JP2009158802A - Manufacturing method of dust core - Google Patents

Manufacturing method of dust core Download PDF

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JP2009158802A
JP2009158802A JP2007337137A JP2007337137A JP2009158802A JP 2009158802 A JP2009158802 A JP 2009158802A JP 2007337137 A JP2007337137 A JP 2007337137A JP 2007337137 A JP2007337137 A JP 2007337137A JP 2009158802 A JP2009158802 A JP 2009158802A
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soft magnetic
metal particles
dust core
magnetic metal
oxide film
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Takayuki Hirose
隆之 広瀬
Masaharu Edo
雅晴 江戸
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Fuji Electric Co Ltd
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Fuji Electric Device Technology Co Ltd
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<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a dust core in which the dust core having superior high-frequency characteristics and superior magnetic permeability can be obtained. <P>SOLUTION: Disclosed is the manufacturing method of the dust core characterized in that, after soft magnetic metal particles each having an insulating oxide skin on a surface are pressed and formed, heat treatment is carried out in an atmosphere of ≤1013 Pa in oxygen partial pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、圧粉磁心の製造方法に関する。この圧粉磁心はスイッチング電源用トランス、リアクトルなどに用いるものとして有用である。   The present invention relates to a method for manufacturing a dust core. The dust core is useful as a transformer for a switching power supply, a reactor, and the like.

近年、各種電子機器は、小形化、軽量化されてきており、これに伴い電子機器に搭載されているスイッチング電源も小形化の要求が高まっている。特にノート型パソコンや小型携帯機器、薄型CRT、フラットパネルディスプレイに用いられるスイッチング電源では、小型化、薄型化が強く求められている。しかしながら、従来のスイッチング電源は、その主要な構成部品であるトランス、リアクトル等の磁気部品が、大きな体積を占め、小型化、薄型化することに限界があった。これら磁気部品の体積を小型、薄型化しない限り、スイッヂング電源を小型化、薄型化することは困難となっていた。   In recent years, various electronic devices have been reduced in size and weight, and accordingly, switching power sources mounted on the electronic devices have been required to be reduced in size. In particular, switching power supplies used in notebook personal computers, small portable devices, thin CRTs, and flat panel displays are strongly required to be small and thin. However, in conventional switching power supplies, magnetic components such as transformers and reactors, which are main components, occupy a large volume, and there has been a limit to downsizing and thinning. Unless the volume of these magnetic components is reduced in size and thickness, it has been difficult to reduce the size and thickness of the switching power supply.

従来、このようなスイッチング電源に使用されているトランス、リアクトルなどの磁気部品には、センダストやパーマロイなどの金属磁性材料や、フェライトなどの酸化物磁性材料が使用されていた。そのうち金属磁性材料は、一般に高い飽和磁束密度と透磁率を有するが、電気抵抗率が低いため、特に高周波数領域では渦電流損失が大きくなってしまう。近年、電源回路を高周波駆動して必要なインダクタンス値を下げることにより磁気部品を小型化する傾向にあるが、渦電流損失の影響から金属磁性材料を高周波で使用することはできない。   Conventionally, metal magnetic materials such as Sendust and Permalloy and oxide magnetic materials such as ferrite have been used for magnetic parts such as transformers and reactors used in such switching power supplies. Among them, the metal magnetic material generally has a high saturation magnetic flux density and magnetic permeability, but since the electrical resistivity is low, eddy current loss is particularly large in a high frequency region. In recent years, magnetic components tend to be miniaturized by reducing the required inductance value by driving the power supply circuit at a high frequency, but metal magnetic materials cannot be used at a high frequency due to the influence of eddy current loss.

一方、酸化物磁性材料は、金属磁性材料に比べ、電気抵抗率が高いため、高周波数領域でも発生する渦電流損失が小さい。しかしながら、飽和磁束密度が小さいため、磁気飽和しやすいことから、その体積を小さくすることができなかった。つまり、いずれの場合でも、磁性体コアの体積がインダクタンス値を決定付ける一番大きな要因となっていて、磁性材料の磁気特性を向上させない限り、小型化、薄型化が困難となっていた。   On the other hand, an oxide magnetic material has a higher electrical resistivity than a metal magnetic material, and hence eddy current loss that occurs even in a high frequency region is small. However, since the saturation magnetic flux density is small, magnetic saturation is likely to occur, and thus the volume cannot be reduced. That is, in any case, the volume of the magnetic core is the largest factor determining the inductance value, and it has been difficult to reduce the size and thickness unless the magnetic properties of the magnetic material are improved.

このように、従来の磁気部品では、小型化に限界があり、電子機器の小型化、薄型化の要求に充分に応えられるものではなかった。   As described above, the conventional magnetic parts have a limit in miniaturization, and cannot sufficiently meet the demand for miniaturization and thinning of electronic devices.

この課題を解決する方法として、特許文献1には、1〜10μmの粒子からなる金属磁性材料の表面をM−Fex4(但しM=Ni、Mn、Zn、x≦2)で表されるスピネル組成の金属酸化物磁性材で被覆してなる粉体による高密度焼結磁性体が提案されている。 As a method for solving this problem, Patent Document 1, is represented by the surface of the metallic magnetic material consisting of 1~10μm particles M-Fe x O 4 (where M = Ni, Mn, Zn, x ≦ 2) A high density sintered magnetic body made of powder coated with a metal oxide magnetic material having a spinel composition is proposed.

さらに、特許文献2には、表面に超音波励起フェライトめっきによって形成されたフェライト層の被覆を有する金属または金属間化合物の強磁性体微粒子粉末が圧縮成形され、前記フェライト層を介して前記強磁性体粒子間に磁路を形成するものであることを特徴とする複合磁性材料が提案されている。   Further, in Patent Document 2, ferromagnetic fine particle powder of metal or intermetallic compound having a ferrite layer coating formed by ultrasonic excitation ferrite plating on the surface is compression-molded, and the ferromagnetic material powder is passed through the ferrite layer. There has been proposed a composite magnetic material characterized in that a magnetic path is formed between body particles.

高密度で、かつ、比抵抗が高い軟磁性成形体を得る方法として、軟磁性の金属粒子と、その表面に被覆された高抵抗物質と、該高抵抗物質の表面に被覆されたリン酸系化成処理被膜とよりなることを特徴とする軟磁性粒子が提案されている(例えば、特許文献3参照。)。   As a method for obtaining a soft magnetic molded body having a high density and a high specific resistance, soft magnetic metal particles, a high-resistance material coated on the surface thereof, and a phosphoric acid system coated on the surface of the high-resistance material Soft magnetic particles characterized by comprising a chemical conversion coating have been proposed (see, for example, Patent Document 3).

金属磁性材料の欠点である抵抗率を向上するために、飽和磁束密度および透磁率が高い軟磁性金属粒子の表面に、電気抵抗率の高い非磁性絶縁酸化物の被膜を形成した磁性材料が提案されている。この被膜形成軟磁性金属粒子を用いて得られる圧粉磁心は、非磁性絶縁膜の効果により電気抵抗率が向上することで渦電流を抑制できる、つまりMHz帯域などの高周波でも使用することができる。   In order to improve resistivity, which is a drawback of metal magnetic materials, magnetic materials with a nonmagnetic insulating oxide film with high electrical resistivity formed on the surface of soft magnetic metal particles with high saturation magnetic flux density and high permeability are proposed. Has been. The dust core obtained by using the film-formed soft magnetic metal particles can suppress eddy currents by improving the electrical resistivity due to the effect of the non-magnetic insulating film, that is, can be used at high frequencies such as MHz band. .

特開昭56−38402号公報JP-A-56-38402 国際公開第03/015109号パンフレットWO03 / 015109 pamphlet 特開2001−85211号公報JP 2001-85211 A

これらのこのような圧粉磁心は、その透磁率を向上させるために、通常、プレス成型後、熱処理を実施するが、主としてコスト面の問題から、大気中熱処理が行われる。しかし、大気中熱処理では大量に含まれる酸素によって圧粉磁心内の軟磁性金属粒子が酸化され飽和磁化量が低下し、それによって透磁率が低下してしまうという問題があった。
さらに、このような酸化物生成は特性バラツキを生じる要因にもなりうる。
In order to improve the magnetic permeability of these powder magnetic cores, heat treatment is usually performed after press molding, but heat treatment in the atmosphere is performed mainly due to cost problems. However, in the heat treatment in the atmosphere, there is a problem that the soft magnetic metal particles in the dust core are oxidized by oxygen contained in a large amount and the saturation magnetization amount is lowered, thereby lowering the magnetic permeability.
Furthermore, the generation of such an oxide can be a factor causing characteristic variations.

例えば、特許文献1や2で用いられているフェライト被膜は、900℃以上の温度で熱処理をしなければフェライトとしての特性がでないため、このような高温で熱処理をすることになる。このような高温で熱処理すると軟磁性金属粒子中の金属が拡散して被膜近傍に移動し、この金属が酸化されて酸化物が形成されるため酸化物膜厚が厚くなってしまう。   For example, since the ferrite film used in Patent Documents 1 and 2 does not have the properties of ferrite unless it is heat-treated at a temperature of 900 ° C. or higher, it is heat-treated at such a high temperature. When heat treatment is performed at such a high temperature, the metal in the soft magnetic metal particles diffuses and moves to the vicinity of the coating, and this metal is oxidized to form an oxide, so that the oxide film thickness becomes thick.

本発明の目的は、高周波特性に優れ、かつ、透磁性に優れた圧粉磁心を得ることのできる圧粉磁心の製造方法を提供することにある。   An object of the present invention is to provide a method of manufacturing a dust core that is capable of obtaining a dust core having excellent high-frequency characteristics and excellent permeability.

本発明の圧粉磁心の製造方法は、表面に絶縁酸化被膜を有する軟磁性金属粒子をプレス成型した後、酸素分圧1013Pa以下の雰囲気中で熱処理することを特徴とする。
前記雰囲気は不活性ガスであってもよく、酸素分圧1013Pa以下であれば酸素を含有する不活性ガスであってもよい。
前記不活性ガスとして窒素ガスを用いると、コスト面で有利となる。
前記雰囲気は酸素分圧1013Pa以下であれば真空雰囲気であってもよく、減圧下であってもよい。雰囲気の気圧が1013Paを超える場合は不活性ガスまたは分圧1013Pa以下の酸素を含有する不活性ガスが用いられる。
The method for producing a dust core according to the present invention is characterized in that soft magnetic metal particles having an insulating oxide film on the surface are press-molded and then heat-treated in an atmosphere having an oxygen partial pressure of 1013 Pa or less.
The atmosphere may be an inert gas, and may be an inert gas containing oxygen as long as the oxygen partial pressure is 1013 Pa or less.
Use of nitrogen gas as the inert gas is advantageous in terms of cost.
The atmosphere may be a vacuum atmosphere as long as the oxygen partial pressure is 1013 Pa or less, or may be under reduced pressure. When the atmospheric pressure exceeds 1013 Pa, an inert gas or an inert gas containing oxygen having a partial pressure of 1013 Pa or less is used.

本発明の圧粉磁心の製造方法においては、表面に絶縁酸化被膜を有する軟磁性金属粒子をプレス成形した後、熱処理するが、この熱処理により、軟磁性金属粒子中の金属が絶縁酸化被膜の方に拡散する。前記絶縁酸化被膜中における、絶縁酸化被膜を主に形成する酸化物の酸素以外の主成分の原子数に対する前記軟磁性金属粒子から拡散してきた軟磁性金属粒子の1つの主成分の原子数の比率が0.2以下であると、得られる圧粉磁心が高透磁率となるので好ましい。   In the method of manufacturing a dust core according to the present invention, soft magnetic metal particles having an insulating oxide film on the surface are press-molded and then heat-treated. By this heat treatment, the metal in the soft magnetic metal particles is the insulating oxide film. To spread. In the insulating oxide film, the ratio of the number of atoms of one main component of the soft magnetic metal particles diffused from the soft magnetic metal particles to the number of atoms of main components other than oxygen in the oxide that mainly forms the insulating oxide film Is preferably 0.2 or less, since the obtained dust core has high magnetic permeability.

軟磁性金属粒子が例えばパーマロイの場合、その主成分はFeまたはNiとなる。また、絶縁酸化被膜を形成する酸化物がSiO2の場合、酸化物の酸素以外の主成分はSiとなる。したがって、これらの成分を用いた場合には、SiO2被膜内におけるFe/SiまたはNi/Si原子数比率が0.2以下であることが好ましいことになる。 When the soft magnetic metal particles are, for example, permalloy, the main component is Fe or Ni. When the oxide that forms the insulating oxide film is SiO 2 , the main component other than oxygen in the oxide is Si. Therefore, when these components are used, it is preferable that the Fe / Si or Ni / Si atomic number ratio in the SiO 2 coating is 0.2 or less.

本発明の圧粉磁心の製造方法によれば、軟磁性金属粒子の酸化を防止し、高周波特性に優れ、かつ、高透磁率の圧粉磁心を得ることが可能になる。   According to the method for producing a dust core of the present invention, it is possible to prevent the soft magnetic metal particles from being oxidized, to obtain a dust core having excellent high frequency characteristics and high permeability.

本発明の圧粉磁心の製造方法においては、図1に示すような軟磁性金属粒子11の表面に絶縁酸化被膜12を有する絶縁酸化被膜付き軟磁性金属粒子1を用いる。   In the method for producing a dust core of the present invention, soft magnetic metal particles 1 with an insulating oxide film having an insulating oxide film 12 on the surface of soft magnetic metal particles 11 as shown in FIG. 1 are used.

本発明において用いられる軟磁性金属粒子11を構成する材料としては、例えば、鉄、コバルト、ニッケルなどの単金属、あるいはパーマロイ、センダストなどそれらを基とする合金などの透磁率が高い金属材料を挙げることができる。
軟磁性金属粒子11の粒径(球換算)は特に限定されるものではないが、1〜30μmであることが好ましい。
Examples of the material constituting the soft magnetic metal particles 11 used in the present invention include metal materials having high magnetic permeability such as single metals such as iron, cobalt and nickel, or alloys based on them such as permalloy and sendust. be able to.
The particle diameter (in terms of sphere) of the soft magnetic metal particles 11 is not particularly limited, but is preferably 1 to 30 μm.

軟磁性金属粒子11の表面を被覆する絶縁酸化被膜12としては、ガラス、シリカ、アルミナなどを挙げることができる。ガラスとしてはSiO2、B23、P25等を主成分とするガラスを挙げることができる。 Examples of the insulating oxide film 12 that covers the surface of the soft magnetic metal particles 11 include glass, silica, and alumina. Examples of the glass include glass containing SiO 2 , B 2 O 3 , P 2 O 5 or the like as a main component.

絶縁酸化被膜12の平均膜厚は圧縮成型後の成形体における絶縁酸化被膜が保たれることにより粒子間の電気抵抗を高めることができる厚さであれば特に限定されないが、5nm以上であることが好ましく、透磁率を高める観点および軟磁性金属材料の飽和磁化を低下させすぎない観点から、25nm以下であることが好ましい。   The average film thickness of the insulating oxide film 12 is not particularly limited as long as the insulating oxide film in the compact after compression molding is maintained, and the thickness can increase the electrical resistance between the particles. From the viewpoint of increasing the magnetic permeability and not reducing the saturation magnetization of the soft magnetic metal material too much, it is preferably 25 nm or less.

絶縁酸化被膜12がSiO2の場合、このSiO2被膜は水ガラス法で形成できる。
水ガラスは組成がNa20・xSiO2・nH20(x=2〜4)で、これを水に溶かした溶液はアルカリ性を示す。この溶液に軟磁性金属粒子11を入れ、酸を溶液に加えると加水分解してゲル状の珪酸(H2SiO3)が析出し、軟磁性金属粒子表面に付着する。この後、軟磁性金属粒子を乾燥させれば、表面に珪酸からなる絶縁酸化被膜12が成膜された軟磁性金属粒子11が得られる。珪酸膜の膜厚は、水ガラス水溶液の濃度で制御可能であり、25nm以下(5〜25nm)という薄い膜を再現性よく成膜できる。
また、SiO2以外の酸化物であっても、水ガラス法のような湿式被膜形成法で被膜を形成してもよく、乾式成膜法で成膜してもよい。
When the insulating oxide film 12 is SiO 2 , the SiO 2 film can be formed by a water glass method.
The composition of water glass is Na 2 0 · xSiO 2 · nH 2 0 (x = 2 to 4), and a solution obtained by dissolving this in water shows alkalinity. When the soft magnetic metal particles 11 are put into this solution and an acid is added to the solution, it is hydrolyzed and gel silicic acid (H 2 SiO 3 ) is precipitated and adheres to the surface of the soft magnetic metal particles. Thereafter, when the soft magnetic metal particles are dried, the soft magnetic metal particles 11 having the insulating oxide film 12 made of silicic acid formed on the surface are obtained. The film thickness of the silicate film can be controlled by the concentration of the water glass aqueous solution, and a thin film of 25 nm or less (5 to 25 nm) can be formed with good reproducibility.
Moreover, even if it is oxides other than SiO2, a film may be formed by the wet film formation method like the water glass method, and you may form into a film by the dry-type film-forming method.

本発明においては前記絶縁酸化被膜付き軟磁性金属粒子1をプレス成形する。
プレス成形方法としては、金型を用いて、例えば上下方向から加圧圧縮する一軸圧縮成形、圧縮圧延成形、電気絶縁性非磁性被膜を有する軟磁性粒子をゴム型などにつめて全方向から加圧圧縮する静圧圧縮成形、これらを温間で行う温間一軸圧縮成形、温間静圧圧縮成形(WIP)、熱間で行う熱間一軸圧縮成形および熱間静圧圧縮成形(HIP)などを用いることができる。
プレス圧力は軟磁性金属粒子11、絶縁酸化被膜12の材質によっても異なるが、1100〜1300MPaであることが好ましい。
In the present invention, the soft magnetic metal particles 1 with an insulating oxide film are press-molded.
As the press molding method, for example, uniaxial compression molding, compression-rolling molding, which compresses and compresses in the up-down direction, soft magnetic particles having an electrically insulating nonmagnetic coating are packed in a rubber mold or the like and added from all directions. Hydrostatic compression molding to compress, warm uniaxial compression molding to perform these in warm, warm static pressure compression molding (WIP), hot uniaxial compression molding to perform hot and hot static pressure compression molding (HIP), etc. Can be used.
The pressing pressure varies depending on the materials of the soft magnetic metal particles 11 and the insulating oxide film 12, but is preferably 1100 to 1300 MPa.

本発明においては、得られた圧粉成形体を熱処理する。熱処理することにより透磁率が高く(μ′(透磁率の実部)が大きく)、損失の小さい(μ″(透磁率の虚部)が小さい)成形体を得ることができる。熱処理の最高到達温度は470〜530℃、最高到達温度保持時間は0.5〜2時間であることが好ましい。最高到達温度が上記下限未満では熱処理効果が不十分となり易く、上記上限より高い温度では、絶縁被膜の絶縁性低下のために、周波数特性が悪化する。   In the present invention, the obtained green compact is heat-treated. By heat treatment, it is possible to obtain a molded article having high permeability (μ ′ (real part of magnetic permeability) is large) and low loss (small μ ″ (imaginary part of magnetic permeability)). It is preferable that the temperature is 470 to 530 ° C., and the maximum temperature holding time is 0.5 to 2 hours.If the maximum temperature is less than the above lower limit, the heat treatment effect tends to be insufficient, and if the temperature is higher than the above upper limit, the insulating film The frequency characteristics deteriorate due to the lowering of the insulation.

本発明においては、熱処理中の雰囲気における酸素分圧が1013Pa(0.01atm)以下である必要がある。もちろん酸素を全く含まない雰囲気であってもよい。酸素分圧が1013Paを超える雰囲気で熱処理を行うと、熱処理温度にもよるが、軟磁性金属粒子から絶縁酸化被膜12の内部あるいはその表面に拡散してきた軟磁性金属粒子の主成分が酸化されて透磁率の低い領域が形成され、このため圧粉磁心全体としても透磁率が低くなる。   In the present invention, the oxygen partial pressure in the atmosphere during the heat treatment needs to be 1013 Pa (0.01 atm) or less. Of course, an atmosphere containing no oxygen may be used. When heat treatment is performed in an atmosphere where the oxygen partial pressure exceeds 1013 Pa, depending on the heat treatment temperature, the main component of the soft magnetic metal particles diffusing from the soft magnetic metal particles into the insulating oxide film 12 or on the surface thereof is oxidized. A region having a low magnetic permeability is formed, so that the magnetic permeability of the entire powder magnetic core is lowered.

熱処理中の雰囲気における酸素分圧を1013Pa以下にする方法としては、雰囲気を構成する気体の主成分を不活性ガスとして、酸素分圧を1013Pa以下とする方法や、大気雰囲気を用い、酸素分圧が1013Pa以下となるまで減圧あるいは真空下におく方法を採用できる。もちろん、不活性ガスの使用と減圧とを併用してもよい。   As a method for setting the oxygen partial pressure in the atmosphere during the heat treatment to 1013 Pa or less, a method in which the main component of the gas constituting the atmosphere is an inert gas and the oxygen partial pressure is 1013 Pa or less, or an oxygen atmosphere is used. It is possible to employ a method in which the pressure is reduced or vacuumed until the pressure becomes 1013 Pa or less. Of course, you may use together use of inert gas, and pressure reduction.

このように、熱処理中の雰囲気における酸素分圧を1013Pa以下にすることで、絶縁酸化被膜12中において、絶縁酸化被膜12を形成する酸化物の酸素以外の主成分の原子数に対する軟磁性金属粒子11から拡散してきた軟磁性金属粒子11の1つの主成分の原子数の比率が0.2以下となるようにすることができる。この比率を0.2以下とすることで高透磁率の圧粉磁心を得ることができる。   Thus, by setting the oxygen partial pressure in the atmosphere during the heat treatment to 1013 Pa or less, the soft magnetic metal particles with respect to the number of atoms of main components other than oxygen of the oxide forming the insulating oxide film 12 in the insulating oxide film 12 The ratio of the number of atoms of one main component of the soft magnetic metal particles 11 diffusing from 11 can be made 0.2 or less. By setting this ratio to 0.2 or less, a dust core having a high magnetic permeability can be obtained.

例えば、絶縁酸化被膜12を形成する酸化物がSiO2であり、軟磁性金属粒子11がパーマロイである場合、上述のような熱処理により、絶縁酸化被膜12における、パーマロイの主成分であるFeやNiと絶縁酸化被膜12を形成する酸化物の酸素以外の主成分であるSiとの原子数比率Fe/SiやNi/Siが0.2以下となる場合には150程度の高透磁率を得ることが可能となる。 For example, when the oxide forming the insulating oxide film 12 is SiO 2 and the soft magnetic metal particles 11 are permalloy, Fe or Ni, which are the main components of permalloy in the insulating oxide film 12, are obtained by the heat treatment as described above. When the atomic ratio Fe / Si or Ni / Si of Si / the main component other than oxygen of the oxide forming the insulating oxide film 12 is 0.2 or less, a high magnetic permeability of about 150 is obtained. Is possible.

<実施例1>
本実施例では、軟磁性金属粒子11として水アトマイズ法にて作製したNi78Mo5Feパーマロイ(Niが75重量%、Moが5重量%、残りがFeからなるパーマロイ)粒子(平均粒径8μm)を用い、その表面に絶縁酸化被膜12としてSiO2被膜を水ガラス法で形成した。水ガラスの組成はNa2O・xSiO2・nH2O(x=2〜4)で、これを水に溶かした溶液はアルカリ性を示す。この水ガラス水溶液に軟磁性金属粒子11を入れ、塩酸を溶液に加え、pHをコントロールして加水分解してゲル状の珪酸(H2SiO3)を軟磁性金属粒子11表面に付着させた。この後、この軟磁性金属粒子11を乾燥させることでSiO2被膜を形成した。SiO2被膜の膜厚は、水ガラス水溶液の濃度を制御することにより、5nmに制御した。
<Example 1>
In this example, Ni78Mo5Fe permalloy (Ni is 75% by weight, Mo is 5% by weight, and the rest is made of Fe permalloy) particles (average particle diameter: 8 μm) produced by the water atomization method as the soft magnetic metal particles 11; A SiO 2 film was formed as an insulating oxide film 12 on the surface by a water glass method. The composition of water glass is Na 2 O.xSiO 2 .nH 2 O (x = 2 to 4), and a solution obtained by dissolving this in water shows alkalinity. Soft magnetic metal particles 11 were added to this aqueous water glass solution, hydrochloric acid was added to the solution, and the pH was controlled and hydrolysis was performed to attach gel-like silicic acid (H 2 SiO 3 ) to the surface of the soft magnetic metal particles 11. Thereafter, the soft magnetic metal particles 11 were dried to form a SiO 2 film. The film thickness of the SiO 2 film was controlled to 5 nm by controlling the concentration of the water glass aqueous solution.

上記で得た絶縁酸化被膜付き軟磁性金属粒子1をプレス成型した。プレス成型では、超硬合金製の金型に粒子1を充填し、一軸プレスにより内径3mmφ、外形8mmφ、高さ約0.5mmのリングコア形状に成型した。   The soft magnetic metal particle 1 with an insulating oxide film obtained above was press-molded. In press molding, a die made of cemented carbide was filled with particles 1 and formed into a ring core shape having an inner diameter of 3 mmφ, an outer diameter of 8 mmφ, and a height of about 0.5 mm by uniaxial pressing.

成型後、ガス置換が可能な電気炉にて熱処理をした実施した。不活性ガスとしては窒素ガスを用いた。圧粉磁心を電気炉内にセットし、炉内の空気をポンプで減圧し、その後窒素ガスを導入し、大気圧とした。また、炉内の酸素濃度が0.1%(分圧101.3Paに相当)になるように酸素ガスを若干導入することで調整した。熱処理条件は設定温度500℃、保持時間1時間とした。   After molding, heat treatment was performed in an electric furnace capable of gas replacement. Nitrogen gas was used as the inert gas. The dust core was set in an electric furnace, the air in the furnace was depressurized with a pump, and then nitrogen gas was introduced to achieve atmospheric pressure. Further, the oxygen concentration in the furnace was adjusted to 0.1% (corresponding to a partial pressure of 101.3 Pa) by slightly introducing oxygen gas. The heat treatment conditions were a set temperature of 500 ° C. and a holding time of 1 hour.

得られたリングコアに1次および2次巻線をそれぞれ5ターン巻回し、B−Hアナライザにて複素透磁率μ=μ’+μ”を10kHz〜10MHzの周波数領域で測定した。得られた透磁率μ’、μ”の周波数特性を図2に示す。
また、圧粉磁心の表面をESCAによって組成分析した結果を図3に示す。なお、図3の横軸Fe/Si原子数比率は、圧粉磁心の表面(絶縁酸化被膜)におけるSiに対するFeの原子数比率であり、ESCAによって得られたFeの割合(at%)をSiの割合(at%)で除して求めたものである。
The primary and secondary windings were wound around the obtained ring core for 5 turns, respectively, and the complex permeability μ = μ ′ + μ ″ was measured with a BH analyzer in a frequency range of 10 kHz to 10 MHz. The frequency characteristics of μ ′ and μ ″ are shown in FIG.
Moreover, the result of having analyzed the composition of the surface of the dust core by ESCA is shown in FIG. The abscissa Fe / Si atomic ratio in FIG. 3 is the atomic ratio of Fe to Si on the surface of the dust core (insulating oxide film), and the Fe ratio (at%) obtained by ESCA is Si. Divided by the ratio (at%).

<実施例2>
プレス成型した後の熱処理を、熱処理炉に真空チャンバーを有するものを使用して、減圧雰囲気(0.01Pa)で実施した以外は実施例1と同様にして、約0.5mmのリングコア形状の圧粉磁心を得た。得られたリングコアに1次および2次巻線をそれぞれ5ターン巻回し、B−Hアナライザにて複素透磁率μ=μ’+μ”を10kHz〜10MHzの周波数領域で測定した。得られた透磁率μ’、μ”の周波数特性を実施例1の結果と共に、図2に示す。
また、圧粉磁心の表面をESCAによって組成分析した結果を図3に示す。
<Example 2>
The heat treatment after press molding was carried out in a reduced pressure atmosphere (0.01 Pa) using a heat treatment furnace having a vacuum chamber, and the pressure of a ring core shape of about 0.5 mm was carried out in the same manner as in Example 1. A powder magnetic core was obtained. The primary and secondary windings were wound around the obtained ring core for 5 turns, respectively, and the complex permeability μ = μ ′ + μ ″ was measured with a BH analyzer in a frequency range of 10 kHz to 10 MHz. The frequency characteristics of μ ′ and μ ″ are shown in FIG. 2 together with the result of Example 1.
Moreover, the result of having analyzed the composition of the surface of the dust core by ESCA is shown in FIG.

<比較例1>
プレス成型した後の熱処理を、常圧の大気雰囲気で実施した以外は実施例1と同様にして、約0.5mmのリングコア形状の圧粉磁心を得た。得られたリングコアに1次および2次巻線をそれぞれ5ターン巻回し、B−Hアナライザにて複素透磁率μ=μ’+μ”を10kHz〜10MHzの周波数領域で測定した。得られた透磁率μ’、μ”の周波数特性を実施例1、2の結果と共に、図2に示す。
また、圧粉磁心の表面をESCAによって組成分析した結果を図3に示す。
<Comparative Example 1>
A powder core having a ring core shape of about 0.5 mm was obtained in the same manner as in Example 1 except that the heat treatment after press molding was performed in an atmospheric atmosphere at normal pressure. The primary and secondary windings were wound around the obtained ring core for 5 turns, respectively, and the complex permeability μ = μ ′ + μ ″ was measured with a BH analyzer in a frequency range of 10 kHz to 10 MHz. The frequency characteristics of μ ′ and μ ″ are shown in FIG. 2 together with the results of Examples 1 and 2.
Moreover, the result of having analyzed the composition of the surface of the dust core by ESCA is shown in FIG.

<比較例2>
プレス成型した後の熱処理を、常圧の下、炉内の酸素濃度を5%(分圧5065Paに相当)になるように調整した以外は実施例1と同様にして、約0.5mmのリングコア形状の圧粉磁心を得た。得られたリングコアに1次および2次巻線をそれぞれ5ターン巻回し、B−Hアナライザにて複素透磁率μ=μ’+μ”を10kHz〜10MHzの周波数領域で測定した。得られた透磁率μ’、μ”の周波数特性を実施例1、2、比較例1の結果と共に、図2に示す。
また、圧粉磁心の表面をESCAによって組成分析した結果を図3に示す。
<Comparative example 2>
A ring core of about 0.5 mm in the same manner as in Example 1 except that the heat treatment after press molding was adjusted so that the oxygen concentration in the furnace was 5% (corresponding to a partial pressure of 5065 Pa) under normal pressure. A dust core with a shape was obtained. The primary and secondary windings were wound around the obtained ring core for 5 turns, respectively, and the complex permeability μ = μ ′ + μ ″ was measured with a BH analyzer in a frequency range of 10 kHz to 10 MHz. The frequency characteristics of μ ′ and μ ″ are shown in FIG. 2 together with the results of Examples 1 and 2 and Comparative Example 1.
Moreover, the result of having analyzed the composition of the surface of the dust core by ESCA is shown in FIG.

図2から明らかなように、比較例1では、透磁率μ’が105程度であり、比較例2では115程度であった。一方、実施例1、実施例2ともにμ’は150程度であり、雰囲気の酸素濃度を低減し、軟磁性金属粒子の酸化を防止した効果が現れている。周波数5MHz以上ではμ’が低ドし、μ”が上昇し始めているが、1〜2MHz程度での使用には問題ない。   As is clear from FIG. 2, the magnetic permeability μ ′ was about 105 in Comparative Example 1 and about 115 in Comparative Example 2. On the other hand, in both Example 1 and Example 2, μ ′ is about 150, and the effect of reducing the oxygen concentration in the atmosphere and preventing the oxidation of the soft magnetic metal particles appears. At a frequency of 5 MHz or higher, μ ′ decreases and μ ″ begins to rise, but there is no problem in use at about 1 to 2 MHz.

図3から実施例1、2ではFe/SiやNi/Si原子数比率が0.2以下であるのに対し、比較例では0.8以上であることがわかる。パーマロイ粒子の構成元素であるFeやNiが酸化し、SiO2被膜内や被膜表面に拡散しているものと推測される。この結果から、Fe/SiやNi/Si原子数比率が0.2以下である場合には150程度の高透磁率を得ることが可能となる。 FIG. 3 shows that the Fe / Si and Ni / Si atomic ratios are 0.2 or less in Examples 1 and 2, but 0.8 or more in the comparative example. It is presumed that Fe and Ni, which are constituent elements of permalloy particles, are oxidized and diffused in the SiO 2 coating and on the coating surface. From this result, when the Fe / Si or Ni / Si atomic ratio is 0.2 or less, a high magnetic permeability of about 150 can be obtained.

本発明の製造方法によれば、軟磁性金属粒子の酸化を防止し、高透磁率の圧粉磁心を得ることができる。この圧粉磁心はスイッチング電源用トランス、リアクトルなどに用いるものとして有用である。   According to the production method of the present invention, it is possible to prevent the soft magnetic metal particles from being oxidized and obtain a dust core having a high magnetic permeability. The dust core is useful as a transformer for a switching power supply, a reactor, and the like.

絶縁酸化被膜付き軟磁性金属粒子を示した模式図である。It is the schematic diagram which showed the soft-magnetic metal particle with an insulating oxide film. 各実施例、比較例で得た圧粉磁心の周波数特性を示した図である。It is the figure which showed the frequency characteristic of the powder magnetic core obtained by each Example and the comparative example. 各実施例、比較例で得た圧粉磁心の透磁率μ’とFe/Si原子数比率を示した図である。It is the figure which showed permeability (micro | micron | mu) 'and Fe / Si atomic ratio of the powder magnetic core obtained by each Example and the comparative example.

符号の説明Explanation of symbols

1 絶縁酸化被膜付き軟磁性金属粒子
11 軟磁性金属粒子
12 絶縁酸化被膜
DESCRIPTION OF SYMBOLS 1 Soft magnetic metal particle with insulating oxide film 11 Soft magnetic metal particle 12 Insulating oxide film

Claims (6)

表面に絶縁酸化被膜を有する軟磁性金属粒子をプレス成型した後、酸素分圧1013Pa以下の雰囲気中で熱処理することを特徴とする圧粉磁心の製造方法。   A method for producing a powder magnetic core, comprising: press-molding soft magnetic metal particles having an insulating oxide film on a surface thereof, and then performing heat treatment in an atmosphere having an oxygen partial pressure of 1013 Pa or less. 前記雰囲気が不活性ガスまたは酸素含有不活性ガスであることを特徴とする請求項1記載の圧粉磁心の製造方法。   2. The method of manufacturing a dust core according to claim 1, wherein the atmosphere is an inert gas or an oxygen-containing inert gas. 前記不活性ガスが窒素ガスであることを特徴とする請求項2記載の圧粉磁心の製造方法。   The method of manufacturing a dust core according to claim 2, wherein the inert gas is nitrogen gas. 前記酸素分圧1013Pa以下の雰囲気中での熱処理が減圧または真空雰囲気での熱処理であることを特徴とする請求項1または2に記載の圧粉磁心の製造方法。   The method for producing a dust core according to claim 1 or 2, wherein the heat treatment in an atmosphere having an oxygen partial pressure of 1013 Pa or less is a heat treatment in a reduced pressure or vacuum atmosphere. 前記絶縁酸化被膜における、前記絶縁酸化被膜を主に形成する酸化物の酸素以外の主成分の原子数に対する、前記軟磁性金属粒子から拡散してきた軟磁性金属粒子の1つの主成分の原子数の比率が0.2以下であることを特徴とする請求項1〜4のいずれか1項に記載の圧粉磁心の製造方法。   In the insulating oxide film, the number of atoms of one main component of the soft magnetic metal particles diffused from the soft magnetic metal particles with respect to the number of atoms of main components other than oxygen of the oxide mainly forming the insulating oxide film The method according to any one of claims 1 to 4, wherein the ratio is 0.2 or less. 前記絶縁酸化被膜を形成する酸化物がSiO2であり、前記軟磁性金属粒子がパーマロイであることを特徴とする請求項5記載の圧粉磁心の製造方法。 The oxide forming the insulating oxide film is SiO 2, the manufacturing method of the dust core according to claim 5, wherein said soft magnetic metal particles are permalloy.
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