JPH11260617A - Dust core, manufacture of the same, and winding component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust core having high magnetic permeability and an superior direct-current superimposition property, a winding component, and a manufacturing method which enables easy manufacture of a dust core. SOLUTION: A dust core is obtained by compression-molding powder, obtained by mixing powder of an alloy containing Fe-Si-Al as a principal component and a binder. The alloy powder is made of a powder A at 5-95%, in which the aspect ratio of particles is 5 or more and in which a short-axis length is 50 μm or less, and a powder for the remaining part in which the aspect ratio of particles is smaller than that of the powder A and is not less than 1.5. As a manufacturing method for the same, a metal mold and the powder are pre- heated within a temperature range which is not higher that the hardening temperature of the dust core and the binder, and the powder is compression-molded. Binder hardening processing is carried out so as to constrain the shape of a compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a winding component used for a DC power supply of an electronic device and the like, and more particularly, to a dust core suitable for use in a winding component such as a transformer and a choke coil, and a method of manufacturing the same. And a winding component.

[0002]

2. Description of the Related Art Ferrite cores and dust cores are used for choke coils and transformers used at high frequencies in DC power supplies for electronic equipment and the like.

[0003] Among them, the ferrite core has a disadvantage that the saturation magnetic flux density is small. On the contrary,
A dust core formed by molding an alloy powder has a higher saturation magnetic flux density than a ferrite core, and thus has an advantage of being excellent in DC superposition.

However, since the dust core is formed by mixing an alloy powder with an organic binder or the like and compression-molding the powder magnetic core, it has a drawback of low magnetic permeability and poor high-frequency characteristics of magnetic permeability.

On the other hand, with the recent miniaturization of electronic equipment, miniaturization of electronic components is also required.
Strict reduction in size is required for winding components having a large volume.

[0006] Therefore, there is a constant need to improve the magnetic properties of the magnetic core that determine the size of the winding component. And
Dust cores are no exception. In other words, it is required that the inductance of the winding component be equivalent while achieving a reduction in size. As a solution to this, it is necessary to improve the magnetic permeability of the dust core used for the winding component and the frequency characteristics.

In general, there are two methods for improving the magnetic permeability of a dust core. One method is to increase the magnetic permeability of the raw material itself, and the other is to increase the filling rate.

Conventionally, the method of improving the magnetic permeability of a dust core has mainly focused on the improvement of the filling rate. As means for this, for example, increasing the molding pressure or changing the binder variously has been studied. Have been.

[0009]

However, the improvement of the magnetic permeability of the dust core by the above-mentioned method has already been thoroughly studied. For example, even if the molding pressure is increased, the life of the mold is reduced. It is difficult to raise the pressure more than before from the viewpoint of manufacturing costs. Therefore, a significant improvement from the current characteristic level is in a difficult situation, and it cannot cope with very recent miniaturization of equipment.

Therefore, an object of the present invention is to provide a high magnetic permeability,
Moreover, it is an object of the present invention to provide a dust core having excellent DC superimposition characteristics, a winding component, and a manufacturing method capable of easily manufacturing a dust core.

[0011]

Means for Solving the Problems The present inventors have repeatedly studied the relationship between the powder shape and the magnetic permeability of the dust core in order to achieve the above object, and as a result, by increasing the aspect ratio of the raw material powder. And found that the magnetic permeability of the dust core was significantly improved.

Accordingly, the present invention provides a dust core obtained by compression-molding a powder obtained by mixing a powder of an alloy mainly composed of Fe—Si—Al and a binder, wherein the powder of the alloy is 5% to 95% of powder A having an aspect ratio of particles of 5 or more and a minor axis length of 50 μm or less, and the remainder comprising powder having a particle aspect ratio smaller than that of powder A and 1.5 or more. It is a dust core.

The present invention also relates to a powder A having an alloy having an aspect ratio of 5 or more and a minor axis length of 50 μm or less, wherein the aspect ratio of the particle is smaller than that of the powder A and 1.5 or less.
A method for producing a dust core as described above, wherein the powder described above is mixed and used in a range of 95: 5 to 5:95.

Further, the present invention provides the above-mentioned compacting method, wherein the mold and the powder are preheated in a temperature range not lower than room temperature and not higher than the curing temperature of the binder, and the powder is compacted and formed. This is a method for manufacturing a magnetic core.

Further, the present invention is the above-mentioned method for producing a dust core, wherein the curing treatment of the binder is performed in a state where the shape of the compact is restricted.

[0016] The present invention also provides a winding component comprising the above-mentioned dust core.

The improvement of the magnetic permeability in the present invention is due to the fact that the demagnetizing coefficient of the powder is reduced by increasing the shape of the powder to a high aspect ratio. This is probably because the material has the property of being oriented at right angles to the pressing direction, which is the most stable.

Further, by performing the molding with the mold and the powder preheated at the time of molding, the fluidity of the binder is increased, the slip between the powder particles is improved, the filling of the powder and the orientation of the powder are improved, and the high permeability is further improved. A dust core with magnetic susceptibility is obtained.

On the other hand, an increase in the magnetic permeability of the magnetic core generally causes deterioration of the DC superposition characteristics of the winding component. However, in the present invention, by mixing two kinds of powders having different aspect ratios, the magnetic permeability and The DC superimposition characteristics were simultaneously improved. This improvement is considered to be due to the fact that the powder filling ratio and the powder orientation are improved by mixing two kinds of powders, and the saturation magnetic flux density is improved.

The improvement of the magnetic permeability by performing the binder hardening treatment of the molded body while restricting the shape and dimensions of the molded body is due to the fact that the molded body made of the powder having a high aspect ratio is subjected to spring back (after compression molding). This is because it is very effective in improving the filling rate to perform binder hardening after molding while restricting the shape and dimensions at the time of molding because the molded article released from external force expands greatly.

Various starting materials can be considered, such as pulverized powder from an ingot, atomized powder, and the like by a dissolving method. However, as long as the concentration distribution of the composition is uniform, the production method is not limited, and these powders are pulverized by a ball mill, an attritor, or the like. The aspect ratio of the powder can be changed by adjusting the grinding time.

The reason why the aspect ratio of the powder to be mixed is limited here is that the aspect ratio of the powder to be mixed causes a decrease in the magnetic permeability, or the DC superimposition characteristic cannot be improved.

The reason why the short axis length of the powder particles is specified is that if the short axis length exceeds 50 μm, it is difficult to secure an aspect ratio.

The reason why the mixing ratio of the powder to be mixed is limited is that the mixing ratio of the powder causes a decrease in the magnetic permeability, or the DC superimposition characteristic cannot be improved.

The reason why the preheating temperature is specified here is that the fluidity of the binder is improved at room temperature or higher, and the hardening of the binder is started at the curing temperature or higher, so that the fluidity is reduced.

[0026]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dust core obtained by compression-molding a powder obtained by mixing a powder of an alloy mainly composed of Fe-Si-Al and a binder, and Is composed of powder A having an aspect ratio of 5% to 95% of particles of 5 or more and a minor axis length of 50 μm or less, and the remainder composed of powder having a particle aspect ratio smaller than that of powder A and 1.5 or more. Dust core and pre-heated mold and powder within the temperature range below the curing temperature of the binder, compression-molded the powder, and hardened the binder by constraining the shape of the compact. And its manufacturing method.

[0027]

The present invention will be described below with reference to examples.

Example 1 A powder of a BalFe-10 wt% Si-5 wt% Al alloy produced by an atomizing method was classified to 150 μm or less, and the resulting powder was pulverized using a ball mill to flatten the powder. went.

As a result of the above treatment, powder having a minor axis length of 50 μm or less and powder particles having an aspect ratio of 2.5 and 15 was obtained.
Then, 50 wt% of the powder having the aspect ratio of 2.5 was mixed with the powder having the aspect ratio of 15 and then 3 wt% of the silicone resin (binder) was mixed, and compression molding was performed at room temperature using a mold (forming pressure of 10 ton / cm ² ) and the outer diameter is 1
A dust core of the present invention (sample No. 1) having a toroidal shape of 3 mm, an inner diameter of 8 mm, and a thickness of 5 mm was obtained.

Further, the mixed powder used for sample No. 1 was preheated, the die was also preheated, and then compression-molded.
dust core of the present invention having the same shape as o.1 (Sample No. 2)
I got

Next, these dust cores were subjected to a heat treatment at 170 ° C. for 2 hours in the air to cure the binder.
Next, heat treatment was performed at 700 ° C. for 2 hours in the air which is an oxidizing atmosphere.

Further, a dust core similar to that of sample No. 2 was obtained and held in a mold, that is, the shape of the molded body was restrained, and the same A hardening treatment was performed to obtain a dust core of the present invention (Sample No. 3).

Next, a winding was applied to the obtained dust core, and DC BH characteristics were measured. FIG. 1 shows the BH curve (Sample No. 1). Next, the inductance and the DC bias characteristics were measured with an LCR meter.

The inductance was converted to AL [inductance ÷ (number of turns) ² ] which is an inductance value per turn, and normalized.

Next, the evaluation of the DC superimposition characteristic is as follows: AL (AL ₀ ) before DC bias is applied,
2) A DC bias indicating × AL ₀ is represented by a magnetic field strength (AT), and the AT value, AL ₀ and magnetic permeability (calculated from inductance) are shown in Table 1.

[0036]

The sample used as a comparative example is a raw material powder before ball mill pulverization, in which a dust core having the same dimensions as that of the sample N0.1 was produced in exactly the same manner. The properties were measured.

As shown in Table 1 and FIG. 1, the product of the present invention of Example has a higher magnetic permeability μ and a higher saturation magnetic flux density (instead of the magnetic flux density when 200 Oe is applied), as compared with the comparative example. As a result, the DC superposition characteristic [AL is (1/2)
× AT value indicating the AL ₀ Value is also excellent present invention product. That is, according to the present invention, the magnetic permeability and the direct current superimposition characteristics could be simultaneously improved.

Example 2 An alloy powder having a minor axis length of 50 μm or less and an aspect ratio of powder particles having an aspect ratio of 15 prepared in Example 1 and an aspect ratio of 2.5 having an aspect ratio of 2.5 was prepared in exactly the same manner as in Example 1. 5 wt%, 20 wt%, 40 wt% of powder,
The mixture was mixed at 60 wt%, 80 wt%, and 95 wt%, and the molding pressure (15 ton) was obtained in the same manner as in Sample No. 2 of Example 1.
/ Cm ² ) to obtain a dust core of the present invention.

The DC superimposition characteristics and inductance of the obtained dust core were measured, and the inductance was determined to be 100 kHz.
The magnetic permeability at z was also determined. The result is shown in FIG.

The comparative examples include powder particles having an aspect ratio of 15
3 wt% of a silicone resin is mixed with the powder of only the mixture (mixing ratio 0%) and the powder of the aspect ratio 2.5 only (0% of the same). A powder magnetic core was prepared and used.

As shown in FIG. 2, the powder having an aspect ratio of only 15 has a high magnetic permeability but a low DC superposition characteristic, and the powder having an aspect ratio of only 2.5 has a good DC superposition characteristic. However, the magnetic permeability is extremely low.

Therefore, the magnetic permeability is significantly reduced when the mixing ratio of the powder having an aspect ratio of 2.5 of the powder particles is 95% or more.
Since the direct current superimposition characteristic is improved by powder mixing from a mixing ratio of 5% or more, the range of the mixture ratio of the powder having both good characteristics is specified as 5 wt% to 95 wt%.

Example 3 Powder particles having an aspect ratio of 1.5 and 2.5 and powder having an aspect ratio of 1 before pulverization, each having an aspect ratio of 1.5, were obtained in exactly the same manner as in Example 1.
Was mixed at a ratio of 50 wt%, and the sample N of Example 1 was mixed.
at all to prepare a dust core in the same way as O.2, permeability, measured DC bias characteristics were determined AT value indicating 1 / 2AL ₀ value. Table 2 shows the results.

[0045]

As shown in Table 2, the magnetic permeability of the dust core in which the powder particles having the aspect ratio of 1 and 5 are mixed has a remarkably low magnetic permeability. This is considered to be because powder having an aspect ratio of 1 deteriorates powder orientation in the dust core by mixing the powder.

[0047] Looking at the second permeability table, but other than dust core obtained by mixing powders of aspect ratio 1 and 5 are permeability showed high values, whereas, the AT value o'clock 1 / 2AL ₀ Looking at it,
The value of the dust core having an aspect ratio of 5, in which no powder is mixed, is smaller than other values.

Therefore, the aspect ratio of the effective powder particles of one powder to be mixed in the present invention is specified to be 5 or more.

Example 4 The powder particles obtained by exactly the same method as in Example 1 had an aspect ratio of 1.5, 2, 2.5, 5, 1
The powder having an aspect ratio of 15 was mixed with the powders having the aspect ratio of 1 at a ratio of 50 wt% to the powders having the aspect ratios of 1 and 15 before pulverization, and a dust core was obtained in exactly the same manner as in Sample No. 2 of Example 1. Thus, the magnetic permeability and the DC superimposition characteristics (AT value indicating 1 / 2AL ₀ value) were obtained. Table 3 shows the results.

[0050]

[0051] Looking at the magnetic permeability of Table 3, except the aspect ratio of 1 and 15 of the powder mixed dust core is magnetic permeability is shown a high value, whereas, 1 / 2AL AT value of _0:00 , The value of the dust core having an aspect ratio of 15 in which no powder is mixed is smaller than other values.

Therefore, the aspect ratio of the effective powder particles of the other powder mixed in the present invention is specified to be 1.5 or more and smaller than the aspect ratio of the one powder.

A winding was applied to the dust core obtained as described above to obtain a wound part, and the DC superposition characteristics and the inductance were measured.

[0054]

According to the present invention, a dust core having high magnetic permeability and excellent DC superposition characteristics, a winding component, and
A production method that can easily produce a dust core is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a DC BH curve of a dust core of the present invention.

FIG. 2 is a view showing a change in DC superposition characteristics and a magnetic permeability of a dust core with a change in an aspect ratio of powder particles.

Claims (5)

[Claims] 1. A dust core obtained by compression molding a powder obtained by mixing a powder of an alloy mainly composed of Fe—Si—Al and a binder, wherein the powder of the alloy is 5% to 95%. %
A powder A having a particle aspect ratio of 5 or more and a minor axis length of 50 μm or less, and a balance of powder A having a particle aspect ratio smaller than the powder A and 1.5 or more. core. 2. The method according to claim 1, wherein the powder A and a powder having a particle aspect ratio smaller than that of the powder A and not less than 1.5
2. The method for producing a dust core according to claim 1, wherein the powder magnetic core is mixed and used in a range of 5: 5 to 5:95. 3. The powder magnetic material according to claim 2, wherein the mold and the powder are preheated in a temperature range not lower than room temperature and not higher than the curing temperature of the binder, and the powder is compressed and molded. Manufacturing method of core. 4. The method for producing a dust core according to claim 2, wherein the curing treatment of the binder is performed in a state where the shape of the molded body is restricted. 5. A winding component comprising the dust core according to claim 1.