JP2760026B2 - Ferrite magnetic body and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low shrinkage ferrite magnetic material obtained by binding and solidifying a highly crystalline ferrite magnetic powder with a glass material, and a method for producing the same. Kinds of ferrite magnetic materials are used as useful electronic components.

2. Description of the Related Art Conventional ferrite magnetic material manufacturing methods mainly include a powder metallurgy method, that is, a sintering method that requires steps of powder molding and high-temperature firing.

When a ferrite magnetic material is produced, the starting materials are blended in a predetermined ratio, calcined under appropriate conditions, degassing and a certain amount of solid-phase reaction are advanced (this is called calcined powder), and then pulverized and molded. Through the steps of granulation and compaction, the compact is fired at a temperature higher than the calcination temperature in an appropriate atmosphere to produce a polycrystalline ferrite sintered body having desired magnetic properties and mechanical strength. It has gained.

FIG. 2 shows a schematic diagram of the fine structure of this polycrystalline ferrite sintered body. In FIG. 2, 5 is a crystal grain, 6 is a grain boundary, 7 is a grain boundary pore, and 8 is a pore of the crystal grain 5.

The calcining temperature in the above process is set between 700 and 1000 ° C., at which the starting material of a predetermined blending ratio starts the solid-phase reaction, and the main calcining temperature for sufficient sintering is the material and composition of the calcined powder and the granules. Although it depends on the diameter and shape, it is usually a high temperature of 1000 to 1400 ° C. The firing atmosphere at this time is the required material,
An oxidizing atmosphere or a non-oxidizing atmosphere is selected depending on the composition.

A disadvantage of the ferrite sintering method is that sintering of the calcined powder compact in the main sintering step necessarily causes a dimensional change. In other words, after the final firing, usually 10-20%,
When it is large, it shrinks more, and the dimensional accuracy and yield of the sintered product are deteriorated. Therefore, post-processing, which is mechanical processing such as cutting and polishing, is required.

Shrinkage during the sintering process described above occurs for the following reasons. That is, the compact obtained by simply pressing the calcined powder usually has a low compaction density because a powder having a particle size of about 2 to 5 μm or less is used. That is, although the powders are in contact with each other, there are still many voids, When heated at a temperature of 700 to 1000 ° C. or more, inter-diffusion of atoms constituting the particles occurs at the contact portion between the calcined powders, and the sintering phenomenon starts. As a result, the voids between the calcined powders decrease with the progress of sintering, and shrink more than 20% when large.

Therefore, it is important to make the temperature rise and the temperature at the time of main firing relatively slow in order to make the sintering uniform and not to receive the thermal shock to the compact.

As a result, the main firing step may take two days even if it is usually at least half a day or longer.

There have been many studies to improve the disadvantages of the ferrite firing method. Among them, regarding the problem of shrinkage of the sintered body, various methods have been studied to reduce the shrinkage as much as possible and to control the shrinkage at a constant level.However, in order to secure the performance and characteristics of ferrite, some shrinkage is avoided. The fact is that it cannot be done. For example, JP-A-58-135133
As described in JP-A-58-135606, after calcined ferrite powder and glass powder are mixed, firing is performed at a temperature at which densification (sintering) of ferrite proceeds. By adding the glass powder to the periphery of the ferrite particles, the densification of the ferrite can be partially suppressed to obtain a sintered body having a low shrinkage. However, even in this case, since the calcined powder production temperature is lower than the final firing temperature of the compact afterwards, mutual diffusion occurs between the calcined powders that are still in direct contact during the final firing, so that the compaction shrinkage phenomenon Was unavoidable and in fact shrank by a few percent.

Problems to be Solved by the Invention As described above, in the conventional ferrite sintered body, the more the sintering is advanced in order to obtain the desired performance, the larger the shrinkage is, and conversely, if the sintering is suppressed, the performance is reduced. Can not be secured, it is difficult to balance. However, sintered ferrites are widely used as electronic parts and device materials, and their performance and high dimensional accuracy are increasingly regarded as important.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a glass-bound ultra-low-shrinkage ferrite magnetic material having almost no shrinkage and excellent magnetic properties, and a method of manufacturing the same at a low cost. Is what you do.

Means for Solving the Problems The ferrite magnetic material of the present invention for solving the above problems has at least sufficiently advanced ferrite formation at high temperature firing.
A mixture of a highly crystalline ferrite magnetic powder containing Cu and a glass powder having a softening point lower than the sintering temperature in a range of not less than the softening temperature of the glass powder and not more than the sintering temperature of the highly crystalline ferrite magnetic powder. The heat treatment is performed so that the high crystalline ferrite magnetic powder is bound with a glass material.

Action Since the ferrite magnetic powder containing at least Cu to be used has already been crystallized to near perfection by high-temperature sintering, sintering between the highly crystalline ferrite magnetic powders in the subsequent low-temperature molding heat treatment This hardly occurs, and the glass powder mixed between the high crystalline ferrite magnetic powders is simply melted to bind the high crystalline ferrite magnetic powder. As a result, the porosity in the molded body does not change much before and after the heat treatment, so that a novel ferrite magnetic body having high dimensional accuracy close to the mold forming dimensions and excellent magnetic properties can be obtained.

Furthermore, the heat treatment of the molded body does not expect sintering properties, and it is basically necessary to melt the glass powder as described above and flow between the high-crystalline ferrite magnetic powders and obtain a binding effect. It is much shorter than the main firing time of the method. Therefore, equipment costs and electricity costs are low, and the manufacturing method is simple, so that it can be manufactured at low cost.

In addition, in the case of soft ferrite, high resistance is desired because it is necessary to reduce eddy current loss of the ferrite as much as possible.However, according to the present invention, even when a Mn-Zn ferrite having a relatively low electric resistance is melted and solidified, a glass component is hardened. Since the highly crystalline ferrite magnetic powder is electrically insulated, the resistance value can be increased and the high frequency characteristics can be improved.

Examples Hereinafter, examples of the present invention will be described.

That is, according to the present invention, as shown in FIG.
And a glass material 2 that softens and melts at a firing temperature or lower.

Specifically, the highly crystalline ferrite magnetic powder 1 and the glass powder are mixed well, and the granulated mixed granule is pressed and then mixed with the highly crystalline ferrite magnetic powder 1 in the compact. A ferrite magnetic material in which the above-mentioned glass powder is softened and melted so that the highly crystalline ferrite magnetic powder 1 is simply bound with the glass material 2 and solidified. In addition, 3 in the figure
Indicates voids, and 4 indicates pores in the highly crystalline ferrite magnetic powder 1.

The highly crystalline ferrite magnetic powder 1 used here is sufficiently ferritized by firing at a high temperature, and usually preferably fired at 900 ° C. or higher.

When it is desired to obtain a soft ferrite magnetic substance, the smaller the coercive force Hc of the highly crystalline ferrite magnetic powder 1 is, the better the size of the magnetic particles is. Thus, the packing density of the highly crystalline ferrite magnetic powder 1 is preferably small. Actually go down 10
A diameter of 0 to 200 μm is suitable.

Next, the temperature should be equal to or lower than the softening temperature of the glass powder that binds the high crystalline ferrite magnetic powder 1. However, considering the application of the ferrite magnetic material according to the present invention, the lower limit is from the viewpoint of heat resistance.
It is desirable that the temperature be 300 ° C. or higher. The amount of the glass powder added to the high-crystalline ferrite magnetic powder 1 is preferably 0.3 to 30% by weight. If the amount is less than 0.3% by weight, the binding effect of the high-crystalline ferrite magnetic powder 1 is so small that mechanical strength cannot be secured. On the other hand, when the amount of glass is more than 30% by weight, the binding force becomes sufficiently strong, but the non-magnetic amount increases, so that the magnetic properties of the ferrite magnetic material are not significantly deteriorated.

The heat treatment of the mixed molded body of the high crystalline ferrite magnetic powder 1 and the glass powder is performed mainly because the heat treatment of the mixed molded body of the glass powder is mainly for melting and infiltration of the glass powder. In addition, the time required for raising and lowering the temperature may be 3 hours or less.

The heat treatment temperature may be basically higher than the softening temperature of the glass. However, as the temperature approaches the sintering temperature of the highly crystalline ferrite magnetic powder 1, especially when the temperature becomes 800 ° C. or more, the glass material 2
Has been obtained, and the favorable effect that the magnetic properties are excellent despite the low shrinkage property was obtained.

 Hereinafter, specific examples will be described.

(Example _{1~10) Fe 2 O 3 48mol%} , NiO13mol%, ZnO34mol%, CuO5mol%
The obtained starting mixed granulated powder was calcined at 1320 ° C. for 6 hours and pulverized to prepare a Ni-Zn-Cu soft ferrite main calcined powder having an average particle diameter of 70 μm. As a result of X-ray analysis of this powder, a sharp spinel structure diffraction line unique to soft ferrite was obtained, and it was confirmed that the powder was a magnetic powder having extremely high crystallinity.

The softening point (T
d) Alkali-free lead borosilicate glass powder having an average particle size of 1 μm at 370 ° C. was added to each of 0, 0.1, 0.3, 0.5, 1, 3, 5, and 1
After adding 0, 30, and 40 wt% each, mixing and granulating, 3 ton / cm ²
Under the above pressure, ring-shaped molded articles having an inner diameter of 7 mmφ, an outer diameter of 12 mmφ, and a thickness of 3 mm with different glass contents were produced. The molded articles were individually placed in an electric furnace and heated at 1200 ° C. for 60 minutes in air to obtain a glass-bound ring-shaped ferrite core.

Table 1 shows the material properties of the samples of Examples 1 to 10.

In Examples 1 to 10, the core tensile strength increases as the glass content increases, but the glass content is 0.3 wt%.
If it is less, it cannot be used practically. Also, 30wt%
If it is larger, the magnetic properties will deteriorate.

(Comparative Example 1) A starting mixed granulated powder having the same composition as in Example 1 was prepared.
Perform calcination at 1000 ° C for 2 hours, finely pulverize to 2 to 5 μm,
After granulation, a ring-shaped molded product of the same size was produced in the same manner as in Example 1.

This molded product was placed in an electric furnace, fired in air at 1300 ° C. for 3 hours, then cooled and cooled to obtain a Ni-Zn-Cu ferrite sintered ring core. The material properties of this sample are shown in Table 1.

Comparative Example 2 The same calcined powder used in Comparative Example 1 was mixed with the same glass powder used in Example 7 in an amount of 5 wt%, mixed and granulated. A shaped article was produced.

This molded product was placed in an electric furnace and heated at 1200 ° C. for 60 minutes in air to obtain a glass-containing type ring-shaped ferrite core.

 The material properties of this sample are shown in Table 1.

In Comparative Examples 1 and 2, the core shrinkage becomes 10% or more and a low shrinkage cannot be realized.

(Examples 11 to 15) 5 wt% of the same glass powder was added to the same ferrite main firing powder used in Example 7, mixed and granulated, and then 3 ton /
Five ring-shaped molded articles having an inner diameter of 7 mmφ, an outer diameter of 12 mmφ, and a thickness of 3 mm were produced at a pressure of cm ² .

Each of these moldings was placed in an electric furnace one at a time at 1300 ° C.
Heat treatment was performed in air at 1000 ° C., 800 ° C., 600 ° C., and 450 ° C. for 60 minutes to obtain a glass-bound ring-shaped ferrite core.

Table 2 shows the material properties of the samples of Examples 11 to 15 described above.

As the heat treatment temperature decreases, the magnetic properties and the mechanical strength of the core decrease, and it is practically difficult to use at a treatment temperature lower than 800 ° C.

(Example 16) 5 wt% of alkali-free lead borosilicate glass powder having a softening point (Td) of 700 ° C and an average particle diameter of 1 µm was added to the same ferrite main firing powder used in Example 1 and mixed and granulated. After 3 ton / cm ² pressure, inner diameter 7mmφ, outer diameter 12mmφ, thickness 3mm
Was produced.

This molded product was heated in air at 1200 ° C. for 60 minutes to obtain a glass-bound ring-shaped ferrite core.

 Table 2 shows the material properties of Example 16 described above.

In the above Examples and Comparative Examples, the initial magnetic permeability was measured according to the JIS standard (C2561).
A sample was prepared by further winding an insulated copper wire of 0.26 mmφ all around.

Next, this self-inductance was measured with a Maxwell bridge when the strength of the measured magnetic field was 0.8 (A / m) or less, and the initial magnetic permeability at a frequency of 1 (MHz) was calculated from this.

In addition, the saturation magnetic flux density is determined by JIS standard (C256
According to 1), the magnetic flux density at a magnetic field of 10 (Oe) was measured by a magnetic fluxmeter method.

Furthermore, the shrinkage was measured by measuring the outer diameters of the ring-shaped molded product before the heat treatment and the ring-shaped ferrite core after the heat treatment, and calculating the dimensional shrinkage before and after the heat treatment. According to JIS standard (C2564), two thin wires were passed through the ring core once, and one of them was fixed, and the other one was pulled vertically at a speed of 5 mm / min or less. The tensile load at the moment when the core was broken was measured and determined.

Effects of the Invention As described above, according to the present invention, a glass-bound high-density low-shrink ferrite magnetic material has good dimensional accuracy, and becomes a magnetic material with excellent magnetic properties, and can be manufactured at low cost. It can provide excellent effects as useful electronic components and materials used in various magnetic products.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fine structure of a ferrite magnetic material according to the present invention, and FIG. 2 is a schematic diagram of a fine structure of a conventional typical sintered ferrite magnetic material. 1 ... High crystalline ferrite magnetic powder, 2 ... Glass material,
3 voids 4 pores 5 crystal grains 6 grain boundaries
7 ... grain boundary pore, 8 ... pore.

Claims (5)

(57) [Claims] A mixture of a highly crystalline ferrite magnetic powder containing at least Cu, which has been sufficiently ferritized by firing at a high temperature, and a glass powder having a softening point lower than the firing temperature,
A ferrite magnetic material obtained by heat-treating the high-crystalline ferrite magnetic powder in a temperature range not lower than the softening temperature of the glass powder and not higher than the firing temperature of the high-crystalline ferrite magnetic powder, and binding the high-crystalline ferrite magnetic powder with a glass material. 2. The ferrite magnetic material according to claim 1, wherein the heat treatment temperature of the mixture of the high crystalline ferrite magnetic powder and the glass powder is 800 ° C. or higher and the firing temperature of the high crystalline ferrite magnetic powder or lower. 3. The ferrite magnetic material according to claim 1, wherein the material ratio of the glass to the high crystalline ferrite magnetic powder is 0.3 to 30 wt%. 4. A high-crystalline ferrite magnetic powder containing at least Cu, which has been sufficiently ferritized by high-temperature firing, mixed with a glass powder having a softening point lower than the firing temperature, and the mixture obtained by granulation is heated. And a method of producing a ferrite magnetic material in which the glass powder mixed in the compact is softened and melted by a heat treatment at a temperature not higher than the firing temperature of the ferrite magnetic powder to bind the highly crystalline ferrite magnetic powder with a glass material. 5. The method for producing a ferrite magnetic material according to claim 4, wherein the heat treatment temperature of the mixture of the high crystalline ferrite magnetic powder and the glass powder is set to 800 ° C. or higher and the firing temperature of the high crystalline ferrite magnetic powder or lower.