JP3264010B2 - Manufacturing method of ferrite powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferrite powder used for a ferrite resin used as a molding material for a choke coil, a microinductor, a rotary transformer and the like.

[0002]

2. Description of the Related Art Conventionally, as a molding material for a choke coil, a microinductor, a rotary transformer, etc., for example, a ferrite resin composed of a polymer material and ferrite powder has been used. This ferrite resin is used for enclosing the coil in the choke coil or the like to increase the magnetic permeability of the coil.

[0003] Such a ferrite resin can be formed into a desired shape by injection molding after mixing and kneading a roughly spherical ferrite powder and a polymer material to prepare a ferrite slurry, and can also be formed into a complex shape. It is possible and has advantages such as low cost.

[0004]

However, in the above-mentioned ferrite resin, there is a problem that the initial magnetic permeability cannot be sufficiently increased because a nonmagnetic polymer material is mixed between the ferrite powders. . Especially in recent years,
In the situation where the usage forms of various devices such as the choke coil are expanding, extremely high performance is required depending on the application, and the ferrite resin which is a molding material is accompanied by a further increase in magnetic permeability. Improvement is desired.

On the other hand, in order to increase the magnetic permeability of the ferrite resin, for example, a method of increasing the content of ferrite powder in the ferrite resin has been proposed.
However, in this method, there is a disadvantage that the flowability of the ferrite resin is reduced and the injection moldability is reduced.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and is intended to produce a ferrite powder capable of obtaining a ferrite resin having a high initial permeability and capable of sufficiently meeting the demand for high performance of various devices. The aim is to provide a method.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the achievement of the above-mentioned object, and as a result, classifying the calcined ferrite powder and then sintering the ferrite powder, the inductance is improved and the ferrite powder is formed. It has been found that the magnetic permeability of ferrite resin is improved, and the present invention has been completed.

That is, the present invention relates to a method for producing a ferrite powder, which is preliminarily calcined, pulverized, and finally calcined.
Pulverized ferrite powder with particle size of 0 to 50 μm, 50 to 1
After sieving to 00 μm, 100 to 150 μm, and 150 to 350 μm, the main baking was performed, and each was 0 to 20% by weight,
30-70% by weight, 30-70% by weight, 0-20% by weight
It is characterized by being blended in a certain ratio.

In the method for producing ferrite powder of the present invention, the ferrite powder is preferably a Ni—Cu—Zn ferrite powder. The above Ni-C
The u-Zn-based ferrite powder is 48.5 in terms of Fe ₂ O ₃ .
~ 51 wt%, ZnO 27 ~ 32 wt%, NiO 5
It is a ferrite containing 〜15% by weight and CuO at a rate of 5１５15% by weight.

[0010]

According to the present invention, in the method for producing a ferrite powder obtained by preliminarily calcining, pulverizing, and performing main firing, a ferrite powder having a high inductance is obtained by classifying the ground ferrite powder and then main firing. Can be
A ferrite resin produced using a ferrite powder having a high inductance has excellent initial magnetic permeability.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments to which the present invention is applied will be described in detail based on experimental results.

Embodiment 1 In general, ferrite powder is prepared by weighing, mixing, dehydrating raw materials,
It is manufactured through the steps of drying, calcination, pulverization, main baking, and pulverization. The present invention is characterized in that the pulverizing step after the above-mentioned preliminary calcination is carried out in the same manner as before, but after that, classification is carried out and then main calcination.

Hereinafter, a method for producing a ferrite powder of the present invention will be described. First, 49.5% by weight of Fe ₂ O ₃
31.5% by weight of nO, 9.5% by weight of NiO, CuO
Was weighed in a ratio of 9.5% by weight, mixed, dehydrated and dried, and then calcined in air at 950 ° C. for 4 hours.

The above-mentioned calcination is performed for the purpose of oxidizing the mixed raw materials to some extent so that no decomposition gas is generated during the main calcination, and if the calcination temperature is too high,
It affects the properties after firing. As a result of the present inventors examining the calcination temperature of various ferrite powders, it has been confirmed that the temperature of 800 to 1000 ° C. does not affect the properties of the ferrite powder after calcination. At the time of calcination, the temperature was raised at a rate of 160 ° C./h, maintained at a predetermined calcination temperature, and then gradually cooled.

[0015] Then, after calcining the calcined material as described above, it is coarsely pulverized, and then a sieve is used.
(Powder A), 50-100 μm (powder B), 100-1
The particles were classified into 50 μm (powder C) and 150 to 350 μm (powder D).

Here, the powder A classified as described above
For each of ~ to D, the inductance is measured,
Injection molded products of ferrite resin using each of the powders A to D were prepared, and the magnetic permeability μ _e of these injection molded products was also measured. Table 1 shows the measurement results.

[0017]

[Table 1]

The inductance and the magnetic permeability μ _e are 1
It was measured at kHz. In powder A, the powder is separated and the magnetic permeability μ _e of the injection molded product is
Was not able to be measured, and in the case of powder D, injection molding of a ferrite resin was not possible.

Next, each of the classified powders A to D was added to 10
The main firing was performed at 50 ° C. for 4 hours in the air. During the main firing, the temperature was raised at a rate of 160 ° C./h, and
The temperature was maintained at the main firing temperature of ℃, and then the temperature was gradually cooled.

The Ni-C obtained as described above
For u-Zn ferrite powder, with each measuring the inductance, to create an injection molded product of the ferrite resin using each powder, the magnetic permeability mu _e of the injection molded product was also measured. Table 2 shows the measurement results.

[0021]

[Table 2]

Comparing the results with the values before the main firing shown in Table 1, it can be seen that, for any ferrite powder having any particle size, both the inductance and the magnetic permeability μ _e of the injection molded product are improved.

Thereafter, the Ni-
10% by weight of powder A, 30% by weight of powder B, 50% by weight of powder C, and 10% by weight of Cu-Zn ferrite powder.
By weight, the ferrite powder of this example was completed.

Then, regarding the above ferrite powder,
In addition to measuring the inductance, an injection molded product of a ferrite resin was prepared, and the magnetic permeability μ _e of the injection molded product was measured. The inductance at 1 kHz was 0.1%.
02 μH / g-turn, 1 kHz of injection molded product
Magnetic permeability μ _e in was 33. From this, from the classified powders of the respective particle diameters, the powder blended in the above-described ratio has a higher inductance and magnetic permeability μ _e of the injection molded product.
It can be seen that is improved.

By the way, when measuring the molded magnetic permeability ferrite powder bulk by experiment, until it reaches the temperature T ₁ of is the sintering temperature (℃) magnetic permeability mu _b rises, the present sintering temperature Magnetic permeability μ even if it is higher than T ₁ (° C)
_It turns out that _b does not change. However, a ferrite resin is manufactured using ferrite powder that has been main-baked at an optimum main-baking temperature T ₁ (° C.) or higher during bulk molding, and the magnetic permeability μ of an injection-molded product of this ferrite resin is obtained.
_{When e} was measured, there was a difference in the magnetic permeability μ _e of this injection molded product. When the main firing temperature was a temperature higher by 50 to 150 ° C. than the above T ₁ , the magnetic permeability μ _e of the injection molded product was most improved.

With respect to the ferrite powder prepared in the present example, the optimum main firing temperature T ₁ (° C.) at the time of bulk molding was measured to be 950 ° C. Therefore, in this embodiment, the main firing temperature is set to a temperature higher by 50 to 150 ° C. than T _1.
The temperature was set to 50 ° C.

A method for evaluating the inductance of the ferrite powder will be described below. In the present embodiment, as shown in FIG. 1, a coil 2 is formed by winding a cotton-wound copper wire around a cylindrical portion 3 of a plastic syringe 1 for 100 turns, and the cylindrical portion 3 is filled with ferrite powder (not shown). And measured by an impedance analyzer (not shown) connected to the coil 2. At this time, absorbent cotton 5 was packed at the tip of the cylindrical portion 3 so that air other than air would not escape from the air hole 3a provided at the tip of the cylindrical portion 3. The amount of ferrite powder to be charged into the cylindrical portion 3 is set to 20 g, and the rear end portion 6a of the rubber 6 provided at the front end of the piston portion 4 in order to keep the filling pressure constant matches the rear end portion 2a of the coil. As described above, the piston part 4 was inserted into the cylindrical part 3, and the filling pressure of the ferrite powder was kept constant.

Comparative Example 1 Here, for comparison, the characteristics of ferrite powders prepared without classification after calcination were examined. To prepare the ferrite powder of this comparative example, first, after calcination, up to the step of coarse pulverization is performed in the same manner as in the above example,
The main firing was performed without classification. Then, the classification is performed for the first time, and 0 to 50 μm using a sieve.
(Powder E), 50-100 μm (Powder F), 100-1
The particles were classified into 50 μm (powder G) and 150 to 350 μm (powder H).

The inductance of each of the ferrite powders E to H classified as described above is measured, and an injection molded product of ferrite resin is prepared using each of the powders E to H. The magnetic susceptibility μ _e was also measured. Table 3 shows the measurement results.

[0030]

[Table 3]

Then, the ferrite powders E to H obtained as described above were adjusted so that powder E was 10% by weight, powder F was 30% by weight, powder G was 50% by weight, and powder H was 10% by weight. Was blended. For this ferrite powder, the inductance was measured, an injection molded product of a ferrite resin was prepared, and the magnetic permeability μ _e of the injection molded product was also measured. The inductance at 1 kHz was 0.095 μm.
H / g · turn, and the magnetic permeability μ _e of the injection molded product at 1 kHz was 30.

As a result, the ferrite powder of Example 1 subjected to classification before the main firing was compared with the ferrite powder of Comparative Example 1 subjected to the classification after main firing in terms of inductance and inductance of the ferrite powder for each particle size. It can be seen that both the magnetic permeability μ _e of the injection molded product of the ferrite resin is improved. Further, it can be seen that, in the compounded ferrite powder, both the inductance and the magnetic permeability μ _e of the injection molded product of the ferrite resin are improved.

[0033]

[Effect] As is clear from the above description, in the present invention, the ferrite powder obtained by preliminarily calcining, coarsely pulverizing, classifying, and then sintering, and blending particles of each particle size is obtained. It shows that a large inductance is exhibited. Therefore, when a ferrite powder having a high inductance is used, a ferrite resin having an excellent initial magnetic permeability can be produced. Further, by obtaining such a ferrite resin, it is possible to provide a high-performance molding material for various devices such as a choke coil, and it is expected that the use form of these devices can be further expanded.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing the configuration of a measuring device used for measuring the inductance of ferrite powder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container 2 ... Coil 3 ... Tube part

Continuation of front page (56) References JP-A-48-17500 (JP, A) JP-A-55-103705 (JP, A) JP-A-3-278502 (JP, A) JP-A-3-64005 (JP) , A) JP-A-2-241007 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 1/12-1/375

Claims (2)

(57) [Claims] 1. A method for producing a ferrite powder, comprising: calcination, crushing, and main calcination, wherein the crushed ferrite powder has a particle size of 0 to 50 μm, 50 to 1 μm.
After classification into 00 μm, 100 to 150 μm, and 150 to 350 μm, main firing was performed, and 0 to 20% by weight,
30-70% by weight, 30-70% by weight, 0-20% by weight
A method for producing a ferrite powder, characterized in that the ferrite powder is blended in an appropriate ratio. 2. The method for producing ferrite powder according to claim 1, wherein the ferrite powder is a Ni—Cu—Zn ferrite powder.