JP5048219B2 - Ferrite sintered body, manufacturing method thereof and coil component - Google Patents

Description

  The present invention relates to a ferrite sintered body, a manufacturing method thereof, and a coil component.

  Ferrite cores composed of sintered ferrite are mainly used for coil parts, sensors, antennas, deflection yokes and other parts, and electrical products incorporating these parts have been mainly used indoors until now. It was.

However, due to the rapid spread of electric products such as mobile phones and notebook computers, and the expansion of applications as automotive parts in recent years, products with built-in coil parts will be used outdoors. It has become to. Naturally, the coil components employed in these outdoor products are required to have characteristics that can withstand harsh usage environments, particularly temperature changes. As a characteristic specifically required for the coil component used in such an environment and application, there is a small change in inductance in an operating temperature range, and preferably no change at all. In order to meet this requirement, it is necessary to make the relative temperature coefficient α μ _ir of the initial permeability μ _i of the ferrite core as small as possible.

Conventionally, as a ferrite core having such characteristics, Ni—Cu—Zn-based ferrite is mainly used, and 0.2 to 0.8 wt% of Nb ₂ O ₅ , 0.3 to 1.2 wt. %
There is known a sintered body of an oxide magnetic material to which any one of Ta ₂ O ₅ , 0.15 to 1.35 wt% MoO ₃ is added (see, for example, Patent Document 1 below). According to Patent Document 1, by setting the composition of the oxide magnetic material in the sintered body as described above, the temperature coefficient of initial permeability in the temperature range of −25 to 85 ° C. is 0.5 to 2.9 ppm / ° C. A ferrite sintered body having a value of is realized.
Japanese Patent Laid-Open No. 5-3112

  By the way, in recent years, coil components used in automobile electrical products such as tire pressure sensors and engine room control circuits have a higher initial permeability temperature characteristic than coil components used in other applications. There are more demanding requirements.

However, the ferrite sintered body disclosed in Patent Document 1 mentioned above, although low Arufamyu _ir can be realized in a temperature range of -25 to 85 ° C., it is possible to achieve a low Arufamyu _ir in a region particularly outside the above temperature range It tends to be impossible. As a result, the coil component may not operate properly in a region outside the temperature range. For example, the usable frequency band may change due to a change in environmental temperature, and the device may not operate properly. Therefore, the use of the coil component is limited, and there is a problem that the versatility is inferior.

  The present invention has been made in view of the above circumstances, and is capable of properly operating a coil component over a wide temperature range of −40 to 120 ° C. and can be used for a wide range of applications, and a method for manufacturing the same. And it aims at providing a coil component.

In order to solve the above-mentioned problems, the present invention contains 46.0 to 50.0 mol% Fe ₂ O ₃ , 20.0 to 35.0 mol% ZnO, 5.9 to 9.0 mol% CuO, _The balance excluding ₂ O ₃ , ZnO and CuO is NiO , and the sum of mol% of Fe ₂ O ₃ , ZnO, CuO and NiO, each of which may contain inevitable impurities, is 100, and ZnO / Fe ₂ the molar ratio of _Fe 2 _{O 3} and ZnO, represented by O ₃ is 0.54 to 0.67, the temperature range of relative temperature coefficient αμ _ir of initial permeability μi at a frequency of 100kHz is -40 to 120 ° C. The ferrite sintered body is characterized in that it is -2 to 2 ppm / ° C.

According to this ferrite sintered body, since the relative temperature coefficient αμ _ir of the initial magnetic permeability μi is −2 to 2 ppm / ° C. in the temperature range of −40 to 120 ° C., the coil is spread over a wide temperature range of −40 to 120 ° C. Parts can be operated properly. For this reason, the ferrite sintered body of the present invention can be used as a core of a coil component for automobiles, such as a tire air pressure sensor and a control circuit in an engine room, or as a coil component other than those for automobiles. Can be used.

The present invention, 46.0~50.0mol% of _Fe 2 _{O 3, 20.0~35.0mol%} of ZnO, the CuO containing _{5.9~9.0mol%, Fe 2 O 3,} ZnO and The balance excluding CuO is NiO , and the sum of mol% of Fe ₂ O ₃ , ZnO, CuO, and NiO, each of which may contain inevitable impurities, is 100, and is represented by ZnO / Fe ₂ O ₃ A calcining step of calcining a raw material mixture having a molar ratio of Fe ₂ O ₃ and ZnO of 0.54 to 0.67 to obtain a calcined product, and crushing the calcined product to obtain a pulverized powder And a main firing step of obtaining a ferrite sintered body by subjecting the pulverized powder to main firing, and in the pulverizing step, the D90 in the particle size distribution for the primary particle size of the pulverized powder is 5 μm or less. Crush the pre-baked product , In the main baking step, the average crystal grain size D50 in the ferrite sintered body is a method for producing a ferrite sintered body of firing the pulverized powder such that 5 to 15 [mu] m.

According to this method for producing a ferrite sintered body, it is possible to effectively produce a ferrite sintered body having a relative temperature coefficient αμ _ir of initial permeability μi of −2 to 2 ppm / ° C. in a temperature range of −40 to 120 ° C. Can do. Moreover, the ferrite sintered compact obtained by this manufacturing method can operate a coil component appropriately over the wide temperature range of -40-120 degreeC. For this reason, the ferrite sintered body of the present invention can be used as a core of a coil part for automobiles and a coil part other than for automobiles, such as a tire pressure sensor and a control circuit in an engine room, and is widely used. Can be used for applications.

  Furthermore, this invention is a coil component provided with the ferrite sintered compact mentioned above.

According to this coil component, since the relative temperature coefficient αμ _ir of the initial permeability μi in the temperature range of −40 to 120 ° C. in the ferrite sintered body is −2 to 2 ppm / ° C., a wide temperature of −40 to 120 ° C. It is possible to operate properly over a range. Therefore, the coil component of the present invention can be used as a coil component for automobiles or a coil component other than for automobiles, such as a tire pressure sensor and a control circuit in an engine room, and can be used for a wide range of applications.

  In the present invention, the “primary particle diameter of the pulverized powder” refers to the particle diameter per one pulverized powder, and the particle diameter of the aggregated particles obtained by agglomerating the pulverized powder, that is, secondary particles of the pulverized powder Does not include diameter.

  In the present invention, “D90 in the particle size distribution of the primary particle size of the pulverized powder” means that the pulverized powder is observed with a visual field of 46 μm × 35 μm (magnification: 5500 times) using a scanning electron microscope (SEM). The value calculated by analyzing the observed SEM image by Asahi Kasei image analysis apparatus IP-1000 shall be said.

  Furthermore, in the present invention, the “average grain size D50 of the sintered ferrite body” means that the cross section of the sintered ferrite body is observed with a visual field of 85 μm × 64 μm (magnification: 1500 times) using SEM. The value calculated by analyzing the SEM image with the image analysis apparatus IP-1000 manufactured by Asahi Kasei shall be said.

  According to the ferrite sintered body, the manufacturing method thereof, and the coil component of the present invention, the coil component can be properly operated over a wide temperature range of −40 to 120 ° C. and can be used for a wide range of applications.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.

  FIG. 1 is a perspective view showing an embodiment of a coil component of the present invention. As shown in FIG. 1, the coil component 10 includes a drum-type ferrite core (sintered body core) 12 and a copper wire (winding) 14 with an insulation coating wound around the ferrite core 12. .

Ferrite core 12 is composed of a ferrite sintered body, ferrite sintered body, _Fe 2 _{O 3} the 46.0~50.0mol%, ZnO of 20.0～35.0Mol%, a CuO 5.9-9 and contains _.0mol%, the balance excluding Fe ₂ O 3, ZnO, and CuO is Ru NiO der. The molar ratio of Fe ₂ O ₃ and ZnO represented by ZnO / Fe ₂ O ₃ is 0.54 to 0.67, and the relative temperature coefficient αμ _ir of the initial permeability μi at a frequency of 100 kHz is It is −2 to 2 ppm / ° C. in the temperature range of −40 to 120 ° C.

According to this coil component 10, since the relative temperature coefficient αμ _ir of the initial permeability μi in the temperature range of −40 to 120 ° C. in the ferrite core 12 is −2 to 2 ppm / ° C., a wide temperature of −40 to 120 ° C. It is possible to operate properly over a range. For this reason, the coil component 10 can be used as an automotive coil component or a coil component other than an automotive component, such as a tire pressure sensor or a control circuit in an engine room, and can be used for a wide range of applications.

  The reason why the ferrite sintered body has the above composition is as follows.

That is, if the content of Fe ₂ O ₃ in the ferrite sintered body is less than 46.0 mol%, the sintered body density is lowered, and as a result, the mechanical strength and the magnetic properties are deteriorated. The coil component 10 cannot be properly operated over a wide temperature range of 120 ° C. For this reason, the use of the coil component 10 is limited, and the coil component is inferior in versatility. On the other hand, when the content ratio of Fe ₂ O ₃ in the ferrite sintered body exceeds 50.0 mol%, Fe ₃ O ₄ is remarkably precipitated and the sintered body density is lowered, so that the mechanical strength of the ferrite core 12 is reduced. descend. Further, if the content of Fe ₂ O ₃ in the ferrite sintered body exceeds 50.0 mol%, the specific resistance as a core is remarkably lowered, and the eddy current is generated and the proper operation is not performed in a high frequency region.

  Further, when the content of CuO in the ferrite sintered body is less than 1.0 mol%, the sintered body density is lowered, so that the mechanical strength of the ferrite core 12 is lowered. On the other hand, when it exceeds 9.0 mol%, the specific resistance of the core is lowered, and the eddy current is generated, so that the core does not operate properly in the high frequency region.

  On the other hand, if the ZnO content is less than 20.0 mol%, the initial permeability decreases. On the other hand, when the ZnO content exceeds 35.0 mol%, the Curie temperature is lowered, and demagnetization occurs due to the influence of the temperature.

In the ferrite sintered body, the balance excluding Fe ₂ O ₃ , ZnO, and CuO contains NiO. This is because if the ferrite sintered body does not contain NiO, the specific resistance of the core is lowered, and the generation of eddy currents prevents proper operation in the high frequency region.

Furthermore, when the molar ratio of Fe ₂ O ₃ represented by ZnO / Fe ₂ O ₃ and ZnO is less than 0.54, αμir increases in the positive direction, and when the molar ratio exceeds 0.67, 20 to 20 Αμir at 120 ° C. increases in the negative direction.

Furthermore, when the relative temperature coefficient αμ _ir of the initial permeability μi is out of the range of −2 to 2 ppm / ° C. in the temperature range of −40 to 120 ° C. in the ferrite sintered body, the coil is spread over the temperature range of −40 to 120 ° C. The component 10 may not operate properly, resulting in poor versatility.

In the ferrite sintered body, the content of Fe ₂ O ₃ is preferably 46.5 to 49.5 mol%, and the content of ZnO is preferably 24.0 to 33.0 mol%.

  In the ferrite sintered body, the average crystal grain size D50 is preferably 5 to 15 μm. When the average crystal grain size D50 is less than 5 μm, αμir tends to increase in the negative direction as compared with the case where the average crystal grain size D50 is 5 μm or more. On the other hand, when the average crystal grain size D50 exceeds 15 μm, αμir tends to increase in the positive direction as compared with the case where it is 15 μm or less.

Further, the remainder excluding Fe ₂ O ₃ , ZnO, and CuO may contain inevitable impurities in addition to NiO.

  Next, the manufacturing method of the coil component 10 mentioned above is demonstrated.

  First, a method for manufacturing the ferrite core 12 constituting the coil component 10 will be described.

First, iron oxide α-Fe ₂ O ₃ , copper oxide CuO, zinc oxide ZnO, and nickel oxide NiO are prepared, and these oxides are mixed to obtain a raw material mixture. At this time, the contents of Fe ₂ O ₃ , ZnO, and CuO were 46.0 to 50.0 mol%, 20.0 to 35.0 mol%, and 5.9 to 9.0 mol%, respectively, and ZnO / Fe ₂ O ₃ molar ratio of in _Fe 2 _{O 3} and ZnO represented raw material were mixed so as to have a 0.54 to 0.67, to form the balance in N iO. The sum of mol% of Fe ₂ O ₃ , ZnO, CuO, and NiO, each of which may contain inevitable impurities, is 100. Each raw material is mixed so that it may become the said composition ratio as a final composition. Mo is an inevitable impurity.

  Next, the raw material mixture is calcined to obtain a calcined product (calcining step). The calcination is usually performed in the air. The calcining temperature depends on the components constituting the raw material mixture, but is preferably 800 to 1100 ° C. Moreover, although calcining time is dependent on the component which comprises a raw material mixture, it is preferable to set it as 1-3 hours.

  Next, the obtained calcined product is pulverized by a ball mill or the like to obtain a pulverized powder (pulverization step). At this time, the calcined product is pulverized so that D90 in the particle size distribution with respect to the primary particle size of the pulverized powder is 5 μm or less. In order to do so, specifically, the raw material mixture may be mixed and pulverized for 10 to 40 hours using a pulverizer such as a ball mill.

  Subsequently, the pulverized powder obtained as described above and a suitable binder such as polyvinyl alcohol are mixed and molded into the same shape as the ferrite core 12, that is, a drum shape to obtain a molded body.

  Next, the molded body is fired (main firing step). Thus, a ferrite core 12 made of a ferrite sintered body is obtained. At this time, the pulverized powder is sintered so that the average crystal grain size D50 in the ferrite core 12 is 5 to 15 μm. When D50 is less than 5 μm, αμir increases in the negative direction. On the other hand, when the average crystal grain size D50 exceeds 15 μm, αμir increases in the positive direction.

  The molded body may be fired in the air. The firing temperature depends on the raw materials constituting the pulverized powder, but is preferably 900 to 1300 ° C. Moreover, although baking time is dependent on the raw material which comprises pulverized powder, it is preferable to set it as 2 to 5 hours.

  Finally, a copper wire (winding) 14 with an insulation coating is wound around the ferrite core 12 obtained as described above. Thus, the manufacture of the coil component 10 is completed.

When the coil component 10 is manufactured as described above, the ferrite having the relative temperature coefficient αμ _ir of the initial permeability μi is −2 to 2 ppm / ° C. in the temperature range of −40 to 120 ° C. by the manufacturing method of the ferrite core 12. A sintered body can be produced effectively. Moreover, the ferrite sintered compact obtained by the said manufacturing method can operate the coil component 10 appropriately over the wide temperature range of -40-120 degreeC. For this reason, the obtained coil component 10 can be used as a coil component other than for automobiles, such as a tire pressure sensor and a control circuit in an engine room, and can be used for a wide range of applications.

Why should be noted that for defining the method for producing the ferrite sintered body, Fe ₂ O ₃ molar ratio of ZnO, the D50 average crystal grain size of D90 and a ferrite sintered body in the particle size distribution for the primary particle diameter of the pulverized powder To state.

The temperature characteristics of the initial permeability μ _i are affected by the composition, the Curie temperature determined by the composition, the stress balance between the crystal grains and the grain boundaries, and the magnetic anisotropy. Therefore, first, by defining the molar ratio of Fe ₂ O ₃ and ZnO represented by ZnO / Fe ₂ O ₃ , the influence of the composition and the Curie temperature is controlled.

And the sintered compact with the desired average crystal grain diameter D50 is obtained by baking the molded object which consists of the pulverized powder which does not contain the coarse particle which prescribed | regulated D90 on suitable baking conditions. The microstructure of the sintered body thus obtained has no coarse crystal grains, and the sintered body becomes a uniform polycrystalline body having a uniform crystal grain diameter. As a result, the size of the crystal grains in the sintered body is increased. The variation in shape magnetic anisotropy resulting from the unevenness of the shape (particle diameter) and the shape is reduced, and the variation in the stress balance between the crystal grains and the grain boundaries is also reduced. At this time, by controlling the average crystal grain size D50 to an arbitrary size according to the firing conditions, the stress balance between the crystal grains and the grain boundaries when viewed as the entire sintered body can be controlled. This is because if the average crystal grain size D50 is small, the ratio of the grain boundary per unit volume increases, and conversely, if D50 is large, the ratio of the grain boundary decreases. Thus, the temperature characteristics of the initial permeability μ _i are good. For the above reasons, in the method for producing a ferrite sintered body, the molar ratio of Fe ₂ O ₃ and ZnO, D90 in the particle size distribution for the primary particle diameter of the pulverized powder, and D50 of the average crystal particle diameter of the ferrite sintered body are defined. Has been.

  The present invention is not limited to the above embodiment. For example, in the manufacturing method of the ferrite core 12, in order to make the ferrite core 12 into a predetermined shape, a mixture of pulverized powder and binder is formed into a drum shape before the main firing, but the ferrite core 12 has a predetermined shape. For this purpose, the pulverized powder may be formed into a drum shape by subjecting it to main firing and then processing.

  Moreover, in the said embodiment, although the coil component 10 is comprised by the ferrite core 12 and the copper wire 14 with an insulation coating, you may provide the resin mold which surrounds the ferrite core 12 and the copper wire 14 with an insulation coating further. .

(Examples 1-7 , Reference Example 8 and Comparative Examples 1-8)
Each component raw material was weighed so as to have the composition shown in Table 1, and mixed for 5 hours by a ball mill. The raw material mixture thus obtained was calcined in air at the calcining temperature shown in Table 2 for 2 hours, and then mixed and pulverized for a predetermined time in a ball mill.

After drying the pulverized powder thus obtained and adding 1.0 part by mass of polyvinyl alcohol to 100 parts by mass of the pulverized powder, the resulting mixture was pressure-molded at a pressure of 100 kPa, and the dimensions were an outer diameter of 20 mm, A toroidal molded body having an inner diameter of 10 mm and a height of 5 mm was obtained. These molded bodies were fired in air at the firing temperature shown in Table 2 for 2 hours to obtain toroidal core samples (ferrite cores) of Examples 1 to 7, Reference Example 8 and Comparative Examples 1 to 8.

After winding the wire of φ0.35 mm 20 times on each of the toroidal core samples of Examples 1 to 7, Reference Example 8 and Comparative Examples 1 to 8, the inductance value was measured by a Precision LCR meter 4284A manufactured by Hewlett-Packard Company, The initial permeability μi at 100 kHz and 0.4 A / m was determined. The results are shown in Table 1.

により求めた。ただし、上記式中、Ｔ_１，Ｔ_２はそれぞれ測定の行われた温度を表し、μi_１，μi_２はそれぞれ温度Ｔ_１，Ｔ_２における初透磁率を表す。結果を表１に示す。また初透磁率の相対温度係数αμ_ｉｒは、−４０〜２０℃の範囲と、２０℃〜１２０℃の範囲とで符号が逆転し、Ｔ１＝−４０℃、Ｔ２＝１２０℃であるとして初透磁率の相対温度係数αμ_ｉｒを算出すると小さい値として算出される場合がある。この場合に算出される相対温度係数αμ_ｉｒは初透磁率の温度特性を的確に表しているとは言い難い。そこで、表１においては、温度範囲を−４０〜２０℃の範囲と、２０℃〜１２０℃の範囲の２つに分け、各温度範囲において初透磁率の相対温度係数αμ_ｉｒを算出してある。 Further, with respect to the toroidal core sample used for the measurement of μi, the inductance value is further measured in the range of −40 to 120 ° C., and the relative temperature coefficient αμ _ir of the initial permeability in this temperature range is expressed by the following formula:

Determined by However, in the above formula, T ₁ and T ₂ represent the temperatures at which the measurements were made, and μ i ₁ and μ i ₂ represent the initial magnetic permeability at the temperatures T ₁ and T ₂ , respectively. The results are shown in Table 1. In addition, the relative temperature coefficient αμ _ir of the initial permeability reverses the sign between the range of −40 to 20 ° C. and the range of 20 ° C. to 120 ° C., and T1 = −40 ° C. and T2 = 120 ° C. When the relative temperature coefficient αμ _ir of the magnetic susceptibility is calculated, it may be calculated as a small value. It is difficult to say that the relative temperature coefficient αμ _ir calculated in this case accurately represents the temperature characteristic of the initial permeability. Therefore, in Table 1, the temperature range is divided into a range of −40 to 20 ° C. and a range of 20 to 120 ° C., and the relative temperature coefficient αμ _ir of the initial permeability is calculated in each temperature range. .

Furthermore, about the pulverized powder obtained in the process of manufacturing the toroidal core samples of Examples 1 to 7, Reference Example 8 and Comparative Examples 1 to 8, the field of view was observed with a visual field of 46 μm × 35 μm (magnification: 5500 times). The SEM image observed at this time was analyzed by Asahi Kasei image analyzer IP-1000 to calculate D90 in the particle size distribution for the primary particle size of the pulverized powder. The results are shown in Table 2.

Further, the toroidal core samples of Examples 1 to 7, Reference Example 8 and Comparative Examples 1 to 8 were observed using a SEM with a visual field of 85 μm × 64 μm (magnification: 1500 times), and SEM images observed at this time were manufactured by Asahi Kasei. The average crystal grain size D50 was calculated by analyzing with an image analyzer IP-1000. The results are shown in Table 2.

  Furthermore, the density of the sintered body was calculated from the outer diameter, inner diameter, height dimension and weight of the toroidal core ampoule. The results are shown in Table 2.

  Further, for the trochoidal core samples according to Examples 1, 2, 4, and 5 and Comparative Examples 1, 3, and 4, the relationship between the initial permeability μi and the temperature was examined. The results are shown in FIG.

As is clear from the results shown in Table 1, the toroidal core samples according to Examples 1 to 7 have a relative temperature of initial permeability μi in any of the temperature range of −40 to 20 ° C. and the temperature range of 20 to 120 ° C. The coefficient α μ _ir is in the range of −2 to 2 ppm / ° C., and the toroidal core sample that is a coil component can be properly operated over a wide temperature range of −40 to 120 ° C. and can be used for a wide range of applications. It was.

On the other hand, in the toroidal core samples according to Comparative Examples 1 to 8, the relative temperature coefficient αμ _ir of the initial permeability μi is outside the range of −2 to 2 ppm / ° C. in the temperature range of −40 to 20 ° C. It has been found that the toroidal core sample as a component cannot be properly operated over a wide temperature range of −40 to 120 ° C. and cannot be used for a wide range of applications.

  From the above, according to the ferrite sintered body of the present invention, it was confirmed that the coil component can be properly operated over a wide temperature range of −40 to 120 ° C. and can be used for a wide range of applications.

It is a perspective view which shows one Embodiment of the coil components of this invention. It is a graph which shows the relationship between the initial permeability (micro | micron | mu) i and temperature about the trochoidal core sample which concerns on Example 1,2,4,5 and Comparative Example 1,3,4.

Explanation of symbols

  10 ... Coil parts, 12 ... Ferrite core, 14 ... Winding.

Claims (3)

Fe ₂ O ₃ 46.0 to 50.0 mol%, ZnO 20.0 to 35.0 mol%, CuO 5.9 to 9.0 mol%, and the remainder excluding Fe ₂ O ₃ , ZnO and CuO is NiO, _Fe 2 _O 3, ZnO, each may include inevitable impurities, CuO, and the respective mol% of the sum of NiO 100, and _Fe 2 _{O 3} expressed by ZnO / _Fe 2 _{O 3} A calcining step of calcining a raw material mixture having a molar ratio with ZnO of 0.54 to 0.67 to obtain a calcined product;
A pulverizing step of pulverizing the calcined product to obtain a pulverized powder;
A main firing step of obtaining a ferrite sintered body by subjecting the pulverized powder to main firing,
In the pulverization step, the calcined product is pulverized so that D90 in the particle size distribution for the primary particle size of the pulverized powder is 5 μm or less,
In the main firing step, the pulverized powder is fired so that the average crystal grain size D50 in the ferrite sintered body is 5 to 15 μm.
Manufacturing method of ferrite sintered body. A ferrite sintered body obtained by the method for producing a ferrite sintered body according to claim 1,
The relative temperature coefficient αμ _ir of the initial permeability μi at a frequency of 100 kHz is −2 to 2 ppm / ° C. over a temperature range of −40 to 120 ° C.,
A ferrite sintered body characterized by that.   A coil component comprising the ferrite sintered body according to claim 2.

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