JPH10223423A - Thin-type magnetic core and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic core and method for manufacturing it in which miniaturizing and thinning are realized by uniformly coating a magnetic core base material, without causing significant deterioration in properties. SOLUTION: In a magnetic core comprising a toroidal magnetic core base material 3, in which a thin band 2 of soft magnetic alloy is wound and a coating layer 4 which coats the outer surface thereof, the coating layer 4 is formed by powder coating of resin material, such as an epoxy resin. This coating layer 4 is formed only on the outer surface of the magnetic core base material 3, so that it does not get into gaps between the thin band 2 layers. In addition, the thickness of the coating layer 4 is made to be about 50-100μm, and hardening temperature is set to be 160 deg.C or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin magnetic core and a method of manufacturing the same, and more particularly to a small and thin magnetic core suitable for use in a pulse transformer for an interface or a choke coil for a noise filter, and a method of manufacturing the same. is there.

[0002]

2. Description of the Related Art With the miniaturization of electronic devices, there is a demand for further miniaturization and thinning of this type of transformer and coil. Conventionally, ferrite, microcrystalline alloys, and the like, which have advantages such as low core loss, have been used as the material of the magnetic core used for these transformers and coils. However, when ferrite is used, it is difficult to reduce the size of a magnetic core when applied to a pulse transformer or a choke coil because of its low inductance and poor temperature characteristics. Also,
When a microcrystalline alloy is used, it is possible to reduce the size as a whole due to the large inductance.
It is necessary to house in a case to insulate and wind the magnetic core substrate wound with a thin ribbon of the base soft magnetic microcrystalline alloy,
There was a limit to thinning.

[0003]

In the case where a case for accommodating the magnetic core base is manufactured by resin molding, the thickness of the case is limited to 150 μm, which is a limit of thickness reduction. could not.
Therefore, instead of using a case, it has been studied to cover the outer surface of the magnetic core base with a coating layer made of resin or the like.

However, when a resin containing a solvent is coated, the coating film thickness can be reduced to about 1 μm, but there is a problem that the edge of the magnetic core base is not sufficiently covered and insulation cannot be secured. . Therefore, if it is attempted to coat to a thickness of about several tens of micrometers, the thickness will not be uniform due to dripping of the resin. Also,
In this method, the resin enters between the layers of the wound soft magnetic alloy ribbon, and stress is generated in the magnetic core substrate when the resin is cured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made to reduce the size by uniformly coating the magnetic core substrate without causing significant deterioration in characteristics.
It is an object of the present invention to provide a magnetic core that can be made thinner and a method for manufacturing the same.

[0006]

The inventors of the present invention have conducted intensive studies and as a result, have found that by using powder coating for forming the coating layer, the edge portion of the magnetic core substrate is not exposed, and the characteristics of the core are not deteriorated. They have found that a small coating layer can be obtained and a thin core with high inductance can be obtained, and the present invention has been created.

That is, the thin magnetic core of the present invention comprises a magnetic core substrate formed by winding a thin ribbon of a soft magnetic alloy and a coating layer covering the outer surface thereof, and the coating layer is formed by powder coating of a resin material. It is characterized by having. In the case of powder coating, the powdery resin is unlikely to enter the gap between the ribbon layers, and the powder adhering to the outer surface is adhered by moderate heating. Are not formed. Further, it is desirable that the thickness of the coating layer is 50 to 100 μm and that the coating layer is made of an epoxy resin.

The method of manufacturing a thin magnetic core according to the present invention comprises:
A method of manufacturing a thin magnetic core comprising a magnetic core substrate formed by winding a thin ribbon of a soft magnetic alloy and a coating layer covering the outer surface thereof, wherein after the core substrate is manufactured, a powder of a resin material is added to the core substrate. The coating layer is formed by applying a coating. In particular, it is desirable to set the thickness of the coating layer to 50 to 100 μm, to cure the resin material at a temperature of 160 ° C. or lower, and to use an epoxy resin as the resin material.

As the resin-based material used for the coating layer, various resin-based materials such as epoxy-based, polyethylene-based, polyester-based, fluorine-based, nylon-based, Mersen (EVA) -based, and acrylic-based materials can be used. .
Among them, an epoxy resin is particularly preferable as a coating layer material because it has a high electric insulation property and can lower the curing temperature. The electrical insulation between the ribbon layers may be further enhanced by adding an interlayer insulating film such as SiO ₂ or Al ₂ O ₃ to the ribbon. Before the powder coating is performed, a base film for absorbing stress may be formed with a silicon resin or the like.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. The thin magnetic core 1 of the present embodiment is
A toroidal magnetic core substrate 3 formed by winding a ribbon 2 of a soft magnetic alloy and a coating layer 4 covering the outer surface thereof;
The coating layer 4 is formed by powder coating of a resin material. The soft magnetic alloy ribbon 2 includes Fe, M
(= Zr, Hf, Nb, Ta, Mo, W), a microcrystalline alloy material containing B as a main component and having a microcrystalline structure having an average particle diameter of 30 nm or less (trade name: Nanopalm, Alps Electric Co., Ltd.)
Manufactured), a Co-based amorphous alloy, a Fe-based amorphous alloy, or the like. As the resin-based material used for the coating layer 4, various resin-based materials such as epoxy-based, polyethylene-based, polyester-based, fluorine-based, nylon-based, Mersen (EVA) -based, and acrylic-based materials are used.

The coating layer 4 is formed only on the outer surface of the toroidal magnetic core base 3 and does not enter the gap between the layers of the ribbon 2. The gap between the layers of the ribbon 2 is about 1 to 2 μm, the average particle diameter of the powder resin is about 40 μm (minimum 10 μm, maximum 80 μm), and the thickness of the coating layer 4 is about 50 to 100 μm.

When manufacturing the thin magnetic core 1, first,
A thin ribbon 2 in an amorphous state is produced from a soft magnetic alloy material by a liquid quenching method or the like. Then, after winding this, a heat treatment is performed to produce a toroidal magnetic core substrate 3 in a microcrystalline state. Next, on the surface of the toroidal magnetic core substrate 3, the resinous material in a powder form, for example, an epoxy resin having a thickness of 50 to 10 is applied.
It is sprayed so as to have a thickness of about 0 μm, heated to a temperature of 160 ° C. or lower, and cured to form a coating layer 4.

Conventionally, when a coating layer is formed by applying a liquid resin containing a solvent, if the coating is performed with a thickness that does not expose the edge of the toroidal core substrate, the resin drips and the coating layer drips on the substrate surface. Was not formed uniformly. In addition, the resin soaked between the layers of the wound ribbon, resulting in remarkable property deterioration due to the curing stress of the resin. On the other hand, in the present embodiment, since the coating layer 4 is formed by powder coating, the thickness can be sufficiently controlled, and the uniform coating layer 4 is formed to ensure sufficient insulation. be able to. Further, since the resin-based material is in a powder form, a large amount of resin does not enter into the layers of the thin ribbon 2 and the characteristic deterioration can be reduced as compared with the related art.

The technical scope of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present invention. For example, various materials can be used for the magnetic core substrate in addition to the Fe-MB microcrystalline alloy, the Co-based amorphous alloy, the Fe-based amorphous alloy, and the shape may be appropriately changed in addition to the toroidal type. In addition, soft magnetic alloy ribbon
An interlayer insulating film such as ₂ or Al ₂ O ₃ may be added. Thereby, the electrical insulation between the ribbon layers can be further enhanced. In addition, a base film for stress absorption may be formed using a silicon-based resin or the like before performing powder coating.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The results of actual production of thin magnetic cores according to the present invention and evaluation of characteristics will be described below.

[Experimental Example 1] (Comparison between equivalent product of the present invention and conventional product) Nb 3.5%, Zr 3.5%, B8%, Cu1 in atomic%
%, And the remainder of the alloy was substantially quenched by a single roll method to prepare an amorphous alloy ribbon having a width of 15 mm and a thickness of 20 μm. Then, after cutting the obtained amorphous alloy ribbon into a width of 1 mm, the outer diameter is 7.8 mm and the inner diameter is 4.
It was wound to a size of 8 mm to produce a toroidal magnetic core substrate. Next, this substrate was heat-treated in a vacuum at 660 ° C. for 10 minutes without applying a magnetic field, and air-cooled to room temperature. After the heat treatment, the formation phase and the structure of the alloy ribbon constituting the magnetic core substrate were observed, and it was found that most of the phases were composed of 80 to 100 ° bccFe ultrafine crystal grains. Then, an epoxy-based powder resin having an average particle size of 40 μm is
The coating was applied by curing at a temperature of ° C. to prepare a core having a coating layer thickness of 50 μm and a core having a thickness of 100 μm. These are the magnetic cores of the first and second embodiments, respectively.

On the other hand, after preparing a toroidal magnetic core substrate in the same manner as described above, coating was performed with a normal liquid epoxy resin containing a solvent, and a magnetic core having a coating layer thickness of 1 μm and a magnetic core of 10 μm.
m magnetic cores were produced. These are the magnetic cores of Comparative Example 1 and Comparative Example 2, respectively.

The change in inductance before and after coating was examined for each of the magnetic cores, and the covering state of the edge portion of the magnetic core base was observed. Table 1 shows the results.
The inductance change rate in Table 1 was calculated by the following equation.

(Equation 1)

[0019]

[Table 1]

As shown in Table 1, the edge portion is exposed in Comparative Example 1 having a very small film thickness, and the edge portion is not exposed in Comparative Example 2, but the inductance change rate is -50.
% Was extremely large. On the other hand, in both Examples 1 and 2, the edge portions were not exposed, and the inductance change rates were -3% and -8%, which were smaller values than Comparative Example 1. Therefore, according to the magnetic cores of Examples 1 and 2 using the powder coating, it was found that a coating layer having a uniform film thickness could be formed, and the characteristic deterioration could be suppressed to a small level.

[Experimental Example 2] (Study on Dependence of Film Thickness) After a toroidal magnetic core substrate was prepared in the same manner as in Examples 1 and 2, the thickness of the coating layer by powder coating was reduced to 30 μm or more.
The coating layer was formed by changing the thickness to 180 μm.
The film thickness is 30 μm, 60 μm, 90 μm, 120 μm, 1
The cores of 50 μm and 180 μm were used as the cores of Comparative Example 3, Example 3, Example 4, Comparative Example 4, Comparative Example 5, and Comparative Example 6, respectively. Then, for each of these magnetic cores, the inductance change rate before and after coating and the covering state of the core core edge were examined. The results are shown in Table 2 and FIG.

[0022]

[Table 2]

As shown in Table 2, in Comparative Example 3 having a thin film thickness of 30 μm, the edge portion was exposed, and in Comparative Examples 4 to 6, the rate of change in inductance exceeded -10%. On the other hand, in Examples 3 and 4, the results were good in both the rate of change in inductance and the covering state of the edge portion. In addition, as shown in FIG. 2, when the coating layer thickness exceeds 100 μm, the inductance change rate tends to increase rapidly.
Therefore, considering the covering state of the edge part,
When an epoxy resin was used for the coating layer, it was found that the film thickness was optimally about 50 to 100 μm.

[Experimental Example 3] (Study on Curing Temperature Dependence) After preparing a toroidal magnetic core substrate in the same manner as in Examples 1 and 2, the coating layer thickness was adjusted to 100 μm, and the curing temperature was 150 ° C. The coating layer was formed by changing the temperature to 〜220 ° C. Curing temperature 150 ° C, 180
C, 200 C and 220 C were cores of Example 5, Comparative Example 7, Comparative Example 8 and Comparative Example 9, respectively. And the inductance change rate before and after coating was examined for each of these magnetic cores. The results are shown in Table 3 and FIG.

[0025]

[Table 3]

As shown in Table 3, only Example 5 having a curing temperature of 150 ° C. had an inductance change rate smaller than -10%, and Comparative Examples 7 to 9 all exceeded -10%. In addition, as shown in FIG. 3, when the curing temperature becomes 160 to 170 ° C. or higher, the inductance change rate tends to increase sharply. It is considered that the reason for this is that if the curing temperature is too high, the amount of shrinkage of the cured resin when it is cooled to room temperature increases, and the stress applied to the substrate increases. Therefore, it was found that when the epoxy resin was used for the coating layer, the curing temperature was optimally 160 ° C. or lower.

[0027]

As described above in detail, according to the present invention, a small and thin magnetic core having a high inductance can be obtained, so that the present invention is applied to a pulse transformer for an interface or a choke coil for a noise filter. It is possible to provide a magnetic core with higher performance than before.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a thin magnetic core according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating evaluation results in the example of the present invention, and is a diagram illustrating a relationship between an inductance change rate and a coating layer thickness.

FIG. 3 is a diagram showing the same evaluation results, and is a diagram showing a relationship between an inductance change rate and a curing temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thin core 2 Thin ribbon 3 Toroidal core base 4 Coating layer

Claims (8)

[Claims] 1. A magnetic core substrate formed by winding a ribbon of a soft magnetic alloy, and a coating layer covering an outer surface thereof, wherein the coating layer is formed by powder coating of a resin material. Thin magnetic core. 2. The thin magnetic core according to claim 1, wherein the coating layer is not formed in a gap between the ribbon layers constituting the magnetic core base. 3. The coating layer has a thickness of 50 to 10.
The thin magnetic core according to claim 1, wherein the thickness is 0 μm. 4. The thin magnetic core according to claim 1, wherein the coating layer is made of an epoxy resin. 5. A method for producing a thin magnetic core comprising a magnetic core substrate formed by winding a thin ribbon of a soft magnetic alloy and a coating layer covering an outer surface thereof, wherein the core substrate is produced, and a resin is applied to the magnetic core substrate. A method for producing a thin magnetic core, wherein a coating layer is formed by applying powder coating of a base material. 6. The coating layer having a thickness of 50 to 10
The method for manufacturing a thin magnetic core according to claim 5, wherein the thickness is set to 0 µm. 7. The method according to claim 6, wherein the resin material is cured at a temperature of 160 ° C. or less. 8. The method according to claim 5, wherein an epoxy resin is used as the resin material.