WO2010113681A1 - 複合磁性材料及び磁性素子 - Google Patents
複合磁性材料及び磁性素子 Download PDFInfo
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- WO2010113681A1 WO2010113681A1 PCT/JP2010/054828 JP2010054828W WO2010113681A1 WO 2010113681 A1 WO2010113681 A1 WO 2010113681A1 JP 2010054828 W JP2010054828 W JP 2010054828W WO 2010113681 A1 WO2010113681 A1 WO 2010113681A1
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- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/147—Alloys characterised by their composition
- H01F1/14766—Fe-Si based alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
- B22F1/062—Fibrous particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
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- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C22C9/00—Alloys based on copper
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- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
- H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
- H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
- H01F1/26—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated by macromolecular organic substances
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C2202/00—Physical properties
- C22C2202/02—Magnetic
Definitions
- the present invention relates to a composite magnetic material and a magnetic element. More specifically, the present invention relates to a composite magnetic material containing Mn, Si, Cr, the remaining Fe, and inevitable impurities in a specific ratio, and a magnetic element using the composite magnetic material.
- Patent Document 1 compression-molds a powder magnetic body composed of an alloy powder mainly composed of Fe, Al, and Si and a binder, and has an oxidizing atmosphere.
- Patent Document 2 Japanese Patent Application Laid-Open No. 2008-240041
- Patent Document 2 includes a soft magnetic powder mainly composed of Fe, Si, and Cr and manufactured by an atomizing method, and the soft magnetic powder and a binder.
- a compression-molded powder magnetic core has been proposed.
- the Cr content is more than 8 and 13 wt% or less.
- the dust core proposed in Patent Document 1 is excellent in terms of reducing core loss because the eddy current generated in the magnetic core is divided between the particles.
- the alloy powder is oxidized and rust is generated when it is in contact with air for a long time because Cr is not added.
- the binder may be deteriorated or deteriorated, which may increase core loss.
- the core loss increases, the heat generation of the powder magnetic core increases, and accordingly, the alteration and deterioration of the binder are further accelerated. Such a tendency becomes more apparent as the particle size of the alloy powder is smaller.
- the dust core described in Patent Document 2 is qualitatively evaluated for the relative permeability and core loss, and the corrosion resistance is evaluated by the relative value of the initial specific resistance and the specific resistance after 10 days.
- a powder magnetic core having a Cr content in the above range shows good corrosion resistance, but quantitative data is not shown.
- For dust cores and other magnetic elements there are chemical demands such as corrosion resistance, so there is a high social demand for these well-balanced composite magnetic materials and magnetic elements using such magnetic materials. .
- the present invention has been completed under the above circumstances, and an object thereof is to provide a composite magnetic material having a good balance of electrical characteristics, magnetic characteristics, and chemical characteristics, and a magnetic element using such a magnetic material. To do. That is, according to the present invention, Mn of 0.25 wt% or more and 3 wt% or less and 1 wt% or more of the total weight of the magnetic powder material (hereinafter sometimes referred to as “magnetic powder particles” or “powder particles”).
- the proportion of powder particles containing 7 wt% or less of Si, 2 wt% or more and 8 wt% or less of Cr, and the balance of Fe and inevitable impurities and having a major axis / minor axis ratio of 2 or more is 5% of the total powder particles
- This is a composite magnetic material containing the following magnetic powder and a binder.
- the magnetic powder preferably has an average particle size of about 50 ⁇ m or less, and more preferably an average particle size of about 10 ⁇ m or less.
- the binder is preferably an epoxy resin.
- the composite magnetic material preferably has an insulation resistivity of 150 M ⁇ ⁇ cm or more, and a dielectric breakdown electric field of 1.6 kV / cm or more. Moreover, it is preferable that the core loss is 5 w / cm 3 or less when measured at a magnetic flux density of 50 mT and an effective frequency of 500 kHz. Furthermore, the relative magnetic permeability of the composite magnetic material of the present invention is preferably 19 or more. As described above, it is possible to obtain a composite magnetic material having high insulation resistivity, dielectric breakdown electric field, and low core loss.
- the present invention is also a magnetic element manufactured by the above composite magnetic material.
- the magnetic element preferably has a rust generation area of 5% or less of the surface area of the composite magnetic element after being kept in an atmosphere of 105 ° C. and 100% humidity for 8 hours. If the magnetic element has a high rust prevention property, it is possible to manufacture a magnetic element that keeps stable electrical characteristics over a long period of time without rust flying within the element.
- a composite magnetic material having excellent characteristics can be produced. Moreover, by using this composite magnetic material, a high-performance magnetic element having excellent corrosion resistance can be manufactured.
- FIG. 1A is a front view showing a composite magnetic element (before completion) taken out from a powder molding machine.
- 1B is a cross-sectional view of the magnetic element shown in FIG. 1A.
- FIG. 2A is a front view showing the completed composite magnetic element.
- 2B is a cross-sectional view of the composite magnetic element shown in FIG. 2A.
- FIG. 3 is a graph showing the relationship between the Mn content, the ratio of the long diameter / short diameter ratio ⁇ 2 of the present invention examples 1 to 8 and comparative examples 1 to 2, the dielectric resistivity, the dielectric breakdown electric field, and the Pcv. .
- FIG. 1A is a front view showing a composite magnetic element (before completion) taken out from a powder molding machine.
- 1B is a cross-sectional view of the magnetic element shown in FIG. 1A.
- FIG. 2A is a front view showing the completed composite magnetic element.
- 2B is a cross-sectional view of the composite magnetic element shown in FIG. 2
- FIG. 4 is a graph showing the relationship between the relative magnetic permeability and Pcv of Invention Examples 9 to 13 and Comparative Examples 3 to 4, and the Si content.
- FIG. 5 is a graph showing the relationship between the relative magnetic permeability of Examples 14 to 18 and Comparative Examples 5 to 6 and the Cr content.
- the present invention is described in detail below.
- the composite magnetic material of the present invention comprises 0.25 wt% or more and 3 wt% or less of Mn, 1 wt% or more and 7 wt% or less of Si, 2 wt% or more and 8 wt% or less of Cr, and the balance with respect to the total weight of the magnetic powder.
- a magnetic material powder containing Fe and unavoidable impurities and the ratio of the major axis / minor axis ratio being 2 or more is 5% or less of the entire powder particles, and the binder.
- the Mn content is preferably 0.25 wt% or more and 3 wt% or less with respect to the total weight of the magnetic powder material because a magnetic material having excellent electrical characteristics can be obtained, and 0.4 wt% More preferably, it is 1 wt% or less.
- the Mn content is less than 0.25 wt%, there are the following problems. That is, since the ratio of powder particles having a major axis / minor axis ratio of 2 or more is large, the insulation resistivity and the dielectric breakdown electric field are low, and the core loss is increased. In addition, wire damage occurs during product formation. Conversely, if it exceeds 3 wt%, there are the following problems. That is, the insulation resistivity and the breakdown electric field do not increase greatly, and the core loss does not greatly improve, but the relative permeability is greatly decreased.
- the Si content is preferably 1 wt% or more and 7 wt% or less with respect to the total weight of the magnetic powder material because a magnetic material having excellent magnetic properties can be obtained, and is 3 wt% or more and 5 wt% or less. More preferably it is.
- the content of Cr is preferably 2 wt% or more and 8 wt% or less with respect to the total weight of the magnetic powder material because a magnetic material having excellent chemical characteristics can be obtained, and is preferably 3 wt% or more and 5 wt% or less. Further preferred. If the Cr content is less than 2 wt%, sufficient corrosion resistance cannot be obtained, and if it exceeds 8 wt%, the relative magnetic permeability is greatly reduced.
- the ratio of powder particles having a major axis / minor axis ratio of 2 or more is preferably 5% or less of the entire powder particles.
- the physical properties of the composite magnetic material are improved, such as an increase in insulation resistivity and breakdown electric field, and a decrease in core loss.
- Epoxy resins can be suitably used as a binder because they have low cure shrinkage and are excellent in adhesiveness, heat resistance, and electrical properties.
- the amount of the binder added is preferably about 2 to 5 wt% with respect to the total weight of the composite magnetic material from the viewpoint of securing the required relative magnetic permeability and core loss.
- the insulation resistivity is preferably 150 M ⁇ ⁇ cm or more from the viewpoint of suppressing eddy current loss (core loss), and more preferably 160 M ⁇ ⁇ cm or more.
- the dielectric breakdown electric field is preferably 1.6 kV / cm or more from the viewpoint of ensuring a sufficient withstand voltage of the magnetic element, and more preferably 2.6 kV / cm or more.
- the composite magnetic body preferably has a core loss of 5 w / cm 3 or less when measured at a magnetic flux density of 50 mT and an effective frequency of 500 kHz in order to suppress heat generation of the magnetic element, and is 4.5 w / cm 3 or less. More preferably.
- the average particle size of the magnetic powder particles (alloy powder particles) used in the composite magnetic material is preferably 5 ⁇ m or more and 6 ⁇ m or less in order to suppress core loss. If the thickness is 10 ⁇ m or less, substantially the same effect can be obtained.
- the present invention is also a magnetic element manufactured by the composite magnetic material having the physical properties as described above. The production of the composite magnetic material and the composite magnetic element of the present invention will be described with reference to FIGS. 1A and 1B, taking as an example the case of using a composite magnetic material having the composition shown in Table 1 below.
- Alloy powder particles having the composition shown in Table 1 above are produced by a water atomization method or other desired methods.
- the ratio of major axis / minor axis of the obtained alloy powder particles is determined by observing the powder particle shape using a scanning electron microscope.
- a binder By spraying a binder on the alloy powder particles, a composite magnetic material in which the surface of the alloy powder is coated with an epoxy resin is obtained.
- a magnetic element having a desired thickness and size is manufactured as follows.
- the size of the magnetic element can be, for example, 6 to 15 mm ⁇ 6 to 15 mm and a thickness of 2 to 6 mm.
- a copper wire formed in a coil shape is molded with a composite magnetic material (see FIGS. 1A and 1B).
- the copper wire diameter, the coil inner diameter, and the number of turns used to create the coil 12 are determined according to the size of the magnetic element and the required product characteristics.
- the copper wire used here may be either a flat wire or a round wire.
- the external terminals 14 1 and 14 2 a thin copper plate having a desired size and plated with Sn is prepared.
- the tip of the coil and the external terminal are connected by spot welding. Welding can also be performed by methods such as arc welding, ultrasonic welding, thermal diffusion welding, and soldering in addition to spot welding.
- the composite magnetic material shown in Table 1 and the above-described coil with external terminals are inserted into a mold of a powder molding machine and molded at a desired molding pressure, for example, 2 to 6 ton / cm 2 . Thereafter, the molded body is taken out from the molding machine and heated at a desired temperature, for example, about 100 to about 200 ° C. for about 30 to 90 minutes to cure the resin. After naturally cooling the molded body obtained as described above (see FIGS. 1A and 1B), the terminals 14 1 and 14 2 are bent along the outside of the molded magnetic powder to obtain a magnetic element. (See FIGS. 2A and 2B).
- Example 1 Examination of Mn content (1) Production of magnetic material The change in the shape of the particles due to the addition amount of Mn when the content ratio of Si and Cr was constant was confirmed using a scanning electron microscope, The ratio and average particle diameter of powder particles having a major axis / minor axis ratio of 2 or more were determined.
- the Mn content was as shown in Table 2 below, and particles were produced by a well-known water atomization method.
- the average particle size of the prepared powder was 10 ⁇ m or less.
- a molded body was obtained from the obtained composite magnetic powder based on the following molding conditions.
- Molding condition Molding method: Compression molding Molded body shape: Ring-shaped core Disc core Molded body dimensions: Ring-shaped core Outer diameter 15 mm, inner diameter 10 mm, thickness 2.5 mm Disc core outer diameter 10mm, thickness 0.6mm Molding pressure: 4 ton / cm 2
- the ring-shaped core was used for measurement of relative permeability and core loss.
- the disk core was used for measurement of insulation resistivity, dielectric breakdown electric field, and observation of rust generation.
- the compact was heated in air at 100 ° C. for 1 hour to cure the binder, and a dust core was obtained.
- Dielectric breakdown electric field (kV / cm): The electric resistance when a voltage is applied to the front and back surfaces of the disk core is measured to determine the voltage at which the electric resistance rapidly decreases, and the value is taken as the dielectric breakdown electric field. . A sufficient dielectric breakdown electric field was obtained when the Mn content was 0.25 wt% or more.
- (C) Relative permeability The ring core was measured for inductance at a frequency of 1 MHz with an LCR meter, and the relative permeability was obtained from the core constant of the ring core.
- the relative magnetic permeability ( ⁇ r ) was obtained from the following formula.
- ( ⁇ r ) (Ls ⁇ le ) / ( ⁇ 0 ⁇ Ae ⁇ N 2 )
- Ls is the inductance (H)
- l e is the magnetic path length (m)
- Ae is the cross-sectional area (m 2 )
- ⁇ 0 the magnetic permeability (H / m) in vacuum
- N is the number of turns of the coil. .
- the insulation resistivity and the breakdown electric field were low, and the core loss was high.
- the relative magnetic permeability was low.
- the dust cores of Examples 1 to 8 of the present invention were evaluated as having high relative permeability but low core loss and good balance. From the above, the Mn content was set to 0.25 wt% or more and 3 wt% or less.
- Example 2 Examination of Si content A dust core having the composition shown in Table 4 below was prepared, and physical properties were evaluated by relative permeability and core loss. The core loss measurement conditions were the same as in Example 1. The results are shown in Table 4.
- Example 3 Examination of Cr content Dust cores having the compositions shown in Table 5 below were prepared, and the physical properties were evaluated by the relative permeability and the occurrence of rust.
- the dust core for rust evaluation used in this example was evaluated by observing the occurrence of rust with the naked eye after performing rust prevention treatment.
- an inorganic rust prevention aqueous solution containing boron oxide and sodium oxide was used for the rust prevention treatment.
- a relative permeability greater than 19.0 was designated as A, and less than 19.0 was designated as C.
- B for rusted area ⁇ 5%
- C for rusted area ⁇ 5%.
- the dust core produced for this example was submerged in a glass sealed container containing the above-mentioned inorganic anticorrosive solution, and immersed for 5 minutes under reduced pressure. Thereafter, the dust core was pulled up from the treatment liquid and dried by heating at 140 ° C. for 60 minutes.
- the dust core subjected to the rust prevention treatment as described above was held in a humidity chamber for 8 hours in an atmosphere having a temperature of 105 ° C. and a humidity of 100%. The state of rust generation on the surfaces of the magnetic elements of Invention Examples 14 to 18 and Comparative Examples 5 and 6 was observed.
- the occurrence of rust is 5% of the front and back area of the dust core, and A is the case where rust is not observed, and B is the case where rust is observed but less than 5%.
- % Was evaluated as C.
- the dust core of Comparative Example 5 having a Cr content of 1.8 wt% rust was generated in a wide range.
- Comparative Example 6 in which the Cr content was 7.2 wt%, the relative magnetic permeability was greatly reduced.
- the relative magnetic permeability was not greatly reduced, and the occurrence of rust was less than 5%. From the above, the Cr content was set to 2 wt% to 8 wt%.
- Example 4 Examination of Inductance and Core Loss Magnetic elements having the compositions shown in Table 6 below were manufactured, and the inductance and core loss were measured. Inductance was measured at an effective frequency (f) of 1 MHz. The core loss was measured at a magnetic flux density of 25 mT and an effective frequency of 500 kHz. The results are shown in Table 6.
- the core loss of the magnetic element of the present invention was about 20% smaller. From the above, 0.25 wt% or more and 3 wt% or less of Mn, 1 wt% or more of 7 wt% or less of Si, 2 wt% or more of 8 wt% or less of Cr, and Fe and inevitable impurities as the balance, It is shown that the composite magnetic element produced using the magnetic powder whose ratio of the powder particles having a ratio of 2 or more is 5% or less of the whole powder particles is excellent in the various characteristics described above. It was.
- the present invention is useful for reducing the size, weight, and performance of PDA and other electronic devices.
Abstract
Description
ところで、こうした磁性素子の駆動周波数が高くなると、各磁性素子が備える磁心では、渦電流によるジュール損失(渦電流損失ともいう、以下「コア損失」ということがある。)が増大するという問題がある。その一方で、こうした機器の安定した電気特性を保証するためには、錆の発生を防止する必要もある。
特開2008-240041号公報(以下、「特許文献2」という)には、Fe,Si,Crを主成分とし、アトマイズ法で製造された軟磁性粉末と、この軟磁性粉末と結合材とを圧縮成形した圧粉磁心が提案されている。この公報に記載された圧粉磁心の成分中、Crの含有量は8超13wt%以下となっている。
圧粉磁心その他の磁性素子に対しては、耐食性等の化学的な面からの要請もあるため、これらのバランスのよい複合磁性材料及びそうした磁性材料を用いた磁性素子に対する社会的な要請は高い。
すなわち、本発明は、磁性粉末材料(以下、「磁性粉末粒子」又は「粉末粒子」ということがある。)の総重量に対して、0.25wt%以上3wt%以下のMnと、1wt%以上7wt%以下のSiと、2wt%以上8wt%以下のCrと、残部としてFe及び不可避不純物とを含み、長径/短径の比が2以上である粉末粒子の割合が、粉末粒子全体の5%以下である磁性体粉末と、結合材と、を含む複合磁性材料である。ここで、上記磁性体粉末は、平均粒径が約50μm以下であることが好ましく、平均粒子径が約10μm以下であることがさらに好ましい。また、上記結合材は、エポキシ系樹脂であることが好ましい。
以上により、絶縁抵抗率、絶縁破壊電界が高く、コア損失が低い複合磁性材料を得ることが可能となる。
本発明はまた、上記の複合磁性材料によって製造された磁性素子である。この磁性素子は、105℃、湿度100%の雰囲気中で8時間保持した後の錆の発生面積が、前記複合磁性素子の表面積の5%以下であることが好ましい。
磁性素子の防錆性が高ければ、錆が素子内で飛ぶことがなく、安定した電気特性を長期間に渡って保持する磁性素子を製造することが可能となる。
本発明の複合磁性材料は、磁性粉末の総重量に対して、0.25wt%以上3wt%以下のMnと、1wt%以上7wt%以下のSiと、2wt%以上8wt%以下のCrと、残部としてFe及び不可避不純物とを含み、長径/短径の比が2以上である粉末粒子の割合が、粉末粒子全体の5%以下である磁性体粉末と、結合材と、を含むものである。
ここで、上記Mnの含量は、磁性粉末材料の総重量に対して、0.25wt%以上3wt%以下であることが、電気特性に優れる磁性材料を得ることができることから好ましく、0.4wt%以上1wt%以下とすることがさらに好ましい。Mn含量が0.25wt%未満であると以下の問題がある。すなわち、長径/短径の比が2以上の粉末粒子の割合が多いため、絶縁抵抗率及び絶縁破壊電界が低く、コア損失が大きくなる。また、製品形成時のワイヤダメージも発生する。逆に、3wt%を超えると、以下の問題がある。すなわち、絶縁抵抗率及び絶縁破壊電界が大きく上昇することはなく、コア損失も大きな改善が見られないが、比透磁率は大きく低下する。
上記Crの含量は、磁性粉末材料の総重量に対して、2wt%以上8wt%以下であることが化学特性に優れる磁性材料を得ることができることから好ましく、3wt%以上5wt%以下であることがさらに好ましい。Crの含量が2wt%未満では十分な耐食性が得られず、8wt%を超えると比透磁率が大きく低下することによる。
エポキシ系樹脂は、硬化収縮が小さく、接着性、耐熱性及び電気的性質に優れていることから、結合材として好適に使用することができる。また、結合材の添加量は、複合磁性材料の総重量に対して、約2~5wt%であることが、要求される比透磁率やコア損失を確保する面から好ましい。
本発明の複合磁性材料においては、上記絶縁抵抗率が150MΩ・cm以上であることが渦電流損失(コア損失)の抑制という点から好ましく、160MΩ・cm以上であることがさらに好ましい。
また、上記絶縁破壊電界は、1.6kV/cm以上であることが磁性素子の十分な耐電圧を確保できることから好ましく、2.6kV/cm以上であることがさらに好ましい。
また、上記複合磁性材料に使用した磁性粉末粒子(合金粉末粒子)の平均粒径は、5μm以上6μm以下であることがコア損失を抑制する上で好ましい。なお、10μm以下であれば、ほぼ同等の効果が得られる。
本発明はまた、上述したような物性を有する複合磁性材料によって製造された磁性素子である。本発明の複合磁性材料及び複合磁性素子の製造を、下記表1に示す組成の複合磁性材料を使用した場合を例に挙げて、図1A及び1Bを参照しつつ説明する。
合金粉末粒子に結合材を噴霧することにより、合金粉末の表面がエポキシ系樹脂で被覆された複合磁性材料を得る。
本発明の複合磁性素子は、コイル状に成形した銅線を複合磁性材料でモールドしている(図1A及びB参照)。コイル12の作成に使用する銅線径、コイル内径及び巻数は、磁性素子の大きさ、要求される製品特性に応じて定まる。
ここで使用する銅線は、平角線又は丸線のいずれを使用してもよい。次に、外部端子用の141,142として、Snメッキを施した、所望の大きさの薄い銅板を準備する。各々の外部端子141,142に、コイル12の各先端を溶接し、外部端子付きコイルとする。コイルの先端と外部端子とは、スポット溶接で接続する。溶接は、スポット溶接の他、アーク溶接、超音波溶接、熱拡散溶接、半田付け等の方法で行うこともできる。
以上のようにして得られた成形体を自然放冷後(図1A及び1B参照)、端子141,142を、成型された磁性体粉末の外側に沿うように折り曲げて、磁性素子を得る(図2A及び2B参照)。
(実施例1) Mn含量の検討
(1)磁性材料の製造
Si、Crの含有率を一定としたときのMnの添加量による粒子の形状の変化を、走査型電子顕微鏡を用いて確認し、長径/短径の比が2以上の粉末粒子の比率と平均粒径を求めた。Mn含量は、下記表2に示す通りの含量とし、周知の水アトマイズ法によって粒子を製造した。作製した粉末の平均粒径は、10μm以下を用いた。
上記表2に示す平均粒径の合金粉末を使用して、以下の複合磁性粉末を作製した。
下記表3に示す組成を有する合金粉末を、水アトマイズ法によって製造した。次に、合金粉末に結合材(エポキシ系樹脂)を噴霧することにより、合金粉末の表面がエポキシ系樹脂で被覆された複合磁性材料を得る。
[成形条件]
成形方法:圧縮成形
成形体形状:リング状コア
ディスクコア
成形体寸法:リング状コア 外径15mm、内径10mm、厚み2.5mm
ディスクコア 外径10mm、厚み0.6mm
成形圧力:4ton/cm2
リング状コアは、比透磁率、コア損失の測定に使用した。
ディスクコアは、絶縁抵抗率、絶縁破壊電界の測定、錆発生の観察に使用した。
次に成形体を大気中で、100℃、1時間加熱して結合材を硬化させて、圧粉磁芯を得た。
本発明例1~8、及び比較例1~2の磁性体粉末を使用して作製した圧粉磁芯の物性の測定項目を、絶縁抵抗率(MΩ・cm)、絶縁破壊電界(kV/cm)、比透磁率及びPcv(w/cm3)として測定し、評価した。それぞれの物性の測定条件及び評価の基準を以下に示す。
(a)絶縁抵抗率(MΩ・cm):ディスクコアの表裏面に電圧60Vを印加した時の電気抵抗を測定して、試料厚みを考慮して絶縁抵抗率を求めた。表3に示すように、Mn含量が0.25wt%以上で十分な絶縁抵抗率が得られた。
(b)絶縁破壊電界(kV/cm):ディスクコアの表裏面に電圧を印加した時の電気抵抗を測定して、電気抵抗が急激に低下する電圧を求め、その値を絶縁破壊電界とした。Mn含量が0.25wt%以上で十分な絶縁破壊電界が得られた。
(μr)=(Ls×le)/(μ0×Ae×N2)
ここで、Lsはインダクタンス(H)、leは磁路長(m)、Aeは断面積(m2)、μ0は真空中における透磁率(H/m)、Nはコイルの巻数を表す。
以上より、Mn含量が3.0wt%以下で十分な比透磁率が得られた。
(d)コア損失(Pcv;w/cm3):リング状コアを交流B-H曲線測定装置を用いて、Bm=50mT、f(実効周波数)=500kHzの条件で測定した。Mn含量0.25wt%以上で、十分なコア損失が得られた。
*1:粒子比率の評価について、5%以下をA、5%超をCとした。
*2:絶縁抵抗率の評価について、150(MΩ・cm)超をA、150(MΩ・cm)をB、150(MΩ・cm)未満をCとした
*3:絶縁破壊電界の評価について、1.5(kV/cm)超をA、1.5(kV/cm)以下をCとした。
*4:比透磁率の評価について、19.0超をA、19.0をB、19.0未満をCとした。
*5:Pcv測定条件は、Bm=50mT、f=500kHzとした。
*6:Pcvの評価について、5.0(w/cm3)以下をA、5.0(w/cm3)超をCとした。
これに対し、本発明例1~8の圧粉磁芯は、比透磁率は高いがコア損失が低く、バランスが良いと評価された。
以上より、Mnの含量を0.25wt%以上3wt%以下とした。
下記表4に示す組成の圧粉磁芯を作製し、物性を比透磁率及びコア損失で評価した。コア損失の測定条件は、実施例1と同様とした。結果を表4に示す。
これに対し、本発明例9~13の圧粉磁芯では、いずれも良好な物性値を示した。
下記表5に示す組成の圧粉磁芯を作製し、物性を比透磁率及び錆の発生で評価した。本実施例で使用した錆評価用の圧粉磁芯は、防錆処理を行った後に錆の発生を肉眼で観察し、評価した。防錆処理には酸化ボロンと酸化ナトリウムとを含有する無機防錆水溶液を使用した。
以上のように防錆処理した圧粉磁芯を、恒湿器中にて、温度105℃、湿度100%の雰囲気中に8時間保持した。本発明例14~18、比較例5及び6の磁性素子表面における錆発生状況を観察した。
Cr含量が1.8wt%の比較例5の圧粉磁芯では錆が広範囲に発生した。また、Cr含量が7.2wt%の比較例6では比透磁率が大きく低下していた。
これに対し、本発明例14~18の圧粉磁芯では、比透磁率の大きな低下もなく錆の発生も5%未満であった。
以上より、Cr含量を2wt%~8wt%とした。
下記表6に示す組成の磁性素子を作製し、インダクタンス及びコア損失を測定した。インダクタンスは、実効周波数(f)1MHzで測定した。また、コア損失は磁束密度25mT、実効周波数500kHzで測定した。結果を表6に示す。
以上より、0.25wt%以上3wt%以下のMnと、1wt%以上7wt%以下のSiと、2wt%以上8wt%以下のCrと、残部としてFe及び不可避不純物とを含み、長径/短径の比が2以上である粉末粒子の割合が、粉末粒子全体の5%以下である磁性体粉末を使用して作製した複合磁性素子は、上述した各種の特性に優れたものであることが示された。
Claims (7)
- 磁性粉末材料の総重量に対して、
0.25wt%以上3wt%以下のMnと、
1wt%以上7wt%以下のSiと、
2wt%以上8wt%以下のCrと、
残部としてFe及び不可避不純物とを含み、長径/短径の比が2以上である粉末粒子の割合が、粉末粒子全体の5%以下である磁性体粉末と、
結合材と、
を含む、複合磁性材料。 - 絶縁抵抗率が150MΩ・cm以上であることを特徴とする、請求項1に記載の複合磁性材料。
- 絶縁破壊電界が、1.6kV/cm以上であることを特徴とする、請求項1に記載の複合磁性材料。
- 磁束密度50mT、実効周波数500kHzで測定したときのコア損失が5w/cm3以下であることを特徴とする、請求項1に記載の複合磁性材料。
- 前記結合材の含有量が、前記複合磁性材料の2.5~4.5重量%であることを特徴とする、請求項1に記載の複合磁性材料。
- 請求項1~5のいずれかに記載の複合磁性材料によって製造された磁性素子。
- 温度105℃、湿度100%の雰囲気中で8時間保持した後の錆の発生面積が、前記磁性素子の表面積の5%以下であることを特徴とする、請求項6に記載の磁性素子。
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JP2016171115A (ja) | 2015-03-11 | 2016-09-23 | スミダコーポレーション株式会社 | 磁性素子および磁性素子の製造方法 |
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