxide of zinc oxide. 15.8 mol% is contained, and the balance is composed of manganese oxide, with respect to 100% by weight of the main component, as subcomponents, silicon oxide is 60 to 250 ppm in terms of SiO _{2 and} calcium oxide is in terms of CaO. 360-1000 ppm is contained, Furthermore, in 100 weight% of the said main components, content of Pb is 7 ppm or less, and content of Cd is 7 ppm or less, It is characterized by the above-mentioned.

  In the present invention, considering use in the vicinity of room temperature or outside temperature, more specifically in the temperature range of 0 to 50 ° C., the temperature (Tsp) at which the magnetic loss is minimized is mainly in the range of 0 to 50 ° C. The components are determined, and the content of the subcomponents is within the specific range described above. By doing in this way, the ferrite composition which can reduce a power loss (Pcv) also in a high frequency area | region (for example, 1 MHz or more) can be obtained, keeping saturation magnetic flux density Bs high.

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

  Since the electronic component according to the present invention has a Tsp of the ferrite composition in the range of 0 to 50 ° C., it reduces power loss when used as a component whose operating temperature or environmental temperature is near room temperature or near ambient temperature. Can do. Moreover, since the ferrite composition of the present invention achieves both a reduction in power loss and a high saturation magnetic flux density, it is possible to realize power saving of an electronic component having a ferrite core made of the ferrite composition.

  Although it does not restrict | limit especially as an electronic component which concerns on this invention, The coil component of the DC-DC converter etc. which are used for portable apparatuses etc. are mentioned. Examples of the coil component include an inductor and a choke coil. Moreover, the electronic component according to the present invention can be suitably used for the transformer by cooling the transformer to a temperature near Tsp. Examples of transformer parts include power transformers for switching and inverters.

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

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

  As the ferrite core for the DC-DC converter according to this embodiment, in addition to the toroidal type shown in FIG. 1, FT type, ET type, EI type, UU type, EE type, EER type, UI type, drum type, pot Examples include molds and cup types. A desired coil magnetic core is obtained by winding a predetermined number of turns around the ferrite core for the DC-DC converter.

  The ferrite core for a DC-DC converter according to this embodiment is composed of the ferrite composition according to this embodiment.

  The ferrite composition according to this embodiment is a Mn—Zn ferrite and contains iron oxide, manganese oxide, and zinc oxide as main components. The temperature (Tsp) at which the magnetic loss of the ferrite composition according to this embodiment is minimized is in the range of 0 to 50 ° C.

  Conventionally, in Mn—Zn ferrite, the temperature showing Tsp has been explained by the magnetocrystalline anisotropy. That is, it is said that the magnetic loss has a minimum value at a temperature of K1 = 0 where the sign of the magnetocrystalline anisotropy constant K1 changes from a negative value to a positive value as the temperature rises.

Further, it is known that this temperature coincides with a so-called secondary peak of magnetic permeability where the magnetic permeability is maximized. The above K1 increases monotonously with increasing temperature, but Fe ²⁺ has a positive K1, so when the amount of Fe ²⁺ increases (ie, the amount of Fe ₂ O ₃ increases), the temperature of the secondary peak Moves to the low temperature side.

Based on the above findings and experimental results, page 79 of “Electronic Material Series Ferrite” (published by Maruzen Co., Ltd., 1988) has an Fe ₂ O ₃ content of X mol% and a ZnO content of Z mol%. The following formula is described as a formula for obtaining Tsp.
Tsp = -45.5 (X + 0.2Z) +2620

Further, it is known that a high saturation magnetic flux density can be easily obtained by increasing the amount of Fe ₂ O ₃ . However, when the amount of Fe ₂ O ₃ increases, the saturation magnetic flux density is considered to be influenced not only by the amount of Fe ₂ O ₃ but also by the ratio of the amount of Fe ₂ O _{3 and the} amount of ZnO.

Tsp of the ferrite composition according to the present embodiment is in the range of 0 to 50 ° C. In such a ferrite composition, it is conceivable to increase the saturation magnetic flux density by increasing Tsp within the above range by increasing the amount of Fe ₂ O ₃ . Therefore, when trying to determine the amount of Fe ₂ O ₃ and ZnO using the above formula, for example, if the amount of Fe ₂ O ₃ is 64.4 mol%, ZnO is 13.7 mol%, and the balance is MnO. , Tsp becomes −400 ° C. or lower, which is not realistic.

Therefore, it is considered that the above formula for obtaining Tsp does not hold when the amount of Fe ₂ O ₃ is large (for example, 63 mol% or more). However, since there is nothing which is an index for determining the Tsp if the amount of _Fe 2 _{O 3} is large, if the amount of _Fe 2 _{O 3} is large, in 1MHz or more high-frequency region, the ferrite composition having a high saturation magnetic flux density Had no knowledge.

Therefore, the present inventors have conducted intensive experiments and found that when the content of iron oxide in the ferrite composition is relatively large, Tsp and iron oxide and zinc oxide have a relationship different from the above formula. I found it. That is, the main component, 63.3 to 65.5 mol% of iron oxide calculated as _Fe 2 _{O 3,} preferably 63.9 to 65.0 mol%, zinc oxide in terms of ZnO 11.6 to 15.8 The present inventors have found that Tsp is in the range of 0 to 50 ° C. when the content is mol%, preferably 12.0 to 15.8 mol%, and the balance is manganese oxide.

  When the content of iron oxide or zinc oxide is small, the temperature (Tsp) at which the magnetic loss is minimized is less than 0 ° C, and when it is too much, it exceeds 50 ° C.

  The ferrite composition according to the present embodiment contains silicon oxide and calcium oxide as subcomponents in addition to the main components in the above composition range. By including such a subcomponent, the absolute value of power loss can be reduced and a high saturation magnetic flux density can be obtained.

The content of silicon oxide is 60 to 250 ppm, preferably 60 to 200 ppm in terms of SiO _{2 with} respect to 100% by weight of the main component. Even if the content of silicon oxide is large or too small, power loss in the high frequency region tends to deteriorate.

  The content of calcium oxide is 360 to 1000 ppm, preferably 630 to 830 ppm in terms of CaO with respect to 100% by weight of the main component. Even if the content of calcium oxide is large or too small, power loss in the high frequency region tends to deteriorate.

  Moreover, the ferrite composition according to the present embodiment contains Cd and Pb in addition to the above main component and subcomponent. By controlling such components within a predetermined range, it is possible to prevent power loss from deteriorating in a high frequency region.

  The content of Pb is 7 ppm or less, preferably 2 to 7 ppm, more preferably 5 to 7 ppm in 100% by weight of the main component. If the content exceeds 7 ppm in 100% by weight of the main component, the power loss in the high frequency region tends to deteriorate.

  The content of Cd is 7 ppm or less, preferably 2 to 7 ppm, more preferably 5 to 7 ppm in 100% by weight of the main component. If the content exceeds 7 ppm in 100% by weight of the main component, the power loss in the high frequency region tends to deteriorate.

  Pb and Cd may be contained in iron oxide, zinc oxide, and manganese oxide, which are main component materials. The inventors of the present application have found that when the contents of Pb and Cd in the main component exceed a predetermined range, power loss in a high frequency region tends to deteriorate. Therefore, in the present invention, the contents of Cd and Pd in the raw material are strictly controlled so as to be within the above range. The method for controlling the Pb and Cd contents to a predetermined range is not particularly limited.

  In addition, the ferrite composition according to the present embodiment may contain about several ppm to several hundred ppm of inevitable impurity element oxides in the raw material.

  Specifically, B, C, S, Cl, As, Se, Br, Te, I, Li, Na, Mg, Al, K, Ga, Ge, Sr, In, Sn, Sb, Ba, Bi, etc. And transition metal elements such as Sc, Ti, V, Cr, 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 a raw material for the main component, iron oxide (α-Fe ₂ O ₃ ), zinc oxide (ZnO), manganese oxide (Mn ₃ O ₄ ), or a composite oxide 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. In addition, although the content of manganese oxide in the main component is calculated in terms of MnO, Mn ₃ O ₄ is preferably used as the main component material.

As the raw material of the subcomponent, as in the case of the raw material of the main component, not only the oxide but also a composite oxide or a compound that becomes an oxide after firing may be used. In the case of silicon oxide (SiO ₂ ), it is preferable to use SiO ₂ . In the case of calcium oxide (CaO), it is preferable to use calcium carbonate (CaCO ₃ ).

  Cd and Pb are contained in iron oxide, zinc oxide, and manganese oxide, which are the main components. Therefore, the content of Cd and Pb can be adjusted by adjusting the use amounts of various iron oxide, zinc oxide and manganese oxide raw materials having different Cd and Pb contents.

  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 , ZnO, and Mn ₃ O ₄ were prepared as main components. SiO ₂ and CaCO ₃ were prepared as auxiliary component materials.

  Cd and Pb are contained in iron oxide, zinc oxide, and manganese oxide, which are the main components. Therefore, the usage amount of various iron oxides, zinc oxides and manganese oxide raw materials having different Cd and Pb contents are adjusted so that the finally obtained sample contains the Cd amount and Pb amount described in Tables 1 to 3. Adjusted and prepared.

  Next, the raw material powder of the main component prepared was weighed, and further, the powder of the subcomponent raw material was weighed to the amount shown in Table 1, and then wet mixed with a ball mill for 5 hours to obtain a raw material mixture. .

  Next, the obtained raw material mixture was calcined in air at 950 ° 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 having an average particle diameter of 1.5 μm. Obtained.

Next, this pulverized material was dried, and then granulated by adding 1.0% by weight of polyvinyl alcohol as a binder to 100% by weight of the pulverized material, and granulated with a 20 mesh sieve to obtain granules. This granule was pressure-molded at a pressure of 196 MPa ( ² ton / cm ² ) to obtain a molded body having a toroidal shape (size = outer diameter 22 mm × inner diameter 12 mm × height 6 mm).

  Next, each of these molded bodies was fired at 1270 ° C. for 2.5 hours while appropriately controlling the oxygen partial pressure to obtain a toroidal 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.

<Power loss (Pcv)>
The obtained toroidal core sample was wound with the primary winding and the secondary winding three times each, and the power loss at −10 to 60 ° C. was measured under the condition of 1 MHz-50 mT. Tsp) was determined, and the power loss Pcv at 25 ° C. was calculated (unit: kW / m ³ ). The measurement was performed using a BH analyzer (SY-8217 manufactured by Iwasaki Tsushinki Co., Ltd.). The results are shown in Tables 1-3.

<Saturation magnetic flux density (Bs)>
After winding the winding 60 times on the obtained toroidal core sample, the saturation magnetic flux density Bs when a magnetic field of 2 kA / m was applied using a BH curve tracer (Model BHS40 manufactured by Riken Denshi Co., Ltd.) Measurement was performed at 25 ° C. and 100 ° C. (unit: mT). The results are shown in Tables 1-3.

  Tables 1 to 3 show Pcv / Bs indicating the quality factor of the ferrite core at 1 MHz. The smaller Pcv or the larger Bs, the smaller this Pcv / Bs. Therefore, it is preferable that the value of Pcv / Bs is smaller because a reduction in power loss and a higher saturation magnetic flux density can be achieved at the same time. In the present embodiment, Pcv / Bs is preferably less than 1.30, more preferably 1.25 or less.

From Table 1, the subsidiary components SiO ₂ and CaO are simultaneously contained, and the contents of Pb and Cd contained in the raw materials are within the scope of the present invention, and the content of the main composition is within the scope of the present invention. In other words, in the samples according to Examples 1 to 8, it was confirmed that the temperature (Tsp) at which the power loss was minimized was in the range of 0 to 50 ° C. Furthermore, in the samples according to Examples 1 to 8, the power loss (Pcv) in the high frequency region (1 MHz) is low, and a high saturation magnetic flux density (Bs) is obtained, and the quality factor expressed by Pcv / Bs is good. It was confirmed that

On the other hand, from Table 1, in the case where the content of ZnO of iron oxide Fe ₂ O ₃ or zinc oxide is outside the scope of the present invention in the main component composition (Comparative Examples 1 to 4), the quality factor The tendency for Pcv / Bs to deteriorate was confirmed.

Further, from Table 2, even when subcomponents (SiO ₂ and CaO) are contained, Tsp does not change, and the content is within the scope of the present invention (Examples 9 to 13). It was confirmed that a reduction in loss and a high saturation magnetic flux density were compatible, and the quality factor Pcv / Bs was good.

On the other hand, from Table 2, when the content of silicon oxide SiO ₂ or calcium oxide CaO as a subcomponent is outside the scope of the present invention (Comparative Examples 5 to 8), the quality factor Pcv / Bs is deteriorated. The tendency to do was confirmed.

  Further, from Table 3, when the contents of Cd and Pb are within the scope of the present invention (Examples 14 to 21), it is possible to achieve both reduction of power loss at 1 MHz and high saturation magnetic flux density, and the quality factor Pcv / Bs is It was confirmed to be good.

  On the other hand, from Table 3, when Cd or Pb is outside the scope of the present invention (Comparative Examples 9 and 10), it was confirmed that the quality factor Pcv / Bs does not fall within a favorable range.

  In the electronic component according to the present invention, power loss is reduced in the operating temperature range, and a high saturation magnetic flux density is obtained. Even when the electronic component according to the present invention is used in a portable device or the like, consumption of a battery or the like can be suppressed, and power saving can be realized.

Claims (3)

Main component 63.3 to 65.5 mol% of iron oxide calculated as _Fe 2 _{O 3,} zinc oxide containing 11.6 to 15.8 mol% calculated as ZnO, and the balance is composed of a manganese oxide In addition, 100% by weight of the main component contains 60 to 250 ppm of silicon oxide in terms of SiO ₂ and 360 to 1000 ppm of calcium oxide in terms of CaO as subcomponents. A ferrite composition having a Pb content of 7 ppm or less and a Cd content of 7 ppm or less.   The electronic component which has a ferrite core comprised from the ferrite composition of Claim 1, and is used in the range whose temperature is 0-50 degreeC.   The electronic component which has a ferrite core comprised from the ferrite composition of Claim 1, and is used in a frequency range of 1 MHz or more.

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