JP4688029B2 - Core for common mode choke coil and manufacturing method thereof - Google Patents

Description

  The present invention relates to a core for a common mode choke coil in which a wound core of a nanocrystalline alloy ribbon is impregnated with a resin and a method for manufacturing the same.

  With the progress of high performance of semiconductor switching elements, switching power supplies and inverter devices are rapidly spreading. In particular, the development of high-power semiconductor switching elements, such as IGBTs, that are capable of high-frequency operation has led to the rapid increase in frequency of high-capacity inverter devices, including low-noise inverter devices that have switching frequencies above the upper limit of the audible frequency band. It is being However, with the widespread use of such switching power supplies and high-frequency inverter devices, high-frequency noise generated by the switching operation of the semiconductor switching elements of these devices is transmitted to other electronic devices connected to the same power supply line via the power supply line. There is a problem that gives an obstacle. For this reason, in order to suppress high-frequency noise propagated from the device that performs such a switching operation to the power supply line side, for example, a noise filter having a circuit configuration as shown in FIG. Inserted between lines. These noise filters also have a function of preventing high-frequency noise from entering the apparatus from the power line and causing the apparatus to malfunction.

  FIG. 7 shows a circuit configuration of a noise filter for a single phase, in which 31 and 32 are input terminals connected to the power supply line, 33 and 35 are capacitors between the power supply lines, 34 is a common mode choke coil, and 36 and 37 Is a capacitor between the power line and the ground, 38 is a resistance between the power lines, and 39 and 40 are output terminals connected to the apparatus. Depending on the application, the input and output can be connected in reverse.

  The common mode choke coil is formed by winding a single-phase or three-phase conductor around an annular magnetic core (FIG. 5 is an example of single-phase winding). Conventionally, the magnetic core has been formed of Mn—Zn ferrite, a dust core, an Fe-based amorphous alloy, a Co-based amorphous alloy, or the like. The magnetic core used for the core for the common mode choke coil desirably has a high relative permeability and a high saturation magnetic flux density, but the above materials are not always satisfactory in that respect. Therefore, a noise filter having a common mode choke coil using such a material as a magnetic core is not sufficient in its characteristics, and is used today in multistage connection, so that it is required to increase the size of the noise filter. And miniaturization was not achieved sufficiently.

Patent Document 1 and Patent Document 2 disclose a core for a common mode choke coil using a fine core (trade name), which is an alloy developed by Hitachi Metals Co., Ltd., as a magnetic core that can be changed to the above-mentioned materials. It is described that the magnetic susceptibility and saturation magnetic flux density are obtained, and the common mode choke coil and the noise filter can be increased in frequency and size.
JP-A-8-115830 Japanese Patent Laid-Open No. 10-172841

  The impedance value of the common mode choke coil is a target of specification, but in addition, the reliability of impedance due to changes with time is also emphasized. As one of the reliability tests, a high temperature storage test is performed. This is to measure the impedance by exposing to a high temperature of 130 ° C. for 1000 hours assuming the amount of heat generated during mounting. In many cases, the change in impedance over time by this test is about -20% as a specification. In addition, since the nanocrystalline soft magnetic alloy ribbon becomes brittle during the heat treatment for nanocrystallization, the wound magnetic core may be impregnated with a resin in order to improve mechanical properties. At this time, it was found that the impedance of the wound magnetic core may not satisfy the above specifications because the nanocrystalline alloy ribbon is distorted when impregnated with resin.

  Accordingly, an object of the present invention is to solve the above problems, a method for producing a core for a common mode choke coil which is subjected to a heat treatment that does not cause a drop in impedance even when impregnated with a resin, and has a low drop in impedance even in a high-temperature storage test, and It is to provide a core and a coil for a common mode choke coil manufactured by the above.

As a result of the study by the present inventors, the required impedance value and the reliability due to the change in impedance over time can be obtained by setting the oxygen concentration in the heat treatment atmosphere within a predetermined range in the heat treatment step of nanocrystallization. I understood that.
That is, the present invention has the general formula: (Fe _1-a M _a ) _{100-x-yz-α-β-γ} Cu _x Si _y B _z M ′ _α M ″ _β X _γ (atomic%) , M is Co and / or Ni, M ′ is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, and M ″ is V, Cr, Mn, Al , White metal element, Sc, Y, rare earth element, at least one element selected from the group consisting of Au, Zn, Sn, Re, X is from C, Ge, P, Ga, Sb, In, As, Be A, x, y, z, α, β and γ are 0 ≦ a <0.1, 0.1 ≦ x ≦ 3, 14 ≦ y ≦ 20, respectively. , 5 ≦ z ≦ 7,2 ≦ α ≦ 5,0 ≦ β satisfy ≦ 10 and 0 ≦ γ ≦ 10.) the Fe-based nanocrystalline alloy having a composition represented A method of manufacturing a common mode choke core coil in winding core is impregnated with resin comprising strip, said the alloy ribbons wound with winding core, in said winding core oxygen concentration below 25ppm or 45ppm atmosphere, A method of manufacturing a core for a common mode choke coil, wherein a heat treatment for nanocrystallization is performed at a temperature of 550 ° C. or more and 600 ° C. or less , and a wound magnetic core subjected to the heat treatment is impregnated with a resin.

Further, the present invention provides a general formula: (Fe _1-a M _a ) _{100-xyz-α-β-γ} Cu _x Si _y B _z M ’ _α M ” _β X _γ (Atom%) (where M is Co and / or Ni, M ′ is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, and M ″ is V , Cr, Mn, Al, white metal element, Sc, Y, rare earth element, at least one element selected from the group consisting of Au, Zn, Sn, Re, X is C, Ge, P, Ga, Sb, A, x, y, z, α, β, and γ are 0 ≦ a <0.1, 0.1 ≦ x ≦ 3, respectively, which are at least one element selected from the group consisting of In, As, and Be. 14 ≦ y ≦ 20, 5 ≦ z ≦ 7, 2 ≦ α ≦ 5, 0 ≦ β ≦ 10 and 0 ≦ γ ≦ 10). And the winding core is 550 ° C. or more and 600 ° C. or less in an atmosphere having an oxygen concentration of 25 ppm or more and 45 ppm or less. A core for a common mode choke coil in which a heat treatment for nanocrystallization is performed and then a heat-treated core is impregnated with resin, and the impedance change rate at 100 kHz before and after resin impregnation is less than 10%. Is a core for a common mode choke coil.

  When the amorphous alloy ribbon having the above composition is used for the heat treatment for nanocrystallization, the heat treatment temperature for nanocrystallization is preferably 550 ° C to 600 ° C. Furthermore, it is preferable to heat-process in the range of 580 degreeC-595 degreeC. By performing heat treatment at this temperature, it is possible to obtain a nanocrystalline alloy ribbon having a magnetostriction that is almost zero, and it is possible to obtain a material that does not have a decrease in impedance even when the wound core is impregnated with resin.

The core for a common mode choke coil obtained by impregnating a wound magnetic core made of a nanocrystalline alloy ribbon obtained by the above manufacturing method with an initial value has an impedance at 100 kHz after a high-temperature storage test of 130 ° C. × 800 hours. It is characterized by a change rate of less than 10% with respect to the impedance.

  As the resin to be used, an epoxy resin or an acrylic resin can be used as appropriate. The capacity of the resin solvent used when impregnating these resins is about 5 wt% to 40 wt% with respect to the weight of the resin. As will be described later, the capacity of the solvent affects the impedance of the core for the common mode choke coil after being impregnated with the resin. When the amount of the resin solvent is more than 20 wt%, there is an effect of suppressing a decrease in impedance due to resin impregnation when measured at a low frequency (1 kHz or more and less than 50 kHz). Further, when the amount of the resin solvent is 20 wt% or less, there is an effect of suppressing a decrease in impedance due to resin impregnation when measured at a high frequency (50 kHz or more and less than 500 kHz).

  As described above, a core for a common mode choke coil in which a soft magnetic alloy ribbon is wound into a magnetic core, the soft magnetic alloy ribbon is nanocrystallized by heat treatment, and impregnated with resin, there is no deterioration of impedance over time and reliability. It was possible to provide a high-performance product and a method for producing the same.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

  The Fe-based soft magnetic alloy used in the magnetic core according to the present invention is obtained by a step of obtaining an amorphous alloy having a predetermined composition by quenching from a molten metal and a heat treatment step of heating the amorphous alloy to form fine crystal grains. . Analysis by X-ray diffraction and transmission electron microscope reveals that fine crystal grains are Fe of a body-centered cubic lattice structure in which Si or the like is dissolved. Fine crystal grains are those having an average grain size of 200 angstroms or less with the largest dimension having a body-centered cubic lattice structure and crystal grains occupying at least 80% of the structure. Portions other than fine crystal grains in the alloy structure are mainly amorphous. Note that the magnetic core of the present invention exhibits sufficiently excellent magnetic properties even when the proportion of fine crystal grains is substantially 100%.

  In the alloy used in the present invention, Cu is contained in the range of 0.1 to 3 atomic%. If it is less than 0.1 atomic%, there is almost no effect of decreasing core loss and increasing magnetic permeability due to the addition of Cu. On the other hand, if it exceeds 3 atomic%, the core loss may be larger than that without adding, and the magnetic permeability is also deteriorated. To do. Particularly preferable Cu content x in the present invention is 0.5 to 2 atomic%, and the core loss is particularly small in this range. The cause of the Cu core loss reduction and permeability increase is not clear, but is thought to be as follows. Since the interaction parameters of Cu and Fe are positive, the solid solubility is low, and there is a tendency to separate, when an amorphous alloy is heated, Fe atoms or Cu atoms come together to form a cluster, resulting in composition fluctuations. Occurs. For this reason, a large number of regions that are easily crystallized are formed, and fine crystal grains having the cores are generated. This crystal is mainly composed of Fe, and there is almost no solid solubility of Fe and Cu, so that Cu is expelled around fine crystal grains by crystallization, and the Cu concentration around the crystal grains becomes high. For this reason, it is considered that the crystal grains are difficult to grow.

  As described above, it is thought that crystal grain refinement occurs due to the large number of crystal nuclei formed by Cu addition and the difficulty of growing crystal grains, but this action is due to the presence of Nb, Ta, W, Mo, Zr, Hf, Ti, etc. This is considered to be particularly remarkable. In the absence of Nb, Ta, W, Mo, Zr, Hf, Ti, etc., the crystal grains are not very refined. Nb, Ta, Zr, Hf, and Mo are particularly effective. However, when Nb is added among these elements, the crystal grains are particularly likely to be thin, and excellent soft magnetic properties can be obtained. In addition, since a fine crystalline phase mainly composed of Fe is generated, magnetostriction is smaller than that of Fe-based amorphous alloys, and magnetic anisotropy due to internal stress-strain is also reduced. It is done.

As an Fe-based soft magnetic alloy related to the magnetic core of the present invention, in order to prevent a decrease in impedance due to resin impregnation, magnetostriction is negative, particularly like an alloy represented by the composition formula: Fe _bal Cu ₁ Nb ₃ B ₅ Si _17.5. And those having a magnetostriction of 0 or almost zero are preferred.

  Elements such as V, Cr, Mn, Al, white metal elements, Sc, Y, rare earth elements, Au, Zn, Sn, and Re have effects of improving corrosion resistance, improving magnetic properties, and adjusting magnetostriction. Its content is at most 10 atomic% or less. This is because when the content exceeds 10 atomic%, the saturation magnetic flux density is significantly lowered, and the particularly preferable content is 8 atomic% or less. Among these, a magnetic core having particularly excellent corrosion resistance and wear resistance is obtained when it is made of an alloy to which at least one element selected from Ru, Rh, Pd, Os, Ir, Pt, Au, Cr, and V is added.

  In the present invention, at least one element selected from the group consisting of C, Ge, P, Ga, Sb, In, Be, and As may be contained in an amount of 10 atomic% or less. These elements are effective elements for amorphization, and adding them together with Si and B helps to amorphize the alloy and is effective in adjusting magnetostriction and Curie temperature.

  Si and B are particularly useful elements for grain refinement of the alloy according to the present invention. The Fe-based soft magnetic alloy according to the present invention is preferably obtained by once forming an amorphous alloy by the effect of addition of Si and B and then forming fine crystal grains by heat treatment. If the Si and B contents are too high, there is a significant decrease in the saturation flux density of the alloy.

  In the present invention, M ′ has an effect of refining crystal grains precipitated by complex addition with Cu, and is at least one selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo. Elements. Nb and the like have the effect of increasing the crystallization temperature of the alloy, but it is considered that the crystal grains precipitated by the interaction with Cu having the function of forming clusters and lowering the crystallization temperature are refined. Further, in order to reduce magnetostriction, the content α of M ′ is 2 to 5 atomic% from the relationship with other additive elements.

  The balance is substantially composed mainly of Fe except for impurities, but a part of Fe may be replaced by the component M (Co and / or Ni). The content a of M is 0 ≦ a <0.5, but preferably 0 ≦ a ≦ 0.3. This is because core loss may increase when a exceeds 0.3.

  Addition of M "can improve corrosion resistance, magnetic properties, or magnetostriction adjustment effect. When M" exceeds 10 atomic%, the saturation magnetic flux density is significantly reduced.

  Next, the manufacturing method of the magnetic core of this invention is demonstrated. First, a ribbon-like amorphous alloy is formed from a molten metal having a predetermined composition by a known liquid quenching method such as a single roll method or a twin roll method. Usually, the plate thickness of the amorphous alloy ribbon produced by the single roll method or the like is about 3 to 100 μm, but a plate thickness of 25 μm or less is particularly suitable as a thin ribbon for a magnetic core used at a high frequency. This amorphous alloy may contain a crystalline phase, but is desirably amorphous in order to uniformly produce fine crystal grains by a subsequent heat treatment. The thin ribbon is wound around so that the space factor becomes 70% to 90% and magnetically cored.

  The heat treatment is performed by holding the amorphous alloy ribbon processed into a predetermined shape for a certain period of time in an inert gas atmosphere of hydrogen, nitrogen, Ar or the like having an oxygen concentration of 20 to 100 ppm. When the oxygen concentration is less than 20 ppm, an oxide film is not formed on the surface of the ribbon having the above composition, and the impedance decreases due to the influence of magnetostriction due to resin impregnation, Oxidation progresses, and stable impedance characteristics cannot be obtained, resulting in deterioration over time. The impedance of the nanocrystalline alloy ribbon having the above composition is higher than the required impedance value of the core for a common mode choke coil. Therefore, although the impedance is slightly reduced due to the oxidation of the ribbon surface, the required specifications are satisfied, and since the surface is oxidized, the change over time is extremely small and the reliability is high for common mode choke coils. A core is obtained. On the other hand, when the oxygen concentration exceeds 100 ppm, the impedance is too low to satisfy the required specifications. A more preferable oxygen concentration in the heat treatment furnace is 22 to 50 ppm, and a more preferable oxygen concentration is 25 to 45 ppm.

  The heat treatment holding temperature for nanocrystallization of the soft magnetic alloy ribbon obtained by roll cooling the composition is preferably 550 ° C to 600 ° C. When the temperature is lower than 550 ° C. or higher than 600 ° C., magnetostriction is increased, which is not preferable. The holding time is preferably about 5 minutes to 24 hours. As for heat treatment time, it is difficult to bring the entire processed alloy to a uniform temperature if the heat treatment time is less than 5 minutes, and magnetic characteristics are likely to vary, and if it is longer than 24 hours, not only productivity will deteriorate but also excessive growth of crystal grains will occur. In addition, the generation of crystal grains having a non-uniform shape tends to cause a decrease in magnetic properties. Preferable heat treatment conditions are 585 ° C. to 595 ° C. for 5 minutes to 6 hours in consideration of practicality and uniform temperature control.

  The heat treatment can also be performed in a magnetic field such as direct current or alternating current. Furthermore, magnetic anisotropy can be produced in the alloy used in the magnetic core by heat treatment in a magnetic field to improve the characteristics. The magnetic field may be applied during the heat treatment, but it is not necessary to apply it for the entire period, and a sufficient effect can be obtained at a temperature lower than the Curie temperature Tc of the alloy. Further, the heat treatment is not limited to one step, and a multi-step heat treatment or a plurality of heat treatments can be performed.

Example 1
An amorphous soft magnetic alloy ribbon having a composition of Fe74Cu1Nb3Si17B5, a thickness t of 22 μm, and a width of 25 mm is manufactured by liquid quenching using a single roll, and then the amorphous soft magnetic alloy ribbon is slit to a width of 20 mm. The ribbon was obtained. Using an amorphous soft magnetic alloy ribbon having a width of 20 mm, the outer diameter 37 is obtained by setting the space factor K expressed by Ae / A, which is the ratio of the apparent sectional area A and the effective sectional area Ae of the wound core, to 75%. A wound magnetic core having a diameter of .17 mm and an inner diameter of 28.1 mm was produced.

  This wound magnetic core was put into a nitrogen atmosphere furnace, and the oxygen concentration in the furnace was changed to 5, 10, 15, 25, 35, 50 ppm, and nanocrystallization heat treatment was performed under each condition. The holding temperature was 585 ° C. and the holding time was 1 hour. Thereafter, it was left to cool for 48 hours, and the impedance of the obtained sample at frequencies of 10 kHz and 100 kHz was measured. The measurement was performed using Agilent 4194A as a measuring instrument. The measurement conditions were Ave16. The results are shown in FIG. In addition, this wound magnetic core is impregnated with a solution in which an epoxy resin of a product name EOCN-102S (manufactured by Nippon Kayaku Co., Ltd.) and an epoxy resin of a product name EPIKURE171 (manufactured by Japan Epoxy Resin Co., Ltd.) and a curing agent are mixed to 30 wt% with acetone. It was. For the impregnation of the resin, the resin was immersed in the impregnating solution for 1 minute, taken out, left in the atmosphere for 1 minute, and placed in a drying furnace maintained at 150 ° C. for 15 minutes to cure the resin. With the resin impregnated, impedance was measured in the same manner as described above. The rate of change between the impedance of the wound magnetic core before impregnation with the resin obtained in FIG. 1 and the impedance after impregnation with the resin was examined. The results are shown in FIG.

As can be seen from FIG. 1, when the influence of residual magnetostriction on the wound magnetic core due to impregnation with resin is observed, characteristic changes occur in both frequency ranges of 10 kHz and 100 kHz. The impedance frequency characteristic has a small change at 10 kHz and a large change at 100 kHz. From this, it can be inferred that the impedance change factor is not the one in which the magnetostriction residual is uniformly affected. Although not shown in the figure, it was found that when heat treatment was similarly performed in an atmosphere in which the oxygen concentration exceeded 100 ppm, the impedance was significantly reduced and the magnetic characteristics were insufficient with respect to the specifications.
As seen from FIG. 2, the variation in characteristics depending on the oxygen concentration is not significantly affected at 10 kHz, but the heat treatment at an oxygen concentration of 15 ppm or less at 100 kHz has a large variation in characteristics and a large change rate. I understand that.

(Example 2)
The core for the common mode choke coil manufactured according to the present invention was wound and subjected to a high temperature storage test to confirm the reliability due to the change with time. A wound magnetic core is manufactured in the same manner as in Example 1, this wound magnetic core is inserted into a 15% glass frit PBT resin case, fixed with a vise, and wound under the conditions of manual winding by an operator. With the stress applied, heat treatment for nanocrystallization was performed to obtain a common mode talk coil. The oxygen concentration in the heat treatment furnace was 5 ppm and 35 ppm. In the high-temperature storage test, the impedance of the common mode talk coil was measured after 24, 100, 250, 500, 800, and 1000 hours when left in a high-temperature bath (130 ° C. air atmosphere). The measurement was performed after taking out from the high temperature bath and cooling to room temperature over 48 hours.

FIG. 3 shows the results when winding was performed on a core for a common mode talk coil that had been nanocrystallized in an oxygen concentration of 5 ppm and 35 ppm in a heat treatment furnace, a high-temperature storage test was performed, and measurement was performed at 10 kHz. FIG. 4 shows the results when a high-temperature storage test was conducted in the same manner and measured at 100 kHz.
When used at 10 kHz, the decrease in impedance has no significant effect, but when used at 100 kHz, a significant difference is observed when the heat treatment for nanocrystallization is performed at oxygen concentrations of 5 ppm and 35 ppm. Nanocrystal crystallization heat treatment at an oxygen concentration of 35 ppm results in a highly reliable common mode talk coil core and coil with little change in impedance over time even when placed in a harsh environment for a long time in a high temperature storage test. I understood that

(Example 3)
In order to see the effect of the viscosity of the resin when impregnated, the high temperature storage test was conducted in the same manner as in Example 2 by comparing both the case where the solvent was used at 10 wt% and the case where 30 wt% was used with respect to the weight of the epoxy resin. went.
The rate of change from the impedance of the common mode talk coil measured before the high temperature storage test was measured. Nanocrystallization was performed with the oxygen concentration in the heat treatment furnace being 35 ppm, and the impedances at 10 kHz and 100 kHz were examined. The results are shown in FIG.
It was found that when the solvent was used at 10 wt% with respect to the weight of the epoxy resin, the rate of change at 100 kHz was small, and conversely, when the solvent was used at 30 wt%, the rate of change at 10 kHz was small.

(Comparative example)
A wound magnetic core was prepared in the same manner as in Example 1, and nanocrystallization was performed with an oxygen concentration in the heat treatment furnace of 5 ppm. This wound magnetic core was subjected to a high-temperature storage test in the same manner as in Example 2 to examine the impedance at 100 kHz. The results are shown in FIG.
It was found that a change rate of 10% or less appeared in the impedance after 250 hours of high-temperature storage test, and after 800 hours, more than half became a change rate of 10% or less.

It is the figure which measured the influence of the impedance of the winding magnetic core by oxygen concentration. It is the figure which measured the rate of change of the impedance before and behind impregnating a winding magnetic core with resin. It is the figure which measured the influence of the impedance by a high temperature storage test. It is the figure which measured the influence of the impedance by a high temperature storage test. It is the figure which measured the change rate of the impedance by a high temperature storage test. It is the figure which measured the change rate of the impedance by a high temperature storage test. It is an example of a circuit diagram in which a common mode choke coil is used

Explanation of symbols

31, 32: Input terminal, 33, 35: Capacitor, 34: Common mode choke coil, 36, 37: Capacitor between power line and ground, 38: Resistance between power line, 39, 40 output terminal

Claims (4)

General formula: (Fe _1-a M _a ) _{100-xyz-α-β-γ} Cu _x Si _y B _z M ′ _α M ″ _β X _γ (atomic%) (where M is Co and / or Or M ′ is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, M ″ is V, Cr, Mn, Al, a white metal element, Sc , Y, rare earth elements, at least one element selected from the group consisting of Au, Zn, Sn, Re, X is selected from the group consisting of C, Ge, P, Ga, Sb, In, As, and Be A, x, y, z, α, β, and γ are 0 ≦ a <0.1, 0.1 ≦ x ≦ 3, 14 ≦ y ≦ 20, and 5 ≦ z ≦ 7, respectively. , 2 ≦ α ≦ 5,0 ≦ β ≦ 10 and 0 ≦ gamma satisfy ≦ 10.) wound magnetic of Fe-based nano-crystalline alloy ribbon having a composition represented by A method of manufacturing a core for the common mode choke coil impregnated with resin, wherein the alloy ribbons wound with winding core, in said winding core oxygen concentration 25ppm or 45ppm or less of the atmosphere, 600 ° C. 550 ° C. or higher A method for producing a core for a common mode choke coil, comprising: performing heat treatment for nanocrystallization, and impregnating a resin into a wound magnetic core subjected to the heat treatment. General formula: (Fe _1-a M _a ) _{100-xyz-α-β-γ} Cu _x Si _y B _z M ’ _α M ” _β X _γ (Atom%) (where M is Co and / or Ni, M ′ is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, and M ″ is V , Cr, Mn, Al, white metal element, Sc, Y, rare earth element, at least one element selected from the group consisting of Au, Zn, Sn, Re, X is C, Ge, P, Ga, Sb, A, x, y, z, α, β, and γ are 0 ≦ a <0.1, 0.1 ≦ x ≦ 3, respectively, which are at least one element selected from the group consisting of In, As, and Be. 14 ≦ y ≦ 20, 5 ≦ z ≦ 7, 2 ≦ α ≦ 5, 0 ≦ β ≦ 10 and 0 ≦ γ ≦ 10). And the winding core is 550 ° C. or more and 600 ° C. or less in an atmosphere having an oxygen concentration of 25 ppm or more and 45 ppm or less. A core for a common mode choke coil in which a heat treatment for nanocrystallization is performed and then a heat-treated core is impregnated with resin, and the impedance change rate at 100 kHz before and after resin impregnation is less than 10%. Core for common mode choke coils.
General formula: (Fe _1-a M _a ) _{100-xyz-α-β-γ} Cu _x Si _y B _z M ′ _α M ″ _β X _γ (atomic%) (where M is Co and / or Or M ′ is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, M ″ is V, Cr, Mn, Al, a white metal element, Sc , Y, rare earth elements, at least one element selected from the group consisting of Au, Zn, Sn, Re, X is selected from the group consisting of C, Ge, P, Ga, Sb, In, As, and Be A, x, y, z, α, β, and γ are 0 ≦ a <0.1, 0.1 ≦ x ≦ 3, 14 ≦ y ≦ 20, and 5 ≦ z ≦ 7, respectively. , 2 ≦ α ≦ 5, 0 ≦ β ≦ 10, and 0 ≦ γ ≦ 10)). And, in the winding core oxygen concentration 25ppm or 45ppm or less of the atmosphere, subjected to a heat treatment for nanocrystallized at 550 ° C. or higher 600 ° C. or less, common mode choke was then heat-treated resin-impregnated wound magnetic core was a core coils, common mode choke core coil, wherein the impedance at 100kHz after the high temperature storage test 1 30 ° C. × 800 hours is the rate of change of less than 10% with respect to the impedance of the initial value . 4. The core for a common mode choke coil according to claim 2, wherein the resin is an epoxy resin.

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