JP3300838B2 - Oxide magnetic material for inductor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide magnetic material, and more particularly to an oxide soft magnetic material which can be fired at a low temperature and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, oxide magnetic materials have been used as high frequency materials because of their higher electrical resistance than metal materials. Among them, spinel-type ferrite is most frequently used as a high frequency material because it exhibits excellent soft magnetism, uses an inexpensive raw material, and can easily obtain a sintered body by powder metallurgy.

In recent years, devices using these high-frequency materials have been significantly reduced in size and weight due to higher frequencies.

[0004] Therefore, the inductance elements used in these devices are also required to be reduced in size and weight.
In addition, there has been a need to manufacture devices in a shape that makes automatic mounting easier. Such an element is called a so-called surface mount component.

Therefore, it is necessary that the configuration of these inductance elements is significantly finer than that of a conventional bulky element.

One of the useful methods for manufacturing such a surface mount component is to use a slurry in which powders of the respective constituent materials are dispersed, sinter a molded body in which each circuit is formed by printing or the like, and form an inductance element. There is a method of forming. In this method, the electric conductor and the magnetic ferrite are formed independently.

[0007] The sintering temperature of a conventionally used ferrite powder compact is 1050 to 1400 ° C. Therefore, when these powders are used, the conductor portion must be sintered and not broken at the sintering temperature, and diffusion into the magnetic ferrite portion must be suppressed.

Further, when the magnetic ferrite portion and the electric conductor portion are configured to be in contact with each other, the ferrite material constituting the magnetic ferrite portion needs to be a high electric resistor.

From the above, when each material of the magnetic ferrite portion and the electric conductor portion of the high-frequency inductance element is selected, Ni-based ferrite is used as the material for the magnetic ferrite portion, and an Ag-Pd alloy is used as the electric conductor portion. Can be determined to be useful.

[0010]

However, the Ag-conductor used for the electric conductor of the high-frequency inductance element has a disadvantage.
In a Pd alloy, Pd is extremely expensive and increases the electric resistance. Therefore, it is desirable to reduce the content of Pd. Therefore, if the electric conductor portion can be constituted only by Ag, it will be extremely useful industrially.

In order to form the electric conductor portion by sintering Ag alone, the sintering temperature of the ferrite material of the magnetic ferrite portion needs to be 900 ° C. or less. The sintered state of the ferrite material at this time should be a state without water absorption because it is not preferable that the characteristics (inductance, impedance, etc.) of the element change with the environment.
That is, it is preferable that the pores present in the ferrite sintered body be in a closed state.

On the other hand, in the closed state, there are advantages that the mechanical strength of the sintered body is improved and the amount of change in inductance due to the sintering temperature is reduced.

In the above, only the problem on the characteristics of the element has been described. The fact that sintering can be performed at a low temperature means that not only the sintering energy can be significantly reduced but also the sintering equipment cost can be significantly reduced. And is extremely useful industrially.

Further, in the above-described device, in order to integrally sinter the respective materials of the Ag conductor portion and the magnetic ferrite portion,
Reaction occurs at the interface between the materials. For this reason, the electrical resistance of the Ag conductor portion fluctuates, which causes variations in the characteristic values of the inductor element and the impedance element.

Therefore, the reduction in the variation in the electric resistance of the Ag conductor portion improves the quality of the element,
It is extremely useful in industry.

Accordingly, a technical problem of the present invention is to provide an oxide magnetic material for an inductor which can improve the mechanical strength by low-temperature sintering, reduce the change in inductance due to the sintering temperature, and improve the quality of the element. And a method of manufacturing the same.

[0017]

The present inventors have made various studies and found that the chemical composition ratio of a spinel-type ferrite sintered body containing oxides of Ni, Cu, Zn, and Fe as main components is determined. _{a (Ni (1-x)} · Cu x) O · b
ZnO · cFe ₂ O ₃ , where a + b + c = 10
0, 0.15 ≦ x ≦ 0.70, 0 ≦ b ≦ 37, 35 ≦ c
≦ 49.5 and, by having 0.1 to 0.3% containing zirconium oxide (ZrO ₂₎ in the ferrite material can be produced ferrite sintered body is no water absorption in 900 ° C. below the sintering temperature, In addition, it has been found that when an inductor is formed by sintering integrally with an Ag conductor, variations in the electrical resistance of the conductor can be reduced.

According to the present invention, in a spinel-type ferrite sintered body containing an oxide of Ni, Cu, Zn or Fe as a main component used for an inductor , the chemical composition ratio is a (Ni _(1-x)・ Cu _x ) O ・ bZnO ・ cF
e ₂ O ₃ (where a + b + c = 100, 0.15 ≦ x
≦ 0.70, 0 ≦ b ≦ 37, 35 ≦ c ≦ 49.5), and zirconium oxide (Zr
Inductor oxide magnetic material, characterized in that O ₂₎ and having containing 0.1 to 0.3 wt% is obtained.

[0019]

According to the present invention, in a method for producing a spinel-type ferrite sintered body mainly containing an oxide of Ni, Cu, Zn, Fe used for an inductor by powder metallurgy, the sintered body is And the chemical composition ratio is a
_{(Ni (1-x) ·} Cu x) O · bZnO · cFe 2 O
₃ (where a + b + c = 100, 0.15 ≦ x ≦ 0.
70, 0 ≦ b ≦ 37, 35 ≦ c ≦ 49.5), and further, zirconium oxide (Z
rO ₂ ) in an amount of 0.1 to 0.3 wt% , and the mixture ratio of particles exceeding 5 μm contained in the molding powder is adjusted to be in a range of 5 vol% or less. Thus, a method for producing an oxide magnetic material for an inductor is obtained.

Here, the following characteristics were set as criteria for setting each range relating to the ferrite material of the present invention.

First, regarding the water absorption, the density d of the sintered body
When the ratio between i and the X-ray density dx of the ferrite material (corresponding to the lattice constant determined by X-ray diffraction and the density determined from the composition of the ferrite element and the number of vacancies to be zero) is 90% or more,
It has been confirmed that the ferrite sintered body becomes non-water absorbing.

As the electrical insulation of the ferrite material, it is desirable that the DC specific resistance ρ _DC is 1 × 10 ⁷ Ω · cm or more.

As the soft magnetic material, it is desirable that the relative magnetic permeability μ be high in order to obtain a high inductance, but the required value differs depending on the frequency band used. Therefore, it is extremely useful condition that μ can take an arbitrary value, so that it is not specified here.

Although the smaller the loss coefficient tan δ of the soft magnetic material is, the better it is, the present invention sets a region where tan δ does not increase remarkably to a useful range. In the present invention, μ and tan δ are evaluated at 100 kHz.

In the present invention, as a molding condition of a green compact for evaluating di / dx, a molding pressure is a general 1 ton.
/ Cm ² .

Here, in the chemical composition ratio of the ferrite material of the present invention, the range of x is set to 0.15 to 0.70 because when x is 0.15 or more, di / dx is 90% or more,
ρ _DC is 10 ⁷ Ω · cm or more, while x is 0.70
Is exceeded, tan δ tends to increase significantly.

The reason why b is set to 0 to 37 in the chemical composition ratio of the ferrite material of the present invention is that b is 37 or less and di / dx is 90% or more, and μ is remarkably improved by increasing b. Because.

Further, in the chemical composition ratio of the ferrite material of the present invention, c is set to 35 to 49.5 because c is 4
When 9.5 or less, di / dx indicates 90% or more, and c is 35.
This is because tan δ tends to significantly increase below.

In the present invention, the content of ZrO ₂ contained in the ferrite material is set to 0.1 to 0.3 wt% because the content of ZrO _{2 of} 0.1 wt% or more is integrated with the ferrite material. Although the variation in the electric resistance of the sintered Ag conductor is reduced, when the content of ZrO ₂ exceeds 0.3 wt %, the sinterability of the ferrite material is reduced, and di / dx is reduced.
This is because it becomes 92 % or less.

In the method for producing an oxide magnetic material of the present invention, the mixing ratio of particles having a size of 5 μm or more in the molding powder is limited to 5 vol% or less.
This is because di / dx becomes 90% or more.

The above characteristic ranges were obtained from samples obtained by sintering at 900 ° C., and the ρ _DC of the ferrite material was 10 ⁷ Ω · cm or more in the setting range of the present invention.

If the molding pressure is increased to increase the molding pressure, di
/ Dx is improved, but in the present invention, it is determined that the general molding conditions are industrially useful, so that the range including the effect of increasing the molding pressure is particularly limited. is not.

[0034]

Embodiments of the present invention will be described below.

Example 1 The chemical composition ratio was 28 (Ni _0.7
.Cu _0.3 ) O.25ZnO.47Fe ₂ O ₃ so that iron oxide (α-Fe ₂ O ₃ ) and nickel oxide (Ni
O), cupric oxide (CuO) and zinc oxide (ZnO) powders as raw materials, and zirconium oxide (Zr
O ₂ ) is 0, 0.1, 0.2, 0.3, 0.
Powder having an average particle size of about 0.2 μm was weighed so as to be 4,0.5 wt%, and was wet-mixed with a stainless steel ball mill for 20 hours.

Next, the raw material mixed powder was calcined at 800 ° C. in the air for 2 hours, and then wet-pulverized in a ball mill for 3 hours to obtain a molding powder. The specific surface area of these powders is B
It was about 3 m ² / g when measured by the ET method.

Next, 3% by weight of PVA was added to these pulverized powders.
After wet mixing, molding pressure 1 ton / cm ² and length 30m
m, a width of 5 mm and a thickness of 1 mm.

Next, a commercially available silver paste (powder particle size: 3 μm or less) was printed on the plate surface of this molded product by silk screen printing at a width of 400 μm and a thickness of 40 μm, and 30 pieces were printed in the width direction of the molded product. did.

Next, the printed surface was covered with another ferrite molded body, kept at 900 ° C. for 2 hours in the air, gradually heated, and cooled in a furnace, and sintered.

Next, the direct current resistance of the silver conductor formed inside these compacts was measured. The result is shown in FIG.

As shown in FIG. 1, the variation of the direct current electrical resistance of the silver conductive by the addition of ZrO ₂ (σ _n-1) is significantly reduced. Also, the average value (bar R) of the DC electric resistance is clearly reduced. Therefore, Ni-Cu-Zn
It can be seen that the inclusion of ZrO ₂ in the system ferrite significantly improves the quality of the inductor.

(Example 2) Using the binder mixed and molded powder obtained in Example 1, a molded body having an outer diameter of about 20 mm, an inner diameter of about 12 mm, and a height of about 8 mm was obtained at a molding pressure of 1 ton / cm ^2. And compression molding using a mold. Next, these compacts were sintered at 900 ° C. for 2 hours in the atmosphere, gradually heated, and cooled in a furnace.

Next, an insulated copper wire having a diameter of 0.26 mm was wound around the sintered body 10 times, and then the relative permeability μ and the loss coefficient tan δ at 100 kHz were measured using an impedance analyzer manufactured by YHP. . The DC specific resistance ρ _DC of the ferrite sintered body was measured using a bridge after grinding the upper and lower bottom surfaces of the sample by about 1 mm. The density ratio di / dx of the sintered body is a value obtained by measuring the density di of the sintered body by the Archimedes method, while calculating dx from the lattice constant obtained by the X-ray diffraction method and the atomic ratio of ferrite (X-ray Density). The result is shown in FIG.

As shown in FIG. 2, the amount of ZrO ₂ added was 0.
The di / dx is 9 2 % or more when the content is 1 wt% or more and 0.3 wt% or less. μ, tan δ, and ρDC do not show values that are problematic as inductance materials. Therefore, the content of ZrO ₂ in the ferrite material is 0.1 wt%.
It is necessary to be at least 0.3 wt% .

Therefore, from Examples 1 and 2, it can be said that ZrO ₂ contained in the ferrite material is industrially useful in the range of 0.1 to 0.3 wt% .

As can be seen from the first and second embodiments, N
A low-temperature sinterable spinel-type ferrite material containing i, Cu, Zn, and Fe oxides as main components contains zirconium oxide (ZrO ₂ ) in an amount of 0 to 0.35 wt% (excluding 0), It is possible to industrially usefully produce a soft magnetic oxide magnetic material having excellent quality by sintering integrally with a silver conductor and capable of being sintered at a low temperature. It is not essential to add zirconium oxide in the form of ZrO ₂ , and even if other zirconium compounds are formed, they are formed with zirconium oxide in the process of calcination or sintering, and the present invention is incorporated into a ferrite material. It is within the scope of the present invention if an amount in the range is contained.

Also, for example, by using zirconium oxide as a medium for mixing and pulverization and selecting conditions, the ZrO ₂ content in ferrite can be adjusted.
Therefore, even this manufacturing method falls within the scope of the present invention.

Example 3 The chemical composition ratio was 28 (Ni _0.7
.Cu _0.3 ) O.25ZnO.47Fe ₂ O ₃ so that iron oxide (α-Fe ₂ O ₃ ) and nickel oxide (Ni
O), cupric oxide (CuO) and zinc oxide (ZnO) as raw materials, and a ball mill using ethanol as a dispersion medium.
Wet mixed for 2 hours. Next, these raw material powders were calcined at 820 ° C. for 4 hours in the air, and then 0.5 mm in a ball mill.
Wet pulverization was performed for up to 5.0 hours to produce eight types of molding powders shown below, and the particle size distribution of the powders was measured with a laser diffraction measuring apparatus. As a result, the mixing ratio of particles having a particle size exceeding 5 μm in these powders was 0, 1.7, 3.1,
4.6, 6.0, 7.4, 8.8, and 10.7 vol%. The specific surface area of these powders measured by the BET method was in the range of 1.6 to 2.7 m ² / g.

Next, 1% by weight of PVA was added to these pulverized powders.
After wet mixing, the outer diameter is about 20 at a molding pressure of 1 ton / cm ^2.
It was compression molded using a mold so as to obtain a molded body having a size of about 12 mm, an inner diameter of about 12 mm and a height of about 8 mm. Next, these compacts were sintered at 900 ° C. for 2 hours in the atmosphere, gradually heated and furnace cooled.

Next, after winding the sintered body with an insulated copper wire having a diameter of 0.26 mm ten times, the relative permeability μ and the loss coefficient tan δ at 100 kHz were measured using an impedance analyzer manufactured by YHP. It was measured. The DC specific resistance ρ _DC of the ferrite sintered body was measured using a bridge after grinding the upper and lower bottom surfaces of the sample by about 1 mm. The density ratio di / dx of the sintered body is a value obtained by measuring the density di of the sintered body by the Archimedes method, and calculating dx from the lattice constant obtained by X-ray diffraction and the atomic ratio of ferrite (X-ray density ). The result is shown in FIG.

FIG. 3 shows that when the mixing ratio of particles having a particle size of 5 μm or more in the powder is 5 vol% or less, di / dx is 90% or more, ρ _DC is 10 ⁷ Ω · cm or more, and tan δ
Is around 10 × 10 ⁻³ and no remarkable change is observed. Therefore, it is understood that the range of 5 vol% or less is useful.

As described in the third embodiment, Ni,
In a sintered spinel-type ferrite containing an oxide of Cu, Zn, or Fe as a main component, low-temperature sintering is performed by setting the mixing ratio of particles exceeding 5 μm in the molding powder to 5 vol% or less. A soft magnetic oxide magnetic material having excellent characteristics can be industrially usefully produced. In addition, the powder is calcined and the compact is sintered in the air. If the product of sintering is spinel ferrite, the method of producing the compacting powder is coprecipitation, spray roasting, etc. Even if is applied, whether the sintering atmosphere is oxidizing or reducing compared to the atmosphere, it is within the scope of the present invention. Also, the mixing and pulverization of the powder is not limited to the ball mill alone, but may be a method of stirring the medium with a disk, a pin or the like. Also, the method for producing the compact is not particularly limited.

[0053] The above in Examples 1, 2 and 3 mentioned chemical composition ratio of _{28 (Ni 0.7 · Cu 0. 3} ) O · 25ZnO
Although only 47 Fe ₂ O ₃ was described, as described above, a (Ni _(1-x) .Cu _x ) O.bZnO.cFe ₂
In O ₃ , a + b + c = 100, and 0.15 ≦ x
This is true if the composition ranges of ≦ 0.70, 0 ≦ b ≦ 37, and 35 ≦ c ≦ 49.5. Examples 1 and 2
In (3) and (3), oxides are used as raw material powders, but are not necessarily limited to these oxides.
Those skilled in the art can easily understand that the present invention is within the scope of the present invention as long as the sintered body constitutes a spinel type ferrite. In addition, any spinel-type ferrite containing Ni, Cu, Zn, and Fe as main components is included in the scope of the present invention as containing other elements.

[0054]

As described above, according to the present invention,
Low-temperature sintering oxide magnet for low-temperature sintering, which has various advantages that low-temperature sintering can improve mechanical strength, reduce the amount of inductance change due to sintering temperature, and improve element quality. Materials and methods for their manufacture can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing the amount of ZrO ₂ added and the DC electric resistance (average value R, standard deviation σ _n-1 ) of an Ag conductor in a ferrite sintered body in Example 1 of the present invention. .

FIG. 2 shows the amount of ZrO ₂ added and the characteristics of a ferrite sintered body (μ, tan δ, ρ _DC , di / d) in Example 2 of the present invention.
It is the figure which showed the relationship of x).

FIG. 3 shows the relationship between the mixture ratio (vol%) of particles exceeding 5 μm in the molding powder and the characteristics of the sintered body (μ, tan δ, ρ _DC , di / dx) in Example 3 of the present invention. FIG.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-130607 (JP, A) JP-A-64-47007 (JP, A) JP-A-59-217624 (JP, A) JP-A-63-1987 158811 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01F 1/12-1/375

Claims (2)

(57) [Claims] 1. Ni, Cu, Z used for an inductor.
In a spinel type ferrite sintered body containing an oxide of n and Fe as a main component, the chemical composition ratio is a (Ni
_{(1-x) · Cu x} ) O · bZnO · cFe 2 O 3 ( where, a + b + c = 100,0.15 ≦ x ≦ 0.70,
0 ≦ b ≦ 37, 35 ≦ c ≦ 49.5), and zirconium oxide (ZrO ₂ ) is further added to the oxide magnetic material .
Inductor characterized in that it comprises 1 to 0.3 wt% free
For oxide magnetic materials. 2. Ni, Cu, Z used for an inductor.
In a method for producing a spinel ferrite sintered body containing an oxide of n and Fe as a main component by a powder metallurgy method, the sintered body has a chemical composition ratio of a (Ni _(1-x) .Cu
_x ) O.bZnO.cFe ₂ O ₃ (where a + b + c
= 100,0.15 ≦ x ≦ 0.70,0 ≦ b ≦ 37,3
The basic component represented by 5 ≦ c ≦ 49.5), further additives
0.1 to 0 zirconium oxide (ZrO ₂₎ as the object.
An oxide for inductors , wherein a powder for molding is mixed so as to contain 3 wt%, and a mixture ratio of particles exceeding 5 μm contained in the powder for molding is adjusted to be in a range of 5 vol% or less. Manufacturing method of magnetic material.