JP3127550B2 - Oxide magnetic material - 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 used for a core for a high frequency low loss chip coil and the like.
More specifically, the present invention relates to a low-loss, low-open-porosity oxide magnetic material suitable for use in a high-frequency band of 100 MHz or more.

[0002]

2. Description of the Related Art A wound type chip coil is an electronic component used for an amplification circuit and an oscillation circuit, and is widely used in fields such as video equipment and communication equipment. In particular, in recent years, with the increase in precision and frequency of electronic circuits used in these devices, 100 MHz
A coil having a high Q in the above high frequency band has been required.

In such a high frequency chip coil, for example, NiMgCu ferrite is used as a magnetic core material.

However, this NiMgCu ferrite is 1
Although a high Q can be obtained in a frequency band of ５０50 MHz, a high Q cannot be obtained in a high frequency band of 100 MHz or more because an eddy current is generated in the grains (crystal grains) of the sintered body. .

[0005] Therefore, the grain growth is suppressed by lowering the firing temperature at the time of producing a magnetic core from 1000 to 1100 ° C., and the grain size (crystal grain size) of the sintered body is reduced.
Has been proposed to reduce the grain size of the sintered body to 1 μm or less, so that
It is possible to obtain Q exceeding 00.

However, when a magnetic core is made of ferrite whose grain size is controlled, the open porosity is large. Therefore, when the electrode is applied to the formed chip coil and baked, the electrode material penetrates and short-circuiting occurs. There is a problem that it occurs.

The present invention has been made to solve the above problems, and has a small crystal grain size after sintering, can suppress loss in a high frequency band, and has a low open porosity of a sintered body. An object is to provide an oxide magnetic material.

[0008]

Means for Solving the Problems To achieve the above object, the oxide magnetic material of the present invention has a composition of 44.5 to 49.0.
and mol% of Fe ₂ O _3, and 3.0～9.0Mol% of MgO,
Zinc borosilicate glass is blended in a proportion such that the content becomes 3.0 to 18.0% by weight with respect to the main component consisting of 1.2 to 4.0 mol% of CuO and the remaining amount of NiO, It is characterized by firing at a predetermined temperature.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be described below in more detail with reference to embodiments.

Example 1 47.5 mol% of Fe ₂ O ₃ , N
46.0 mol% of iO, 4.5 mol% of MgO, CuO
To a ferrite dry powder (main component) containing 2.0 mol%, zinc borosilicate glass is added so as to have a predetermined content as shown in Table 1, and this is made of polyethylene together with cobblestone and distilled water. Put in a pot, mix for 24 hours and dry. Then, the dried raw material is heated at 900 ° C for 2 hours.
The mixture is calcined for a time, put again in a polyethylene pot together with cobblestone and distilled water, mixed and pulverized for 24 hours, then an organic binder is added and mixed for 2 hours, and then the mixture is dried.

Next, the resultant is granulated by a spray-drying method, molded into a predetermined shape (the shape of a core for a chip coil), and fired at a temperature of 1000 to 1150 ° C. to produce a core for a chip coil.

A 0.1 mmφ conducting wire was wound around the chip coil core thus produced five times, and Q at 100 MHz was measured by an impedance analyzer.
Further, the chip coil core was placed in boiling water and boiled for one hour, and the open porosity was measured. Table 1 shows the results.

[0013]

[Table 1]

In Table 1, those marked with an asterisk (*) indicate the content (addition amount) of zinc borosilicate glass, Q at 100 MHz, open porosity, average crystal grain size, etc. of the present invention. It is out of the range (comparative example).

As shown in Table 1, when the calcination temperature is 950 ° C. or lower, the formation of the liquid phase by the zinc borosilicate glass becomes insufficient. Does not drop. In addition, if the firing temperature is 1
At 150 ° C. or higher, the open porosity can be sufficiently reduced, but the ferrite grain growth increases and the average crystal grain size exceeds 2 μm.
Decrease. Therefore, the firing temperature of this material is preferably in the range of 1000 to 1100 ° C. from the viewpoint of keeping the open porosity low and preventing the average crystal grain size from increasing.

When forming a chip coil for a communication device, it is desirable that the inductance Q is 100 or more at 100 MHz and the open porosity is 5% or less.

Next, when examining the content of zinc borosilicate glass, as shown in Table 1, as the content of zinc borosilicate glass increases, the open porosity decreases.
The Q at 100 MHz tends to decrease, and when the content of zinc borosilicate glass decreases, 100 MH
Although the Q in z increases, the open porosity also tends to increase. When the firing temperature is in the range of 1000 to 1100 ° C., the content of zinc borosilicate glass is set to 3 to 18% by weight. Q is 100 or more,
It can be seen that a preferable oxide magnetic material having an open porosity of 5.0% or less and an average crystal grain size of 2 μm or less can be obtained.

Therefore, the data shown in Table 1 and Table 1
According to the overall evaluation based on other data not specifically shown, the content of the zinc borosilicate glass is 3% by weight to 1%.
It is preferably in the range of 8% by weight.

Example 2 A ferrite dry powder prepared by blending the respective component materials so that the final composition has the ratio shown in Table 2 is prepared.

[0020]

[Table 2]

These ferrite dry powders are made of Fe ₂ O ₃
And the ratio of MgO was changed to 1.0mo without changing the ratio of CuO.
The percentage was changed by 1%, and the balance was NiO. In Table 2, a sample number with an asterisk indicates a comparative example outside the scope of the present invention.

To each ferrite dry powder (main component) thus prepared, zinc borosilicate glass was added at a ratio such that the content became 5.0% by weight. Put in a pot, mix for 24 hours and dry. Then, this dried raw material is 900
The mixture is calcined at a temperature of 2 ° C. for 2 hours, put again in a polyethylene pot together with cobblestone and distilled water, mixed and ground for 24 hours, added with an organic binder, mixed for 2 hours, and then dried. Next, this is granulated by a spray drying method, then molded into a predetermined shape (shape of a chip coil core), and fired at a temperature of 1050 ° C. to form a chip coil core.

A 0.1 mmφ conducting wire was wound around the chip coil core thus formed five times, and Q at 100 MHz was measured by an impedance analyzer.
The result is shown in FIG.

Further, the chip coil core was placed in boiling water and boiled for one hour, and the open porosity was measured. The result is shown in FIG.

As shown in FIG. 1, as the MgO content increases, the Q at 100 MHz tends to increase.
When the O content is less than 3.0 mol%, the effect of increasing Q becomes insufficient, and the Q at 100 MHz becomes less than 100.

As shown in FIG. 2, as the content of MgO increases, the open porosity tends to increase.
When the content of gO exceeds 9.0 mol%, the open porosity becomes 5.
More than 0%.

Therefore, the content of MgO is 3.0 to
It is preferably in the range of 9.0 mol%.

Example 3 A dry ferrite powder prepared by blending the respective component materials so that the final composition has the ratio shown in Table 3 is prepared.

[0029]

[Table 3]

These ferrite dry powders are made of Fe ₂ O ₃
Without changing the ratio of MgO and the ratio of CuO
The percentage was changed by 1%, and the balance was NiO.

In Table 3, a sample number with an asterisk indicates a comparative example outside the scope of the present invention.

To each ferrite dry powder (main component) thus prepared, zinc borosilicate glass was added at a ratio such that the content became 5.0% by weight. Put in a pot, mix for 24 hours and dry. Then, this dried raw material is 900
The mixture is calcined at a temperature of 2 ° C. for 2 hours, put again in a polyethylene pot together with cobblestone and distilled water, mixed and ground for 24 hours, added with an organic binder, mixed for 2 hours, and then dried. Next, this is granulated by a spray drying method, then molded into a predetermined shape (shape of a chip coil core), and fired at a temperature of 1050 ° C. to form a chip coil core.

A 0.1 mmφ conducting wire was wound five times around the chip coil core thus prepared, and Q at 100 MHz was measured by an impedance analyzer.
The result is shown in FIG.

The chip coil core was placed in boiling water and boiled for one hour, and the open porosity was measured. FIG. 4 shows the results.

As shown in FIG. 3, as the CuO content increases, the Q at 100 MHz tends to decrease,
If the content exceeds 4.0 mol%, the decrease in Q becomes remarkable, and the Q at 100 MHz becomes less than 100.

As shown in FIG. 4, as the CuO content increases, the open porosity tends to decrease.
Is less than 1.2 mol%, the open porosity is 5.0.
%.

Therefore, the content of CuO is from 1.2 to
It is preferably in the range of 4.0 mol%.

Example 4 A ferrite dry powder prepared by blending the respective component materials so that the final composition has the ratio shown in Table 4 is prepared.

[0039]

[Table 4]

These dry ferrite powders have a ratio of Fe ₂ O ₃ of 1.0 mol without changing the ratio of MgO and CuO.
The percentage was changed by 1%, and the balance was NiO.

In Table 4, a sample number with an asterisk indicates a comparative example outside the scope of the present invention.

To each of the ferrite dry powders (main components) thus prepared, zinc borosilicate glass was added at a ratio such that the content became 5.0% by weight, and this was made of polyethylene with cobblestone and distilled water. Put in a pot, mix for 24 hours and dry. Then, this dried raw material is 900
The mixture is calcined at a temperature of 2 ° C. for 2 hours, put again in a polyethylene pot together with cobblestone and distilled water, mixed and ground for 24 hours, added with an organic binder, mixed for 2 hours, and then dried. Next, this is granulated by a spray drying method, then molded into a predetermined shape (shape of a chip coil core), and fired at a temperature of 1050 ° C. to form a chip coil core.

A wire having a diameter of 0.1 mm was wound around the chip coil core thus formed five times, and Q at 100 MHz was measured by an impedance analyzer.
The result is shown in FIG.

Further, the chip coil core was placed in boiling water and boiled for one hour, and the open porosity was measured. FIG. 6 shows the result.

As shown in FIG. 5, when the content of Fe ₂ O ₃ increases, Q at 100 MHz tends to decrease.
_When the content of ₂ O ₃ exceeds 49.0 mol%, the Q is remarkably reduced, and the Q at 100 MHz becomes less than 100.

As shown in FIG. 6, as the content of Fe ₂ O ₃ increases, the open porosity tends to decrease.
When the content of e ₂ O ₃ is less than 44.5 mol%, the open porosity exceeds 5.0%.

Therefore, the content of CuO is 44.5.
It is preferably in the range of 〜49.0 mol%.

[0048]

As described above, the oxide magnetic material of the present invention contains 44.5 to 49.0 mol% of Fe ₂ O ₃ and 3.0 to 49.0 mol%.
~ 9.0 mol% MgO and 1.2 ~ 4.0 mol% Cu
With respect to the main component consisting of O and the remaining amount of NiO, 3.0 to 3.0
Since 18.0% by weight of zinc borosilicate glass is added and fired at a predetermined temperature, the crystal grain size after sintering is small, and loss in a high frequency band can be suppressed, and It is possible to obtain an oxide magnetic material having a low open porosity of a sintered body, and by using this as a core material for a high-frequency chip coil, a Q in a high-frequency band is large, and a short-circuit failure due to penetration of an electrode material. It is possible to manufacture a high-frequency low-loss chip coil that does not cause the problem.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the MgO content and Q at 100 MHz.

FIG. 2 is a graph showing the relationship between the MgO content and the open porosity.

FIG. 3 is a diagram showing the relationship between the CuO content and Q at 100 MHz.

FIG. 4 is a diagram showing a relationship between a CuO content and an open porosity.

FIG. 5 is a diagram showing the relationship between the content of Fe ₂ O ₃ and Q at 100 MHz.

FIG. 6 is a graph showing the relationship between the content of Fe ₂ O ₃ and the open porosity.

Claims (2)

(57) [Claims] 1. 44.5 to 49.0 mol% of Fe ₂ O
₃ , 3.0 to 9.0 mol% of MgO, and 1.2 to 4.0
Zinc borosilicate glass was blended at a ratio of 3.0 to 18.0% by weight with respect to the main component consisting of mol% of CuO and the remaining amount of NiO, and fired at a predetermined temperature. An oxide magnetic material, comprising: 2. The oxide magnetic material according to claim 1, wherein the average crystal grain size after firing is 2.0 μm or less, and the open porosity is 5% or less.