JPH0645128A - Magnetic core comprising ultra-fine crystalline alloy excellent in dc-superimposed characteristic and manufacturing method thereof, and choke coil and transformer using the core - Google Patents

Abstract

PURPOSE:To obtain the title magnetic core having excellent DC-superimposed characteristics at low magnetic core loss by making use of ultra-fine crystalline alloy having crystalline particles in specific particle diameter and residual flux density. CONSTITUTION:Within the title choke coil, transformer, an ultra-fine crystalline alloy wherein at least 50% of the structure thereof is held by crystalline particles in particle diameter not exceeding 500Angstrom as well as residual flux density not exceeding 7000G and the density at 10Oe not exceeding 7000G is used as the title magnetic core. This magnetic core displays the characteristics thereof fit for a transformer or normal mode choke when the residual flux density and the flux density at 10Oe does not exceed 7000G. Besides, it recommended that the mean particle diameter does not exceed 300Angstrom . It is also required that the ratio of crystalline particles exceeds 50% of the structure and if it does not exceed 50%, the magnetostriction is intensified to start humming in audio-frequency. Through these procedures, the title ultra-fine crystalline alloy having excellent DC-superimposed characteristics at low magnetic core loss can be obtained thereby enabling the effect on a choke coil and transformer using the same to be notably enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high frequency transformer and a node.
The present invention relates to a magnetic core using an alloy having an ultrafine grain structure excellent in high-frequency magnetic characteristics excellent in DC superposition characteristics used in a malmode choke coil, a manufacturing method thereof, a choke coil and a transformer using the same.

[0002]

2. Description of the Related Art As a magnetic core material used for a high frequency transformer, a smooth choke, a normal mode choke for a noise filter, etc., a material having excellent DC superposition characteristics is used because it is less likely to damage circuit components due to magnetic saturation. It is preferred because it can increase the magnetic flux density and can obtain high incremental magnetic permeability in the state where DC is superposed. In a high frequency transformer, a circuit element is destroyed when the magnetic core is magnetically saturated, so that a cut core is often used. The cut core is also preferred because of its ease of winding.
Usually, in order to obtain characteristics suitable for such applications, a method is used in which a gap is formed in the case of a metal material or a powder magnetic core is used to reduce the slope of the BH curve to improve the DC superposition characteristics. ing. The DC superposition characteristic is a dependency of the incremental magnetic permeability μΔ on the DC superposition magnetic field H _DC , and it is desirable that μΔ is as high as possible with respect to H _DC . Roh - Malmö - Docho - it is necessary to sufficiently high μ △ even for more H _DC 10Oe as a click. As materials suitable for the above applications, high saturation magnetic flux density materials such as silicon steel and Fe-based amorphous alloys, and ferrites and permalloy powder magnetic cores having excellent high frequency magnetic characteristics are used.

[0003]

However, silicon steel and Fe
Amorphous base alloys and the like have a large magnetic core loss, which causes a problem of a large temperature rise and a problem of reduced efficiency. In addition, it is necessary to form a gap or use a cut core in order to improve the direct current superposition characteristic during use. Therefore, there is a problem that the leakage of the magnetic flux from the gap portion or the joint portion affects the peripheral devices and the magnetic core loss increases due to the eddy current caused by the leakage magnetic flux. Further, the Fe-based amorphous alloy has remarkably large magnetostriction, and there is a problem that resonance occurs due to magnetostriction depending on the frequency and the characteristics change, and a beat occurs when used in the audible frequency band. Further, there is still a problem that the core loss is larger than that of Co-based amorphous and ferrite, and the heat generation is large. On the other hand, ferrite and permalloy powder magnetic cores have a problem that the DC superposition characteristics are not sufficient and the magnetic core becomes large as compared with Fe-based materials. Further, Japanese Patent Publication No. 44393 discloses that a Fe-based microcrystalline alloy exhibits high permeability and low core loss characteristics. However, the Fe-based microcrystalline alloy is apt to be magnetically saturated and is not suitable for the above-mentioned use as it is. Therefore, it is common to form a gap when used for these applications. However, when the gap is formed, magnetic core loss may increase or leakage magnetic flux may occur in the gap portion, which may affect peripheral components when mounted.

[0004]

In order to solve the above problems, the inventors of the present invention have crystal grains with a grain size of 500 angstroms or less occupying at least 50% of the structure, and a residual magnetic flux density of 7,000 G or less, 10 The inventors have found that a magnetic core made of an ultrafine crystal alloy having a magnetic flux density in Oe of 7,000 G or less is excellent in direct current superposition characteristics and is suitable for a normal mode choke, a high frequency transformer and the like, and conceived the present invention. In the present invention, when the residual magnetic flux density is 7,000 G or less and the magnetic flux density at 10 Oe is 7,000 G or less, it exhibits characteristics suitable for a normal mode choke such as a transformer or a smooth choke. When the residual magnetic flux density exceeds 7,000 G, the magnetic core loss increases, which is not preferable, and when the magnetic flux density at 10 Oe exceeds 7,000 G, the DC magnetic field in which the incremental magnetic permeability lowers becomes small, which is not preferable.
In particular, when the residual magnetic flux density is 6000 G or less and the magnetic flux density at 10 Oe is 4000 G or less, a magnetic core suitable for a normal mode choke such as a smooth choke can be obtained. When the residual magnetic flux density is 6000 G or less, the core loss is particularly low. The core loss is particularly low when the crystal grains consist of the bcc phase. Further, when the crystal grains are composed of the bcc phase and the Fe-B compound phase, the incremental magnetic permeability can be 1000 or less, which is particularly desirable for applications such as normal mode choke. On the other hand, if the average particle size exceeds 1,000 angstroms, the soft magnetic properties are significantly deteriorated, which is not preferable. It is preferably 300 angstroms, more preferably 200 angstroms or less. Further, the proportion of crystal grains needs to be at least 50% or more of the structure. Five
If it is less than 0%, the magnetostriction becomes large, causing humming at an audible frequency, and at high frequencies, the magnetic permeability and the core loss rapidly change at a specific frequency due to resonance, which is not preferable. Further, the characteristics are changed due to the deformation due to the increase of the magnetostriction and the core loss is increased, which is not preferable. The crystal grains in the alloy according to the present invention mainly consist of the bcc phase and may contain an ordered phase. The rest of the crystal grains are mainly the amorphous phase. The preferred composition of the alloy according to the present invention is: (Fe _1-a M _a ) _100-xyz- αA _x Si _y B _z M'α (at%) (where M is Co and / or Ni) , A is Cu, at least one element selected from Au, M'is at least one element selected from the group consisting of Mo, V, Cr, Mn and W, a, x, y, z
And α are 0 ≤ a ≤ 0.3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 20, 2 ≤ z
It satisfies ≦ 15, 0.1 ≦ α ≦ 10. ), Or the composition formula: (Fe _1-a M _a ) _100-xyz- α _- βA _x Si _y B _z M '
αM''β (at%) (where M is Co and / or Ni and A is
At least one element selected from Cu and Au, M'is Mo, V, C
at least one element selected from the group consisting of r, Mn and W, M '' is Nb, Ta, Ti, Zr, Hf, Al, Sn, In, Ag, Pd, Rh, Ru, Os, I
At least one element selected from r, Pt, a, x, y, z
And α are 0 ≤ a ≤ 0.3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 20, 2 ≤ z
≦ 15,0.1 ≦ α ≦ 10,0 <β ≦ 10 is satisfied. ) Or a composition formula: (Fe _1-a M _a ) _100-xyz- α _- βA _x Si _y B _z M'αM''βX
γ (at%) (where M is Co and / or Ni, A is Cu, A
At least one element selected from u, M'is Mo, V, Cr, Mn
And at least one element selected from the group consisting of W,
M '' is Nb, Ta, Ti, Zr, Hf, Al, Sn, In, Ag, Pd, Rh, Ru, Os, Ir, Pt
At least one element selected from, X is at least one element selected from C, Ge, Ga, P, a, x, y, z and α
Are 0 ≤ a ≤ 0.5, 0 ≤ x ≤ 3, 0 ≤ y ≤ 20, 2 ≤ z ≤ 15,
0.1 ≦ α ≦ 10,0 <β ≦ 10,0 <γ ≦ 10 is satisfied. The composition represented by () is preferable because it has excellent DC superposition characteristics and low core loss. Here, M is Co and / or Ni, and if the total composition ratio a of Co and Ni exceeds 0.3, the high frequency characteristics deteriorate, which is not preferable. A is at least one element selected from Cu and Au.
It has the effect of facilitating the formation of phases, but if it exceeds 3 at%, it becomes brittle and impractical. M'is Mo, V, Cr, Mn and W is at least one element selected from the group consisting of and has the effect of refining the crystal grain growth and refining the structure and the effect of improving DC superposition characteristics, It is an effective element for the present invention. When the content α of M'exceeds 10%, the saturation magnetic flux density remarkably decreases, so α is preferably 10 at% or less. M '' is Nb, Ta, Ti, Zr, H
At least one element selected from the group consisting of f, Al, Sn, In, Ag, Pd, Rh, Ru, Os, Ir, and Pt. Has the effect of improving.
When the content β of M ″ exceeds 10 at%, the saturation magnetic flux density remarkably decreases, so β is preferably 10 or less. X is at least one element selected from the group consisting of C, Ge, Ga and P and has the effect of adjusting magnetostriction and magnetic properties. When the content γ of X exceeds 10 at%, the saturation magnetic flux density is remarkably reduced, so γ is preferably 10 or less. Si and B are effective in improving the core loss and the magnetic permeability, and it is desirable that the Si amount y is 20 at% or less and the B amount z is 2 to 15 at% or less. Another aspect of the present invention is the step of producing an amorphous alloy ribbon by the liquid quenching method, and 50% of the structure becomes crystal grains with a grain size of 500 angstroms or less at a temperature of 5 minutes or more and 24 hours or less above the crystallization start temperature. Heat treatment, the residual magnetic flux density is 7000G or less, 10O
A method for producing a magnetic core made of the above ultrafine crystal alloy, which is excellent in direct current superposition characteristics, and which comprises a step of setting the magnetic flux density at e to be 7,000 G or less. First, an amorphous alloy ribbon having a plate thickness of about 3 to 100 μm is produced by a liquid quenching method such as a single roll method or a twin roll method. Next, after stacking or winding the alloy ribbon, the structure of 50 minutes or more and 24 hours or less is maintained at a crystallization start temperature or higher in an inert gas atmosphere such as argon gas or nitrogen gas or in the atmosphere. % Is a crystal grain with a grain size of 500 Å or less, residual magnetic flux density is 7,000 G or less, 1
Heat treatment is performed so that the magnetic flux density at 0 Oe is 7,000 G or less. The heat treatment temperature must be higher than the crystallization start temperature. This is because it is difficult to complete the heat treatment in a practical time below the crystallization start temperature, and it is difficult to obtain the above characteristics. Hold time during heat treatment
5 minutes or more and 24 hours or less is desirable. The reason for this is that if the time is less than 5 minutes, it is difficult to keep the alloy at a uniform temperature and sufficient characteristics cannot be obtained, and if it exceeds 24 hours, it is not preferable in terms of productivity. The cooling may be either rapid cooling or gradual cooling, but gradual cooling usually gives preferable results. The usual cooling rate is 0.1 ° C / min or less. At this time, if the surface of the alloy ribbon is covered with an oxide such as SiO ₂ or Al ₂ O ₃ for interlayer insulation, more preferable results can be obtained especially when a wide material is used. As a method for interlayer insulation, MgO by electrophoresis method is used.
A method of attaching oxides such as, a method of forming a metal alkoxide solution on the surface and heat-treating it to form an oxide such as SiO ₂ , a method of performing phosphate or chromate treatment to coat the surface with an oxide, There is a method of forming a film such as AlN or TiN on the surface by CVD or PVD. There is also a method of inserting an insulating film such as polyimide or PET between the thin strips to perform interlayer insulation. Another aspect of the present invention is a chord formed by winding a conductive wire around a magnetic core made of the ultrafine crystal alloy.
It's a cocoile. The choke coil is small in size and high in performance because it has excellent DC superposition characteristics and has a small magnetic core loss. The alloy ribbons produced by the single roll method or the like are laminated or wound in a toroidal shape, and after the magnetic core is produced, heat treatment is performed at a temperature higher than the crystallization start temperature, and 50% of the structure has a grain size of 500 angstroms or less. So that it becomes the crystal grain of. Further, this magnetic core is put into an insulating core case or coated, and then a conducting wire is wound to produce a choke coil. Another aspect of the present invention is a transformer formed by winding at least two conducting wires around a magnetic core made of the ultrafine crystal alloy. Since the direct current superimposition characteristics are excellent, there is little possibility that the magnetic core will be saturated and the circuit will be damaged due to demagnetization or the like, and it is not necessary to provide a gap or use a cut core. Further, since there is no gap, the leakage magnetic flux is small and the influence on the surroundings is small. Further, the magnetic core loss is small and the operating magnetic flux density can be large. Therefore, the transformer is small. The alloy ribbons produced by the single roll method or the like are laminated or wound in a toroidal shape, and after the magnetic core is produced, heat treatment is performed at a temperature higher than the crystallization start temperature, and 50% of the structure has a grain size of 500 angstroms or less. So that it becomes the crystal grain of. Further, this magnetic core is put in an insulating core case, or after coating, at least two conducting wires are wound to form a transformer.

[0005]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. (Embodiment 1) Fe having a width of 6.5 mm and a thickness of 19 μm by a single roll method
_bal. Cu ₁ Mo ₃ Si ₁₆ B ₆ Amorphous alloy ribbon was prepared. Next, this alloy ribbon is wound around an outer diameter of 21.5 mm and an inner diameter of 12.0 mm, and 610 °
The heat treatment was carried out at C for 1 hour in the absence of a magnetic field. Observation of the structure of this alloy revealed that most of them were bcc crystal grains with a grain size of about 200 angstroms. In addition, a compound phase was partially formed according to the result of X-ray diffraction. Next, this magnetic core was placed in a phenol resin core case and the DC BH curve was measured. The B-H curve has a very low residual magnetic flux density and an excellent constant magnetic permeability. The residual magnetic flux density B _r is 3500 G, and the magnetic flux density at 10 Oe is 3600 G. Next, a conductor with a diameter of 0.7 mm
A 20-turn winding choke coil was manufactured and the DC superposition characteristics at 10 kHz were measured. The obtained results are shown in FIG.
For comparison, the DC superposition characteristics of a ferrite core with a gap and a Mo permalloy dust core are shown. The incremental magnetic permeability μΔ of the alloy of the present invention is 150 or more up to 40 Oe, and ferrite and Mo
Better than permalloy dust core. Further, in the conventional ultra-fine crystal alloy, the incremental magnetic permeability μΔ rapidly decreases when the superimposed magnetic field becomes large, whereas the choke made of the alloy of the present invention has a large μΔ and exhibits excellent characteristics as a normal mode choke. . Therefore, it is suitable as a smooth choke and a choke for preventing noise of normal mode. Next, 100kHz, 2kG
The magnetic core loss was measured. The results obtained are shown in Table 1.

[Table 1] It can be seen that the core loss is low and superior to conventional materials having excellent DC superposition characteristics.

(Example 2) 6.5 mm wide by a single roll method,
A 19 μm thick Fe _bal. Cu ₁ Mo ₃ Si ₁₆ B ₆ amorphous alloy ribbon was prepared. Next, this alloy ribbon was cut to an outer diameter of 21.5 mm and an inner diameter of 1
It was wound to 2.0 mm and the heat treatment temperature was changed for 1 hour to perform heat treatment in a non-magnetic field. The structure of this alloy was observed by a transmission electron microscope to examine the grain size and the forming phase by X-ray diffraction. Next, this magnetic core was placed in a phenol resin core case and the DC BH curve was measured. The results obtained are shown in Table 2. All alloys except the alloy in which the forming phase consists of the amorphous phase are bc
Phase c accounted for 50% or more of the structure.

[Table 2] When heat treatment is performed so that the crystal grains are at least 50% of the structure, the crystal grain size is 500 angstroms or less, the residual magnetic flux density B _r is 7,000 G or less, and the magnetic flux density at a DC superimposed magnetic field of 10 Oe is 7,000 G or less. At a DC superposed magnetic field of 10 Oe, the incremental magnetic permeability μΔ is high and the core loss is low, which is suitable for the normal mode choke.

(Example 3) A width of 6.5 mm was measured by a single roll method.
Amorphous alloy ribbons with the composition shown in Tables 3 and 4 with a thickness of 19 μm were prepared. Next, this alloy ribbon was cut to an outer diameter of 21.5 mm and an inner diameter of 12.0.
The film was wound into a millimeter and heat-treated at 610 ° C for 1 hour in a non-magnetic field. The structures of these alloys were observed with a transmission electron microscope to examine the crystal grain size and the forming phase by X-ray diffraction. As a result, the particle size
At least 5 grains of 500 angstroms or less in the structure
It was confirmed to account for more than 0%. Next, this magnetic core was placed in a phenol resin core case and the DC BH curve was measured. The obtained results are shown in Tables 3 and 4.

[Table 3]

[Table 4]

(Embodiment 4) A width of 6.5 mm is measured by a single roll method.
An amorphous alloy ribbon with a composition of Fe _bal Cu ₁ Nb ₂ Si ₁₁ B ₈ (at%) with a thickness of 19 μm was prepared. Next, use this alloy ribbon with an outer diameter of 2
It was wound to a diameter of 1.5 mm and an inner diameter of 12.0 mm and heat-treated in a magnetic field-free. The structures of these alloys were observed with a transmission electron microscope to examine the crystal grain size and the forming phase by X-ray diffraction. Next, this magnetic core was placed in a phenol resin core case and the DC BH curve was measured. The results obtained are shown in Table 4. It can be seen that when B _r exceeds 7,000 G, the core loss significantly increases, which is not preferable. Further, when B ₁₀ exceeds 7,000 G, μΔ is low and the direct current superposition characteristic is poor, which is not preferable.

[Table 5]

(Example 5) A width of 6.5 mm was measured by a single roll method.
A 19 μm thick Fe _bal. Cu ₁ W ₃ Si ₁₅ B ₆ amorphous alloy ribbon was prepared. Next, use this alloy ribbon with an outer diameter of 20 mm and an inner diameter of 12.0 mm.
After being heat-treated at 605 ° C for 1 hour in a non-magnetic field
After cooling to room temperature at a rate of C / min, the ultrafine crystal alloy of the present invention was produced. Next, this magnetic core is used as a phenol resin core
It was put in a coil to prepare a wound magnetic core, which was further wound to prepare a transformer. We evaluated this transformer as the main transformer of the switching power supply. Conventional Fe for comparison
_A comparison was made with a transformer using a _73.5 Cu ₁ Nb ₃ Si _13.5 B ₉ ultrafine crystal alloy. When a gap is not formed or a cut core is not used, the transformer using the conventional ultra-fine crystal alloy saturates the magnetic core and the semiconductor fails. On the other hand, the transformer of the present invention operated stably at a temperature rise of 40 ° C without breaking the circuit.

[0010]

According to the present invention, an ultra-fine crystal alloy having excellent DC superposition characteristics and low loss, suitable for a normal mode choke coil and a transformer, a method for producing the same, and a choke coil using the same are provided. Since a transformer can be provided, its effect is remarkable.

[Brief description of drawings]

FIG. 1 is a graph showing an example of DC superimposition characteristics of an ultrafine crystal alloy according to the present invention.

Claims (10)

[Claims] 1. A crystal grain having a grain size of 500 Å or less occupies at least 50% of the structure, a residual magnetic flux density of 7,000 G or less, and a magnetic flux density of 10 Oe of 7,000 G or less. A magnetic core characterized by being made of a crystalline alloy. 2. The magnetic core according to claim 1, wherein the residual magnetic flux density is 6000 G or less and the magnetic flux density at 10 Oe is 4000 G or less. 3. The magnetic core according to claim 1, wherein the crystal grains are composed of a bcc phase. 4. The magnetic core according to claim 1, wherein the crystal grains consist of a bcc phase and a Fe—B compound phase. 5. The ultrafine crystal alloy has a composition formula: (Fe _1-a M _a ).
_100-xyz- αA _x Si _y B _z M'α (at%) (where M is Co and / or Ni, A is at least one element selected from Cu and Au, M'is Mo, V, Cr, Mn and at least one element selected from the group consisting of W, a, x, y, z and α are respectively 0 ≤ a ≤ 0.3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 20,2 ≦ z ≦ 15, 0.1 ≦ α ≦ 10
Meet The magnetic core according to any one of claims 1 to 4, which has a composition represented by (4). 6. The ultrafine crystal alloy has a composition formula: (Fe _1-a M _a ).
_{100-xyz- α - βA x Si} y B z M'αM''β (at%) ( where, M is Co
And / or Ni, A is at least one element selected from Cu and Au, M ′ is at least one element selected from the group consisting of Mo, V, Cr, Mn and W, and M ″ is Nb. , Ta, Ti, Zr, Hf, A
At least one selected from l, Sn, In, Ag, Pd, Rh, Ru, Os, Ir, Pt
It is one kind of element, a, x, y, z and α are 0 ≦ a ≦ 0.
3,0 ≤ x ≤ 3, 0 ≤ y ≤ 20, 2 ≤ z ≤ 15, 0.1 ≤ α ≤ 10, 0 <β ≤ 10
Meet The magnetic core according to any one of claims 1 to 4, which has a composition represented by (4). 7. The ultrafine crystal alloy has a composition formula: (Fe _1-a M _a ).
_100-xyz- α _- βA _x Si _y B _z M'αM''βXγ (at%) (However, M is
Co and / or Ni, A is at least one element selected from Cu and Au, M ′ is at least one element selected from the group consisting of Mo, V, Cr, Mn and W, and M ″ is Nb, Ta, Ti, Zr, H
f, Al, Sn, In, Ag, Pd, Rh, Ru, Os, Ir, Pt at least one element selected from, X is at least 1 selected from C, Ge, Ga, P
It is a seed element, and a, x, y, z and α are each 0 ≦ a ≦ 0.
3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 20, 2 ≤ z ≤ 15, 0.1 ≤ α ≤ 10, 0 <β ≤ 1
0,0 <γ ≦ 10 is satisfied. The magnetic core according to any one of claims 1 to 4, which has a composition represented by (4). 8. A choke constructed by winding a conductor wire around a magnetic core made of the ultrafine crystal alloy according to claim 1. Description:
Cucoir. 9. A transformer constituted by winding at least two conducting wires around a magnetic core made of the ultrafine crystal alloy according to any one of claims 1 to 7. 10. A step of producing an amorphous alloy ribbon by a liquid quenching method, and 5 minutes or more at a crystallization start temperature or higher 2
Heat treatment is performed at a temperature of 4 hours or less so that 50% of the structure becomes crystal grains with a grain size of 500 angstroms or less.
An excellent DC superimposition characteristic comprising a step of setting the magnetic flux density at 7,000 G or less and 10 Oe at 7,000 G or less.
8. The method for manufacturing a magnetic core according to any one of 7 to 7.