KR100302071B1 - Method for preparing soft magnetic ferrite - Google Patents

Abstract

PURPOSE: A method for preparing soft magnetic ferrite is provided to have a plastic temperature lower than the melting point of Ag by suitably controlling the components and content of start material and additive, as well as to have the electromagnetic properties of permeability;150-270 and Q;220-260 at 500MHz when plasticized for 3 hours at 890 deg.C. CONSTITUTION: The soft magnetic ferrite is prepared by breaking, calcining, forming and plasticizing start material comprising Fe2O3 and MO. The start material consists of Fe2O3 of 49.0-49.6 mol%, NiO of 10.0-12.0 mol%, ZnO of 25.0-28.0 mol% and CuO of 12.0-16.0 mol%. In addition, the start material is calcined and broken, and then at least one selected from a group consisting of CuO of 0.5-5.0 wt.%, SiO2 of 500-1000 ppm, CoO of 0.1-1.0 wt.%, Co2O3 of 0.1-1.0 wt.%, Co3O4 of 0.1-1.0 wt.%, Bi2O3 of 0.3-0.75 wt.%, V2O5 of 0.3-1.0 wt.% and ZnO of 0.5-5.0 wt.% are added to the broken calcination powder.

Description

Manufacturing method of soft magnetic ferrite

1 (a) and 1 (b) are graphs showing the change in Q value according to the frequency change of Inventive Example (A) and Comparative Example (1).

2 (a) and 2 (b) are graphs showing changes in Ls values according to frequency changes in Inventive Example (A) and Comparative Example (1).

3 is a heat treatment curve applied to this embodiment.

[Purpose of invention]

[Technical field to which the invention belongs and the prior art in that field]

The present invention relates to a method of manufacturing soft magnetic ferrite used in a chip inductor, which is a kind of surface mount component (hereinafter referred to as "SMD"), and more specifically, can be fired at a temperature of 1000 ° C or lower, The present invention relates to a method for manufacturing a Fe-Ni-Cu-Zn soft magnetic ferrite having a high Q value required for a coil for an inductor in a band.

Recently, as part of miniaturization and thinning of electronic components, SMD is rapidly progressing, and its field has been applied to simple parts such as capacitors, resistors, coils, and the like.

Among such SMD electronic components, chip inductors are applied to various electronic circuits due to high loss and excellent noise rejection characteristics in electromagnetic circuits. Applications include cellular phones, office automation (OA), microcomputer appliances, automotive controllers, and A / V systems.

The structure of the chip inductor is a form in which internal electrodes connecting both terminals, which are input / output terminals, form a circular magnetic field inside the magnetic material. The inductance generated at this time removes noise at a specific frequency.

The chip inductor having the above structure generally uses Ag paste having low loss in the high frequency band as the internal electrode and soft magnetic ferrite as the external magnetic material. Therefore, firing, which is the final step to commercialize the chip inductor and obtain the desired characteristics, should be performed under the condition that the soft magnetic ferrite, which is the external magnetic material, can exhibit the electromagnetic characteristics without damage to the Ag paste, the internal electrode.

In other words, in order to commercialize the chip inductor to have the desired electromagnetic characteristics, the chip inductor must be fired at a temperature in the range of 40-50 ° C. or lower than the melting point of the internal electrode Ag (100% purity). Magnetic ferrite must also have sufficient spinelization to be able to have the desired electromagnetic properties.

However, the soft magnetic ferrite that has been developed or proposed in the past has the following problems when used in the chip inductor because the basic firing temperature is in the range of 1050-1350 ° C., and thus it is difficult to apply to the chip inductor.

When the chip inductor is manufactured using soft magnetic ferrite having a firing temperature in the range of 1050-1350 ° C., the internal electrode is made of Ag-Pd because it is difficult to be completely fired at the optimum firing temperature range of the chip inductor at 910-920 ° C. In addition, when only Ag is used as the internal electrode, the number of turns of the internal electrode increases because of low electromagnetic characteristics compared to the frequency. In addition, it is difficult to obtain high Q values at high frequencies.

Therefore, as a result of research on soft magnetic ferrite that can be fired at a temperature range of 40-50 ° C. or lower than the melting point of Ag, firing accelerators are mainly added to soft magnetic ferrite having a conventional firing temperature of 1050-1350 ° C. It is applied to chip inductor with the temperature lowered to 900-950 ℃.

However, if the firing temperature of the soft magnetic ferrite is lowered by adding the firing accelerator as described above, the original electromagnetic properties of the soft magnetic ferrite are about 50-60% (permeability: 30-40%, Q: 60-70%). There is a disadvantage of deterioration. This is because the calcination promoter causes coarsening of the partial crystal grains in the process of promoting the calcination reaction.

Therefore, in the case of soft magnetic ferrite in which the firing accelerator is added to lower the firing temperature, the change in the electromagnetic characteristics is too severe, and the application range thereof is extremely limited.

In addition, in recent years, even if the same components are different according to the diversification of electronic components, the soft magnetic ferrite that shows the characteristics suitable for each frequency band is required.

[Technical problem to be achieved]

Accordingly, the present inventors have conducted research and experiments to solve the problems of the conventional soft magnetic ferrites to provide soft magnetic ferrites that can be fired at low temperatures and exhibit excellent electromagnetic characteristics in each frequency band to be used. As a result, it was confirmed that the firing temperature and the electromagnetic characteristics of the soft magnetic ferrite were greatly influenced even if the composition ratio of each component was changed by 0.02 mol%. Proposed.

According to the present invention, the firing temperature is lower than the melting point of Ag, an internal electrode, and the magnetic permeability at a frequency of 500 KHz at 890 ° C. for 3 hours by appropriately controlling the components, contents, and additives of the starting material of the soft magnetic ferrite. To provide a method for producing a soft magnetic ferrite having electromagnetic characteristics of Q: 220-260.

[Configuration of Invention]

The present invention relates to a method for producing soft magnetic ferrite comprising crushing, calcining, crushing, shaping and firing a starting material composed of iron oxide (Fe ₂ O ₃ ) and metal oxide (MO) as required. The starting material is composed of Fe ₂ O ₃ : 49.0-49.6 mol%, NiO: 10.0-12.0 mol%, ZnO: 25.0-28.0 mol% and CuO: 12.0-16.0 mol%, which is calcined by crushing and then the crushed calcined With respect to the total weight of the starting material as an additive to the powder, CuO: 0.5-5.0%, SiO ₂ : 500-1000ppm, CoO: 0.1-1.0%, Co ₂ O ₃ : 0.1-1.0%, Co ₃ O ₄ : 0.1 -1.0%, Bi ₂ O ₃ : 0.3-0.75%, V ₂ O ₅ : 0.3-1.0% and ZnO: 0.5-5.0% of the selected one or more selected from the group consisting of It relates to a method for producing magnetic ferrite.

Hereinafter, the present invention will be described in more detail.

In order to achieve the above object, in the present invention, it is preferable to prepare a starting material composed of iron oxide (Fe ₂ O ₃ ) and metal oxide (MO) as needed, and the reason is as follows.

Fe ₂ O ₃ is the main component of soft magnetic ferrite, which is composed of spinel lattice. Among these, Fe ^{+ 3} ions induce electron diffusion in the crystals, which not only affect the movement of the magnetic wall but also have inverse spinel structure. If the content is 49.0 mol% or less (hereinafter, referred to as '%'), the Q property is sharply deteriorated. If the content is 49.6% or more, the hardness of the material is high. Since there is a problem of deterioration, the content of Fe ₂ O ₃ is preferably limited to 49.0-49.6%.

NiO is a component that improves high frequency characteristics by forming Fe ⁺³ (Ni ⁺² · Fe ₂ ⁺³ O ₄ ) reverse spinel magnetic moment structure. When the content is less than 10.0%, NiO decreases and Porosity, which is a crystal defect, is generated, and in the case of 12.0% or more, since the workability is deteriorated due to the increase in the firing temperature and the rapid increase in the hardness of the material due to the high frequency movement of the Q band, the NiO content is It is desirable to limit it to 10.0-12.0%.

ZnO is a Fe ⁺³ (Zn ⁺² · Fe ₂ ⁺³ O ₄ ) positive spinel magnetic moment structure. When the content is less than 25.0%, ZnO has a problem of decrease of permeability and Q characteristic. Since there is a problem of temperature increase and Tc temperature drop, the content of ZnO is preferably limited to 25.0-28.0%.

CuO is a Fe ⁺³ [Cu ⁺² · Fe ₂ ⁺³ O ₄ ) structure, and is a component that promotes sintering. When the content is 12.0% or less, there is a problem of increasing the firing temperature and decreasing the sintering density. , 16.0% or more, there is a problem of lowering the permeability and Q value due to precipitation between grain boundaries, it is preferable to limit the content of CuO to 12.0-16.0%.

In the present invention, after the starting material is prepared as described above, soft magnetic ferrite is manufactured by a conventional method, which will be described in more detail.

The ball mill was carried out for 4-5 hours while maintaining the weight ratio between the starting material and (pure + ball) at 1: 5 so that the dispersed particle size was 0.05-0.1 μm and then the water was dried in a drying oven at 350-400 ° C. Remove it completely and grind to the size of 10-20mm.

The powder pulverized in this way is charged with Al ₂ O ₃ or zircon, and then calcined under an oxidizing atmosphere such that the spinelation of the magnetic material is performed at a temperature of about 50-100 ° C. lower than the final firing (main firing) in an electric furnace.

The calcined magnetic body is crushed again to promote mixing of unreacted oxides and to reduce particle size. At this time, the fracture particle size is preferably about 0.5-1 μm.

The crushed powder is dried and sieved to equalize the particle size, and then granulated by adding a binder (binder), molded and finally calcined to produce soft magnetic ferrite.

On the other hand, in the present invention, in order to improve the electromagnetic properties of the soft magnetic ferrite and the reactivity between the grains in the final firing, as an additive to the calcined powder, CuO: 0.5-5.0%, SiO ₂ : 500-1000 ppm, CoO: 0.1-1.0%, Co ₂ O ₃ : 0.1-1.0%, Co ₃ O ₄ : 0.1-1.0%, Bi ₂ O ₃ : 0.3-0.75%, V ₂ O ₅ : 0.3-1.0% And ZnO: 0.5-5.0% by adding one or two or more selected from the group consisting of, after the mixed grinding, soft magnetic ferrite may be prepared by the above-described method.

The additive serves as a catalyst to increase the reactivity of the crystal grain surface when the compounds of the starting materials Fe ₂ O ₃ , NiO, CuO and ZnO are crystallized in the final firing step.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Starting materials were quantified to have a composition as shown in Table 1 below.

TABLE 1

The starting material quantified as shown in Table 1 was subjected to inconsistency for 3 hours while maintaining the weight ratio with (pure + ball) at 1: 5, and wet crushed to have a dispersion particle size of 0.1-l μm. The wet crushed and mixed raw materials were completely removed from the dry oven at 200-500 ° C., and then crushed to a size of 2-5 mm, charged to the main bowl, and calcined in an electric furnace at an oxidizing atmosphere at a temperature of 750 ° C. for 3 hours.

The calcined powder magnetic material was pulverized into a wet ball mill to a particle size of 0.5-1 μm and dried, and then granulated by 100 mesh sieve, and granulated by adding 8% by weight of 5% PVA (poly vinyl alchol) solution as a binder. Then, by adding the molding lubricant steriaic acid-Zn to the granulated powder to form a cyclic troidal core with a molding pressure of 5kg / ° cm ² and a molding density of 2.9-3.3g / cc, the temperature gradient as shown in FIG. It was charged into an electric furnace having and fired.

As described above, the enamelled copper wire (0.6PAI) was wound 20 times on the finished specimen as described above, and the Q value was measured in the frequency range of 10KHz-40MHz.

As shown in FIG. 1, in the case of Inventive Example (A) satisfying the scope of the present invention, it can be seen that the Q value of 210-240 is shown in the frequency band of 200-800KHz. On the contrary, in the case of the comparative example (1) which does not satisfy the scope of the present invention, it can be seen that the above Q value cannot be obtained in the frequency band.

In addition, the permeability according to the frequency change was calculated by the following equation using the Ls value, which is the inductance value shown in FIG.

(Ls: inductance value, 1: magnetic field, A: magnetic cross-section area, N: coil winding player, μ _o : permeability)

As a result, in the case of Inventive Example (A) satisfying the scope of the present invention, an excellent permeability value was obtained in the frequency band as compared with the case of Comparative Example (1) outside the scope of the present invention in the high frequency band of 200-800KMz. It can be seen that.

Example 2

In order to confirm the change in the magnetic properties of the soft magnetic ferrite according to the change of the final firing temperature, the soft magnetic ferrite of Inventive Example (A) of Example 1 was maintained while keeping the other conditions the same as those of Example 1 As shown in Table 2, after the final firing while only changing the firing temperature, the enamelled copper wire (0.6PAI) was wound 20 times to measure the electromagnetic characteristics at a frequency of 500 KHz and the results are shown in Table 2 below.

TABLE 2

As can be seen in Table 2, when the firing temperature is in the range of 40-50 ℃ lower than the melting point of Ag 100% of the internal electrode (890, 900 ℃) Q value 240-260, permeability: 150-170 range While the desired electromagnetic characteristic values (Q value and permeability) range are satisfied, when the firing temperature is lower than this (870 ° C), the spinelization of the soft magnetic ferrite does not proceed sufficiently and the permeability of the electromagnetic characteristics deteriorates and When the temperature is high (950 ℃) it can be seen that the electromagnetic Q of the electromagnetic characteristics is rapidly deteriorated to obtain the desired Q value.

Example 3

In order to confirm the magnetic property change and the reactivity change according to the addition of the additive, calcining and pulverizing Inventive Example (A) in the soft magnetic ferrite prepared by the method of Example 1, and then adding the additive as shown in Table 3 below. After preparing the soft magnetic ferrite of the present invention, the electromagnetic properties (Q value and permeability) were measured at 500 KHz, and the results are shown in Table 3 below.

TABLE 3

As can be seen from Table 3, in the case of Inventive Examples (A1-A4) satisfying the scope of the present invention, Q of the electromagnetic characteristics compared to the case of Comparative Examples (1a-1b) that do not satisfy the scope of the present invention It can be seen that the value is better.

It is presumed that the better properties when the additive is added are because the additive acts as a catalyst to increase the reactivity of the surface between the crystal grains during final firing.

[Effects of the Invention]

As described above, the present invention controls the components and contents of the starting material in the preparation of the soft magnetic ferrite and injects the additives appropriately, so that the firing temperature is 1000 ° C. or less and the melting point of the internal electrode Ag when applied to the chip inductor. Final firing at low temperatures is possible, and soft magnetic ferrites with Q values of 220-260 and permeability values of 150-270 can be produced at a frequency of 500 KHz for three hours firing at 890 ° C. In addition, since low-temperature firing is possible when applied to a chip inductor, the existing precious metal (Ag-Pb alloy) internal electrode is replaced with Ag alone, thereby reducing the manufacturing cost.

Claims (1)

In the method for producing soft magnetic ferrite comprising crushing, calcining, crushing, shaping and firing a starting material composed of iron oxide (Fe ₂ O ₃ ) and metal oxide (MO) as required, the starting material is In mole%, Fe ₂ O ₃ : 49.0-49.6%, NiO: 10.0-12.0%, ZnO: 25.0-28.0% and CuO: 12.0-16.0%, calcined and crushed and then added to the crushed calcined powder CuO: 0.5-5.0%, SiO ₂ : 500-1000ppm, CoO: 0.1-1.0%, Co ₂ O ₃ : 0.1-1.0%, Co ₃ O ₄ : 0.1-1.0%, based on the total weight of the starting material Soft magnetic ferrite characterized by adding one or two or more selected from the group consisting of Bi ₂ O ₃ : 0.3-0.75%, V ₂ O ₅ : 0.3-1.O% and ZnO: 0.5-5.0% Manufacturing method.